Objective: We have postulated that the host autoimmune response regulates and mediates CD4 depletion during HIV infection by opsonization of circulating CD4(+) lymphocytes carrying autoreactive immune complexes (IC) consisting of complement-fixing IgM and IgG, and during advanced stages of HIV disease of IgM/ IgG/gp120 complexes. In this retrospective study, we investigated whether HIV causes CD4 depletion by direct cytotoxicity or indirectly by induction of a host autoimmune response.
Patients and methods: In 1996, 12 HIV(+) hemophilia patients were converted to highly active antiretroviral therapy (HAART), while 10 other patients were maintained on conventional antiretroviral treatment and another 11 patients refused to be treated with antiretroviral drugs. The host immune response of these 33 HIV(+) patients was studied during the periods of minimum viral replication (Interval 1), subsequent rise in viral replication with strong replication dynamic (Interval 2), and maximum viral replication (Interval 3). The patients were categorized into three groups according to viral load (VL). Group A: patients with low level VL (n=10) showed a modest increase from <80 to <4 log 10 HIV-1 RNA copies per milliliter plasma during the observation period; Group B: patients with medium level VL (n=12) showed a stronger increase from <80 to >4 log 10 copies per milliliter plasma; and Group C: patients with high level VL (n=11) consistently had a median of >4 log 10 copies per milliliter plasma, during Intervals 1-3, with the exception of one patient who during Interval 2 had 4800 copies per milliliter. Blood lymphocyte subpopulations, proportions of CD4(+) blood lymphocytes coated with IgM, IgG, C3d and/or gp120, in vitro responses to mitogens and pooled allogeneic stimulator cells, as well as numbers of HIV-1 RNA copies per milliliter plasma were measured.
Results: Sequential analysis of VL, IC load on CD4(+) blood lymphocytes and CD4 counts showed that an increasing VL was not associated with CD4 depletion, when the proportion of IC-coated circulating CD4(+) blood lymphocytes remained stable. When, CD4 counts and IC load were analyzed during corresponding intervals of retroviral replication in the three patient groups, a higher VL was associated with lower CD4 counts only when the IC load (IgG or gp120/IgG) on CD4(+) lymphocytes was higher as well.
Conclusion: These data suggest that HIV regulates and mediates CD4 depletion in part by the induction of autoreactive ICs against CD4(+) lymphocytes, especially complement-fixing autoreactive IgG and gp120/IgG complexes.