Dengue vaccine in the offing

Jayashree Padmini - New Delhi

Dengue fever, the disease without any effective therapy, may have a vaccine in the future if the independent research works by the Hyderabad-based Biological Evans and the Delhi-based International Centre for Genetic Engineering & Biotechnology (ICGEB) prove fruitful.

Mahima Datla, vice-president, Biological Evans, Hyderabad, confirmed the development and said that the company is developing a dengue vaccine and it is licensed from National Institute of Health, USA.

‘‘We are at a very early stage of development and we would be able to give further details of the vaccine candidate and an update on the progress of the project within the next couple of months,’’ said Mahima.

The candidate vaccine is understood to be using a unique technology, 30 point deletion mutant virus addition of chimeric antigen.

The ICGEB’s project on a dengue vaccine and a diagnostics kit is in the early stages of development.

The institution has initiated work to evaluate the potential of replication, defective adenovirus as a live vector for the expression of recombinant structural and nonstructural dengue viral proteins in mammalian cells.

Such a vector would fail to replicate in-vivo, but express the foreign protein during abortive infection resulting in efficient stimulation of both arms of the immune response. This approach will obviate problems encountered with purification of the expressed protein. The major objective of this project is to design, construct and evaluate a recombinant adenovirus vector capable of co-expressing protective antigens of all four serotypes of dengue viruses in mammalian cells both in-vitro and in-vivo.

A marketing study conducted by Easton Associates estimates the potential annual dengue vaccine market to be in excess of $5 billion, with a realistic market of $300-$400 million annually.

More than 90 per cent of these revenues are attributable to travelers from the US, Europe, and Japan - who make more than 50 million visits per year to dengue endemic areas.

In the past many years the dengue vaccine research was stymied by complex technical hurdles when the research efforts failed to establish a tetravalent immunity against all the four types of dengue viruses.

Last year the Bill & Melinda Gates Foundation awarded the International Vaccine Institute (IVI) US $55 million on behalf of The Pediatric Dengue Vaccine Initiative (PDVI). Key partners of this initiative include the WHO, vaccine companies, and international and national groups working to control and prevent dengue around the world.

Dengue fever is expanding globally with an estimated 50 million to 100 million cases of dengue world-wide annually with more than 20,000 deaths. It is carried by mosquitoes and causes severe flu-like symptoms that can lead to a life threatening hemorrhagic fever.

The number of countries reporting dengue hemorrhagic fever has increased more than four-fold over the past three decades, and in 2001-2002, dengue epidemics reached an all-time high in Brazil, Venezuela, Ecuador, Peru, Thailand, Vietnam, and Myanmar. The number of cases in the Americas has risen from 60,000 in 1980 to 700,000 in 2000. In 2001, Hawaii reported its first dengue outbreak in more than 50 years.

Current dengue prevention measures rely on protecting against and eliminating the mosquito that transmits the dengue viruses to humans. However, this mosquito is remarkably well adapted to urban environments because it breeds inside homes, and has proven very difficult to control even with stringent efforts. As a result, current dengue control programs have been unable to protect the millions of children at risk of infection and illness, heightening the need for an effective dengue vaccine.