Anti-IL-10 antibody reduces Toxoplasma gondii brain cysts but increases tissue damage in mice

Chronic Toxoplasma gondii infection persists lifelong by balancing protective T helper type 1 (Th1) immunity with regulatory pathways that prevent immunopathology. Interleukin-10 (IL-10) is a key proposed suppressor of anti-parasite immunity, yet its precise functional contribution during chronic toxoplasmosis remains incompletely defined. Understanding IL-10's role is crucial for developing strategies that effectively control the parasite without inducing excessive host tissue damage, a significant challenge in managing this widespread parasitic infection.

Researchers investigated IL-10's immunoregulatory role during experimental T. gondii infection in 45 female Swiss albino mice. Mice were divided into three groups: non-infected, T. gondii-infected, and T. gondii-infected treated with anti-IL-10 monoclonal antibody. Infection was induced intraperitoneally with 10 ME49 cysts. The anti-IL-10 mAb treatment began one-week post-infection. Mice were sacrificed at 14, 28, and 42 days post-infection to assess brain cyst kinetics, liver and brain histopathology, and measure serum IFN-γ, TNF-α, IL-10, and IgM levels using ELISA.

Infection with T. gondii induced robust elevations of IFN-γ and TNF-α, confirming a dominant Th1 response essential for early parasite control. Concurrently, IL-10 levels increased, indicating activation of a compensatory regulatory axis. IL-10 neutralization dramatically reshaped disease outcomes: anti-IL-10-treated mice exhibited significantly reduced cerebral cyst burdens and heightened IgM levels, accompanied by pronounced amplification of IFN-γ and TNF-α responses. Network analysis revealed strong positive coupling between IFN-γ and TNF-α, while IL-10 displayed marked negative correlations with both cytokines, identifying IL-10 as a master suppressor of inflammatory immunity. However, IL-10 blockades resulted in severe hepatic and neural tissue damage, demonstrating the cost of unrestrained inflammation. This highlights IL-10's crucial role in mediating a delicate balance between parasite control and host protection. The study did not provide specific numerical percentages or p-values for these findings in the abstract, but emphasized the 'significantly reduced' and 'pronounced amplification' effects.

IL-10 neutralization dramatically reshaped disease outcomes: anti-IL-10-treated mice exhibited significantly reduced cerebral cyst burdens and heightened IgM levels, accompanied by pronounced amplification of IFN-γ and TNF-α response.