Vaccine-mediated protection against Campylobacter-associated enteric disease

Identification of novel small molecule inhibitors of twin arginine translocation (Tat) pathway and their effect on the control of Campylobacter jejuni in chickens

Introduction

Control of Campylobacter from farm to fork is challenging due to the frequent emergence of antimicrobial-resistant isolates. Furthermore, poultry production systems are known reservoirs of Campylobacter. The twin-arginine translocation (Tat) pathway is a crucial bacterial secretion system that allows Campylobacter to colonize the host intestinal tract by using formate as the main source of energy. However, Tat pathway is also a major contributing factor for resistance to copper sulfate (CuSO4).

Methods

Since mammals and chickens do not have proteins or receptors that are homologous to bacterial Tat proteins, identification of small molecule (SM) inhibitors targeting the Tat system would allow the development of safe and effective control methods to mitigate Campylobacter in infected or colonized hosts in both pre-harvest and post-harvest. In this study, we screened 11 commercial libraries (n = 50,917 SM) for increased susceptibility to CuSO4 (1 mM) in C. jejuni 81-176, a human isolate which is widely studied.

Results

Furthermore, we evaluated 177 SM hits (2.5 μg/mL and above) that increased the susceptibility to CuSO4 for the inhibition of formate dehydrogenase (Fdh) activity, a Tat-dependent substrate. Eight Tat-dependent inhibitors (T1-T8) were selected for further studies. These selected eight Tat inhibitors cleared all tested Campylobacter strains (n = 12) at >10 ng/mL in the presence of 0.5 mM CuSO4in vitro. These selected SMs were non-toxic to colon epithelial (Caco-2) cells when treated with 50 μg/mL for 24 h and completely cleared intracellular C. jejuni cells when treated with 0.63 μg/mL of SM for 24 h in the presence of 0.5 mM of CuSO4. Furthermore, 3 and 5-week-old chicks treated with SM candidates for 5 days had significantly decreased cecal colonization (up to 1.2 log; p < 0.01) with minimal disruption of microbiota. In silico analyses predicted that T7 has better drug-like properties than T2 inhibitor and might target a key amino acid residue (glutamine 165), which is located in the hydrophobic core of TatC protein.

Discussion

Thus, we have identified novel SM inhibitors of the Tat pathway, which represent a potential strategy to control C. jejuni spread on farms.

The impact on primary care of a large waterborne campylobacter outbreak in Norway: a controlled observational study

OBJECTIVE

Document the impact of an outbreak of gastroenteritis on local primary health care services, compared to a control period.

DESIGN

Controlled observational study with data from the outbreak and a control period. Data obtained from electronic medical records (EMR) of general practitioners (GPs) and the out-of-hours (OOH) service. Telephone data from the OOH service's telephone records.

SETTING

Campylobacteriosis outbreak in Askøy municipality, Norway in 2019. Over 2000 individuals were infected.

SUBJECTS

Patients in contact with GPs and the OOH service during the outbreak and a control period.

MAIN OUTCOME MEASURES

Patient contacts with GPs and the OOH service during the outbreak and a control period.

RESULTS

There was a 36% increase in contacts during the outbreak compared to the control period (4798 vs. 3528), with the OOH service handling 78% of outbreak-related contacts. Telephone advice was the dominant method for managing the increase in contacts to primary care, both in OOH services and daytime general practice (OR 3.73 CI: [3.24-4.28]). Children aged 0-4 years had increased use of primary care during the outbreak (OR 1.51 CI: [1.28-1.78]). GPs referred 25% and OOH services referred 75% of 70 hospitalized cases.

CONCLUSION

The OOH service handled most of the patients during the outbreak, with support from daytime general practice. The outbreak caused a shift towards telephone advice as a means of providing care. Young children significantly increased their use of primary care during the outbreak.

