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Flashcards in Exam 1 Terminology Deck (285):
1

Virology

The study of viruses and viral diseases

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Virologist

Someone who studies viruses

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Virion

A complete virus particles that consists of an RNA or DNA core with a protein coat sometimes with external envelopes and that is the extracellular infective form of a virus.

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Virus

Is a broad general terminology that is used to describe any aspect of the infectious agent and includes: the infectious (virion) or inactivated virus particles, or viral nucleic acid and protein in the infected cell.

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Viroid

An infectious particle smaller than any of the known viruses, an agent of certain plant diseases. The particle consists only of an extremely small circular RNA (ribonucleic acid) molecule, lacking the protein coat of a virus.

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Smallest viruses

Porcine circovirus type 1 (17 nm diameter)
Parvoviruses (18 nm diameter)

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Largest viruses

Pandoravirus (400 nm diameter)
Poxvirus (200 nm) diameter and 300 nm in length)

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Pleomorphism

The ability of some virus to alter their shape or size

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Electron Microscopy (EM)

Requires negative staining with electron dense material. Resolution range is usually 50-75 angstroms.

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Cryo-electrom Microscopy (Cryo-EM)

Allows the observation of biological specimens in their native environment (not stained or fixed in any way) at cryogenic temperatures in EM.

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X-ray Crystallographic Method

The virus is crystallized. Then you bombarded the virus crystal with x-rays. The x-rays will strike and be reflected. Can measure angle of reflection and intensity of reflection. Fit into the computer and with software can reconstruct the virus structure.

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Capsid

A protein (coat) shell of a virus that encases/envelopes the viral nucleic acid or genome

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Capsomeres

Make up a capsid by non-covalent bonds. It is the basic subunit protein in the capsid of a virus.

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Nucleocapsid

Capsid + virus nucleic acid

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Triangulation number (T-number)

Described the relation between the number of pentagons and hexagons of the icosahedron. The larger the T-number the more hexagons are present relative to the pentagons.

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T-number formula

T = (h^2 + h * k + k^2)

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Glycoprotein

Spike embedded on the envelope. Anchored in the lipid bilayer by means of hydrophobic bonds. Transmembrane proteins.

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Matrix protein

Between the lipid envelope and the capsid. These proteins link the internal nucleocapsid to the lipid membrane envelope.

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External glycoprotein

Anchored in the envelope by a single transmembrane domain, and a short internal tail. Usually major antigens.

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Hemagglutinin (HA)

Binding, fusion, antigenic, hemagglutination, clumping RBC

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Neuraminidase (NP)

Release progeny virus from host cell, antigenic

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Channel proteins

Which are most hydrophobic proteins that form a protein lined channel through the envelope. Alters permeability of the membrane.

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Fusion proteins

Fuse to host cytoplasmic membrane. Facilitates virus into the host cell. Host cytoplasmic membrane and virus envelope is fused. Needed to penetrate into the host cell.

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Positive sense RNA genome

It is similar to mRNA and thus can be immediately translated by the host cell and can directly synthesize viral proteins.

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Negative sense RNA genome

Is complementary to mRNA and must be converted to positive sense RNA by an RNS polymerase before translation.

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Antigenic Drift

Caused by point mutations. Mutation is a change of nucleotide of the genome. There is a change of antigenicity of the virus as a result of point mutation.

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Antigenic Shift - Recombination

Intramolecular recombination involves the exchange of nucleotide sequences between different nucleotides. Usually by closely related, viruses during replication.

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Antigenic Shift - Reassortment

Is the most important mechanism for high genetic diversity in viruses with segmented genome.

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Lysins

Hydrolytic enzymes produced by bacteriophages to cleave the host's cell wall

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Retroviral integrase (IN)

Enzyme produced by a retrovirus (such as HIV) that enables its genetic material to be integrated into the DNA of the infected cells

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Reverse Transcriptase (RT)

Enzyme used to generate complementary DNA (cDNA) from a RNA template

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Nucleic acid polymerase

viral genome replication

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Neuraminidases

Enzymes that cleave glycosidic bonds. Allows release of viruses from host cell.

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Incomplete virions

Virion without nucleic acid (empty capsid)

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Defective virions

a virus that cannot replicate because it lacks a full complement/copy of viral genes.

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Defective Interfering Particle (DIP)

When the defective viruses cannot replicate, but can interfere other congeneric mature virion entering the cells, we call them defective interfering particles (DIP)

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Pseudovirion

Contains non-viral genome within the viral capsid, such as host nucleic acid instead of viral nucleic acid. Look like ordinary viral particles under EM, but do not replicate.

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Pseudotypes

When related viruses infect the same cell, the genome of one virus may be enclosed in the heterologous capsid of the second virus.

