Anti-Toxoplasma antibodies in Egyptian rheumatoid arthritis patients

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.

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.

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.

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.