Anti-Toxoplasma antibodies in Egyptian rheumatoid arthritis patients.

Objective: To assess seroprevalence of anti-Toxoplasma gondii antibodies; both IgG and IgM in Egyptian rheumatoid arthritis (RA) patients versus a non-RA group and to compare anti-Toxoplasma antibodies seroprevalence among RA patients receiving traditional treatment and RA patients treated with biologic drug.

Methods: 60 RA patients and 60 healthy controls were enrolled in the study. Patients were categorized into two groups: one group included 30 patients receiving disease modifying anti-rheumatic drugs (DMARDs), while the other group included 30 patients receiving biologic agent, infliximab, a TNF-α antagonist. Serum samples of all investigated persons were examined for anti-Toxoplasma antibodies. RA activity markers including rheumatoid factor, anti-cyclic citrullinated protein antibodies, C reactive protein, ESR in addition to disease activity score 28 (DAS28) of RA patients were also evaluated to explore their association with Toxoplasma seropositivity.

Results: Anti-Toxoplasma IgG antibodies were detected among 46/60 RA patients (76.7%) versus 29/60 controls (48.3%), (p = 0.001). Anti-Toxoplasma IgG titre was higher among RA group [median, (range) = 232.940 (8.949-653.242) IU/ml] than among controls [median, (range) = 68.820 (2.450-318.945) IU/ml], (p < 0.001). No difference was detected among RA patients either on traditional or biologic treatment regarding anti-Toxoplasma IgG antibodies. No positive anti-Toxoplasma IgM was detected. A positive correlation was detected between anti-Toxoplasma IgG titre and disease activity markers.

Conclusion: Higher seroprevalence of anti-Toxoplasma IgG antibodies among RA patients compared to controls reflects an association between latent Toxoplasma infection and RA. Our findings support previous studies and necessitate future large-scale studies to elucidate the exact role of Toxoplasma whether a trigger of autoimmunity in RA or an effect of immunosuppression.