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The Baltimore Classification System

Is a classification system based on viral genome. Viruses are classified into one of the seven groups depending on combination of their nucleic acid (DNA or RNA), strandness, sense, and method replication.

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The International Committee Taxonomy of Viruses (ICTV) Classification System

The ICTV is the only body charged by the international union of microbiological societies with the task of developing, refining, and maintaining a universal virus taxonomy. Considers: nature of virus genome and virus genetic diversity, virus replication strategies, and virus morphology.

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Monolayer cultures

When the bottom of the culture vessel is covered with a continuous layer of cells, usually one cell in thickness

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Primary Cell Culture

Growth of cells dissociated directly from the parental tissue. Cells have the same chromosomes and same number of chromosomes as the original tissue.

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Secondary (Transfer) Cell Culture

When a primary culture is sub-cultured. This is periodically required to provide fresh nutrients and growing space for continuously growing cell lines.

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Finite/Diploid Cell Lines

Homogenous population of a single cell type - fewer cell types. Derived mainly from embryos; or from secondary cell culture. Cells retain original morphology and diploid chromosome number. Growth rate is slow.

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Continuous Cell Lines

Divide indefinitely. Derived directly from cancer cells; or induce transformation of a primary of diploid cell strain to divide indefinitely. Abnormal morphology and chromosome number. FDA prohibits their use in vaccine production.

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Phenol Red pH Indicator

Red is normal color, at a pH of 7-7.5. If there is an accumulation of toxic substances in medium then it will become acidic and it will become yellow or orange in color.

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Carbon Dioxide (CO2) Level

Changes in atmospheric CO2 can alter the pH of the medium. Therefore, it is necessary to use exogenous CO2 when using media buffered with a CO2 bicarbonate based buffer.

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How will you dissociate/deattach adherent cells?

Use enzyme trypsin which is a proteolytic enzyme and cause lysis of adhesion factors. Or use integrins which rely on calcium

49

Cytopathogenic Effect (CPE)

Refers to damage or morphological changes to host cells during virus invasion

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Shell vial

Small borosilicate glass vial with a coverslip. Grow cells in coverslip or shell vial. Inoculate the virus into the vial. Virus grows in monolayers. Take cover slip out and drip it with fluorescent antibody and look under the microscope.

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Cultivation of viruses in eggs

Egg candling and egg inoculation

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When can you not use eggs for experiments?

If there is a crack in the eggshell, infertile egg, and blood ring indicated early embryonic death

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Routes of egg inoculation

1. Chorioallantoic membrane inoculation
2. Amniotic inoculation
3. Allantoic inoculation
4. Yolk Sac inoculation

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Yolk Sac Inoculation

Drill hole (use 22 gauge), place the inoculum below the embryo and within the yolk material. Seal the hole in the eggshell with scotch tape or melted wax.

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Allantoic Cavity Inoculation

26 gauge, drill hole in eggshell above or over the air sac. Inoculate specimen into the allantoic cavity.

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Amniotic Cavity Inoculation

26 gauge, drill a hole in the egg shell over the air sac, inoculate specimen into the amniotic cavity.

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Chorioallantoic Membrane Inoculation (CAM)

Drill two holes in the eggshell, one on the side and the other above the air sac. Move air sac to the side of the egg by gentle suction, using a rubber bulb. Inoculate specimen on the dropped CAM.

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Pocks on CAM

Most common lesions found in eggs. Assay is known as pocks assay. Pocks formed by vaccine virus on CAM.

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Ultracentrifuge

Provide sufficient gravitational force to efficiently sediment even the smallest viruses

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Rate-zonal centrifugation

Narrow zone on the top of a density gradient. Under centrifugal force, particles move at different rates depending on their mass.

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Buoyant density

If the object has exactly the same density as the fluid, then its buoyancy equals its weight. It will remain submerged in the fluid, but it will neither sink nor float.

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Isopycnic Point

The point where the buoyant density of a particle equals that of the surrounding density gradient medium.

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Isopycnic Centrifugation

Particles are separated solely on the basis of their buoyant density. Particles will never sediment to the bottom of the tube. Virus particles appear as visible bands.

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Virus Purification with Membrane Chromatography

Chromatography membranes are not utilized in purification of viruses and virus like particles and for impurity removal. The macroporous structure of the membrane allows large viruses to enter it and to bind to the inner pore surface easily.

Binding of the viruses on ion exchange membranes depends on charge distribution on the virus. Adsorption and subsequent elation of viruses can be achieved by anion and cation exchange membranes.

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Virus Quantification

Counts the number of viruses in a specific volume to determine the virus concentration

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Virus Titer

The lowest concentration of virus that still infects cells

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Biological - Viral Quantification Tests

Depend on a virus particle initiating a successful replication cycle. Plaque assays, pock assays, various endpoint titration methods.

