Viral Pathogens: Classification, Biology, Diseases - II

Question 1

“Typical” course of HIV-1 infection

Answer 1

In a typical untreated patient, ten billion virions are made and destroyed every day during the chronic phase of disease

The inexorable depletion of CD4 T cells during infection ultimately leads to immunodeficiency (AIDS) and mortality (via opportunistic infections)

Question 2

Explain the specific type of replication needed in viruses

Answer 2

Viruses must evade immune responses. Some immune responses are mediated by specific cells of the immune system. These immune cells recognize and kill cells infected by virus.

To evade this type of immune response, some viruses replicate in the immune cells whose function is to recognize and kill infected cells.

Question 3

Explain the advantage of the specific type of replication is needed in viruses

Answer 3

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

Inhibition of immune cell function allows other pathogens to replicate in virus infected hosts and, thus, disease occurs.

Question 4

HIV associated viruses - list

Answer 4

Virus:

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

Question 5

HIV associated bacterium - list

Answer 5

Bacteria:

Mycobacterium tuberculosis
Salmonella

Question 6

HIV associated fungi - list

Answer 6

Fungus:

Candida
Cryptococcus neoformans

Question 7

HIV associated parasites - list

Answer 7

Parasite:

Cryptosporidium
Toxoplasma gondii

Question 8

AIDS : Cancers and Opportunistic Infections - describe both possible routes of infection

Answer 8

Two possible routes of infection (i) primary infection
(ii) reactivation from latency

Primary infection can be resolved (typically by immune suppression) and infection moves to sites in the host that the immune system does not access. In these sites the virus resides without replicating: latency

Reactivation from latency occurs upon immunodeficiency

Question 9

List 7 viruses that cause cancer

Answer 9

Human papilloma viruses (HPVs) – Papilloma virus, circular dsDNA genome, skin cancer

Epstein-Barr virus (EBV) – Herpes virus, linear dsDNA genome, lymphoma

Hepatitis B virus (HBV) – Hepadnavirus, circular dsDNA genome, carcinoma

Hepatitis C virus (HCV) – Flavivirus, ssRNA genome, carcinoma

Human herpes virus 8 (HHV-8) - Herpes virus, linear dsDNA genome, lymphoma

Human T-lymphotrophic virus-1 (HTLV-1) – Retrovirus, RNA-DNA genome, leukemia/ lymphoma

Merkel cell polyomavirus (MCV) – Polyomavirus, dsDNA genome, carcinoma