Adult worm-specific IgE⁄IgG4 balance is associated with low infection levels of Schistosoma mansoni in an endemic area

SUMMARY Field studies have suggested an immune-mediated mecha-nism associated with resistance to Schistosoma mansoniinfection. Overall, levels of specific IgE have been correlatedwith resistance to infection, whereas levels of IgG4 havebeen associated with susceptibility. This study aimed to eval-uate serum levels of soluble adult worm antigen preparation(SWAP)-specific IgE and IgG4 in relation to current infec-tion in a large casuistic of individuals living in an endemicarea of schistosomiasis in Bahia, Brazil. The prevalence ofS. mansoni infection was 37AE7% and the mean parasite bur-den was 55AE4 (0–2100) epg⁄faeces. There was no significantdifference in the levels of SWAP-specific IgE in individualswith different parasite burden, whereas high producers ofparasite-specific IgG4 presented higher parasite burden whencompared to low IgG4 producers. Additionally, S. mansoniparasite load was positively correlated with the levels of spe-cific IgG4 or total IgE. No significant correlation wasobserved between parasite burden and SWAP-specific IgE.Nevertheless, SWAP-specific IgE⁄IgG4 ratio was higher inuninfected or lightly infected individuals (1–99 epg⁄faeces)than in heavily infected ones (‡400 epg⁄feces). These find-ings highlight the important role of IgE⁄IgG4 ratio in theresistance to infection, which could be useful for furtherstudies in schistosomiasis vaccine candidates.Keywords helminth, IgE, IgG4, Schistosoma mansoni