Calcium phosphate nanoparticles induce mucosal immunity and protection against herpes simplex virus type 2

Abstract

Previously we reported that calcium phosphate nanoparticles (CAP) represented a superior alternative to alum adjuvants in mice immunized with viral protein. Additionally, we showed that CAP was safe and elicited no detectable immunoglobulin E (IgE) response. In this study, we demonstrated that following mucosal delivery of herpes simplex virus type 2 (HSV-2) antigen with CAP, CAP adjuvant enhanced protective systemic and mucosal immunity versus live virus. Mice were immunized intravaginally and intranasally with HSV-2 protein plus CAP adjuvant (HSV-2+CAP), CAP alone, phosphate-buffered saline, or HSV-2 alone. HSV-2+CAP induced HSV-specific mucosal IgA and IgG and concurrently enhanced systemic IgG responses. Our results demonstrate the potency of CAP as a mucosal adjuvant. Furthermore, we show that systemic immunity could be induced via the mucosal route following inoculation with CAP-based vaccine. Moreover, neutralizing antibodies were found in the sera of mice immunized intranasally or intravaginally with HSV-2+CAP. Also, the results of our in vivo experiments indicated that mice vaccinated with HSV-2+CAP were protected against live HSV-2 infection. In conclusion, these preclinical data support the hypothesis that CAP may be an effective mucosal adjuvant that protects against viral infection.

Figures

FIG. 1.

Groups of five female BALB/c mice were immunized on days 0 and 7 by intranasal or intravaginal delivery of PBS (vertically striped bars), CAP alone (open bars), HSV-2 alone (horizontally striped bars), or HSV-2+CAP (solid bars). The antigen concentration and vaginal lavage fluid dilution used in the ELISA were 100 μg/ml and 1:1, respectively.

FIG. 2.

The antigen concentration and antibody dilution used in the IgG ELISA were 6 μg/ml and 1:200, respectively. The antigen concentration and antibody dilution used in the IgG2a ELISA were 100 μg/ml and 1:50, respectively. Each bar represents the group mean antibody level for mice immunized intranasally or intravaginally with PBS (vertically striped bars), CAP alone (open bars), HSV-2 alone (horizontally striped bars), or HSV-2+CAP (solid bars).

FIG. 3.

Five BALB/c mice per group were immunized intranasally or intravaginally with PBS (vertically striped bars), CAP alone (open bars), HSV-2 alone (horizontally striped bars), or HSV-2+CAP (solid bars) and challenged intravaginally with 106 PFU of HSV-2 at 43 days after the last immunization. Clinical pathology was scored as described in the text. The stars indicate P values of <0.05 for HSV-2+CAP versus PBS, CAP alone, and HSV-2 alone.