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Physical - Viral Quantification Tests

Do not depend on any biological activity of the virus particle. More related on the counting. EM, Hemagglutination, ELISA, PCR, flow cytometry.

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Transmission Electron Microscopy (TEM)

Direct particle counts; the most direct method to determine the concentration of virus particles in a sample.

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Virus Counter 2100

The technology behind the virus counter 2100 is based on specialized version of flow cytometry developed specifically for use with nanometer scale particles.

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When using a virus counter ...

Each sample is stained with two different fluorescent dyes, one specific for nucleic acid, and the other specific for protein, and analyzed as they flow through a laser beam

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Hemagglutination Assay

Antigen concentration assessment. RBC in suspension becomes linked (agglutinated) by ND virus receptors. RBC settle to form a mat.

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High Performance Liquid Chromatographhy (HPLC)

Antigen concentration assessment. The concentrations of specific viral antigens may be quantified through UV analysis of fractions generated during HPLC.

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Single Radial Immunodiffusion (SRID)

Antigen concentration assessment. Radial diffusion of purified viral antigens (standards) and viral particles through agarose gel seeded with polyclonal antisera against a viral antigen.

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Monolayer Plaque Assay

A circular zone of white necrotic cells surrounded by viable cells in a monolayer. It is a functional measurement, and has no relation to actual number of viruses.

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Plaque Forming Units/ml (PFU)

Measures the number of virus particles capable of forming plaques per unit volume.

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Transformation Assay

Quantitative determination of titers of oncogenic viruses. Oncogenic viruses transform cells in culture. Transformed cells lose contact inhibition and become heaped upon one another.

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Quantal Assay

Measures the presence of absence of infection. Use for certain viruses that do not form plaques or for determining the virulence of a virus in animals or eggs.

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Lethal dose 50

Amount of virus that kills 50% of test subjects

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TCID50

A Tissue Culture Infectious Dose which will infect 50% of the cell monolayers challenged with the defined inoculum

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Multiplicity of Infection (MOI)

Is the average number of virus particles infecting each cell

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TCID50 Formula

(% Infection above 50% - 50%)/ (% Infection above 50% - % Infection below 50%)

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Permissive Cell

A cell in which a virus is able to replicate

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Non-permissive cell

Cells in which a factor or factors necessary to viral reproduction is not present or one detrimental to viral reproduction is present

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One-step Virus Growth Curve

1. Viral adsorption and entry
2. Viral uncoating and replication
3. Viral maturation
4. Viral release

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Burst Size

Number of infectious virions released per average cell

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Adsorption

During this period, virus attached to and enters cells, and the titer of free virus in the medium may actually decline

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Eclipse Period

Tie interval between uncoating ("disapperance" of viruses) and appearance, intracellularly, of first infectious progeny virion.

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Latent Period

The time before new infectious virus appears in the medium. I.e., from uncoating to just prior to the release of the first extracellular virions.

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Steps of Virus Replication

1. Attachment (adsoprtion)
2. Penetration (Injection)
3. Uncoating
4. Synthesis of viral components (nucleic acid and protein)
5. Assembly and maturation
6. Release in large numbers (lysis)

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Co-receptor

In some cases, binding to a cellular receptor is not sufficient for infection. An additional cell surface molecule, or co-receptor, is required for entry.

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Endocytosis

A process in which a substance gains entry into a cell without passing through the cell membrane. The process involves invagination and pinching off of small regions of the cell membrane, resulting in the non-specific internalization of molecules.

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Surface Fusion

Type of virus penetration. Only enveloped viruses. Membrane fusion or fusion proteins facilitates membrane fusion.

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pH dependent surface fusion and uncoating

Low pH in endosome promotes fusion of envelope with endosomal membrane; lysis of nucleocapsid by lysosomal proteases, and release of viral genome

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pH independent surface fusion and uncoating

The F protein catalyzes membrane fusion at the cell surface at neutral pH. The viral nucleocapsid is then released into the cytoplasm.

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Pore-mediated penetration

Penetration of viral genome into host cell (non-enveloped aka naked viruses). Inject their genome into the host cytoplasm through creation of a pore in the host membrane.

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Antibody-mediated penetration

Antibody (Ig - Fc) receptor enhances the entry of viruses into host cell

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Capping

Addition of 7-methylguanosine of the 5' end of RNA. Provides stability, binding of mRNA to ribosomes, and mark mRNA as "self".

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3'-Polyadenylation

Viral mRNAs can be polyadenylated by host or viral enzymes. A stretch of adenylated residues are added to the 3' end.

