Background: Antibodies with functional anti-Human Cytomegalovirus (HCMV) activity are likely to be involved in preventing virus dissemination and thus may contribute to minimize the clinical manifestations of infection.
Objectives: To investigate the role of humoral immunity in modulating the clinical expression of primary Human Cytomegalovirus (HCMV) infection in immunocompetent persons.
Study design: Neutralizing (NA) and glycoprotein B (gB)-specific antibodies were quantitated in acute-phase and late-convalescence phase sera from 19 individuals who developed either HCMV mononucleosis (12) or oligosymptomatic hepatitis (seven).
Results: The levels of NA in sera drawn early after infection were significantly lower in the former patients than in the latter (P=0. 032). This difference was not related to either the total serum IgG levels and anti-HCMV IgGs avidity or to the presence of higher viral loads in blood, as assessed by detecting serum HCMV DNA by PCR, in patients experiencing mononucleosis. Increased NA titers were seen in all available late-convalescence sera. In these sera, median NA levels were not significantly different among the study groups. Antibodies to HCMV gB of both IgG and IgM classes were detected in all acute-phase sera analyzed. Median anti-gB IgG and IgM titers did not differ significantly between study groups. Likewise, the IgG subclass reactivity pattern against gB was found to be similar for both groups.
Conclusions: The data revealed that an intense and early antibody response to gB developed in patients undergoing primary HCMV infection irrespective of the clinical manifestation of the disease. In contrast, a deficient NA response was observed in patients with HCMV mononucleosis versus that observed in patients displaying a milder form of disease-suggesting that the strength of NA response to HCMV generated early after infection might determine the severity of primary HCMV infection.