Transmission and Prevention of HIV - HIV is primarily transmitted through sexual contact, sharing contaminated needles, and from an infected mother to her infant during pregnancy, childbirth, or through breast milk. - Condom use and practicing safe sex can reduce the risk of HIV transmission. - HIV transmission is unlikely if the HIV-positive partner has a consistently undetectable viral load. - It is important to use barrier methods, such as condoms, to reduce the risk of HIV transmission.

Impact on the Immune System and Development of AIDS - HIV infects vital cells in the immune system, leading to low levels of CD4 T cells. - As CD4 T cell numbers decline, the body becomes more susceptible to opportunistic infections and the development of AIDS. - HIV can cause the death of infected cells, leading to a loss of cell-mediated immunity. - The loss of cell-mediated immunity allows opportunistic infections and cancers to thrive.

Structure and Genome of HIV - HIV is a retrovirus with a roughly spherical structure and contains two copies of positive-sense single-stranded RNA. - The RNA is tightly bound to nucleocapsid proteins and enzymes needed for virion development. - The viral envelope surrounds the capsid and contains proteins from both the virus and the host cell. - The envelope protein allows the virus to attach to target cells and initiate the infectious cycle.

HIV-1 and HIV-2 - HIV-1 is more virulent and infective than HIV-2, causing the majority of HIV infections globally. - HIV-2 has a lower infectivity and is largely confined to West Africa. - Both types of HIV can lead to the development of AIDS if left untreated.

Advances in HIV Research and Diagnosis - Structural biology techniques have allowed the determination of the viral spike's molecular structure, leading to the development of promising vaccine candidates. - Recombinant trimeric viral spikes known as SOSIP trimers reproduce the antigenic properties of the native viral spike. - Understanding the structure and biology of HIV is crucial for developing effective prevention strategies and treatments. - HIV testing involves initial screening with an enzyme-linked immunosorbent assay (ELISA) to detect antibodies, followed by confirmatory testing with more specific supplemental tests.