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Splicing

RNA splicing is a process that removes introns and joins exons in a primary transcript

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Exon

the portion of a gene that codes of amino acids

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Intron

a portion of a gene that does not code for amino acids

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Constituitive splicing

Every intron is spliced out; every exon is spliced in

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Alternative splicing

All introns spliced out; only selected exons spliced in. Results in mRNAs having different coding information derived from a single gene

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Monocistronic

A type of viral mRNA that encodes one polypeptide. Singe RNA that will encode one protein.

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Polycistronic

A type of viral mRNA that encodes several polypeptides.

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Exocytosis

By budding through the membrane of golgi apparatus or ER. Vesicles containing the virus then migrate to the plasma membrane and are released by exocytosis

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Extracellular Spread

Released viruses in extracellular environment. Travel to a new cell. Infect new host cell. Same replication cycle repeated etc.

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Intercellular Spread

Spread from cell-to-cell without contact with extracellular environment. Results in rapid virus dissemination, evasion of immune system and persistent infections

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Disseminated infection

Infection spreads beyond the primary site of infection

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Systemic infection

If a number of organs or tissues are infected

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Viremia

The presence of a virus in the blood. Virus may be free in the blood or in a cell.

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Passive viremia

Direct inoculation of virus in the blood. Bite of arthropods or contaminated syringe

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Primary viremia

Initial entry of virus into the blood after infection

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Secondary viremia

Virus has replicated in major organs and once more entered the circulation

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Active viremia

Viremia following initial virus replication in host. Release of virions from the initial site of replication, such as lymphatics or epithelium of intestine, to the blood stream

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Neurotropic virus

Viruses that can infect neural cells. Infection may occur by neural or hematogenous spread.

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Neuroinvasive virus

Viruses that enter the central nervous system (spinal cord and brain) after infection or a peripheral site.

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Neurovirulent virus

Viruses that cause disease of nervous tissue, manifested by neurological symptoms and often death.

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Retrograde spread

Travel opposite direction of nerve impulse flow. Invades axon terminals and then spread to dendrite or cell body, and then cross synapse to reach next axon terminal.

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Anterograde spread

Travel in direction of nerve impulse flow. Virus invades dendrites or cell bodies and then spread to axon terminals, and then cross synaptic contacts to invade dendrite of next neuron.

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Centripetal Movement of Virus

Towards to the CNS/Brain

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Centrifugal Movement

From CNS, within peripheral nerves, to other location in body

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Acute Infection

Usually intensive shedding over a short period of time

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Persistent Infection

Can be shed at lower titers for months to years

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Tropism

The specificity/affinity of a virus for a particular host tissue

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Pantropic Viruses

Can replicate in more than one host organ/tissue

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Viral Enhancers

Gene activators that increase the efficiency of transcription of viral or cellular genes, facilitating virus replication

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Vesicles

Small distinct elevation with fluid

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Ulcers

Opening in the skin caused by sloughing of necrotic tissue, extending past the epidermis

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Nodules

Palpable, solid, elevated mass nodules with distinct border, tumors extending past the epidermis

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Warts

Are benign (not cancerous) skin growths that appear when a virus infects the top layer of the skin

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Papules

Papular stomatitis in cattle

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Erythema

Redding of skin, consequence of systemic viral infections (endothelial injury in blood vessels throughout body, including those of the subcutaneous tissues)

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Viral-bacterial synergism

When virus and bacteria cause more harm together then they would alone

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Progressive Demyelination

Without the myelin sheath the nerve signals are not delivered properly. Will find seizures as a common sign.

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Petechiae Hemorrhage

pinpoint hemorrhage

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Ecchymoses

large areas of hemorrhage with ill defined margins

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Disseminated Intravascular Coagulation (DIC)

Widespread activation of the clotting cascade that results in the formation of blood clots in the small blood vessels througout the body

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Teratogenesis

The abnormal development of arrests in development of the embryo or fetus. Results in death or malformation.

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Virus Induced Immunopathology

Tissue injury mediated by host immune response to virus infection.

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Immunopathology

is often the cause of damage with viruses that are relatively non-cytolytic and persistent

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Cytokines

broad and loose category of small proteins that are important in cell signaling. They act as mediators and regulators of immune processes, but also cause inflammation.

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Monokines

cytokines produced by mononuclear phagocytic cells

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Lymphokines

cytokines produced by activated lymphocytes, especially Th cell

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Interleukin

cytokines that act as mediators between leukocytes

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Infectious bursal disease

Virus replication causes atrophy of the bursa and a severe deficiency of B lymphocytes, resulting in immunosuppression.

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Latent (persistent) infection

Infectious virus is not demonstrable except when reactivation occurs. Reactivation is often stimulated by immunosuppression and/or by the action of a cytokine or hormone

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Chronic (persistent) infection

Virus is continuously shed from or is present in infected tissue. Established host immunity is unable to clear virus from acute infection.

