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Influenza virus nucleoid ("core") was obtained by the treatment of virions with hydrolytic enzymes without the use of fixing agents. The "core" buoyant density in sucrose density gradient was 1.24 g/cm3. The subvirus particles are completely devoid of surface proteins, glycoproteins, and their polypeptide composition is represented by group P proteins; NP and M proteins. RNA in the core is insensitive to the effect of RNase. Morphological analysis by electron microscopy revealed the presence of spherical compact particles without spikes on their surface.

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The state of the secondary structure of RNA and proteins comprising nucleoids (cores) and RNP of influenza virus was evaluated comparatively. The identity of RNA conformation in these particles and differences from free RNA conformation due to less marked secondary structure were found. Core proteins were predominantly represented by the beta-framework, and RNP as an alpha-helix. The specific transcriptase activity of the core is significantly lower than RNP activity of influenza virus.

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Oral immunization of volunteers with a live tissue culture influenza A (H3N2) vaccine induced an increase in virus neutralizing (VN), haemagglutination inhibiting (HI) and neuraminidase inhibiting (NI) antibody. The dynamics of antibody and IgM and IgG immunoglobulin formation in the blood depended to a great extent on their prevaccination levels. The highest per cent of seroconversions was observed after the 3rd vaccination: a 4-fold or greater rise of VN antibody was found in 80% (titre increase by 3.0 log2 units), of HI antibody in 70% (titre increase by 2.6 log2 units) and NI antibody in 73% (titre increased by 2.5 log2 units) of the volunteers. The level of IgG increased after each vaccination but its highest level did not coincide in time with the maximum antibody production. High titres of the antibodies studied were recorded 1-2 months after the 3rd vaccination, irrespective of their prevaccination levels.

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Influenza A virus antigens were detected in leukocytes by immunofluorescence. After intravenous inoculation of the A/Moscow/16/65 (H2N2) vaccine strain to chickens, cytoplasmic antigens of the virus were observed in mononuclear leukocytes from 24 to 72 hours post inoculation (p.i.). The course of antigen detectability was similar after two repeated inoculations of the virus. After oral vaccination of human volunteers with a live tissue culture influenza A monovaccine from the X-47 (H3N2) recombinant viral antigens were also found in mononuclears; the maximal number of antigen-positive cells was observed at 24 hours p.i. The method of membrane immunofluorescence proved to be the most sensitive for antigen detection; it revealed a considerable decrease in the number of antigen-positive cells after repeated administration of the virus to volunteers. This fact may possibly reflect the development of antiviral resistance in the process of vaccination.

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A controlled experiment was carried out to study the epidemiological effectiveness of live mumps vaccine from the L-3 strain, the importance of urgent prophylaxis by vaccination in mumps foci and to evaluate the economic effectiveness of mass prophylaxis of mumps by vaccination. The observations involved 113,967 children of 1 to 12 years. Vaccinations were given to 51,701 subjects and 62,256 subjects were the control group. The groups were formed by random selection. One vaccination dose contained 10(4)HAdU50 of mumps virus. The results attest to high epidemilogical effectiveness of the mumps vaccine. The incidence of mumps among the vaccinees was 29.7-fold lower than among unvaccinated, and the coefficient of protection was 96.6%. The urgent vaccination vaccination prophylaxis carried out in children's institutions during the period of introduction of mumps arrested the outbreak within one month, nad the duration of quarantine was reduced 2-3-fold. As a result of the vaccination the economic effect of 290,000 roubles was achieved.

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The reactogenic and antigenic properties of live mumps vaccine from the L-3 strain were studied in 1507 children of 1 to 12 years of age. A single injection was given, one immunizing dose containing 10(4)HAdU50 of mumps virus. The live mumps vaccine from the L-3 strain irrespective of the lot of preparation, kind (live or lyophilized), method of application (jet-injector or needle/syringe), age of the vaccinees and the amount of virus in the immunizing dose received by a vaccinee, was demonstrated to be practically areactogenic and markedly antigenic. Serological examinations by neutralization tests of 346 paired serum specimens established variation in seroconversion between individual lots to be within 62.5--82.3% (average 69.9%) of cases. Comparative studies on the postvaccination and postinfection immunitiy in mumps showed the level of antibody in the vaccinees to vary within 4.2--5.1 log2 in different years, and in convalescents within 5.1--5.9 log2 in the same years. The results indicate a sufficiently high and intensive immunity for 5 years (the observation period).

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For some years the Moscow Research Institute of Virus Preparations carried out studies concerned with the elaboration of conditions for production and control of mumps vaccine from the Leningrad-3 (L-3) strain under experimental production conditions. Twenty nine batches of the vaccine were prepared, tested and studied in extensive field trials. The paper presents the optimal conditions for the preparation of the live mumps vaccine from the L-3 strain in Japanese quail embryo cell cultures. In monkey experiments the L-3 strain was shown to have no neurovirulence. The system of biological control for the mumps vaccine permits to release the preparation meeting the current requirements for safety of live tissue culture parenteral vaccines. The data on the stability of the mumps vaccine from the L-3 strain are presented.

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