Viruses, Viroids and Prions Flashcards

Question

Discuss the rules for Viral Nomenclature? How are different orders, families and genera named? How do you distinguish species vs subspecies. Give two main examples of subspecies?

Answer 1

Viral Nomenclature Order names end in - ales Family names end in -viridae Genus names end in -virus Descriptive common names are used for species Subspecies are designated by a number **1. Human immunodeficiency virus 1 (HIV-1) is an Enveloped retrovirus that infects humans*** (not have genus ) **2. Severe acute respiratory syndrome coronavirus 2*** (SARS-CoV-2) is a coronavirus that infects humans ( coronavirus is genus name) -Virus specific epithets are not used- no established binomial nomenclature -Written in italics and first letter is capitalized examples: -Order Monoengavirales -Family Paramyxoviride -Genus Morbillivirus

Answer 2

Viral species: A group of viruses sharing the same genetic information and ecological niche (host)

Answer 3

Class I: All families are Double stranded DNA -Family Adenoviridae and Papovaviridae are Nonenveloped. Family Poxviridiae and Herpesviridae are Enveloped

Answer 4

Class II Single stranded DNA Family Parvoviridae is NON-Enveloped

Answer 5

Class III: Double stranded RNA Family Reoviridae is NON-ENVELOPED

Answer 6

Class IV: ALL are Single-Stranded RNA, Positive strand Families Picornaviridae and Caliciviridae are NON-ENVELOPED Family Togaviridae, Flaviviridae, Coronaviridae, are ENVELOPED

Answer 7

Class V ALL families are Single stranded RNA, Negative strand -Families Rhabdoviridae and Filoviridae and Paramyxoviridae have ONE strand of RNA, ENVELOPED -Families Orthomyxoviridae, Bunyaviridae, and Arenaviridae have MULTIPLE Strands of RNA, ENVELOPED

Answer 8

Class VI Family Retroviridae is Single-Stranded RNA, produce DNA - ENVELOPED

Answer 9

Class VII Family Hepadnaviridae are Double-stranded DNA, use Reverse transcriptase, ENVELOPED

Answer 10

Class V Family Deltaviridae Characteristics : Single stranded RNA, Negative strand -One strand of RNA, ENVELOPED -Virusoid or Satelite RNA *Note Hepatitis D (Delta) is NOT a virus, but a virusoid

Answer 11

Bacteriophage: a virus that infects and replicates within bacteria Properties of bacteriophages: - replicate inside bacterial cells - Consists of a protein coat that encapsulates a pieced of nucleic acid, which can be either double or single-stranded DNA or RNA -Classified as either Virulent or Temperate

Answer 12

Virulent phage- the end result of successful cell infection is the realist of PHAGE progeny

Answer 13

Temperate Phage: The end-result of successful cell infection can either be Release of Phage progeny OR the Formation of a prophage

Answer 14

Prophage: Bacteriophage whose DNA has entered the cell, is replicated in concert with the host genome. but its genes are indefinitely repressed by a phage encoded repressor protein

Answer 15

Lysogen: Bacteria that carries a prophage

Answer 16

Prophage induction- emergence of a prophage from its latent state

Answer 17

Phages: -Phage T4 attaches to a Porin protein -Phage lambda attaches to a maltose transport protein -P1 to a Calcium transporter

Answer 18

Life Cycle of a T-even bacteriophage 1. Attachment: phage attaches to host cell 2. Entry: phage penetrates host cells and injects its DNA 3. Biosynthesis: Phage DNA. directs this synthesis of viral components by the host cells 4. Maturation: Viral components are assembled into visions During steps 3-4 are ECLIPSE period 5. Release: Host cell lyses, and new visions are released

Answer 19

Phage DNA: start with Tail attaching to baseplate pin. Then sheath forms around tail and DNA is inserted into cashed, then Caspid with DNA will attach to tail (with sheath) and tail fibers attaching to tail, and cashed (head)

Answer 20

Phage Lambda Lysogenic cycle 1. Phage attaches to bacterial cell wall and injects DNA 2. Phage DNA circularizes 3. Phage DNA integrates into bacterial chromosome to become a prophage 4. Cell division occurs -Dormancy is maintained by a phage protein that represses the expression of all phage genes except repressor gene 5. Dormant prophage is propagated indefinitely in progeny lysogenic cells

Answer 21

Lambda phage genome -cut sites, Head/tail genes, att site, recombination sites, immunity sites, DNA replication site, and lysis site.

