Protective effects of vaccines against Bordetella parapertussis in a mouse intranasal challenge model

Pertussis Vaccines Scarcely Provide Protection against Bordetella parapertussis Infection in Children-A Systematic Review and Meta-Analysis

BACKGROUND

Pertussis, or whooping cough, is a global public health concern. Pertussis vaccines have demonstrated good protection against Bordetella pertussis infections, but their effectiveness against Bordetella parapertussis remains debated due to conflicting study outcomes.

METHODS

A systematic review and meta-analysis were conducted to assess the effectiveness of pertussis vaccines in protecting children against B. parapertussis infection. A comprehensive search of PubMed, Web of Science, and Scopus databases was conducted, and randomized controlled trials (RCTs) and observational studies that met inclusion criteria were included in the analysis.

RESULTS

The meta-analysis, involving 46,533 participants, revealed no significant protective effect of pertussis vaccination against B. parapertussis infection (risk ratio: 1.10, 95% confidence interval: 0.83 to 1.44). Subgroup analyses by vaccine type and study design revealed no significant protection. The dearth of recent data and a limited pool of eligible studies, particularly RCTs, underscore a critical gap that warrants future research in the domain.

CONCLUSIONS

These findings offer crucial insights into the lack of effectiveness of pertussis vaccines against B. parapertussis. Given the rising incidence of cases and outbreaks, coupled with the lack of cross-protection by the existing vaccines, there is an urgent need to develop vaccines that include specific antigens to protect against B. parapertussis.

Adjuvant Efficacy of the ECMS-Oil on Immune Responses against Bordetella bronchiseptica in Mice through the TLR2/MyD88/NF-κB Pathway

Bordetella infection can be efficiently prevented through vaccination. The current study investigated the effects of an extract of Cochinchina momordica seed (ECMS) combined with oil on the immune responses to the inactivated Bordetella vaccine in mice. Serum IgG and IgG1 level was significantly increased in ECMS-oil group compared to any other group ( $P<0.05$ ) 2 weeks after immunization, while groups ECMS200 μg/400 μg-oil had a markedly higher level of serum IgG2b and IgG3 than any other groups ( $P<0.05$ ). Moreover, lipopolysaccharide/ConA-stimulated proliferation of splenocytes was significantly enhanced in ECMS 400 μg-oil immunized mice in comparison with mice in any other group ( $P<0.05$ ). RT-PCR assay revealed that while ECMS800 μg-oil group had significantly higher levels of serum IL-4, IL-10, Toll-like receptor (TLR)2, and IL-1 beta than any other group ( $P<0.05$ ), the levels of serum IL-2, IL-4, and IL-10 were markedly increased in ECMS 400 μg-oil group as compared to any other groups ( $P<0.05$ ). Blood analysis showed that ECMS800 μg-oil and oil groups had a significantly higher number of immunocytes than any other groups ( $P<0.05$ ). There were significant differences in the number of IgG+, IgG2b+, and IgA+ cells in the lung between ECMS800 μg-oil group and any other groups ( $P<0.05$ ). Western blot analysis demonstrated that stimulation with ECMS 25 μg/mL or 50 ng/mL led to a significant increase in the expression of TLR2, MyD88, and NF-κB in Raw264.7 cells ( $P<0.05$ ). Compared with any other group, the expression of MyD88 was markedly increased in the cells stimulated with ECMS 50 ng/mL, as indicated by the RT-PCR analysis ( $P<0.05$ ). Overall, we observed that ECMS-oil efficiently enhanced the humoral or cellular immune responses against Bordetella and suggested that the mechanism of adjuvant activity of ECMS-oil might involve TLR2/MyD88/NF-κB signaling pathway.

