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A luciferase immunoprecipitation systems assay enhances the sensitivity and specificity of diagnosis of Strongyloides stercoralis infection.

ABSTRACT: BACKGROUND:We investigated whether luciferase immunoprecipitation systems (LIPS) can be the basis for a more rapid, specific, and standardized assay for the diagnosis of Strongyloides stercoralis infection. METHODS:A LIPS assay was developed based on immunoglobulin (Ig) G or IgG4 antibody to a recombinant Strongyloides antigen (NIE) and was compared with an NIE enzyme-linked immunosorbent assay (ELISA). A second antigen, S. stercoralis immunoreactive antigen (SsIR), was tested alone and in combination with NIE. The assays were tested using serum samples from patients with parasitologically proven S. stercoralis or filarial infections and from healthy, uninfected control subjects. RESULTS:The NIE LIPS assay based on IgG antibody easily differentiated between S. stercoralis-infected and uninfected patients (P< .0001) and demonstrated improved specificity compared with the NIE ELISA (100% vs. 95%). Serum from filaria-infected patients did not cross-react when tested with the NIE LIPS assay. When SsIR was used in combination with NIE in the LIPS format, sensitivity and specificity improved to 100%, with a 7-fold difference between positive and negative values. No advantage was found in using a LIPS assay based on IgG4. At posttreatment follow-up, a significant decline in antibody titers was detected using the NIE ELISA (P< .0017) and the NIE LIPS assay (P< .0001). CONCLUSIONS:LIPS addresses several limitations of current ELISAs and represents a major advance in the diagnosis of S. stercoralis infection.

SUBMITTER: Ramanathan R

PROVIDER: S-EPMC3379004 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature

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A luciferase immunoprecipitation systems assay enhances the sensitivity and specificity of diagnosis of Strongyloides stercoralis infection.

Ramanathan Roshan R Burbelo Peter D PD Groot Sandra S Iadarola Michael J MJ Neva Franklin A FA Nutman Thomas B TB

The Journal of infectious diseases 20080801 3

<h4>Background</h4>We investigated whether luciferase immunoprecipitation systems (LIPS) can be the basis for a more rapid, specific, and standardized assay for the diagnosis of Strongyloides stercoralis infection.<h4>Methods</h4>A LIPS assay was developed based on immunoglobulin (Ig) G or IgG4 antibody to a recombinant Strongyloides antigen (NIE) and was compared with an NIE enzyme-linked immunosorbent assay (ELISA). A second antigen, S. stercoralis immunoreactive antigen (SsIR), was tested alo ...[more]

PMID: 18558872

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Project description:Detecting infections of Strongyloides stercoralis is arduous and has low sensitivity. Clinically this is a major problem because chronic infections may disseminate in the host and lead to a life threatening condition. Epidemiologically, S. stercoralis is often missed in surveys as it is difficult to identify by standard stool examination procedures. We present, for the first time, evidence that the infection can be detected in filtered urine samples collected and processed in the field and subsequently assayed for the presence of parasite DNA. Urine specimens (?40mL) were collected from 125 test and control individuals living in rural and peri-urban regions of Northern Argentina. From the same individuals, fresh stool specimens were processed using three different copropological methods. Urine specimens were filtered in the field through a 12.5cm Whatman No. 3 filter. The filters were dried and packed individually in sealable plastic bags with desiccant and shipped to a laboratory where DNA was recovered from the filter and PCR-amplified with primers specific to a dispersed repetitive sequence. Prevalence of S. stercoralis infection by stool culture and direct examination was 35/125 (28%), In contrast, PCR-based detection of parasite-specific trans-renal DNA in urine indicated that 56/125 (44.8%) carried the parasite. Of the patients that tested positive for urine-based parasite DNA, approximately half also tested positive in their stool specimens. There were 6.4% of cases where parasite larvae were seen in the stool but no DNA was amplified from the urine. As proof of principle, DNA amplification from urine residue reveals significantly more cases of S. stercoralis infection than the current standard stool examination techniques. Additional work is required to establish the relative utility, sensitivity and specificity of urine-based analysis compared to parasitological and nucleic acid detection from stool for clinical and epidemiological detection for S. stercoralis infection.

