RFLP 1-7-4, variant 1C.5 (aka L1C-4-4), or 1C.5.32 – these are some of the infamous PRRSV-2 viruses that have caused massive production losses over the past decade. Regardless of how people named or classified them, one thing these epidemic waves had in common was that they were caused by genetic variants that were novel at the time, and vaccination, especially widely used modified-live virus commercial vaccines, failed to mitigate their spread. Many viruses are in an arms-race with host immunity, evolving to evade host immune mechanisms. The less-than-perfect available immunization strategies combined with the expanding genetic diversity seen for PRRSV-2 raises the question:
Does the use of MLV vaccines play a role in shaping wild-type PRRSV-2 evolution, potentially driving the emergence of new variants?
A newly published paper from the University of Minnesota1 attempted to answer that question in a controlled experimental setting to compare the evolution of PRRSV-2 through pig-to-pig infection chains under different MLV vaccination conditions.
Continue reading “Does vaccination influence PRRSV evolution?”