Identification and location of the structural glycoproteins of a tissue culture-adapted turkey enteric coronavirus

A conditional-lethal murine coronavirus mutant that fails to incorporate the spike glycoprotein into assembled virions

The coronavirus spike glycoprotein (S) mediates both the attachment of virus to the host cell receptor and membrane fusion. We describe here the characterization of a temperature-sensitive mutant of the coronavirus mouse hepatitis virus A59 (MHV-A59) having multiple S protein-related defects. The most remarkable of these was that the mutant, designated Albany 18 (Alb18), assembled virions devoid of the S glycoprotein at the nonpermissive temperature. Alb18 also failed to bring about syncytia formation in cells infected at the nonpermissive temperature. Virions of the mutant assembled at the permissive temperature were much more thermolabile than wild type. Moreover, mutant S protein that was incorporated into virions at the permissive temperature showed enhanced pH-dependent thermolability in its ability to bind to the MHV receptor. Alb18 was found to have a single point mutation in S resulting in a change of serine 287 to isoleucine, and it was shown by revertant analysis that this was the lesion responsible for the phenotype of the mutant.

Recent advances in avian virology

Selected, recent research on the following avian diseases, and their causative viruses, has been reviewed: chicken anaemia, infectious bursal disease, turkey rhinotracheitis, avian nephritis, fowlpox, influenza, infectious bronchitis and turkey enteritis.

The S protein of bovine coronavirus is a hemagglutinin recognizing 9-O-acetylated sialic acid as a receptor determinant

The S protein of bovine coronavirus (BCV) has been isolated from the viral membrane and purified by gradient centrifugation. Purified S protein was identified as a viral hemagglutinin. Inactivation of the cellular receptors by sialate 9-O-acetylesterase and generation of receptors by sialylation of erythrocytes with N-acetyl-9-O-acetylneuraminic acid (Neu5,9Ac2) indicate that S protein recognizes 9-O-acetylated sialic acid as a receptor determinant as has been shown previously for intact virions. The second glycoprotein of BCV, HE, which has been thought previously to be responsible for the hemagglutinating activity of BCV, is a less efficient hemagglutinin; it agglutinates mouse and rat erythrocytes, but in contrast to S protein, it is unable to agglutinate chicken erythrocytes, which contain a lower level of Neu5,9Ac2 on their surface. S protein is proposed to be responsible for the primary attachment of virus to cell surface. S protein is proposed to be responsible for the primary attachement of virus to cell surface receptors. The potential of S protein as a probe for the detection of Neu5,9Ac2-containing glycoconjugates is demonstrated.

Hemagglutinating encephalomyelitis virus attaches to N-acetyl-9-O-acetylneuraminic acid-containing receptors on erythrocytes: comparison with bovine coronavirus and influenza C virus

The receptors for the hemagglutinating encephalomyelitis virus (HEV, a porcine coronavirus) on chicken erythrocytes were analyzed and compared to the receptors for bovine coronavirus (BCV) and influenza C virus. Evidence was obtained that HEV requires the presence of N-acetyl-9-O-acetylneuraminic acid (Neu5,9Ac2) on the cell surface for agglutination of erythrocytes as has been previously shown for BCV and influenza C virus: (i) Incubation of red blood cells with sialate 9-O-acetylesterase, the receptor-destroying enzyme of influenza C virus, rendered the erythrocytes resistant against agglutination by each of the three viruses; (ii) Human erythrocytes which are resistant to agglutination by HEV acquire receptors for HEV after resialylation with Neu5,9Ac2. Sialylation of red blood cells with limiting amounts of sialic acid indicated that strain JHB/1/66 of influenza C virus requires less Neu5,9Ac2 for agglutination of erythrocytes than the two coronaviruses, both of which were found to be similar in their reactivity with Neu5,9Ac2-containing receptors.