Toxoplasma vaccines: appropriate end points and sample size in future human clinical trials.

Author for correspondence Department of Infectious Diseases, Aarhus University Hospital, Skejby Aarhus, Denmark Tel.: +45 8949 8307 Fax: +45 8949 8360 [email protected] Toxoplasma eye disease is a huge problem in certain parts of the world, especially South America and Africa [1,2]. In these regions, infection with Toxoplasma gondii is mostly a poverty-related disease where populations depending on surface water and fresh meat are at a particularly high risk [3]. T. gondii eye disease is prevalent in tropical Africa, and the data available point to nonarchetypal genotypes dominating in sub-Saharan Africa [4]. The very high prevalence in Brazil can be partly explained by more virulent T. gondii genotypes [5], but the infectious pressure may also be more pronounced, especially by a high T. gondii infection rate in meat [6]. Current findings indicate that most strains from Brazil do not fit the clonal pattern seen in North America [7]. Other studies suggest that clonal lineages II and III predominate in Africa as in Europe and North America [8,9], and most infections are acquired through food or water in these areas [10,11]. Control of T. gondii infections have not been realized by public health measures, ensuring Toxoplasma-safe water and meat. There is a lack of efficient drugs and no new drugs are on the horizon. Most patients acquire the infection during childhood or early adulthood and there is therefore a possibility to immunize people before infection. Much work has been done on developing vaccines against T. gondii [12], but Phase I or II trials in humans are not imminent, as T. gondii is not perceived as a large public health problem in industrialized countries, such as the USA and the EU, where congenital toxoplasmosis, but not eye disease, is a concern. Monitoring and treatment of pregnant women and newborns is the current medical practice in these countries [13].