Up-Converting Phosphor Technology-Based Lateral Flow Assay for Detection of Schistosoma Circulating Anodic Antigen in Serum▿

Schistosoma sp. circular anodic antigen (CAA) serum concentrations reflect actual worm burden in a patient and are a valuable tool for population screening and epidemiological research. However, for the diagnosis of individual imported schistosomiasis cases, the current enzyme-linked immunosorbent assay (ELISA) lacks sensitivity and robustness. Therefore, a lateral flow (LF) assay was developed to test CAA in serum for individual diagnosis of imported active schistosome infections. Application of fluorescent submicron-sized up-converting phosphor technology (UPT) reporter particles increased analytical sensitivity compared to that of the standard ELISA method. Evaluation of the UPT-LF test with a selection of 40 characterized epidemiologic samples indicated a good correlation between signal intensity and infection intensity. Subsequently, the UPT-LF assay was applied to 166 serum samples of Dutch residents (immigrants and travelers) suspected of schistosomiasis, a case in which group routine antibody detection frequently fails straightforward diagnosis. The UPT-LF assay identified 36 CAA-positive samples, compared to 15 detected by CAA-ELISA. In conclusion, the UPT-LF assay is a low-complexity test with higher sensitivity than the CAA-ELISA, well suited for laboratory diagnosis of individual active Schistosoma infections

Evaluation of banked urine samples for the detection of circulating anodic and cathodic antigens in Schistosoma mekongi and S. japonicum infections : a proof-of-concept study

In Asia, Schistosoma japonicum is the predominant schistosome species, while Schistosoma mekongi is confined to limited foci in Cambodia and Lao People's Democratic Republic. While the People's Republic of China has been successful in controlling schistosomiasis, the disease remains a major public health issue in other areas. In order to prioritise intervention areas, not only accurate diagnosis is important but also other factors, such as practicality, time-efficiency and cost-effectiveness, since they strongly influence the success of control programmes. To evaluate the highly specific urine-based assays for the schistosome circulating cathodic antigen (CCA) and the circulating anodic antigen (CAA), banked urine samples from Cambodia (n=106) and the Philippines (n=43) were examined by the upconverted phosphor lateral flow (UCP-LF) CAA assay and the point-of-care (POC)-CCA urine assay. Based on 250μl urine samples, UCP-LF CAA sensitivity outcomes surpassed a single stool examination by the Kato-Katz technique. The banked urine samples in the current study did not allow the evaluation of larger volumes, which conceivably should deliver considerably higher readings. The sensitivity of a single urine POC-CCA was in the same order as that of a single Kato-Katz thick smear examination, while the sensitivity approached that of triplicate Kato-Katz when a combination of both CAA and CCA assays was used. The promising results from the current proof-of-concept study call for larger investigations that will determine the accuracy of the urine-based CCA and CAA assays for S. mekongi and S. japonicum diagnosis

Latent class analysis to evaluate performance of point-of-care CCA for low-intensity Schistosoma mansoni infections in Burundi

