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It is well known that toxoplasmosis can be life threatening to immunocompromised individuals such as AIDS and organ transplantation patients. Glucocorticoids (GCs) are widely used in the clinic for the treatment of autoimmune diseases and organ transplantation resulting in acute toxoplasmosis in these patients. However, the interaction and mechanism between the development of acute toxoplasmosis and GC therapy are still unknown. The aims of this study were to investigate the infection of Toxoplasma gondii in the peritoneal macrophages of rats treated with glucocorticoids. Our results showed that the growth rate of T. gondii RH strain was significantly increased in the peritoneal macrophages of rats treated with glucocorticoids in vivo. For instance, 242 (±16) tachyzoites were found in 100 macrophages from the rats treated with methylprednisolone (MP), while only 16 (±4) tachyzoites were counted in the macrophages from the non-treated control rats 24 h after infection ( P < 0.01). We also demonstrated that a significant inhibition of nitric oxide (NO) production was detected in the macrophages collected from the rats post-treated with GCs with 12.90 μM (±0.99 μM) of nitrite production from the rats treated with MP, while 30.85 μM (±1.62 μM) was found in the non-treated control rats 36 h after incubation ( P < 0.01). Furthermore, glucocorticoids could significantly inhibit the expression of inducible nitric oxide synthase mRNA and its protein in the rat peritoneal macrophages. Our results strongly indicate that the decrease of NO in the rat peritoneal macrophages is closely linked to the cause of acute toxoplasmosis in the host. Additionally, there was a significant increase in the number of cysts produced by the naturally cyst forming, T. gondii Prugniaud strain with an average of 2,795 (±422) cysts of the parasite being detected in the brains of the rats treated with dexamethasone, while only 1,356 (±490) cysts were found in the non-treated control animals ( P < 0.01). As rats and humans are both naturally resistant to T. gondii infection, these novel data could lead to a better understanding of the development of acute toxoplasmosis during glucocorticoid therapy in humans. [ABSTRACT FROM AUTHOR]

Rats are naturally resistant to Toxoplasma gondii infection, particularly the RH strain, while mice are not. Previous studies have demonstrated that inducible nitric oxide synthase (iNOS) and arginase-1 of rodent peritoneal macrophages are linked to the mechanism of resistance. As an increasing number of studies on human and animal infections are showing that pulmonary toxoplasmosis is one of the most severe clinical signs from T. gondii infection, we are interested to know whether T. gondii infection in alveolar macrophages of rats is also linked to the levels of iNOS and arginase-1 activity. Our results demonstrate that T. gondii could grow and proliferate in rat alveolar macrophages, both in vitro and in vivo, at levels higher than resistant rat peritoneal macrophages and at comparable levels to sensitive mouse peritoneal macrophages. Lower activity and expression levels of iNOS and higher activity and expression levels of arginase-1 in rat alveolar macrophages were found to be linked to the susceptibility of T. gondii infection in these cells. These novel findings could aid a better understanding of the pathogenesis of clinical pulmonary toxoplasmosis in humans and domestic animals. [ABSTRACT FROM AUTHOR]

Abstract: Trypanosoma lewisi has widely been considered as a non-pathogenic rat trypanosome. However, more and more cases of humans infected with T. lewisi have been reported around the world, indicating that it can infect humans in some undetermined circumstances. Quick and sensitive diagnosis of infection by T. lewisi is important for both treatment of patients and epidemiological studies of this parasite. In this paper, three methods i.e. wet blood smear (diagnosis by microscopy), PCR and LAMP were used to detect T. lewisi from 238 wild rats (Rattus norvegicus) collected from the field in Huadu, Guangdong province, China. Infection rates of these samples detected by the 3 methods was 6.7% (16/238), 12.6% (30/238), and 18.9% (45/238), respectively. LAMP could detect all samples shown positive by microscopical observation of wet smear and by single PCR indicating good potential for application in the detection of T. lewisi. So far as we know, this is the first report of the LAMP method being used to detect T. lewisi in wild rats. The specific T. lewisi LAMP primers were able to amplify the target fragment from the genomic DNA of 19 T. lewisi strains isolated from Huadu, Guangdong province (n =16), Changchun, Jilin province of China (n =1) and from Thailand (n =2). Based on the analyses of ITS1 (internal transcribed spacer 1) and ITS2 sequences, these 19 strains show a very close genetic relationship with over 96–97% similarity to the other corresponding sequences of T. lewisi published in Genbank. Phylogenetic trees of the species in the subgenus Herpetosoma were constructed, based on the ITS1 and ITS2 sequences, and these results also indicate that they are closely related and in the same clade. [Copyright &y& Elsevier]