Recombinant Vaccine Candidates with Integrated Adjuvants Provide Stimulation of an Effective Immune Response Against Bacterial Infections

The use of recombinant proteins as vaccine preparations is limited by their weak immunogenicity, which can be enhanced by the use of adjuvants, the development of which is an important and urgent problem of modern vaccinology. Significantly, adjuvants as additives to vaccine preparations are of concern to clinicians. From this point of view, the idea of including an internal adjuvant into the structure of a recombinant protein molecule is of undoubted interest. Previously, we synthesized and studied two recombinant vaccine preparations specific for S. agalactiae (Su4) and S. pneumoniae (PSPF). Each of them was a tandem of immunogenic bacterial surface proteins in combination with an additional adjuvant site. The amino acid sequence identical to flagellin acted as an internal adjuvant. In this work, we investigated the possibility of additional enhancement of the body’s immune response to immunization with recombinant Su4 and PSPF proteins due to the simultaneous administration of an external adjuvant, carboxymethylchitosan or Imject Alum.Studies have shown that the additional introduction of these adjuvants into the composition of the vaccine preparation did not affect the immunogenicity of the Su4 and PSPF proteins, which included the internal adjuvant flagellin. The protective efficacy of the immune response to all immunization options was comparable.Thus, the inclusion of a flagellin insert as an internal adjuvant into the composition of recombinant proteins ensures the development of the highest possible level of the immune response and its protective efficacy against the corresponding pathogens of a bacterial infection.