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How Dengue Tricks the Immune System January 14, 2007

Posted by Hegemony in Health, Science.
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Dengue is a medically relevant virus that is common in tropical climates. The virus itself is a single stranded RNA virus. It is spread by the mosquito Aedes aegypti. It causes two diseases, dengue fever and dengue hemorrhagic fever. One cannot contract the second without having had the first. This is a very interesting component of dengue infection that relies on the host’s immune response. It is also why vaccination for dengue is seen as a risky proposition.

There are four different strains of dengue virus. These strains are very similar; so similar in fact that the immune system recognizes all of them after seeing only one. But recognition is not protection. Human T-cells each are programmed to recognize a specific pattern (or antigen). In the first infection virus particles will be captured and processed by so-called antigen presenting cells. These viruses will be presented to T-cells causing them to become activated. And likewise B-cells will encounter their antigen free floating and become activated. B-cells produce antibodies. Antibodies are used (among other things) to tag the viruses to encourage their uptake by macrophages (called opsonization) and inactivate them.

This first infection is known as dengue fever and will last 6 or 7 days. Its symptoms are much like a severe flu. Most people get over it without incident. If one becomes infected again things could go wrong. There are four strains of Dengue, all of which are all very similar. If you are infected with a different strain than you encountered the first time, you will contract dengue hemorrhagic fever.

But why does this happen? As it turns out, the antibodies from the first infection will attach to the virus particles but will not inactivate them. The strains are just different enough to remain active in the presence of another strain’s antibodies. These are referred to as “non-neutralizing antibodies”. These antibodies will still cause opsonization. So Macrophages willingly take up infectious viruses. This accelerates the course on infection to such a degree that hemorrhagic symptoms are seen. It’s one of those interesting times when our immune systems fail us. Imagine if people were vaccinated for dengue. What if someone missed one of the four vaccines or one was innactivated by improper storage? They would be quite prone to dengue hemorrhagic fever.

Comments»

1. mikeinmanila - January 14, 2007

Here where I am dengue is like a common cold. It comes in waves – and – moves about at a level where most of the medicine is sold over counter and many cases are often not reported unless at a full stage infection requiring hospitalization.
But once treated Dengue, if properly diagnosed is treatable.
owever the key factor is getting the right diagnosis in time.

The Philippine DOH (Dept. Of Health) and the WHO (world Health Org.) have extensive information on dengue fever on thier website both for general public and the medical pro.

Hope this helps…

2. Hegemony - January 14, 2007

Ummm… thanks? I wasn’t really looking for info though. I’m aware that supportive care can reduce mortality. But this was a description of the molecular mechanisms of Dengue infection. I was pointing out the common methods of vaccination are very risky in this case due to the immunological consequences of dengue.

3. Idetrorce - December 15, 2007

very interesting, but I don’t agree with you
Idetrorce

4. Hegemony - December 15, 2007

You don’t agree with what? I’m confused… everything in this article is scientific fact. Nothing written above is my opinion, that’s just how Dengue works.

5. miss thing - October 25, 2008

very informative from an immunological point. Thank you

6. student - May 31, 2009

hey hegemony can u tell me all the host responses to dengue fever but dont go into too much detail thanks

7. trewert - January 11, 2010

Very helpful information. thank you

8. derrick richardson - July 20, 2010

Hi a friend has just been diagnosed with Dengue Fever. He’s due to go back to SE Asia next week again what is the risk?

9. brightlight - August 7, 2010

Hi, you just gave me a very good info. Here in Northern Philippines, it’s rainy season once again and the dengue mosquitoes are all around the corners. One kid I know is now suffering from it and it’s the dengue hemorrhagic fever. The problem is, his blood type is AB which is not available at this time in the hospital’s blood bank. His parents are looking for donors asap.

10. jhay - September 16, 2010

How does Dengue affect the immune system of the patient?

help….

11. MINI - November 29, 2010

HOW DOES DENGUE AFFECT THE IMMUNE SYSTEM OF THE PATIENT

12. Joellen - July 5, 2011

I had hemorrhagic dengue fever the first time I contracted it. It is rare, but not impossible. Dengue is classified as hemorrhagic when your platelets drop below 100,000.

E. Nan - September 29, 2012

I read about a study done in Costa Rica in which researchers asked mothers to bring in children who had never had dengue. The researchers found antibodies to two strains of dengue in a large percentage of the children. They concluded that dengue can be so mild for some children that the parents do not even notice the symptoms.

13. Rage - August 19, 2011

@jhay and @MINI
simply put, it tricks your immune system into giving off incorrect antibodies for the 2nd or 3rd or 4th strain of virus..
that’s because the strains are almost the same and the immune system cannot distinguish one strain from the other.

anyway, one question to anyone who knows the answer:
if you have contracted all 4 strains and survived all of it, does it mean that you’ll be safe from infection again?

has anyone been contracted by all 4 strains already?

14. Blazer - September 10, 2011

@Rage
Nah, it’s probably rare for someone to be able to survive the second infection anyways. To answer your question with another question, even if a person is immune to all four strains, how will his antibodies be able to know which type of strain to destroy since they look so alike? If that’s the case, than that means you can probably be never immune from Dengue.

15. Pbe - November 14, 2011

Hi, I’m looking for information about the immunology of the Dengue Virus infection. Can anyone tell me the target of the antibodies produced? What’s the antigen or proteín of the virus that reacts and makes the immune system to produce antibodies?
(Sorry for my english)
Thanks!!! =)

16. My Experience with Dengue Fever in the Hospital « waves of grace - April 4, 2012

[…] unfortunate thing is that you can get dengue fever multiple times. Infection with one of the four strains of dengue virus usually produces immunity to that strain but does not provide protection against […]

17. dave - September 25, 2012

Hi, I wonder if someone can help me, in January i got dengue fever , but since then i have caught just about every flu thats been around ive had influenza , ive had just a normal cold and im about to come down with something again ,all seem to have sore joints a temp and a cough to the lungs that seems to go on for weeks, my question is after having dengue fever is your immune system weaker.

18. Jae Chasson - January 29, 2013

dengue fever is always deadly if not treated early.;

My personal web page
http://www.healthmedicinecentral.com/pinched-nerve-in-shoulder/

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