At times antibodies turn a double-agent. The theory adds that the antibodies attach themselves to viruses, like that of dengue, to make the infection more severe. And many times, such an infection can be life-threatening, points out Mahima, in the weekly column, exclusively for Different Truths.
My doctor tells me that globally all medical specialists are well aware of a particular disease theory. It suggests that at times antibodies turn a double-agent. The theory adds that the antibodies attach themselves to viruses, like that of dengue, to make the infection more severe. And many times, such an infection can be life-threatening.
This theory called Antibody-Dependent Enhancement (ADE) was first proposed some 40 years ago. It won both critics and supporters.
And recently, I read that a widespread and long-term study in Nicaraguan children has resulted in a compelling evidence that ADE is no longer just a theory.
Yes, molecular biologist Eva Harris from the University of California, Berkeley kick-started this research. She based her study on it to better understand dengue epidemiology as well as pathology. Her study revealed that ADE is a reality. And it is happening when people previously infected with dengue virus become infected again with the same (despite having a particular type and level of dengue antibodies in their blood).
Let’s understand this in simple words.
Over a 100 million people are affected by Dengue in all the tropical nations of the world. Dengue virus has four “stereotypes.” Each of these stereotypes triggers a unique antibody response. The first stereotype infects people causing mild flu-like symptoms, high fever with acute body-aches. But when people are infected with the second stereotype, they are the risk of death due to a haemorrhagic fever/dengue shock syndrome (DHF/DSS) that results in massive fluid loss resulting in organ failure. ADE advocates assert that to some extent such a high-risk second infection is to be blamed for pre-existing antibodies. Few others contend that T-cells, genetics, and even innate immunity also play a vital role.
The ADE hypothesis seems to be true due to the fact that Dengue’s First Stereotype’s antibody can bind to the virus. This has been proven through animal data and test tube analysis. But this binding is weak; not enough to neutralise the Dengue virus. Now, this antibody-virus complex enters the host cells with much more ease. And this ease enables the virus to copy itself in a bigger way, resulting in an intensified infection. This causes cytokines or chemical messengers to suddenly storm the body, which increases the possibility of blood vessels’ haemorrhage and shock.
But as per supporters of the ADE theory, the above mechanism is very complex. Thus, ADE isn’t always caused due to an infection from an additional dengue stereotype. Rather a perfect mix of antibody – a virus infection is necessary to cause ADE. And this perfect combination isn’t always easy to form since the number of dengue antibodies is either always high or very low.
But, I have read that Molecular Biologist Eva Harris has found out that people enter ADE “risk zone” when their antibody levels are somewhere in the middle. And Harris reached this conclusion after a study based on more than 8000 Nicaraguan Dengue-infected children. These children were in the age group 2-14 in Managua. Their blood samples were repeatedly analysed over a 12-year period.
So what results did Eva Harris get?
1) Over 600 children were hit by symptomatic dengue
2) 44 of them developed DHF (Dengue haemorrhagic fever)/ DSS (Dengue Shock Syndrome)
3) Harris analysed some 41,302 blood samples. The analysis was done in different time zones. The results showed that a child who had an intermediate antibody level became infected again with Dengue Virus. Let me remind you that we just studied above – as per ADE, the intermediate antibody level (is just perfect to bind it to the Virus. Research says that such children with intermediate antibodies have 7.64 times higher risk of falling in that category where they will develop DHS/DSS.
However, ADE critics aren’t satisfied by above findings of scientists Eva Harris. And she isn’t shaken by this. Rather her team is engaged in doing more work on it since her team’s research paper is about a sero-epidemiological finding.
But what Halstead, Harris, and many other researchers have raised certain other related, serious concerns. They have raised a concern that ADE might already be triggered in some recipients of the dengue vaccine being produced by Sanofi Pasteur. Not many know that a vaccine is a training course for body’s immune system, by injecting a small dose of the same disease-causing factor, to trigger antibodies.
Thus, this warning by Harris based on her research is a major alert for all the parents, since even the clinical trials of the dengue vaccine have reported increased hospitalization due to Dengue in young children. Harris has been reportedly insisting that increased-hospitalisation rate is due to ADE. Thus, ADE supporters warn that not just Dengue, any vaccine must be given to only to those patients who test negative from all related antibodies. However, Sanofi Pasteur has disputed the claims and caution.
Amid the fight between the ADE supporters, facts, research, and non-supporters, let me inform you that Dengue vaccine has already been licensed in at least 11 affected countries.
Thus, as per my search, even WHO has strongly recommended that Dengue vaccine must be administered in children above the age of nine. And scientist Eva Harris has a sigh of relief since she feels that at least her study-based warning has got the right perception.
So parents are alert, when the vaccine comes to India, ensure that it is administered to your child only after you and your doctor have studied what WHO says then. Prevention is always better than cure!
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A science graduate from Delhi University and MA in Mass Communication, Mahima began her career with E-Lexicon PR & Mutual PR and Hindustan Times. Soon, ANI (a collaboration with Reuters) got her aboard, where she spread her wings in TV, Print & Digital Journalism. In 2010 Rajdeep Sardesai’s flagship primetime show gave her, a dream job at CNN-IBN. From May 2017, she is a freelance journalist. She is a poet and a Sufi at heart.