UspA2 is a cross-protective Moraxella catarrhalis vaccine antigen

Pathogenicity and Bro gene typing of pediatric lower respiratory tract infections with Moraxella catarrhalis in Southwest Shandong, China

To investigate the etiology and clinical characteristics of Moraxella catarrhalis infections in the lower respiratory tract among pediatric patients in southwestern Shandong Province, China. This study aims to enhance early identification and diagnostic accuracy for laboratory physicians, while providing evidence to guide clinical diagnosis and treatment of Moraxella catarrhalis-related infections. This retrospective cohort study analyzed pediatric patients with Moraxella catarrhalis lower respiratory tract infections in southwestern Shandong Province, China. Clinical isolates were obtained through standardized sputum/bronchoalveolar lavage collection protocols and subjected to microbiological identification, antimicrobial susceptibility testing, and molecular characterization of β-lactamase production and bro gene variants. Epidemiological patterns and clinical profiles were systematically evaluated using electronic medical record data spanning January 2020 to December 2023. During the 4-year surveillance period (2018-2021), Moraxella catarrhalis was isolated from 848 pediatric cases of lower respiratory tract infections, representing a 7.81% overall detection rate. Age-stratified analysis revealed the highest prevalence in infants aged 28 days to 1 year (9.69%), with significant seasonal variation peaking in the fourth quarter (11.58%, p < 0.05). Monomicrobial infections predominated (79.72%, 676/848), while polymicrobial cases (20.28%, 172/848) predominantly co-occurred with Streptococcus pneumoniae and Haemophilus influenzae. All isolates were confirmed through parallel testing using automated biochemical analyzers and MALDI-TOF mass spectrometry. Antimicrobial susceptibility profiling demonstrated complete susceptibility to ceftazidime, cefepime, and imipenem (100%), with ≥ 95% susceptibility rates to ciprofloxacin (98.2%), levofloxacin (97.6%), ceftriaxone (96.8%), cefuroxime (96.1%), tetracycline (95.4%), and chloramphenicol (95.1%). A concerning temporal escalation in erythromycin resistance was observed (69.73% in 2018 vs. 90.57% in 2021, χ²=41.32, p < 0.001), while ampicillin and clindamycin resistance remained persistently high (> 93% across all years).β-lactamase production was detected in 96.58% (819/848) of isolates, with molecular characterization identifying bro-1 (94.51%, 774/819) and bro-2 (5.49%, 45/819) gene variants. The β-lactamase-negative subgroup (3.42%, 29/848) showed no significant epidemiological clustering. Our surveillance study demonstrates that Moraxella catarrhalis lower respiratory tract infections in southwestern Shandong Province predominantly affect infants aged 28 days to 1 year, with significantly elevated seasonal incidence during the fourth quarter. Notably, we observed a concerning temporal escalation in erythromycin resistance and persistently high resistance rates to ampicillinand clindamycin throughout the 2018-2021 surveillance period. Crucially, β-lactamase hyperproduction particularly BRO-1 gene carriage emerged as the principal resistance mechanism against β-lactams, while maintained susceptibility to expanded-spectrum cephalosporins and carbapenems suggests preserved therapeutic options. These findings underscore the necessity for: Avoidance of macrolides and β-lactam/β-lactamase inhibitor combinations in empirical therapy; Continuous monitoring of BRO gene evolution patterns; Age-specific antimicrobial stewardship programs targeting infant populations.

Type 5 secretion system antigens as vaccines against Gram-negative bacterial infections

Infections caused by Gram-negative bacteria are leading causes of mortality worldwide. Due to the rise in antibiotic resistant strains, there is a desperate need for alternative strategies to control infections caused by these organisms. One such approach is the prevention of infection through vaccination. While live attenuated and heat-killed bacterial vaccines are effective, they can lead to adverse reactions. Newer vaccine technologies focus on utilizing polysaccharide or protein subunits for safer and more targeted vaccination approaches. One promising avenue in this regard is the use of proteins released by the Type 5 secretion system (T5SS). This system is the most prevalent secretion system in Gram-negative bacteria. These proteins are compelling vaccine candidates due to their demonstrated protective role in current licensed vaccines. Notably, Pertactin, FHA, and NadA are integral components of licensed vaccines designed to prevent infections caused by Bordetella pertussis or Neisseria meningitidis. In this review, we delve into the significance of incorporating T5SS proteins into licensed vaccines, their contributions to virulence, conserved structural motifs, and the protective immune responses elicited by these proteins.

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.