Answer 22

The prophage integrates at specific sequence *(the att site) * in the bacterial chromosome

Answer 23

Integration site for bacteriophage 22 is att P22 -integration site for bacteriophage lambda is att lamda

Answer 24

Induction of a Lysogenic Bacterium (for Phage lambda) 1. Blockage of DNA synthesis (by UV irradiation, for example) causes a cascade of reactions that destroys the phage repressor 2. Phage genes are expressed and prophage excises from chromosome 3. Phage DNA replicates and directs synthesis of new phage particles 4. Lysis relates progeny phage

Answer 25

lambda induction: various DNA damaging treatments INDUCE lambda prophages. Cellular repair of gapped DNA results in the accumulation of single-stranded DNA which binds and activates the E.coli Rec A protein. This activated protein then proteolytically cleaves the lambda repressor protein -Efficient excision from bacterial genome requires a phage encoded protein

Answer 26

Only certain bacteriophages can be lysogenic: -Bacteriophage lambda -bacteriophage P22 and many others

Answer 27

Cascade -UV light can cause damage in DNA strand and lead to break in DNA. -This causes a protein called Rec A to become activated -Activated Rec A will when Cleave Cl to for lytic growth OR cleave Lex A to activate DNA repair genes

Answer 28

Specialized transduction: -prophage excises imperfectly, taking nearby DNA with it. *Limited to few genes surrounding integration site * *requires LYSOGENY*, integration of phage DNA into bacterial chromosome Generalized transduction: - as bacterial genome is degraded, some is packaged into phage -Can transduce visually *any gene in chromosome* -Does NOT require lysogeny

Answer 29

Specialized Transduction -The virus carries a SPECIFIC gene or set of neighboring genes from a host to another host depending on where the att site is. process: 1. Prophage exists in galactose-using host (containing gal gene) 2. Phage genome excises, carrying with it the adjacent gal gene from the host 3. Phage matures and cell lyses, releasing phage carrying gal gene 4. Phage infects a cell that cannot utilize galactose (lacking gal gene) 5. Along with the prophage, the bacterial gal gene, becomes integrated into the new host's DNA. 6. Lysogenic cell can now metabolize galactose

Answer 30

Generalized transduction : the virus carries a RANDOM gene or genes from a host to another host process: 2. Phage DNA and proteins are made and then bacterial chromosome is broken into pieces 3. Occasionally during phage assembly, pieces of bacterial DNA are packaged in a phage caspid. Then the donor cell lyses and releases phage particles containing DNA 4. A phage carrying bacterial DNA infects new host cell, the recipient cell 5. Recombination can occur producing a recombinant cell with a genotype different from both donor and recipient cells.

Answer 31

Lysognic conversion: the bacterium has a new property due to presence of the prophage for example: a disease-causing bacterium may produce a toxin encoded on a gene in the prophage

Answer 32

Diseases: * cholera: caused by bacterium Vibrio cholera and bacteriophage CTX phage. The gene product formed is cholera toxin *Hemorrhagic diarrhea is caused by bacterium Escherichia coli and bacteriophage lambda phage. The gene product formed is the shiga-like toxin *Botulism/food poisoning is caused by bacterium Clostridium botulinum and bacteriophage clostridial phages The gene product formed is botulinum toxin *scarlet fever is caused by bacterium Streptococcus pyogenes that have bacteriophage T12. The gene product formed are erthyogenic toxins

Answer 33

Major structures of mammalian cell: -plasma membrane -ribosomes -nucleotides -amino acids -sugars -DNA polymerases -Golgi apparatus -centriole -nucleus -endoplasmic reticulum -lysosome -mitochondrion