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Slow (persistent) infection

Prolonged incubation period, lasting months or years

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Primary CPE

Induced by viral replication and viral proteins toxic to host cells

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Secondary CPE

effects of metabolic needs of the virus

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Complete destruction of cells

Most severe form of CPE. All cells in the monolayer rapidly shrink, become dense (pyknosis), and detach from the glass within 72 hours.

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Subtotal destruction of cell

consists of detachment (death) of some, but not all of the cells in the monolayer.

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Focal destruction of cells

produce localized areas (foci) of infection

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Pyknosis

degenerative condition of a cell nucleus marked by clumping of the chromosomes, hyperchromatism, and shrinking of the nucleus.

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Cell fusion (synctium or polykaryon formation)

Involves the fusion of the plasma membranes of four or more cells to produce an enlarged cell with four or more nuclei. Prone to premature cell death.

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Inclusion bodies

An abnormal structure in a cell nucleus or cytoplasm or both

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Negri bodies

Consists of ribonuclear proteins produced by the rabies virus

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The intrinsic pathway

the mitochondrial pathway is activated as a result of increased permeability of mitochondrial membranes subsequent to cell injury, such as the associated with viral infection

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The extrinsic pathway

the death receptor pathway is activated by engagement of specific cell-membrane receptors, which are members of the TNF receptor family.

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Non-cytocidal Viruses

Usually do not cause immediate death of cells in which they replicate. They often cause persistent infection.

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Cell Transformation

Is the changing of a normal cell into a cancer cell

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Neoplasia

Is descriptive term that denotes an abnormal tissue overgrowth that may be either localized of disseminated. It is the process that leads to the formation of neoplasms (syn. Carcinogenesis)

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Oncology

study of neoplasia and neoplasms

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Benign Neoplasm

Is a growth produced by abnormal cell proliferation that remains localized and does not invade adjacent tissue

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Malignant Neoplasm

(Syn. Cancer) is locally invasive and may also be spread to other parts of the body (metastasis)

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Oncogenic viruses:

Viruses that cause or give rise to tumors

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Neoplasms (tumors)

Arise as a consequence of the dysregulated growth of cells derived from a single, genetically altered progenitor cell

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Metastatsis

Is the spread of cancer cells from the part of the body where it started (the primary site) to the other parts of the body.

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Proto-oncogenes

are often involved in growth signaling and anti-apoptotic pathways

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Oncogenes

Mutated forms of proto-oncogenes or aberrantly expressed proto-oncogenes. Function in an unregulated manner.

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Tumor Suppressor Genes

encode proteins that inhibit cell proliferation (by holding cell cycle at G1 phase)

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Rb: Retinoblastoma Protein

Tumor suppressor protein, alternates between phosphorylated and unphosphorylated state. The role of un-phosphorylated Rb is to bind to the transcription factor E2F, not allowing cell division to procee from G1 to S phase. Phosphorylated Rb cannot bind E2F from its inhibition and allows the cell cycle to progress

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P53 Protein

P53 activates the DNA repair system and stops the cell cycle at the G1 checkpoint (before DNA replication)

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Productive Infection in Permissive Cell

The virus completes its replication cycle, resulting in cell lysis

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Non-productive infection in Non-permissive cell

The virus transforms the cell without completing its replication cycle

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C-onc genes/proto-oncogenes

Are host genes that encode important cell signaling products that regulate normal cell proliferation

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V-onc genes

Separated from the cellular machinery that normally controls gene expression (lacks introns), so they have power of unregulated expression

180

Slow/chronic transforming retrovirus

Integration of retroviral genes into host chromosomal DNA can occur at promoter or enhancer sites that drives the increase in proto-oncogene/C-onc gene expression, leading to malignant transformation of the cell

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Promoter

DNA sequence at which DNA-dep RNA polymerase binds to initiate transcription

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Enhancer

A transcriptional regulatory sequence located some distance from the promoter; it increases the rate of initiation of transcription

183

Perforin

Can produce pores in plasma membranes

184

Granzymes

Proteins that can initiate apoptosis

185

Granulocytosis

Presence in peripheral blood of an increased number of granulocytes, i.e. Neutrophils, eosinophils, basophils, mast cell

186

Virus neutralization

Neutralizing antibodies prevent virus attachment and entry into host cell. They bind to the viral capsid or host envelope

187

Opsonization

Coating of virions with antibodies. Antibody coated virion is recognized and phagocytosed by macrophages and sometimes by neutrophils

188

Clumping of viruses (Immunocomplex formation)

Reduced the number of viral particles available for cell invasion

189

Activation of Complement System

Opsonization - enhancing phagocytosis of antigens
Chemotaxis - attracting macrophages and neutrophils
Lysis - rupturing membranes of foreign cells/pathogens
Agglutination - clustering and binding of pathogens together (sticking)

190

Antigenic plasticity

Rapid changes in the structure of the viral antigen. May be the result of mutation, reassortment or recombination

191

Antigen multiplicity

Antigenic variants with little or not cross-reactivit

192

Negative Cytokines Regulation

Blocking interferon receptor signal

193

Virokines

Some viruses synthesize proteins which are homologs of cytokines/interferons.

