Ehrlichia ruminantium antigens and peptides induce cytotoxic T cell responses in vitro

Ruminant livestock TR V(D)J genes and CDR3 repertoire

Ruminant livestock exhibit certain immune characteristics that make them valuable models for studying T cell receptor diversity and immune responses. This resistance is attributed to their well-developed immune system, comprising both innate and adaptive components. In this review, we delve into the intricate workings of the immune system of ruminant livestock, focusing on innate immunity and adaptive immunity. Specifically, we discuss the TR V(D)J genes (including TRB, TRG, and TRA/D chain) and the characteristics of the complementary determining region 3 (CDR3) repertoire in bovine and ovine species, shedding light on the diversity and functionality of the T-cell receptor(TCR) repertoire in these species. Understanding the distinct features of these germline genes and CDR3 repertoires is essential for unraveling the complexities of immune responses in ruminant livestock. Lastly, we outline future prospects in this field, emphasizing the importance of further research to enhance our understanding of ruminant livestock immunity and its potential applications in disease management, vaccine development, and breeding strategies.

Th1 and Th2 epitopes of Cowdria polymorphic gene 1 of Ehrlichia ruminantium

Cowdria polymorphic gene 1 (cpg1, Erum2510, ERUM_RS01380) has been shown to induce 30% and 100% protection in sheep immunised by deoxyribonucleic acid (DNA) prime combined with DNA boost and DNA prime combined with protein boost, respectively, against heartwater infection via needle challenge. To localise its antigenic regions for inclusion in a multi-epitope DNA vaccine against heartwater, Erum2510 was cleaved into five overlapping subfragments. These subfragments were expressed individually in an Escherichia coli host expression system and evaluated for their ability to induce proliferative responses, Th1 and Th2 cytokines (interferon gamma [IFN-γ] and interleukin 4 [IL-4]) via enzyme-linked immunospot (ELISpot), quantitative real time polymerase chain reaction (qRT-PCR) and flow cytometry. Recombinant (r)proteins 3 and 4 were shown to induce immunodominant Th1 and Th2 immune responses characterised by the secretion of effector cytokines IFN-γ and IL-4 in addition to differential messenger ribonucleic acid (mRNA) expression of tumour necrosis factor (TNF), IL-2, IL-1, IL-18, IL-10, transforming growth factor (TGF), granulocyte-macrophage colony-stimulating factor (GM-CSF) and inducible nitric oxide synthase (iNOS). Thirty-seven overlapping synthetic peptides (16 mer) spanning the lengths of these immunodominant rproteins were synthesised and assayed. A peptide pool comprising p9 and p10 derived from rprotein 3 induced a Th1-biased immune response. A peptide pool comprising p28 and p29 derived from rprotein 4 induced a mixed Th1 and Th2 immune response characterised by secretion of IFN-γ and differential mRNA expression of IL-1, IL-2, IL-10, IL-12, iNOS, TGF, TNF and GM-CSF. Only one of the peptides (p29) induced secretion of IL-4. Phenotypic analysis showed significant activation of cluster of differentiation 8+ (CD8+), cluster of differentiation 4+ (CD4+) and B+ lymphocyte populations. Findings suggest that Erum2510 rproteins and synthetic peptides can induce both cellular and humoral immune responses, thereby implicating their importance in protection against heartwater.Contribution: This study will facilitate the design of an effective multi-epitope DNA vaccine against heartwater that will contribute to control this economically important disease in sub-Saharan Africa and beyond.

Vaccination against Bacterial Infections: Challenges, Progress, and New Approaches with a Focus on Intracellular Bacteria

Many bacterial infections are major health problems worldwide, and treatment of many of these infectious diseases is becoming increasingly difficult due to the development of antibiotic resistance, which is a major threat. Prophylactic vaccines against these bacterial pathogens are urgently needed. This is also true for bacterial infections that are still neglected, even though they affect a large part of the world's population, especially under poor hygienic conditions. One example is typhus, a life-threatening disease also known as "war plague" caused by Rickettsia prowazekii, which could potentially come back in a war situation such as the one in Ukraine. However, vaccination against bacterial infections is a challenge. In general, bacteria are much more complex organisms than viruses and as such are more difficult targets. Unlike comparatively simple viruses, bacteria possess a variety of antigens whose immunogenic potential is often unknown, and it is unclear which antigen can elicit a protective and long-lasting immune response. Several vaccines against extracellular bacteria have been developed in the past and are still used successfully today, e.g., vaccines against tetanus, pertussis, and diphtheria. However, while induction of antibody production is usually sufficient for protection against extracellular bacteria, vaccination against intracellular bacteria is much more difficult because effective defense against these pathogens requires T cell-mediated responses, particularly the activation of cytotoxic CD8+ T cells. These responses are usually not efficiently elicited by immunization with non-living whole cell antigens or subunit vaccines, so that other antigen delivery strategies are required. This review provides an overview of existing antibacterial vaccines and novel approaches to vaccination with a focus on immunization against intracellular bacteria.

A multi-epitope DNA vaccine co-administered with monophosphoryl lipid A adjuvant provides protection against tick transmitted Ehrlichia ruminantium in sheep

Previously, a heartwater experimental DNA vaccine provided 100% protection following laboratory challenge with Ehrlichia ruminantium administered by needle but not against an E. ruminantium tick challenge in the field. A multi-epitope DNA vaccine incorporating both CD4⁺ and CD8⁺ cytotoxic T lymphocytes epitopes could provide a better alternative. In this study, we investigated the use of multi-epitope DNA vaccines against an E. ruminantium experimental tick challenge in sheep. The multi-epitope DNA vaccines were delivered via the intramuscular route and intradermal route using the gene gun in the presence of monophosphoryl lipid A (MPL) adjuvant, which was either applied topically to the gene gun inoculation site or co-administered with the vaccine via the intramuscular route. Initially two constructs namely, pSignal plus and pLamp were tested with MPL applied topically only and no protection was obtained in this formulation. However, when pLamp was co-administered with MPL via the intramuscular route in addition to topical application, its protective efficiency improved to protect 60% of the sheep against tick challenge. In this formulation, the vaccine induced enhanced activation of memory T cell responses both before and after challenge with variations amongst the different sheep possibly due to their different genetic backgrounds. In conclusion, this study showed that a heartwater multi-epitope DNA vaccine, co-administered with MPL adjuvant can protect sheep following a laboratory E. ruminantium tick challenge.