The review presents a modern strategy to improve the means of vaccine prevention of streptococcal infections aimed at finding and developing new vaccines for immunization of people belonging to risk groups. It should be noted that pneumococci (S. pneumoniae) are members of gram-positive bacteria (diplococci) and become the main cause of various nosological forms of human infectious diseases (such as pneumonia, otitis media, sinusitis, bacteremia and meningitis). Existing pneumococcal vaccines (conjugate and polysaccharide) have some important limitations, for example, serotype dependence, loss of effectiveness due to a change in the serotype landscape, insufficient protective effect from non-invasive forms of pneumococcal infections and high production costs associated with the development of these products. The main part of the review presents the most important research papers that used modern proteomic technologies in the study of the S. pneumoniae proteomic profile. These works allow us to evaluate at the molecular level the importance of bacterial proteins as candidates for creating new combination vaccines that can effectively protect against the full range of pneumococcal serotypes circulating in the human population. So, in particular, the data are provided on the new methodology for the analysis of the proteome of extracellular S. pneumoniae bacterial microvesicles to identify immunoreactive protein antigens, potential candidates for inclusion into vaccines. As a result of these studies, 15 immunoreactive proteins were discovered, 7 of which are cytosolic and 8 proteins are bound to the cell surface (MalX, ABC transporter or substrate binding transport protein, AmiA, AliA, LytC, IgA1 protease, PspA and the putative precursor of β-galactosidase). These are possible candidates for developing combination vaccines. Additionally, the review presents data on the role of significant virulence factors of the protein nature of S. pneumoniae strains in nasopharyngeal colonization, increased infectivity, as well as on overcoming reactions of the host's immune response.
Novel Protein-Based Pneumococcal Vaccines: Assessing the Use of Distinct Protein Fragments Instead of Full-Length Proteins as Vaccine Antigens