Infection efficiency of PVs was the same for the ∆aglB mutant and the parent strain (average of 6.83% ± 1.4% for ∆aglB strain and 3.45% ± 1.92% for parent strain), indicating that infection is independent of N-glycosylation of the host cell envelope proteins and S-layer stability. The gene discussed is ERVW-1; the disease is infection.