Enhanced Production of IL-10 in PCR-Positive Dogs Infected with E. canis and A. phagocytophilum Facilitate Specific Immune Responses

Abstract

Infection of dogs with the tick-borne rickettsiae Ehrlichia and Anaplasma provokes an immune response mediating the pathology and bacterial resistance. IL-10 is the main anti-inflammatory cytokine and plays a multifaceted role in host protection. The study aimed to investigate circulating IL-10 in 32 dogs naturally infected with A. phagocytophilum and E. canis, identified by PCR positivity, and 33 PCR-negative animals which tested positive for antibodies against these pathogens, as well as 22 healthy animals. The highest quantity of IL-10, measured by ELISA, was observed among dogs positive simultaneously for anti-E. canis and anti-A. phagocytophilum IgG antibodies, followed by dogs positive for anti-E. canis only. The concentration of IL-10 in PCR-positive dogs was almost three and a half times higher than that measured in the control group (77.09 ± 23.61 pg./mL vs. 21.55 ± 4.61 pg./mL; p = 0.0015) and five times higher than the concentration of interleukin in PCR-negative animals (77.09 ± 23.61 pg./mL vs. 14.86 ± 3.01 pg./mL; p = 0.000016). The highest level of IL-10 was observed in PCR-positive dogs with mixed infection (120.54 ± 44.18), followed by the level in PCR-positive dogs for E. canis only (78.81 ± 16.92). The lowest level of IL-10 was observed in PCR-positive dogs for A. phagocytophilum only (56.32 ± 12.68). We may suggest that infection with E. canis and A. phagocytophilum stimulates the IL-10 production in dogs, which may facilitate specific antibody responses.