Pneumococcal Vaccines: Challenges and Prospects

A narrative review of genomic characteristics, serotype, immunogenicity, and vaccine development of Streptococcus pneumoniae capsular polysaccharide

This narrative review describes genomic characteristic, serotyping, immunogenicity, and vaccine development of Streptococcus pneumoniae capsular polysaccharide (CPS). CPS is a primary virulence factor of S. pneumoniae. The genomic characteristics of S. pneumoniae CPS, including the role of biosynthetic gene and genetic variation within cps (capsule polysaccharide) locus which may lead to serotype replacement are still being investigated. One hundred unique serotypes of S. pneumoniae have been identified through various methods of serotyping using phenotypic and genotypic approach. The advantages and limitations of each method are various, emphasizing the need for accurate and comprehensive serotyping for effective disease surveillance and vaccine targeting. In addition, we elaborate the critical role of CPS in vaccine development by providing an overview of immunogenicity, ongoing research of pneumococcal vaccines, and the impact on disease burden.

Impaired IgM Memory B Cell Function Is Common in Coeliac Disease but Conjugate Pneumococcal Vaccination Induces Robust Protective Immunity

Coeliac disease (CD) is associated with hyposplenism, an acquired impairment of spleen function associated with reduced IgM memory B cells and increased susceptibility to serious pneumococcal infection. Little is known about the immune implications of hyposplenism in CD or the optimal pneumococcal vaccination strategy. In this study, the immune effects of hyposplenism in CD, and the accuracy of screening approaches and protective responses induced by two different pneumococcal vaccines were examined. Active and treated CD cohorts, and healthy and surgically splenectomised controls underwent testing for the presence of Howell-Jolly bodies and pitted red cells, spleen ultrasound, and immune assessment of IgM memory B cell frequency and IgM memory B cell responses to T cell-dependent (TD) or T cell-independent (TI) stimulation. Responses following conjugate (TD) and polysaccharide (TI) pneumococcal vaccination were compared using ELISA and opsonophagocytic assays. Although hyposplenism is rare in treated CD (5.1%), functional B cell defects are common (28-61%) and are not detected by current clinical tests. Conjugate pneumococcal vaccination induced superior and sustained protection against clinically relevant serotypes. Clinical practice guidelines in CD should recommend routine pneumococcal vaccination, ideally with a conjugate vaccine, of all patients in lieu of hyposplenism screening.

The Role of Health Information Technology in Pneumococcal Vaccination Uptake Among Adults with Heart Disease

Background: Health information technology (HIT) may influence pneumococcal vaccination uptake in high-risk populations. This study assessed the association of HIT utilization on pneumococcal vaccine (PCV) uptake among adults ≥40 years with heart disease. Methods: This was a cross-sectional study of 2,134 individuals representing 16,813,593 United States adults ≥40 years with heart disease using the National Health Interview Survey data. The independent variables were use of the Internet to (1) look up health information, (2) fill a prescription, and (3) schedule a medical appointment, and use of an e-mail (4) communicate with a health care provider. The dependent variable was PCV uptake. Chi-square analysis was used to evaluate group differences, and a multiple logistic regression was used to analyze the association between HIT utilization and PCV uptake. Results: Those who use the Internet to fill up a prescription and to communicate with their health care provider were more likely to take up the PCV (adjusted odds ratio [AOR] 1.56; 95% confidence interval [CI] 1.03-2.37, p = 0.035) and (AOR 1.95; 95% CI 1.23-3.10, p = 0.005) respectively. Compared with those who did not use HIT in any form, those who used HIT in at least three or four forms had a higher PCV uptake (AORs 1.93; 95% CI 1.19-3.13, p = 0.008) and (AOR 2.33 95% CI 1.22-4.47, p = 0.011) respectively. Conclusion: Our analysis shows a positive association of HIT utilization and PCV uptake. It further stresses the importance of electronic health in preventive medicine. This implies that HIT can be used purposively in other aspects of preventive health. Larger studies should evaluate the relationship between different uses of HIT and the uptake of different vaccines.

Vitamin D Modulation of the Innate Immune Response to Paediatric Respiratory Pathogens Associated with Acute Lower Respiratory Infections

Vitamin D is an essential component of immune function and childhood deficiency is associated with an increased risk of acute lower respiratory infections (ALRIs). Globally, the leading childhood respiratory pathogens are Streptococcus pneumoniae, respiratory syncytial virus and the influenza virus. There is a growing body of evidence describing the innate immunomodulatory properties of vitamin D during challenge with respiratory pathogens, but recent systematic and unbiased synthesis of data is lacking, and future research directions are unclear. We therefore conducted a systematic PubMed literature search using the terms “vitamin D” and “Streptococcus pneumoniae” or “Respiratory Syncytial Virus” or “Influenza”. A priori inclusion criteria restricted the review to in vitro studies investigating the effect of vitamin D metabolites on human innate immune cells (primary, differentiated or immortalised) in response to stimulation with the specified respiratory pathogens. Eleven studies met our criteria. Despite some heterogeneity across pathogens and innate cell types, vitamin D modulated pathogen recognition receptor (PRRs: Toll-like receptor 2 (TLR2), TLR4, TLR7 and nucleotide-binding oligomerisation domain-containing protein 2 (NOD2)) expression; increased antimicrobial peptide expression (LL-37, human neutrophil peptide (HNP) 1-3 and β-defensin); modulated autophagosome production reducing apoptosis; and modulated production of inflammatory cytokines (Interleukin (IL) -1β, tumour necrosis factor-α (TNF-α), interferon-ɣ (IFN-ɣ), IL-12p70, IFN-β, Regulated on Activation, Normal T cell Expressed (RANTES), IL-10) and chemokines (IL-8 and C-X-C motif chemokine ligand 10 (CXCL10)). Differential modulation of PRRs and IL-1β was reported across immune cell types; however, this may be due to the experimental design. None of the studies specifically focused on immune responses in cells derived from children. In summary, vitamin D promotes a balanced immune response, potentially enhancing pathogen sensing and clearance and restricting pathogen induced inflammatory dysregulation. This is likely to be important in controlling both ALRIs and the immunopathology associated with poorer outcomes and progression to chronic lung diseases. Many unknowns remain and further investigation is required to clarify the nuances in vitamin D mediated immune responses by pathogen and immune cell type and to determine whether these in vitro findings translate into enhanced immunity and reduced ALRI in the paediatric clinical setting.