Evaluation of vaccines for atrophic rhinitis--a comparison of three challenge models

Tissue specific stem cell therapy for airway regeneration

Secondary atrophic rhinitis (AR), a consequence of mucosal damage during nasal surgeries, significantly impairs patient quality of life. The lack of effective, lasting treatments underscores the need for alternative therapeutic strategies. A major impediment in advancing research is the scarcity of studies focused on secondary AR. Our study addresses this gap by developing an animal model that closely mirrors the histopathological changes observed in patients with secondary AR. These changes include squamous metaplasia, goblet cell hyperplasia, submucosal fibrosis, and glandular atrophy. Upon administering human nasal turbinate stem cells embedded in collagen type I hydrogel in these models, we observed ciliary regeneration. This finding suggests the potential therapeutic benefit of this approach. Our animal models not only emulate the clinical manifestations of secondary AR but also serve as valuable tools for evaluating the efficacy of cell-based biotechnological interventions.

Integrated pharmacokinetic-Pharmacodynamic (PK/PD) model to evaluate the in vivo antimicrobial activity of Marbofloxacin against Pasteurella multocida in piglets

Background

Marbofloxacin is a veterinary fluoroquinolone with high activity against Pasteurella multocida. We evaluated it’s in vivo activity against P. multocida based on in vivo time-kill data in swine using a tissue-cage model. A series of dosages ranging from 0.15 to 2.5 mg/kg were administered intramuscularly after challenge with P. multocida type B, serotype 2.

Results

The ratio of the 24 h area under the concentration-time curve divided by the minimum inhibitory concentration (AUC₂₄TCF/MIC) was the best PK/PD index correlated with the in vivo antibacterial effectiveness of marbofloxacin (R2 = 0.9279). The AUC₂₄TCF/MIC necessary to achieve a 1-log₁₀ CFU/ml reduction and a 3-log₁₀ CFU/ml (90% of the maximum response) reduction as calculated by an inhibitory sigmoid E_max model were 13.48 h and 57.70 h, respectively.

Conclusions

Marbofloxacin is adequate for the treatment of swine infected with P. multocida. The tissue-cage model played a significant role in achieving these PK/PD results.

Feed exposure to FB1 can aggravate pneumonic damages in pigs provoked by P. multocida

The possible interaction between Pasteurella multocida and the mycotoxin fumonisin B1 (FB1), recognised as one of the most often food/feed contaminant, was studied with the aim to evaluate whether and how FB1 can influence and/or complicate the development and severity of various pathological damages provoked by Pasteurella multocida in some internal organs of pigs. Heavier lung pathology was seen in pigs experimentally infected with Pasteurella multocida, when the same were exposed to 20ppm dietary levels of fumonisin B1 (FB1) as was assessed by gross pathology, pathomorphological examinations, clinical biochemistry and some immunological investigations. The most typical damages in FB1 treated pigs were the strong oedema in the lung and the slight oedema in the other internal organs and mild degenerative changes in the kidneys, whereas the typical pathomorphological findings in pigs infected with Pasteurella multocida was broncho-interstitial pneumonia. FB1 was found to aggravate pneumonic changes provoked by P. multocida in the cranial lobes of the lung and to complicate pneumonic damages with interstitial oedema in the lung. No macroscopic damages were observed in the pigs infected only with Pasteurella multocida. It can be concluded that the feed intake of FB1 in pigs may complicate or exacerbate the course of P. multocida serotype A infection.

A comparative pathological finding in pigs exposed to fumonisin B1 and/or Mycoplasma hyopneumoniae

A more complicated pathology was observed in female pigs infected with Mycoplasma hyopneumoniae, when the same were exposed to 20 ppm dietary levels of fumonisin B1 (FB1) starting 14 days before infection for a period of 42 days as was assessed by gross pathology and pathomorphological examinations or computed tomography, and also manifested by the strong deterioration of the pneumonic process in two pigs and the subsequent euthanizing of one pig. Typical damages in FB1-fed pigs were a strong oedema in the lung and slight oedema in the other internal organs and mild degenerative changes in the kidneys, whereas the typical pathomorphological changes in M. hyopneumoniae-infected pigs corresponded to the morphologic pattern of a catarrhal bronchointerstitial pneumonia more pronounced in the cranial and middle lobes or in the cranial third of the caudal lobe of the lung. The pigs treated by both pathogens (toxic and infectious) revealed strong oedematous changes in the interstitium of lung in addition to deteriorated and extended bronchointerstitial pneumonic process.

