Identifying protective synthetic oligosaccharide (OS) epitopes of Streptococcus pneumoniae capsular polysaccharides (CP) is an indispensable step in the development of third generation carbohydrate pneumococcal vaccines. Synthetic tetra-, hexa-, and octasaccharide structurally related to CP of S. pneumoniae Type 14 were coupled to BSA, adjuvanted with aluminum hydroxide and tested for their immunogenicity in mice upon intraperitoneal prime-boost immunizations. Injections of the conjugates induced production of opsonizing anti-OS IgG1 antibodies. Immunization with the tetra- and octasaccharide conjugates stimulated the highest titers of the specific antibodies. Further, the tetrasaccharide ligand demonstrated the highest ability to bind OS and CP antibodies. Murine immune sera developed against tetra- and octasaccharide conjugates promoted pathogen opsonization to a higher degree than antisera against conjugated hexasaccharide. For the first time, the protective activities of these glycoconjugates were demonstrated in mouse model of generalized pneumococcal infections. The tetrasaccharide conjugate possessed the highest protective activities. Conversely, the octasaccharide conjugate had lower protective activities and the lowest one showed the hexasaccharide conjugate. Sera against all of the glycoconjugates passively protected naive mice from pneumococcal infections. Given that the BSA-tetrasaccharide induced the most abundant yield of specific antibodies and the best protective activity, this OS may be regarded as the most promising candidate for the development of conjugated vaccines against S. pneumoniae type 14 infections.

We report the effect of a BSA conjugate of a synthetic hexasaccharide related to the fragment of the capsular polysaccharide (PS) of Streptococcus pneumoniae type 14 on the stimulation of innate and cell-mediated immunity and the subsequent development of a PS-specific antibody response. Glycoconjugate (GC) in the presence (GC+AL) or absence of aluminium hydroxide was administered to mice twice. GC increased the number of TLR2-expressing cells and induced the maturation of dendritic cells (CD11c+, CD80+ and MHCII+), which secreted IL-1β, IL-6, and TNFα into the culture medium. The level of IL-1β, IL-10, IFNγ, and TNFα in the blood increased within 24 h after the single GC administration to mice. On day 7, the numbers of splenic CD4+ and CD8+ Т lymphocytes and B lymphocytes increased. After the second immunization, the levels of CD4+ and CD8+ Т lymphocytes were lower than in the control, whereas the B cell, NK cell and MHC class II-expressing cell numbers remained enhanced. However, of the presence of anti-PS IgG antibodies was not detected. The addition of aluminium hydroxide to GC stimulated the production of GM-CSF, IL-1β, IL-5, IL-6, IL-10, IL-17, IFNγ, and TNFα. Anti-PS IgG1 antibody titres 7 days after the second immunization were high. During that period, normal levels of splenic CD4+ T lymphocytes were maintained, whereas reduced CD8+Т lymphocyte numbers and increased levels of B lymphocytes, NK cells and MHC class II-expressing cell numbers were observed. Anti-PS IgG levels diminished until day 92. A booster immunization with GC+AL stimulated the production of anti-PS IgG memory antibodies, which were determined within 97 days. The elucidation of specific features of the effect of the synthetic hexasaccharide conjugate on the stimulation of innate, cell-mediated immunity and antibody response can favour the optimization of glycoconjugate vaccine design.

Background. Influenza prophylaxis with the use of quadrivalent vaccines (QIV) is increasingly being introduced into healthcare practice. Methods. In total, 32 healthy adults and 6 patients with common variable immunodeficiency (CVID) received adjuvant QIV during 2018–2019 influenza season. Depending on initial antibody titers, healthy volunteers were divided into seronegative (≤1:20) and seropositive (≥1:40). To evaluate immunogenicity hemagglutination inhibition assay was used. Results. All participants completed the study without developing serious post-vaccination reactions. Analysis of antibody titer 3 weeks after immunization in healthy participants showed that seroprotection, seroconversion levels, GMR and GMT for strains A/H1N1, A/H3N2 and B/Colorado, B/Phuket among initially seronegative and seropositive participants meet the criterion of CHMP effectiveness. CVID patients showed increase in post-vaccination antibody titer without reaching conditionally protective antibody levels. Conclusion. Adjuvant QIV promotes formation of specific immunity to vaccine strains, regardless of antibodies’ presence or absence before. In CVID patients search of new regimens should be continued.

Pregnant women are risk group for influenza infection. Results of new subunit vaccines application have not been studied enough. Prospective, randomized, open-label comparative study of subunit (Agrippal) and polymeric subunit (Grippol plus) vaccines. 42 pairs of mothers-infants were participated in the study. Protective antibodies (≥ 1:40) to different influenza strains were registered on day 1 after the birth on the same level as 53% of cases in pairs mothers-infants after immune adjuvant polymeric subunit and subunit vaccines administration. There were the same level of protective antibodies (AB) among mothers after 3 month, but transplacental antibodies decreased among infants and registered in the 13–22% cases of Grippol plus group and 31–43% cases in Agrippal S1 group. AB titre to influenza virus A/H1N1/pdm09 and A/H3N2/in pairs mothers-infants were the same in both groups in first days after birth, but AB levels to B strain were lower among infants without regard to vaccine. There is no difference in AB titres among infants of both groups at 3 month of age, but their levels were twice lower versus initial data. An immune adjuvant polymeric subunit as well as subunit vaccines application in pregnant women forms protective AB in pairs mothers-infants.

Tγδ and B1 lymphocytes are essential components of the mucosal immune system, activating different bacterial and viral ligands without costimulatory signals and preprocessing of other immune effectors. This ability enables the immune system to provide rapid protection against pathogens and contributes to the decoding mechanism of the sensitizing activity of mucosal antigens, because the interaction of these cells produces antibodies for immunoglobulin M (IgM) and IgA, but not for IgE. We studied 3 routes of introducing antigens for opportunistic microorganisms to activate Tγδ and B1 lymphocytes: subcutaneous, intranasal, and oral. The subcutaneous and intranasal routes produced a significant increase of these cells in lymph nodes associated with the nasal cavity (NALT) and in those associated with bronchial tissue (BALT). The oral route significantly increased levels of these cells in the spleen, in NALT, BALT, and in nodes associated with the gut (GALT). We found that mucosal application of the immunomodulator Immunovac-VP-4 (contains antigens of conditionally pathogenic microorganisms), in conjunction with the activation of Tγδ and B1, induces adaptive immune mechanisms not only in the lymphoid formations associated with the respiratory system and with GALT, but also in the spleen (increased expression of cluster of differentiation 3 [CD3], CD4, CD8, CD19, and CD25). This indicates that there is migration of lymphoid cells from the regional lymph nodes and mucosal lymphoid tissues via the lymph and blood to distant organs, lymphoid development, and both local and systemic immunity. Mucosal application of Immunovac-VP-4 in mice potentiates the cytotoxic activity of NK cells in the NALT, BALT and GALT. The highest cytotoxicity was observed in cells, derived from lymphoid tissue of the intestine after oral immunization. Although we found that cytokine production was increased by all 3 immunization routes, it was most intensive after subcutaneous injection.