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The observation of many cases of mumps and mumps-associated CNS complications in vaccinees prompted us to perform an evaluation of the efficacy of four attenuated mumps virus (Urabe, Jeryl Lynn, Rubini and S12) vaccines. Two doses of vaccine were necessary to induce a good immunity in animals. The humoral and cell-mediated response induced in mice immunized intramuscularly or intranasally with these vaccines has been evaluated. Although the Urabe and Jeryl Lynn strains appear more immunogenic than the other strains and induce higher levels of IgG when administered intramuscularly, the S-12 strain administered intranasally induces a good IgG response. A marked specific CTL activity against mumps virus was observed in mice immunized intranasally with all the strains and, particularly, with the S12 strain. Thus, the intranasal immunization could be considered a possible alternative and efficient route of vaccination against mumps.

We have constructed a recombinant baculovirus expressing the rubella virus E2 (42-45 KDa) and C (34 KDa) proteins. Sf9 cells infected with recombinant virus were able to synthesize and process the two proteins coded by a unique precursor gene. By immunoblot and immunoprecipitation analysis with polyclonal and monoclonal antibodies, a precursor polyprotein (66 KDa) and two other proteins migrating with an apparent molecular weight of 42 KDa and 36 KDa were recognized as E2 glycoprotein and C protein, respectively. The recombinant E2 protein appeared to be glycosylated since it was susceptible to tunicamycin. The results indicate that the RV polyprotein coding for E2 and C is expressed and proteolytically cleaved in insect cells. This baculovirus expression system provides a useful alternative approach for the production of rubella virus antigens and should allow the purification of large quantities of the RV proteins for further biochemical and immunological studies.

A serological study was carried out on 527 girls immunized with RA 27/3 rubella vaccine. Data from all scheduled serum samples over a 5-year follow-up were available for 102 vaccinees, 10 (9.8%) of whom showed evidence of reinfection during the 5th year after immunisation, a year in which there was a rubella outbreak in the Siena area (Italy). We examined in greater detail the serological responses of these vaccinees after reinfection and the consequent implications pertinent to the duration of the protective immunity.

Essential parts of epitopes have been identified on rubella virion envelope glycoprotein E1, by scanning with overlapping octapeptides situated between amino acids 243-286 in a previously determined antigenic domain.

Antibody responses to individual structural proteins (E1, E2, and C) of the M33 wild rubella virus and the RA 27/3 live attenuated rubella strain were assayed by immunoblotting in 11 girls, following immunization with RA 27/3 rubella vaccine. Serum samples were drawn before immunization and at 10 days, 1 month, 1 year, 2 years, and 3 years afterwards. All the subjects showed antibodies to E1 glycoprotein of both the virus strains up to three years after immunization, indicating the importance of E1 in immunity. Antibodies to E1 were always present when with neutralizing activity was observed. Antibodies to E2 protein of both the viruses and to the C protein of the M33 virus gradually disappeared with time in some samples, while antibodies to C protein of the RA 27/3 virus strain were found persistently in all the sera.

Antibody response to individual structural proteins (E1, E2, and C) of the M-33 wild rubella virus strain was assayed by an immunoblot technique in 12 girls, following immunization with RA 27/3 live attenuated rubella vaccine. Of the 12 immunized subjects, before vaccination 9 had no demonstrable rubella specific antibodies while the remaining 3 had a low level of rubella specific antibodies, reacting only with the E1 protein. At one month after vaccination all the immunized subjects presented anti-E1, anti-E2, and anti-C specific antibodies. However, at 1-2 weeks after vaccination the 9 girls who were seronegative before immunization still had no detectable antibodies to any of the rubella virus structural proteins, while the 3 subjects whose preimmunization sera had reacted with the E1 protein presented an accelerated immune response, showing anti-E2 and anti-C specific antibodies and a more intensely marked anti-E1 specific band.