Th17 responses to pneumococcus in blood and adenoidal cells in children

Conjugation Mechanism for Pneumococcal Glycoconjugate Vaccines: Classic and Emerging Methods

Licensed glycoconjugate vaccines are generally prepared using native or sized polysaccharides coupled to a carrier protein through random linkages along the polysaccharide chain. These polysaccharides must be chemically modified before covalent linking to a carrier protein in order to obtain a more defined polysaccharide structure that leads to a more rational design and safer vaccines. There are classic and new methods for site-selective glycopolysaccharide conjugation, either chemical or enzymatic modification of the polysaccharide length or of specific amino acid residues of the protein carrier. Here, we discuss the state of the art and the advancement of conjugation of S. pneumoniae glycoconjugate vaccines based on pneumococcal capsular polysaccharides to improve existing vaccines.

Immune responses to bacterial lung infections and their implications for vaccination

The pulmonary immune system plays a vital role in protecting the delicate structures of gaseous exchange against invasion from bacterial pathogens. With antimicrobial resistance becoming an increasing concern, finding novel strategies to develop vaccines against bacterial lung diseases remains a top priority. In order to do so, a continued expansion of our understanding of the pulmonary immune response is warranted. Whilst some aspects are well characterised, emerging paradigms such as the importance of innate cells and inducible immune structures in mediating protection provide avenues of potential to rethink our approach to vaccine development. In this review, we aim to provide a broad overview of both the innate and adaptive immune mechanisms in place to protect the pulmonary tissue from invading bacterial organisms. We use specific examples from several infection models and human studies to depict the varying functions of the pulmonary immune system that may be manipulated in future vaccine development. Particular emphasis has been placed on emerging themes that are less reviewed and underappreciated in vaccine development studies.

Generation of protective pneumococcal-specific nasal resident memory CD4+ T cells via parenteral immunization

The generation of tissue-resident memory T cells (T_RM) is an essential aspect of immunity at mucosal surfaces, and it has been suggested that preferential generation of T_RM is one of the principal advantages of mucosally administered vaccines. We have previously shown that antigen-specific, IL-17-producing CD4⁺ T cells can provide capsular antibody-independent protection against nasal carriage of Streptococcus pneumoniae; but whether pneumococcus-responsive T_RM are localized within the nasal mucosa and are sufficient for protection from carriage has not been determined. Here, we show that intranasal administration of live or killed pneumococci to mice generates pneumococcus-responsive IL-17A-producing CD4⁺ mucosal T_RM. Furthermore, we show that these cells are sufficient to mediate long-lived, neutrophil-dependent protection against subsequent pneumococcal nasal challenge. Unexpectedly, and in contrast with the prevailing paradigm, we found that parenteral administration of killed pneumococci also generates protective IL-17A⁺CD4⁺ T_RM in the nasal mucosa. These results demonstrate a critical and sufficient role of T_RM in prevention of pneumococcal colonization, and further that these cells can be generated by parenteral immunization. Our findings therefore have important implications regarding the generation of immune protection at mucosal surfaces by vaccination.

Differential IL-17A response to S. pneumoniae in adenoid tissue of children with sleep disordered breathing and otitis media with effusion

Streptococcus pneumonia, one of the major colonizers in nasopharyngeal adenoids, has been the predominant pathogen causing acute otitis media (AOM) in children. Recent evidence suggests an association between IL-17A-mediated immune response and the clearance of pneumococcal colonization in nasopharyngeal adenoids. Here, we evaluated the expressions of IL-17A and associated genes in hypertrophic adenoid tissues of children with sleep-disordered breathing (SDB) and otitis media with effusion (OME) and their association with pneumococcal carriage. Sixty-six pediatric patients with adenoid hypertrophy were enrolled. During adenoidectomy, nasopharyngeal swab and adenoid tissues were used to determine pneumococcal carriage and IL-17A expression. Our results revealed significantly higher levels of IL-17A and IL-17A:IL-10 mRNA in the SDB patients positive for nasopharyngeal pneumococcal carriage than those negative. However, these differences were not significant in the OME group. These results suggested, in OME patients, prolonged or chronic pneumococcal carriage may occur because of insufficient IL-17A-mediated mucosal clearance, and could further lead to AOM and OME development.

Screening for Th17-Dependent Pneumococcal Vaccine Antigens: Comparison of Murine and Human Cellular Immune Responses

Conjugate vaccines against Streptococcus pneumoniae have significantly reduced the incidence of diseases caused by the serotypes included in those vaccines; however, there is still a need for vaccines that confer serotype-independent protection. In the current study, we have constructed a library of conserved surface proteins from S. pneumoniae and have screened for IL-17A and IL-22 production in human immune cells obtained from adenoidal/tonsillar tissues of children and IL-17A production in splenocytes from mice that had been immunized with a killed whole-cell vaccine or previously exposed to pneumococcus. A positive correlation was found between the rankings of proteins from human IL-17A and IL-22 screens, but not between those from human and mouse screens. All proteins were tested for protection against colonization, and we identified protective antigens that are IL-17A dependent. We found that the likelihood of finding a protective antigen is significantly higher for groups of proteins ranked in the top 50% of all three screens than for groups of proteins ranked in the bottom 50% of all three. The results thus confirmed the value of such screens for identifying Th17 antigens. Further, these experiments have evaluated and compared the breadth of human and mouse Th17 responses to pneumococcal colonization and have enabled the identification of potential vaccine candidates based on immunological responses in mouse and human cells.