Detection of tetanus toxoid-specific memory T cells in equine lymph nodes but not in peripheral blood

CD154 Expression Indicates T Cell Activation Following Tetanus Toxoid Vaccination of Horses

Despite the relevance of adaptive immunity against equine pathogens antigen-specific T cell responses of horses are not well characterized and the lack of insight into T cell responses hampers the understanding of the pathogeneses of important diseases. In this study we used tetanus toxoid (TT) as a well-defined antigen to characterize antigen-reactive T cells. Six healthy adult horses received a routine booster against tetanus with an immune stimulating complex (ISCOM)-based vaccine and were followed for 28 days. TT-specific serum antibodies were quantified by ELISA and increased in all horses by day 7 after vaccination. CD154 is an established indicator of antigen-reactive T helper cells in other species, but has not been characterized in horses. CD154 detection in equine PBMC by an anti-human CD154 antibody (clone 5C8) was confirmed by Western blots and then applied for flow cytometry. As a common indicator of equine T cell activation, cytokine induction was studied in parallel. T cells were analyzed by multicolor flow cytometry of PBMC after re-stimulation with TT in vitro. Reactive T helper (Th) cells were characterized by increased frequencies of CD4⁺CD154⁺ lymphocytes in in vitro TT-re-stimulated PBMC on day 14 after vaccination of the horses compared to pre-vaccination. The majority of all CD154⁺ cells after TT re-stimulation were CD4⁺ Th cells, but CD154 was also induced on CD4^- cells albeit in lower frequencies. CD154⁺CD4⁺ Th cells were enriched in cytokine-expressing cells compared to CD154^-CD4⁺ Th cells. Similar to the CD4⁺CD154⁺ frequencies, CD4⁺IL-4⁺, CD4⁺IFN-γ⁺ and CD4⁺TNF-α⁺ were increased after vaccination, but IL-4⁺ increased later than IFN-γ⁺ and CD4⁺TNF-α⁺, which already exceeded pre-vaccination frequencies on day 7. CD4⁺CD154⁺ frequencies correlated positively with those of CD4⁺IL-4⁺ (Th2) on day 14, and negatively with CD4⁺IFN-γ⁺ induction on day 7, but did not correlate with CD4⁺TNF-α⁺ frequencies or TT-specific antibody concentrations. CD154 appears to be a useful marker of antigen-reactive equine Th cells in combination with cytokine expression. The T cell analyses established here with TT can be applied to other antigens relevant for infections or allergies of horses and in horse models for translational research.

Vaccination of donkeys against Babesia equi using killed merozoite immunogen

Protective efficacy of a killed Babesia equi immunogen was assessed in donkeys. The immunogen was prepared from B. equi infected blood so as to contain lysate of 2 x 10(10) parasitised erythrocytes per dose. The immunogen was mixed with an adjuvant Quil A (3mg) and inoculated into four susceptible donkeys (group I). A booster inoculation was given after 21 days of first inoculation followed by challenge with fresh infected blood containing 1x10(11) parasitised erythrocytes 14 days later. Two groups of two donkey each were included as adjuvant only control (group II) and uninoculated control (group III), respectively. After challenge, donkeys were observed for a period of 4 weeks. The immunised donkeys (group I) showed significantly high (P<0.05%) enzyme linked immunosorbant assay (ELISA) antibody titres and significantly high (P<0.05%) stimulation indices (SI) in lymphocyte proliferation assay (LPA) than that of groups II and III donkeys from day 14 PI and day 7 PI onwards, respectively. All the immunised donkeys withstood lethal challenge, whereas, control donkeys died within 10 days post-challenge (PC). Parasitaemia rose to mean maximum 8.0+/-6.0% for 5-7 days in group I donkeys after challenge, whereas, it rose to 55.5% in control groups. The percent rise in rectal temperature, total leucocyte count (TLC), fall in haemoglobin (Hb) was less severe in immunised group as compared to the control groups. Two immunised-challenged donkeys were splenectomised recovery. No parasites appeared in the blood during the observation period following splenectomy 4-week. Three times increase in skin-fold thickness at 24h of intradermal inoculation prior to challenge in group I donkeys was observed, thus, indicating a good in vivo cell mediated immunity. It can be concluded that the B. equi immunogen along with adjuvant Quil A, used in the present study, was optimum to elicit a strong immune response against B. equi in experimental donkeys.

Equine peripheral blood mononuclear cells proliferate in response to tetanus toxoid antigen

It has been reported that equine peripheral blood mononuclear cells (PBMNs) do not proliferate in response to tetanus toxoid (TT) (Frayne and Stokes 1995, Research in Veterinary Science 59, 79-81). Here we demonstrate that lymphocyte proliferation responses to TT, which are characteristic of a recall antigen, may be achieved under certain culture conditions. Given that TT vaccination is routinely applied to many horses, TT is a suitable antigen for the investigation of cellular immune responses by peripheral blood mononuclear cells in the horse.

The cellular response of lambs to Brucella ovis before and after birth

The immunological response of lambs to Brucella ovis before and after birth was investigated. The establishment of indwelling cannulas in the efferent prescapular lymphatic ducts of foetal lambs allowed continual monitoring of the immune response of a single lymph node. Foetal lambs in the last trimester of pregnancy were shown to mount a strong cell-mediated immune response to B. ovis. Lymphocytes from the challenged lymph node stimulated with B. ovis in vitro usually first reacted significantly and had highest [3H]-thymidine incorporation between 4 and 6 days after primary and secondary challenge, whereas, lymphocytes from the unchallenged node did not exhibit significant [3H]-thymidine incorporation until some 24 h later. Lymphocytes from these lambs challenged as foetuses still exhibited significant [3H]-thymidine incorporation in response to B. ovis for 4 to 5 months after birth. The proportion of surface immunoglobulin-positive cells in efferent prescapular lymph of unchallenged lambs ranged from 0.5 to 2.0% but after B. ovis challenge this proportion ranged from 2.7 to 8.7% between 4 to 6 days after challenge. By 9 to 12 days after challenge, the proportion had declined to pre-challenge values.