Regeneration of toxigenic Pasteurella multocida induced severe turbinate atrophy in pigs detected by computed tomography

Background

Atrophic rhinitis is a widely prevalent infectious disease of swine caused by Bordetella bronchiseptica and Pasteurella multocida. The course of the disease is considered to be different depending on the principal aetiological agents distinguishing B. bronchiseptica induced non-progressive and toxigenic P. multocida produced progressive forms. In order to compare the pathological events of the two forms of the disease, the development of nasal lesions has longitudinally been studied in pigs infected by either B. bronchiseptica alone or B. bronchiseptica and toxigenic P. multocida together using computed tomography to visualise the nasal structures.

Results

B. bronchiseptica infection alone caused moderately severe nasal turbinate atrophy and these lesions completely regenerated by the time of slaughter. Unexpectedly, complete regeneration of the bony structures of the nasal cavity was also observed in pigs infected by B. bronchiseptica and toxigenic P. multocida together in spite of seeing severe turbinate atrophy in most of the infected animals around the age of six weeks.

Conclusions

B. bronchiseptica mono-infection has been confirmed to cause only mild to moderate and transient lesions, at least in high health status pigs. Even severe turbinate atrophy induced by B. bronchiseptica and toxigenic P. multocida combined infection is able to be reorganised to their normal anatomical structure. Computed tomography has further been verified to be a useful tool to examine the pathological events of atrophic rhinitis in a longitudinal manner.

Pasteurella multocida: from zoonosis to cellular microbiology

In a world where most emerging and reemerging infectious diseases are zoonotic in nature and our contacts with both domestic and wild animals abound, there is growing awareness of the potential for human acquisition of animal diseases. Like other Pasteurellaceae, Pasteurella species are highly prevalent among animal populations, where they are often found as part of the normal microbiota of the oral, nasopharyngeal, and upper respiratory tracts. Many Pasteurella species are opportunistic pathogens that can cause endemic disease and are associated increasingly with epizootic outbreaks. Zoonotic transmission to humans usually occurs through animal bites or contact with nasal secretions, with P. multocida being the most prevalent isolate observed in human infections. Here we review recent comparative genomics and molecular pathogenesis studies that have advanced our understanding of the multiple virulence mechanisms employed by Pasteurella species to establish acute and chronic infections. We also summarize efforts being explored to enhance our ability to rapidly and accurately identify and distinguish among clinical isolates and to control pasteurellosis by improved development of new vaccines and treatment regimens.

Protective immunity conferred by the C-terminal fragment of recombinant Pasteurella multocida toxin

Pasteurella multocida serogroup D, producing P. multocida toxin (PMT), is a causative pathogen of progressive atrophic rhinitis (PAR) in swine. To evaluate the protective immunity and vaccination efficacy of the truncated form of PMT, a C-terminal form of recombinant PMT (designated PMT2.3; amino acid residues 505 to 1285 of PMT) was expressed in an Escherichia coli expression system, and the humoral and cellular immune responses to PMT2.3 were investigated. PMT2.3 vaccination in mice led to high levels of the anti-PMT antibody with a high neutralizing antibody titer. PMT2.3 also induced a cellular immune response to PMT, as demonstrated by the lymphocyte proliferation assay. Furthermore, strong protection against a homologous challenge with P. multocida was also observed in mice vaccinated with PMT2.3. In PMT2.3 vaccination in swine, high levels of serum antibody titers were observed in offspring from sows vaccinated with PMT2.3. Offspring from sows vaccinated with PMT2.3 or toxoid showed a good growth performance as depicted by mean body weight at the time of sacrifice, as well as in average daily gain in the postweaning period. Low levels of pathological lesions in turbinate atrophy and pneumonia were also observed in these offspring. Therefore, we consider PMT2.3--in the truncated and nontoxic recombinant PMT form--to be an attractive candidate for a subunit vaccine against PAR induced by P. multocida infection.

Screening of 71 P. multocida proteins for protective efficacy in a fowl cholera infection model and characterization of the protective antigen PlpE

Background

There is a strong need for a recombinant subunit vaccine against fowl cholera. We used a reverse vaccinology approach to identify putative secreted or cell surface associated P. multocida proteins that may represent potential vaccine candidate antigens.

