Parasitic helminth infections in humans modulate Trefoil Factor levels in a manner dependent on the species of parasite and age of the host

Abstract

Helminth infections, including hookworms and Schistosomes, can cause severe disability and death. Infection management and control would benefit from identification of biomarkers for early detection and prognosis. While animal models suggest that Trefoil Factor Family proteins (TFF2 and TFF3) and interleukin-33 (IL-33) -driven type 2 immune responses are critical mediators of tissue repair and worm clearance in the context of hookworm infection, very little is known about how they are modulated in the context of human helminth infection. We measured TFF2, TFF3, and IL-33 levels in serum from patients in Brazil infected with Hookworm and/or Schistosomes, and compared them to endemic and non-endemic controls. TFF2 was specifically elevated by Hookworm infection, not Schistosoma or co-infection. This elevation was more strongly correlated with age than with worm burden. To determine if this might apply more broadly to other species or regions, we measured TFFs and cytokine levels in both the serum and urine of Nigerian school children infected with S. haematobium. We found that serum levels of TFF2 and 3 were reduced by infection, but urine cytokine levels were increased (IL-1{beta}, TNF, IL-13, and IL-10). Finally, to determine if TFF2 and 3 might have immunosuppressive effects, we treated stimulated or unstimulated PMBCs with recombinant human TFF2 or TFF3 and measured proinflammatory cytokine levels. We found that rhTFF2, but not rhTFF3, was able to suppress TNF alpha and IFN gamma release from stimulated human PMBCs. Taken together, these data support a role for TFF proteins in human helminth infection. Author SummaryBillions of people are infected with parasitic helminths across the globe, especially in resource poor regions. These infections can result in severe developmental delay, disability, and death. Adequate management of helminth infection would benefit from the identification of host biomarkers in easily obtained samples (e.g. serum or urine) that correlate to infection state. Our goal was to determine if specific proteins involved in tissue repair and immune modulation are altered by infection with specific helminth species in Brazil (hookworm) or Nigeria (blood fluke). One of these proteins, Trefoil Factor 2 (TFF2), was elevated in the serum of hookworm infected individuals, and decreased in the serum of blood fluke infected children. In the blood fluke-infected children, there were also significant increases in pro-inflammatory cytokines in the urine, where the eggs burst from host tissue. Further, in laboratory experiments, Trefoil Factor 2 reduced the release of pro-inflammatory cytokines from human blood cells. This suggests that at high levels TFF2 may suppress inflammation and could serve as a biomarker for infection or treatment efficacy.