Pathogenicity And Location Of New Receptor Positive Cells Of Porcine Reproductive And Respiratory Syndrome Virus On Two Species Pigs

Porcine reproductive and respiratory syndrome (PRRS) is now prevalence in manyswine-producing countries and continues to be an economically devastating infectious diseaseworldwide since described in the USA in1987. PRRSV has many clinical manifestations butthe two most prevalent are severe reproductive failure in sows (characterized by late-termabortions, an increased number of stillborns, mummified and weak-born pigs) and respiratoryproblems in pigs of all ages associated with a non-specific lymphomononuclear interstitialpneumonitis. PRRS is present worldwide, and the etiological agent, PRRSV, is primarilyknown for its ability to avoid host defenses and establish a long-term infection. It is alsoobvious that PRRSV isolates show considerable genetic variation, causing the currentvaccines based on a single PRRSV strain alone not or only partially effective. PRRSV entryoccurs by receptor-mediated endocytosis, but how the virus enters cells was not so sure untilnow. Are there any other proteins participated in PRRSV entry except the four acceptedreceptors? Does the distribution of the proteins vary in tissues? Is the pathogenicity ofPRRSV the same among genetically diverse lines of pigs? Searching these doubts is anessential step toward making a contribution to the understanding of the pathogenicity ofPRRSV.Landraces and Laiwu pigs were infected with PRRSV isolate in this study respectively.Data collected included histopathology observation and immunohistochemistry location ofnew receptor in main tissues infected with PRRSV or not. Blood routine examination wasmonitored after Laiwu pigs infected with PRRSV, and fluorescence quantitative PCR wasused to detect relative quantity changes of PRRSV in lungs and spleens. The results showedthat, Landraces were more susceptible to PRRSV isolate, lung lesions were characterized byserious interstitial pneumonia, other organs lesions varied distribution and severity and werecharacterized by lymphocyte infiltration. Infection caused significant immunosuppression toLandraces. The distribution of new receptor showed no difference with PRRSV in mainorgans, and no changes before or after infection with PRRSV. Tissues lesions in Laiwu pigswere slighter, characterized by mild interstitial pneumonia in lung and necrotizinginflammation in lymph nodes, while no serious lesions in other organs. The distribution ofnew receptor was the same with Landraces, but it changed obviously after infected withPRRSV in lung and immune tissues such as spleen, lymph nodes and tonsil. Blood routineexamination indicated that the number of leukocyte and lymphocyte reached peak on10dpi,then got a sharp drop, and maintained levels below normal. Highest virus load on7dpi and consecutive drop in lungs and spleens was shown by fluorescence quantitative PCR, whichsuggest Laiwu pigs may have resistance to PRRSV.All data showed that new receptor is closely involved in PRRSV entry. Laiwu pigs haveresistance of PRRSV according to changes of immune state and new receptor. This studyprovides evidence that the existence of a host genetic component in disease susceptibility toPRRSV and lays a foundation for figuring out genetic resistance or susceptibility genes ofChinese native pig breeds.