Methods: The study was conducted in the Department of Medical Microbiology and Parasitology, University Putra Malaysia in 2014-2017. Saline extract protein from the infective larvae of S. ratti was used to immunize BALB/c mice and subsequent fusion of the B-cells with myeloma cells (SP2/0) using 50% PEG. The hybridomas were cultured in HAT medium and cloned by limiting dilutions. Positive hybrids were screened by indirect ELISA. The ascites fluid from the antibody-secreting hybridoma was purified and the MAb was characterized by western-blots and evaluated in sandwich ELISA for reactivity against the homologous and heterologous antigens.
Results: An IgG1 that recognizes a 30 and 34 kDa protein bands was obtained. The MAb was recognized by all S. ratti-related antigens and cross-reacted with only Toxocara canis antigens in both assays. The minimum antigen detection limit was found to be 5 ng/ml. All antibody-positive rat and dog sera evaluated have shown antigen-positive reactions in Sandwich-ELISA.
Conclusion: The MAb produced, was able to detect antigens in strongyloidiasis and toxocariasis in animal models and may also be useful for the serological detection of active strongyloidiasis and visceral toxocariasis in human sera.
METHODS: This cross-sectional study was performed at Hue Central Hospital from 2012-2016 on 176 CKD and 64 control subjects. ADMA levels were measured by using the enzyme linked immunosorbent assay (ELISA) method.
RESULTS: Mean ADMA level was markedly higher (p<0.001) in all patients combined (0.73±0.24μmol/L) than in control subjects (0.47±0.13μmol/L). Mean ADMA levels in advanced kidney disease were higher than control subjects. ADMA levels correlated inversely and relatively strictly to estimated glomerular filtration rate (eGFR) (r = -0.689; p<0.001), haemoglobin (r = -0.525; p<0.001) and haematocrit (r = - 0.491; p<0.001); correlated favourably and relatively strictly to serum creatinine (r = 0.569; p<0.001) and serum urea (r = 0.642; p<0.001). ADMA elevation was predicted simultaneously by eGFR<60 mL/min/1.73m2 (p<0.001), anaemia (p=0.002), body mass index (BMI) (p=0.011) and high sensitivity C-reactive protein (hs-CRP) (p=0.041). Cutoff of ≥0.68μmol/L, ADMA levels predict reduction of eGFR<60 mL/min/1.73m2, sensitivity of 86.9 %, specificity of 82.6%, area under ROC 92.4% (95%CI: 88.6-96.1%).
METHODOLOGY/PRINCIPAL FINDINGS: Using in silico tools, we designed and expressed four novel P. knowlesi protein products to address the distinct lack of suitable serosurveillance tools: PkSERA3 antigens 1 and 2, PkSSP2/TRAP and PkTSERA2 antigen 1. Antibody prevalence to these antigens was determined by ELISA for three time-points post-treatment from a hospital-based clinical treatment trial in Sabah, East Malaysia (n = 97 individuals; 241 total samples for all time points). Higher responses were observed for the PkSERA3 antigen 2 (67%, 65/97) across all time-points (day 0: 36.9% 34/92; day 7: 63.8% 46/72; day 28: 58.4% 45/77) with significant differences between the clinical cases and controls (n = 55, mean plus 3 SD) (day 0 p<0.0001; day 7 p<0.0001; day 28 p<0.0001). Using boosted regression trees, we developed models to classify P. knowlesi exposure (cross-validated AUC 88.9%; IQR 86.1-91.3%) and identified the most predictive antibody responses.
CONCLUSIONS/SIGNIFICANCE: The PkSERA3 antigen 2 had the highest relative variable importance in all models. Further validation of these antigens is underway to determine the specificity of these tools in the context of multi-species infections at the population level.