Viral Pathogens: Classification, Biology, Diseases II

Question 1

Describe the typical course of HIV-1 infection

Answer 1

• Primary infection - the point at which there is initial HIV infection
• Acute HIV infection - Wide distribution of virus, Seeding of lymphoid organs
• Clinical Latency- period where there is no increase in HIV population
• Onset of symptoms- so few T cells that HIV replication begins again
• Opportunistic infections - Other infection take advantage of the immunosuppressed patient

Question 2

What is the set point viral load

Answer 2

• The number of HIV particle that exist over time in the clinical latency period

Question 3

Why doe HIV want to replicate in T cells

Answer 3

Viruses must evade immune responses.

Replication in immune cells hides the virus from immune cells and inhibits immune cell function.

Question 4

Describe HIV infection in Non-permissive CD4 T-Cells

Answer 4

Non-permissive cells are normally non-replicative cells 95% of cells

• Fusion
• Impaired reverse Transcription
• Accumulation of Incomplete Reverse Transcripts
• Detection by IFI16 DNA sensor
• Activation of innate antiviral and inflammatory responses
• IFI16 Inflammasome assemble
• Cascade-1 activation
• Pyroptosis

Death of abortively infected CD4 T cell

Question 5

Describe HIV infection in Permissive CD4 T-Cells

Answer 5

5% of cells

• Fusion
• Processive reverse transcription
• Evading host detection
• Infection of CD4 T cell
• Caspase-3 activation
• Apoptosis

Death of Productively infected CD4 T cell

Question 6

Describe the initiation of pathogenesis in HIV infection

Answer 6

• HIV infection
• Release of pro-inflammatory cytokines and cellular contents
• Inflammation
• recruitment of healthy CD4 T cells

Question 7

Describe chronic inflammation and pathogenesis in HIV infection

Answer 7

• Migration of neutrophils and monocytes in the tissue
• Cell death and release of pro-inflammatory cytokines and cellular contents
• Inflammation

Question 8

List some HIV associated pathogens

Answer 8

Virus:

• Herpes simplex virus (HSV)
• Kaposi’s sarcoma herpesvirus (KSHV)

Bacteria:

• Mycobacterium tuberculosis
• Salmonella

Fungus:

• Candida
• Cryptococcus neoformans

Parasite:

• Cryptosporidium
• Toxoplasma gondii

Question 9

What are the two possible routes of infection

Answer 9

• Primary infection
• Reactivation from latency

Question 10

Why does the Herpes virus select dendrites as its host

Answer 10

It is difficult to mount an immune response in neural tissue

The virus can stay in the CNS and only leaves and replicates when T-cell count is low due to HIV

Question 11

Describe Asymptomatic KSHV infection in a healthy individual

Answer 11

• KS Progenitors undergo de novo infections
• Can turn into latent epithelial cells which are not transformed
• Reactivation makes it latent and early lytic, oncogenic and immunogenic
• Further development makes it productive, cytopathic and immunogenic
• Causes reinfection into other cells

Question 12

Describe Viral oncogenesis of AIDS-Kaposi’s Sarcoma