What virus is known to severely weaken the body's immune system and is a precursor to AIDS?

HIV, or Human Immunodeficiency Virus, is the virus that is well-documented for its role in severely compromising the immune system, which can ultimately lead to acquired immunodeficiency syndrome (AIDS). The significance of HIV lies in its targeting of CD4 cells, a type of white blood cell that plays a critical role in the immune response. As HIV attacks and destroys these cells, the body becomes increasingly vulnerable to opportunistic infections and certain cancers, marking the progression towards AIDS if not treated effectively.

The other viruses mentioned are not responsible for this specific immune deficiency progression. HTLV (Human T-cell Lymphotropic Virus) is associated with certain types of leukemia and tropical spastic paraparesis but does not directly lead to AIDS. HSV (Herpes Simplex Virus) can cause recurrent infections but does not have the same immunosuppressive effects as HIV. HCV (Hepatitis C Virus) primarily affects the liver and can cause liver disease, but it is not related to the progression to AIDS. Hence, HIV stands out as the virus that directly links to the weakening of the immune system leading to AIDS.