The Structure of HIV

The Origin of AIDS

HIV is now believed to have arisen by the mutation of a virus that had been endemic in wildlife in some areas of central Africa. Genetic studies of the virus have led to the conclusion that HIV-2 (a type of HIV that is weakly contagious and not often found outside of West Africa) is a mutation of a simian immunodeficiency virus (SIV). Mangabey monkeys in West Africa are naturally and harmlessly infected with this SIV. More recently, studies show that HIV- l (the primary HIV found worldwide in humans) is genetically related to another SIV that is carried by chimpanzees in Central Africa.

These SIV infections apparently crossed over relatively recently (well into the twentieth century) into the human population, known to eat "bushmeat." Mathematical models of the supposed evolution of HTV, by Bette Korber of the Los Alamos National Laboratory, calculate that the virus probably made the transition to humans around 1930. The disease may have smoldered with little notice as long as transmission was limited to small villages where rates of sexual promiscuity were lower. The virus could not have killed or incapacitated its hosts quickly; otherwise, it could not have been maintained in the village population. With the sudden end of European colonialism, the social structure of sub-Saharan Africa was disrupted. The population became urbanized; the developments that result from urbanization and contribute to an increase in sexual promiscuity, such as an increase in prostitution and the growth of highway transportation, are believed to be responsible for the spread of the disease.

HIV, of the genus Lentivirus, is a retrovirus. It has two identical strands of RNA, the enzyme reverse transcriptase, and an envelope of phospholipid (Figure 2). The envelope has glycoprotein spikes termed gp120 (the notation for a glycoprotein with a molecular weight of 120,000).

Figure 2 HIV structure and attachment to receptors on target T cell.

Дата добавления: 2014-01-11