Principal Findings

A high-throughput cloning and expression protocol was used to express and purify 71 recombinant proteins for vaccine trials. Of the 71 proteins tested, only one, PlpE in denatured insoluble form, protected chickens against fowl cholera challenge. PlpE also elicited comparable levels of protection in mice. PlpE was localized by immunofluorescence to the bacterial cell surface, consistent with its ability to elicit a protective immune response. To explore the role of PlpE during infection and immunity, a plpE mutant was generated. The plpE mutant strain retained full virulence for mice.

Conclusion

These studies show that PlpE is a surface exposed protein and was the only protein of 71 tested that was able to elicit a protective immune response. However, PlpE is not an essential virulence factor. This is the first report of a denatured recombinant protein stimulating protection against fowl cholera.

Atrophic rhinitis vaccine composition triggers different serological profiles that do not correlate with protection

Atrophic rhinitis (AR) is a widespread and economically important disease of swine caused by Bordetella bronchiseptica and Pasteurella multocida. It can be controlled by vaccination. This study investigates the effect of altering the composition (adjuvants and/or addition of formalin-inactivated P. multocida toxin, fPMT) of conventional vaccines on the serological profile and on protection against AR in swine. A significantly higher B. bronchiseptica specific antibody titre was detected for vaccines with novel immunostimulants, the best being Montanide IMS 1313 (1:630 compared to 1:274 obtained with alum). The highest B. bronchiseptica antibody titre was demonstrated for a combination of B. bronchiseptica--fPMT, while PMT antibody titre was highest for monovalent fPMT (both adjuvanted with IMS 1313). The AR-specific antibodies were transmitted from dams to their offspring in similar titres and with the same hierarchy of effectiveness. After a B. bronchiseptica--P. multocida bacterial challenge, piglets from dams vaccinated with fPMT combined with B. bronchiseptica or B. bronchiseptica--P. multocida bacterins showed the lowest nasal lesions scores (4.5 and 3.2, respectively, out of a possible maximum score of 18). These combinations, both of which were adjuvanted with IMS 1313, gave the best protection against experimentally induced AR. Our results show that the adjuvant and the antigen composition of the vaccine strongly affect seroconversion, and that the AR-specific antibody titre does not necessarily correlate with the degree of protection.

BopC is a novel type III effector secreted by Bordetella bronchiseptica and has a critical role in type III-dependent necrotic cell death

In Bordetella bronchiseptica, the functional type III secretion system (TTSS) is required for the induction of necrotic cell death in infected mammalian cells. To identify the factor(s) involved in necrotic cell death, type III-secreted proteins from B. bronchiseptica were analyzed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and electrospray ionization tandem mass spectrometry. We identified a 69-kDa secreted protein designated BopC. The gene encoding BopC is located outside of the TTSS locus and is also highly conserved in both Bordetella parapertussis and Bordetella pertussis. The results of a lactate dehydrogenase release assay and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling assay demonstrated that BopC is required for necrotic cell death. It has been reported that tyrosine-phosphorylated proteins (PY) of host cells are dephosphorylated during B. bronchiseptica infection in a TTSS-dependent manner. We found that BopC is also involved in PY dephosphorylation in infected host cells. It appears that the necrotic cell death triggered by BopC occurs prior to the PY reduction in host cells, because Bordetella-induced cell death was not affected even in the presence of a dephosphorylation inhibitor. Furthermore, a translocation assay showed that the signal sequence for both secretion into culture supernatant and translocation into the host cell is located in 48 amino acid residues of the BopC N terminus. This report reveals for the first time that a novel type III effector, BopC, is required for the induction of necrotic cell death during Bordetella infection.

Immunogenicity and efficacy of three recombinant subunit Pasteurella multocida toxin vaccines against progressive atrophic rhinitis in pigs

Three short fragments of recombinant subunit Pasteurella multocida toxin (rsPMT) were constructed for evaluation as candidate vaccines against progressive atrophic rhinitis (PAR) of swine. PMT-specific antibody secreting cells and evidence of cellular immunity were detected in rsPMT-immunized pigs following authentic PMT challenge or homologous antigen booster. Piglets immunized with rsPMT fragments containing either the N-terminal or the C-terminal portions of PMT developed high titers of neutralizing antibodies. Pregnant sows immunized with rsPMT had higher levels of maternal antibodies in their colostrum than did those immunized with a conventional PAR-toxoid vaccine. Offspring from rsPMT vaccinated sows had better survival after challenge with a five-fold lethal dose of authentic PMT and had better growth performance after challenge with a sublethal dose of toxin. Our findings indicate these non-toxic rsPMT proteins are attractive candidates for development of a subunit vaccine against PAR in pigs.

