Effects of glycosylation on antigenicity and immunogenicity of classical swine fever virus envelope proteins

Classical swine fever virus (CSFV) harbors three envelope glycoproteins (Erns, E1 and E2). Previous studies have demonstrated that removal of specific glycosylation sites within these proteins yielded attenuated and immunogenic CSFV mutants. Here we analyzed the effects of lack of glycosylation of baculovirus-expressed Erns, E1, and E2 proteins on immunogenicity. Interestingly, Erns, E1, and E2 proteins lacking proper post-translational modifications, most noticeable lack of glycosylation, failed to induce a detectable virus neutralizing antibody (NA) response and protection against CSFV. Similarly, no NA or protection was observed in pigs immunized with E1 glycoprotein. Analysis of Erns and E2 proteins with single site glycosylation mutations revealed that detectable antibody responses, but not protection against lethal CSFV challenge is affected by removal of specific glycosylation sites. In addition, it was observed that single administration of purified Erns glycoprotein induced an effective protection against CSFV infection.

► Immunogenicity of CSFV envelope proteins is affected by deglycosylation.
► Complete deglycosylation of Erns and E2 results in non-immunogenic proteins.
► Neutralizing epitopes in Erns and E2 proteins depend on correct glycosylation.
► Purified Erns glycoprotein induces protective immunity in swine against CSFV.