Question

Describe the molecular mechanisms responsible for HIV recognition of T helper cells (T_H cells) and HIV import across the T_H cells plasma membrane.

Answer 1

Helper T cells play a pivotal role in HIV recognition. HIV primarily infects CD4⁺ T cells, causing loss of functional CD4⁺ T cells in the advance stage of disease, which leads to the acquired immunodeficiency syndrome (AIDS). During the non-symptomatic phase of HIV infection, the virus kills CD4⁺ T cells slowly. But once it becomes lymphotropic, the killing rate increases enormously. Subsequently, CD4⁺ T cell level begin to decrease, and it is hard to determine CD4⁺ T cell population against selected antigens that could potentially be detected. Furthermore, CD8⁺ T cells are also unable to stimulate effectively during HIV infection. Antibody class switching is directly related to the T cells functions. When T cells function fails, the immune system losses its ability to generate B cells that is mainly responsible to produce antibody groups such as IgG and IgA.

HIV import across the TH cells plasma membrane is mediated by different factors and cofactors involved in this pathway. HIV Env (envelope) comprises of gp120 and gp41 subunits. These proteins first attach to the CD4 on host cell membrane, resulting a conformational changes in Env. This conformational changes allow other coreceptors to bind, which is mediated by the V3 loop of the Env. The fusion peptide of gp41 inserts in to the host cell membrane, followed by six-helix bundle formation. By this way, it can enter into the TH cells.