Immunogenicity of a recombinant adenovirus expressing porcine reproductive and respiratory syndrome virus polyepitopes.

The objective of this work was to evaluate the immunogenicity of a chimeric antigen containing characterized PRRSV epitopes. A synthetic gene, designated HEJ, encoding defined epitopes was used to generate a recombinant adenovirus designed Ad-HEJ. The chimeric antigen included T-cell epitopes from structural and nonstructural proteins, and a neutralizing B-cell epitope. Following a homologous prime-boost immunization, the Ad-HEJ virus elicited significant (p<0.05) epitope-specific IFN-γ responses compared to sham-treatment. Two weeks post-challenge, this response was significantly (p<0.05) higher compared to the negative control treatment. IFN-γ response to PRRSV stimulation in vitro were observed in both groups only after challenge. Antibodies against PRRSV and peptides were detectable following prime-boost immunization in the Ad-HEJ treatment group and the responses increased post-challenge against the virus and against most of the peptides. All the swine were viremic one week post-challenge, but four weeks later, five out of the seven Ad-HEJ vaccinees had cleared the PRRSV, whereas only two of the six negative controls had cleared the virus. The outcome suggests that the adenovirus expressing defined epitopes induced a strong immune response against the peptides, but this response was not sufficient to confer protection against PRRSV challenge.

Immune Response of Multiparous Hyper-Immunized Sows against Peptides from Non-Structural and Structural Proteins of PRRSV.

The purpose of this study was to evaluate the humoral and cellular responses of commercial multiparous and hyper-immunized sows against peptides from non-structural (nsp) and structural proteins of porcine reproductive and respiratory syndrome virus (PRRSV). We selected sows with different numbers of parities from a commercial farm. Management practices on this farm include the use of the MLV commercial vaccine four times per year, plus two vaccinations during the acclimation period. The humoral response was evaluated via the antibody recognition of peptides from nsp and structural proteins, and the cellular response was assessed by measuring the frequency of peptide and PRRSV-specific IFN-gamma-secreting cells (IFNγ-SC). Our results show that sows with six parities have more antibodies against peptides from structural proteins than against peptides from nsp. The analysis of the cellular response revealed that the number of immunizations did not affect the frequency of IFNγ-SC and that the response was stronger against peptides from structural proteins (M protein) than against nsp (nsp2). In summary, these results demonstrate that multiparous, hyper-immunized sows have a stronger immune humoral response to PRRSV structural peptides than nsp, but no differences in IFNγ-SC against the same peptides were observed.

Immunological features of the non-structural proteins of porcine reproductive and respiratory syndrome virus.

Porcine reproductive and respiratory syndrome virus (PRRSV) is currently one of the most important viruses affecting the swine industry worldwide. Despite the large number of papers published each year, the participation of non-structural proteins (nsps) in the immune response is not completely clear. nsps have been involved in the host innate immune response, specifically, nsp1α/ß, nsp2, nsp4 and nsp11 have been associated with the immunomodulation capability of the virus. To date, only participation by nsp1, nsp2, nsp4 and nsp7 in the humoral immune response has been reported, with the role of other nsps being overlooked. Furthermore, nsp1, nsp2, nsp5, nsp7 nsp9, nsp10, nsp11 have been implicated in the induction of IFN-γ and probably in the development of the cell-mediated immune response. This review discusses recent reports involving the participation of nsps in the modulation of the innate immune response and their role in the induction of both the humoral and cellular immune responses.