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Mutations in the precore region of hepatitis B virus (HBV) have been associated with failure of expression of HBV e-antigen (HBeAg), however, the prevalence of these and other mutations in HBV carriers without overt chronic liver disease remains uncertain. Homosexual or bisexual males (n = 65) with chronic HBV infection attending The Middlesex Hospital, London were studied, of whom two had clinical evidence of chronic liver disease. HBV DNA was amplified from 62 of 65 serum samples using nested and double nested polymerase chain reaction (PCR) assays. Direct sequencing of the PCR products was employed to investigate sequence variation. HBV-DNA from all available HBeAg-negative (n = 9) and selected HBeAg-positive (n = 33) sera were sequenced in the entire precore gene, the 3' terminal portion of the X gene (aa128-154), and the 5' terminus of the core gene (aa18-73). Sequences were highly conserved in all regions studied. Samples from two anti-HBe-seropositive patients contained mutations in the precore region. In one, a single mutation in the first amino acid resulted in a change to leucine, which would prevent translation of this region and therefore HBeAg expression. Wild type sequences were also detected in this sample. In the other sample from a patient with overt chronic liver disease, a mutation of precore amino acid 28 changed a tryptophan residue to a stop codon which would also prevent HBeAg expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Mutations of the precore region of hepatitis B virus (HBV) genome have been associated with fulminant and severe chronic hepatitis. However uncertainty remains about the clinical significance and transmissibility of these mutant strains. A point mutation assay (PMA) was developed to identify qualitatively and quantitatively mutations affecting precore amino acids 1 and 28. We have analysed serum samples from six mother-infant pairs where perinatal transmission of HBV has occurred and where the mothers were HBV carriers without detectable serum HBeAg. In three cases fulminant hepatitis developed in the infant, in two cases acute hepatitis resolved, and in one case the infant was immunised and did not become infected. We also examined serum from a healthcare worker, an anti-HBe-seropositive HBV carrier, believed to have transmitted HBV infection to a patient. The PMA results were confirmed in all cases by direct sequencing of polymerase chain reaction (PCR) products using nested and double-nested PCR with primers to the precore and X region. Precore aa28 mutant-type virus was detected in the serum of one mother at the time of delivery of three of her children, two of whom developed fulminant hepatitis. Another mother of an infant with fulminant hepatitis had no precore mutations. In one mother-infant pair a mixed viral population was found; the acute hepatitis B in the infant resolved. The HBV sequence from the healthcare worker was also of aa28 mutant type. No mutations of aa1 were detected in any of the specimens. The study supports the association of precore mutations with some cases of transmission of HBV infection from HBeAg-negative mothers to their infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell-free human immunodeficiency virus type-1 (HIV-1) was precipitated from archival serum with polyethylene glycol (PEG), and HIV-1 RNA was detected and quantified by reverse transcription and amplification in a nested polymerase chain reaction (PCR). The assay of end-point dilutions cDNA in nested PCRs allowed an estimation of the minimum RNA copies per unit volume of serum. RNA titres correlated with the classification of HIV-1 infection by CDC disease groups (30 patients). The geometric mean titres of HIV-1 serum RNA from patients grouped by disease stage gave minimum estimates of 340 and 400 virions per millilitre of serum in CDC groups II and III (n = 6 and 10, respectively) and 4,240 virions per millilitre in CDC group IV (n = 14). An overall fall in viral titre measured in this way was observed in 3 patients during zidovudine treatment. HIV-1 titres increased in a further 4 patients when therapy was interrupted, stopped, or complicated by secondary infection.

Thirty-five homosexual men who had been the regular sexual partners (for at least 6 months) of anti-HIV-positive patients with AIDS (N = 18) or PGL (N = 17) were studied. Twenty-one (60%) were seropositive, but 14 (40%) were consistently anti-HIV-negative. The duration of relationship with the index case was not statistically different in seropositive compared to seronegative partners; median 26 months (range 7-60) vs 30 months (range 7-60). However, seropositive partners had a significantly higher monthly number of other sexual partners and sexually transmitted diseases and a higher frequency of insertive and receptive anal intercourse in the preceding five years. The risk of acquiring HIV infection was significantly increased by frequent receptive anal intercourse when the frequency of insertive was controlled for but not the converse. Seronegative partners had undetectable antibodies by live and fixed cell immunofluorescence and by radioimmunoprecipitation and were repeatedly negative by competitive enzyme immunoassay. Furthermore, the sera of seronegative partners lacked HIV neutralising activity. Peripheral blood mononuclear cells (PBMCs) from seronegative partners, stained with monoclonal antibodies to seven different CD4 epitopes, revealed no differences when compared to those from heterosexual controls and no qualitative differences from cells from seropositive individuals. In addition, PBMCs from seronegative partners could be productively infected by HIV in vitro. If resistance to infection in seronegative partners exists, then it is likely that mechanisms other than a specific humoral immunity or CD4 polymorphisms are involved.