Genome-wide epitope mapping across multiple host species reveals significant diversity in antibody responses to Coxiella burnetii vaccination and infection.

Coxiella burnetii is an important zoonotic bacterial pathogen of global importance, causing the disease Q fever in a wide range of animal hosts. Ruminant livestock, in particular sheep and goats, are considered the main reservoir of human infection. Vaccination is a key control measure, and two commercial vaccines based on formalin-inactivated C. burnetii bacterins are currently available for use in livestock and humans. However, their deployment is limited due to significant reactogenicity in individuals previously sensitized to C. burnetii antigens. Furthermore, these vaccines interfere with available serodiagnostic tests which are also based on C. burnetii bacterin antigens. Defined subunit antigen vaccines offer significant advantages, as they can be engineered to reduce reactogenicity and co-designed with serodiagnostic tests to allow discrimination between vaccinated and infected individuals. This study aimed to investigate the diversity of antibody responses to C. burnetii vaccination and/or infection in cattle, goats, humans, and sheep through genome-wide linear epitope mapping to identify candidate vaccine and diagnostic antigens within the predicted bacterial proteome. Using high-density peptide microarrays, we analyzed the seroreactivity in 156 serum samples from vaccinated and infected individuals to peptides derived from 2,092 open-reading frames in the C. burnetii genome. We found significant diversity in the antibody responses within and between species and across different types of C. burnetii exposure. Through the implementation of three different vaccine candidate selection methods, we identified 493 candidate protein antigens for protein subunit vaccine design or serodiagnostic evaluation, of which 65 have been previously described. This is the first study to investigate multi-species seroreactivity against the entire C. burnetii proteome presented as overlapping linear peptides and provides the basis for the selection of antigen targets for next-generation Q fever vaccines and diagnostic tests.

Efficacy of Phase I and Phase II Coxiella burnetii Bacterin Vaccines in a Pregnant Ewe Challenge Model.

The bacterium Coxiella burnetii can cause the disease Q-fever in a wide range of animal hosts. Ruminants, including sheep, are thought to play a pivotal role in the transmission of C. burnetii to humans; however, the only existing livestock vaccine, namely, Coxevac® (Ceva Animal Health Ltd., Libourne, France), a killed bacterin vaccine based on phase I C. burnetii strain Nine-Mile, is only approved for use in goats and cattle. In this study, a pregnant ewe challenge model was used to determine the protective effects of Coxevac® and an experimental bacterin vaccine based on phase II C. burnetii against C. burnetii challenge. Prior to mating, ewes (n = 20 per group) were vaccinated subcutaneously with either Coxevac®, the phase II vaccine, or were unvaccinated. A subset of pregnant ewes (n = 6) from each group was then challenged 151 days later (~100 days of gestation) with 106 infectious mouse doses of C. burnetii, Nine-Mile strain RSA493. Both vaccines provided protection against C. burnetii challenge as measured by reductions in bacterial shedding in faeces, milk and vaginal mucus, and reduced abnormal pregnancies, compared to unvaccinated controls. This work highlights that the phase I vaccine Coxevac® can protect ewes against C. burnetii infection. Furthermore, the phase II vaccine provided comparable levels of protection and may offer a safer and cost-effective alternative to the currently licensed vaccine.

Focused B cell response to recurring gluten motif with implications for epitope spreading in celiac disease.

Antibodies to deamidated gluten peptides are accurate diagnostic markers of celiac disease. However, binding of patient antibodies to all possible gluten epitopes has not previously been investigated. Here, we assess serum antibody specificity across the gluten proteome by use of high-density peptide arrays. We confirm the importance of deamidation for antibody binding, and we show that the response is remarkably focused on the known epitope QPEQPFP (where E results from deamidation of Q). In addition, we describe an epitope in native (non-deamidated) gluten, QQPEQII (where E is gene encoded), which is associated with both B cell and T cell reactivity. Antibodies to this native epitope are cross-reactive with the major deamidated epitope due to recognition of the shared PEQ motif. Since cross-reactive B cells can present peptides to different gluten-specific T cells, we propose that such B cells play a role in epitope spreading by engaging T cells with multiple specificities.

Depletion of regulatory T cells leads to an exacerbation of delayed-type hypersensitivity arthritis in C57BL/6 mice that can be counteracted by IL-17 blockade.

Rodent models of arthritis have been extensively used in the elucidation of rheumatoid arthritis (RA) pathogenesis and are instrumental in the development of therapeutic strategies. Here we utilise delayed-type hypersensitivity arthritis (DTHA), a model in C57BL/6 mice affecting one paw with synchronised onset, 100% penetrance and low variation. We investigate the role of regulatory T cells (Tregs) in DTHA through selective depletion of Tregsand the role of IL-17 in connection with Tregdepletion. Given the relevance of Tregsin RA, and the possibility of developing Treg-directed therapies, this approach could be relevant for advancing the understanding of Tregsin inflammatory arthritis. Selective depletion of Tregswas achieved using aFoxp3-DTR-eGFPmouse, which expresses the diphtheria toxin receptor (DTR) and enhanced green fluorescent protein (eGFP) under control of theFoxp3gene. Anti-IL-17 monoclonal antibody (mAb) was used for IL-17 blockade. Numbers and activation of Tregsincreased in the paw and its draining lymph node in DTHA, and depletion of Tregsresulted in exacerbation of disease as shown by increased paw swelling, increased infiltration of inflammatory cells, increased bone remodelling and increased production of inflammatory mediators, as well as increased production of anti-citrullinated protein antibodies. Anti-IL-17 mAb treatment demonstrated that IL-17 is important for disease severity in both the presence and absence of Tregs, and that IL-17 blockade is able to rescue mice from the exacerbated disease caused by Tregdepletion and caused a reduction in RANKL, IL-6 and the number of neutrophils. We show that Tregsare important for the containment of inflammation and bone remodelling in DTHA. To our knowledge, this is the first study using theFoxp3-DTR-eGFPmouse on a C57BL/6 background for Tregdepletion in an arthritis model, and we here demonstrate the usefulness of the approach to study the role of Tregsand IL-17 in arthritis.