Abstract
Dengue virus (DENV) represents a major threat to public health worldwide. Early DENV diagnosis should not only detect the infection but also identify patients with a higher likelihood to develop severe cases. Previous studies have suggested the potential for NS1 to serve as a viral marker for dengue severity. However, further studies using different sera panels are required to confirm this hypothesis. In this context, we developed a lab-based ELISA to detect and quantitate NS1 protein from the four DENV serotypes and from primary and secondary cases. This approach was used to calculate the circulating NS1 concentration in positive samples. We also tested the NS1 positivity of DENV-positive samples according to the Platelia Dengue NS1 Ag assay. A total of 128 samples were positive for DENV infection and were classified according to the WHO guidelines. The overall NS1 positivity was 68% according to the Platelia assay, whereas all samples were NS1-positive when analyzed with our lab-based ELISA. Fifty-four samples were positive by PCR, revealing a co-circulation of DENV1 and DENV4, and the NS1 positivity for DENV4 samples was lower than that for DENV1. The circulating NS1 concentration ranged from 7 to 284 ng/mL. Our results support previous data indicating the low efficiency of the Platelia assay to detect DENV4 infection. Moreover, this work is the first to analyze NS1 antigenemia using retrospective samples from a Brazilian outbreak.
Highlights
Classified by the World Health Organization (WHO) as one of the most prevalent arthropod-borne viruses in the world, dengue virus (DENV) constitutes a serious public health problem
These samples were subjected to the following tests: PCR analysis to identify the DENV serotype, detection of non-structural protein 1 (NS1) antigen using the Platelia Dengue NS1 Ag assay and determination of dengue-specific IgM/IgG levels to distinguish between primary and secondary infections
A serotype-specific PCR was used to detect the presence of the DENV genome in 54 samples, and these results revealed the co-existence of DENV1 (9/54) and DENV4 (45/54) infection during the 2012 dengue outbreak in Rio de Janeiro (Table 4)
Summary
Classified by the World Health Organization (WHO) as one of the most prevalent arthropod-borne viruses in the world, dengue virus (DENV) constitutes a serious public health problem. In 2009, the WHO adopted a new classification of dengue based on the clinical manifestation spectra, including dengue without or with warning signs and severe dengue [3] According to this classification, patients have dengue when they exhibit fever and two of the following symptoms: nausea, rash, aches and pains, leucopenia and a positive tourniquet test. If patients exhibit abdominal pain, persisting vomiting, fluid accumulation, mucosal bleeding, lethargy and/or liver enlargement, besides the abovementioned symptoms, they present dengue with warning signs and require strict observation and medical intervention. These patients may evolve to severe dengue characterized by severe plasma leakage, bleeding and organ impairment. This classification is believed to facilitate initial clinical care as well as clinical management and surveillance, with focused attention on the latter two cases, which are potentially dangerous
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