Biology Reference
In-Depth Information
parasite-derived immunomodulator components to ameliorate allergic
inflammation are presented.
The immunomodulation is evident in chronic and heavily parasited
individuals; this could mean that high doses are needed to achieve an
appropriate downregulation of the allergic responses, but also may reflect,
as already mentioned, that a particular subpopulation is highly sensitive to
parasite-derived immunomodulation (
Figure 2.2
). Since, at the population
level, this degree of sensitivity may appear as a gradient, it is likely that
dosage of a particular potential therapeutic product should be adapted to
this circumstance. In addition, if the hypothesis of a genetic predisposition
to helminth-induced immunosuppression were true, immunosuppressor
products will not exert their effects in all allergic patients.
Since immunosuppressant as well as immunostimulant effects have
been observed during helminthiases, therapeutic immunomodulation
should be induced with helminth-purified products and not with live
helminth parasites. The use of “non-pathogen” or natural-infecting
helminths (e.g.
Ancylostoma
spp.) does not avoid the risk of sensitiza-
tion to cross-reactive allergens or the unspecific boosting the allergic
responses. In addition, helminths are not harmless and in some cases
serious health problems may arise. Using low doses of parasites and
short-term infections, in addition to providing contradictory outcomes,
has not significantly ameliorated asthma or rhinitis symptoms
174,175
and
may not be a good strategy because, as has been described in this chapter,
some epidemiological studies have shown that mild helminth infections
are associated with more allergy symptoms. As in any other health
problem, ethical issues are paramount in this field of therapeutic research,
especially when using live parasites.
In addition to PAS-1, which has immunosuppressor activity on both Th1
and Th2 responses,
176
the potential
Ascaris
-derived immunomodulator
molecules comprise a large number of the secretome
20
but none of them
has been fully characterized. Given the different pathogenic mechanisms
of helminthiases, especially the larval migratory phases and the final
localization of mature forms, it is possible that not all helminths produce
the same immunomodulators; the search for those downregulating the
allergic responses without adverse effects upon the protective immune
response will provide the most useful results in this field.
CONCLUSION
Ascariasis influences allergy, namely asthma, in several ways. Other
intestinal helminthiases may potentiate its effects on allergy, but it is
hoped that appropriate socioeconomic progress coupled with control
efforts will lead a significant reduction in soil-transmitted helminthiases.
