Serum cytokine levels in human ascariasis and toxocariasis.

Cytokine-mediated regulation of chronic intestinal helminth infections is well documented. The present study reports the serum cytokine responses in 38 ascariasis (stool samples positive for Ascaris lumbricoides ova) and toxocariasis (seropositive) patients, 8 ascariasis-positive and toxocariasis-seronegative patients, 22 endemic, normal, healthy subjects residing in areas hyperendemic for ascariasis and 16 normal healthy subjects residing in a low-endemic area in India. The results indicated T-helper type-2-type cytokine responses in ascariasis and toxocariasis (seropositive) and ascariasis-positive and toxocariasis-seronegative patients. The important observation was that both patients and healthy individuals in ascariasis-hyperendemic areas had significantly higher interleukin-5 (IL-5) responses than non-endemic control subjects. The altered immune responses of patients in areas hyperendemic of ascariasis may have further implications. Earlier reports suggest that the geohelminth parasites in endemic areas may modulate the immune response to oral vaccines. A critical role for IL-5 in the immune response against challenge infection consistent with the association of type-2 cytokines with vaccine-mediated protection has been reported. Furthermore, co-infection by pathogens that elicit opposing immune responses, particularly helminths vs HIV and tuberculosis, could influence the infection dynamics, progression and immunoprophylaxis of the diseases they cause. Further studies are warranted to ascertain these findings.