Answer 34

Steps of virus multiplication 1. *Attachment* to specific cell surface molecules 2. *Entry*of either the virus particle or its genome 3. *Uncoating*- separation of the viral nucleic acid from its protein coat 4. **Latent infection ** were the virus is present but produces few or no new viruses 5. Biosynthesis of nucleic acid and proteins 6. Maturation including assembly and incorporation of the genome into the cased 7. Release of many more viruses by budding (enveloped viruses) or lysis of the cell *This latent infection, happens only in a few specific viruses; ex lambda bacteriophage, herpesviruses, retroviruses

Answer 35

Attachment; a virus attaches to a specific receptor molecule on the cell surface - in contrast to attachment for bacteriophages, animal viruses DO NOT have appendages like tail fibers of some bacteriophage and attachment sites for viruses are distributed over the SURFACE of the virus

Answer 36

Attachment; animal cell surface receptors -cell surface receptors are used for various viruses Glycoproteins are also receptors -these proteins have normal functions for the host that are hijacked by the virus.

Answer 37

Entry: -following virus attaches to host receptor 1) some enveloped and nonenveloped viruses enter by a variety of ENDOCYTIC methods ex: togavirus enters by pinocytosis 2) Some noneveloped viruses insert their genome into the host cytoplasm through creation of a PORE in the **Host plasma membrane or vesicle membrane**. -The virus has a pore-forming peptide in its capsid -some enveloped viruses enter by *FUSION* Ex: Herpesvirus enters by Fusion (fusion of viral envelope and PM, and then capsid released into cytoplasm)

Answer 38

Structural study showing the Poliovirus viral RNA directly translocating from the particle across the membrane, similar to bacteriophage

Answer 39

Uncoating; Separating of the viral nucleic acid from its protein coat -process varies with type of virus and include... 1. Lysosomal enzymes degrade proteins of viral capsid 2. Virus encodes a specific enzyme for capsid degradation 3. Low pH of endosome triggers uncoating REVIEW

Answer 40

In animal cell nucleic acid biogenesis: mammalian cells lacks: -RNA-dependent DNA polymerase -RNA-dependent RNA polymerase

Answer 41

Biosynthesis of viral nucleic acids -if a virus needs to... make DNA from DNA, it uses the host's DNA-dependent DNA polymerase -Unless its a CYTOPLASMIC virus, then it uses its OWN To make RNA from DNA, -it uses the host's RNA polymerase -unless its Cytoplasmic To make RNA from RNA, - if it is a POSITIVE strand virus, it can ENCODE its own polymerase - if it is a NEGATIVE strand virus, it must BRING IN its own polymerase To make DNA from RNA, -it must BRING IN its own polymerase (reverse transcriptase)

Answer 42

*For Adenoviridae and Papoviridae, Both Transcription and replication occur in the cell nucleus using cellular polymerases * *However, Herpesviridae uses a viral DNA polymerase in the Nucleus, while Poxviridae uses a viral DNA polymerase in the Cytoplasm* process: 1. attachment of vision to host cell 2. entry and uncoating (vision enter cell, its DNA is uncoated) 3. a portion of viral DNA is transcribed producing mrNA 4. Biosynthesis: viral DNA replicated and some viral proteins are made 5. late translation: capsid protons are made ' 6 . maturation of visions 7. release of virions

Answer 43

The + RNA genome serves as mRNA for the synthesis of new virus proteins, including the virus polymerase -The virus polymerase (red) copies the +RNA into a - RNA and copies the -RNA into another +RNA *Viral genome is injected into the cytoplasm* process 1. Attachment of vision to host cell 2. Entry and uncoating; releasing viral RNA and proteins. -the viral genome is injected into the cytoplasm 3. RNA replication by viral RNA-dependent RNA polymerase 4. Translation and synthesis of viral proteins 5. Maturation and release *Piconaviridae: example of family that has + RNA virus *

