Dr. Rajendran Rajendran

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HIV - virology (30 MCQs)

2) The master regulator of the immune system

a. Pituitary gland

b. CD4+ T cells

c. CD8+ T cells


e. Neutrophils

Ans: (b)

The CD4+ T cell is the master regulator. CD4+ T cells secrete cytokines. By secreting cytokines, CD4+ T cells influence the function of virtually all other cells of the immune system, including other T cells, B cells, macrophages, and NK cells. The HIV cripples the immune system by destroying CD4+ T cells.

CD8+ T cells function mainly as cytotoxic cells to kill other cells.

3) The genetic information of the HIV is encoded by

a. DNA

b. RNA

c. Both

d. Neither

Ans: (b)

A central belief of molecular biology is that information passes unidirectionally from DNA to RNA to protein. The retroviruses are called so because RNA, rather than DNA, encodes their genetic information. Retroviruses contain an RNA-dependent DNA polymerase (a reverse transcriptase) that directs the synthesis of a DNA form of the viral genome from the RNA.

4) Most common cause of HIV disease throughout the world

a. Transforming retroviruses

b. HIV-1

c. HIV-2

d. HIV - 3

Ans: (b)

There are four human retroviruses: the transforming retroviruses (human T lymphotropic viruses - HTLV 1 and HTLV 2) and cytopathic viruses (HIV-1 and HIV-2). HIV-1 infection in humans originated from chimpanzees and/or gorillas, and HIV-2 from sooty mangabeys.

HIV was isolated by Luc Montagnier from Pasteur institute, Paris (1983) and by Robert Gallo (1984). The most common type is HIV-1. It is a 90 to 120 nm sized single stranded RNA virus. HIV-1 is more pathogenic than HIV-2. The subtype C is prevalent in India.

HIV-1 viruses likely came from chimpanzees

5) Which group is responsible for most of the infections in the world?

a. M

b. O

c. N

d. Circulating recombinant forms

Ans: (a)

There are two groups of HIV-1. Group M (major) is responsible for most of the infections in the world.
Group O (outlier) is a relatively rare form found originally in Cameroon, Gabon, and France. There is a third group (group N) first identified in a Cameroonian woman with AIDS.

The M group comprises eight subtypes or clades, designated A, B, C, D, F, G, H, and J, as well as four major circulating recombinant forms (CRFs). Subtype C viruses (of the M group) are the most common form worldwide. Subtype C is prevalent in India.