Vaccines, asthma, Samter's and the Th1-Th2 theory

[Guest guest]

Immunization by vaccines is a complex science. Some believe that a vaccine

schedule that

is too precocious can increase the risk of pathologies such as asthma in

children.

The following article gives credit to this theory : the vaccination history of

11,000 children

in Manitoba was retrospectively studied, and it was found that children whose

vaccination

schedule was delayed as little as 2 months had 1/2 less occurrences of asthma.

This kind

of result should at the very least have the people in charge of vaccine policy

in Canada do

some extra research.

The (crudely simplified) theory behind this is that the DPT vaccine is supposed

to induce

what is called a " Th2-biaised response " . This means there is an increase in the

production

of " T-helper-2 " lymphocytes following vaccination. T-helper lymphocytes come in

2

varieties, 1 and 2, each corresponding to a particular organization of the

body's immune

response. For instance, a Th1-response is more useful than a Th2-response

against some

viruses and bacteria, while a Th2-response is more useful against parasites.

Also, both

types of responses are competitive between themselves : if there is a Th-1

biais, it reduces

the Th2 population, and vice-versa. The body needs and uses both types of

responses

according to the pathology it senses, so one is not worse or better than the

other in

general.

For a graphic illustration of the Th1-Th2 model, see :

http://www.digizyme.com/images/L3_allecure_anim.swf

Problems arise when there is too much of a biais in the immune response, ie for

instance

when a response that should be Th1-biaised to a certain extent is not enough

Th1-

oriented, or when there is an over-production of Th-1 when there should not be

one (and

the same applies for Th-2).

Vaccines may alter, briefly or more lastingly, the Th-profile, but this may vary

from one

vaccine to the other. For instance, some believe Pneumovaccines are more likely

to induce

a Th1-biaised response.

Many believe asthma is a Th-2 oriented pathology, so the questioning behind the

Canada

study was : " Since asthma is a Th-2 disease and DTP is believed to induce a Th-2

biais, is

there a possibility that vaccinating children too early might induce a Th-2

biais favorable

to asthma ? " According to the article below, this causality cannot be ruled out.

The Th1-Th2 theory is a model that is not perfect, but is likely to have some

validity for a

number of diseases. Note that it may also be partially disproved or improved in

the future.

Samter's is likely to be a Th2-biaised-condition (judging from Dr. son's

2006 article

in the Journal of Allergy and Clinical Immunology), like asthma. Likewise,

chronic

rhinosinusitis with polyps is thought to be a Th2-biaised condition (see

American Journal

of Rhinology 2008).

Would this help explain why Pneumovaccines (which may have a pro-Th1 effect)

have had

a temporary beneficial effect on some of us ? This is a tempting assumption.

Of course, the question that springs up at this point is : if Samter's and

asthma really are

Th2-biaised diseases, can we shift the balance back to the normal equilibrium

between

Th1 and Th2, by employing something like " pro-Th1-shifters " ? Some people,

including

researchers, supplement manufacturers, etc have asked themselves this question

and are

indeed researching, producing and selling supplements, etc.

At this point, however, there are more questions than answers, essentially

because :

- the Th1-Th2 theory is not foolproof,

- the theory was designed using mice models, and it turned out that it did not

work

exactly in the same way in humans in a number of circumstances,

- measuring the Th1-Th2 balance is not easy at all nor commonly available, so

there is no

possibility of knowing whether one is biaised or not, and it is likely that it

will not be

available soon given the cost and complexity,

- even if a general Th2 biais in Samter's was proved, and supposing everyone was

Th2

biaised, trying by oneself to shift a biais is not easy and probably calls for

care in order

not to create a biais in the other direction,

- immunomudulators are sometimes safe, but also sometimes tricky meds with side

effects, and their effect on the Th1-Th2 balance is rarely established (a few

studies do

exist, though).

So, more research is warranted, as they often conclude articles.

That being said, a few safe and easy things can be tried :

- early sleep is associated with a Th1 profile, while late sleep is rather

associated with a

Th2 profile - so going to sleep early is a rather good idea for asthma and

Samter's

sufferers ; also, it is possible that asthmatics holding night-shift jobs

experience a

worsening of their condition ;

- some probiotics seem to be Th1-promoters and are safe.

Beta-glucans (proteins from wheat or mushrooms) seem to be Th1-promoters too,

and

seem safe so far, at least for short courses - but I have not researched them

yet and

cannot make any recommendation, and there may be a lot of differences between

various

brands.

Here is the article about children vaccination and asthma :

-------

Journal of Allergy and Clinical Immunology

March, 2008

Delay in diphtheria, pertussis, tetanus vaccination is associated with a reduced

risk of

childhood asthma

Kara L. Mc, MSca, Shamima I. Huq, BScbde, M. Lix, PhDad, Allan B.

Becker, MD,

FRCPCc, Anita L. Kozyrskyj, PhDabcde

Received 22 September 2006; received in revised form 11 November 2007; accepted

13

November 2007. published online 21 January 2008.

Background

Early childhood immunizations have been viewed as promoters of asthma

development by

stimulating a TH2-type immune response or decreasing microbial pressure, which

shifts

the balance between TH1 and TH2 immunity.

Objective

Differing time schedules for childhood immunizations may explain the discrepant

findings

of an association with asthma reported in observational studies. This research

was

undertaken to determine whether timing of diphtheria, pertussis, tetanus (DPT)

immunization has an effect on the development of childhood asthma by age 7

years.

Methods

This was a retrospective longitudinal study of a cohort of children born in

Manitoba in

1995. The complete immunization and health care records of cohort children from

birth

until age 7 years were available for analysis. The adjusted odds ratio for

asthma at age 7

years according to timing of DPT immunization was computed from multivariable

logistic

regression.

Results

Among 11, 531 children who received at least 4 doses of DPT, the risk of asthma

was

reduced to ½ in children whose first dose of DPT was delayed by more than 2

months. The

likelihood of asthma in children with delays in all 3 doses was 0.39 (95% CI,

0.18-0.86).

Conclusion

We found a negative association between delay in administration of the first

dose of

whole-cell DPT immunization in childhood and the development of asthma; the

association was greater with delays in all of the first 3 doses. The mechanism

for this

phenomenon requires further research.