Syncytial giant-cell hepatitis is a rare but severe form of hepatitis that is associated with autoimmune diseases, drug reactions, and viral infections. We used serologic, molecular, and immunohistochemical methods to search for an infectious cause in a case of syncytial giant-cell hepatitis that developed in a liver-transplant recipient who had latent infection with variant B of human herpesvirus 6 (HHV-6B) and who had received the organ from a donor with variant A latent infection (HHV-6A). At the onset of the disease, the detection of HHV-6A (but not HHV-6B) DNA in plasma, in affected liver tissue, and in single micromanipulated syncytial giant cells with the use of two different polymerase-chain-reaction (PCR) assays indicated the presence of active HHV-6A infection in the patient. Expression of the HHV-6A-specific early protein, p41/38, but not of the HHV-6B-specific late protein, p101, was demonstrated only in liver syncytial giant cells in the absence of other infectious pathogens. The same markers of HHV-6A active infection were documented in serial follow-up samples from the patient and disappeared only at the resolution of syncytial giant-cell hepatitis. Neither HHV-6B DNA nor late protein was identified in the same follow-up samples from the patient. Thus, HHV-6A may be a cause of syncytial giant-cell hepatitis.

Infectionwith BKvirus in man is common in England (Gardner, 1973); haemagglutinationinhibiting (HI) and complement-fixing antibodies were found in all age gropps. We investigated 453 healthy people in Italy by the HI test, and also by the fluorescent-antibody (FA) technique to detect antibodies to other structural components of the virion. MATERIALS AND METHODS Virus and cells. BK virus was kindly supplied by Dr S. D. Gardner and was grown inVero cells. Growth and maintenance media were Eagle's minimum essential medium supplemented with 2.5 % foetal bovine serum. One week after infection of the cultures the medium was changed and after a further 7-10 days' incubation, when cytopathic effects were clearly evident, cells and medium were frozen and thawed once, treated for 2 min. in a Branson ultrasonic disintegrator, and centrifuged at 800 g for 10 min. to sediment cellular debris. The supernatant fluid had a titre of 2048 to 40,768 haemagglutinating units (HAU) per ml, and was used as antigen in the haemagglutination (HA) and HI antibody tests. SV40 was grown in Vero cells in the same way as BK virus.Sera. Serum specimens were obtained from healthy donors, ages 19-65 years, in the Blood Centre of the University Hospital, Bologna. Other sera were collected from healthy children and young people, aged 6 months-18 years, in Milan.Haemagglutination. HA and HI antibody tests were performed in disposable plates by the microtitre method (Sever, 1962). Serial two-fold dilutions of BK virus were made in 0.05-ml amounts of phosphate-buffered saline (PBS), pH 7.2. Human type-0 erythrocytes, from healthy donors, were washed three times and suspended to a concentration of 0-5 % in PBS. One volume of PBS and two volumes of 0.5% erythrocytes were added to each virus dilution. Plates were incubated at +4"C and the HA titre was read 4 hours later, when control erythrocytes in PBS only had completely sedimented. The highest dilution of antigen giving complete haemagglutination was considered to contain 1 HAU. Haemagglutination-inhibition. Sera were heated at 56°C for 30 min. and treated with NaI04 to remove non-specific inhibitors. Serial, two-fold dilutions of serum, from 1 in 4 to 1 in 8192, were made in 0.05 ml amounts of PBS. One volume of PBS containing 8 HAU of antigen was added to each serum dilution and the mixtures were kept at room temperature for 1 hour. After this time, two volumes of 05% erythrocytes were added, the plates were incubated at + 4°C for 4 hours, and the HI-antibody titres were read. From the correlation

Primary hamster kidney cells were transformed by BK virus, a new human papovavirus. Transformed (HKBK) cells produced BK virus T antigen and induced tumors in hamsters that developed antibodies to BK virus T antigen. BK virus was rescued from HKBK cells by Sendai virus-assisted fusion with permissive cells. One out of six cell lines derived from HKBK cell-induced tumors showed the same characteristics as HKBK cells.

SUMMARYHuman embryonic fibroblasts (HEF) have been transformed by BK virus (BKV) DNA and by u.v.-inactivated or live BKV alone or in association with methylcholanthrene (MTC). The transformed cells produced BKV large T and small t antigens as well as the cellular 53 kdal protein, detected by immunofluorescence and immunoprecipitation. After an initial phase of lysis and virus shedding, virus or its coat protein antigen could not be detected in transformed cells. All human transformed cell lines could be superinfected by BKV or BKV DNA, but their susceptibility to superinfection was 20-to 500-fold lower than normal HEF. BKV could be rescued by fusion of transformed cells with normal HEF or Veto cells and by transfection of normal HEF with total DNA and DNA extracted from the Hirt supernatant of transformed cells. Blot hybridization analysis of DNA from transformed cells showed a considerable amount of free BKV DNA in monomeric and polymeric forms. Integrated BKV DNA was absent in most cell lines but present in only small amounts in BKV-transformed cells treated with MTC. Analysis of free BKV DNA with various restriction endonucleases and by blot hybridization showed that monomeric forms were complete BKV genomes, whereas polymers contained both complete and defective or rearranged BKV DNA. Transformation of HEF was also obtained with a 3.7 kilobase (kb) fragment of the BKV genome, produced by sequential digestion of BKV with the restriction endonucleases HhaI and EcoRI. This fragment extends clockwise on the virus genome from 0 to 72-2 map units and contains the entire early region. Blot hybridization analysis of cells transformed by the HhaI/EcoRI 3.7 kb fragment showed two separate integrations of BKV sequences without free virus DNA.

No abstract