Many scientists and drug companies have worked hard to produce drugs to stop various stages of the HIV life cycle. Some drugs have been tested that inhibit the function of Vpu. What stage of the HIV life cycle would such a drug inhibit?

A. Synthesis of double stranded DNA
B. Virus assembly
C. Virus budding
D. Integration into the host chromosome
E. Viral RNA exit from the nucleus

Option A. Synthesis of double stranded DNA

Explanation:

HIV is Human Immunodeficiency Virus, that acts by targeting the immune system of humans. Antiretroviral drugs target different 'HIV lifecycle' stages to stop replication of HIV.

HIV can not reproduce by itself, so it must infect cells of the human immune system, called CD4 cells, to make new copies of itself. CD4 cells are white blood cells which play a central role in the body's response to infections. Over time, HIV destroys CD4 cells, and the ability of the body to identify and fight other forms of infection starts to weaken. When therapy does not control HIV, the loss of CD4 cells contributes to the development of serious diseases or 'opportunistic infections.' These infections should be recognised and cleared by the immune system in people with normal levels of CD4 cells.

As HIV RNA enters the cell, it needs to be 'reversed' into proviral DNA before it can be incorporated into the host cell's DNA. Reverse transcriptase enzyme of HIV turn the RNA within the cell into a proviral DNA.

Two types of antiretroviral drugs that involves nucleoside and nucleotide reverse transcriptase inhibitors (NRTIs and NtRTIs), were designed to stop the reverse transcriptase activity and the development of proviral DNA. HIV production is inhibited by NRTIs and NtRTIs by adding a nucleoside or nucleotide into the HIV DNA chain as it is established to end the chain.  

Non-nucleoside reverse transcriptase inhibitors (NNRTIs), by binding directly to the reverse transcriptase enzyme, block HIV development. Hence the drug inhibit the synthesis of double stranded DNA.

Hence, the correct option is A.

C. Virus budding

Explanation:

The Vpu protein helps in moving the viral cells out from the host cell.

Budding enables viruses to exit the host cell and is mostly used by enveloped viruses which must acquire a host-derived membrane enriched in viral proteins to form their external envelope.

answer; both surfaces of the membrane are nonpermeable