Structured Intermittent Therapy
Because of drug toxicities, drug resistance, difficulties with ad-herence, and the high cost of medications, the complex medica-tion regimen is often difficult for patients to follow. In an effort to determine if alternative treatment approaches are possible, a study is underway to examine patients’ responses to stopping HAART therapy by monitoring their immune status and viral load (Dybul et al., 2001). This would allow patients to move from a continuous regimen of anti-HIV therapy to a strategy in which they discontinue therapy for a specific period of time (ie, 7 days) and then resume therapy for 7 days. This approach is known as structured intermittent therapy. While preliminary re-sults of the study are promising, larger studies are needed to de-termine the effectiveness of these alternative medication regimens.
Combating HIV infection requires not only agents that will in-hibit viral growth but also those that will restore or augment the damaged immune system. New therapies are needed to restore immune function, and immunologic markers need to be identi-fied to predict the success of therapy (NIAID, 2001). Current re-search is testing the effectiveness of interleukin-2, interleukin-12, and other cytokines and lymphokines (NIAID, 2001).
HIV-1 is a uniquely difficult target for the development of vac-cines (Letvin, 1998). Since HIV-1 was discovered, researchers have been working to develop a vaccine. A vaccine is a substance that triggers the production of antibodies to destroy the offending organism. Most vaccines activate the humoral arm of the immune system, which stimulates the production of protective antibodies. In addition to antibodies, B lymphocytes take the form of mem-ory B cells. These cells do not produce antibodies immediately but respond vigorously to subsequent exposure. Vaccines that stimu-late the cellular arm of the immune system are being developed. Since 1995, there have been a variety of vaccines under study using different strategies to prevent HIV infection in animals and humans. Some researchers are exploring whether different im-munization schedules, different schedules of boosters, or a com-bination of several vaccines will result in stronger or more durable responses. Creation of an HIV vaccine is feasible, but a world-wide commitment is needed. Cooperation between all nations is necessary to develop and commit the resources to develop the vaccine and to create and support the infrastructure needed to facilitate testing of vaccine immunogens (Letvin, Bloom & Hoffman, 2001).
Clinical trials began in November 2002 to test an HIV vac-cine that incorporates three HIV subtypes that cause about 90% of all HIV-1 infections around the world. The first phase of this yearlong trial, which is being conducted at NIH, is examining the vaccine’s safety. Subsequent trials will be conducted to deter-mine the immune response to the vaccines (NIH News Release, 11/13/2002).