Immunity against HIV Virus

HIV attacks CD4 T lymphocytes, macrophages, and dendritic cells. Until recently, the CD4 molecule was believed to be the only receptor that HIV uses to enter lymphocytes, but not all of the experimental data supported this. For example, although 10¹⁰ HIV virions are produced per day, a minority of CD4 T lymphocytes from patients infected with HIV contain the virus and some lymphocytes are resistant to infection. This resistance to HIV infection seems to be associated with the activity of a family of attractant inflammatory peptides (called the CC chemokines), which contribute to cell wall adhesion and tissue migration and are produced by CD8 T lymphocytes. During initial infection HIV enters the cell through the CC-CKR-5 receptor (CC-chemokine receptor). The CC-CKR-5 receptor is activated by the chemokine’s RANTES (which stands for regulated by activation, normal T cell expressed and secreted), MIP-1α, and MIP-1β (macrophage inflammatory protein 1α and 1β). Once a person is infected, however, the CXCR-4 receptor, another chemokine receptor, is used by HIV to enter cells and spread from one CD4 T lymphocyte to another. People who are apparently uninfected despite repeated exposure have allotypic variants of the CC-CKR-5 receptor.

• The cellular receptor used by HIV infusing with target cells has been identified. The natural ligand for the receptor is capable of blocking HIV transmission in vitro, implying a new treatment strategy
• Motor vehicle pollution is implicated in the pathogenesis of asthma. Genetic studies link the disease with the gene for interleukin 4, a cytokine known to enhance IgE production
• The subdivision of CD4, and now CD8, T lymphocytes into groupings on the basis of cytokine production is promoting a greater understanding of the role of these cells in allergy, autoimmunity, and infection
• The crystallization of a complex of T cell receptor, peptide antigen, and a molecule of the major histocompatibility complex has provided the best insight yet of how these molecules interact to achieve T cell activation

Clearly, if the entry of the virus through chemokine receptors into CD4 T lymphocytes, macrophages, and dendritic cells is preventable, then people could be protected. Furthermore, prevention of viral spread in infected patients could maintain the virus at a low concentration, allowing the immune system to eliminate it. Great strides have been made in developing a vaccine against HIV.