Answer 44

Multiplication of -RNA virus - RNA CANNOT be translated directly; viral polymerase must be carried within the virus -Viral polymerase (blue) copies - RNA into + RNA for translation -Viral polymerase copies the + RNA into more - RNA - Rhabodiviridae is family of organisms that have -RNA virus process: 1. Attachment 2. Entry and uncoating (releases viral RNA and proteins) -Viral genome is injected into the cytoplasm -virus polymerase is transported in with the genome 3. RNA replicate by viral RNA- dependent RNA polymerase (positive strand (mRNA) must first be transcribed from the - viral genome before proteins are made) 4. translation and synthesis of viral proteins 5. Maturation and release

Answer 45

Mutliplication of dsRNA virus (Reoviridae) - Viral polymerase must be carried into the cell inside the virus -The Double stranded RNA (dsRNA) stays inside the virus particle and Cannot be translated directly, so viral polymerase copies the dsRNA into mRNA and more dsRNA process: 1. Attachment of capsid to host cell 2. Entry and uncoating (releases viral RNA and proteins) virus does not completely uncoat -virus polymerase is carried in with the genome 3. RNA replication by viral dependent RNA polymerase -mRNA is produced inside the capsid and released into cytoplasm of the host 4. Translation and synthesis of viral proteins -RNA polymerase initates the production of negative strand. The mRNA and - strands from the dsRNA that is incorporated as new viral genome -dsRNA and polymerase are incorporated into the capsid 5. Maturation and relate

Answer 46

Multiplication of a Retroviridae: uses two identical + strands of RNA, has revere transcriptase (enzyme), envelope, capsid, host cell and virus. process: 1. Retrovirus enters by fusion between attachment spikes and host cell receptors 2. *Uncoating releases the two viral strands and viral enzymes reverse transcriptase, integrate and protease 3. *reverse transcriptase copes viral RNA to produce double-stranded DNA* 4. The new viral DNA is transported into the host cell's nucleus, where it is integrated into a host cell chromosome as a provirus by viral integrate. The provirus may be replicated when the host cell replicates (DNA integrates into host genome) 5. Transcription of the provirus may also occur, producing RNA for new retrovirus genomes and RNA that encodes retrovirus capsid, enzymes, and envelope proteins (virus DNA is transcribed like the host's own genes) 6. Viral proteins are processed by viral protease. some of the viral proteins are moved to the host plasma membrane 7. Mature retrovirus leaves the host cell, acquiring an even lope and attachment spikes as it buds out.

Answer 47

The One-step viral growth curve: describes the events that occur during reproduction of virus or (life cycle of virus) -It is called one-step growth curve because it is on ONE replication cycle (1 life cycle) Has diffrent periods: -1. phase (at o minutes) where viruses contacts the cells 2.* Eclipse period: the time of synthesizing viral proteins and nucleic acids followed by maturation inside host cell 3. Then viruses are related form the host cell 4.* Acute infection period were there is a rapid onset of disease, short period of symptoms, quick resolution MOI: multiplicity of infection virus: virus number: host number

Answer 48

REVEIW this do we have to know all info on Lisle 73 and 74?

Answer 49

Why does this matter: mutation rates -DNA synthesis has a LOW error rate DNA polymerases can "proofread: -The cell has DNA-repair mechanisms -RNA synthesis has a HIGH error rate **RNA polymerases CANNOT proofread** -NO known RNA repair mechanism is known Therefore: RNA viruses produce more variants per replication cycle than DNA viruses **Coronavirus RNA polymerase can proofread!

Answer 50

We want antiviral drugs to INHIBIT viral replication -If the virus makes and requires its own enzymes (such as an RNA-dependent DNA polymerase), then drugs against those enzymes may be effective treatments -However, if virus uses the host cell enzymes to replicate, then drugs against those enzymes will be toxic to host cells as well

Answer 51

Maturation: nucleic acids and capsids are assembled into complete virions--usualy spontaneous

Answer 52

Release of virus: -many viruses lyse the host cell -also budding of an enveloped virus occur (budding does NOT result in host cell lysis) (the surface of HIV is an envelope taken from the host cell plasma membrane)

