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Dec 2018 DOI 10.14302/issn.2575-1212.jvhc-18-2487
Parasitic infection by the Fasciola hepatica (F. hepatica) promotes susceptibility towards other infections, such as Mycobacterium bovis. As consequence, could affect diagnostic tests for this disease. Hence, the objective of this study was to assess the impact of F. hepatica coinfection on the most commonly used immunodiagnostic bovine tuberculosis (bTB) tests in field conditions in an enzootic area for both diseases. Thus, from a dairy herd located in Hidalgo State, México, displaying a 59.2% and 28% prevalence of fascioliasis and bTB, respectively. Sixty-one cows were analyzed based on their response towards bTB immunodiagnostic tests, such as Single Intradermal Comparative Tuberculin Test (SICTT), gamma-interferon test (BOVIGAM) and enzyme-linked immunosorbent assay (ELISA), along with the assessment of the F. hepatica parasite load and serodiagnosis by ELISA. Three study groups were formed according to test results. Group 1: coinfected (n=22). Group 2: non-parasitized cows, and positive for bTB tests (n=13) and Group 3: parasitized cows without tuberculosis (n=26). In addition, a group of cows kept in fascioliasis - and tuberculosis-free zones were included (Group 4, n=10). A non-parametric Kruskal-Wallis test and a Dunn test were applied to analyze the results. In Group 1, significant differences were observed regarding IFN-γ production, but not for antibody levels to M. bovis or reactivity towards bovine PPD in relation Group 2. While, Groups 1 and 3 did not display difference in antibody levels against F. hepatica. Differences were observed regarding tuberculosis and Fasciola diagnostic tests when both coinfected and infected groups were compared to controls. It is concluded that F. hepatica coinfection in tuberculous animals studied, depressed the production of IFN-γ towards bovine PPD under in vitro conditions, but its reactivity to the SICTT not show to be altered.
Dec 2021 DOI 10.14302/issn.2575-1212.jvhc-21-4034
In bovine tuberculosis (bTB), cellular, humoral, or both types of immune responses have been observed. The purpose of this study was to examine the immune status of tuberculous cows based on the differential cytokine gene expression associated with Th1 (IFN-γ, IL-2), or Th2 (IL-4, IL-10) responses. Twenty-three (23) cows belonging to a dairy herd located in a rural region of the State of Hidalgo, México, were selected for the study. Single Intradermal Comparative Cervical Tuberculin (SICCT) Test, Interferon-Gamma (IFN-γ) Release Assay (BOVIGAM), and Enzyme-Linked Immunosorbent Assay (ELISA) were used for detection of cattle infected by M. bovis. Thirteen cows were positive to all the tests (Group 1); ten cows were positive only to ELISA (Group 2), and the remaining Group (Group 3, control) included cows negative to all the tests. Peripheral blood mononuclear cells (PBMC) from animals were in vitro stimulated by bovin purified protein derivative (PPD), avian PPD, and Concanavalin A (Con A) mitogen for 72h. Changes in the levels of expression of mRNA of the respective cytokines was measured by Reverse Transcription-Polymerase Chain Reaction (RT-PCR) using β-actin gene as internal control. In group 1, PPD bovis and Con A-stimulated cells exhibited high production of IFN-γ, IL-2 and IL-4, but not IL-10. In contrast, PPD avium-stimulated cells displayed a low production of cytokine transcripts. In group 2, cells showed a significant production of IL-10 in response to bovine PPD (P< 0.001). In the control group, a high production of IFN-γ and IL-2 was observed only in Con A-stimulated cells. Post-mortem examinations in animals of group 1 showed slight and medium lesions in lymph nodes, whereas in group 2, the lesions were more extensive. Results indicate differences on gene expression levels of cytokines considered to determine balance in Th1/Th2 response among the evaluated groups. In addition, high levels of antibodies against M. bovis and high IL-10 expression in PBMC together are indicators of progressive bTB when both tuberculin test and IFN-γ assay are negative in tuberculous anergic cattle. Inclusion of serology and IL-10 cytokine expression in in the diagnosis checklist improves detection of infected cattle to help control bovine tuberculosis.
Aug 2017 DOI 10.14302/issn.2575-1212.jvhc-17-1662
Immunization of cattle with the bacillus Calmette-Guérin (BCG) vaccine, especially neonates, induces protection against Mycobacterium bovis (M. bovis) and has been proposed as a strategy for bovine tuberculosis (bTB) control. Therefore, the aim of this study was to evaluate the immune response induced under field conditions in neonatal calves vaccinated with BCG Phipps, a strain that has rarely been evaluated in the bovine population, using interferon (IFN)-γ and tuberculin tests, flow cytometry and enzyme-linked immunosorbent assay. Two groups (vaccinated and control) of 5 calves were monitored for 12 weeks, and increases in the in vitro IFN-γ production, the percentage of cluster of differentiation (CD)8+ T cells and the activation levels of CD4+ and CD8+ T cells were observed 3 to 4 weeks post-vaccination. Bovine purified protein derivative-specific IFN-γ production was increased about 4.8- and 5.5-fold in vaccinated animals compared to non-vaccinated animals 3 and 4 weeks post-vaccination respectively. CD8+ T cells of the vaccinated group were increased 1.6-, 1.5- and 1.6-fold at weeks 2, 3 and 4 respectively. Levels of activation were 1.7- and 1.9-fold higher for CD4+ T cells and 2.3- and 1.8-fold higher for CD8+ T cells in the vaccinated group at weeks 3 and 4 respectively in response to M. bovis antigens. However, no animals (vaccinated or control) showed positive results for the single intradermal comparative tuberculin test (SICTT). Therefore, our results indicate that vaccination with M. bovis BCG Phipps strain stimulated peripheral blood T cell activity and induced a cell-mediated immune response. In addition, vaccination did not interfere with the SICTT, as previously reported, which indicates that this vaccine could be successfully applied in bTB control campaigns.