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.
The human immunodeficiency viruses (HIV) are two species of Lentivirus (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive. Without treatment, the average survival time after infection with HIV is estimated to be 9 to 11 years, depending on the HIV subtype.
| Human immunodeficiency viruses | |
|---|---|
| |
| Scanning electron micrograph of HIV-1 (in green) budding from cultured lymphocyte. Multiple round bumps on cell surface represent sites of assembly and budding of virions. | |
Scientific classification
| |
| (unranked): | Virus |
| Realm: | Riboviria |
| Kingdom: | Pararnavirae |
| Phylum: | Artverviricota |
| Class: | Revtraviricetes |
| Order: | Ortervirales |
| Family: | Retroviridae |
| Subfamily: | Orthoretrovirinae |
| Genus: | Lentivirus |
| Groups included | |
| Other lentiviruses | |
In most cases, HIV is a sexually transmitted infection and occurs by contact with or transfer of blood, pre-ejaculate, semen, and vaginal fluids. Non-sexual transmission can occur from an infected mother to her infant during pregnancy, during childbirth by exposure to her blood or vaginal fluid, and through breast milk. Within these bodily fluids, HIV is present as both free virus particles and virus within infected immune cells. Research has shown (for both same-sex and opposite-sex couples) that HIV is untransmittable through condomless sexual intercourse if the HIV-positive partner has a consistently undetectable viral load.
HIV infects vital cells in the human immune system, such as helper T cells (specifically CD4+ T cells), macrophages, and dendritic cells. HIV infection leads to low levels of CD4+ T cells through a number of mechanisms, including pyroptosis of abortively infected T cells, apoptosis of uninfected bystander cells, direct viral killing of infected cells, and killing of infected CD4+ T cells by CD8+ cytotoxic lymphocytes that recognize infected cells. When CD4+ T cell numbers decline below a critical level, cell-mediated immunity is lost, and the body becomes progressively more susceptible to opportunistic infections, leading to the development of AIDS.
