High variation in immune responses and parasite phenotypes in naturally acquired Trypanosoma cruzi infection in a captive non-human primate breeding colony in Texas, USA

Abstract

Trypanosoma cruzi, the causative agent of human Chagas disease, is endemic to the southern region of the United States where it routinely infects many host species. The indoor/outdoor housing configuration used in many non-human primate research and breeding facilities in the southern of the USA provides the opportunity for infection by T. cruzi and thus provides source material for in-depth investigation of host and parasite dynamics in a natural host species under highly controlled and restricted conditions. For cynomolgus macaques housed at such a facility, we used a combination of serial blood quantitative PCR (qPCR) and hemoculture to confirm infection in >92% of seropositive animals, although each method alone failed to detect infection in >20% of cases. Parasite isolates obtained from 43 of the 64 seropositive macaques were of 2 broad genetic types (discrete typing units, (DTU’s) I and IV); both within and between these DTU groupings, isolates displayed a wide variation in growth characteristics and virulence, elicited host immune responses, and susceptibility to drug treatment in a mouse model. Likewise, the macaques displayed a diversity in T cell and antibody response profiles that rarely correlated with parasite DTU type, minimum length of infection, or age of the primate. This study reveals the complexity of infection dynamics, parasite phenotypes, and immune response patterns that can occur in a primate group, despite being housed in a uniform environment at a single location, and the limited time period over which the T. cruzi infections were established.

Discovery of an orally active benzoxaborole prodrug effective in the treatment of Chagas disease in non-human primates

“…All animals in the trial were positive by PCR for T. cruzi DNA in blood at one or more time points pre-treatment and were seropositive for anti- T. cruzi antibodies by standard facility screening tests and via our Luminex-based multiplex serological assay 16 , 17 (Extended Data Figs. 2 and 3, and Fig.…”

Prophylactic low-dose, bi-weekly benznidazole treatment fails to prevent Trypanosoma cruzi infection in dogs under intense transmission pressure

“…Roughly half (29/53; 54.7%) of the dogs with detectable (generally robust) serological responses also had T. cruzi DNA in their blood as determined by qPCR. It is notable that, as in other species [24,[28][29][30][31], the pattern of antigen specificity of antibody responses in these subjects varied extensively, although the antigen in lane 8, a polyubiquitin protein, appeared to be the most reliable. A fraction of the screened dogs (n = 14; 11.1%) were seronegative by Luminex and other assays but had a weak signal in the blood PCR assay that was measurable, but above our standard cutoff for determining infection (Ct < 35.0; Fig 2C and Table S1).…”

“…Additionally, serologic tests may miss very recent infections. A total of 126 dogs of previously undetermined infection status were screened using a Luminex-based assay previously employed for detection and monitoring T. cruzi infection in humans [28][29][30] and other species [24,31], a commercial Stat-Pak test (ChemBio, NY) that is validated for humans but commonly used for research purposes in dogs [32,33], and by blood PCR. Figure 2A displays dogs considered to be infection-negative based upon the Luminex assay and confirmed in most cases by Stat-Pak and indirect fluorescent antibody (IFA) (Texas A&M Veterinary Medical Diagnostic Laboratory, College Station, TX; [32]) assays (Supplemental Table 1; n=57; 45.2% of total screened).…”

Phenotypic and Functional Signatures of Peripheral Blood and Spleen Compartments of Cynomolgus Macaques Infected With T. cruzi: Associations With Cardiac Histopathological Characteristics

“…In fact, the study of natural or experimental infectious diseases in non-human primates has enabled the development of improved vaccines, diagnostic tools, and therapeutic strategies for human diseases (Gardner and Luciw, 2008). Cynomolgus macaques have been suggested as useful models for studies on Chagas disease, based on PCR assessment of T. cruzi in cardiac tissue, histopathological features, and electrocardiograms (Zabalgoitia et al, 2003;Williams et al, 2009;Padilla et al, 2021), as well as phenotypic and functional features of immune response that these animals share in common with humans after natural infection with T. cruzi (Sathler-Avelar et al, 2016;Vitelli-Avelar et al, 2017;Padilla et al, 2021). Aiming at further understanding the immune response of cynomolgus macaques that were naturally infected with T. cruzi, the present investigation enabled a detailed immunophenotypic and functional analysis of peripheral blood and spleen cells, and identification of their unique and shared features in relation to cardiac histopathological lesion status.…”