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.

Ependymomas were produced in 44 of 50 Syrian golden hamsters and in 9 of 31 outbred Swiss mice inoculated intracerebrally with high-titer, purified BK virus (BKV). Tumors contained a T-antigen that reacted with BKV-specific T-antibody in immunofluorescence and complement-fixation tests. A proportion of tumor-bearing animals had antibodies to BKV T-antigen in their sera. BKV could be rescued from two tumor cell lines by Sendal virus-mediated fusion with Vero cells. A low, or lack of, oncogenic activity was displayed by BKV inoculated sc, ip, or iv.

The leishmanin skin test was used in four different areas of the Italian Adriatic coast (Emilia Romagna, Marche, San Marino and Abruzzi), old endemic areas for cutaneous leishmaniasis. The test was found to be postitive in 80% of past infections, the 20% negative reactions being found in those who had been infected 20 or more years before. In the old endemic area of Teramo there was increasing positivity with age, with a sharp rise in the over 30 years age group suggesting that there had been a sudden break in transmission 30 years ago, coinciding with the DDT campaign of 1944-45. In San Marino in the past overt infection had occurred in a number of small microfoci, centred on houses surrounded by a larger number of inapparent infection. Control studies on a number of infectious and non-infectious diseases were all negative, and there was no relationship between tuberculin and leishmanin sensitivity.

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Leishmanin skin testing was carried out in the Emilia-Romagna region of Northern Italy, the site of an outbreak of kala-azar in 1971-72, and in Catania, Eastern Sicily an old endemic focus of Mediterranean kala-azar. Nearly all the people who had recovered from kala-azar in the past gave positive skin tests. Active cases of kala-azar gave negative tests. There was a higher proportion of positive reactors amongst the household contacts and neighbours of cases of kala-azar than among the general population. Age specific leishmanin rates showed an increasing positive rate with age in Catania, comparable to those found in endemic areas in Kenya, but in the Emilia-Romagna area all age groups showed a high positivity rate suggesting a simultaneous exposure to infection. The age specific rates from Catania suggest an interruption in transmission 20-30 years ago. The leishmanin skin test is a useful tool for the study of the epidemiology of Mediterranean kala-azar.