Infection with HIV, the human immunodeficiency virus, causes the disease called AIDS, or Acquired Immune Deficiency Syndrome.

First recognized in 1981, AIDS and HIV infection are now found in every country, but they are especially common in sub-Saharan Africa where in some countries there up to 25% of the population are infected.

How HIV infection makes you ill
HIV infection progressively weakens the immune system, and most of the obvious effects of HIV infection relate to immune deficiency which allows "opportunistic" infections and cancers to occur. "Opportunistic" means that these infections and cancers are rarely if ever seen in individuals with normal immune systems. Late-stage HIV infection, with an immune system that is weakened such that the individual is susceptible to opportunistic infections and cancers, is called AIDS.

The immune deficiency due to HIV is largely because HIV infects a particular type of lymphocyte (a white blood cell) called a "helper-inducer" or "CD4" lymphocyte. These CD4 lymphocytes are key to initiating and sustaining the immune responses which protect us from cancer and infections. HIV infection of CD4 lymphocytes makes they dysfunctional, and also kills the prematurely, resulting in a decline of CD4 lymphocytes during HIV infection.

HIV infection is the only infection known to cause progressive and ultimately fatal immunodeficiency.

How susceptible a patient with HIV infection is to opportunistic infections and cancers can be assessed by the number of CD4 lymphocytes in the blood (the "CD4 count"). Normal is from about 450 to over 1000; patients with AIDS generally have 100 or less.

HIV infection can also cause neurologic disease and other conditions, although they are less common that immune deficiency.

Treatment of HIV infection
HIV infection is now very effectively treated with "antiretrovirals" - antiviral drugs which target HIV infection. There are now almost two dozen antiretrovirals available, and these are always given in combination (usually three or four at once, but sometimes more), as combinations of these drugs virtually completely inhibit HIV infection, prevent it becoming resistant to antiretrovirals, and prolong life and prevent patients from developing AIDS. Combination therapy is also known as Highly-Active AntiRetroviral Therapy, or HAART.

At present there are four classes of antiretrovirals; they are classified by the step in the HIV replication cycle that they target and their chemical structure.

In addition, there are investigational drugs which inhibit the HIV integrase enzyme, and several investigational drugs targeting the mechanisms which allow virus particles to enter cells.

Narhex's investigational drug DG35 is a member of the protease inhibitor class.

HAART does not cure HIV infection, even after many years of therapy. Hence, once patients with HIV infection start HAART they must continue for life. As with many other illnesses requiring life-long therapy (e.g. hypertension, elevated cholesterol, arthritis), it is important to have a wide range of drugs available, even within the same drug class, as patients differ in how they respond to specific drugs, both with respect to efficacy and toxicity.

More Information About HIV and AIDS
There are many web sites with useful, accurate information about HIV infection and AIDS, but some of the best are:

WHO/United Nations AIDS Program : particularly good for an overall global picture of the impact of the HIV epidemic.

InSite, Center for HIV Information (CHI) : Excellent, detailed information about all aspects of HIV infection and AIDS.

AIDS Map : Another website with excellent, detailed information about HIV & AIDS.

AIDSinfo : A site sponsored by the US Government's National Institutes of Health. Provides written recommendations for many aspects of HIV diagnosis and treatment.