Detection of Immunoglobulin G Antibodies toNeospora caninumin Humans: High Seropositivity Rates in Patients Who Are Infected by Human Immunodeficiency Virus or Have Neurological Disorders

Abstract

Considering that little is known about the epidemiology ofNeospora caninuminfection in humans, particularly in populations with highToxoplasma gondiiinfection rates, the present study aimed to investigate the presence of antibodies toN. caninuminT. gondii-seropositive and -seronegative individuals. A total of 256 serum samples divided into four groups (61 samples from human immunodeficiency virus [HIV]-positive patients, 50 samples from patients with neurological disorders, 91 samples from newborns, and 54 samples from healthy subjects) were assessed forN. caninumandT. gondiiserologies by indirect fluorescent-antibody test, enzyme-linked immunosorbent assay, and immunoblotting (IB). Immunoglobulin G antibodies toN. caninumwere predominantly detected in HIV-infected patients (38%) and patients with neurological disorders (18%), while newborns and healthy subjects showed lower seropositivity rates (5% and 6%, respectively). Seropositivity toN. caninumwas significantly associated with seropositivity toT. gondiiin both HIV-infected patients and patients with neurological disorders. Seroreactivity toN. caninumwas confirmed by IB, with positive sera predominantly recognizing the 29-kDa antigen ofN. caninum. The results of this study indicate the presence ofN. caninuminfection or exposure in humans, particularly in HIV-infected patients or patients with neurological disorders, who could have opportunistic and concurrent infections withT. gondii. These findings may bring a new concern for the unstable clinical health of HIV-infected patients and the actual role ofN. caninuminfection in immunocompromised patients.