Immunogenicity and mechanisms of action of PnuBioVax, a multi-antigen serotype-independent prophylactic vaccine against infection with Streptococcus pneumoniae

Preliminary Evaluation of the Safety and Immunogenicity of a Novel Protein-Based Pneumococcal Vaccine in Healthy Adults Aged 18-49: A Phase Ia Randomized, Double Blind, Placebo-Controlled Clinical Study

Background: Protein-based pneumococcal vaccines (PBPVs) may offer expanded protection against Streptococcus pneumoniae and tackle the antimicrobial resistance crisis in pneumococcal infections. This study examined the safety and immunogenicity in healthy adults vaccinated with three doses of a protein-based pneumococcal vaccine containing pneumococcal surface protein A (PspA) (PRX1, P3296 and P5668) and in combination with a recombinant detoxified pneumolysin protein (PlyLD). Methods: This phase Ia randomized, double blind, placebo-controlled clinical study enrolled healthy adults aged 18-49 years. The participants were randomized into experimental (low-dose, medium-dose, high-dose) and placebo groups in a ratio of 3:1. Three doses of investigational vaccine were given to the participants with an interval of two months. Safety endpoints included the occurrence of total adverse reactions, solicited local and systemic adverse reactions, unsolicited adverse reactions, serious adverse events (SAEs), and several laboratory parameters. Immunogenicity endpoints included geometric mean titers (GMT) of anti-PspA (PRX1, P3296 and P5668) and anti-PlyLD antibodies level as determined by ELISA, seropositivity rates of PspA and PlyLD antibodies (>4-fold increase) and neutralization activity of anti-Ply antibody in serum. Results: A total of 118 participants completed the study of three doses. The candidate PBPV was safe and well-tolerated in all experimental groups. No vaccine-related SAEs were observed in this study. Most solicited adverse reactions were mild and transient. The most frequently reported solicited adverse reactions in the medium- and high-dose groups was pain at the injection site, while in the low-dose group it was elevated blood pressure. The immunogenicity data showed a sharp increase in the GMT level of anti-PspA-RX1, anti-PspA-3296, anti-PspA-5668, and anti-PlyLD antibodies in serum. The results also showed that the elicited antibodies were dosage-dependent. The high-dose group showed a higher immune response against PspA-RX1, PspA-3296, PspA-5668, and PlyLD antigens. However, repeat vaccination did not increase the level of anti-PspA antibodies but the level of anti-PlyLD antibody. High seropositivity rates were also observed for anti-PspA-RX1, anti-PspA-3296, anti-PspA-5668, and anti-PlyLD antibodies. In addition, a significant difference in the GMT levels of anti-Ply antibody between the high-, medium-, and low-dose groups post each vaccination were indicated by neutralization activity tests. Conclusions: The PBPV showed a safe and immunogenic profile in this clinical trial. Taking into consideration both safety and immunogenicity data, we propose a single dose of 50 µg (medium dose) of PBPV as the optimum approach in providing expanded protection against Streptococcus pneumoniae.

Bacterial Vaccinations in Patients with Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a frequent, often progressive, chronic disease of the lungs. Patients with COPD often have impaired immunity; therefore, they are prone to chest infections, such as pneumonia or bronchitis. Acute exacerbations of COPD are major events that accelerate disease progression, contributing to its symptoms' burden, morbidity, and mortality. Both pneumonia and acute exacerbations in COPD are caused by bacteria against which there are effective vaccinations. Although the number of randomised controlled studies on bacterial vaccinations in COPD is limited, national and international guidelines endorse specific vaccinations in patients with COPD. This review will summarise the different types of vaccinations that prevent pneumonia and COPD exacerbations. We also discuss the results of early phase studies. We will mainly focus on Streptococcus pneumoniae, as this bacterium was predominantly investigated in COPD. However, we also review studies investigating vaccinations against Haemophilus influenzae, Moraxella catarrhalis, and Bordetella pertussis.

Otitis media: recent advances in otitis media vaccine development and model systems

Otitis media is an inflammatory disorder of the middle ear caused by airways-associated bacterial or viral infections. It is one of the most common childhood infections as globally more than 80% of children are diagnosed with acute otitis media by 3 years of age and it is a common reason for doctor's visits, antibiotics prescriptions, and surgery among children. Otitis media is a multifactorial disease with various genetic, immunologic, infectious, and environmental factors predisposing children to develop ear infections. Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis are the most common culprits responsible for acute otitis media. Despite the massive global disease burden, the pathogenesis of otitis media is still unclear and requires extensive future research. Antibiotics are the preferred treatment to cure middle ear infections, however, the antimicrobial resistance rate of common middle ear pathogens has increased considerably over the years. At present, pneumococcal and influenza vaccines are administered as a preventive measure against otitis media, nevertheless, these vaccines are only beneficial in preventing carriage and/or disease caused by vaccine serotypes. Otitis media caused by non-vaccine serotype pneumococci, non-typeable H. influenza, and M. catarrhalis remain an important healthcare burden. The development of multi-species vaccines is an arduous process but is required to reduce the global burden of this disease. Many novel vaccines against S. pneumoniae, non-typeable H. influenza, and M. catarrhalis are in preclinical trials. It is anticipated that these vaccines will lower the disease burden and provide better protection against otitis media. To study disease pathology the rat, mouse, and chinchilla are commonly used to induce experimental acute otitis media to test new therapeutics, including antibiotics and vaccines. Each of these models has its advantages and disadvantages, yet there is still a need to develop an improved animal model providing a better correlated mechanistic understanding of human middle ear infections, thereby underpinning the development of more effective otitis media therapeutics. This review provides an updated summary of current vaccines against otitis media, various animal models of otitis media, their limitations, and some future insights in this field providing a springboard in the development of new animal models and novel vaccines for otitis media.

