Date Full Report Received


Date Abstract Report Received



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Porcine reproductive and respiratory syndrome (PRRS) continues to be the most devastating disease of swine in the USA. PRRSV is the biological viral agent responsible for this disease. Here we show that PRRSV exists as a cloud of genomic variants, especially in the infected tissue, e.g. lung, of the infected animal. A reduced cloud of PRRSV strains are released into the blood stream, highlighting that the infection found and routinely monitored from serum does not give the whole picture as to the true PRRSV infection dynamic occurring in the animal. We also show that orf5, the gene that encodes GP5, does not describe the true genetic variation and thus true origin and evolutionary potential of PRRSV. The greatest genetic variation exists in the non-structural region of the virus. A large deletion in the orf1 non-structural gene of one of our isolates had no impact on the replication of this virus. In fact, this deleted PRRSV strain had a more severe pathology that the standard wild-type PRRSV strain. In addition, even the genetic variation that exist across the rest of the genome does not translate into many changes in amino acid sequence and thus protein structure and function. The greatest changes in amino acids occurs in the PRRSV sequences found in the tissue samples. This was true for both PRRSV isolates screened, irrespective of whether they produced a chronic persistent or severe infection as indicated by the differing levels of viremia produced by the two isolates. Genetic variation within animal over a small window of time (up to 14 days post infection) was less when compared between sample type. This study once again re-emphasizes the wealth of new information that can be obtained from whole genome comparative analysis.