What are HIV Clades?

Mary McMahon
Mary McMahon
Clades A and D are common in East Africa, making them among the oldest clades.
Clades A and D are common in East Africa, making them among the oldest clades.

HIV clades are distinct subgroups of HIV, broken up by geographical region. Within each clade, the virus has a number of genetic similarities and markers which can be used to learn more about the evolution of HIV. The fact that many of the clades are quite distinctive and very different from each other has some very serious implications for scientists working on HIV/AIDS vaccines. Unfortunately, it may not be possible to develop a vaccine to protect people from all HIV clades, or it may not be possible to vaccinate against certain clades.

HIV clades help to explain why some people thrive on combination antiretroviral therapy and others do not respond to the treatment.
HIV clades help to explain why some people thrive on combination antiretroviral therapy and others do not respond to the treatment.

This virus is infamous for mutating extremely rapidly, a source of great frustration to doctors and HIV researchers. Even as researchers first began studying the evolution of HIV, the virus was already mutating, developing new traits and displaying new behaviors in the body. As researchers learned more about the virus, however, they were able to start recognizing and identifying distinct HIV clades; “clade” is simply a fancy word for a taxonomic grouping.

Studying HIV clades have helped researchers track the evolution of the virus.
Studying HIV clades have helped researchers track the evolution of the virus.

By studying HIV clades, researchers have been able to track the evolution of the virus, in the hopes of learning more about where it came from, how it spread, and how it could potentially be treated. Learning about HIV clades was an important step in the research needed to identify the origins of the HIV epidemic, as it allowed researchers to start pinpointing the region of the virus' origin, which turned out to be Africa.

Most people who test positive within a geographical area will have the same HIV clade.
Most people who test positive within a geographical area will have the same HIV clade.

There are two basic groups of HIV clades: M or Main, and O or Outgroup. The main clades cause the bulk of HIV infections, while outgroup HIV clades are more unusual, responsible for fewer infections. Because O clades are rare, sometimes they can be used to trace a very specific pathway of infection, if researchers can track down and test a large number of people.

Using contaminated needles and syringes may increase the number of HIV cases in a given area.
Using contaminated needles and syringes may increase the number of HIV cases in a given area.

Among the M clades, there are eight different subtypings, lettered A through H, and each geographic region tends to have a dominant clade. Clades A and D, for example, are common in East Africa, making them among the oldest clades, while clade B appears in Europe and the Americas, with clade C cropping up in East Asia. Viruses in each clade respond differently to treatment, and they have differing levels of virulence, which explains why some people respond very well to HIV/AIDS drugs, while others struggle with a series of drug regimens.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a InfoBloom researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a InfoBloom researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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    • Clades A and D are common in East Africa, making them among the oldest clades.
      Clades A and D are common in East Africa, making them among the oldest clades.
    • HIV clades help to explain why some people thrive on combination antiretroviral therapy and others do not respond to the treatment.
      HIV clades help to explain why some people thrive on combination antiretroviral therapy and others do not respond to the treatment.
    • Studying HIV clades have helped researchers track the evolution of the virus.
      Studying HIV clades have helped researchers track the evolution of the virus.
    • Most people who test positive within a geographical area will have the same HIV clade.
      Most people who test positive within a geographical area will have the same HIV clade.
    • Using contaminated needles and syringes may increase the number of HIV cases in a given area.
      Using contaminated needles and syringes may increase the number of HIV cases in a given area.
    • Blood testing is commonly used to detect the presence of HIV in a person's body.
      Blood testing is commonly used to detect the presence of HIV in a person's body.