Project description:BackgroundEarly detection of porcine reproductive and respiratory syndrome virus (PRRSV) infection of swine is necessary to control this devastating disease. By monitoring host serum antibodies to viral antigens, early virus detection within herds is feasible. In this study, recombinant antigens were generated using recombinant DNA techniques to fuse PRRSV structural protein (N) or nonstructural protein 1α (nsp1α) with the Rellina luciferase gene. Next, fused genes were cloned into plasmids and transfected into HEK-293 T cells for transient expression. Upon co-incubation of lysates with pig sera, antigen-antibody complexes formed that bound to Protein-G coated onto microplates. By further measurement of luminance value, a modified form of Luciferase Immunoprecipitation Systems, namely luciferase-linked antibody capture assay (LACA) was developed for detection of PRRSV-specific antibodies.ResultsKnown anti-PRRSV antibody-positive or -negative serum samples (125 and 122 samples, respectively) were used to validate the LACA and compared it with IDEXX PRRS ×3 ELISA. Based on the result, N-Rluc and nsp1α-Rluc LACA results were 95.3 and 94.4% in agreement with IDEXX ELISA, suggested a similar specificity of LACA to IDEXX ELISA. Moreover, when both LACA and IDEXX ELISA were used to evaluate sequential serum samples obtained from PRRSV experimentally infected pigs, the PRRSV-specific antibody response was detectable as early as 3 days post-inoculation (dpi) using N-Rluc LACA, but undetectable until 7 dpi using IDEXX ELISA, suggesting an improved sensitivity of LACA. Meanwhile, antibodies specific for nsp1α were detected at higher levels overall, but were undetectable until 10 dpi. Furthermore,. Notably, one IDEXX ELISA positive result was not confirmed by LACA or IFA and was thus considered a false-positive result.ConclusionThe LACA exhibited similar specificity but improved sensitivity to that of the commercial IDEXX PRRS ×3 ELISA kit for detection of PRRSV-specific antibodies in pig serum. Importantly, LACA could be adapted for detecting antibodies against other PRRSV targets, such as nsp1α, to achieve earlier detection of PRRSV infection.

Project description:BackgroundWorldwide, an estimated 30 to 100 million people are infected with Strongyloides stercoralis, a soil-transmitted helminth. Information on the parasite is scarce in most settings. In semi-rural Cambodia, we determined infection rates and risk factors; compared two diagnostic methods (Koga agar plate [KAP] culture and Baermann technique) for detecting S. stercoralis infections, using a multiple stool examination approach; and assessed efficacy of ivermectin treatment.Methods/principal findingsWe performed a cross-sectional study in 458 children from four primary schools in semi-rural villages in Kandal province, using three diagnostic procedures (Kato-Katz, KAP culture and Baermann technique) on three stool samples. Infected children were treated with ivermectin (100 µg/kg/day for two days) and re-examined three weeks after treatment. Hookworm, S. stercoralis, Trichuris trichiura, and small trematode eggs were most prevalent, with 24.4% of children being infected with S. stercoralis. The sensitivity of KAP culture and Baermann technique was 88.4% and 75.0%, respectively and their negative predictive values were 96.4% and 92.5%, respectively. The cumulative prevalence of S. stercoralis increased from 18.6% to 24.4%, after analyzing three stool samples, which was close to the modeled 'true' prevalence of 24.8%. Children who reported defecating in latrines were significantly less infected with S. stercoralis than those who did not use latrines (p<0.001). Itchy skin and diarrhea were significantly associated with S. stercoralis infection. The cure rate of ivermectin was 98.3%.Conclusions/significanceS. stercoralis infection is highly prevalent among semi-rural Cambodian schoolchildren. The sensitivity of KAP culture is higher than that of the Baermann technique. In the absence of a "gold standard", analysis of multiple stool samples by different diagnostic methods is required to achieve a satisfactory level of sensitivity. Almost three-quarters of the infections could have been avoided by proper sanitation. Ivermectin is highly efficacious against S. stercoralis but prohibitive costs render the drug inaccessible to most Cambodians.

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A luciferase immunoprecipitation systems assay enhances the sensitivity and specificity of diagnosis of Strongyloides stercoralis infection.

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A luciferase immunoprecipitation systems assay enhances the sensitivity and specificity of diagnosis of Strongyloides stercoralis infection.

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