Dengue virus is an enveloped single-stranded positive-sense RNA virus, which belongs to the family of Flaviviridae. Dengue virus has approximately 11,000 nucleotides in length that encodes three structural (C, Env, M) and seven non-structural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5). There are four different serotypes of dengue virus (DENV 1-4) and the classification is based on structural antigens that induce type-specific antibodies at the time of infection. Dengue fever is an arthropod-borne disease caused by the dengue virus (DENV), mainly transmitted by Aedes aegypti mosquitoes. Dengue fever is the most popular mosquito-borne disease in the world. The dengue virus mainly spreads in tropical and subtropical regions, including Southeast Asia, the Americas, Africa, the Western Pacific, and the Eastern Mediterranean.
Dengue virus research should be conducted using biosafety level 2 practices, equipment, and facility design. Laboratory diagnostic methods to confirm dengue virus infection may involve detection of virus, viral nucleic acid, antigen or antibody, or a combination of these techniques. The virus can be detected in serum, plasma, circulating blood cells, and other tissues for 4-5 days after onset. In the early stages of the disease, viral isolation, nucleic acid or antigen testing can be used to diagnose infection. At the end of the acute phase of infection, serology is the method of choice for diagnosis. Serological tests for dengue virus generally use IgM antibody-capture enzyme-linked immunosorbent assay (MAC-ELISA), IgG ELISA, IgM capture and IgG capture ELISAs, anti-dengue virus IgA capture ELISA, and haemagglutination-inhibition (HI) test.
Figure 1. Dengue virus replication cycle.
DENV infection is initiated by the binding of the virus to the host cell receptor (Figure 1a). The virus is then internalized through clathrin-mediated endocytosis (Figure 1b), and the low pH in the endosome triggers the membrane fusion reaction (Figure 1c). After membrane fusion and nucleocapsid uncoating, the viral genome is translated into a polyprotein, which is cleaved into structural and NS proteins (Figure 1d). Structural protein envelope (E) and premembrane (prM) are translocated to the endoplasmic reticulum. The NS protein makes RNA replication possible, including producing positive (orange) and negative (green) sense single-stranded RNA copies (Figure 1e). The genomic RNA (orange) is packed by capsid proteins, and the nucleocapsid buds into the endoplasmic reticulum lumen to form enveloped immature virions (Figure 1f). Immature virions are transported through the secretory pathway, where prM cleavage into M (Figure 1g) occurs. Finally, mature virus particles are released by exocytosis (Figure 1h&i).
At present, no antiviral drugs have been developed to treat dengue virus infection, and the treatment is still supportive. Although the DENV vaccine has recently been used in some countries, its indications are limited due to the severe risk of dengue fever in some populations. This has led to calls for intensified research efforts to develop new vaccines, therapeutics, and vector-control strategies for better prevention and control of dengue fever. Creative Diagnostics has extensive knowledge to support clients in dengue antiviral research and development.
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