Answer 53

Some animal viruses integrate Into the genome (but not at specific sites) -DNA from dsDNA (double-stranded) viruses normally enters the nucleus, circularizes, but does NOT integrate into the genome -Some DNA viruses will integrate on rare occasions. -Herpesviridae can resist and establish Latency without integration. However, certain herepsviridae do integrate at Low frequencies -In many cervical cancers, the Human Papilloma virus (HPV), genome has been found integrated into the host cell genome, where certain viral proteins remain expressed and active. -Retroviridae REQUIRES genome integration for its normal life cycle

Answer 54

Conditional integration: Lambda (and certain other bacteriophages) have specialized mechanisms that allow them to integrate at SPECIFIC locations in the bacterial genome if the conditions are right

Answer 55

Certain viruses cause latent or persistent infections *Latent infection: the virus remains asymptomatic in the host cell for LONG periods (often years) -cold sores/fever blister (Herpes simplex virus)- inhabits nerve cells but cause No damage until activated (fevers or sunburn) -fifty to 80 percent of US adults have oral herpes (HSV-1) -Shingles (varicella zoster virus)- following Chickenpox, some virus enters nerve cells and remains latent. Later in life, changes in T-cell response can activate the virus producing the shingles rash along nerve where the virus was latent *Persistent infection: Disease processes occurs over a Long period of time and is often FATAL ex: subacute sclerosing panencephailts- rare progressive neurological disorder in children and young adults caused by measles virus

Answer 56

Growth curves persistent infection: Continuous, low-level virus production Latent infection: No symptoms or virus produced for a long time

Answer 57

Examples of Latent infections: Virus: *Herpes simplex 1 and 2 causes cold sores (disease) and virus effect: lesions in skin and mucosa *HTLV-1 and 2 (retroviruses) will cause Leukemia (disease) and virus effect: increased white blood cell growth *Varicella zoster virus (herpesvirus) cause Shingles (disease); virus effect: skin lesions

Answer 58

Examples of persistent infections Virus: -Human papilloma virus (HPV) (papovirus) causes cervical cancer (disease); virus infect: increased cell growth -HIV-1 and 2 (retrovirus) causes HIV/AIDS (disease) and virus effect: Decreased CD4+ T cells -Hepatitis B virus (hepadnavirus) cause Liver cancer (disease) and virus effect; increased cell growth -Rubella virus (togavirus) causes progressive encephalitis (disease); virus effect: rapid mental deterioration -measles virus (paramyxovirus) causes subacute sclerosing panencephalitis (SSPE) (Disease) and virus effect; mental deterioration

Answer 59

Growing viruses in the laboratory Viruses must be grown in living cells -Bacteria for bacteriophages -fungi for fungi viruses -animals, animal tissues, or cultured animal cells (where the virus is grown) for animal viruses -plants or cultured plant cell for plant viruses

Answer 60

Detection and Quantitation of bacteriophage by plaque method -Bacteriophages can be grown either in suspensions of bacterial in liquid or solid media - The concentration of a viral solution is usually expressed in terms of plaque-forming units (PFU)/ml process; 1. mixture of unaffected bacterial cells and single layer of phage-infected cell are in melted agar 2. solidification of top agar layer immobilizes cells 3. Phage replicate in the infected cell. The cell lyses, releasing progeny that infect adjacent cells. These cells lyse and the cycle repeats -Growth of uninfected bacteria creates an opaque lawn except at the location of original infected cell, where there is a plaque (hole) containing millions of phage

Answer 61

Depending on the virus, the plaques are either clear or cloudy/turbid. phenotype: Cloudy plaque: no cells in the hole (temperate phase) Clear: some cells have been lysed (lytic phase)

Answer 62

bacteriophage plaques -a phage causes plaques (clearings) in lawn of bacteria. Each plaque was started by a single virus infection that spread to surrounding cells over time.

