Cystic Fibrosis Mice Develop Spontaneous Chronic Bordetella Airway Infections

Genomic characterization and drug resistance of Bordetella pseudohinzii first isolated from wild niviventer

BACKGROUND

Niviventer, a rodent species widely distributed in Asian forests, serves as a significant reservoir for pathogens. Bordetella pseudohinzii(B. pseudohinzii), a recently identified Bordetella species with unclear pathogenic potential, poses challenges in species identification and understanding of its pathogenicity, its biological traits and antibiotic resistance are not well understood.

METHODS

B. pseudohinzii(strains 21F10, 22F12, and 27F25) were isolated from lung tissue of wild niviventer rodents in Guizhou, China. Initial identification was performed using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) and 16 S rRNA gene sequencing. A phylogenetic tree based on the 16 S rRNA gene sequences was constructed using the neighbor-joining method implemented in MEGA 11. Whole-genome sequencing (WGS) was conducted on all three strains, and strain 21F10 underwent hybrid assembly of second- and third-generation sequencing to achieve high-quality sequences. Average Nucleotide Identity (ANI) and digital DNA-DNA hybridization (dDDH) were used as gold standards for strain identification, with thresholds set at 95% and 70%, respectively. Gene annotation was performed using nine databases, including KEGG, VFDB, CARD, PHI, COG, and NR. Antimicrobial susceptibility testing was carried out using the drug-sensitive plate method.

RESULTS

Initial MALDI-TOF MS identification misclassified the strains as B. avium and B. hinzii. However, PCR amplification of the 16 S rRNA gene (primers 27 F and 1492R) revealed that the strains were identified as B. hinzii (identity > 99%). Further analysis of the 16 S rRNA gene sequences obtained from WGS showed identities greater than 99% with both B. pseudohinzii and B. hinzii. Phylogenetic analysis of the 16 S rRNA gene sequences showed that the strains were closely related to B. hinzii, followed by B. pseudohinzii. Ultimately, the ANI values of all three strains with B. pseudohinzii were greater than 95%, and dDDH values exceeded 70%, confirming the strains as B. pseudohinzii. Strain 21F10 exhibited notable findings in terms of virulence factors and antibiotic resistance genes. Antimicrobial susceptibility testing revealed significant resistance to several cephalosporins (cefoxitin, cefuroxime, cefotaxime, cefazolin, and ceftiofur). The 16 S rRNA and WGS of strain 21F10 have been deposited in GenBank and Genome Sequence Archive (GSA)under accession numbers PQ881859 and CRA022358, respectively.

CONCLUSION

The first isolation of B. pseudohinzii from the lung tissue of wild niviventer was reported, and the limitations of traditional methods for identifying B. pseudohinzii were demonstrated. We highlight the superiority of WGS for accurate species identification. The findings reveal a complex pathogenic profile and notable antibiotic resistance, providing important insights for the future prevention and treatment of B. pseudohinzii infections in humans, as well as underscoring the need for monitoring B. pseudohinzii in rodent populations.

Human Mesenchymal Stem Cell (hMSC) Donor Potency Selection for the "First in Cystic Fibrosis" Phase I Clinical Trial (CEASE-CF)

Human Mesenchymal Stem Cell (hMSC) immunotherapy has been shown to provide both anti-inflammatory and anti-microbial effectiveness in a variety of diseases. The clinical potency of hMSCs is based upon an initial direct hMSC effect on the pro-inflammatory and anti-microbial pathophysiology as well as sustained potency through orchestrating the host immunity to optimize the resolution of infection and tissue damage. Cystic fibrosis (CF) patients suffer from a lung disease characterized by excessive inflammation and chronic infection as well as a variety of other systemic anomalies associated with the consequences of abnormal cystic fibrosis transmembrane conductance regulator (CFTR) function. The application of hMSC immunotherapy to the CF clinical armamentarium is important even in the era of modulators when patients with an established disease still need anti-inflammatory and anti-microbial therapies. Additionally, people with CF mutations not addressed by current modulator resources need anti-inflammation and anti-infection management. Furthermore, hMSCs possess dynamic therapeutic properties, but the potency of their products is highly variable with respect to their anti-inflammatory and anti-microbial effects. Due to the variability of hMSC products, we utilized standardized in vitro and in vivo models to select hMSC donor preparations with the greatest potential for clinical efficacy. The models that were used recapitulate many of the pathophysiologic outcomes associated with CF. We applied this strategy in pursuit of identifying the optimal donor to utilize for the "First in CF" Phase I clinical trial of hMSCs as an immunotherapy and anti-microbial therapy for people with cystic fibrosis. The hMSCs screened in this study demonstrated significant diversity in antimicrobial and anti-inflammatory function using models which mimic some aspects of CF infection and inflammation. However, the variability in activity between in vitro potency and in vivo effectiveness continues to be refined. Future studies require and in-depth pursuit of hMSC molecular signatures that ultimately predict the capacity of hMSCs to function in the clinical setting.

