CCR5 Testing and HIV Tropism

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CCR5 Testing and HIV Tropism

What Is HIV Tropism Testing?

Human immunodeficiency virus (HIV) tropism testing helps figure out if a drug called maraviroc (Selzentry®) is likely to work against a person's particular kind of HIV.

HIV copies itself by infecting white blood cells called CD4 cells. HIV gets into the CD4 cell by attaching to one of two proteins that sit on the outside of the cell. These proteins are called the CCR5 and CXCR4 receptors.

HIV may use CCR5, CXCR4, or a combination of both to infect cells. HIV tropism testing looks at a person's HIV infection to find out which receptors the virus uses.

There are three main types of tropism:

  1. CCR5 tropism (also called R5-tropic): HIV virus infects cells using the CCR5 receptor only.
  2. CXCR4 tropism (also called X4-tropic): HIV virus infects cells using the CXCR4 receptor only.
  3. Dual or mixed tropism: HIV virus uses either receptor to infect cells.

Maraviroc is an HIV drug that attaches to the CCR5 receptor and blocks HIV from using it to get into the cell. Maraviroc does not block HIV that uses the CXCR4 receptor.

Maraviroc only works in people infected with CCR5-tropic HIV. It should not be taken by people with virus that uses only CXCR4 or a combination of both receptors.

Right now, HIV tropism testing is only used to predict maraviroc response. In the future, it could be used to predict response to other drugs that target CCR5 or CXCR4 specifically.

Next: Who Should Consider HIV Tropism Testing for Maraviroc Response?