Enhancing mucosal immunity in mice by recombinant adenovirus expressing major epitopes of porcine circovirus-2 capsid protein delivered with cytosine-phosphate-guanosine oligodeoxynucleotides.

A recombinant replication-defective adenovirus expressing the major epitopes of porcine circovirus-2 (PCV-2) capsid protein (rAd/Cap/518) was previously constructed and shown to induce mucosal immunity in mice following intranasal delivery. In the present study, immune responses induced by intranasal immunization with a combination of rAd/Cap/518 and cytosine-phosphate-guanosine oligodeoxynucleotides (CpG ODN) were evaluated in mice. The levels of PCV-2-specific IgG in serum and IgA in saliva, lung, and intestinal fluids were significantly higher in the group immunized with rAd/Cap/518 and CpG ODN than animals immunized with rAd/Cap/518 alone. The frequencies of IL-2-secreting CD4⁺ T cells and IFN-γ-producing CD8⁺ T cells were significantly higher in the combined immunization group than mice immunized with rAd/Cap/518 alone. The frequencies of CD3⁺, CD3⁺CD4⁺CD8⁻, and CD3⁺CD4⁻CD8⁺ T cells in the combined immunization group were similar to that treated with CpG ODN alone, but significantly higher than mice that did not receive CpG ODN. PCV-2 load after challenge in the combined immunization group was significantly lower than that in the phosphate-buffered saline placebo group and approximately 7-fold lower in the group treated with CpG ODN alone. These results indicate that rAd/Cap/518 combined with CpG ODN can enhance systemic and local mucosal immunity in mice, and represent a promising synergetic mucosal vaccine against PCV-2.

Induction of mucosal immunity by intranasal immunization with recombinant adenovirus expressing major epitopes of Porcine circovirus-2 capsid protein.

Porcine circovirus-2 (PCV-2) is primarily transmitted through mucosa, thus the mucosal immunity may constitute an essential feature of vaccination strategies against PCV-2 infection. Mucosal immunity elicited by recombinant replication-deficient adenovirus expressing the major epitopes of PCV-2 capsid protein (rAd/Cap/518) via intranasal (i.n.), intramuscular (i.m.) or oral routes in mice were evaluated. Immunization with rAd/Cap/518 via i.n. route induced higher titers of IgA in saliva, bronchoalveolar and intestinal lavage fluid compared with those immunized via i.m. route. The proportions of CD3+, CD3+CD4+ and CD3+CD8+ T cells were significantly increased in mice immunized with rAd/Cap/518 via i.n. route compared with the control group. Higher levels of IFN-γ were detected in the spleen and mesenteric lymph nodes of mice immunized with rAd/Cap/518 via i.n. route compared with other groups, yet IL-4 was not detected in any group. Real-time PCR analysis confirmed viral DNA loads in the i.m. or i.n. immunization group was lower than that seen in the rAd immunization. These results indicate that i.n. administration of rAd/Cap/518 can elicit humoral and Th1-type cellular protective immunity in both systemic and mucosal immune compartments in mice, representing a promising mucosal vaccine candidate against PCV-2.