Conserved Patterns of Symmetric Inversion in the Genome Evolution of Bordetella Respiratory Pathogens

Whooping cough (pertussis), primarily caused by Bordetella pertussis, has resurged in the United States, and circulating strains exhibit considerable chromosome structural fluidity in the form of rearrangement and deletion. The genus Bordetella includes additional pathogenic species infecting various animals, some even causing pertussis-like respiratory disease in humans; however, investigation of their genome evolution has been limited. We studied chromosome structure in complete genome sequences from 167 Bordetella species isolates, as well as 469 B. pertussis isolates, to gain a generalized understanding of rearrangement patterns among these related pathogens. Observed changes in gene order primarily resulted from large inversions and were only detected in species with genomes harboring multicopy insertion sequence (IS) elements, most notably B. holmesii and B. parapertussis While genomes of B. pertussis contain >240 copies of IS481, IS elements appear less numerous in other species and yield less chromosome structural diversity through rearrangement. These data were further used to predict all possible rearrangements between IS element copies present in Bordetella genomes, revealing that only a subset is observed among circulating strains. Therefore, while it appears that rearrangement occurs less frequently in other species than in B. pertussis, these clinically relevant respiratory pathogens likely experience similar mutation of gene order. The resulting chromosome structural fluidity presents both challenges and opportunity for the study of Bordetella respiratory pathogens.IMPORTANCE Bordetella pertussis is the primary agent of whooping cough (pertussis). The Bordetella genus includes additional pathogens of animals and humans, including some that cause pertussis-like respiratory illness. The chromosome of B. pertussis has previously been shown to exhibit considerable structural rearrangement, but insufficient data have prevented comparable investigation in related species. In this study, we analyze chromosome structure variation in several Bordetella species to gain a generalized understanding of rearrangement patterns in this genus. Just as in B. pertussis, we observed inversions in other species that likely result from common mutational processes. We used these data to further predict additional, unobserved inversions, suggesting that specific genome structures may be preferred in each species.

Outer-Membrane-Vesicle-Associated O Antigen, a Crucial Component for Protecting Against Bordetella parapertussis Infection

Bordetella parapertussis is a respiratory-disease pathogen producing symptomatology similar to that of pertussis but of underestimated incidence and with no specific vaccine existing. We recently designed a vaccine candidate from B. parapertussis outer-membrane vesicles (OMVs) that proved to be safe and protective in a murine-infection model. Based on protection recently reported for the B. parapertussis O antigen in aqueous solution, we assessed here whether the B. parapertussis O-antigen-containing lipopolysaccharide (BppLPS-O⁺) embedded in the membranes, as present in B. parapertussis-derived OMVs (OMVs(Bpp-LPS-O⁺)), was the component responsible for that previously observed protection by OMVs. By performing a comparative study with OMVs from a human strain with undetectable O antigen (OMVs(Bpp-LPS-O^-)), we demonstrated that the OMVs(Bpp-LPS-O⁺), but not the OMVs(Bpp-LPS-O^-), protected mice against sublethal B. parapertussis infections. Indeed, the B. parapertussis loads were significantly reduced in the lungs of OMVs(Bpp-LPS-O⁺) -vaccinated animals, with the CFUs recovered being decreased by 4 log units below those detected in the non-immunized animals or in the animals treated with the OMVs(Bpp-LPS-O^-), (p < 0.001). We detected that the OMVs(Bpp-LPS-O⁺) induced IgG antibodies against B. parapertussis whole-cell lysates, which immunocomponents recognized, among others, the O antigen and accordingly conferred protection against B. parapertussis infection, as observed in in-vivo-passive-transfer experiments. Of interest was that the OMVs(Bpp-LPS-O⁺) -generated sera had opsonophagocytic and bactericidal capabilities that were not detected with the OMVs(Bpp-LPS-O^-)-induced sera, suggesting that those activities were involved in the clearance of B. parapertussis. Though stimulation of cultured spleen cells from immunized mice with formulations containing the O antigen resulted in gamma interferon (IFN-γ) and interleukin-17 production, spleen cells from OMVs(Bpp-LPS-O⁺) -immunized mice did not significantly contribute to the observed protection against B. parapertussis infection. The protective capability of the B. parapertussis O antigen was also detected in formulations containing both the OMVs derived from B. pertussis and purified BppLPS-O⁺. This combined formulation protected mice against B. pertussis along with B. parapertussis.

