Viral pathogens: classification, biology, diseases II

Question 1

Describe the ‘typical’ course of HIV-1 infection? VD

Answer 1

• HIV targets CD4+ T cells -> primary infection -> Acute HIV infection (peak) ->
• Decrease in viral load - clinical latency (Active HIV, no symptoms) + set point viral load (minimum HIV particles without triggering immunity -> Increased viral load - onset of symptoms + opportunistic infections -> depletion of CD4 T cells -> Immunodeficiency (AIDS) + mortality
• Course of infection -> Decrease in CD4+ T cells + increase viral RNA

Question 2

What is the viral load and what does it indicate?

Answer 2

• Number of viral RNA genomes/ml blood
• Determined by RT-PCR

Question 3

State the pathways of killing from HIV?

Answer 3

• Non-permissive CD4 T cells (95%) -> cells prevent HIV recognition -> Caspase-1 activation -> pyroptosis (cell death)
• Permissive CD4 T cells (5%) -> caspase-3 activation -> apoptosis

Question 4

Describe the pathogenesis cycle of HIV?

Answer 4

HIV infection -> Pyroptosis (CD4 death) - release of pro-IF cytokines - >IF -> Recruitment of healthy CD4 (HIV infected eventually) -> Migration of neutrophils + monocytes into tissue -> cell death + release of pro-IF cytokines

Question 5

Describe what the effect of inhibiting immune cell function via viruses allow?

Answer 5

• Replication of other pathogens in virus infected hosts
• Causes disease
• Known as opportunistic infection of HIV associated pathogen

Question 6

State 4 types of HIV associated pathogens with 2 examples of each?

Answer 6

• Virus: herpes simplex virus, kaposi’s sarcoma herpes virus
• Bacteria: mycobacterium tuberculosis, salmonella
• Fungus: candida, cryptoccus neoformans
• Parasite: cryptosporidium, toxoplasma gondii

Question 7

State the 2 possible routes of infection for cancers + opportunistic infections from AIDS?

Answer 7

• Primary infection -> resolved via immune suppression -> infection moves to site that IS can’t access -> virus resides without replicating -> latency
• Reactivation from latency -> depends upon immunodeficiency

Question 8

State viruses which cause the following cancer: skin cancer, lymphoma, carcinoma?

Answer 8

• Skin cancer: Human papilloma virus
• Lymphoma: EBV. HHV-8, Human T-lymphotrophic virus-1 (+ leukemia)
• Carcinoma: HBC, HCV, Merkel cell polyomavirus