The pattern of free and antibody-complexed HIV antigen and the antibody profile were investigated retrospectively in 305 serum samples taken from 22 AIDS patients before and during the development of AIDS and from 40 apparently healthy seropositive individuals. Most AIDS patients were found positive for both free and complexed antigen and had high gp41 antibody titres but low or undetectable p24 antibody. Four different patterns of HIV antigenaemia were observed: 1) positive for both free and complexed antigen; 2) negative for free HIV antigen at first, but always positive for complexed antigen; 3) positive for free antigen without complexed antigen; and 4) negative for both free and complexed antigen. The development of immune complexes preceded the appearance of free antigen and might reflect the ongoing viral replication with antigen excess and binding of anticore antibodies. No correlation was found between the development of AIDS symptoms and either the duration of free antigen positivity or the level of antigenaemia. A different pattern was observed in apparently healthy seropositive individuals: 90% of whom had high antibody titres to p24 and gp41 and were persistently negative for free and complexed HIV antigen. This study demonstrates that testing HIV markers in sequentially collected serum samples from HIV seropositive individuals is a useful and simple tool for early identification of persons at risk of developing AIDS.

A cross-sectional seroepidemiologic study was carried out on household contacts and sexual partners of human immunodeficiency virus (HIV) antibody-positive intravenous drug abusers in Palermo, Italy, in 1985 to evaluate factors that influenced HIV transmission. A total of 43 index cases, 36 spouses or heterosexual partners, 28 children, and 55 adult household members were enrolled. None of the household members without sexual contact, who had shared items and facilities and had interacted with the index cases, contracted HIV infection. However, six of 36 sexual partners had antibodies to HIV. It was observed that the risk of HIV infection was significantly associated with the frequency of sexual intercourse with the seropositive partner. Four children were also found to be infected: two had acquired immunodeficiency syndrome-related complex, and the other two were clinically and immunologically normal. Furthermore, one other child had evidence of passive transfer of maternal antibodies. The infection was confined to the younger children (ranging in age from eight months to three years). The data support a high rate of vertical transmission from mother to infant, an intermediate rate of transmission to sexual partners, and no transmission attributable to household contact.

An assay based on inhibition of cytopathic effect of human immunodeficiency virus (HIV) strains in Molt 4 cells was developed to quantitate neutralizing antibodies (NA) in sera of HIV-infected individuals. The assay was specific and gave results comparable to those obtained by the inhibition of immunofluorescence (IFI) and reverse transcriptase (RT) activity. Attempts were made to correlate the presence and the antibody titres with the clinical status of HIV-infected individuals classified according to Walter Reed staging classification scheme. NA titres correlated inversely with the stage of HIV infection: Compared with acquired immunodeficiency syndrome (AIDS) patients, HIV-infected subjects at stage WR1 had significantly higher NA titres. Moreover, a decrease in NA titre in relation to clinical deterioration was noted in sequential sera of eight of 11 AIDS patients, retrospectively examined, for NA. The symptomless subjects showed either the same level of NA or a trend towards an increasing antibody titre with time. Different isolates of HIV strains showed a variability in the extent of sensitivity to neutralization by sera obtained from different HIV-infected individuals.

A seroepidemiological survey, carried out to evaluate the prevalence of antibodies to HIV in patients with ARC and in healthy individuals at risk for AIDS, showed the infection to be widespread in the groups at risk, namely in drug abusers and hemophiliacs. However, remarkable difference existed between the prevalence of antibodies to HIV in drug abusers of the city of Palermo and those of other Sicilian provinces. Spread of the virus among Sicilian thalassemics, however, was very low and quite similar in all geographic areas. Antibodies were found very rarely (0.06%) in unpaid voluntary blood donors. The spread of the virus is still confined in high risk groups, and the major part of the seropositive blood donors were identified a posteriori as drug abusers.