Site-specific alteration of murine hepatitis virus type 4 peplomer glycoprotein E2 results in reduced neurovirulence

Abstract

Strains of the murine coronavirus mouse hepatitis virus type 4 (MHV-4) which contained a mutation in the E2 peplomer glycoprotein were obtained by selection for resistance to neutralization by monoclonal antibodies. Characterization of six variants representing two independent epitopes on E2, E2B and E2C, by in vitro neutralization and antibody-binding assays demonstrated that selection for an alteration in epitope E2B also resulted in changes in epitope E2C and vice versa. We observed a mutation frequency of approximately 10-4.3 to 10-4.6, which is consistent with the expected occurrence of single point mutations. The variant virus strains were attenuated with respect to neurovirulence when compared with wild-type MHV-4. Mice normally develop encephalomyelitis and die after wild-type MHV-4 infection. Mice receiving 2to 3-log-higher doses of the variant strains survived and developed demyelinating disease. As the disease progressed, evidence of remyelination and ongoing demyelination was observed up to 65 days after infection. Virus reisolated 15 days after infection retained the variant phenotype. The data indicate that the E2 glycoprotein plays a central role in determining the cellular tropism and virulence of MHV-4 in the mouse.

Coronavirus Spike Protein and Tropism Changes

“…The spike protein of MHV-JHM may induce receptor-independent fusion (Gallagher et al, 1992(Gallagher et al, , 1993. However, deletion of residues in HVR of MHV-JHM resulted in the spike protein being entirely dependent on CEACAM1a binding for fusion (Dalziel et al, 1986;Gallagher and Buchmeier, 2001;Phillips and Weiss, 2001).…”

The antiviral activity of antibodies in vitro and in vivo

“…One potently neutralizing anti-E2 mAb was not protective. However, this mAb recognizes an epitope which is subject to rapid neutralization escape (Dalziel et al, 1986), and the challenge virus may have contained escape variants of unusual fitness in vivo (M. J. Buchmeier, personal communication). Nonneutralizing anti-E1 membrane glycoprotein and anti-N nucleoprotein mAbs were nonprotective.…”

Pathogenesis of Theiler's Murine Encephalomyelitis Virus

“…Neutralizing MAbs have been used to select less neurovirulent reovirus variants (Spriggs and Fields, 1982). Similarly, neutralizationresistant coronavirus variants with an altered pathogenicity have been obtained (Fleming et al, 1986;Dalziel et al, 1986). The use of neutralization-resistant TMEV variants has been confirmed by Roos et al (1989~).…”