Answer 63

Animal and plant cell cult can be used for viruses growth Cell culture: cells grown in culture media in the lab process: 1. tissue is treated with enzymes to separate the cells 2. Cells are suspended in culture medium 3. Normal cells or primary cells grow in a Monolayer across glass or plastic container. The transformed cells or continuous cell cultures Do NOT grow in a monolayer. ** transformed cells are also called cell lines or immortalized cells (both transformed and normal cells are used to grow viruses in lab)

Answer 64

Primary cells (normal cells) are derived from NORMAL tissues and have LIMITED growth capacity -Cell lines (aka Transformed cells) are derived from Cancers and other abnormal tissues, but have UNLIMITED growth capacity (there are more than 650 human cell lines)

Answer 65

Cell lines examples: A-5449: lung carcinoma MCF10A : mammary gland HL-60 (myeloblast) HEK (embryonic kidney )

Answer 66

The most widely used human cell line is HeLa HeLa cells have been used to study many viruses and have been critical to may scientific breakthroughs (He La cells are easy to grow) (He la cells- one of first immortalized cells used in cancer research)

Answer 67

Cytopathic effect (CPE) -many virus infections produce a cytopathic effect, characterized by round, swelling, detaching and dying of infected cells -CPE can be detected and counted in a way similar to plaques on a lawn of bacteria and reported as PFU/ml (PFU: plaque forming units) -used as plaque assay

Answer 68

Cultured mammalian cells can be used for plaque assays -each plaque was started by a single virus infection that spread to surrounding cells over time The cells are stained with a blue dye that stains only live cells

Answer 69

The GROWTH of Viruses used in embryonate chicken eggs -once the most widely used method of isolating and growing virus -Most influenza vaccine is made in chicken eggs each year (in order for virus to effectively infect cells, they need to be injected into the right compartment of eggs) (yolk sac, amniotic cavity, allatonic cavity, or choriallatonic membrane)

Answer 70

Animal hosts for human viruses *some human pathogenic viruses can only be grown in animals. Scientists exhaust all other ways of trying to grow a virus before using such animals in research - Mammals including mice, rhesus macaque monkeys and chimpanzees

Answer 71

Some human viruses can't grow in animals, or some can grow, BUT don't cause disease -Although chimpanzees can be infected with one of the two subspecies of HIV (HIV-1) , they are asymptomatic for the disease, and CANNOT be used to study effects of viral growth and disease treatments -Simian AIDs (monkey) and feline AIDs develop disease within a few months and closely related to human AIDs. Thus provide models for studying AIDS. -AIDS vaccines are tested in humans but can take years to determine effectiveness, because the disease progresses so slowly

Answer 72

Virus identification (Not east to visualize) *Observation of cytopathic effects (ex: cell shape, chromosome, or specific protein level changes, inclusion bodies, cell fusion ) *Viral culture: samples of a virus are added to different cell lines and tested for their ability to infect *Serological tests -viral hemagglutination test (mix virus with blood to see if wit will agglutinate) -*Use ANTIBODIES from a patient's serum against a panel of known viruses to identify the infecting virus (western blot or neutralization test) *Nucleic acids -PCR -Sequencing (isolate DNA or nucleic acid and sequence it) -RFLP- restriction fragment l linear polymorphism (digesting DNA)

Answer 73

Infected host cells (eukaryotic or prokaryotic) can be cultured and grown, then the growth medium can be harvested as a source of virus. Viruses can be purified away from cellular proteins and organelles using centrifugation techniques

Answer 74

Host range (host tropism) the range of different species a virus can infect Tissue tropism : the types of different tissues in an individual a virus can infect

Answer 75

*specific host attachment sites -due to differences in surface proteins *Intracellular factors, such as host enzymes and antiviral defenses -restriction to virus tropism are not just at the surface of the cell, but can occur at virtually any step of virus replication, maturation, and release form the cell

Answer 76

tropism: what the virus is able infect cellular tropism : type of cell in which a virus can infect ex; HIV normally infects m macrophages but not neurons tissue tropism: the types of tissues in an individual that a virus can infect ex; Influenza virus normally infects lung tissue but not brain tissue Host range ; aka host tropism describes the range of species that a virus can infect ex: myxoma virus normally infects rabbits, but Not humans -A virus's tropism is strictly limited. it changes on evolutionary time scale

Answer 77

Different HA proteins of influenza A virus bind different forms of sialic acid binding sites for influenza hemagglutinin protein -alpha 2, 6 linkages in human influenza -alpha, 2, 3 linkages in Avian and some swine flu influenza (changes in hemaglutinin protein recognize different linkages)

