Lack of evidence of conserved lentiviral sequences in pigs with post weaning multisystemic wasting syndrome

In order to investigate the role of retroviruses in the recently described porcine postweaning multisystemic wasting syndrome (PMWS) serum and leukocy tes were screened for reverse transcriptase (RT) activity, and tissues were examined for the presence of conserved lentiviral sequences using degenera te primers in a polymerase chain reaction (PCR), Serum and stimulated leuko cytes from the blood and lymph nodes from pigs with PMWS, as well as from c ontrol pigs had RT activity that was detected by the sensitive Amp-RT assay . A 257-bp fragment was amplified from DNA from the blood and bone marrow o f pigs with PMWS, This fragment was identical in size to conserved lentivir al sequences that were amplified from plasmids containing DNA from several lentiviruses, Cloning and sequencing of the fragment from affected pigs, ho wever, did not reveal homology with the recognized lentiviruses, Together t he results of these analyses suggest that the RT activity present in tissue s from control and affected pigs is the result of endogenous retrovirus exp ression, and that a lentivirus is not a primary pathogen in PMWS.