Lysates of HEp-2 cells productively infected with herpes simplex virus yielded two bands on isopycnic centrifugation in CsCl gradients, ranging from 1.2 to 1.6 g/cm3. One band, designated a, had a mean buoyant density of 1.27 g/cm3 and contained herpes virions. Band , had a mean density of 1.305 g/cm3 and contained primarily complement-fixing viral antigens and little or no viral deoxyribonucleic acid (DNA). The products banding in the a and A bands were unstable; fivefold or higher amounts were recovered by treating the cell extract with formaldehyde prior to centrifugation. Formaldehyde treatment increased the buoyant density of viral products in both the a and : bands by about 0.015 g/cm3. In addition, it stabilized hitherto inapparent products, forming a broad bandy with a density range of 1.37 to 1.45 g/cm3. The material in the Py band was heterogeneous; it contained viral DNA, cellular DNA, and viral antigen. Formalinized lysates of DK cells abortively infected with herpes simplex virus yielded a (3 band undifferentiated from that formed by extracts of productively infected cells. The 'y band was less dense and narrower. The a band was entirely missing.
Influenza A/Scotland/74 (H3N2) and A/Victoria/75 (H3N2) cold-adapted (ca) recombinant viruses, prepared by mating the A/Ann Arbor/6/60 (H2N2) ca donor virus and influenza A wild-type virus, were evaluated in adult seronegative volunteers (serum hemagglutination-inhibiting antibody titer, 51:8) for level of attenuation, antigenicity, and genetic stability of the temperature-sensitive and ca phenotypes. At 107.0 to 107-5 50% tissue culture infective doses the A/Scotland/74 and A/Victoria/75 ca recombinant viruses were clearly attenuated and antigenic. However, one of eight vaccinees infected with 107-5 50% tissue culture infective doses of the A/Scotland/74 ca recombinant had a febrile reaction (390C). At a 10-fold higher dose (108.5 50% tissue culture infective doses), 4 of 12 A/Scotland/74 vaccinees had a febrile and/or systemic reaction. Febrile reactions were not observed in volunteers who received the A/Victoria/75 ca recombinant virus, whereas 3 of the 12 vaccinees had mild upper respiratory tract symptoms, in one instance associated with mild systemic manifestations. Significantly, the serum hemagglutinationand neuraminidase-inhibiting antibody responses were comparable to those induced by wild-type virus. Both ca recombinant viruses were shed in low titer for a short period of time. Each isolate retained the temperature-sensitive phenotype. However, there was evidence of genetic instability of the ca marker in that 7 of 24 isolates exhibited some loss of the ca property, and one isolate completely lost the capacity to produce plaques at 25CC.
The Hong Kong/68-ts-l[E] virus, which has a 380C shutoff temperature for plaque formation, has been proposed as a donor of its two ts lesions to new variants of influenza A virus that pose an epidemic threat. To further examine whether the acquisition of the two ts-l[E] lesions will predictably attenuate new influenza A variants, the HK/68-ts-1[E] virus was mated with the A/Vic/3/75 wild-type virus. The Vic/75-ts-[E] recombinants that had the two ts-l[E] lesions also had a 380C shutoff temperature. Two Vic/75-ts-l[E] recombinants (clones 81 and 113) that had the two ts-l[E] lesions, a 380C shutoff temperature, and the
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