Abstract Background Kato-Katz examination of stool smears is the field-standard method for detecting Schistosoma mansoni infection. However, Kato-Katz misses many active infections, especially of light intensity. Point-of-care circulating cathodic antigen (CCA) is an alternative field diagnostic that is more sensitive than Kato-Katz when intensity is low, but interpretation of CCA-trace results is unclear. To evaluate trace results, we tested urine and stool specimens from 398 pupils from eight schools in Burundi using four approaches: two in Burundi and two in a laboratory in Leiden, the Netherlands. In Burundi, we used Kato-Katz and point-of-care CCA (CCAB). In Leiden, we repeated the CCA (CCAL) and also used Up-Converting Phosphor Circulating Anodic Antigen (CAA). Methods We applied Bayesian latent class analyses (LCA), first considering CCA traces as negative and then as positive. We used the LCA output to estimate validity of the prevalence estimates of each test in comparison to the population-level infection prevalence and estimated the proportion of trace results that were likely true positives. Results Kato-Katz yielded the lowest prevalence (6.8%), and CCAB with trace considered positive yielded the highest (53.5%). There were many more trace results recorded by CCA in Burundi (32.4%) than in Leiden (2.3%). Estimated prevalence with CAA was 46.5%. LCA indicated that Kato-Katz had the lowest sensitivity: 15.9% [Bayesian Credible Interval (BCI): 9.2–23.5%] with CCA-trace considered negative and 15.0% with trace as positive (BCI: 9.6–21.4%), implying that Kato-Katz missed approximately 85% of infections. CCAB underestimated disease prevalence when trace was considered negative and overestimated disease prevalence when trace was considered positive, by approximately 12 percentage points each way, and CAA overestimated prevalence in both models. Our results suggest that approximately 52.2% (BCI: 37.8–5.8%) of the CCAB trace readings were true infections. Conclusions Whether measured in the laboratory or the field, CCA outperformed Kato-Katz at the low infection intensities in Burundi. CCA with trace as negative likely missed many infections, whereas CCA with trace as positive overestimated prevalence. In the absence of a field-friendly gold standard diagnostic, the use of a variety of diagnostics with differing properties will become increasingly important as programs move towards elimination of schistosomiasis. It is clear that CCA is a valuable tool for the detection and mapping of S. mansoni infection in the field and CAA may be a valuable field tool in the future

Effects of schistosomiasis on susceptibility to HIV-1 infection and HIV-1 viral load at HIV-1 seroconversion: A nested case-control study.

Schistosomiasis affects 218 million people worldwide, with most infections in Africa. Prevalence studies suggest that people with chronic schistosomiasis may have higher risk of HIV-1 acquisition and impaired ability to control HIV-1 replication once infected. We hypothesized that: (1) pre-existing schistosome infection may increase the odds of HIV-1 acquisition and that the effects may differ between men and women, and (2) individuals with active schistosome infection at the time of HIV-1 acquisition may have impaired immune control of HIV-1, resulting in higher HIV-1 viral loads at HIV-1 seroconversion.We conducted a nested case-control study within a large population-based survey of HIV-1 transmission in Tanzania. A population of adults from seven villages was tested for HIV in 2007, 2010, and 2013 and dried blood spots were archived for future studies with participants' consent. Approximately 40% of this population has Schistosoma mansoni infection, and 2% has S. haematobium. We tested for schistosome antigens in the pre- and post-HIV-1-seroconversion blood spots of people who acquired HIV-1. We also tested blood spots of matched controls who did not acquire HIV-1 and calculated the odds that a person with schistosomiasis would become HIV-1-infected compared to these matched controls. Analysis was stratified by gender. We compared 73 HIV-1 seroconverters with 265 controls. Women with schistosome infections had a higher odds of HIV-1 acquisition than those without (adjusted OR = 2.8 [1.2-6.6], p = 0.019). Schistosome-infected men did not have an increased odds of HIV-1 acquisition (adjusted OR = 0.7 [0.3-1.8], p = 0.42). We additionally compared HIV-1 RNA levels in the post-seroconversion blood spots in HIV-1 seroconverters with schistosomiasis versus those without who became HIV-infected in 2010, before antiretroviral therapy was widely available in the region. The median whole blood HIV-1 RNA level in the 15 HIV-1 seroconverters with schistosome infection was significantly higher than in the 22 without schistosomiasis: 4.4 [3.9-4.6] log10 copies/mL versus 3.7 [3.2-4.3], p = 0.017.We confirm, in an area with endemic S. mansoni, that pre-existing schistosome infection increases odds of HIV-1 acquisition in women and raises HIV-1 viral load at the time of HIV-1 seroconversion. This is the first study to demonstrate the effect of schistosome infection on HIV-1 susceptibility and viral control, and to differentiate effects by gender. Validation studies will be needed at additional sites

Additional file 1: of Latent class analysis to evaluate performance of point-of-care CCA for low-intensity Schistosoma mansoni infections in Burundi