Answer 78

Influenza virus tropism -Different HA proteins of influenza A virus bind different forms of sialic acid present in different places in each animal's body

Answer 79

Influenza viruses have a BROAD host range. it can affect multiple species -Poliovirus by contrast, has a Narrow host range of one species

Answer 80

Human influenza A viruses cause seasonal epidemics of disease (know as flu season) almost every winter in the US -Influenza virus are classified by their HA and NA proteins HA---> Hemmmaglutinin NA---> neuraminidase -there are 17 different HA subtypes and 10 different NA subtypes -Only three known subtypes of Human influenza virus: H1N1, H1N2, H3N2

Answer 81

Model for antigenic shift in influenza virus -Influenza A viruses are found in many different animals. sometimes viruses seen in one species can cross over and cause illness in another (ex: human virus genes and avian virus genes can mix with swine virus genes to make triple reassortment ) -the 8 segments of the -RNA genome allows virus genes to mix and create a new influenza A virus, if viruses from two different species infect the same species. -This virus will hav a mixture of the H an N antigens. This is known an antigenic shift. Term is applied specifically to influenza -The 2009 H1N1 influenza virus was a quadruple reassortment virus: genes from flu viruses that circulated in European pigs, asian pigs, avian and human genes -A new vaccine for flu must be made every year because new variants appear every year.

Answer 82

Importance of virus surface proteins; -The virus surface proteins determine what *Cell surface receptors the virus binds* -Whichever cells express the surface receptors determines TISSUE TROPISM, thus pathology (the tissue virus infects) -Variation in the cell surface receptors determine the determine the *host range*, that is what species can be infected. -Variations in virus surface proteins determine the effectiveness of the *host immune response*

Answer 83

-immunity to one virus strain may confer immunity to another similar strain, but may NoT to a more distally-related virus. -The virus mutates to vary its surface proteins a little, to evade immune response -But viruses evolve to use different receptors, very, very slowly only on an evolutionary time scale

Answer 84

Oncogene: a gene that has the potential to cause cancer Most oncogenes begin as protoncogenes Proto-oncogenes: normal genes that undergo cell division and apoptosis (inhibit apoptosis?) The genetic material of oncogenic viruses become integrated into the host cell's DNA oncogenic viruses of humans are usually DNA viruses

Answer 85

Transformed cells acquire properties distinct from uninfected cells: increased growth, loss of contact inhibition, host-encoded tumor specific transplant antigens and (TSTA) on their cell surface and viral-encoded T-antigens

Answer 86

Tumor specific transplant antigens : (TSTA): a protein that is found only on cancer cells and NOT normal cells; these antigens can help body make an immune response against cancer cells. T- antigens: protein that is produced by tumorigenic DNA viruses and that will transform normal cells into tumor cells

Answer 87

Activation of an oncogene by a retrovirus provirus -during evolution, a retrovirus provirus might have integrated next to a host gene involved in cell growth control. if the virus activates that gene, it would become an oncogene capable of driving the formation of cancer Thus, in the distant past these viruses have "picked up" oncogenes and now carry them other cells to cause cancer.

Answer 88

Oncogenic DNA viruses: carry genes unrelated to host that inactivate tumor suppressor genes ex: -Herpesviridae -EBV (epstein Barr virus) -Papovaridiae -HPV (human papillomavirus) -Hepadnaviridiae - HBV (Hepatitis B virus) Oncogenic RNA viruses; carry "TRUE" oncogenes related to host genes -several examples in animals, but rare in humans -Retroviruses -HTLV-1 -HTLV-2

Answer 89

Only about 12% of human cancers are attributable to viruses -The most common virus-associated cancers are: *Cervical cancer (human papillomavirus, HPV) -HPV types 16 and 18 cause 70% of cervical cancers *Liver cancer (hepatitis B virus, Hepatitis C virus) ALL of these are preventable with VACCINATION -Girls and boys, age 11-26, should be vaccinated with a vaccine against four HPV serotypes, including HPV16.

