In vivo evaluation of a candidate live marker vaccine for porcine reproductive and respiratory syndrome virus.

摘要

Porcine reproductive and respiratory syndrome virus (PRRSV) continues to be a major problem in the pork industry worldwide. The limitations of current PRRSV vaccines require the development of a new generation of vaccines. One of the key steps in future vaccine development is to include markers for diagnostic differentiation of vaccinated animals from those naturally infected with wild-type virus.;Using a cDNA infectious clone of Type 1 PRRSV SD01-08, we have constructed a recombinant green fluorescent protein (GFP) tagged PRRSV containing deletion of an immunogenic epitope, ES4, in the Nsp2 region. We hypothesize that immunization of pigs with the marker virus will go without noticeable clinical symptoms, and subsequent inoculation with a different more virulent strain could show that vaccination can prevent disease by the challenge virus. We performed the in vivo study in a nursery pig disease model, found the recombinant virus was attenuated with a lower level of viremia, but induced a higher level of neutralizing antibody response in comparison to that of parental virus. To compliment the marker identification, we developed GFP and ES4 epitope-based ELISAs. Pigs immunized with the recombinant virus lacked antibodies directed against the corresponding deleted epitope ES4, while generating a high level of antibody response to GFP starting at 14 days post-infection.;Our results demonstrated that this recombinant marker virus, in conjunction with a diagnostic test, enables serological differentiation of vaccinated animals from naturally infected animals. This rationally designed marker virus will provide a basis for further development of PRRSV marker vaccines to assist PRRSV eradication programs.