194

Viroreceptors

Some viruses encode proteins that are homologs bind to cytokines and serve as competitive antagonist.

195

Virus Epidemiology

The study of determinants, frequency, dynamics, and distribution of viral disease in populations

196

Cast-fatality rate

The number (%) of deaths among the clinically ill animals

197

Mortality rate

The number (%) of animals in a population that die from a particular disease over a specified period of time

198

Morbidity rate

The % of animals in a population that develop clinical signs attributable to a particular virus over a defined period of time (commonly the duration of an outbreak)

199

Incidence

The number of new cases that occur in a population over a specified period time

200

Incidence rate or attack rate

a measure of occurrence of infection or disease in a population over time

201

Prevalence

The number of occurrences of disease (old and new cases), infection, or related attributes (antibodies) in a population, at a particular point of time

202

Sporadic viral disease

Viral diseases occurring occasionally, singly, or in scattered instances, and in an irregular and haphazard manner

203

Enzoonotic viral diseases

(endemic in humans), the constant presence of a viral disease within a given geographic area or population group

204

Epizootic viral diseases

(epidemic in humans), the occurrence of more cases of viral diseases than expected in a given area of among a specific group of people/animals over a particular period of time. Refers to peaks in disease incidence that exceed the endemic/enzootic baseline or expected incidence of disease

205

Panzootic viral disease

(pandemic in humans), a virus epidemic occurring over a very wide area (several countries or continents) and usually affecting a large proportion of the population

206

Carrier

Animals that have contracted an infectious viral disease but display no clinical symptoms

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Incubatory (acute) carriers

Animals that shed virus during the incubation period of the disease

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Convalescent (chronic) carriers

Animals that shed the virus during recovery from disease

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Inapparent carriers

Carrier state may exist in an animal with an infection that is inapparent throughout its course

210

Contagious disease

A disease that is spread from one person or organism to another by direct or indirect contact

211

Reservoir

The habitat in which an infectious agent normally lives, grows or multiplies; reservoirs include human reservoirs, animal reservoirs, and environmental reservoirs. May be animate or inanimate

212

Surveillance

The systematic collection, analysis, interpretation, an dissemination of health data on an ongoing basis, to gain knowledge of the pattern of disease occurrence and potential in a community, in order to control and prevent disease in the community

213

Direct-contact transmission

involves actual physical contact between an infected animal and a susceptible animals (e.g. licking, rubbing, biting). STDs.

214

Droplet transmission

Direct-contact, transmission of virus in droplet nuclei (saliva or mucus) that travel less than 1 meter from the source to the susceptible host

215

Indirect-contact transmission

Occurs via fomites such as shared eating containers, bedding, dander, restraint, devices, vehicles, clothing, improperly sterilized surgical equipment, or improperly sterilized syringes or needles

216

Fomites

An inanimate object or substance that is contaminated with the infectious agent and is capable of transmitting infectious organism from one individual to another

217

Airborne transmission

Spread of infectious agents by droplet nuclei in dust that travel more than one meter, sometimes for miles, from the infected to the susceptible host

218

Mechanical transmission - passive transmision

infectious agent undergoes either a necessary part of its life cycle

219

Biological transmission

infectious agent undergoes either a necessary part of its life cycle before transmission

220

Extrinsic incubation period

replication of the ingested virus, initially in the insect gut, and its spread to the salivary gland takes several days

221

Overwintering

the survival of the virus from one vector season to the next (period during which arthropods hibernate)

222

Trans-ovarial transmission

The virus is transmitted from the mother tick through infected eggs to the next generation of ticks

223

Trans-stadial transmission

the virus is transmitted from larva or nymph to next stage of development (nymph or adult). But not transmitted vertically (from mother tick to eggs and next generation)

224

Arboviruses

A class of viruses transmitted to humans by arthropods such as mosquitoes and ticks.