Association of growth performance with atrophic rhinitis and pneumonia detected at slaughter in a conventional pig herd in Hungary

The influence of atrophic rhinitis (AR) and pneumonia on growth performance was assessed in a conventional farrow-to-finish pig farm affected by both diseases. All tested pigs (n = 138) were individually weighed at birth, at weaning, at moving to the growing/finishing unit, and at slaughtering. The extent (grade) of turbinate atrophy and lung consolidation attributable to pneumonia was determined in each pig at slaughter. A negative correlation was found between birth weight and the prevalence of nasal lesions at slaughter, suggesting that pigs born with smaller weight may be more susceptible to AR. The growth performance of the pigs also showed a negative correlation with the degree of turbinate atrophy. In the nursery period, the average daily gain (ADG) of pigs with moderate/severe turbinate atrophy was 13.3% lower than that of animals with healthy snouts. In the finishing period, pigs with mild AR lesions had an ADG reduction of 6.2%, while pigs with severe AR lesions had a significant, 9.4% reduction in ADG as compared to the AR-free pigs. The extent of weight gain reduction over the whole life cycle was very similar (approximately 6%) in the pigs having either AR or pneumonia alone. In those pigs where both respiratory diseases were present, their effects seemed to be added up (11.5%); however, nasal lesion scores and percentage of lung consolidation did not show statistically apparent interactive effects on growth performance.

Molecular pathogenesis, epidemiology, and clinical manifestations of respiratory infections due to Bordetella pertussis and other Bordetella subspecies

Bordetella respiratory infections are common in people (B. pertussis) and in animals (B. bronchiseptica). During the last two decades, much has been learned about the virulence determinants, pathogenesis, and immunity of Bordetella. Clinically, the full spectrum of disease due to B. pertussis infection is now understood, and infections in adolescents and adults are recognized as the reservoir for cyclic outbreaks of disease. DTaP vaccines, which are less reactogenic than DTP vaccines, are now in general use in many developed countries, and it is expected that the expansion of their use to adolescents and adults will have a significant impact on reducing pertussis and perhaps decrease the circulation of B. pertussis. Future studies should seek to determine the cause of the unique cough which is associated with Bordetella respiratory infections. It is also hoped that data gathered from molecular Bordetella research will lead to a new generation of DTaP vaccines which provide greater efficacy than is provided by today's vaccines.

Developing animal models for polymicrobial diseases

Although polymicrobial diseases are not a new concept for microbiologists, they are experiencing a resurgence of interest owing to the development of suitable animal models and new molecular techniques that allow these diseases to be studied effectively. This broad review provides an excellent introduction to this fascinating topic.

Examples are included of each type of polymicrobial disease and the animal models that are used to study these diseases are discussed. In many instances, schematics for the animal model are presented.

Viral co-infections including bovine viral diarrhoeal viruses, porcine reproductive and respiratory syndrome, mixed hepatitis virus infections and HIV co-infection with hepatitis virus are discussed, together with attempts to model these diseases in animals.

Viral and bacterial co-infections are reviewed with a special focus on otitis media and the rodent models that have been used to probe this important childhood illness.

Of the polybacterial diseases, periodontitis is one of the best understood and a clinically relevant rodent model is now available. This model, and the role of biofilm formation in periodontitis are examined.

Fungal infections of humans are often referred to as 'opportunistic' but in fact these infections are often fungal co-infections with viruses such as HIV and fungal mixed co-infections. The roles of these infections in disease and the rodent models used to study them are discussed.

Parasite co-infections are thought to have a role in the severity of malaria and the severity of Lyme arthritis. These diseases and attempts to model them are evaluated.

Finally, co-infections that are associated with virus-induced immunosuppression are discussed, together with their animal models.

Polymicrobial diseases involve two or more microorganisms that act synergistically, or in succession, to mediate complex disease processes. Although polymicrobial diseases in animals and humans can be caused by similar organisms, these diseases are often also caused by organisms from different kingdoms, genera, species, strains, substrains and even by phenotypic variants of a single species. Animal models are often required to understand the mechanisms of pathogenesis, and to develop therapies and prevention regimes. However, reproducing polymicrobial diseases of humans in animal hosts presents significant challenges.