[COMPARATIVE STUDY OF IMMUNOGENICITY AND PROTECTIVE EFFECT OF LIVE COLD-ADAPTED AND INACTIVATED VACCINES AGAINST TYPE...

Direct comparative studies of immunogenicity and protective effect of live cold-adapted (ca) and inactivated vaccines against type A influenza.

Groups of mice were immunized intramuscularly (i/m) or intranasally (i/n) twice with inactivated or live ca vaccines based on wild-type parent strain A/Krasnodar/101/59 (H2N2) and the corresponding ca donor strain A/Krasnodar/101/59/30CE/5MDCK/l/7/4 (H2N2), respectively. Immunogenicity was determined by HAI antibodies in sera and lungs (extracts) against both vaccine strains. Protective effect--by the level of wild-type strain in lungs of immunized mice after the infection.

Live ca and inactivated vaccines based on similar strains increase immunogenicity and protective effect when administered via different routes in varying patterns. A significant increase of immunogenicity was only observed for i/m (sera antibodies) and i/n (lung antibodies) administration of the live ca vaccine, and could be determined by antigenic features of the vaccine strains. At the same time, all the vaccine variants and administration routes induced at least partial protection from infection compared with unimmunized control. However, complete protection from infection was only noted for the i/m administered live ca vaccine.

A combination of immunization variant and vaccine type determines immunogenicity and protective effect, and their interconnection requires further studies using all the possible combinations of preparations and administration routes as well as determination of induction of various components of the immune system.