Campylobacter jejuni proteomics for new travellers’ diarrhoea vaccines

Combating Childhood Infections in LMICs: evaluating the contribution of Big Data Big data, biomarkers and proteomics: informing childhood diarrhoeal disease management in Low- and Middle-Income Countries

Despite efforts to reduce the global burden of childhood diarrhoea, 50% of all cases globally occur in children under five years in Low–Income and Middle- Income Countries (LMICs) and knowledge gaps remain regarding the aetiological diagnosis, introduction of diarrhoeal vaccines, and the role of environmental enteric dysfunction and severe acute malnutrition. Biomarkers may assist in understanding disease processes, from diagnostics, to management of childhood diarrhoea and the sequelae to vaccine development. Proteomics has the potential to assist in the identification of new biomarkers to understand the processes in the development of childhood diarrhoea and to aid in developing new vaccines. Centralised repositories that enable mining of large data sets to better characterise risk factors, the proteome of both the patient and the different diarrhoeal pathogens, and the environment, could inform patient management and vaccine development, providing a systems biological approach to address the burden of childhood diarrhoea in LMICs.

Vaccine development for enteric bacterial pathogens: Where do we stand?

Gut infections triggered by pathogenic bacteria lead to most frequently occurring diarrhea in humans accounting for million deaths annually. Currently, only a few licensed vaccines are available against these pathogens for mostly travelers moving to diarrheal endemic areas. Besides commercialized vaccines, there are many formulations that are either under clinical or pre-clinical stages of development and despite several efforts to improve safety, immunogenicity and efficacy, none of them can confer long-term protective immunity, for which repeated booster doses are always recommended. Further in many countries, financial, social and political constraints have jeopardized vaccine development program against these pathogens that enforce us to gather knowledge on safety, tolerability, immunogenicity and protective efficacy regarding the same. In this review, we analyze safety and efficacy issues of vaccines against five major gut bacteria causing enteric infections. The article also simultaneously describes several barriers for vaccine development and further discusses possible strategies to enhance immunogenicity and efficacy.

Update on Campylobacter vaccine development

Background: Acute diarrheal disease caused by viral, bacterial and parasitic infections are a major global health problem with substantial mortality and morbidity in children under five years of age in lower and middle income countries. However, a number of these infections also impact large segments of populations in upper income countries, as well as individuals who travel overseas for work, business or pleasure. Campylobacter has been and continues to be a leading cause of disease burden globally across all income countries.

Aims: The aim of this review is to describe recent understanding in burden of disease, consider the current landscape of Campylobacter vaccine development, and address the challenges that need to be overcome.

Sources: Relevant data from the literature as well as clinical trials described in European and US registries were used to conduct this review.

Content: Despite advances in population health, food security, improved sanitation, water quality and the reduction of poverty, Campylobacter infections continue to plague global populations. The emerging recognition of chronic health consequences attributed to this pathogen is changing the potential valuation of preventive interventions. Advancing development of new vaccines is a present opportunity and holds promise.

Proteomic contributions to our understanding of vaccine and immune responses

Vaccines are one of the greatest public health successes; yet, due to the empirical nature of vaccine design, we have an incomplete understanding of how the genes and proteins induced by vaccines contribute to the development of both protective innate and adaptive immune responses. While the advent of genomics has enabled new vaccine development and facilitated understanding of the immune response, proteomics identifies potentially new vaccine antigens with increasing speed and sensitivity. In addition, as proteomics is complementary to transcriptomic approaches, a combination of both approaches provides a more comprehensive view of the immune response after vaccination via systems vaccinology. This review details the advances that proteomic strategies have made in vaccine development and reviews how proteomics contributes to the development of a more complete understanding of human vaccines and immune responses.

Evaluation of the immunogenicity of Campylobacter jejuni CjaA protein delivered by Salmonella enterica sv. Typhimurium strain with regulated delayed attenuation in chickens

Campylobacter spp. are regarded as the most common bacterial cause of gastroenteritis worldwide, and consumption of chicken meat contaminated by Campylobacter is considered to be one of the most frequent sources of human infection in developed countries. Here we evaluated the immunogenicity and protective efficacy of Salmonella Typhimurium χ9718 producing the Campylobacter jejuni CjaA protein as a chicken anti-Campylobacter vaccine. In this study chickens were orally immunized with a new generation S. Typhimurium strain χ9718 with regulated delayed attenuation in vivo and displaying delayed antigen expression. The immunization with the S. Typhimurium χ9718 strain producing C. jejuni CjaA antigen induced strong immune responses against CjaA in both serum IgY and intestinal IgA, however, it did not result in the significant reduction of intestinal colonization by Campylobacter strain. The low level of protection might arise due to a lack of T cell response. Our results demonstrated that a Salmonella strain with regulated delayed attenuation and displaying regulated delayed antigen expression might be an efficient vector to induce immune response against Campylobacter. It seems that an efficient anti-Campylobacter subunit vaccine should be multicomponent. Since S. Typhimurium χ9718 contains two compatible balanced-lethal plasmids, it can provide the opportunity of cloning several Campylobacter genes encoding immunodominant proteins. It may also be used as a delivery vector of eukaryotic genes encoding immunostimulatory molecules to enhance or modulate functioning of chicken immune system.

Update on human Campylobacter jejuni infections

PURPOSE OF REVIEW

The present review will update the reader to the clinical, epidemiological and immunologic advances in the field of human campylobacteriosis.

RECENT FINDINGS

New advances in human campylobacteriosis include an increased appreciation of the role of Campylobacter jejuni in postinfectious sequelae, a broadened understanding of Campylobacter-associated disease burden and the interplay between host immunity and bacterial factors. Antibiotic management has also become more complex: C. jejuni has undergone a rapid increase in resistance to the fluoroquinolone antibiotics and concurrently, postinfectious irritable bowel syndrome has been associated with a longer duration of untreated infection. In anticipation of new candidate C. jejuni vaccines, progress in understanding human immune responses to infection has been made via human experimental infections. These tightly controlled studies have also increased our understanding of the natural history of campylobacteriosis as well as observations of recrudescent infection following treatment with C. jejuni-sensitive antibiotics.

SUMMARY

As one of the most common agents of bacterial gastroenteritis and a major health burden for both developing world and industrialized nations, Campylobacter infections remain a high priority for research efforts to improve prevention and management. Priorities for the future include vaccine development, pathogen-specific immunity and identification of risk factors for postinfectious sequelae.

Evaluation of Salmonella-vectored Campylobacter peptide epitopes for reduction of Campylobacter jejuni in broiler chickens

Campylobacter is a leading cause of bacterial gastroenteritis in humans and is often linked to contaminated poultry products. Live Salmonella vectors expressing three linear peptide epitopes from Campylobacter proteins Cj0113 (Omp18/CjaD), Cj0982c (CjaA), and Cj0420 (ACE393) were administered to chicks by oral gavage on the day of hatch, and the chicks were challenged with Campylobacter jejuni on day 21. All three candidate vaccines produced consistent humoral immune responses with high levels of serum IgG and mucosal secretory IgA (sIgA), with the best response from the Cj0113 peptide-expressing vector. Campylobacter challenge following vaccination of three candidate vaccine groups decreased Campylobacter recovery from the ileum compared to that for controls on day 32. The Cj0113 peptide-expressing vector reduced Campylobacter to below detectable levels. The Salmonella-vectored Cj0113 subunit vaccine appears to be an excellent candidate for further evaluation as a tool for the reduction of Campylobacter in poultry for improved food safety.