Human Infection with<i>Ascaris lumbricoides</i>Is Associated with Suppression of the Interleukin-2 Response to Recombinant Cholera Toxin B Subunit following Vaccination with the Live Oral Cholera Vaccine CVD 103-HgR

To investigate the potential immunomodulatory effects of concurrent ascariasis on the cytokine response to a live oral vaccine, we measured cytokine responses to cholera toxin B subunit (CT-B) following vaccination with the live oral cholera vaccine CVD 103-HgR in Ascaris lumbricoides-infected subjects randomized in a double-blind study to receive two doses of either albendazole or placebo prior to vaccination and in a group of healthy U.S. controls. Postvaccination cytokine responses to CT-B were characterized by transient increases in the production of interleukin-2 (IL-2; P = 0.02) and gamma interferon (IFN-gamma; P = 0.001) in the three study groups combined; however, postvaccination increases in IFN-gamma were significant only in the albendazole-treated A. lumbricoides infection group (P = 0.008). Postvaccination levels of IL-2 were significantly greater in the albendazole-treated group compared with the placebo group (P = 0.03). No changes in levels of Th1 and Th2 cytokines in response to control ascaris antigens were observed over the same period. These findings indicate that vaccination with CVD 103-HgR is associated with a Th1 cytokine response (IL-2 and IFN-gamma) to CT-B, that infection with A. lumbricoides diminishes the magnitude of this response, and that albendazole treatment prior to vaccination was able to partially reverse the deficit in IL-2. The potential modulation of the immune response to oral vaccines by geohelminth parasites has important implications for the design of vaccination campaigns in geohelminth-endemic areas.