CMV gB genotypes and outcome of vertical transmission: study on dried blood spots of congenitally infected babies

Background: The role of the virulence of the infecting cytomegalovirus (CMV ) strain in the transmission of the virus from mother to fetus and the outc ome of the fetal infection has not received much attention yet. Molecular a nalysis of the gene coding for the surface glycoprotein B (gB) has been use d to investigate the relationship between genotype and virulence in groups of immunosuppressed, patients. Objectives: (1) to assess the prevalence of different gB genotypes in babies with congenital CMV infection; (2) to inve stigate the possible relationship between genotype and severity of congenit al CMV disease; (3) to evaluate the possibility of using dried blood on Gut hrie cards (DBS) for genotyping. Study design: CMV DNA was extracted from D BS and From urine/saliva samples collected in the first two weeks of life o f 98 congenitally infected babies, half of which were symptomatic at birth. Genotyping was performed through RFLP analysis of the region corresponding to the cleavage site of the gB protein. Results: The most prevalent genoty pe was gB1 (42%) followed by gB3 (26%), gB2 (19%) and gB4 (13%). Rates of d isease and CNS damages were higher among children infected by gB1 (35%, 17% ) and gB3 (31%, 28%) than in those infected by gB2 and gB4 (20%, 17% and 13 %, 15%, respectively). These differences however did not reach the statisti cal significance. The parallel typing of DBS and urine/saliva strains gave a full concordance of results. Conclusions: All four major CMV gB genotypes (gB1-4) can cause a congenital infection but none seems to be associated t o the development and the severity of disease. The possibility of using the neonatal DBS for genotyping opens a way to the examination of large number s of cases of congenital CMV infection. (C) 2001 Elsevier Science B.V. All rights reserved.