Immunostimulatory neem leaf preparation acts as an adjuvant to enhance the efficacy of poorly immunogenic B16 melanoma surface antigen vaccine

Immunogenecity of the poorly immunogenic B16 melanoma cell surface antigen (B16MelSAg) was enhanced by combining B16MelSAg with NLP in C57BL/6 mice, as evidenced by ELISA and flow cytometry. NLP was as effective as Freund's complete and incomplete adjuvant to generate antibodies recognizing the B16MelSAg. The NLP generated antibody was a gamma globulin with a subtype of IgG1. Splenic lymphocytes from B16MelSAg + NLP treated mice proliferated more rapidly in vitro when stimulated by specific (B16MelSAg) and nonspecific (ConA) stimulators, in comparison to the proliferation detected in B16MelSAg and NLP treated groups. Vaccination of mice with B16MelSAg + NLP more efficiently prevented the growth of B16 melanoma tumor than mice immunized with B16MelSAg or NLP alone. In another experiment, the immune sera (B16MelSAg + NLP) was mixed with B16Mel tumors and injected subcutaneously into syngenic C57BL/6 mice. Tumor burden was less in mice receiving a tumor along with B16MelSAg + NLP generated immune sera than other groups. The B16MelSAg + NLP generated immune sera induced antibody dependent cellular cytotoxicity specifically towards B16Mel tumor cells in vitro. We concluded that NLP might be a potential immune adjuvant for inducing active immunity towards tumor antigens.