T Cells Boost Vaccine Effectiveness Against PRRS Virus in Pigs

Research released in the journal Vaccine reveals that the effectiveness of vaccines against porcine reproductive and respiratory syndrome virus (PRRSV) is largely driven by T cell responses rather than the production of neutralizing antibodies. This finding provides critical insights into vaccine development for a virus known for its rapid mutation rate and significant financial impact on the pork industry, which incurs losses exceeding $1 billion annually due to PRRSV.

The study, led by Michael Rahe, an assistant professor at North Carolina State University, highlights the need for vaccines that can effectively target the evolving strains of PRRSV. Current vaccines do offer some protection; however, the virus’s ability to mutate quickly means that the antibodies produced are often mismatched to the circulating strains. Rahe explained, “PRRSV is one of the fastest mutating RNA viruses in the veterinary world. Neutralizing antibodies developed from vaccination typically do not match circulating strains.”

To assess the immune response to PRRSV, researchers examined four groups of pigs: an unvaccinated control group, an unvaccinated group challenged with PRRSV, a vaccinated group receiving one of the commonly used vaccines, and a group receiving a combination vaccine that included protection against porcine circovirus 2. By employing advanced detection techniques, the study measured both the viral infection and the immune response.

The results showed that all vaccinated groups exhibited elevated PRRSV-specific T cell responses in their blood, alongside reduced levels of the virus in both blood and lung tissues. Notably, this protective effect occurred in the absence of neutralizing antibodies against the specific PRRSV strain used for infection. Rahe stated, “What this tells us is that T cells are doing the heavy lifting here. Our current vaccines are successful in helping the body identify and attack pieces of the PRRSV virus that are conserved and not mutating.”

This research establishes a foundational understanding necessary for the development of more effective vaccines against PRRSV. Rahe emphasized the importance of targeting specific components of the virus that remain stable, which could lead to the production of broadly effective vaccines in the future.

The study was supported by Boehringer Ingelheim Animal Health, Inc., and Andrew Noel, a former graduate student at Iowa State University, is the first author. Other contributors from Iowa State University include Jianqiang Zhang, Baoqing Guo, Jennifer Groeltz-Thrush, Emily Rahe, and Teerawut Nedumpun. Additional assistance came from Panchan Sitthicharoenchai, an assistant professor at NC State, alongside Reid Phillips, Marius Kunze, and Oliver Gomez-Duran of Boehringer Ingelheim Vetmedica.

As the research progresses, understanding T cell responses could pave the way for innovative solutions to combat the challenges posed by PRRSV and enhance the resilience of the pork industry. The work signifies a crucial step in the ongoing effort to improve vaccine efficacy in the face of rapidly mutating pathogens.