Use of the MILLIPLEX® bovine cytokine/chemokine multiplex assay to identify Mycobacterium bovis-infection biomarkers in African buffaloes (Syncerus caffer)

Use of a commercial feed supplement based on diatom earth and yeast products on oxidative status and in vitro immune response in buffaloes during peripartum

The transition period is a critical metabolic phase for dairy ruminants, especially those with high production levels. In spite of this, little is still known about dairy water buffalo. The aim of this study was to evaluate the effect of a commercial feed additive based on diatomaceous earth and hydrolyzed yeasts on health status, milk quality, and immune response of buffalo cows during the transition period. Eighty healthy Water buffaloes (Bubalus bubalis) of Italian Mediterranean breed were included in the trial. They were subdivided into two groups: one group received the additive (n = 40) while the control group (n = 40) received a placebo. The trial lasted 120 d, from 60 d before calving to 60 d in milk. Blood samples were collected from each buffalo at -60 (60 d from the expected calving), -30, 0 (calving), +15, +30, and +60 d (respectively, i.e., 15, 30, and 60 d in milking). The biochemical as well as the oxidative profile, and the antioxidant power and enzymatic activity were evaluated in the samples obtained. Moreover, acute phase proteins, reactive proteins, and interleukin plasma levels were determined. Peripheral blood mononuclear cells (PBMCs) and monocytes were isolated and viability, reactive oxygen species (ROS), and reactive nitrogen species were measured on PBMC and monocytes. The introduction of additives enhanced the total antioxidant capacity and enzyme activity, while no differences were observed in oxidation products throughout the trial. Additionally, it significantly reduced the synthesis of ROS in polymorphonuclear cells, supporting a potential positive response in animals experiencing inflammation. The impact of oxidation on the products was not evident. Despite higher enzyme levels in plasma, this did not necessarily correspond to significantly increased enzymatic activity but rather indicated a higher potential. From these results, it was evident that the transition period in buffaloes differs notably from what reported in the literature for cows, probably due to the absence of common postpartum production diseases in dairy cows and lower metabolic challenges linked to lower milk production in buffaloes. Few parameters exhibited notable changes during the transition period in buffaloes, notably certain antioxidant enzymes, PBMC viability, PBMC ROS production, and Hp levels.

Brain-Derived Neurotrophic Factor, Kynurenine Pathway, and Lipid-Profiling Alterations as Potential Animal Welfare Indicators in Dairy Cattle

Complete animal welfare evaluation in intensive farming is challenging. With this study, we investigate new biomarkers for animal physical and mental health by comparing plasma expression of biochemical indicators in dairy cows reared in three different systems: (A) semi-intensive free-stall, (B) non-intensive tie-stall, and (C) intensive free-stall. Additionally, protein levels of mature brain-derived neurotrophic factor (mBDNF) and its precursor form (proBDNF) and indoleamine 2,3-dioxygenase (IDO1) specific activity were evaluated in brain samples collected from 12 cattle culled between 73 and 138 months of age. Alterations in plasma lipid composition and in the kynurenine pathway of tryptophan metabolism were observed in the tie-stall-reared animals. The total plasma BDNF concentration was higher in tie-stall group compared to the two free-housing groups. Brain analysis of the tie-stall animals revealed a different mBDNF/proBDNF ratio, with a higher level of proBDNF (p < 0.001). Our data are similar to previous studies on animal models of depression, which reported that inhibition of the conversion of proBDNF in its mature form and/or elevated peripheral kynurenine pathway activation may underlie cerebral biochemical changes and induce depressive-like state behavior in animals.

A proof-of-concept study to investigate the efficacy of heat-inactivated autovaccines in Mycobacterium caprae experimentally challenged goats

This study aimed to assess the efficacy of a heat-inactivated Mycobacterium caprae (HIMC) vaccine in goats experimentally challenged with the same strain of M. caprae. Twenty-one goats were divided into three groups of seven: vaccinated with heat-inactivated Mycobacterium bovis (HIMB), with HIMC and unvaccinated. At 7 weeks post-vaccination all animals were endobronchially challenged with M. caprae. Blood samples were collected for immunological assays and clinical signs were recorded throughout the experiment. All goats were euthanized at 9 weeks post-challenge. Gross pathological examination, analysis of lung pathology using computed tomography, and bacterial load quantification in pulmonary lymph nodes (LN) by qPCR were carried out. Only HIMC vaccinated goats showed a significant reduction of lung lesions volume and mycobacterial DNA load in LN compared to unvaccinated controls. Both vaccinated groups showed also a significant reduction of the other pathological parameters, an improved clinical outcome and a higher proportion of IFN-γ-producing central memory T cells after vaccination. The results indicated that homologous vaccination of goats with HIMC induced enhanced protection against M. caprae challenge by reducing lung pathology and bacterial load compared to the heterologous vaccine (HIMB). Further large-scale trials are necessary to assess the efficacy of autovaccines under field conditions.

Cell-Mediated Immunological Biomarkers and Their Diagnostic Application in Livestock and Wildlife Infected With Mycobacterium bovis

Mycobacterium bovis has the largest host range of the Mycobacterium tuberculosis complex and infects domestic animal species, wildlife, and humans. The presence of global wildlife maintenance hosts complicates bovine tuberculosis (bTB) control efforts and further threatens livestock and wildlife-related industries. Thus, it is imperative that early and accurate detection of M. bovis in all affected animal species is achieved. Further, an improved understanding of the complex species-specific host immune responses to M. bovis could enable the development of diagnostic tests that not only identify infected animals but distinguish between infection and active disease. The primary bTB screening standard worldwide remains the tuberculin skin test (TST) that presents several test performance and logistical limitations. Hence additional tests are used, most commonly an interferon-gamma (IFN-γ) release assay (IGRA) that, similar to the TST, measures a cell-mediated immune (CMI) response to M. bovis. There are various cytokines and chemokines, in addition to IFN-γ, involved in the CMI component of host adaptive immunity. Due to the dominance of CMI-based responses to mycobacterial infection, cytokine and chemokine biomarkers have become a focus for diagnostic tests in livestock and wildlife. Therefore, this review describes the current understanding of host immune responses to M. bovis as it pertains to the development of diagnostic tools using CMI-based biomarkers in both gene expression and protein release assays, and their limitations. Although the study of CMI biomarkers has advanced fundamental understanding of the complex host-M. bovis interplay and bTB progression, resulting in development of several promising diagnostic assays, most of this research remains limited to cattle. Considering differences in host susceptibility, transmission and immune responses, and the wide variety of M. bovis-affected animal species, knowledge gaps continue to pose some of the biggest challenges to the improvement of M. bovis and bTB diagnosis.