Immonotoxicity of Zidovudine Plus Sulfamethoxazole-Trimethoprim Exposure

HIV -infected individuals endure an immunodeficiency syndrome that has been well-described. However, the fate of B lymphocytes in this population remains underappreciated, Despite having elevated IgG titers, HIV -infected individuals have an impaired ability to produce specific antibodies in response to neo-antigens. Previous work in mice suggests that simultaneous exposure to zidovudine (ZDV) and sulfamethoxazole-trimethoprim (SMX- TMP) causes a synergistic immunotoxicity, specifically to the ability to produce an antigen-specific antibody response. Pilot clinical data from our group shows that ZDV plus SMX- TMP exposure impacts influenza-specific serum IgG titers in HIV -infected subjects postvaccination, and eliminates the positive correlation typically observed between IgG titers and CD4+ counts. Decreased proliferation and antibody production have been demonstrated in B cells responding to T cell-independent B cell mitogens in individuals infected with HIV, Our hypothesis is that exposure to ZDV plus SMX- TMP contributes to the B cell defects observed among HIV-infected individuals. We aim to 1) evaluate ex vivo proliferation, antibody production, and cytokine secretion of Band T cells isolated from subjects treated with ZDV plus SMX- TMP and 2) differentiate whether this immunotoxicity affects innate B cell function, T cell help, or both, Subjects will be recruited from the University of Kentucky Bluegrass Care Clinic who are HlV infected, receiving combination antiretroviral therapy that includes ZDV, have CD4+ counts greater than 350 cellsiJ.tI, and undetectable viral loads. Fifteen patients who grant informed consent will be included in the final analysis, Each subject will be given a 30-day experimental course of SMX-TMP (l double-strength tablet daily). Blood will be obtained from each subject by venipuncture at the beginning and at the end of treatment. Peripheral blood mononuclear cells will be isolated by Ficoll gradient purification for analysis. Data from before and after treatment will be compared, with each subject serving as his or her own control. Cells will be cultured with mitogens of different types to stimulate proliferative and antibody responses as follows: pokeweed antigen (T cell-dependent B cell mitogen), Staphylococcus aureus Cowan (T cell-independent B cell mitogen), and phytohemagglutinin A (T cell mitogen). Proliferation will be assayed by hemocytometric enumeration. Antigen-specific antibody responses will be measured by an ELISA assay of the collected culture upernatants, quantifying titers of IgG and IgM. The number of antigen-specific antibody secreting cells will be determined by an ELISPOT technique. Further, T cells will be assayed for their ability to secrete cytokines, including tumor necrosis factor-a, interferon-y, interleukin (IL)-2, and IL-4 by utilizing cytometric bead array technology and flow cytometry. These data will provide evidence as to the mechanism of this drug toxicity in humans by examining the functionality of Band T cells in this in vitro context. Clinicians involved in the treatment of patients in this population will benefit from the knowledge of additional immunosuppression this drug combination may cause.