Non-capsular based immunization approaches to prevent Streptococcus pneumoniae infection

Streptococcus pneumoniae is a Gram-positive bacterium and the leading cause of bacterial pneumonia in children and the elderly worldwide. Currently, two types of licensed vaccines are available to prevent the disease caused by this pathogen: the 23-valent pneumococcal polysaccharide-based vaccine and the 7-, 10, 13, 15 and 20-valent pneumococcal conjugate vaccine. However, these vaccines, composed of the principal capsular polysaccharide of leading serotypes of this bacterium, have some problems, such as high production costs and serotype-dependent effectiveness. These drawbacks have stimulated research initiatives into non-capsular-based vaccines in search of a universal vaccine against S. pneumoniae. In the last decades, several research groups have been developing various new vaccines against this bacterium based on recombinant proteins, live attenuated bacterium, inactivated whole-cell vaccines, and other newer platforms. Here, we review and discuss the status of non-capsular vaccines against S. pneumoniae and the future of these alternatives in a post-pandemic scenario.

Development of Next Generation Streptococcus pneumoniae Vaccines Conferring Broad Protection

Streptococcus pneumoniae is a major pathogen causing pneumonia with over 2 million deaths annually, especially in young children and the elderly. To date, at least 98 different pneumococcal capsular serotypes have been identified. Currently, the vaccines for prevention of S. pneumoniae infections are the 23-valent pneumococcal polysaccharide-based vaccine (PPV23) and the pneumococcal conjugate vaccines (PCV10 and PCV13). These vaccines only cover some pneumococcal serotypes and are unable to protect against non-vaccine serotypes and unencapsulated S. pneumoniae. This has led to a rapid increase in antibiotic-resistant non-vaccine serotypes. Hence, there is an urgent need to develop new, effective, and affordable pneumococcal vaccines, which could cover a wide range of serotypes. This review discusses the new approaches to develop effective vaccines with broad serotype coverage as well as recent development of promising pneumococcal vaccines in clinical trials. New vaccine candidates are the inactivated whole-cell vaccine strain (Δpep27ΔcomD mutant) constructed by mutations of specific genes and several protein-based S. pneumoniae vaccines using conserved pneumococcal antigens, such as lipoprotein and surface-exposed protein (PspA). Among the vaccines in Phase 3 clinical trials are the pneumococcal conjugate vaccines, PCV-15 (V114) and 20vPnC. The inactivated whole-cell and several protein-based vaccines are either in Phase 1 or 2 trials. Furthermore, the recent progress of nanoparticles that play important roles as delivery systems and adjuvants to improve the performance, as well as the immunogenicity of the nanovaccines, are reviewed.

Next-Generation Whole-Cell Pneumococcal Vaccine

Streptococcus pneumoniae remains a major public health hazard. Although Pneumococcal Conjugate Vaccines (PCVs) are available and have significantly reduced the rate of invasive pneumococcal diseases, there is still a need for new vaccines with unlimited serotype coverage, long-lasting protection, and lower cost to be developed. One of the most promising candidates is the Whole-Cell Pneumococcal Vaccine (WCV). The new generation of whole-cell vaccines is based on an unencapsulated serotype that allows the expression of many bacterial antigens at a lower cost than a recombinant vaccine. These vaccines have been extensively studied, are currently in human trial phase 1/2, and seem to be the best treatment choice for pneumococcal diseases, especially for developing countries.

Measurement of Typhim Vi IgG as a Diagnostic Tool to Determine Anti-polysaccharide Antibody Production Deficiency in Children

Background: The assessment of specific polysaccharide antibody production plays a pivotal role in the diagnosis of humoral primary immunodeficiencies (PID). The response to 23-valent pneumococcal vaccine (PPV) remains the gold standard for the diagnosis of polysaccharide antibodies. However, in Spain, the interpretation of pure polysaccharide 23-valent immunization is hampered by the high endemicity of pneumococcal disease and the generalization of the 13-valent adjuvant pneumococcal vaccination. Specific Typhim Vi vaccination (TV) immunoglobulin G IgG response to immunization is useful in adult PID, but there is no data regarding children. Objectives: To evaluate the clinical utility of TV IgG production as a diagnostic tool to determine anti-polysaccharide antibody production deficiency in children, when the response to PPV is unclear and isolated determination of serotypes is unfeasible. Methods: We conducted a single-institution prospective observational study on 61 children with recurrent infections. Baseline specific antibodies against PPV and TV were evaluated. In 28 children (46%), the response to the production of antibodies confirmed a clinical suspicion of humoral PID, and they were therefore immunized with 23-valent pneumococcal vaccine and Typhim Vi. Both specific antibody responses were measured by ELISA (The Binding Site Group Ltd, Birmingham, UK) using previously published cut-offs. Results: Seventy percent of the 61 children displayed baseline PPV IgG > 27 mg/L, whereas only 8% showed TV IgG > 28 U/mL (p < 0.0001). Twenty-one of 28 children (75%) achieved a 3-fold increase in post-vaccination TV IgG levels, whereas only 3% achieved a 4-fold increase in PPV IgG post vaccination, mainly due to high baseline PPV IgG titers. When we classified children according to their response to TV as responders or non-responders and compared this with the well-known clinical warning signs of the Jeffrey Modell Foundation. The proportions of children with history of pneumonia and the need for intravenous antibiotics were significantly higher in TV IgG non-responders than in TV IgG responders (p = 0.02 and p = 0.01, respectively). Conclusion: Response to TV can be considered an ancillary diagnostic tool to determine polysaccharide antibodies in children, particularly when isolated determination of pneumococcal serotypes is not feasible. TV provides a useful asset for clinicians in the era of conjugate PPV vaccination, with clinical relevance. Further research is warranted for validation.