Infant diarrheal disease in rhesus macaques impedes microbiome maturation and is linked to uncultured Campylobacter species

Diarrheal diseases remain one of the leading causes of death for children under 5 globally, disproportionately impacting those living in low- and middle-income countries (LMIC). Campylobacter spp., a zoonotic pathogen, is one of the leading causes of food-borne infection in humans. Yet to be cultured Campylobacter spp. contribute to the total burden in diarrheal disease in children living in LMIC thus hampering interventions. We performed microbiome profiling and metagenomic genome assembly on samples collected from over 100 infant rhesus macaques longitudinally and during cases of clinical diarrhea within the first year of life. Acute diarrhea was associated with long-lasting taxonomic and functional shifts of the infant gut microbiome indicative of microbiome immaturity. We constructed 36 Campylobacter metagenomic assembled genomes (MAGs), many of which fell within 4 yet to be cultured species. Finally, we compared the uncultured Campylobacter MAGs assembled from infant macaques with publicly available human metagenomes to show that these uncultured species are also found in human fecal samples from LMIC. These data highlight the importance of unculturable Campylobacter spp. as an important target for reducing disease burden in LMIC children.

Campylobacter vaccination reduces diarrheal disease and infant growth stunting among rhesus macaques

Campylobacter-associated enteric disease is estimated to be responsible for more than 160 million cases of gastroenteritis each year and is linked to growth stunting of infants living under conditions of poor sanitation and hygiene. Here, we examine naturally occurring Campylobacter-associated diarrhea among rhesus macaques as a model to determine if vaccination could reduce severe diarrheal disease and infant growth stunting. Compared to unvaccinated controls, there are no Campylobacter diarrhea-associated deaths observed among vaccinated infant macaques and all-cause diarrhea-associated infant mortality is decreased by 76% (P = 0.03). By 9 months of age, there is a 1.3 cm increase in dorsal length that equaled a significant 1.28 LAZ (Length-for-Age Z score) improvement in linear growth among vaccinated infants compared to their unvaccinated counterparts (P = 0.001). In this work, we show that Campylobacter vaccination not only reduces diarrheal disease but also potentially serves as an effective intervention that improves infant growth trajectories.

Characterisation of N-linked protein glycosylation in the bacterial pathogen Campylobacter hepaticus

Campylobacter hepaticus is an important pathogen which causes Spotty Liver Disease (SLD) in layer chickens. SLD results in an increase in mortality and a significant decrease in egg production and therefore is an important economic concern of the global poultry industry. The human pathogen Campylobacter jejuni encodes an N-linked glycosylation system that plays fundamental roles in host colonization and pathogenicity. While N-linked glycosylation has been extensively studied in C. jejuni and is now known to occur in a range of Campylobacter species, little is known about C. hepaticus glycosylation. In this study glycoproteomic analysis was used to confirm the functionality of the C. hepaticus N-glycosylation system. It was shown that C. hepaticus HV10T modifies > 35 proteins with an N-linked heptasaccharide glycan. C. hepaticus shares highly conserved glycoproteins with C. jejuni that are involved in host colonisation and also possesses unique glycoproteins which may contribute to its ability to survive in challenging host environments. C. hepaticus N-glycosylation may function as an important virulence factor, providing an opportunity to investigate and develop a better understanding the system's role in poultry infection.

Development of a next-generation chikungunya virus vaccine based on the HydroVax platform

Chikungunya virus (CHIKV) is an emerging/re-emerging mosquito-borne pathogen responsible for explosive epidemics of febrile illness characterized by debilitating polyarthralgia and the risk of lethal infection among the most severe cases. Despite the public health risk posed by CHIKV, no vaccine is currently available. Using a site-directed hydrogen peroxide-based inactivation approach, we developed a new CHIKV vaccine, HydroVax-CHIKV. This vaccine technology was compared to other common virus inactivation approaches including β-propiolactone (BPL), formaldehyde, heat, and ultraviolet (UV) irradiation. Heat, UV, and BPL were efficient at inactivating CHIKV-181/25 but caused substantial damage to neutralizing epitopes and failed to induce high-titer neutralizing antibodies in vaccinated mice. HydroVax-CHIKV and formaldehyde-inactivated CHIKV retained intact neutralizing epitopes similar to live virus controls but the HydroVax-CHIKV approach demonstrated a more rapid rate of virus inactivation. HydroVax-CHIKV vaccination induced high neutralizing responses to homologous and heterologous CHIKV clades as well as to other alphaviruses including Mayaro virus, O’nyong’nyong virus, and Una virus. Following heterologous infection with CHIKV-SL15649, HydroVax-CHIKV-immunized mice were protected against viremia, CHIKV-associated arthritic disease, and lethal CHIKV infection by an antibody-dependent mechanism. In contrast, animals vaccinated with Heat- or UV-inactivated virus showed no protection against viremia in addition to demonstrating significantly exacerbated CD4⁺ T cell-mediated footpad swelling after CHIKV infection. Together, these results demonstrate the risks associated with using suboptimal inactivation methods that fail to elicit protective neutralizing antibody responses and show that HydroVax-CHIKV represents a promising new vaccine candidate for prevention of CHIKV-associated disease.