Insights from targeting transferrin receptors to develop vaccines for pathogens of humans and food production animals

While developing vaccines targeting surface transferrin receptor proteins in Gram-negative pathogens of humans and food production animals, the common features derived from their evolutionary origins has provided us with insights on how improvements could be implemented in the various stages of research and vaccine development. These pathogens are adapted to live exclusively on the mucosal surfaces of the upper respiratory or genitourinary tract of their host and rely on their receptors to acquire iron from transferrin for survival, indicating that there likely are common mechanisms for delivering transferrin to the mucosal surfaces that should be explored. The modern-day receptors are derived from those present in bacteria that lived over 320 million years ago. The pathogens represent the most host adapted members of their bacterial lineages and may possess factors that enable them to have strong association with the mucosal epithelial cells, thus likely reside in a different niche than the commensal members of the bacterial lineage. The bacterial pathogens normally lead a commensal lifestyle which presents challenges for development of relevant infection models as most infection models either exclude the early stages of colonization or subsequent disease development, and the immune mechanisms at the mucosal surface that would prevent disease are not evident. Development of infection models emulating natural horizontal disease transmission are also lacking. Our aim is to share our insights from the study of pathogens of humans and food production animals with individuals involved in vaccine development, maintaining health or regulation of products in the human and animal health sectors.

FHUSPA2/10 is a bactericidal monoclonal antibody targeting multiple repeated sequences of Moraxella catarrhalis UspA2

Moraxella catarrhalis is an important and common respiratory pathogen that can cause Otitis Media, Community Acquired Pneumonia, and has been associated with an increased risk of exacerbations in chronic obstructive pulmonary disease in adults, leading to morbidity and mortality. Its ubiquitous surface protein A2 (UspA2) has been shown to interact with host structures and extracellular matrix proteins, suggesting a role at an early stage of infection and a contribution to bacterial serum resistance. The UspA proteins are homo-trimeric autotransporters that appear as a lollipop-shaped structure in electron micrographs. They are composed of an N-terminal head with adhesive properties, followed by a stalk, which ends by an amphipathic helix and a C-terminal membrane domain. The three family members UspA1, UspA2 and UspA2H, present different amino acid signatures both at the head and membrane-spanning regions. By combining electron microscopy, hydrogen deuterium exchange mass spectrometry and protein modeling, we identified a shared and repeated epitope recognized by FHUSPA2/10, a potent cross-bactericidal monoclonal antibody raised by UspA2 and deduced key amino acids involved in the binding. The finding strengthens the potential of UspA2 to be incorporated in a vaccine formulation against M. catarrhalis.

A detailed analysis of possible efficacy signals of NTHi-Mcat vaccine against severe COPD exacerbations in a previously reported randomised phase 2b trial

BACKGROUND

An investigational vaccine containing non-typeable Haemophilus influenzae (NTHi) and Moraxella catarrhalis (Mcat) surface proteins did not show vaccine efficacy (VE) against combined moderate and severe (moderate/severe) exacerbations in a randomised, observer-blinded, placebo-controlled phase 2b trial of patients with chronic obstructive pulmonary disease (COPD). Nevertheless, observations on rates of severe exacerbations and hospitalisations encouraged further evaluation.

METHODS

Patients with stable COPD (moderate to very severe airflow limitation, Global Initiative for Chronic Obstructive Lung Disease [GOLD] stage 2-4), 40-80 years and at least one moderate/severe exacerbation in the last year received two doses of NTHi-Mcat vaccine or placebo plus standard care. Secondary analyses were conducted on VE against exacerbations according to severity. Potential predictive factors at baseline for VE against severe exacerbations were explored in post-hoc analyses.

RESULTS

Of 606 patients enrolled, 571 were included in the efficacy analysis (279 in NTHi-Mcat vaccine group, 292 in placebo group). VE against severe acute exacerbations of COPD (AECOPD) in various subgroups was 52.11 % (p = 0.015; frequent exacerbators), 65.43 % (p = 0.015; baseline GOLD grade 4), 38.24 % (p = 0.034; previous pneumococcal and/or influenza vaccination). VE was 52.49 % (p = 0.044) for the 6-12 months period after 1 month post-dose 2. Multivariable analysis identified two factors (frequent exacerbator status plus inhaled corticosteroid use at baseline) associated with significant VE against severe AECOPD; in this subpopulation, VE was 74.99 % (p < 0.001).

CONCLUSION

Results suggest potential efficacy with the NTHi-Mcat vaccine against severe exacerbations in certain patients with COPD, in particular those who have frequent exacerbations and use inhaled corticosteroids. This potential signal requires confirmation in an appropriately designed prospective clinical trial.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03281876.

