Characterization of effector and memory T cell subsets in the immune response to bovine tuberculosis in cattle

Cultured IFN-γ ELISPOT assays are primarily a measure of central memory T cell (Tcm) responses with humans; however, this important subset of lymphocytes is poorly characterized in cattle. Vaccine-elicited cultured IFN-γ ELISPOT responses correlate with protection against bovine tuberculosis in cattle. However, whether this assay measures cattle Tcm responses or not is uncertain. The objective of the present study was to characterize the relative contribution of Tcm (CCR7+, CD62Lhi, CD45RO+), T effector memory (Tem, defined as: CCR7-, CD62Llow/int, CD45RO+), and T effector cells (CCR7-, CD62L-/low, CD45RO-), in the immune response to Mycobacterium bovis. Peripheral blood mononuclear cells (PBMC) from infected cattle were stimulated with a cocktail of M. bovis purified protein derivative, rTb10.4 and rAg85A for 13 days with periodic addition of fresh media and rIL-2. On day 13, cultured PBMC were re-stimulated with medium alone, rESAT-6:CFP10 or PPDb with fresh autologous adherent cells for antigen presentation. Cultured cells (13 days) or fresh PBMCs (ex vivo response) from the same calves were analyzed for IFN-γ production, proliferation, and CD4, CD45RO, CD62L, CD44, and CCR7 expression via flow cytometry after overnight stimulation. In response to mycobacterial antigens, ~75% of CD4+ IFN-γ+ cells in long-term cultures expressed a Tcm phenotype while less than 10% of the ex vivo response consisted of Tcm cells. Upon re-exposure to antigen, long-term cultured cells were highly proliferative, a distinctive characteristic of Tcm, and the predominant phenotype within the long-term cultures switched from Tcm to Tem. These findings suggest that proliferative responses of Tcm cells to some extent occurs simultaneously with reversion to effector phenotypes (mostly Tem). The present study characterizes Tcm cells of cattle and their participation in the response to M. bovis infection

Application of long-term cultured interferon-γ enzyme-linked immunospot assay for assessing effector and memory T cell responses in cattle

doi:10.3791/52833 (2015). Effector and memory T cells are generated through developmental programing of naïve cells following antigen recognition. If the infection is controlled up to 95 % of the T cells generated during the expansion phase are eliminated (i.e., contraction phase) and memory T cells remain, sometimes for a lifetime. In humans, two functionally distinct subsets of memory T cells have been described based on the expression of lymph node homing receptors. Central memory T cells express C-C chemokine receptor 7 and CD45RO and are mainly located in T-cell areas of secondary lymphoid organs. Effector memory T cells express CD45RO, lack CCR7 and display receptors associated with lymphocyte homing to peripheral or inflamed tissues. Effector T cells do not express either CCR7 or CD45RO but upon encounter with antigen produce effector cytokines, such as interferon-γ. Interferon-γ release assays are used for the diagnosis of bovine and human tuberculosis and detect primaril

Senecavirus A 3C Protease Mediates Host Cell Apoptosis Late in Infection

Senecavirus A (SVA), an oncolytic picornavirus used for cancer treatment in humans, has recently emerged as a vesicular disease (VD)-causing agent in swine worldwide. Notably, SVA-induced VD is indistinguishable from foot-and-mouth disease (FMD) and other high-consequence VDs of pigs. Here we investigated the role of apoptosis on infection and replication of SVA. Given the critical role of the nuclear factor-kappa B (NF-κB) signaling pathway on modulation of cell death, we first assessed activation of NF-κB during SVA infection. Results here show that while early during infection SVA induces activation of NF-κB, as evidenced by nuclear translocation of NF-κB-p65 and NF-κB-mediated transcription, late in infection a cleaved product corresponding to the C-terminus of NF-κB-p65 is detected in infected cells, resulting in lower NF-κB transcriptional activity. Additionally, we assessed the potential role of SVA 3C protease (3Cpro) in SVA-induced host-cell apoptosis and cleavage of NF-κB-p65. Transient expression of SVA 3Cpro was associated with cleavage of NF-κB-p65 and Poly (ADP-ribose) polymerase (PARP), suggesting its involvement in virus-induced apoptosis. Most importantly, we showed that while cleavage of NF-κB-p65 is secondary to caspase activation, the proteolytic activity of SVA 3Cpro is essential for induction of apoptosis. Experiments using the pan-caspase inhibitor Z-VAD-FMK confirmed the relevance of late apoptosis for SVA infection, indicating that SVA induces apoptosis, presumably, as a mechanism to facilitate virus release and/or spread from infected cells. Together, these results suggest an important role of apoptosis for SVA infection biology

Potential for rapid antibody detection to identify tuberculous cattle with non-reactive tuberculin skin test results

Abstract Background Bovine tuberculosis (TB) control programs generally rely on the tuberculin skin test (TST) for ante-mortem detection of Mycobacterium bovis-infected cattle. Results Present findings demonstrate that a rapid antibody test based on Dual-Path Platform (DPP®) technology, when applied 1-3 weeks after TST, detected 9 of 11 and 34 of 52 TST non-reactive yet M. bovis-infected cattle from the US and GB, respectively. The specificity of the assay ranged from 98.9% (n = 92, US) to 96.0% (n = 50, GB) with samples from TB-free herds. Multi-antigen print immunoassay (MAPIA) revealed the presence of antibodies to multiple antigens of M. bovis in sera from TST non-reactors diagnosed with TB. Conclusions Thus, use of serologic assays in series with TST can identify a significant number of TST non-reactive tuberculous cattle for more efficient removal from TB-affected herds

Pathogenesis and Host Responses to Viral Diseases in Livestock Species

Infectious diseases in livestock species are responsible for significant economic losses worldwide and constantly threaten food security [...

