Genetic and splice variations of Bos taurus CD46 shift cell permissivity to BVDV, the bovine pestivirus

Abstract

The pestivirus bovine viral diarrhea virus (BVDV) is known to bind to the CD46 molecule, which subsequently promotes entry of the virus. Mapping of the BVD-virion-binding site has shown that two peptides, 66EQIV69 and 82GQVLAL87, located on antiparallel beta sheets in the most distal complement control protein module (CCP1), provide the attachment platform. In the present study, we reveal the existence of ten distinct allelic versions of the CCP1 module, varying significantly in frequency among taurine and indicine races. A complex mRNA splicing pattern was also evidenced for bovine CD46, generating three different serine-threonine-proline segments and five different cytoplasmic domains. The four most frequent allelic variants and the six splice variants were then expressed in BVDV-nonpermissive porcine cells and the quantity of progeny virions generated by each cell preparation was measured 48 h post-infection. As expected, ectopic expression of the 10 bovine CD46 isoforms rendered the PK15 cells permissive to BVDV, as attested by the 100,000-fold greater recovery of virions from these cells than from non-transfected cells. This permissivity increase was significantly lower (-33%, P<0.001) when the canonical CCP1 was replaced with the variant most frequent in zebus, suggesting positive or negative selection of this allele in the latter and in the former, respectively. The predicted secondary structure of this variant suggests that the measured loss of function is due to the disappearance of one of the two beta sheets constituting the BVDV attachment platform. On the other hand we showed that for a given CCP1, the titer recovered at 48 hpi also depended on the nature of the CD46 cytoplasmic domain (P<0.001). This result implies that virus binding generates a cytoplasmic-tail-dependent outside-in signal that determines permissivity to BVDV.

The molecular pathways underlying host resistance and tolerance to pathogens

“…The bovine viral diarrhea virus (BVDV) employs the bovine CD46 cell surface molecule, a member of the complement regulatory receptors, to gain entry to cells (Maurer et al, 2004). Recently, genetic variants in bovine CD46 have been shown to influence cell permissiveness for BVDV, at least in vitro (Zezafoun et al, 2011), and thus carriers of CD46 alleles might vary in resistance to BVDV.…”

A SNP in intron 8 of CD46 causes a novel transcript associated with mastitis in Holsteins

“…The STP region is variable, and encoded by three exons (A, B, C) which are commonly expressed as B + C or C isoforms. One of two non-homologous alternative cytoplasmic tails (cyt-1 or cyt-2) resulting from alternative splicing contains signaling motifs which drive the differential processing of isoforms [17, 18]. CD46 belongs to the family of regulators of complement activation, and cleaves complement factors C3b and C4b to protect normal cells from complement-mediated damage [19, 20].…”

Entry of Classical Swine Fever Virus into PK-15 Cells via a pH-, Dynamin-, and Cholesterol-Dependent, Clathrin-Mediated Endocytic Pathway That Requires Rab5 and Rab7

“…Although in-depth studies regarding the route of pestivirus entry are still lacking, it is believed that pestiviruses enter host cells by receptor-mediated endocytosis (12)(13)(14). Heparan sulfate and CD46 have been suggested to be cellular receptors for tissue culture-adapted BVDV and CSFV (15)(16)(17). Recently, the laminin receptor (LamR) was reported to be an additional attachment receptor for CSFV (18).…”