Viral Load in Blood and Lymph Tissues of HIV-Infected Individuals

Our laboratory has previously demonstrated that lymph nodes are a major reservoir for human immunodeficiency virus (HIV) and a major site of active virus replication in infected individuals(1-3). There is at least a 10 fold greater viral burden per given number of CD4+ T lymphocytes obtained from the lymph nodes versus the peripheral blood in the same infected individual. These data have been accumulated predominantly in individuals with progressive generalized lymphadenopathy (CDC Class A1 and A2). It is unclear at present whether this pattern holds true for all categories of HIV infected individuals. We have proposed that the seeding of lymph nodes by HIV early in the course of HIV infection and the persistent production of virus in lymph nodes throughout the course of infection are major factors in the pathogenesis of HIV in virtually all infected individuals. In addition, it is likely that the selective perturbations of various T cell subsets (i.e., V-B classes of CD4+T cells) that have been observed in peripheral blood are much more dramatic in the lymph node given the greater viral burden in the lymph node compared to the peripheral blood. In order to investigate this hypothesis, it is essential that we study simultaneously lymph nodes and peripheral blood from the same individuals and that we study different individuals at various stages of disease from early in the course of infection (CDC Class A) to advanced disease (CDC Class B and C). If, as we suspect, there is active virus replication in the lymph node early in the course of infection, even at a time when there is little virus burden or active replication in the peripheral blood, this would justify anti-retroviral therapy at the earliest possible time in the course of infection. In addition, in certain patients who are about to initiate treatment with an anti-retroviral agent such as zidovudine or didanosine through their private physician, it would be important to know whether treatment actually reduces the viral burden and virus replication in lymph nodes. The effect of therapy on viral burden and replication will be compared in the lymph node versus peripheral blood mononuclear cells and both of these parameters will be compared with the level of plasma viremia.