Innovative diagnostic tools and therapeutic aproaches for dengue disease
Dengue disease is a mosquito-borne viral disease that is one of the foremost public health issues in developing countries. Up to 100 million cases are reported each year. Over 500 000 cases of a life-threatening form of the illness, known as dengue hemorrhagic fever (DHF), occur each year, with about 25 000 fatalities (mainly children under 15). To date, there is no specific prevention or treatment.
The main aim of the DENFRAME project is to improve the management of dengue disease in the human populations of Latin America and Asia. The goals of the project are to develop and implement new diagnostic tools, to devise a comprehensive approach of innate immune response to the infection and to develop lead compounds inhibitors of Dengue virus (DV) replication. Additional goals include the collection of well-characterised data, identification of prognosis factors involved in disease severity, and standardisation of current diagnostic assays.
To reach these goals, two complementary Work Programmes (WPs) are being developed:
Dengue has emerged as the most important vector-borne viral disease in tropical areas. The four serotypes of DV each cause human disease and are transmitted by mosquitoes. Epidemics with a high frequency of life-threatening DHF continue to expand geographically. Despite the increased health and economic impacts of dengue, there is no specific prevention or treatment. Thus, there is an urgent need for reliable rapid diagnostic and new therapeutic tools for people at risk of DV infection.
The overall objective of DENFRAME is to make a fundamental contribution to the management of dengue disease in the human populations of Latin America and Asia.
The consortium has defined three scientific objectives:
The following are some additional goals:
Concerning WP1, standardisation of collection of well-characterised sequential clinical data and biological samples from dengue patients (children and adults, with different dengue patterns) in Asia and South America has been established. An electronic database has been created and data analysis has already started.
The partners have now selected the reference techniques for virological and immunological diagnosis of dengue infections, and tests such as RT-PCR, viral culture, antigen detection and in-house ELISA, are currently used. The consortium has produced recombinant DV envelope proteins that can be used for serological assays, in a microtitre plate format or as part of chemiluminescent biosensors.
They also analysed the interactions between the envelope protein and a neutralising antibody strictly specific for DV, to the exclusion of the other Flaviviruses. The partners constructed several derivatives to this antibody to better understand the molecular mechanisms by which it interacts with DV and neutralises its four serotypes. They might prove useful as therapeutic molecules against DV. The strategy of immobilisation of antigens on optical fibres and its reproducibility have been validated. The consortium constructed and validated such biosensors for several viruses and is now progressing in the application of this technology to DV.
Concerning WP2, the partners have produced many of the tools necessary for the study of DV-host interactions, such as cell lines inducible for the expression of the secreted form of the dengue envelope protein of the four DV serotypes and cell lines producing recombinant retrovirus expressing each dengue type-2 non-structural (NS) protein separately. They constructed recombinant bicistronic vectors coexpressing the green fluorescent protein and dengue NS proteins, as well as an infectious full-length dengue type-2 genome expressing gene reporters. The consortium demonstrated that dengue NS proteins play a major role in the blocking of innate immunity response of DV-infected cells. They showed that DV NS proteins upregulate expression of MHC-class I molecules at the infected cell surface. Their studies of the innate immune responses to DV infection at the skin level show that fibroblasts are targets for viral replication, and that some toll-like receptors are upregulated on these cells. A lead compound was identified and novel analogues are being synthetised and tested against DV type 2. They recently identified an antibiotic derivative that can inhibit selectively DV replication in primary screening assays.
Dengue disease has considerable impact on the economic development perspectives and is a major childhood infection in the affected communities. The DENFRAME project, through an integrated multidisciplinary approach, is providing new knowledge on biology and epidemiology, as well as new diagnostic tools and therapeutic approaches for dengue disease. It might help to implement appropriate strategies and policies for control and treatment of dengue.