The mRNA regulation of porcine double-stranded RNA-activated protein kinase gene

The presence of alpha interferon at the time of infection alters the innate and adaptive immune responses to porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome (PRRS) is one of the most devastating and costly diseases to the swine industry worldwide. Overall, the adaptive immune response to PRRS virus (PRRSV) is weak, which results in delayed elimination of virus from the host and inferior vaccine protection. PRRSV has been shown to induce a meager alpha interferon (IFN-α) response, and we hypothesized that elevated IFN-α levels early in infection would shorten the induction time and increase elements of the adaptive immune response. To test this, we measured both antibody and cell-mediated immunity in pigs after the administration of a nonreplicating human adenovirus type 5 vector expressing porcine IFN-α (Ad5-pIFN-α) at the time of PRRSV infection and compared the results to those for pigs infected with PRRSV alone. Viremia was delayed, and there was a decrease in viral load in the sera of pigs administered the Ad5-pIFN-α. Although seroconversion was slightly delayed in pigs receiving Ad5-pIFN-α, probably due to the early reduction in viral replication, little difference in the overall or neutralizing antibody response was seen. However, there was an increase in the number of virus-specific IFN-γ-secreting cells detected in the pigs receiving Ad5-pIFN-α, as well as an altered cytokine profile in the lung at 14 days postinfection, indicating that the presence of IFN-α at the time of infection can alter innate and adaptive immune responses to PRRSV.

Human αIFN co-formulated with milk derived E2-CSFV protein induce early full protection in vaccinated pigs

Subunit vaccines are a suitable alternative for the control of classical swine fever. However, such vaccines have as the main drawback the relatively long period of time required to induce a protective response, which hampers their use under outbreak conditions. In this work, type I interferon is used as an immunostimulating molecule in order to increase the immunogenicity of a vaccine candidate based on the E2-CSFV antigen produced in goat milk. Pigs vaccinated with E2-CSFV antigen co-formulated with recombinant human alpha interferon were protected against clinical signs and viremia as early as 7 days post-vaccination. It was also demonstrated that interferon stimulates a response of specific anti-CSFV neutralizing antibodies. The present work constitutes the first report of a subunit vaccine able to confer complete protection by the end of the first week after vaccination. These results suggest that the E2-CSFV antigen combined with type I interferons could be potentially used under outbreak conditions to stop CSFV spread and for eradication programs in CSF enzootic areas.

Adenovirus-mediated expression of interferon-alpha delays viral replication and reduces disease signs in swine challenged with porcine reproductive and respiratory syndrome virus

In this study, pigs were injected with a nonreplicating human adenovirus type 5 vector expressing porcine interferon-alpha (Ad5-pIFN-alpha) and then challenged with porcine reproductive and respiratory syndrome virus (PRRSV) to determine whether the presence of increased levels of IFN-alpha would decrease viral replication and/or disease. Groups of 10 pigs each were inoculated with Ad5-pIFN-alpha and not challenged, Ad5-pIFN-alpha and challenged with PRRSV 1 d later, or inoculated with a control adenovirus that does not express IFN-alpha (Ad5-null) and challenged 1 d later with PRRSV. IFN-alpha levels in all pigs inoculated with the Ad5-pIFN-alpha were elevated the day of challenge (1 d after inoculation), but were undetectable by 3 d after inoculation in the pigs that were not challenged with PRRSV. Pigs inoculated with Ad5-pIFN-alpha and challenged with PRRSV had lower febrile responses, a decreased percentage of lung involvement at 10 d post-infection, delayed viremia and antibody response, and higher serum IFN-alpha levels as a result of PRRSV infection, compared to pigs inoculated with Ad5-null and challenged with PRRSV. These results indicate that IFN-alpha can have protective effects if present during the time of infection with PRRSV.

Differences in clinical disease and immune response of pigs challenged with a high-dose versus low-dose inoculum of porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV) continues to be an economically important infectious disease of swine. Mechanisms governing activation of the innate immune response to PRRSV remain to be elucidated. Virulence differences observed between PRRSV isolates have been attributed to replication ability in vivo, though immunogenic differences likely contribute to virulence also. The current study utilized a single PRRSV isolate given at two different challenge doses to investigate the effect of viral replication and load on immune responses, including type I interferon activation. Body temperature, viral load, antibody levels, cellular infiltration into pulmonary tissue, and the interferon response were measured in animals receiving either a low (10(2) CCID(50)) or high (10(6) CCID(50)) dose of inoculum to understand the role of challenge dose in acute immune responses. Initial PRRSV dose did not correlate with serum levels of PRRSV vRNA or antibody titers during the acute stage of infection (days 2-12 PI), but did have an effect on the immune response and mortality. Type I interferon responses, measured by transcriptional changes in IFN-beta, IFN-alpha, Mx, and PKR, were uniquely different when assessed relative to viral dose or cell type, but no overall trend existed to discern responses based on challenge dose. Serum IFN-gamma levels correlated with serum viral RNA load at day 19 PI. Overall, between days 2 and 12 PI, serum vRNA load was not significantly different between pigs challenged with a low or high dose of PRRSV. Animals receiving high-dose inoculum were viremic longer and eventually succumbed to respiratory disease. IFN-gamma may play a role in PRRSV pathogenesis, as serum levels increased significantly in pigs challenged with the high dose of PRRSV.