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Human immunodeficiency virus (HIV)

HIV is a lentivirus , a member of the retrovirus family that causes acquired immunodeficiency syndrome (AIDS). HIV is different in structure from other retroviruses. It is roughly spherical with a diameter of about 120 nm, around 60 times smaller than a red blood cell, yet large for a virus . [The RNA genome consists of at least seven structural landmarks (LTR, TAR, RRE, PE, SLIP, CRS, and INS) and nine genes (gag, pol, and env, tat, rev, nef, vif, vpr, vpu, and tev) encoding 19 proteins. Three of these genes, gag, pol, and env, contain information needed to make the structural proteins for new virus particles.]

There are two species of HIV known to exist: HIV-1 and HIV-2. HIV-1 is more infectious than HIV-2. HIV-1 is a globel AIDS causing retrovirus,HIV-2 is confined to west Africa. The strains of HIV-1 can be classified into four groups: the "major" group M, the "outlier" group O and two new groups, N and P.

HIV infects primarily vital cells in the human immune system such as helper T cells (to be specific, CD4+ T cells), macrophages, and dendritic cells. HIV infection leads to low levels of CD4+ T cells through three main mechanisms: First, direct viral killing of infected cells; second, increased rates of apoptosis in infected cells; and third, 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]

Current highly benificial treatment for HIV infection is the Highly Active AntiRetroviral Therapy(HAART), its a combination (or "cocktails" ) of at least three drugs belonging to at least two types, or "classes," of antiretroviral agents.However, after over 20 years of research, HIV-1 remains a difficult target for a vaccine.


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