Conquering the host: Bordetella spp. and Pseudomonas aeruginosa molecular regulators in lung infection

When bacteria sense cues from the host environment, stress responses are activated. Two component systems, sigma factors, small RNAs, ppGpp stringent response, and chaperones start coordinate the expression of virulence factors or immunomodulators to allow bacteria to respond. Although, some of these are well studied, such as the two-component systems, the contribution of other regulators, such as sigma factors or ppGpp, is increasingly gaining attention. Pseudomonas aeruginosa is the gold standard pathogen for studying the molecular mechanisms to sense and respond to environmental cues. Bordetella spp., on the other hand, is a microbial model for studying host-pathogen interactions at the molecular level. These two pathogens have the ability to colonize the lungs of patients with chronic diseases, suggesting that they have the potential to share a niche and interact. However, the molecular networks that facilitate adaptation of Bordetella spp. to cues are unclear. Here, we offer a side-by-side comparison of what is known about these diverse molecular mechanisms that bacteria utilize to counteract host immune responses, while highlighting the relatively unexplored interactions between them.

Serum inflammatory profiles in cystic fibrosis mice with and without Bordetella pseudohinzii infection

Cystic fibrosis (CF) is an autosomal recessive disease caused by dysfunctional cystic fibrosis transmembrane conductance regulator (CFTR) protein, and is marked by an accumulation of mucus in affected airways resulting in persistent infection and chronic inflammation. Quantitative differences in inflammatory markers have been observed in CF patient serum, tracheal cells, and bronchoalveolar lavage fluid, in the absence of detectable infection, implying that absent CFTR function alone may result in dysregulated immune responses. To examine the relationship between absent CFTR and systemic inflammation, 22 analytes were measured in CF mice (F508del/F508del) sera using the MSD multiplex platform. Pro-inflammatory cytokines IL-2, TNF-α, IL-17α, IFN-γ, IL-1β, and MIP-3α are significantly elevated in infection-naïve CF mice (p < 0.050). Anti-inflammatory cytokines IL-10 and IL-4 are also significantly increased (p = 0.00003, p = 0.004). Additionally, six general markers of inflammation are significantly different from non-CF controls (p < 0.050). To elucidate the effects of chronic infection on the CF inflammatory profile, we examined CF mice exposed to spontaneous Bordetella pseudohinzii infections. There are no statistical differences in nearly all inflammatory markers when compared to their infection-naïve CF counterparts, except in the Th2-derived IL-4 and IL-5 which demonstrate significant decreases following exposure (p = 0.046, p = 0.045). Lastly, following acute infection, CF mice demonstrate elevations in nearly all inflammatory markers, but exhibit a shortened return to uninfected levels over time, and suppression of Th1-derived IL-2 and IL-5 (p = 0.043, p = 0.011). These results imply that CF mice have a persistent inflammatory profile often indistinguishable from chronic infection, and a dysregulated humoral response during and following active infection.

AGTR2 absence or antagonism prevents cystic fibrosis pulmonary manifestations

BACKGROUND

Pulmonary disease remains the primary cause of morbidity and mortality for individuals with cystic fibrosis (CF). Variants at a locus on the X-chromosome containing the type 2 angiotensin II receptor gene (AGTR2) were identified by a large GWAS as significantly associating with lung function in CF patients. We hypothesized that manipulating the angiotensin-signaling pathway may yield clinical benefit in CF.

METHODS

Genetic subset analysis was conducted on a local CF cohort to extend the GWAS findings. Next, we evaluated pulmonary function in CF mice with a deleted AGTR2 gene, and in those who were given subcutaneous injections of PD123,319, a selective AGTR2 antagonist for 12 weeks beginning at weaning.

RESULTS

The genetic subset analysis replicated the initial GWAS identified association, and confirmed the association of this locus with additional lung function parameters. Studies in genetically modified mice established that absence of the AGTR2 gene normalized pulmonary function indices in two independent CF mouse models. Further, we determined that pharmacologic antagonism of AGTR2 improved overall pulmonary function in CF mice to near wild-type levels.

CONCLUSIONS

These results identify that reduced AGTR2 signaling is beneficial to CF lung function, and suggest the potential of manipulating the angiotensin-signaling pathway for treatment and/or prevention of CF pulmonary disease. Importantly, the beneficial effects were not CF gene mutation dependent, and were able to be reproduced with pharmacologic antagonism. As there are clinically approved drugs available to target the renin-angiotensin signaling system, these findings may be quickly translated to human clinical trials.

Airway disease phenotypes in animal models of cystic fibrosis

In humans, cystic fibrosis (CF) lung disease is characterised by chronic infection, inflammation, airway remodelling, and mucus obstruction. A lack of pulmonary manifestations in CF mouse models has hindered investigations of airway disease pathogenesis, as well as the development and testing of potential therapeutics. However, recently generated CF animal models including rat, ferret and pig models demonstrate a range of well characterised lung disease phenotypes with varying degrees of severity. This review discusses the airway phenotypes of currently available CF animal models and presents potential applications of each model in airway-related CF research.