Chikungunya virus (CHIKV) is a mosquito-borne virus that has gained significant attention due to its ability to cause large epidemics and to spread beyond endemic countries through international travelers. Despite substantial efforts over the course of many years, a licensed CHIKV vaccine remains unavailable for protecting at-risk populations. Our research group has established an advanced site-directed oxidation system, termed HydroVax, for the development of new vaccines. Here, we describe a novel CHIKV vaccine that utilizes this peroxide-based vaccine platform and demonstrates greatly improved antiviral immunity compared to other traditional virus inactivation approaches as well as complete protection against viremia, CHIKV-associated arthritic disease and lethal CHIKV infection in robust preclinical mouse models. The HydroVax-CHIKV vaccine not only induced neutralizing antibodies to geographically diverse strains of CHIKV, but also elicited neutralizing antibody responses to other clinically important alphaviruses including, Mayaro, O’nyong’nyong, and Una virus. Together, this indicates that this vaccine not only protects against CHIKV infection but may potentially provide immunity across a broader range of virulent alphaviruses as well.

Development of a Trivalent Construct Omp18/AhpC/FlgH Multi Epitope Peptide Vaccine Against Campylobacter jejuni

Campylobacter jejuni (C. jejuni) is one of the major pathogens contributing to the enteritis in humans. Infection can lead to numerous complications, including but not limited to Guillain-Barre syndrome, reactive arthritis, and Reiter’s syndrome. Over the past two decades, joint efforts have been made toward developing a proper strategy of limiting the transmission of C. jejuni to humans. Nevertheless, except for biosecurity measures, no available vaccine has been developed so far. Judging from the research findings, Omp18, AhpC outer membrane protein, and FlgH flagellin subunits of C. jejuni could be adopted as surface protein antigens of C. jejuni for screening dominant epitope thanks to their strong antigenicity, expression of varying strains, and conservative sequence. In this study, bioinformatics technology was adopted to analyze the T-B antigenic epitopes of Omp18, AhpC, and FlgH in C. jejuni strain NCTC11168. Both ELISA and Western Blot methods were adopted to screen the dominant T-B combined epitope. GGS (GGCGGTAGC) sequence was adopted to connect the dominant T-B combined epitope peptides and to construct the prokaryotic expression system of tandem repeats of antigenic epitope peptides. The mouse infection model was adopted to assess the immunoprotective effect imposed by the trivalent T-B combined with antigen epitope peptide based on Omp18/AhpC/FlgH. In this study, a tandem epitope AhpC-2/Omp18-1/FlgH-1 was developed, which was composed of three epitopes and could effectively enhance the stability and antigenicity of the epitope while preserving its structure. The immunization of BALB/c mice with a tandem epitope could induce protective immunity accompanied by the generation of IgG2a antibody response through the in vitro synthesis of IFN-γ cytokines. Judging from the results of immune protection experiments, the colonization of C. jejuni declined to a significant extent, and it was expected that AhpC-2/Omp18-1/FlgH-1 could be adopted as a candidate antigen for genetic engineering vaccine of C. jejuni MAP.

Reduced infant rhesus macaque growth rates due to environmental enteric dysfunction and association with histopathology in the large intestine

Environmental enteric dysfunction is associated with malnutrition as well as infant growth stunting and has been classically defined by villous blunting, decreased crypt-to-villus ratio, and inflammation in the small intestine. Here, we characterized environmental enteric dysfunction among infant rhesus macaques that are naturally exposed to enteric pathogens commonly linked to human growth stunting. Remarkably, despite villous atrophy and histological abnormalities observed in the small intestine, poor growth trajectories and low serum tryptophan levels were correlated with increased histopathology in the large intestine. This work provides insight into the mechanisms underlying this disease and indicates that the large intestine may be an important target for therapeutic intervention.

