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Graduate Student Expo 2011

 Anisha Misra, MS candidate
Effect of variation in PRRSV N-glycosylation site in GP5 on virus neutralization
Advisor:  W. Laegreid

The ectodomain of glycoprotein 5 in PRRSV has a neutralization epitope which is flanked by three N-linked glycosylation sites, N34, N44 and N51. It is believed that these glycosylation sites play a role in glycan shielding which is a primary mechanism by which the virus evades neutralizing immune responses. Analysis of GP5 sequences of a subset of field strains showed that the N34 glycosylation site can shift to N33 or N35. Comparing these variations to the virus neutralization titers, we observed that the closer the glycosylation site (N35) was to the epitope,  the virus neutralizing titer was significantly lower than when the glycosylation site was further away (N33).  We hypothesized that ….The purpose of this study was to study the association between the variation in glycosylation site and its effects on virus neutralization and fitness. Mutations carrying the change in glycosylation site at N33, N34 and N35 were introduced into a full length cDNA clone. Western Blots confirmed that predicted glycosylated sites were in fact glycosylated. Serum neutralization assays were performed on glycosylation variant FL-12 constructs using antiserum raised against N34 FL-12. Variation in  location of the glycosylation site on the amino terminal side of the putative GP5 neutralization epitope explains some of the variation in neutralization of field strains and be a novel mechanism by which viruses adapted to serologic selection.