Cellular and Cytokine Responses in Lymph Node Granulomas of Bacillus Calmette Guérin (BCG)-Vaccinated and Non-vaccinated Cross-Breed Calves Naturally Infected With Mycobacterium bovis.

Asegedech Sirak,Gobena Ameni,Balako Gumi,Stefan Berg,Begna Tulu,Berecha Bayissa,Francisco J Salguero

doi:10.3389/fvets.2021.698800

Abstract

Local immunological responses at the site of infections, such as at the lymph nodes and lungs, do play a role in containing infection caused by Mycobacterium bovis (M. bovis). This bovine tuberculosis (bTB) study was conducted to evaluate cellular and cytokine responses in the lymph nodes and lungs of BCG-vaccinated and non-vaccinated calves that were naturally infected with M. bovis. Immunohistochemical assays were used for examination of the responses of macrophages, T cells, cytokines and chemical mediators of 40 (22 vaccinated and 18 non-vaccinated) Holstein-Friesian-zebu crossbred calves that were naturally exposed for 1 year to a known bTB positive cattle herd. The incidence rates of bTB visible lesion were 68.2% (15/22) and 89% (16/18) in vaccinated and non-vaccinated calves, respectively. The local responses of CD4+ and CD8+ T cells, and those of IFN-γ and TNF-α within the lesions, were stronger (P < 0.05) in BCG-vaccinated calves than in non-vaccinated calves. However, there was no statistically significant difference between the two groups (P > 0.05) in the response of CD68+ cells. Thus, the findings of this study indicated stronger responses of a set of immunological cells and markers at the local granulomas of BCG-vaccinated calves than in non-vaccinated calves. Furthermore, BCG vaccination may also play a role in reducing the severity of the gross pathology at the primary site of infection.

Highlights

Bovine tuberculosis is a chronic progressive disease of cattle and other animals that is caused by Mycobacterium bovis (M. bovis) and is characterized by progressive development of granulomatous lesions, termed as tubercles, in different tissues
Male HF-zebu crossbreed calves were recruited within 2 weeks of age from known bovine tuberculosis (bTB) free cattle farms as confirmed by the Single Intradermal Comparative Cervical Tuberculin (SICCT) test for which PPD-A and PPD-B were sourced from Thermo Fisher (Lelystad, the Netherlands)
BTB visible lesions were detected in 68.0% (15/22) of the BCG vaccinated and 89.0% (16/18) of the unvaccinated calves

Summary

Introduction

Bovine tuberculosis (bTB) is a chronic progressive disease of cattle and other animals that is caused by Mycobacterium bovis (M. bovis) and is characterized by progressive development of granulomatous lesions, termed as tubercles, in different tissues. BTB poses a major economic problem worldwide costing US$3 billion annually through infecting over 50 million cattle [1]. It causes zoonotic TB in humans in developing countries in Africa, Asia and Latin America [2]. The conventional control measures for bTB are based on a test-andslaughter method, which is less likely to be implemented by the developing countries because of socioeconomic reasons [3]. The test-and-slaughter control method have been shown not to be effective in some developed countries, like the United Kingdom and New Zealand, because of the interference of reservoirs of M. bovis in infected wildlife [4, 5]. Alternative control methods such as the use of vaccination are required for improved control of bTB

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