Co-immunization of BALB/c mice with recombinant immunogens containing G protein fragment and chimeric CTL epitope of respiratory syncytial virus induces enhanced cellular immunity and high level of antibody response

With the goal to develop effective immunogens against infection of respiratory syncytial virus (RSV), vectors co-expressing chimeric CTL epitope or G protein fragment of RSV with carrier protein DsbA (disulfide bond isomerase) were constructed. The capacity of the expressed recombinant immunogens to induce cellular and humoral immunities were evaluated. It was demonstrated that the presence of G protein fragment was able to enhance the CTL activities induced by the chimeric CTL epitope, though G protein fragment alone had no effect on induction of CTL response. In contrast, the level of antibody response to RSV and neutralization titer in co-immunization with G protein fragment plus chimeric CTL epitope was lower than that in immunization with G protein fragment alone. The challenge experiments indicated that co-immunization further reduced RSV titers both in lung tissue and nasal track, indicating the combination of humoral and cellular immunities is more effective. This data imply that the combination of the two protein immunogens would be a viable strategy for a RSV vaccine.