Characterization of the guinea pig CMV gH/gL/GP129/GP131/GP133 complex in infection and spread

• We report the re-evaluation of the GP129-133 locus from GPCMV.
• We report the characterization of GP133, a homolog of HCMV UL131A.
• The GP129-133 proteins form a pentamer complex with the glycoproteins gH and gL.
• GP129-133 proteins play a role in viral entry into endothelial and fibroblast cells.
• The GP129-133 deletion strain fails to spread in vivo.

In human cytomegalovirus (HCMV), the UL128-131A locus plays an essential role in cellular tropism and spread. Here, we report the complete annotation of the GP129-133 locus from guinea pig cytomegalovirus (GPCMV) and the discovery of the UL131A homolog, named GP133. We have found that similar to HCMV the GP129-133 proteins form a pentamer complex with the GPCMV glycoproteins gH and gL. In addition, we find that the GP129-133 proteins play a critical role in entry as the GP129-133 deletion mutant shows a defect in both endothelial and fibroblast cell entry. Although the GP129-133 deletion strain can propagate in vitro, we find that the deletion fails to spread in vivo. Interestingly, the wildtype strain can spontaneously give rise to the GP129-133 deletion strain during in vivo spread, suggesting genetic instability at this locus.