Intrauterine cytomegalovirus infection and glycoprotein N (gN) genotypes

Human cytomegalovirus (HCMV) clinical isolates display genetic polymorphisms, supposed to be related with strain-specific tissue-tropism and HCMV-induced immunopathogenesis. One recently discovered polymorphic gene is ORF UL73, encoding for the envelope glycoprotein gN. Among HCMV clinical strains, it shows four distinct genomic variants denoted as gN-1, gN-2, gN-3 and gN-4.

Aims of this study were to assess the prevalence of the different gN types in the populations examined and to investigate the possible relationship between genotypes and severity of congenital CMV disease.

The gN genotyping was carried out by sequencing analysis of the HCMV ORF UL73. Comparisons were made by chi-square test and contingency tables.

All the four gN genotypes can cause congenital infections and the overall distribution was as follows: gN-1, 23.6%; gN-2, 1.1%; gN-3, 12.9%; gN-4, 62.4%. None of them seems to be preferentially associated with vertical transmission or with acute outcome of congenital infection. However, considering the chronic outcome and long-term sequelae, there was a statistically significant (P<0.05) difference between congenitally infected infants with or without adverse chronic outcome.

HCMV congenital infections, which displayed a prevalence of the gN-1 variants, seem to be associated with favorable chronic outcome.