Nizatidine, a small molecular compound, enhances killed H5N1 vaccine cell-mediated responses and protects mice from lethal viral challenge.

Nizatidine (NIZ), closely related to Cimetidine, is a histamine H2 receptor inverse agonist used primarily as an anti-acid drug. Recent studies showed that this class of compounds may also modulate immune responses. To evaluate adjuvant effects of NIZ on vaccine immune modulation, we formulated NIZ with a H5N1 killed viral antigen and tested in vitro and in vivo. NIZ activated DC maturation and stimulated Th1 and Th2 immune responses to H5N1 vaccine. As a result, it enhanced both antibody and T cell-mediated immune responses. We also observed that a single immunization into C57BL/6 mice blocked IL-10 upregulation and potentiated Th1/Th2 dual polarization. Importantly, the inoculation of H5N1 vaccine with NIZ significantly improved protection of animals from death after challenge and reduced virus loads in the lung tissues. Considering its water-soluble nature, compared with Cimetidine, Nizatidine may be a better choice to use as a vaccine adjuvant.