Studies were performed to evaluate the potential use of the bovine RIT 4237 rotavirus strain as a vaccine candidate against infection with human rotaviruses. Initial experiments revealed that colostrum-deprived piglets were susceptible to infection with several human strains, except for those belonging to subgroup 1. Subsequently, different immunization procedures with RIT 4237 were studied in this animal model. It was found that a two-dose administration, either given intramuscularly (twice) or once intramuscularly and once intragastrically, was necessary to induce a significant serum antibody response. Finally, the protective effect of the latter vaccination schedules against subgroup 2 and 3 rotavirus strains of human origin was evaluated by artificial challenge. In both cases, prior administration of live RIT 4237 significantly decreased fecal shedding of the challenge virus when compared with control animals.

No abstract

The performance of live, attenuated, homologous, canine parvovirus vaccines was studied in 140 puppies aged from four to 11 weeks. In the presence of maternally derived antibody the ability of the vaccines to elicit a serological response, as determined by the haemagglutination inhibition test and a standardised ELISA, was found to be dose (infectious titre) related. An experimental vaccine containing 10(7.0) TCID50 of virus induced seroconversion rates of 95, 89, 82 and 44 per cent in dogs with haemagglutination inhibition antibody titres of less than or equal to 8, 16, 32 and greater than 32, respectively. The standardised ELISA appeared to be better than the haemagglutination inhibition test with respect to variability and subjectivity, especially when titres were low.

Extensive use of recombinants made from A/PR/8/34 (H0N1) and wild, virulent H3N2 viruses as live influenza vaccines has provided a number of viruses of defined virulence for man. Clinical symptoms produced by these strains have ranged from febrile influenza to local coryzal symptoms or nil. A study was therefore made of the extent to which the PR8 genome had been incorporated into that of a number of the recombinants. By RNA--RNA hybridization it seemed that recombinants which had 55 per cent of greater homology with the PR8 parent were likely to conform an acceptable standard of attenuation. Those with lesser homology were frequently, but not always, clinically virulent. The technique seemed potentially useful, therefore, for screening PR8 live vaccine recombinants in vitro before giving them to volunteers.

No abstract