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Sera from a sample of children aged 3 months to 6 years and from cord blood were tested in an indirect immunofluorescence assay (IFA) for reactivity to human herpesviruses 6 (HHV-6) and 7 (HHV-7). HHV-6 seropositivity values rose from 19% to 79.3% in the first 18 months of life, while HHV-7 seroprevalence reached a similar value (75.9%) in children aged 3-6 years. These results show that HHV-7, like HHV-6, is a prevalent virus in infancy. In cord blood sera, assayed to study infant humoral situation at birth, similar values for the two viruses (78.9% for HHV-6 and 76.3% for HHV-7) were found. HHV-6 and HHV-7 IgG antibody affinity to the corresponding antigens was assessed by the end point antibody titration in the presence and absence of urea 8M. This test distinguishes antibodies of recent (low affinity) or past (high affinity) production. Together, the data on seroprevalence and antibody affinity suggest that HHV-6 primary infection generally precedes that by HHV-7. These results are discussed in the light of a different pathogenetic role of the two viruses.

546 human sera from healthy subjects, subjects with cytomegalovirus or Epstein-Barr virus infection and from cordal blood were tested for the human herpesvirus-6 (HHV-6) IgG content in an enzyme-linked immunosorbent assay (ELISA) to verify results previously obtained with an immunofluorescence assay (IFA). The HHV-6 isolate CV, obtained from a child with exanthem subitum, employed as antigen in both tests, belonged to HHV-6 variant B. The ELISA results were similar to those obtained with IFA. 445/546 (81.5%) sera had the same type of reactivity with the two serological procedures. To establish whether different HHV-6 strains may give different serological results, 117 out of the 546 sera tested with IFA against CV infected cells were also tested against cells infected with the HHV-6 isolate U1102 belonging to variant A. All the sera showed a similar reactivity.

Sera from a sample of healthy Italian people were tested in an indirect immunofluorescence assay (IFA) for reactivity to a Human Herpesvirus-6 (HHV-6) strain called CV, isolated from a baby with exanthem subitum (Portolani et al., 1990). Seropositivity values of 83.78%, 92.68% and 63.64% were found in subjects aged 3 months-6 years, 6-18 years and over 18 years respectively. Sera from cordal blood, sera from subjects with evidence of active infection by Cytomegalovirus (CMV) or by Epstein-Barr virus (EBV), sera from seropositive adults to Human Immunodeficiency Virus type 1 (HIV) were also investigated for antibodies to the same HHV-6 strain. Values of antibody incidence and antibody content to HHV-6 in these groups of sera were generally higher than in the other groups. HHV-6 reinfections of both endogenous and exogenous origin and antibody cross-reactivity were considered among the reasons of this increase. HHV-6 seropositivity values in healthy Italian people and in people from different countries were also discussed in the light of the antigenic characteristics of the HHV-6 strains used and of the different test conditions.

Thirty-three sera from women symptom-free for papillomatous disease and 27 sera from women with flat or exophytic genital warts were examined for the presence of IgG and IgM antibodies to papillomavirus (PV) genus-antigens. For this purpose, sera were challenged with genus-antigens extracted from both human and bovine purified virions of PVs, in a micro solid-phase enzyme-linked immunosorbent assay (ELISA). The assay performed with PV genus-antigens of human origin showed that in women with genital warts, IgG antibodies were present in a percentage of 70.37% and IgM antibodies in a percentage of 40.74%; in apparently uninfected women, IgG and IgM antibodies were present in a percentage of 54.54% and 24.24% respectively. When sera were challenged with PV genus-antigens of bovine origin for IgG antibody class, positivity was 70.37% in women with genital disease and 45.45% in symptom-free women. IgG and IgM antibody response in women with and without papillomatous genital lesions is discussed.

Sera from 1,279 patients with various diseases were examined for the presence of antibodies to BK virus (BKV) capsid antigens. The percentage of positive sera was comparable in all the diseases except rheumatoid arthritis and chronic nephropathies, where a slightly higher prevalence was found. Sera from 952 patients with tumors were examined for the presence of antibodies to BKV tumor and capsid antigens in comparison with a matched control group of 501 blood donors. Sera from 11 tumor patients (1.15%) and from 4 normal controls (0.80%) had antibodies to BKV tumor antigen. No higher prevalence of antibodies to BKV capsid antigens was found in any cancer type except in carcinomas of the urinary bladder, where the percentage of positive sera and of sera with high titers was higher than in other groups. BKV infection is discussed in relation to its possible connection with human non-neoplastic diseases as well as with human tumors and to its activation under conditions of immunosuppressive therapy.