The adenovirus type 7 (Ad7) isolates from the 1995 nationwide outbreak in Japan were genetically and seroepidemiologically analyzed in comparison with Japanese Ad7 strains isolated before 1995 to determine their genome type and to speculate on their origin and causative factors of the outbreak. Twenty-six Ad7 isolates from the outbreak were identified by restriction enzyme analysis as the Ad7d2 genome type, while 22 Ad7 strains sporadically isolated in Japan before 1995 were identified as Ad7d. Partial nucleotide sequencing of the E3 region of Ad7d2 revealed a nucleotide substitution of G to A at position 265, resulting in the absence of the BstEII site and making Ad7d2 distinct from Ad7d. In Hiroshima City, Japan, no Ad7 was isolated from 1982 to 1994, but 43 and 50 Ad7 strains were isolated in 1995 and 1996, respectively. A seroepidemiological study of 251 serum samples collected in 1989 in Hiroshima City showed that only 2.8% of the samples were positive for Ad7. These results indicate that the 1995 outbreak of Ad7 in Japan was caused by the Ad7d2 genome type, which might have been introduced from outside Japan. The results also suggest that the low mass immunity in Japan was critical for the outbreak and that the mutation in the E3 region in Ad7d2 may have influenced transmission.

Deoxythymidine kinase (TdR kinase) from rabbit kidney cells infected in vitro with herpes simplex virus type 1 (HSV-1) or type 2 (HSV-2) was further investigated. Enzyme activity induced by HSV-2 was more heat-labile and more sensitive to inhibition by deoxythymidine nucleotides than HSV-1 induced enzyme activity in both crude extracts and partially purified preparations. The thermostability of TdR kinase activity from cells coinfected with HSV-1 and HSV-2 was intermediate between enzymes induced separately. The difference in thermostability between the two enzyme activities was also observed in extracts from 1-β-D-arabinofuranosylcytosine (ara-C) treated infected cells. HSV-1 and HSV-2 induced enzymes also differed in their response to substrate concentration. Gel filtration with Sephadex G-100 revealed the presence of monomer, dimer and aggregated forms of HSV-1 induced enzyme. The molecular weights of the monomer and dimer were estimated to be 58,000 and 97,000, respectively. Such multiple forms were not observed with HSV-2; the molecular weight of the HSV-2 induced enzyme was estimated to be 45,000 to 60,000, depending upon the eluting buffers. HSV-1 induced TdR kinase activity showed a different electrophoretic activity pattern in polyacrylamide gel electrophoresis than did the enzyme induced by HSV-2.

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SUMMARYThymidine kinase (TK) induced by varicella-zoster virus (VZV) was precipitated with ammonium sulphate and purified by Sephadex G-150, QAE-Sephadex and Blue Sepharose column chromatographies. The purified TK fraction also contained deoxycytidine kinase (dCK) activity and a 35000 mol. wt. (35K) polypeptide as a major' component. The TK and dCK activities were both neutralized by anti-VZV serum.