225

Enzoonotic cycle (sylvatic or jungle cycle)

the natural transmission of virus betwen wild animals/birds (vertebrate hosts) and primary insect vectors

226

Epizootic cycle (rural cycle)

the virus is transmitted between non-wild or domestic animals and the primary or accessory insect vectors

227

Urban cycle

the virus cycles between humans and insect vectors

228

Amplifying host

is in which the level of virus can become high enough that an insect vector such as a mosquito that feeds on it will probably become infectious

229

Dead end host or incidental host

A host from which infectious agents are not transmitted to other susceptible hosts. They do not develop sufficient viremia to be picked up by the insect vectors

230

Bridge vector

Is an arthropod that acquires virus from an infected wild animal and subsequently transmits the agent to human or secondary host

231

Common Vehicle Transmission

Includes fecal contamination of food and water supplies and virus contaminated meat or bone products

232

Iatrogenic Transmission

Infection that is transferred during medical or surgical practice

233

Nosocomial transmission

Occurs while an animal is in a veterinary hostpital or clinic

234

Vertical transmission

Infection that is transferred rfom dam to embryo or fetus, or newborn before, during, or shortly after parturition (colostrum, milk, or fecal contamination of teats)

235

Population size is crucial

A virus may disappear from a population if supply of susceptible hosts is exhausted. This depends on size of population, immunity and pattern of virus shedding

236

Host range

Many viruses can infect more than one host

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Herd Immunity

Is a form of immunity that occurs when the vaccination of a significant portion of a population (or herd) provides a measure of protection for individuals who have not developed immunity

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Incubation period

refers to the internal between infection and the onset of clinical signs. In many diseases there is a period during which animals are infectious before they become sick

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Prodromal period

The first signs and feelings of illness after incubation period. The period of early symptoms of a disease occurring after the incubation period and just before the appearnce of the characteristic symptoms of the disease

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Acute period

when the disease is at its height. Sever clinical signs

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Decline period

period when clinical signs begin to subside

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Convalescent period

the body gradually returns to its pre-diseased state and health is restored

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Biohazard

Biological substances that pose a threat to the health of living organisms, primarily that of humans

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Biosafety

Laboratory biosafety described the containment principles technologies and practices that are implemented to prevent the unintentional exposure to pathogens and toxins, or their accidental release

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Aerosol

Very small droplets of fluid that can spread via air. Viruses can spread in lab through aerosol route

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Biosafety Cabinets (BSC)

An enclosed, ventilated laboratory workspace for safely working with materials contaminated with (or potentially contaminated with pathogens requiring a defined biosafety level)

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Biosecurity

Laboratory biosecurity described the protection, control and accountability for valuable biological materials within laboratories, in order to prevent their unauthorized access, loss, theft, misuse, diversion or intentional release

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Virus isolation sampling

Specimens should be collected as soon after onset of symptoms as possible, because maximal amounts (titers) of virus are usually present at the onset of signs

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Serological test sampling

Two blood specimens are generally collected - one during the convalescence period

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Molecular diagnostics sampling

Obtained during the early part of illness

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Viral Transport Medium (VTM)

Prevents specimen from drying, help maintain viral viability and retards the growth of microbial contaminants. Consts of a buffered salt solution to which has been added protein and antimicrobials

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Negative Stain Electron Microscopy

Following bombardment with an electron beam, the stain absorbs electrons in much higher amounts than the sample. The parts of the viral particles that are not penetrated by the stain appear as electron-lucent (low, affinity, less electron density) areas on an opaque (high-affinity, electron dense) background

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Transmission Electron Microscope (TEM)

Based on transmitted electrons. Seeks to see what is inside or beyond the surface

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Scanning Electron Microscope (SEM)

Based on scattered electrons, focuses on the sample's surface and its composition. Produces 3D images.

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Assay

Qualitative or quantitative measurement of a target entity/analyte, such as a drug or biomolecule

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Gold Standard Test

A diagnostic test that is considered to be the most accurate and best available under a particular condition or set of conditions

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Negative Predictive Value (NPV)

the probability that a negative test result accuraetly indicates the abscence of infection

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Sensitivity

The probability (percentage) that cases with the infection (determined by the result of the reference of "gold standard test") will have a positive result using the test under evaluation

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Specificity

The probability (percentage) that cases without the infection (determined by the result of the reference of "gold standards test") will have a negative result using the test under evaluation

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Positive Predictive Value (PPV)

The probability of a positive result accurately indicating the presence of infection

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Serum

The clear yellowish fluid obtained upon separating whole blood into its solid and liquid components after it has been allowed to clot. Plasma - clotting factors = serum.

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Collection of plasma

Plasma is produced when whole blood is collected in tubes that are treated with anticoagulant. The blood does not clot in the plasma tube. The cells are then removed by centrifugation. The supernatant, designated plasma is carefully removed from the cell pellet.

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Typical ELISA

Enzyme tagged to antibody which is bound to antigen will change color of substrate. Intensity of color indicates more positive reaction

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Direct ELISA

Antigens are immobilized and enzyme conjugated primary antibodies are used to detect or quantify antigen concentration. The specificity of the primary antibodies that recognize the primary antibodies.

