Antibody levels correlate with detection of Trypanosoma cruzi DNA by sensitive polymerase chain reaction assays in seropositive blood donors and possible resolution of infection over time

Abstract

Background The clinical significance of anti-T. cruzi low-level reactive samples is incompletely understood. PCR-positive rates and antibody levels among seropositive blood donors in three countries are described. Methods Follow-up whole blood and plasma samples were collected from T. cruzi-seropositive donors from 2008-2010 in the US (n=195) and Honduras (n=58). Also 143 samples from Brazil in 1996-2002, originally positive by three serological assays, were available and paired with contemporary follow-up samples from these donors. All samples were retested with the FDA-approved Ortho ELISA. PCR assays were performed on coded sample panels by two laboratories (BSRI and ARC) that amplified kinetoplast minicircle DNA sequences of T. cruzi. Results PCR testing at BSRI yielded slightly higher overall sensitivity and specificity (33% and 98%) compared with the ARC lab (28% and 94%). Among seropositive donors, PCR-positive rates varied by country (p<0.0001) for the BSRI laboratory: Brazil (57%), Honduras (32%) and the US (14%). ELISA signal/cutoff (S/CO) ratios were significantly higher for PCR-positive compared to PCR-negative donors (p<0.05 for all comparisons). Additionally, PCR-negative Brazilian donors exhibited greater frequencies of antibody decline over time versus PCR-positive donors (p=0.003). Conclusion For all three countries, persistent DNA positivity correlated with higher ELISA S/CO values, suggesting that high-level seroreactivity reflects chronic parasitemia. The higher rate of PCR positivity for Brazilian donors was likely attributable to required reactivity on three assays available a decade ago. Significant S/CO declines in 10% of the PCR-negative Brazilian donors may indicate seroreversion following parasite clearance in the absence of treatment.

Inflammatory and cardiac biomarkers are differentially expressed in clinical stages of Chagas disease

“…Aliquots were frozen in Brazil at −20°C until shipped to the US REDS-II Central Laboratory (BSRI) on dry ice, followed by maintenance at −70°C. The target-capture (TC) T. cruzi real-time (RT) PCR assay used in this study [18] was developed based on the PCR method described by Virreira M et al[19] targeting kinetoplast minicircle T. cruzi DNA.…”

Electrocardiographic Abnormalities in Trypanosoma cruzi Seropositive and Seronegative Former Blood Donors

“…All donors reactive to both assays at the time of donation and counseling were considered eligible for this study. Follow-up samples from all enrolled subjects were retested for T. cruzi antibody under code at the REDS-II Central Laboratory in the US using an FDA-approved assay manufactured by Ortho Diagnostics [21]. All 483 control donors tested negative on their follow-up samples collected at the time of enrollment and clinical assessments for this study.…”

“…All 483 control donors tested negative on their follow-up samples collected at the time of enrollment and clinical assessments for this study. Of the 499 case donors who originally screened as seropositive at the time donation in 1998–2002, serum collected in 2008–2010 from 498 tested repeat reactive, while the samples from one donor tested just below the assay cutoff consistent with slowly progressive seroreversion [21].…”

Chagas disease research and development: Is there light at the end of the tunnel?

“…cruzi parasite diversity, the possibility of patients being infected with a mixed population and a lack of data showing that parasitaemia is representative of tissue parasitism are also problematic. An additional issue with PCR is that not all Chagas patients will be PCR positive; indeed, a study showed that depending on the region, between 20% and 60% of Chagas patients are PCR negative [44].…”