RESUMO
This study was designed to evaluate the prime-boost vaccination regimens as a novel immunization strategy for DNA vaccine against classical swine fever virus (CSFV). BALB/c mice were primed with the alphavirus replicon-vectored DNA vaccine pSFV1CS-E2-UL49 encoding the E2 protein of CSFV fused with the UL49 gene encoding the transduction protein VP22 of pseudorabies virus, followed by either homologous boosting with pSFV1CS-E2-UL49 or heterologous boosting with the recombinant adenovirus rAdV-E2 expressing the E2 protein or with the baculovirus-produced recombinant E2 protein (rE2) in adjuvant. The humoral and cell-mediated immune responses following prime-boost vaccination were assessed. The results showed that: (1) boosting with either rAdV-E2 or rE2 elicited high-level antibodies, whereas homologous boosting with pSFV1CS-E2-UL49 elicited low-level antibodies (below positive threshold); (2) heterologous boosting with rAdV-E2 resulted in stronger CD8(+) and CD4(+) T cells proliferation responses and higher stimulation indexes; and (3) heterologous boosting with rAdV-E2 induced more IFN-gamma production. These results support the notion that a regimen of DNA prime-recombinant adenovirus boost enhances humoral and cell-mediated immune responses, and the DNA prime-protein boost regimen enhances humoral immune responses.
Assuntos
Vírus da Febre Suína Clássica/imunologia , Vacinas de DNA/administração & dosagem , Vacinas Virais/administração & dosagem , Adenoviridae/genética , Alphavirus/genética , Animais , Anticorpos Antivirais/biossíntese , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Peste Suína Clássica/imunologia , Peste Suína Clássica/prevenção & controle , Vírus da Febre Suína Clássica/genética , Feminino , Genes Virais , Vetores Genéticos , Herpesvirus Suídeo 1/genética , Imunidade Celular , Imunidade Humoral , Imunização Secundária , Interferon gama/biossíntese , Interleucina-4/biossíntese , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos BALB C , Replicon , Sus scrofa , Vacinas de DNA/genética , Proteínas Estruturais Virais/genética , Proteínas Estruturais Virais/imunologia , Vacinas Virais/genéticaRESUMO
We have previously shown that an alphavirus replicon-vectored DNA vaccine (pSFV1CS-E2) encoding the E2 glycoprotein of classical swine fever virus (CSFV) completely protected the immunized pigs from lethal challenge. These animals developed only low or moderate level viral-specific antibody titers before challenge, implying that cell-mediated immunity (CMI) probably played an important role in the protective immunity against CSFV conferred by the DNA vaccine. In this study, the CMI induced by pSFV1CS-E2 and its derivative pSFV1CS-E2-UL49 encoding a fusion protein of CSFV E2 and pseudorabies virus (PRV) VP22 was evaluated in a mouse model by lymphoproliferation assays based on CFSE or WST-8, intracellular cytokine staining, and cytokine ELISA. The results showed that both vaccines induced CSFV-specific lymphoproliferative responses and cytokine production, and pSFV1CS-E2-UL49 induced stronger lymphoproliferative responses and higher cytokine levels than pSFV1CS-E2. These findings suggest that the alphavirus replicon-delivered DNA vaccines are capable of inducing CMI, and PRV VP22 is able to enhance the immunogenicity of the co-delivered antigen.
