Virus Intro

Question 1

Virus Outline

Answer 1

Infectious agent in a protein coat. Contain either DNA or RNA (either double/single strands). Strict intracellular parasites (need host cellfor replication) (different from bacteria who reproduce without host cell). Non-living entities

Question 2

How viruses are classified

Answer 2

Morphology (shape), nucleic acid, replication mechanism, type of host they infect and disease that they cause

Question 3

Virus Components

Answer 3

Capsid (protein capsomere coat), nucleic acid (DNA/RNA) (joins with capsid to form nucleocapsid) and occasionally envelope (sourced from host cell)

Question 4

Capsid Overview

Answer 4

Protective shield made up of different capsomer shapes. Contains antigens for interaction with host cell receptors to implement it’s DNA into host cell

Question 5

Capsid Shapes

Answer 5

cubic/icosahedral, helical and complex

Question 6

Cubic Capsids Outline

Answer 6

20 equilateral triangle faces. Eg adenovirus

Question 7

Helical Capsids Outline

Answer 7

protein bound around nucleic acid as helix

Question 8

Complex Capsid Outline

Answer 8

Neither cubic or helical. Eg poxvirus. Includes bacteriophage which includes separate capsid heads and tails

Question 9

Capsid Ressistance

Answer 9

Drying, heating, detergents, acids and proteases. This enables it’s survival on surfaces and in the GI tract

Question 10

Viral Genome

Answer 10

Circular/ linear single/doble stranded DNA/RNA molecules. Codes for host production of viral proteins and replication enzymes

Question 11

Production of mRNA in human DNA viruses

Answer 11

Can have either single/double strand DNA.single strand DNA becomes double strand DNA. Double strand DNA forms mRNA

Question 12

Production of mRNA in RNA viruses

Answer 12

Can have either

Question 13

Viral Envelope Outline

Answer 13

Lipid bilayer that surrounds capsid. Consists of phospholipids and glycoproteins (that acts a s receptors). Derives from host cell’s membrane (via budding)

Question 14

Distinctive Serological Polypeptides of Envelopes

Answer 14

Surface polypeptides (eg influenza hemagglutinins), antigens and enzymes (eg influenza neuraminidase)

Question 15

Envelope is sensitive to

Answer 15

Drying, heat, detergents and acids. Thus viruuses with envelope must have moist transitions (droplets), can’t survive GIT, may need cellular and humoral (antibodies, antimicrobials, ect.) to be treated

Question 16

How viruses are acquired

Answer 16

Vectors (animal/insect bites eg rabies), inhalation (eg influenza), faecal oral (contaminated water eg hepatitis A & E), blood (eg HIV), sexual (eg herpes) and congenital (when born eg rubella)

Question 17

Virus Cell Tropism

Answer 17

The affinity a virus has for host cells. Determined by cell receptors, physical barriers, temp, pH and oxygen tension enzymes

Question 18

Virus Replication Outline

Answer 18

virus attachment and entry to cell, virion uncoating, genomic nucleic acid migrates to nucleus, transcription, genome replication, viral mRNA translation, viron aseembly and release of new viruses

Question 19

How do viruses attach to cell

Answer 19

Viral attachment, Glycoprotein to cell receptor. If compatible virus undergoes endocytosis

Question 20

Why do viruses need to uncoat

Answer 20

Make genome available pushes viral nucleic acid into cytoplasm

Question 21

Location of viral nucleic acid synthesis in host cell

Answer 21

cytoplasm and nucleus

Question 22

Location of viral protein synthesis in host cell

Answer 22

cytoplasm

Question 23

How viruses leave host cells

Answer 23

enveloped: budding. Non-enveloped: lysis or exocytosis

Question 24

Viraemia Def

Answer 24

Virus enetring into blood

Question 25

Cytopathological Activity Def

Answer 25

Impact virus has on host tissue (damage)

Question 26

Immunopathology Def

Answer 26

What response a pathogen (virus) stimulates (if any eg HIV hiding in body cells)

Question 27

Virus effects on cells

Answer 27

death, transformation and latent infection

Question 28

Cell Death Outline

Answer 28

Cytopathogenic effect visible on cell

Question 29

Cell transformation Outline

Answer 29

Cell becomes malignant or pre-malignant (cancerous) eg pampillivirus

Question 30

Latent Infection Outline

Answer 30

Viral parts may be only temporarily inactive

Question 31

What is looked at under electron microiscope

Answer 31

Quick observation of virus

Question 32

What is looked at under fluorescent microscope

Answer 32

Detection of viral antigens using antibodies (fluroscing antibodies)

Question 33

What is looked under a light microscope

Answer 33

virus induced masses in cells. can be pathogonomic

Question 34

Virus Cause of Lymphoma

Answer 34

HIV and Hespatin & Barr virus

Question 35

Virus Cause Hepatocellular cancer

Answer 35

Hepatitis B and C

Question 36

Cervical Cancer

Answer 36

papillomavirus

Question 37

Nasopharyngeal Cancer Virus cause

Answer 37

EBV

Question 38

Ways viruses spraed

Answer 38

Intracellular (cell to cell intercellular bridges), extracellular ( in hematogenous and lymphatic cells they travel in blood), neural (peripheral nerves to CNS) and nuclear (genome continues in host cell)

Question 39

Viral infection Outcomes

Answer 39

In most patients viruses are self limiting (can resolve without treatment) but in immunocompromised individuals it can be more severe to fatal. Can be silent (asymptomatic), can reoccur intermittently (can be dormant for a time). Viral effects can be acute (happening now for a limited time) or chronic (permanent changes)

Question 40

Classifications of antivirals

Answer 40

Deactivating virus (UV, cryotherapy) , Augmentation of host cell (eg intereferons) and viral replication inhibition (eg Aciclovir), vaccinations (eg influenza, HPV)

Question 41

Lab Infection Diagnosis

Answer 41

Qualitative (detection and ID) and quantitative (amount of virus)

Question 42

Examples of detection and ID of viruses

Answer 42

Microscopy, viral culture, serology (viral antibody), viral antigen and viral genome

Question 43

Viral Culture Outline

Answer 43

Animal (host) cells are grown in an artificial culture. Cells are observed for changes specific to particular viral infection. Confirm viral ID by immunofluorescence, neutralisation and haemabsorption inhibition

Question 44

Viral cell culture disadvantages

Answer 44

Most viruses won't grow (eg hepatitis B), susptible to bacterial infection, culture can be damaged by viral waste, poor sesitivity and long wait time

Question 45

How is blood analysed to test for viral antigen

Answer 45

2 samples required: 1 from day of illnes onset and 1 1-2 weeks later. If blood shows a rise in antibodies antigen is present. Tested via ELISA or fluroescent microscopy

Question 46

Molecular Diagnosis eg PCR Outline

Answer 46

rapid diagnosis, used to guide traement plans and detect antiviral ressistance. Not all viruses can be cultured eg hepatitis C