Fusion-Expressed CTB Improves Both Systemic and Mucosal T-Cell Responses Elicited by an Intranasal DNA PrimingIntramuscular Recombinant Vaccinia Boosting Regimen

Abstract EN

Previous study showed that CTB (Cholera toxin subunit B) can be used as a genetic adjuvant to enhance the systemic immune responses.

To further investigate whether it can also be used as a genetic adjuvant to improve mucosal immune responses, we constructed DNA and recombinant Tiantan vaccinia (rTTV) vaccines expressing OVA-CTB fusion antigen.

Female C57BL/6 mice were immunized with an intranasal DNA priming/intramuscular rTTV boosting regimen.

OVA specific T-cell responses were measured by IFN-γ ELISPOT and specific antibody responses were determined by ELISA.

Compared to the nonadjuvant group (pSV-OVA intranasal priming/rTTV-OVA intramuscular boosting), pSV-OVA-CTB intranasal priming/rTTV-OVA-CTB intramuscular boosting group significantly improved the magnitudes of T-cell responses at spleen (1562±567 SFCs/106 splenocytes versus 330±182 SFCs/106 splenocytes, P<0.01), mesenteric LN (96±83 SFCs/106 lymphocytes versus 1±2 SFCs/106 lymphocytes, P<0.05), draining LNs of respiratory tract (109±60 SFCs/106 lymphocytes versus 2±2 SFCs/106 lymphocytes, P<0.01) and female genital tract (89±48 SFCs/106 lymphocytes versus 23±21 SFCs/106 lymphocytes, P<0.01).

These results collectively demonstrated that fusion-expressed CTB could act as a potent adjuvant to improve both systemic and mucosal T-cell responses.