Toxoplasma gondii Serostatus Is Not Associated With Impaired Long Term Survival after Heart Transplantation

Until now, two studies investigated whether the long-term survival after heart transplantation is affected by the Toxoplasma serostatus of the recipient and the donor (1, 2). These studies, however, yielded conflicting results as to the recipient serostatus. Arora et al. reported that a Toxoplasma seropositive status in heart transplant recipients was associated with an increased risk of all-cause mortality as well as risk of death by cardiac allograft vasculopathy and Doesch et al. reported that a Toxoplasma seronegative status was associated with an increased mortality risk (1, 2). In both studies, no association of donor serostatus and mortality was found. Toxoplasma gondii is an obligate intracellular protozoan parasite with a worldwide distribution that can invade and replicate in almost all nucleated cells of warm-blooded mammals. After the primary acute infection, the parasite remains in the body in a quiescent state by the formation of tissue cysts in predominantly muscle and brain tissue. Therefore, toxoplasmosis is a lifelong infection and the prevalence of human T. gondii infections thus increases with age. Its prevalence is reported to be more than 50% in many parts of the world (3). In immunocompetent individuals, the infection is usually asymptomatic, although cases of severe disease due to unusual T. gondii genotypes from South and Central America have been reported (4). In immunocompromised patients, however, toxoplasmosis can be a severe disease (3). Solid-organ transplant recipients are immunocompromised due to the required high dose of immunosuppressive medication. Heart transplant recipients are known to be at risk for toxoplasmosis, especially when recipients are seronegative (and thus naive for T. gondii) and receive a heart transplant, containing tissue cysts, from a T. gondii–infected donor (5). In these cases, prophylactic treatment is indicated to prevent toxoplasmic myocarditis and fatal disseminated toxoplasmosis (5, 6). Also, antibiotic drugs, administered prophylactically to Toxoplasma mismatched recipients, could have a direct or indirect immunomodulatory effect and could negatively influence patient outcome by their side effects (7). Cardiac allograft vasculopathy, a process in which chronic inflammation and immune activation play an important role, is a major cause of death after heart transplantation (8, 9). A T. gondii infection might influence the host immunologic status and thereby affect the risk for cardiac allograft vasculopathy. Therefore, the effects of a T. gondii infection on the survival after heart transplantation have been subject of study. Because of the earlier conflicting results of studies, which involved rather small numbers of patients and a limited follow-up duration, we performed a study on our whole population of heart transplant recipients to evaluate the effects of a T. gondii infection in the recipient and/or the donor on survival after heart transplantation.