Novel insights into antioxidant status, gene expression, and immunohistochemistry in an animal model infected with camel-derived Trypanosoma evansi and Theileria annulata

Abstract

Background: Hemoprotozoan diseases, especially trypanosomosis and theileriosis, adversely affect the productivity, growth, and performance of camels. Regular sampling and investigation of camels are challenging due to several factors. Consequently, there is a lack of knowledge on camel parasite genotyping, cytokine production, and oxidative stress parameters during infection.

Methods: The present study investigated two critical blood protozoa infecting camels in Egypt, Trypanosoma evansi and Theileria annulata, using molecular methods, specifically 18S rRNA gene analysis. Following molecular confirmation, experimental infections were induced in Swiss albino mice to assess the expression of immune response genes and oxidative stress parameters. The study further explored the correlation between histopathological alterations and inflammatory reactions in the kidney, spleen, and liver of infected mice, alongside the immunohistochemical expression of caspase-3, proliferating cell nuclear antigen (PCNA), and tumor necrosis factor (TNF).

Results: Trypanosoma evansi and T. annulata isolated from naturally infected camels were molecularly identified and deposited in GenBank under accession numbers OR116429 and OR103130, respectively. Infection with T. evansi and T. annulata caused significant adverse effects on the immune condition of infected mice, increasing the pathogenicity of the infection. This was evidenced by a significant increase in oxidative stress parameter levels in both naturally infected camels and experimentally infected mice compared to healthy controls. Furthermore, the expression of immune response genes was significantly elevated in infected mice. Immunohistochemistry analysis showed a pronounced upregulation of caspase-3, PCNA, and TNF in the infected groups relative to the control group. These findings are the first to be reported in Egypt.

Conclusions: This study successfully identified and genotyped two economically important blood protozoa, T. evansi and T. annulata, from camels in Egypt. Additionally, the experimental animal model provided valuable insights into the immune response, oxidative stress, and histopathological changes induced by these parasites, demonstrating comparable results to naturally infected camels. These findings highlight the potential of this model to study parasite-host interactions and immune responses, contributing to a better understanding of the pathogenic mechanisms of T. evansi and T. annulata infections. This model may be useful for future studies focused on disease control and therapeutic interventions.

Keywords: Theileria annulata; Trypanosoma evansi; Camels; Gene expression; Immunohistochemistry; Stress markers.

Fig. 1

A Oxidative stress biomarkers (CAT, GPX, and SOD) and B cytokines expression (IFNγ, TGF-1β, and IL-1β) in the blood of apparently healthy and naturally infected camels

Fig. 2

A Blood oxidative stress markers (CAT, GPX, and SOD), B cytokines expression (IFNγ, TGF-1β, and IL-1β) in the liver, C spleen, and D kidney of control and experimentally infected mice with T. evansi and T. annulata

Fig. 3

A Photomicrographs of liver, kidney, and spleen stained by H&E. B, C, and D Histological damage scores in liver, kidney, and spleen tissues, respectively. Data are presented as median ± SD, applying a t-test followed by the Mann–Whitney test (*P ≤ 0.05). Notable features include inflammatory cell infiltration (arrowhead), coagulative necrosis (blue arrow), vacuolation of hepatocellular cytoplasm (curved blue arrow), and extramedullary megakaryopoiesis (curved black arrow)

Fig. 4

A Photomicrographs of liver, kidney, and spleen stained with caspase-3 immunohistochemistry. B, C, and D Immunohistochemical analysis of the area percentage of caspase-3 expression in the liver, kidney, and spleen, respectively. Data are expressed as mean ± SD (*P ≤ 0.05)

Fig. 5

A Photomicrographs of liver, kidney, and spleen stained with TNF immunohistochemistry. B, C, and D Immunohistochemical analysis of the area percentage of TNF expression in the liver, kidney, and spleen, respectively. Data are expressed as mean ± SD (*P ≤ 0.05)

Fig. 6

A Photomicrographs of liver, kidney, and spleen stained with PCNA immunohistochemistry. B, C, and D Immunohistochemical analysis of the area percentage of PCNA expression in the liver, kidney, and spleen, respectively. Data are expressed as mean ± SD (*P ≤ 0.05)