gondiiand its hosts duringin vivoinfection will allow discovery of new drug targets active against bradyzoites and vaccines effective against multiple stages and strains

gondiiand its hosts duringin vivoinfection will allow discovery of new drug targets active against bradyzoites and vaccines effective against multiple stages and strains. == ACKNOWLEDGMENTS == We sincerely thank Jon Boyle and Will Olson for critical editing of this review. Work from this laboratory is supported by NIH (AI104697 and AI114277), the American Heart Connection (14GRNT20490023), and NIH National Research Support award T32 AI007414 (K. J. P. ). == REFERENCES ==. understood, viewing the interconnections between web host and parasite during acute and chronic infection may lead to better methods for long term treatment. The aim of this review is to provide an overview of what is known and unfamiliar about the complex relationship between the web host and parasite during the progression ofT. gondiiinfection, with the best goal of bridging these events. == INTRODUCTION == Toxoplasma gondiiis an obligate intracellular parasite that has been shown to infect a multitude of warm-blooded animals (1). While the asexual cycle can likely occur in any warm-blooded web host, theT. gondiisexual cycle only occurs in feline intestinal epithelial cells (2). Within intermediate hosts, two distinct asexual forms ofT. gondiiexist. During acute infection, the rapidly dividing tachyzoite disseminates throughout the web host until pressure from the immune system, and other unfamiliar factors, induce differentiation to the slower-growing encysted bradyzoite. Formation of cysts containing bradyzoites occurs within cells from the central nervous system and striated muscle (3). Bradyzoite cysts can persist intended for the lifetime of the web host and are infectious if consumed. T. gondiiinfection is typically asymptomatic but does present issues in the immunocompromised and in unborn fetuses when acquired congenitally. In humans, ingestion of undercooked meat containing bradyzoite cysts is considered the primary route of publicity toT. gondii(4, 5), but antibodies have been detected against oocyst stages, which suggests oocyst contamination of food and water is also a major supply of infection (4, 6). == Prevalence and Disease == T. gondiiis one of the most successful parasites globally, with upwards of 30% from the human population infected. T. gondiiinfection is usually asymptomatic in healthy individuals. Prevalence rates among humans vary greatly from country to country and range from 5 to 80% (7). This variation is based on differences in cultural practices as well as environmental conditions that prefer stability of oocysts in soil and water. Although prevalence rates in the United States are significantly lower than in most European countries (7), To. gondiiis considered the second leading cause of foodborne-related deaths in the United States (8). The high event ofT. gondiiinfection worldwide is attributed to its ability to be infectious in its sexual and asexual forms, establish a chronic infection in any warm-blooded creature, and remain infectious intended for the lifetime of that web host. WhileT. gondiiinfection in immunocompetent individuals is usually asymptomatic, flu-like symptoms can occur. If exceeded from mother to fetus, more extreme outcomes may occur, such as hydrocephaly and death (912). Infection withT. gondiiis more RBM45 detrimental in immunocompromised individuals, such as those with HIV, patients WF 11899A receiving organ transplants or undergoing cancer treatment, developing fetuses, and the elderly (1317). In these individuals, either primary infection withT. gondiior reactivation of latent bradyzoite cysts cannot be managed, resulting in encephalitis and pulmonary toxoplasmosis. == Sexual Cycle == The sexual cycle ofT. gondiiis restricted to the feline intestine. First, the ingested bradyzoites or oocysts are released by pepsin and acidity digestion in the stomach. Bradyzoites or sporozoites then invade the feline intestinal epithelium and differentiate into five morphologically distinct asexual types of schizonts, designated A through E (18) (Fig. 1). Within 2 days in the feline intestine, T. gondiiprogresses through almost all five stages of schizonts and evolves into merozoites, the 1st sexual stage. Merozoites undergo a limited proliferation of two to four doublings before they differentiate into macrogametes and microgametes. The macro- and microgametes fuse to produce diploid oocysts, which develop thick impermeable walls and they are shed in the feces (Fig. 1). Pet WF 11899A cats excrete between 2 and 20 million oocysts per day in their feces and shed the from 3 to 10 days postinfection. In ambient air and temperature, oocysts WF 11899A sporulate by undergoing mitosis and meiosis until they produce 8 haploid sporozoites encased within the oocyst wall. T. gondiioocysts are stable for over a year under a variety of environmental conditions and are most stable when stored in 2% sulfuric acidity (19, 20). == FIG 1 . ==.