Table S1. Bayesian Deviance Information Criterion (DIC) from models with different covariances fitted. Table S2. Summary statistics by school and prevalence estimates for each separate test by school. Table S3. Comparison of CCA results in Burundi and Leiden. Table S4. Test result combinations overall and by school, when CCA trace was considered negative and positive. Table S5. Estimate and 95% BCIs of difference between same estimates from trace negative and trace positive models presented in Table 4. Table S6. Output from LCA when specificity of CAA fixed to 100%. Table S7. Estimate and 95% BCIs of difference between same estimates from different models. Table S8 Estimated test and infection prevalence when specificity of CAA fixed to 100%. Fig. S1. Sensitivity of models to prior assumptions. Code S1. Code for running the LCA in R2OpenBugs (DOCX 845 kb

Median log₁₀ whole blood HIV-1 RNA levels in recent HIV-1 seroconverters with and without schistosome infection.

<p>Summary plot depicting median and interquartile range of log₁₀ of whole blood HIV-1 RNA level in copies/mL as quantitated from dried blood spots in recent HIV-1 seroconverters with or without schistosome infection. The median viral load was 4.4 [3.9–4.6] HIV-1 RNA log copies/mL in those with schistosome infection versus 3.7 [3.2–4.3] among those without (p = 0.017 by Wilcoxon rank-sum test).</p

Effects of schistosomiasis on susceptibility to HIV-1 infection and HIV-1 viral load at HIV-1 seroconversion: A nested case-control study

<div><p>Background</p><p>Schistosomiasis affects 218 million people worldwide, with most infections in Africa. Prevalence studies suggest that people with chronic schistosomiasis may have higher risk of HIV-1 acquisition and impaired ability to control HIV-1 replication once infected. We hypothesized that: (1) pre-existing schistosome infection may increase the odds of HIV-1 acquisition and that the effects may differ between men and women, and (2) individuals with active schistosome infection at the time of HIV-1 acquisition may have impaired immune control of HIV-1, resulting in higher HIV-1 viral loads at HIV-1 seroconversion.</p><p>Methodology/Principal findings</p><p>We conducted a nested case-control study within a large population-based survey of HIV-1 transmission in Tanzania. A population of adults from seven villages was tested for HIV in 2007, 2010, and 2013 and dried blood spots were archived for future studies with participants’ consent. Approximately 40% of this population has <i>Schistosoma mansoni</i> infection, and 2% has <i>S</i>. <i>haematobium</i>. We tested for schistosome antigens in the pre- and post-HIV-1-seroconversion blood spots of people who acquired HIV-1. We also tested blood spots of matched controls who did not acquire HIV-1 and calculated the odds that a person with schistosomiasis would become HIV-1-infected compared to these matched controls. Analysis was stratified by gender. We compared 73 HIV-1 seroconverters with 265 controls. Women with schistosome infections had a higher odds of HIV-1 acquisition than those without (adjusted OR = 2.8 [1.2–6.6], p = 0.019). Schistosome-infected men did not have an increased odds of HIV-1 acquisition (adjusted OR = 0.7 [0.3–1.8], p = 0.42). We additionally compared HIV-1 RNA levels in the post-seroconversion blood spots in HIV-1 seroconverters with schistosomiasis versus those without who became HIV-infected in 2010, before antiretroviral therapy was widely available in the region. The median whole blood HIV-1 RNA level in the 15 HIV-1 seroconverters with schistosome infection was significantly higher than in the 22 without schistosomiasis: 4.4 [3.9–4.6] log₁₀ copies/mL versus 3.7 [3.2–4.3], p = 0.017.</p><p>Conclusions/Significance</p><p>We confirm, in an area with endemic <i>S</i>. <i>mansoni</i>, that pre-existing schistosome infection increases odds of HIV-1 acquisition in women and raises HIV-1 viral load at the time of HIV-1 seroconversion. This is the first study to demonstrate the effect of schistosome infection on HIV-1 susceptibility and viral control, and to differentiate effects by gender. Validation studies will be needed at additional sites.</p></div