Environmental enteric dysfunction (EED), a subclinical disorder of intestinal function, is associated with malnutrition, infant growth stunting and pathologies in the small intestine. Here the authors report that infant rhesus macaques that are naturally exposed to enteric pathogens commonly linked to human growth stunting present with EED and growth faltering that associates with large intestine pathologies.

Bioengineering of LAB vector expressing Haemolysin co-regulated protein (Hcp): a strategic approach to control gut colonization of Campylobacter jejuni in a murine model

Background

Campylobacter jejuni (C. jejuni) is accountable for more than 400 million cases of gastroenteritis each year and is listed as a high-priority gut pathogen by the World Health Organization (WHO). Although the acute infection of C. jejuni (campylobacteriosis) is commonly treated with macrolides and fluoroquinolones, the emergence of antibiotic resistance among C. jejuni warrants the need for an alternative approach to control campylobacteriosis in humans. To this end, vaccines remain a safe, effective, and widely accepted strategy for controlling emerging and re-emerging infectious diseases. In search of a suitable vaccine against campylobacteriosis, recently, we demonstrated the potential of recombinant Haemolysin co-regulated protein (Hcp) of C. jejuni Type VI secretion system (T6SS) in imparting significant immune-protection against cecal colonization of C. jejuni; however, in the avian model. Since clinical features of human campylobacteriosis are more complicated than the avians, we explored the potential of Hcp as a T6SS targeted vaccine in a murine model as a more reliable and reproducible experimental host to study vaccine-induced immune-protection against C. jejuni. Because C. jejuni primarily utilizes the mucosal route for host pathogenesis, we analyzed the immunogenicity of a mucosally deliverable bioengineered Lactic acid bacteria (LAB), Lactococcus lactis (L. lactis), expressing Hcp. Considering the role of Hcp in both structural (membrane-bound) and functional (effector protein) exhibition of C. jejuni T6SS, a head-to-head comparison of two different forms of recombinant LAB vectors (cell wall anchored and secreted form of Hcp) were tested and assessed for the immune phenotypes of each modality in BALB/c mice.

Results

We show that regardless of the Hcp protein localization, mucosal delivery of bioengineered LAB vector expressing Hcp induced high-level production of antigen-specific neutralizing antibody (sIgA) in the gut with the potential to reduce the cecal load of C. jejuni in mice.

Conclusion

Together with the non-commensal nature of L. lactis, short gut transit time in humans, and the ability to express the heterologous protein in the gut, the present study highlights the benefits of bioengineered LAB vectors based mucosal vaccine modality against C. jejuni without the risk of immunotolerance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-021-00444-2.

Growth faltering regardless of chronic diarrhea is associated with mucosal immune dysfunction and microbial dysbiosis in the gut lumen

Despite the impact of childhood diarrhea on morbidity and mortality, our understanding of its sequelae has been significantly hampered by the lack of studies that examine samples across the entire intestinal tract. Infant rhesus macaques are naturally susceptible to human enteric pathogens and recapitulate the hallmarks of diarrheal disease such as intestinal inflammation and growth faltering. Here, we examined intestinal biopsies, lamina propria leukocytes, luminal contents, and fecal samples from healthy infants and those experiencing growth faltering with distant acute or chronic active diarrhea. We show that growth faltering in the presence or absence of active diarrhea is associated with a heightened systemic and mucosal pro-inflammatory state centered in the colon. Moreover, polyclonal stimulation of colonic lamina propria leukocytes resulted in a dampened cytokine response, indicative of immune exhaustion. We also detected a functional and taxonomic shift in the luminal microbiome across multiple gut sites including the migration of Streptococcus and Prevotella species between the small and large intestine, suggesting a decompartmentalization of gut microbial communities. Our studies provide valuable insight into the outcomes of diarrheal diseases and growth faltering not attainable in humans and lays the groundwork to test interventions in a controlled and reproducible setting.