HIV-Related Illnesses
T-cell counts help predict risk.

Opportunistic infections (OIs) are illnesses that develop when the immune system is weakened due to HIV activity. After exposure to the virus, individuals typically develop transient, flu-like symptoms lasting two weeks; a prolonged fever may be a predictor of rapid disease progression. Over time, HIV gains an edge over the immune system, leading to a range of HIV-related illnesses, or OIs. Some people progress to disease more rapidly than others, and today we have clues about why that happens.

A new theory put forth by scientists working with AIDS researcher Dr. Anthony Fauci at the National Institute of Allergy and Infectious Diseases suggests that when HIV binds to immune T-cells, proteins on the outside of the virus cause those cells to send out a faulty chemical signal or message that lures other uninfected cells into lymphoid tissue that is packed with HIV. This "T-cell homing," say federal researchers, causes a loss of T-cells that leads to a progressive loss of immune function.

Over the past two years, many studies have shown that triple-drug therapy (also known as Highly Active Antiretroviral Therapy, or HAART) greatly reduces one’s risk of developing OIs, especially PCP, MAC, and CMV. Across the board, the incidence of most OIs has declined dramatically in people on successful HAART regimens. One exception is non-Hodgkin’s lymphoma, which continues to crop up in some individuals on therapy (see "HIV and Cancer"). Other infections, like hepatitis C and human papillomavirus, have been reported in individuals taking combination regimens, particularly those who have very low T-cells or advanced HIV disease.

As a result, experts are now reviewing federal guidelines on the role of prophylaxis, or preventive therapy, for various HIV-related OIs. In general, healthy people with over 500 T-cells are considered at low risk for developing OIs. HIV prophylaxis is still recommended when T-cells drop below 200. But experts suggest that some people on therapy with high, stable T-cell counts might be able to discontinue PCP and MAC prophylaxis.

At the World AIDS Conference in Geneva in June, preliminary studies showed that it’s possible to predict the risk of getting an OI after three months on HAART therapy using a 200 T-cell count as the cutoff point. A persistent low T-cell count of 200 or less after three months was linked to a risk of developing an OI—regardless of whether one has a detectable viral load or is below the limit of detection, say experts. They recommend that these individuals continue prophylactic therapy. For those with more than 200 T-cells after three months on HAART, the risk is lower, and stopping prophylaxis may be an option. This should be carefully discussed with your doctor, taking into consideration that not all OIs are covered.

New evidence also shows that some individuals on HAART may experience transient "immune-mediated" reactivation of some infections, like CMV, that may last up to a year. Researchers are hunting for the cause of these passing symptoms (see "Immune Recovery Syndrome"). It’s also important to keep in mind that there’s still a risk of developing OIs if your drug regimen fails or HIV drug resistance occurs. Looking ahead, new immune-based diagnostic tests are being developed to help people on therapy monitor their progress (see "Immune Boosters").