The History of Human immunodeficiency virus (HIV): Science part four

Human immunodeficiency virus (HIV) is a kind of virus which can causes acquired immunodeficiency syndrome (AIDS),a condition in humans in which the immune system begins to fail, leading to life-threatening opportunistic infections. Infection with HIV occurs by the transfer of blood, semen, vaginal fluid, pre-ejaculate, or breast milk. Within these bodily fluids, HIV is present as both free virus particles and virus within infected immune cells. The four major routes of transmission are unsafe sex, contaminated needles, breast milk, and transmission from an infected mother to her baby at birth (perinatal transmission). Screening of blood products for HIV has largely eliminated transmission through blood transfusions or infected blood products in the developed world.


 
HIV infection in humans is considered pandemic by the World Health Organization (WHO). Nevertheless, complacency about HIV may play a key role in HIV risk.From its discovery in 1981 to 2006, AIDS killed more than 25 million people.HIV infects about 0.6% of the world's population. In 2005 alone, AIDS claimed an estimated 2.4–3.3 million lives, of which more than 570,000 were children. A third of these deaths are occurring in Sub-Saharan Africa, retarding economic growth and increasing poverty. According to current estimates, HIV is set to infect 90 million people in Africa, resulting in a minimum estimate of 18 million orphans. Antiretroviral treatment reduces both the mortality and the morbidity of HIV infection, but routine access to antiretroviral medication is not available in all countries.
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.
Most untreated people infected with HIV-1 eventually develop AIDS. These individuals mostly die from opportunistic infections or malignancies associated with the progressive failure of the immune system. HIV progresses to AIDS at a variable rate affected by viral, host, and environmental factors; most will progress to AIDS within 10 years of HIV infection: some will have progressed much sooner, and some will take much longer. Treatment with anti-retrovirals increases the life expectancy of people infected with HIV. Even after HIV has progressed to diagnosable AIDS, the average survival time with antiretroviral therapy was estimated to be more than 5 years as of 2005. Without antiretroviral therapy, someone who has AIDS typically dies within a year.

HIV is thought to have originated in non-human primates in sub-Saharan Africa and was transferred to humans late in the 19th or early in the 20th century.The first paper recognizing a pattern of opportunistic infections characteristic of AIDS was published in 1981.
Both HIV-1 and HIV-2 are believed to have originated in West-Central Africa and to have jumped species (a process known as zoonosis) from non-human primates to humans. HIV-1 appears to have originated in southern Cameroon through the evolution of SIV(cpz), a simian immunodeficiency virus (SIV) that infects wild chimpanzees (Pan troglodytes troglodytes). The closest relative of HIV-2 is SIV(agm), a virus of the sooty mangabey (Cercocebus atys), an Old World monkey of Guinea-Bissau, Gabon, and Cameroon. New World monkeys such as the owl monkey are resistant to HIV-1 infection, possibly because of a genomic fusion of two viral resistance genes.
Two theories have been offered for the rapid transmission of the initial human infection in Africa. The first is the introduction of millions of inexpensive, mass-produced syringes in the 1950s, introduced to treat yaws, syphilis, malaria, smallpox and polio. The syringes were reused without being sterilized. A second theory favored by Michael Worobey involves the migration of men to the cities in the 1910s where they made use of prostitution.

Discovery :
AIDS was first clinically observed between late 1980 and early 1981. Injection drug users and gay men with no known cause of impaired immunity showed symptoms of Pneumocystis carinii pneumonia (PCP), a rare opportunistic infection that was known to present itself in people with very compromised immune systems. Soon thereafter, additional gay men developed a previously-rare skin cancer called Kaposi’s sarcoma (KS). Many more cases of PCP and KS quickly emerged, alerting U.S. Centers for Disease Control and Prevention (CDC). A CDC task force was formed to monitor the outbreak. After recognizing a pattern of anomalous symptoms presenting themselves in patients, the task force named the condition acquired immune deficiency syndrome (AIDS).

In 1983, two separate research groups led by Robert Gallo and Luc Montagnier independently declared that a novel retrovirus may have been infecting AIDS patients, and published their findings in the same issue of the journal Science. Gallo claimed that a virus his group had isolated from an AIDS patient was strikingly similar in shape to other human T-lymphotropic viruses (HTLVs) his group had been the first to isolate. Gallo's group called their newly isolated virus HTLV-III. At the same time, Montagnier's group isolated a virus from a patient presenting lymphadenopathy (swelling of the lymph nodes) of the neck and physical weakness, two classic symptoms of AIDS. Contradicting the report from Gallo's group, Montagnier and his colleagues showed that core proteins of this virus were immunologically different from those of HTLV-I. Montagnier's group named their isolated virus lymphadenopathy-associated virus (LAV). HIV was chosen as a compromise between the two claims (LAV and HTLV-III).

Whether Gallo or Montagnier deserve more credit for the discovery of the virus that causes AIDS has been a matter of considerable controversy. Together with his colleague Françoise Barré-Sinoussi, Montagnier was awarded one half of the 2008 Nobel Prize in Physiology or Medicine for his "discovery of human immunodeficiency virus". Harald zur Hausen also shared the Prize for his discovery that human papilloma virus leads to cervical cancer, but Gallo was left out.Gallo said that it was "a disappointment" that he was not named a co-recipient. Montagnier said he was "surprised" Gallo was not recognized by the Nobel Committee: "It was important to prove that HIV was the cause of AIDS, and Gallo had a very important role in that. I'm very sorry for Robert Gallo."
Comparison of HIV species: HIV-1 Virulence High ,Infectivity High ,Prevalence Global ,Inferred originCommon Chimpanzee.HIV-2 Virulence Lower,Infectivity Low ,Prevalence West Africa, Inferred originSooty Mangabey.