Factors that Affect Disease Progression

Mutations in HIV Co-receptors

Most strains of HIV use a co-receptor molecule called CCR5, in addition to the CD4 molecule, to infect a cell. Other HIV strains use a different co-receptor known as CXCR4 to attack cells. Both receptors enable the virus to enter a cell during the initial stage of HIV infection.

Studies have shown that people infected with HIV who have specific genetic mutations in one of their two copies of the CCR5 gene progress to AIDS slower than people with two normal copies of the CCR5 gene. There are also rare individuals with two mutant copies of the CCR5 gene who appear, in most cases, to be completely protected from HIV infection. Gene mutations in other HIV co-receptors such as CXCR4 also may influence the rate of disease progression.

High Viral Load

The amount of HIV in a person’s blood often is called his or her viral load. People with high viral loads are more likely to progress to AIDS faster than people with lower levels of the virus. In addition, research has shown that the level of HIV in a person’s blood after the first few months of infection, known as the viral set point, also influences the speed of progression to AIDS. Those with higher viral set point are much more likely to get sick faster than those with lower viral set point.

Highly active antiretroviral therapy (HAART), which is a potent combination of three or more antiretroviral drugs belonging to at least two different antiretroviral drug classes, can help lower the viral load and viral set point for those infected with HIV. For many people, HAART delays the progression to AIDS for a prolonged period of time.