Possible new control measures for SARS

Hypothesis:  MMR may prevent the fatal form of Severe Acute Respiratory Syndrome

(cross reactivity hypothesis)

 

 

Quotes

“Doctors are trying to explain why a virus that moves with relative ease through the adult population, so far infecting 3,000 worldwide with more than 100 dead, has come up against something of an immunological wall when it comes to youngsters.” – CNN -Friday, April 11

 

In the south China city of Guangzhou, just miles from where the outbreak began, Guangzhou Children's Hospital has yet to see its first patient with Severe Acute Respiratory Syndrome (SARS), officials said this week.

 

"We haven't had any cases of SARS," said Yu Minghua, chief of paediatrics at south China's largest hospital for children.

 

"No one has died and no one has been on a respirator...This hospital has about 300 doctors, and none of them has got SARS either."- Yu Minghua, chief of paediatrics

 

Hong Kong's C.K. Li said that children may, in fact, get SARS at proportionate rates to their share of the population, but that their cases may be less debilitating.

 

"We probably see quite a similar number of children who are affected as adults," he said. "But...it seems that young children are not so severely affected."

 

 

Observations:

1)     So far almost no children of the MMR vaccination age group has gotten the fatal or severe form of SARS*

2)     Infants below the MMR vaccination age groups may still get the severe form of SARS.

3)     Frequent detection of  Paramyxoviridae in patients with SARS

4)    Possible cross reactivity of antibodies generated by the live attenuated Paramyxoviridae  (mump/measles virus) in MMR and Paramyxoviridae detected in SARS cases.

 

 

 

Epidemiological evidence

1)     MMR vaccine is widely deployed in China, Hong Kong and Singapore among the pediatric age group.

2)     Paramyxoviride is found frequently in SARS patients by investigators in both Hong Kong and Canada.

3)     Children’s “immunogical wall” (as quoted by CNN Health) or the “pediatric sparing effect” is universally noted in all countries affected by the SARS virus.

4)     These countries all have a vigorous MMR vaccination program for this particular age group.

 

 

Likely Mechanism – (cross reactivity  Hypothesis )

1)     Paramyxoviridae family (the same family as measles, mumps, and parainfluenza)

2)     MMR uses live attenuated Paramyxoviridae

3)     Paramyxoviridae family share common surface antigens eg. (HN-glycoprotein and f-glycoprotein- essential for the infectivity of the virus)

4)     Paramyxoviridae surface glycoproteins or antigen will induce antibodies in vivo that may cross react amongst the members of the virus family.

 

 

Potential problems

1)     Woman who may get pregnant cannot use MMR

2)     Controversy over the very low association of MMR with autism and bowel disease.

3)     MMR would not stop a person getting an infection (or transmitting it) from the new coronavirus believed to be the cause of SARS. More likely, it protects a person from the severe form of SARS when there is a secondary Paramyxoviridae infection (superinfection).

 

 

Public Health implications

1)     Make MMR booster available to the high-risk groups – patients in hospitals, geriatrics populations and health care workers.

2)     Reducing the severity of SARS in terms of fatalities and ICU admissions by increasing the adult MMR booster uptake.

 

Next Steps

1)     Intensive epidemiological research into the relationship between MMR vaccination and the severity of SARS infection.

2)     Investigate the relationship between the antibodies levels of Paramyxoviridae and the severity of the SARS in patients

3)     Identification and large-scale production of an effective monoclonal antibody to use as passive immunization to reduce the mortality of patients with severe forms of SARS.

 

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LINKS

http://www.cnn.com/2003/HEALTH/04/10/sars.child.reut/

http://www.canada.com/toronto/story.asp?id=6C929C38-314B-41CA-A102-27BA340D4B9D

http://usinfo.state.gov/topical/global/hiv/03032503.htm

http://www-micro.msb.le.ac.uk/3035/paramyxoviruses.html

 

 

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