Applications of Platform Technologies in Veterinary Vaccinology and the benefits for One Health

The animal-human interface has played a central role in advances made in vaccinology for the past two centuries. Many traditional veterinary vaccines were developed by growing, attenuating, inactivating and fractioning the pathogen of interest. While such approaches have been very successful, we have reached a point where they have largely been exhausted and alternative approaches are required. Furthermore, although subunit vaccines have enhanced safety profiles and created opportunities for combined discrimination between vaccinated and infected animal (DIVA) approaches, their functionality has largely been limited to diseases that can be controlled by humoral immunity until very recently. We now have a new generation of adjuvants and delivery systems that can elicit CD4 + T cells and/or CD8 + T cell responses in addition to high-titre antibody responses. We review the current vaccine platform technologies, describe their roles in veterinary vaccinology and discuss how knowledge of their mode of action allows informed decisions on their deployment with wider benefits for One Health

An investigation of factors involved in the development of eosinophilic responses in rodents

Elevated numbers of blood and tissue eosinophils were induced in mice and rats by parasitic and non-parasitic means. Mice infected with the nematode Trichinella spiralis developed a peripheral blood eosinophilia which peaked approximately 21 days post infection. Histological examination of various tissues showed that the blood does not always reflect total body changes in eosinophil distribution. The numbers of eosinophils in skeletal muscle continued to increase at a time when the numbers of eosinophils in the blood were decreasing. The involvement of T. spiralis antigens in eliciting this eosinophilia was investigated using an artificial method to localize parasitic material in tissue. A homogenate of T. spiralis larvae was shown to be antigenic by precipitation with serum from a T. spiralis- infected rabbit. This antigenic preparation, designated TSAG, was also capable of eliciting a humoral response when injected into a rabbit. Although not a pure antigenic preparation, the TSAG did contain antigenic components which could bind to inert latex particles. This was demonstrated in vitro by agglutination and fluorescent techniques. When these TSAG-coated particles were injected into mice in such a manner as to result in their embolization in the pulmonary vasculature, they elicited a greater peripheral blood eosinophilic response than mcoated particles. However, similar studies on mice injected with latex particles coated with a non-parasite antigen (BGG) induced a comparable eosinophilia to that induced by parasite antigen- coated particles. The eosinophilia could not, therefore, be directly related to TSAG. Histological measurements of pulmonary cellular accumulations around the embolized particles also showed that TSAG was not more effective than BGG at inducing pulmonary cell accumulations, and furthermore, that uncoated particles also induced cell accumulations. The response to uncoated particles suggested a non-specific mechanism for the induction of eosinophilic responses. This latex model was used to investigate the ability of athymic (Rnu/Rnu) nude rats to develop an eosinophilia following pulmonary embolization of BGG-coated or uncoated latex particles. The number of circulating eosinophils increased in both cases, with the greater response occurring in rats injected with latex-BGG. A similar response was observed in euthymic (Rnu/+) littermates. Pretreatment of both Rnu/Rnu and Rnu/+ rats with antithymocyte serum altered the magnitude of the response but did not totally abrogate it. Studies on interleukin-1 activity in lung lavages recovered from these rats showed that injection of latex particles did not enhance alveolar macrophage activity 48 hours after their pulmonary embolization. The level of activity was similar in both Rnu/Rnu and Rnu/+ rats suggesting that macrophages were not involved in the response in Rnu/Rnu rats which are T cell deficient. The results show that the possibility of a residual T cell population in these rats cannot be excluded. In addition to these responses to physical manipulations, evidence is provided for inherent fluctuations in the number of circulating eosinophils, emphasizing the importance of careful experimental design when investigating haematological phenomena

Immunophenotyping of sheep paraffin-embedded peripheral lymph nodes

Sheep are not only a major livestock species globally, they are also an important large animal model for biomedical research and have contributed to our understanding of the ontogeny and architecture of the mammalian immune system. In this study, we applied immunohistochemistry and multicolor immunofluorescence in fixed and paraffin-embedded lymph nodes to phenotype the key populations of antigen presenting cells, lymphocytes and stromal cells that orchestrate the host adaptive immune response. We used an extensive panel of antibodies directed against markers associated with dendritic cells (MHC class II, CD83 and CD208), macrophages (CD11b, CD163 and CD169), stromal cells (CNA.42, S100 and CD83), and lymphocytes (CD3, Pax5, CD4, CD8). Using different methods of tissue fixation and antigen retrieval, we provide a detailed immunophenotyping of sheep lymph nodes including the identification of potential subpopulations of antigen presenting cells and stromal cells. By characterizing cells expressing combinations of these markers in the context of their morphology and location within the lymph node architecture, we provide valuable new tools to investigate the structure, activation and regulation of the sheep immune system in health and disease

Selection of Neospora caninum antigens stimulating bovine CD4+ve T cell responses through immuno-potency screening and proteomic approaches

Neospora caninum is recognised worldwide as a major cause of bovine infectious abortion. There is a real need to develop effective strategies to control infection during pregnancy which may lead to either abortion or congenital transmission. Due to the intracellular nature of the parasite, cell-mediated immune (CMI) responses involving CD4+ve, CD8+ve, γ/δ TCR+ve T cells and NK cells, as well as production of IFN-γ, are thought to be important for protective immunity. In this study we applied a combination of proteomic and immunological approaches to identify antigens of N. caninum that are recognized by CD4+ve T cell lines derived from infected cattle. Initially, N. caninum tachyzoite Water Soluble Antigens (NcWSA) were fractionated by size-exclusion HPLC and then screened for immune-potency using CD4+ve T cell lines. LC-ESI-MS/MS (liquid chromatography electrospray ionisation tandem mass spectrometry) was employed to catalogue and identify the proteins comprising three immunologically selected fractions and led to the identification of six N. caninum target proteins as well as sixteen functional orthologues of Toxoplasma gondii. This approach allows the screening of biologically reactive antigenic fractions by the immune cells responsible for protection (such as bovine CD4+ve cells) and the subsequent identification of the stimulating components using tandem mass spectrometry

Antibody responses to recombinant protein fragments of the major outer membrane protein and polymorphic outer membrane protein POMP90 in Chlamydophila abortus-infected pregnant sheep

Chlamydophila abortus is one of the major causes of infectious abortion in pregnant sheep (enzootic abortion of ewes or EAE) worldwide. Organisms shed in infected placentas and uterine discharges at lambing time are the main sources of environmental contamination, responsible for transmission to susceptible animals and possible human contacts. In the present study, a recently developed test, based on a recombinant fragment of the polymorphic outer membrane protein POMP90 (rOMP90-4 indirect enzyme-linked immunosorbent assay [iELISA]) and one based on the variable segment 2 (VS2) region of the major outer membrane protein (MOMP) (MOMP VS2 iELISA) were compared using sera from C. abortus-infected ewes at different stages throughout pregnancy. The rOMP90 iELISA detected antibody much earlier in pregnancy than the MOMP iELISA, which, like the complement fixation test, detected antibody only at the time of abortion or lambing. No anti-MOMP antibody response could be detected in three of seven experimentally infected ewes. Furthermore, the rOMP90 iELISA detected antibody in an animal that seroconverted during the course of the study, which the MOMP iELISA failed to detect. Overall, the results show that the rOMP90-4 iELISA is considerably more sensitive than the MOMP VS2 iELISA for identifying animals infected with C. abortus. Earlier detection of infection will allow appropriate control measures to be taken to reduce environmental contamination, thus limiting the spread of infection, financial losses, and the possible risks of zoonotic transmission to humans