Answer 90

Viroids: NOT viruses -***ONLY in Plants *** -short (300- 400 nucleotides) -naked, infectious RNA - 3-dimensional structure may protect it form cellular enzyme destruction -encodes NO proteins and may cause disease by gene silencing -May have evolved from introns -replicated continuously by host RNA polymerase by rolling circle replication in the nucleus or chloroplast. They cut into viroid segments by viral RNA (act as ribozyme)

Answer 91

Virusoid: a viroid enclosed in a protein coat

Answer 92

The only thing similar is Hepatitis Delta (NOT virusoid)

Answer 93

virus- can infect any cell, and have a protein coat called capsid (surrounds genetic material; DNA or RNA) -Viroid is smaller than virus and does NOT have protein coat (naked single stranded RNA strand) , and only infect plants virusoid: a viroid (single stranded, RNA) enclosed in protein coat Prions are smaller than viroids and only composed of protein molecules

Answer 94

Hepatitis D (delta) virus is aka Satellite Virus -Delta is a -RNA circle that makes one protein; the Delta antigen. It makes NO capsid. It requires co-infection with Hepatitis B; it is packaged and carried in the HBV particle (it can only infect people who are also affected with hepatitis B virus) (can be seen as virusoid?)

Answer 95

Prions: Proteinaceous Infectious particles -inherited and transmissible by ingestion, transplant, and surgical instruments -Cause Spongiform encephalopathies: sheep scrapie, Creutzfedldt-Jakob disease, Gerstmann-Strausslaer-Scheinker syndrome, fatal familial insomnia, mad cow disease *Prions resemble viruses epidemiologically, but NOT viruses molecularly* (prions are abnormally mifolded shaped proteins that can transmit their misfolded shape onto normal proteins and cause disease (prions can withstand autoclaving, and are extremely stable proteins)

Answer 96

Two forms of prion protein: PrP^C : prion protein --> "cellular" normal (composed of alpha helices) PrP^Sc : prion protein---> "scrapie" infectious (misfolded form composed of beta sheets)

Answer 97

PrP^Sc forms fibrils: stacks of tightly bound proteins -The fibrils cause neurological damage in the brain

Answer 98

How a protein can be infectious: 1. PrP^c (normal protein) produced by cells is secreted to the surface 2. PrP^Sc may be acquired or produced by an altered PrP^c gene 3. PrP^Sc reacts with PrP^c on the cell surface 4. PrP^Sc converted the PrP^c into PrP^Sc 5. The new PrP^Sc converts more PrP^c 6. The new PrP^Sc is taken in by endocytosis 7. PrP^Sc accumulates in endosomes 8. Prp^Sc continues to accumulate as the endoscope contents are transferred to the lysosomes. the result is cell death

Answer 99

Family: poxiviridae part of class I **SMALLPOX Virus*** (enveloped, large virus)

Answer 100

Herpesviridae -part of Class I ***Varicella Zoster Virus**

Answer 101

Papoviridae: part of Class I ***Human Papilloma Virus (HPV) ***

Answer 102

Coronaviridae Class IV **SARS-COV-2 *(SARS, MERS ) causes disease COVID-19

Answer 103

Picornaviridae: Class IV ***POLIOVIRUS***

Answer 104

Filoviridae Class V ***Ebola**

Answer 105

Paramyxoviridae Class V **Measles***

Answer 106

Orthomyxoviridae Class V ***Influenza Virus**

Answer 107

Retroviridae Class VI *** HIV**** (causes disease AIDS)

Answer 108

Hepadnaviridae Class VII *** Hepatitis B Virus***

Answer 109

Class I: all are double stranded DNA Class II: single stranded DNA (for family parvoviridae) Class III: double stranded RNA (family reoviridae) Class IV; all are + RNA and have polyhedral virion structure Class V: all are -RNA, have envelopes and all are helical virion structure Class VI: are + RNA for (family retroviridae--> HIV) Class VII: gapped ds DNA (fmily hepadnaviridae---> Heaptits B virus)

Viruses, Viroids and Prions Flashcards

(134 cards)