A recombinant iron transport protein from Bordetella pertussis confers protection against Bordetella parapertussis

Whooping cough, which is caused by Bordetella pertussis and B. parapertussis, is a reemerging disease. New protective antigens are needed to improve the efficacy of current vaccines against both species. Using proteomic tools, it was here found that B. parapertussis expresses a homolog of AfuA, a previously reported new vaccine candidate against B. pertussis. It was found that this homolog, named AfuA_Bpp , is expressed during B. parapertussis infection, exposed on the surface of the bacteria and recognized by specific antibodies induced by the recombinant AfuA cloned from B. pertussis (rAfuA). Importantly, the presence of the O-antigen, a molecule that has been found to shield surface antigens on B. parapertussis, showed no influence on antibody recognition of AfuA_Bpp on the bacterial surface. The present study further showed that antibodies induced by immunization with the recombinant protein were able to opsonize B. parapertussis and promote bacterial uptake by neutrophils. Finally, it was shown that this antigen confers protection against B. parapertussis infection in a mouse model. Altogether, these results indicate that AfuA is a good vaccine candidate for acellular vaccines protective against both causative agents of whooping cough.

Development of vaccines against pertussis caused by Bordetella holmesii using a mouse intranasal challenge model

Bordetella holmesii is recognized as the third causative agent of pertussis (whooping cough) in addition to Bordetella pertussis and Bordetella parapertussis. Pertussis caused by B. holmesii is not rare around the world. However, to date, there is no effective vaccine against B. holmesii. We examined the protective potency of pertussis vaccines available in Japan and vaccines prepared from B. holmesii. A murine model of respiratory infection was exploited to evaluate protective potency. No Japanese commercial pertussis vaccines were effective against B. holmesii. In contrast, a wBH vaccine and an aBH vaccine prepared from B. holmesii were both protective. Passive immunization with sera from mice immunized with aBH vaccine established protection against B. holmesii, indicating that B. holmesii-specific serum antibodies might play an important role in protection. Immuno-proteomic analysis with sera from mice immunized with aBH vaccine revealed that the sera recognized a BipA-like protein of B. holmesii. An aBH vaccine prepared from a BipA-like protein-deficient mutant strain did not have a protective effect against B. holmesii. Taken together, our results suggest that the BipA-like protein plays an important role in the protective efficacy of aBH vaccine.

Greater efficacy of the ECMS-oil adjuvant over other formulations on immune responses against Bordetella bronchiseptica in rabbits and the underlying mechanism

