Human immunodeficiency virus Introduction In 1983, scientists led by Luc Montagnier at the Pasteur institute in France, first discovered

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Human immunodeficiency virus

Introduction

In 1983, scientists led by Luc Montagnier at the Pasteur institute in France, first discovered the virus that causes AIDS. They called it lymphadenopathy-associated virus (LAV). A year later, Robert Gallo and Marvin Reitz of the United States, confirmed the discovery of the virus and they named it human T lymphotropic virus type III (HTL V-III). In 1986, both names were dropped in favour of the term human immunodeficiency virus (HIV).

AIDS is thought to have originated in sub-Saharan Africa during the twentieth century. By the end of 2004, it was estimated that 40 million people were currently living with HIV. Women account for 46% of all adults living with HIV. It is estimated that 28 million people have died of AIDS. Young people (15-24 year olds) account for half of all new HIV infections. More than 6,000 people become infected with HIV every day.

Of the 6.5 million people in developing and transitional countries who need life-saving drugs, only 1 million are receiving them.

Causative organisms

Diagram 1

HIV is a retrovirus. A retrovirus has some unique features;

  • Their genetic material is RNA instead of DNA
  • They contain the enzyme reserve transcriptase which enables the cell to make viral DNA from viral RNA
  • When the viral DNA is inserted into the host’s cell’s DNA it forms a provirus.

Retroviruses are characterised as being responsible for long duration illnesses associated with a long period of incubation.

Source of infection

Diagram 2

HIV begins its infection of a susceptible host cell by binding to the CD4 receptor on the host cell. CD4 is present on the surface of many lymphocytes, which are a critical part of the body's immune system. Recent evidence indicates that a coreceptor is needed for HIV to enter the cell. This recognition of HIV coreceptors and progress in understanding how HIV fuses with the cell has opened up new possibilities for antiviral drugs. A number of new agents are being designed to prevent infection by blocking fusion of HIV with its host cell.

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Following fusion of the virus with the host cell, HIV enters the cell. The genetic material of the virus, which is RNA, is released and undergoes reverse transcription into DNA. An enzyme in HIV called reverse transcriptase is necessary to catalyze this conversion of viral RNA into DNA. Once the genetic material of HIV has been changed into DNA, this viral DNA enters the host cell nucleus where it can be integrated into the genetic material of the cell. The enzyme integrase catalyzes this process, once the viral DNA is integrated into the genetic material of the host; it is ...

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