The impact of concurrent and treated Ancylostoma ceylanicum hookworm infections on the immunogenicity of a recombinant hookworm vaccine in hamsters

Background. The effect of concurrent (active) and treated hookworm infections on the immunogenicity of vaccination with the recombinant fusion protein Ay- Ancylostoma-secreted protein 2 was analyzed in the Golden Syrian hamster. Methods. Hamsters were infected with the hookworm Ancylostoma ceylanicum and vaccinated with the recombinant protein, with Quil A used as adjuvant. As controls, hookworm-infected hamsters were treated with the anthelmintic drug pyrantel pamoate before vaccination. Naive hamsters (i. e., those with neither previous hookworm infections nor treatment) were also vaccinated. Results. The proliferation capacities of carboxyfluorescein diacetate succinimidyl ester-positive lymphocytes from the hookworm-infected vaccinated group were reduced by 50% relative to the capacities of lymphocytes from uninfected or treated vaccinated hamsters; capacities were comparable to the rates observed in lymphocytes from the hamsters vaccinated with the adjuvant alone. Immunoglobulin G1 antibody responses were also reduced in the actively infected, untreated hamsters, and interferon-gamma and interleukin-4 cytokine mRNAs were downregulated. Conversely, interleukin-10 and tumor necrosis factor-alpha mRNAs were up-regulated in those hamsters. Conclusions. These results suggest that hookworm infections have an immunomodulatory effect by impairing the immune response to an exogenous antigen during infection. The hookworm-associated immunodepression may have important implications for design of clinical trials of human vaccines and vaccination strategies.