Generating enhanced mucosal immunity against Bordetella pertussis: current challenges and new directions

Robust immune responses to intranasal vaccine targeting Bordetella pertussis antigens to claudin-4 on mucosal microfold cells

Despite high global vaccination rates, pertussis remains uncontrolled and is increasing in many regions. The present study aimed to develop an intranasal (I.N.) vaccine (F1S1-C-CPE) against Bordetella (B.) pertussis. This vaccine comprises the C-terminal fragment of Clostridium perfringens enterotoxin (C-CPE) fused with F1S1 antigen, which consists of the S1 subunit of pertussis toxin and the immunodominant domain of filamentous hemagglutinin (F1). C-CPE specifically targets Claudin-4 on mucosal microfold cells, which enhances immune response at the site of infection. We evaluated the immunogenicity and protective efficacy of this construct following I.N. immunization in BALB/c mice. Significant differences in serum IgG and IgA, as well as lung IgA levels were observed among mice immunized with F1S1, CPE + F1S1, F1S1-C-CPE, and PBS (p < 0.0001). Notably, the F1S1-C-CPE group exhibited significantly higher levels of IgA in both serum and lung extracts compared to the F1S1 or CPE + F1S1 groups (p < 0.05). Moreover, analysis of cell-mediated responses indicated that IFN-γ and IL-17 levels were highest in group F1S1-C-CPE, significantly exceeding those in the F1S1, F1S1+C-CPE groups (p < 0.001). Cytokine profile analysis in lung tissue post-challenge indicated the greatest fold increases in mRNA levels of IFN-γ, IL-6, IL-17, and IL-10 in group F1S1-C-CPE (p < 0.0001). The challenge results indicated that I.N. immunization with F1S1-C-CPE protein effectively controls B. pertussis infection (p < 0.0001). The results indicate the development of mucosal and systemic humoral and Th1/Th17 responses, which are critical in controlling infection. Overall, our findings highlight the potential of the F1S1-C-CPE I.N. vaccine as a powerful tool in combating pertussis.

Clinical and Epidemiological Characteristics of Pediatric Pertussis Cases: A Retrospective Study from Southeast Romania

Background/Objectives: Pertussis remains a significant cause of respiratory illness in children, particularly in regions with suboptimal vaccination coverage. This retrospective study analyzes the clinical presentations, co-infections, treatment, and outcomes of pediatric patients diagnosed with Bordetella pertussis at the Constanța County Clinical Emergency Hospital "St. Apostle Andrew" between 1 January and 30 September 2024. Methods: Thirty-eight children, predominantly under the age of 3 years (81.58%), were included. Demographic data, clinical features, coinfecting pathogens, antimicrobial regimens, and hospital outcomes were reviewed. Results: Only 7 out of 38 children (18.42%) had received pertussis vaccination, and none benefited from maternal immunization. The highest incidence occurred in infants under 1 year (44.74%). Intensive care was required in 18.42% of cases, and macrolides were the most frequently used antibiotics (68.42%). Co-detection of respiratory pathogens-particularly Streptococcus pneumoniae, enteroviruses, and human rhinoviruses-was common. Severe cases often exhibited hyperleukocytosis, which was associated with complications such as heart failure. Conclusions: These findings underscore the need for timely recognition and management of pertussis and its complications. Although macrolides remain the first-line therapy, adjunctive treatments like leukoreduction may be considered in critical cases. The persistence of pertussis despite vaccination efforts highlights the challenges posed by waning immunity and diagnostic limitations, reinforcing the need for strengthened public health strategies.

Pertussis in Southeast Asia: country-level burden and recommendations from the Global Pertussis Initiative

The Global Pertussis Initiative met in March 2024 to discuss the burden of pertussis and prevention efforts in six Southeast Asian countries: Cambodia, Indonesia, Malaysia, Singapore, Thailand, and Vietnam. Except for Cambodia, pertussis is a notifiable disease; data accuracy varies within and between countries. Most cases in the region are diagnosed based on clinical suspicion. Whole-cell and acellular pertussis combination vaccines are available, but the composition differs between countries. Immunization against pertussis is well-established, but policies regarding boosting vary. Vaccination in pregnancy represents a still-neglected opportunity to protect infants. The Global Pertussis Initiative recommends enacting vaccination in pregnancy in countries without and increasing coverage in countries with policies already in place. There is a need to correct the misperception that pertussis affects children exclusively and that childhood vaccines provide lifelong protection. Education is key to widespread understanding of the threat of pertussis and removing barriers to vaccination in Southeast Asia.

Maternal vaccination: shaping the neonatal response to pertussis

Antepartum maternal vaccination can protect highly sensitive newborns before they are old enough to receive their own vaccines. Two vaccines are currently recommended during pregnancy: the flu vaccine and the Tdap vaccine against tetanus, diphtheria, and pertussis. Although there is strong evidence that maternal vaccination works to protect the offspring, limitations in the understanding of vaccines and of maternal transfer of immunity compound to obscure our understanding of how they work. Here we focus on the example of pertussis to explore the possible mechanisms involved in the transfer of protection to offspring and how these may impact the newborn's response to future exposure to pertussis. For example, Tdap vaccines induce pathogen specific antibodies, and those antibodies are known to be transferred from mother to the fetus in utero and to the newborn via milk. But antibodies alone have modest impact on pertussis disease, and even less effect on colonization/transmission. Maternal immune cells can also be transferred to offspring and may play a direct role in protection from disease and/or influence the developing neonatal immune system. However, some of the transferred immunity may also blunt the offspring's response to subsequent vaccination. In this review we will summarize the protection conferred to offspring by maternal vaccination against pertussis and the likely mechanisms by which protection is transferred, identifying the many knowledge gaps that limit our most effective application of this approach.