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Indirect ELISA

Primary antibodies are not labeled, but detected instead with enzyme - conjugates secondary antibodies that recognize the primary antibodies

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Sandwich ELISA

The antigen to be measured is bound between a layer of capture antibodies and a layer of detection antibodies. The two antibodies must be very critically chosen to prevent cross reactivity or competition of binding sites

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Competitive ELISA

The antigen of interest from the sample and purified immobilized antigen compete for binding to the capture antibody. A decrease in signal when compared to assay wells with purified antigen alone indicates the presence of antigens in the sample. The more antigen in the sample, the more Ag-Ab complexes are formed and so there are less unbound antibodies available to bind to the antigen in the well, hence "competition"). A substrate is added, and remaining enzymes elicit a chromogenic of fluorescent signal. Weaker signal indicates presence of antigens in sample.

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Fluorescence Antibody Test (FAT)

The antibodies are labelled with a fluorescent dye (most commonly used in fluorescent isothiocyanate) [FITC] or rhodamine). Visible fluorescence appears following Ag-Ab reaction.

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Direct FAT

Labelled antibodies are added onto the sample (antigen). Visible fluorescence appears at the binding sites of the specific antibodies (antigen-antibody binding).

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Indirect FAT

IFAT employs a secondary antibody labeled with a fluorescent marker that recognizes the primary antibody bound to antigen

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Immunohistochemistry

The antibody is tagged with an enzyme, generally horseradish peroxidase. The enzyme reacts with a substrate to produce a colored product that can be visualized in the infected cells with a standard light microscope.

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Immunohistochemistry Direct Assay

Enzyme tagged with primary antibody that binds to antigen. Upon successful antigen-antibody binding, tagged enzyme catalyzes substrate to produce color product.

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Immunohistochemistry Indirect Assay

Enzyme tagged to a secondary antibody that is specific against primary antibody

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Immunochromatography (lateral flow devices)

A form of POC test that is simple to perform, easy to carry, and does not require specialized equipment. Antibodies on the chromatographic paper, when the liquid sample is dropped on the sample pad, the antigen in the sample forms an immunocomplex with the antibody labeled with colloidal gold. Resulting in generating a colored red purple line. Indicates the presence of antigen of interest in the sample.

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Point of Care (POC)

Diagnostic testing performed at or near the patient's site of care

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Agglutination

Using the property of specific antibodies to bind to many antigens into a single clumps thereby forming large complexes, which are easily precipitated

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Hemagglutination and Hemagglutination inhibition test

relies on the property of some pathogens (mainly viruses) to non-specifically agglutinate erythrocytes

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Agar gel immunodiffusion test

Performed in petri dish with agar. Take a petri dish and make two wells. One well you supply antigen in other well you load antibody this antigen and antibody will diffuse toward each other. If it correspond to the antibody it will produce a white line also known as antibody antigenic precipitate

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Complement Fixation Test - POSITIVE REACTION

Serum from patient has Ab against Virus A. Add ready made Virus A Ag. Ab will bind to Ag A. Add complement which will bind to the Ag-Ab complex. As a result free complement is not available. Add sheep RBC and anti-sheep RBC Ab complement is available to mediate hemolysis of sheep RBC. Intact sheep RBC settle at bottom of well.

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Complement Fixation Test - NEGATIVE REACTION

Serum from patient is negative to Virus A, it will have no Ab. We add ready made virus A Ag. Viral Ag is free as no Ab is present. Add complement, it will also be free as there is no Ag-Ab complex to bind to. Add sheep RBC and anti-sheep RBC Ab. Free complement is available and mediates hemolysis of sheep RBC. Find the hemolysis of sheep RBC.

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Immunoblotting

Run a sample in verticle gel and that will separate different proteins based on molecular weight. Transfer to nitrocellulose membrane from the gel. Treat it with Ab. Specific Ag bind to corresponding labelled Ab we get dark bands visualized.

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Hemadsorption

Glycoproteins are inserted into host cell membrane at sites of budding of enveloped viruses. This allows monolayer cells to adsorb erythrocytes on their cell membranes.

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Hemadsorption - Inhibition Assay

Infected monolayer cells are incubated with known specific Ab. Abs bind to viral glycoproteins (spikes) in cell membrane. Attempts are made to wash away antibodies. Antibodies remain bound to viral proteins. Pretreated monolayer cells are incubated with RBCs. RBC binding is inhibited.

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Neutralization Assays

Loss of infectivity through reaction of the virus with specific Ab. Presence of unneutralized virus may be detected by reactions such as CPE, hemadsorption/hemagglutination, plaque formation disease in animal. Ab-bound virus (neutralized) becomes non-infectious and cannot produce desired effects in eggs, cell-lines or animals.

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IgM class-specific antibody assay

Because IgM antibodies appear early after infection by drop to low levels within 1-2 months and generally disappear altogether within 3 months, they are usually indicative of recent infection