Genetic polymorphism of Trypanosoma cruzi bloodstream populations in adult chronic indeterminate Chagas disease patients from the E1224 clinical trial.

BACKGROUND: The role that the genetic diversity of natural Trypanosoma cruzi populations plays in response to trypanocidal treatment of chronic Chagas disease (CD) patients remains to be understood. We analysed the genetic polymorphisms of parasite bloodstream populations infecting chronic CD patients enrolled in the E1224 clinical trial. METHODS: A total of 506 baseline and post-treatment follow-up samples from 188 patients were analysed. T. cruzi satellite DNA (satDNA) was amplified and sequenced using cruzi1/cruzi2 primers, and samples with TcI/III, TcII, TcIV or hybrid satDNA sequences were identified. Minicircle signatures were obtained after kinetoplast DNA amplification using 121/122 primers and restriction enzyme digestion. Genetic distances between baseline and post-treatment minicircle signatures were estimated using the Jaccard coefficient. RESULTS: At baseline, 74.3% TcII, 17.9% hybrid and 7.8% TcI/III satDNA sequences were found, whereas at the end of follow-up the distribution was 55.2% TcII, 35.2% hybrid and 9.5% TcI/III. The placebo arm was the treatment group with the highest variation of satDNA sequences between baseline and post-treatment follow-up. Genetic distances between baseline and post-treatment minicircle signatures were similar among all treatment arms. No association between minicircle signature variability and satDNA type distribution was found. CONCLUSIONS: Genetic variability of T. cruzi bloodstream populations during post-treatment follow-up did not differ from that observed during chronic infection in the absence of treatment, suggesting that there were no selection events of E1224-resistant parasite populations. This is the first report documenting the genetic polymorphism of natural T. cruzi populations in chronic patients in the context of clinical trials with trypanocidal drugs.

IgE antibodies against Trypanosoma cruzi arginine kinase in patients with chronic Chagas disease.

Arginine kinase (AK) is an enzyme present in various invertebrates, as well as in some trypanosomatids such as T. cruzi, the etiological agent that causes Chagas disease. In invertebrates, this protein acts as an allergen inducing an IgE-type humoral immune response. Since AK is a highly conserved protein, we decided to study whether patients with chronic Chagas disease (CCD) produce specific antibodies against T. cruzi AK (TcAK). Plasma from patients with CCD, with and without cardiac alterations and non-infected individuals were evaluated for the presence of anti-TcAK IgG and IgE antibodies by ELISA, including detection of specific IgG subclasses. Our results showed that the levels of specific anti-TcAK IgG and IgE were different between infected and non-infected individuals, but comparable between those with different clinical manifestations. Interestingly, anti-TcAK IgG4 antibodies associated with IgE-mediated allergenic processes were also increased in CCD patients. Finally, we found that several of the predicted B cell epitopes in TcAK matched allergenic peptides previously described for its homologues in other organisms. Our results revealed for the first time a parasite's specific IgE antibody target and suggest that TcAK could contribute to delineate an inefficient B cell response by prompting a bias towards a Th2 profile. These findings also shed light on a potential allergenic response in the context of T. cruzi infection.

Different genotypes of Trypanosoma cruzi produce distinctive placental environment genetic response in chronic experimental infection.

Congenital infection of Trypanosoma cruzi allows transmission of this parasite through generations. Despite the problematic that this entails, little is known about the placenta environment genetic response produced against infection. We performed functional genomics by microarray analysis in C57Bl/6J mice comparing placentas from uninfected animals and from animals infected with two different T. cruzi strains: K98, a clone of the non-lethal myotropic CA-I strain (TcI), and VD (TcVI), isolated from a human case of congenital infection. Analysis of networks by GeneMANIA of differentially expressed genes showed that "Secretory Granule" was a pathway down-regulated in both infected groups, whereas "Innate Immune Response" and "Response to Interferon-gamma" were pathways up-regulated in VD infection but not in K98. Applying another approach, the GSEA algorithm that detects small changes in predetermined gene sets, we found that metabolic processes, transcription and macromolecular transport were down-regulated in infected placentas environment and some pathways related to cascade signaling had opposite regulation: over-represented in VD and down-regulated in K98 group. We also have found a stronger tropism to the placental organ by VD strain, by detection of parasite DNA and RNA, suggesting living parasites. Our study is the first one to describe in a murine model the genetic response of placental environment to T. cruzi infection and suggests the development of a strong immune response, parasite genotype-dependent, to the detriment of cellular metabolism, which may contribute to control infection preventing the risk of congenital transmission.