Evaluation of efficacy of various immunochromatographic rapid tests for dengue diagnosis

Evaluation of Non-Structural Protein-1(NS1) positive patients of 2013 dengue outbreak in Khyber Pakhtunkhwa, Pakistan

Background & Objective:

Dengue infection is an arthropod borne disease caused by Dengue virus in humans. Dengue virus infection has more potential to produce severe form of the disease with more severe symptoms. Proper diagnosis of dengue fever is very important for its safe management. The objective of this study was to evaluate the non structural protein-1 (NS1) positive parameter for identification of dengue fever by using ELISA from 2013 dengue outbreak in Khyber Pakhtunkhwa.

Methods:

It was a cross sectional study conducted among 384 patients tested for dengue admitted to different hospitals of Khyber Pakhtunkhwa April to December 2013 with symptoms related to classical dengue fever. Written informed consent was taken from 100 NS1 positive diagnosed patients, and 3 to 5 ml blood sample was collected for confirmation through ELISA testing. ELISA test for dengue IgG and IgM was performed two time in order to confirm the dengue cases. Data was entered and analyzed by using SPSS version 16.

Result:

The study performed on 100 NS1 positive samples of patients, admitted to hospitals with symptoms related to classical dengue fever, indicated that after performing the IgM and IgG capture ELISA test only 76 samples were actually found positive for dengue. The rest of the 24 samples were found negative for both IgM and IgG capture ELISAs. The study also revealed that 90.8 % patients had primary dengue infection and 35.5% patients had secondary dengue infection. Most patients were between the age of 10-20 years (26%), among them19.7% were having primary dengue infection. Among 10-20 years of age 50% female patients were false dengue patients.

Conclusion:

About 24 % NSI protein positive samples were found negative for both IgM and IgG capture ELISAs showed that NS1protein positivity does not confirm actual dengue infection.

Dengue Specific Immunoglobulin A Antibody is Present in Urine and Associated with Disease Severity

The kinetics of dengue virus (DENV)-specific IgA antibody in urine and the potential correlation with disease severity remain elusive. In this study, 262 serial urine samples from 78 laboratory-confirmed patients were assayed by a commercial immunoglobulin A (IgA) kit against DENV. All cases were classified into dengue fever (DF) and severe dengue (SD) according to the 2009 WHO/TDR guideline. The total positive rate of IgA in urine was 59%. DENV-specific IgA was detected in urine from day 2 to day 13 after the onset of illness in DF patients; While for SD patients, anti-DENV IgA could be detected till day 14. The positive rate of IgA in patients with secondary infection was higher than that in patients with primary infection. Importantly, during 4-7 days after the onset of illness, the IgA positive rate of SD patients was significantly higher than that of DF patients. Especially, the intensity of IgA signal in SD patients was obviously stronger than that in DF patient at the recovery stage. Overall, our results suggested that the existence of DENV-specific IgA antibodies in urine might be a warning sign for the severity of disease and its measurement might provide valuable guidance for proper patient management.

Evaluation of the diagnostic accuracy of nonstructural protein 1 Ag-based tests for dengue virus in Asian population: a meta-analysis

Background

Nonstructural protein 1 (NS1) Ag-based tests are useful for detecting dengue virus (DENV), but there is lack of evidence on the diagnostic accuracy of NS1 Ag-based tests in Asian population. Thus, we conducted this meta-analysis to obtain the overall estimated and summarized performance of the NS1 Ag-based tests in the detection of DENV in Asia.

Methods

PubMed, Embase and Medline were searched for studies that evaluated the diagnostic validity of NS1 Ag-based tests between January 1990 and November 2014. Data were analyzed by Meta-Disc and STATA software.

Results

A total of 18 studies including 3342 dengue cases and 1904 control cases which fulfilled the inclusion criteria were considered for analysis. The pooled sensitivity and specificity for NS1 Ag-based tests was 66 % (95 % CI 64.5–67.5) and 97.9 % (95 % CI 97.3–100), respectively. STRIP has the overall highest sensitivity (72.9 %, 95 % CI 70.1–75.5). According to viral serotype, the test with the highest sensitivity for DENV1, DENV2 and DENV3 were Platelia (83.7 %, 95 % CI 79.7–87.1), Panbio (71.8 %, 95 % CI 65.5–80.9) and STRIP (81.9 %, 95 % CI 75.5–87.2) respectively. The highest sensitivity for primary infection was Platelia (95.1 %, 95 % CI 92.6–96.9) and for secondary infection was STRIP (64 %, 95 % CI 53.2–73.9).

Conclusion

Our meta-analysis suggests that NS1 Ag-based test is a good diagnostic method for DENV with a high specificity. However, viral serotype, serological status, clinical severity and the duration of illness are the main factors influencing the diagnostic accuracy.

Novel recombinant multiepitope proteins for the diagnosis of asymptomatic leishmania infantum-infected dogs

Background

Visceral leishmaniasis is the most severe form of leishmaniasis. Worldwide, approximately 20% of zoonotic human visceral leishmaniasis is caused by Leishmania infantum, also known as Leishmania chagasi in Latin America. Current diagnostic methods are not accurate enough to identify Leishmania-infected animals and may compromise the effectiveness of disease control. Therefore, we aimed to produce and test two recombinant multiepitope proteins as a means to improve and increase accuracy in the diagnosis of canine visceral leishmaniasis (CVL).

Methodology/Principal Findings

Ten antigenic peptides were identified by CVL ELISA in previous work. In the current proposal, the coding sequences of these ten peptides were assembled into a synthetic gene. Furthermore, other twenty peptides were selected from work by our group where good B and T cell epitopes were mapped. The coding sequences of these peptides were also assembled into a synthetic gene. Both genes have been cloned and expressed in Escherichia coli, producing two multiepitope recombinant proteins, PQ10 and PQ20. These antigens have been used in CVL ELISA and were able to identify asymptomatic dogs (80%) more effectively than EIE-LVC kit, produced by Bio-Manguinhos (0%) and DPP kit (10%). Moreover, our recombinant proteins presented an early detection (before PCR) of infected dogs, with positivities ranging from 23% to 65%, depending on the phase of infection in which sera were acquired.

Conclusions/Significance

Our study shows that ELISA using the multiepitope proteins PQ10 and PQ20 has great potential in early CVL diagnosis. The use of these proteins in other methodologies, such as immunochromatographic tests, could be beneficial mainly for the detection of asymptomatic dogs.

Visceral leishmaniasis is the most severe form among leishmaniasis, being a neglected disease caused by a protozoan parasite. Its transmission through phlebotominae bites, between dogs and humans, classifies it as a zoonotic disease. It is caused by the specie Leishmania infantum ( = L. chagasi) and represents 20% of the world's human visceral leishmaniasis. Visceral leishmaniasis is a serious public health issue, fatal if untreated, and its incidence is increasing in urban areas of the tropics. In Brazil, one of the control measures is the identification and elimination of infected dogs, which act as reservoirs for Leishmania parasites. Diagnostic methods used to identify infection in these animals are still not accurate enough, which may compromise the effectiveness of this control measure. Thus, to contribute to the diagnosis of canine visceral leishmaniasis, we aimed to develop and test two new antigens that could be applied in early detection of infected dogs.