The effect of Schistosoma Mansoni infection on T-cell responses to measles booster immunization among 3-5 year old children

Abstract

Context: Measles virus infection causes morbidities and still contributes to childhood mortality in Asia and sub-Saharan Africa, despite the wide spread vaccination initiatives by the World Health Organization. Schistosoma mansoni, a major parasitic helminth, chronically infects over 200 million people worldwide and is showed to modulate host immune responses by skewing it towards a type two (TH2) immune response. A good type one (TH1) cell phenotype response to measles vaccine is considered optimal for protection against measles. Infants infected with Schistosoma mansoni may not be able to mount optimal immune responses to measles vaccine as a result of schistosome mediated immune modulation. Objective: The objectives of this study were to determine the effect of Schistosoma mansoni infection on CD4+ T Cells responses to measles booster immunization among 3-5 year old children. Methodology: This study was nested in a larger study on “Immune Modulation in Schistosome Mansoni Infection and Effects on Immune Responses to Childhood Measles Immunization” (ISRCTN87107592) and utilized previously collected and stored PBMC samples. Peripheral blood mononuclear cells (PBMC) obtained from 30 S. mansoni infected and 10 uninfected 3-5 years old children were examined for IFN-γ, IL2, IL4, IL10 and TNF-α responses to measles grade 2 antigen and to a pool of 21 peptides of measles virus H protein. FoxP3 expression among the children was also examined. Findings: At baseline and a week after measles booster immunization, Schistosoma mansoni infected children showed lower IL2 and TNF-α responses to measles antigens than uninfected children. Conversely, higher IL4 and IL10 responses to measles antigens as well as FOXP3 expression was higher among the infected children. Polyfunctional CD4+ cells producing three cytokines IFN-γ, TNF-α and IL2 were only observed among the uninfected children and none in the S. mansoni infected children. Conclusions: this study demonstrated an association between S.mansoni infection and increased levels of measles antigen specific IL4, IL10 and FOXP3 in S.mansoni infected children after measles booster immunization. It also demonstrated that S.mansoni infection is associated with decreased levels of TNF-α and IL2. This study further demonstrated an association between S.mansoni infection and decreased T cell poly-functionality