Siao-Kun Wan Welch

CD163 Expression Confers Susceptibility to Porcine Reproductive and Respiratory Syndrome Viruses

ABSTRACT Direct functional screening of a cDNA expression library derived from primary porcine alveolar macrophages (PAM) revealed that CD163 is capable of conferring a porcine reproductive and respiratory syndrome virus (PRRSV)-permissive phenotype when introduced into nonpermissive cells. Transient-transfection experiments showed that full-length CD163 cDNAs from PAM, human U937 cells (histiocytic lymphoma), African green monkey kidney cells (MARC-145 and Vero), primary mouse peritoneal macrophages, and canine DH82 (histocytosis) cells encode functional virus receptors. In contrast, CD163 splice variants without the C-terminal transmembrane anchor domain do not provide PRRSV receptor function. We established several stable cell lines expressing CD163 cDNAs from pig, human, and monkey, using porcine kidney (PK 032495), feline kidney (NLFK), or baby hamster kidney (BHK-21) as the parental cell lines. These stable cell lines were susceptible to PRRSV infection and yielded high titers of progeny virus. Cell lines were phenotypically stable over 80 cell passages, and PRRSV could be serially passed at least 60 times, yielding in excess of 105 50% tissue culture infective doses/ml.

A brief review of CD163 and its role in PRRSV infection.

Porcine reproductive and respiratory syndrome virus (PRRSV) infects fully differentiated cells of the monocyte/macrophage lineage. Recently, CD163 was shown to be a cellular receptor capable of mediating infection of otherwise PRRSV non-permissive cell lines. CD163 is a macrophage differentiation antigen belonging to the scavenger receptor cysteine-rich (SRCR) family of membrane proteins. We provide a brief review of current knowledge regarding CD163 in relation to PRRSV infection, and propose a structure-based prediction of amino acid sequences involved in PRRSV interaction.

Construction of chimeric bovine viral diarrhea viruses containing glycoprotein Erns of heterologous pestiviruses and evaluation of the chimeras as potential marker vaccines against BVDV

Bovine viral diarrhea virus (BVDV) infections are enzootic in the cattle population and continue to cause significant economic losses to the beef and dairy industries worldwide. Extent of the damages has stimulated increasing interest in control programs directed at eradicating BVDV infections. Use of a BVDV marker vaccine would facilitate eradication efforts as a negatively marked vaccine would enable differentiation of infected from vaccinated animals (DIVA). We describe here the construction of three chimeric BVDVs containing glycoprotein E(rns) of heterologous pestiviruses and the evaluation of the chimera viruses as potential marker vaccines against BVDV infections. Chimeric NADL/G-E(rns), NADL/R-E(rns), and NADL/P-E(rns) were constructed by replacing the E(rns) gene of the full-length BVDV (NADL strain) genome with the E(rns) genes of giraffe (G-E(rns)), reindeer (R-E(rns)), or pronghorn antelope (P-E(rns)) pestiviruses, respectively. Each chimeric NADL virus was viable and infectious in RD 420 (bovine testicular) and BK-6 (bovine kidney) cells. By immunohistochemistry assays, NADL/G-E(rns) and NADL/R-E(rns) chimeric viruses reacted to BVDV E(rns) specific monoclonal antibody (mAb) 15C5, whereas the NADL/P-E(rns) chimeric virus did not. In an animal vaccination study, inactivated vaccines made from two chimeric viruses and the wild type NADL BVDV induced similar neutralizing antibody responses. NADL/P-E(rns)-vaccinated animals were distinguished from animals vaccinated with the wild type virus by means of a companion serological DIVA assay. These results show that chimeric NADL/P-E(rns) virus containing the E(rns) gene of pronghorn antelope pestivirus could be a potential marker vaccine candidate for use in a BVDV control and eradication program.