Cytokine Expression and Haptoglobin Levels in Bovine Fetuses Spontaneously Aborted by Intracellular Infectious Agents and by Probable Infectious Etiology

Abstract

Intracellular pathogens such as Neospora caninum, Brucella abortus, and Bovine Viral Diarrhea Virus (BVDV) are major contributors to bovine abortions, yet many cases remain without a definitive etiological diagnosis despite inflammatory evidence. This study aimed to characterize the immune response in bovine fetuses aborted due to these intracellular agents, comparing them with fetuses showing inflammatory lesions of probable infectious origin and with negative controls. We analyzed cytokine expression (IFN-γ, TNFα, IL-4, IL-8, IL-12) and haptoglobin levels in mid- and late-gestation fetuses. Mid-gestation fetuses infected with intracellular agents exhibited elevated IFN-γ and IL-8 expressions, suggesting a Th1-type immune response, while late-gestation fetuses showed decreased of these cytokines, indicating a shift toward a Th2-type response. Probable infectious abortions at late gestation also showed downregulation of IFN-γ. No significant differences were observed in TNF-α and IL-12 expressions. Additionally, haptoglobin levels were lower in mid-gestation infected fetuses compared to controls. These findings highlight gestational age-dependent immune modulation in response to intracellular infections and suggest that other unidentified pathogens may contribute to abortions with inflammatory lesions but no confirmed etiology. This study enhances our understanding of fetal immune responses in bovine abortions and may support improved diagnostic approaches for reproductive losses in cattle.