Application of Long-term cultured Interferon-γ Enzyme-linked Immunospot Assay for Assessing Effector and Memory T Cell Responses in Cattle

doi:10.3791/52833 (2015). Effector and memory T cells are generated through developmental programing of naïve cells following antigen recognition. If the infection is controlled up to 95 % of the T cells generated during the expansion phase are eliminated (i.e., contraction phase) and memory T cells remain, sometimes for a lifetime. In humans, two functionally distinct subsets of memory T cells have been described based on the expression of lymph node homing receptors. Central memory T cells express C-C chemokine receptor 7 and CD45RO and are mainly located in T-cell areas of secondary lymphoid organs. Effector memory T cells express CD45RO, lack CCR7 and display receptors associated with lymphocyte homing to peripheral or inflamed tissues. Effector T cells do not express either CCR7 or CD45RO but upon encounter with antigen produce effector cytokines, such as interferon-γ. Interferon-γ release assays are used for the diagnosis of bovine and human tuberculosis and detect primaril

CD62L and CD44 expression by Tcm, Tem and effector CD4+ cells in long-term (14 day) cultures.

<p>Analysis of long-term cultured PBMCs was performed ~ 8 weeks after aerosol challenge with virulent <i>M</i>. <i>bovis</i>. Cells were stimulated with a cocktail of rAg85A (1 μg/ml), rTB10.4 (1 μg/ml), and rESAT-6:CFP10 (1 μg/ml), as well as PPDb (5 μg/ml) for 13 days followed by transfer to 96 well round bottom plates with APCs and addition of PPDb or rESAT-6:CFP10. Data are presented as mean fluorescence intensity (MFI, y-axis, ± SEM) of CD62L or CD44 by CD4⁺ cells of the various effector / memory subsets (x-axis). <b>(A)</b> CD62L expression by Tcm, Tem and effector cells in response to PPDb and rESAT-6:CFP10. <b>(B)</b> CD44 expression on Tcm, Tem and effector cells in response to PPDb and rESAT-6:CFP10. Tcm, Tem and effector cell phenotypes were as defined in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122571#pone.0122571.g002" target="_blank">Fig 2</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122571#pone.0122571.s003" target="_blank">S3 Fig</a> Paired Student's t-tests (n = 8).</p

Long-term cultured and <i>ex vivo</i> IFN- γ responses by cattle after <i>M</i>. <i>bovis</i> aerosol challenge.

<p>Cultured ELISPOT analysis was performed ~3 weeks after challenge with virulent <i>M</i>. <i>bovis</i>. Long-term cultured cells were generated by stimulating PBMC with a cocktail of rAg85A (1 μg/ml), rTB10.4 (1 μg/ml), and rESAT-6:CFP10 (1 μg/ml) antigens as well as PPDb (5 μg/ml) for 13 days followed by transfer to ELISPOT plates with APCs and addition of either rESAT-6:CFP10, PPDb or medium alone. For the <i>ex vivo</i> response, freshly isolated PBMCs were stimulated with rESAT-6:CFP10, PPDb or medium alone for 16h. Medium control responses were subtracted from antigen-stimulated responses and results are presented as mean spot forming cells (SFC)/million cells (± SEM, n = 8) for <b>(A)</b> long-term culture or <b>(B)</b><i>ex vivo</i> conditions. <b>(C)</b> The kinetics of the response is shown as the percent of CD4⁺ cells producing IFN-γ in long-term cultures at 3, 6, 8, and 12 weeks post infection (WPI n = 6). Two-way ANOVA (Šídák’s multiple comparison post-test).</p

Representative gating strategy for evaluation of CD45RO and CCR7 expression on CD4 T cells producing IFN-γ.

<p>Approximately 8 weeks after aerosol challenge with <i>M</i>. <i>bovis</i>, long-term cultures were generated by stimulating PBMC with a cocktail of rAg85A (1 μg/ml), rTB10.4 (1 μg/ml) and rESAT-6:CFP10 (1 μg/ml) as well as PPDb (5 μg/ml) for 13 days followed by transfer of cells to ELISPOT plates with APCs and restimulation with PPDb. Gating hierarchy (gating sequence as depicted by the arrows): <b>(A)</b> Single cells (within the oblong gate), <b>(B)</b> Lymphocytes (within the polygon gate), <b>(C)</b> CD4⁺ cells, <b>(D)</b> CD4⁺ cells producing IFN-γ, and <b>(E)</b> CD45RO and CCR7 expression for determination of effector/memory phenotypes.</p