Efficacy evaluation of two synthetic lysine lipidated tripeptides as vaccine adjuvants against HBsAg.

In the present investigation, adjuvant potential of two novel lipidated tripeptide lysine derivatives (KKSM and KKSMB) was evaluated using various in vitro and animal-derived models of humoral and cell-mediated immune events in response to hepatitis B surface antigen (HBsAg). The results were compared with alum adjuvanted with HBsAg. Both these molecules were found to stimulate anti-HBsAg IgG and neutralizing (IgG1 and IgG2a) antibody titres in mice sera. The two molecules stimulated the proliferation of T-lymphocyte sub-sets (CD4/CD8) as well as the production of soluble mediators of Th1 (IL-2 and IFN-γ) and Th2 response (IL-4) in spleen cell culture supernatant. Furthermore, the two lipidated tripeptides enhanced the CD4, CD8, CD3 and CD19 cell populations as well as CD4/CD8 derived IL-2, IL-4, IFN-γ and TNF-α in whole blood of treated mice. There was found to be the significant enhancement in the release of IL-12, IFN-γ and nitrite content in macrophage supernatant. Moreover, the two lipidated tripeptides enhanced the population of CD80 and CD86 in spleen-derived macrophages and did not show any hemolytic effect on rabbit RBCs. Taken together, these results suggest that both these molecules are the potent enhancers of anti-HBsAg immune response via augmenting Th1/Th2 response in a dose dependent manner.

Immunomodulatory studies of a bioactive fraction from the fruit of Prunus cerasus in BALB/c mice.

In order to evaluate the role of ethyl acetate fraction (PNRS-EtOAC) obtained from the Prunus cerasus fruit in the modulation of immune responses, detailed studies were carried out using a panel of in vivo assays. Oral administration of PNRS-EtOAC (25-100 mg/kg) stimulated the IgM and IgG titre expressed in the form of hemagglutination antibody (HA) titre. Further, it elicited a dose related increase in the delayed type hypersensitivity reaction (DTH) after 24 and 48 h in BALB/c mice. Besides augmenting the humoral and cell mediated immune response, the concentration of cytokines (IFN-γ, IL-4, and TNF-α) in serum with respect to T cell interactions, i.e. the proliferation of lymphocytes were significantly increased at 50 mg/kg compared with the control. The results in these studies demonstrated the immunostimulatory effect of PNRS-EtOAC in a dose-dependent manner with respect to the macrophage activation possibly expressing the phagocytosis and nitrite production by the enhancement of TNF-α production as a mode of action.

Study of the adjuvanticity of lysine lipopeptides; carbamate analogs elicit strong Th1 and Th2 response to ovalbumin in mice.

Bacterial lipoproteins and their synthetic analogs are strong immune modulators of the early host responses. In view of the strong adjuvanticity of bacterial lipopeptide mimics bearing lysine residues, a focused library of lipidated dipeptides and tripeptides has been synthesized with a view to understand the pattern of activity vis a vis the site and extent of lipidation. Compounds 4, 5 and 14 stimulate OVA specific IgG titer, neutralization of antibodies (IgG1 and IgG2a), T lymphocyte sub-sets (CD4/CD8) and its production of soluble mediators for Th1 (IFN-γ)/Th2 (IL-4) cytokines and costimulatory molecules (CD80/CD86) which are ideal traits of immune adjuvants. The results support lipidated lysine dipeptides as potent enhancers of humoral and cell mediated immune responses and thus might become promising immune-adjuvants for self adjuvanted vaccines.