Evaluation of respiratory tract bacterial co-infections in SARS-CoV-2 patients with mild or asymptomatic infection in Lagos, Nigeria

BACKGROUND

A common complication of any respiratory disease by a virus could be a secondary bacterial infection, which is known to cause an increase in severity. It is, however, not clear whether the presence of some opportunistic pathogens called pathobionts contributes to the severity of the disease. In COVID-19 patients, undetected bacterial co-infections may be associated with the severity of the disease. Therefore, we investigated the implications of bacterial co-infections in COVID-19 cases.

RESULTS

This is a cross-sectional study that involved archived specimens collected from nasopharyngeal samples of 150 people for COVID-19 screening in Lagos. DNA extraction from the samples was carried out to determine the presence of five respiratory bacterial pathogens using nested real-time PCR, and data were analysed using the Chi-square test. Of the 150 samples collected, 121 (80.7%) were positive for SARs-CoV-2 infection and 29 were negative. The proportion of patients with bacteria co-infection in COVID-19-negative, asymptomatic, and mild cases were 93.1%, 70.7%, and 67.5%, respectively. There was no statistically significant difference between mild COVID-19 conditions and bacteria co-infection (p = 0.097). There was also no significant difference in the nasal carriage of Staphylococcus aureus, Mycoplasma pneumoniae, and Haemophilus spp. However, there was a statistically significant increase in the carriage of Moraxella catarrhalis and Chlamydophila pneumoniae among COVID-19-negative patients when compared with the positive patients (p value = 0.003 and 0.000 for Moraxella catarrhalis and Chlamydophila pneumoniae, respectively).

CONCLUSIONS

The current study shows that bacterial co-infection and superinfection with COVID-19 are not associated with mild and asymptomatic COVID-19 cases in our setting. However, given the high prevalence of Staphylococcus aureus and Mycoplasma pneumoniae among the mild COVID-19 cases seen in this study, early diagnosis and treatment of these bacterial co-infections are still encouraged to mitigate the effect on the severity of COVID-19.

Long-term immunogenicity and safety of a non-typeable Haemophilus influenzae-Moraxella catarrhalis vaccine: 4-year follow-up of a phase 1 multicentre trial

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Older adults with smoking history received two doses of combined NTHi-Mcat vaccine.

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We evaluated antibody persistence during 4 years of follow-up after vaccination.

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Immune responses against the NTHi protein antigens persisted up to 4 years.

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There was no persistent immune response against the Mcat antigen.

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No safety concerns were identified during the long-term follow-up period.

A multicomponent vaccine has been developed to reduce the frequency of acute exacerbations of COPD associated with non-typeable Haemophilus influenzae (NTHi) and Moraxella catarrhalis (Mcat) infections, containing NTHi (PD and PE-PilA) and Mcat (UspA2) surface proteins. In a randomised, observer-blind, placebo-controlled study with two steps (NCT02547974), the investigational vaccine had good immunogenicity and no safety concerns were identified. In step 2, 90 adults aged 50–71 years with smoking history received two doses 60 days apart of one of two AS01_E-adjuvanted formulations containing 10 µg of each antigen (10–10-AS01) or 10 µg NTHi antigens and 3.3 µg UspA2 (10–3-AS01), or placebo. Long-term persistence of antigen-specific humoral antibodies was assessed in 81 participants during 3 years of follow-up after the initial 14-month study (NCT03201211).

Antigen-specific antibody concentrations were measured in blood samples taken every 6 months. Safety monitoring evaluated serious adverse events (SAEs) and potential immune-mediated disease (pIMD).

Immune responses against NTHi antigens persisted up to 4 years post-vaccination. For PD, PE and PilA, at each follow-up time point, adjusted antibody geometric mean concentrations (GMCs) were higher (non-overlapping 95% confidence intervals [CIs]) in the vaccine groups versus placebo and versus pre-vaccination. Antibody GMC point estimates were higher with 10–3-AS01 than with 10–10-AS01. For UspA2, 95% CIs included 1 for GMC ratios of 10–10-AS01 or 10–3-AS01 to placebo at each time point. During follow-up, SAEs were reported in nine (11.1%) participants, one of which was fatal (lung cancer, 607 days after second 10–10-AS01 dose). One non-serious pIMD, trigeminal neuralgia, was reported 771 days after second 10–3-AS01 dose. The SAEs and pIMD were considered not related to vaccination.

Immune responses against NTHi antigens persisted for 4 years after two-dose vaccination with the investigational NTHi-Mcat vaccine. There was no persistent response against the Mcat antigen. No safety concerns were identified during the long-term follow-up.