Which antiviral agent is used for the treatment of HIV?

Zidovudine, also known as AZT, is an antiviral medication that is specifically used for the treatment of HIV (Human Immunodeficiency Virus). It belongs to a class of drugs called nucleoside reverse transcriptase inhibitors (NRTIs). These drugs work by interfering with the reverse transcriptase enzyme that HIV needs to replicate its viral RNA into DNA, thus inhibiting the virus's ability to reproduce and reduce the viral load in the patient’s body.

By reducing the HIV viral load, Zidovudine helps to improve the immune response and quality of life in individuals living with HIV. It may also be used in combination with other antiretroviral agents as part of a comprehensive treatment regimen to effectively manage the infection.

Other options like Amphotericin B are antifungals used primarily to treat fungal infections, Oseltamivir is an antiviral drug used to treat influenza, and Acyclovir is used for herpes simplex virus infections. None of these are indicated for the treatment of HIV, reinforcing why Zidovudine is the correct choice for this specific question.