[afro-nets] RFI: Malaria and Helminths co-infections - what is the true picture?

["Maurice Odiere" <maurice.odiere@mail.mcgill.ca>]

RFI: Malaria and Helminths co-infections - what is the true picture?
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Most research in parasite ecology has frequently focused on single parasites in individual hosts. However, we know that under natural conditions, one host may be infected by more than one parasite (as is the case with Plasmodium and most helminths occurring in the same endemic foci), which then makes the dynamics of interactions to be complex. Due to these multiple infections, the immunological pathways activated here can become complicated to study.

Some evidence suggests that interactions occur between helminths-malaria co-infections, although it is unclear whether this effect is beneficial or harmful to the host. The type 1-dependent control of malaria parasitemia might be impaired by the type 2 milieu of preexisting helminth infection. Alternatively, the immunomodulatory effects of helminths might affect the likelihood of malarial immunopathology.

Several studies on the effect of co-infections, however, have produced conflicting results. Why is this the case? 

Another aspect is in regard to the impact of these co-infections on malaria vaccines. As has been shown, chronic helminth infections usually induce strong type 2 and regulatory immune responses, and are known to influence immune activity to other antigens such as allergens and vaccines. Many malaria vaccines have been shown to target parasite antigens that have the capacity to induce specific antibodies capable of inhibiting parasite growth. In the ideal sense, vaccines should also stimulate an efficient CD4+ Th1 response. Is it possible therefore, that helminth infections may affect the induction of an efficient Th1 type of immune response to a potential malaria vaccine? What impact, if any, does this have on the efficacy of vaccine development in malaria? 
Since helminth infections are prevalent throughout tropical regions where malaria parasites are transmitted, co-infections of helminths and malaria parasites will frequently be observed. 

I would appreciate any input/literature on this subject.

Thanks,

Maurice Odiere

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Maurice R. Odiere,
Institute of Parasitology,
Macdonald campus of McGill University,
21,111 Lakeshore Road, Ste-Anne de Bellevue
Quebec H9X 3V9, Canada
Phone +1(514) 398-8382
Fax +1(514) 398-7857
Email: mailto:maurice.odiere@mail.mcgill.ca