HIV

Question 1

What family of viruses does HIV belong to?

Answer 1

Retroviruses.

Question 2

What is the defining feature of retroviruses?

Answer 2

They reverse-transcribe RNA → DNA and integrate into the host genome.

Question 3

Which retrovirus subgroup includes HIV-1 and HIV-2?

Answer 3

Lentiviruses.

Question 4

What percentage of the human genome is made of endogenous retroviruses (HERVs)?

Answer 4

~8%.

Question 5

What useful human function is derived from a HERV gene?

Answer 5

Syncytin, important for placental development.

Question 6

How many people are infected with HIV-1 globally?

Answer 6

~39 million.

Question 7

What was the number of HIV deaths globally in 2021?

Answer 7

~650,000.

Question 8

From which primate viruses did HIV originate?

Answer 8

SIVs (Simian Immunodeficiency Viruses).

Question 9

Which SIV gave rise to HIV-1?

Answer 9

SIVcpz (chimpanzee) and SIVgor (gorilla).

Question 10

Which HIV-1 group is responsible for the global pandemic?

Answer 10

Group M.

Question 11

Which SIV gave rise to HIV-2?

Answer 11

SIVsmm (sooty mangabey).

Question 12

Why did HIV spread globally during the 20th century?

Answer 12

Colonization-era transport, unsterile medical practices, urbanization, global travel.

Question 13

Which host receptor does HIV bind first?

Answer 13

CD4 receptor.

Question 14

Which co-receptor is primarily used for entry?

Answer 14

CCR5 (or CXCR4 later in infection).

Question 15

Why does budding give HIV an envelope similar to the host cell membrane?

Answer 15

The virus buds directly out of the plasma membrane.

Question 16

What enzyme converts HIV RNA → DNA?

Answer 16

Reverse transcriptase.

Question 17

What enzyme inserts HIV DNA into host DNA?

Answer 17

Integrase.

Question 18

What enzyme cleaves viral polyproteins during maturation?

Answer 18

Viral protease.

Question 19

Which immune cells can HIV infect besides T-helper cells?

Answer 19

Dendritic cells, macrophages, microglia, astrocytes.

Question 20

What role do dendritic cells play in early HIV spread?

Answer 20

They capture virus and carry it to lymph nodes, enabling systemic spread.

Question 21

What are the phases of HIV infection?

Answer 21

Acute infection → clinical latency → AIDS.

Question 22

What happens during acute HIV syndrome (2–4 weeks)?

Answer 22

Flu-like illness, high viral load, drop in CD4 cells.

Question 23

What defines AIDS?

Answer 23

(1) HIV-1 infection + (2) CD4 < 200 cells/µL + (3) opportunistic infections.

Question 24

Why do CD4 cells decline over time in HIV infection?

Answer 24

Chronic immune activation → high turnover → immune exhaustion.

Question 25

What genetic mutation protects some individuals from HIV progression?

Answer 25

CCR5-Δ32 truncation → virus cannot attach.

Question 26

Why does ART not cure HIV?

Answer 26

Integrated viral DNA remains in host genome; stopping ART → viral rebound.

Question 27

Effectiveness of PrEP?

Answer 27

74–99%.

Question 28

Effectiveness of PEP?

Answer 28

81–99.5%.

Question 29

Why is developing an HIV vaccine difficult?

Answer 29

Rapid replication, huge genetic diversity, and lack of good animal models.