In this study, the adjuvant effects of the extract of Cochinchina momordica seed ECMS+oil, oil alone, ECMS alone, conventional alum adjuvant on inactivated Bordetella bronchiseptica (Bb) vaccine or control using antigen alone without adjuvant were evaluated along with the underlying mechanism. The results in experiment A demonstrated that antibody levels in Bb whole cell protein in the ECMS800μg+oil group were significantly higher than in the other adjuvant groups (p<0.05) on day 21. The agglutination antibody titer was also higher than the other groups (p<0.05) on day 37. The ECMS800μg+oil group improved cellular immune responses compared to other adjuvant groups, including control using antigen alone without adjuvant and the PBS group (p<0.05). After Bb challenge, the ECMS800μg+oil group showed the highest protection rate, which was significantly higher than ECMS alone or control using antigen alone without adjuvant and the PBS group (p<0.05 and p<0.01). IgA cells in the ECMS800μg+oil group differed significantly from the IgA cells of other groups in the lungs (p<0.01). The results of cell recruitment showed that the number of lymphocytes in the ECMS400μg+oil were higher than the number of cells for other groups except the ECMS(100μg/800μg)+oil groups (p<0.05). Intermediate cells in the ECMS(100μg/400μg)+oil groups were higher than the number of cells for other groups, including the control using antigen alone group (p<0.05). Neutrophils in the ECMS(100μg/400μg/800μg)+oil groups were significantly higher than the ECMS 800μg and control using antigen alone groups (p<0.05). White blood cells in the ECMS100μg+oil group were significantly higher than the oil, ECMS800μg and control using antigen alone groups (p<0.05). IL-2 expression in the ECMS800μg+oil group was significantly higher than other groups, except for the ECMS400μg+oil group (p<0.05). IL-4 expression in the ECMS800μg+oil group was significantly higher than other groups (p<0.05). GATA3 in the ECMS800μg+oil groups was significantly higher than the oil, ECMS800μg and control using antigen alone group (p<0.05). ECMS-oil adjuvant mixture could most effectively protect B. bronchiseptica immunized rabbits and, therefore, could be an alternative way of improving B. bronchiseptica vaccination in rabbits.

Outer membrane vesicles derived from Bordetella parapertussis as an acellular vaccine against Bordetella parapertussis and Bordetella pertussis infection

Bordetella parapertussis, a close related species of B. pertussis, can also cause the disease named pertussis or whooping cough. The number of cases caused by this related pathogen has risen sustained in the last years. The widely used cellular (wP) or acellular (aP) pertussis vaccines have little or no efficacy against B. parapertussis. In an effort to devise an effective acellular vaccine against B. parapertussis infection, outer membrane vesicles (OMVs) were obtained from B. parapertussis. Proteomic analysis of the resulting OMVs, designated OMVsBpp, evidenced the presence of several surface immunogens including pertactin. The characterized OMVsBpp were used in murine B. parapertussis intranasal challenge model to examine their protective capacity when administered by systemic route. Immunized BALB/c mice were challenged with sublethal doses of B. parapertussis. Significant differences between immunized animals and the negative control group were observed (p<0.001). OMVsBpp protected against B. parapertussis infection, whereas current commercial aP vaccine showed little protection against such pathogen. More interestingly, protection induced by OMVsBpp against B. pertussis was comparable to our previously designed vaccine consisting in OMVs derived from B. pertussis (OMVsBp). For these experiments we used as a positive control the current commercial aP vaccine in high dose. As expected aP offered protection against B. pertussis in mice. Altogether the results presented here showed that the OMVs from B. parapertussis are an attractive vaccine candidate to protect against whooping cough induced by B. parapertussis but also by B. pertussis.

Enhancement of Bordetella parapertussis infection by Bordetella pertussis in mixed infection of the respiratory tract

The epidemiological and pathogenic relationship between Bordetella pertussis and Bordetella parapertussis, the two causes of whooping cough (pertussis), is unclear. We hypothesized that B. pertussis, due to its immunosuppressive activities, might enhance B. parapertussis infection when the two species were present in a coinfection of the respiratory tract. The dynamics of this relationship were examined using the mouse intranasal inoculation model. Infection of the mouse respiratory tract by B. parapertussis was not only enhanced by the presence of B. pertussis, but B. parapertussis significantly outcompeted B. pertussis in this model. Staggered inoculation of the two organisms revealed that the advantage for B. parapertussis is established at an early stage of infection. Coadministration of PT enhanced B. parapertussis single infection, but had no effect on mixed infections. Mixed infection with a PT-deficient B. pertussis strain did not enhance B. parapertussis infection. Interestingly, the depletion of airway macrophages reversed the competitive relationship between these two organisms, but the depletion of neutrophils had no effect on mixed infection or B. parapertussis infection. We conclude that B. pertussis, through the action of PT, can enhance a B. parapertussis infection, possibly by an inhibitory effect on innate immunity.