Phenotypic, functional and serological aspects of genotypic-specific immune response of experimental T. cruzi infection

Coinfection by multiple Trypanosoma cruzi clones: a new perspective on host-parasite relationship with consequences for pathogenesis and management of Chagas disease

SUMMARYChagas disease (CD) is caused by the protozoan parasite Trypanosoma cruzi (Tc), infecting 6-7 million people. It is transmitted by insect vectors, orally, through infected tissues, or congenitally. Tc infection can progress toward chronic cardiac and/or digestive severe and fatal CD in 20%-40% of patients. Tc exhibits an important genetic and phenotypic intraspecies diversity and a preponderant clonal population structure. The impact of multiclonal coinfections has been little studied in CD patients. Relationships between the currently used discrete typing unit (DTU)-based classification of Tc lineages and the occurrence of the different clinical forms of CD, its congenital transmission, as well as the efficacy of trypanocidal molecules (benznidazole and nifurtimox) could not be established. In this review, we revisit the different aspects of Tc diversity and analyze the impact of infections with multiple clones and their variants on the dynamic and pathogenesis of CD and its maternal-fetal transmission. We propose to call "cruziome" all the Tc clones and their variants infecting a given host and provide strong evidence that (i) multiclonal Tc infections are likely the rule rather than the exception; (ii) each "cruziome" is associated with a unique combination of virulence factors, tissular tropisms, and host immune responses; (iii) accordingly, some particularly harmful "cruziomes" likely trigger the occurrence and progression of CD and might also favor the congenital transmission of parasites. We propose that our concept of "cruziome" should be taken into consideration because of its practical consequences in epidemiological studies, laboratory diagnosis, clinical management, and treatment of CD.

Dissimilar Trypanosoma cruzi genotype-specific serological profile assessed by Chagas-Flow ATE IgG1 upon benznidazole etiological treatment of chronic Chagas disease

The present study aimed to verify the impact of etiological treatment on the genotype-specific serological diagnosis of chronic Chagas disease patients (CH), using the Chagas-Flow ATE IgG1 methodology. For this purpose, a total of 92 serum samples from CH, categorized as Not Treated (NT, n = 32) and Benznidazole-Treated (Bz-T, n = 60), were tested at Study Baseline and 5Years Follow-up. At Study Baseline, all patients have the diagnosis of Chagas disease confirmed by Chagas-Flow ATE IgG1, using the set of attributes ("antigen/serum dilution/cut-off"; "EVI/250/30%"). The genotype-specific serodiagnosis at Study Baseline demonstrated that 96% of patients (44/46) presented a serological profile compatible with TcII genotype infection. At 5Years Follow-up monitoring, NT and Bz-T presented no changes in anti-EVI IgG1 reactivity. However, significant differences were detected in the genotype-specific IgG1 reactivity for Bz-T. The most outstanding shift comprised the anti-amastigote TcVI/(AVI), anti-amastigote TcII/(AII) and anti-epimastigote TcVI/(EVI) reactivities. Regardless no changes in the genotype-specific serology of NT (TcI = 6%; TcII = 94%), distinct T. cruzi genotype-specific sero-classification was detected for Bz-T samples at 5Years Follow-up (TcII = 100%) as compared to Baseline (TcII = 97%; TcVI = 3%). The anti-trypomastigote TcI/(TI) was the attribute accountable for the change in genotype-specific sero-classification. In conclusion, our findings of dissimilar T. cruzi genotype-specific serology upon Bz-treatment re-emphasize the relevance of accomplishing the genotype-specific serodiagnosis during clinical pos-therapeutic management of chronic Chagas disease patients.

New insights into Trypanosoma cruzi genetic diversity, and its influence on parasite biology and clinical outcomes

Chagas disease, caused by Trypanosoma cruzi, remains a serious public health problem worldwide. The parasite was subdivided into six distinct genetic groups, called "discrete typing units" (DTUs), from TcI to TcVI. Several studies have indicated that the heterogeneity of T. cruzi species directly affects the diversity of clinical manifestations of Chagas disease, control, diagnosis performance, and susceptibility to treatment. Thus, this review aims to describe how T. cruzi genetic diversity influences the biology of the parasite and/or clinical parameters in humans. Regarding the geographic dispersion of T. cruzi, evident differences were observed in the distribution of DTUs in distinct areas. For example, TcII is the main DTU detected in Brazilian patients from the central and southeastern regions, where there are also registers of TcVI as a secondary T. cruzi DTU. An important aspect observed in previous studies is that the genetic variability of T. cruzi can impact parasite infectivity, reproduction, and differentiation in the vectors. It has been proposed that T. cruzi DTU influences the host immune response and affects disease progression. Genetic aspects of the parasite play an important role in determining which host tissues will be infected, thus heavily influencing Chagas disease's pathogenesis. Several teams have investigated the correlation between T. cruzi DTU and the reactivation of Chagas disease. In agreement with these data, it is reasonable to suppose that the immunological condition of the patient, whether or not associated with the reactivation of the T. cruzi infection and the parasite strain, may have an important role in the pathogenesis of Chagas disease. In this context, understanding the genetics of T. cruzi and its biological and clinical implications will provide new knowledge that may contribute to additional strategies in the diagnosis and clinical outcome follow-up of patients with Chagas disease, in addition to the reactivation of immunocompromised patients infected with T. cruzi.

Antigenic diversity of MASP gene family of Trypanosoma cruzi

Trypanosoma cruzi, the etiological agent of Chagas disease (CD), is a heterogeneous species with high genetic and phenotypic diversity. MASP is the second largest multigene family of T. cruzi. The high degree of polymorphism of the family associated with its location at the surface of infective forms of T. cruzi suggests that MASP participates in mechanisms of host-parasite interaction. In this work, MASP members were divided into 7 subgroups based on protein sequence similarity, and one representative member from each subgroup was chosen to be expressed recombinantly. Immunogenicity of recombinant MASP proteins (rMASP) was investigated using different sera panels from T. cruzi infected mice. To mimic a natural condition in which different MASP members are expressed at the same time in the parasite population, a multiplex bead-based flow cytometry assay was also standardized. Results showed that rMASPs are poorly recognized by sera from mice infected with Colombiana strain, whereas sera from mice infected with CL Brener and Y display high reactivity against the majority of rMASPs tested. Flow cytometry showed that MASP recognition profile changes 10 days after infection. Also, multiplex assay suggests that MASP M1 and M2 are more immunogenic than the other MASP members evaluated that may play an immunodominant role during infection.