Interleukin-10 expression in experimental baboon Schistosomiasis mansoni

Interleukin-10 (IL-10) plays a pivotal role in the down-regulation of pro-inflammatory cytokine production, and it ameliorates the host response to certain infectious diseases, including murine schistosomiasis. However, the role of IL-10 in human schistosomiasis is still not clear. The baboon (Papio cynocephalus) is a useful model for the study of human schistosomiasis. Thus, the dynamics of baboon IL-10 expression at specific time points during experimental infection with Schistosoma mansoni could provide insight into the role of this cytokine in humans infected with this parasite.;The goal of this research was to begin to understand if IL-10 expression coincides with oviposition, egg granuloma formation, and fever during experimental baboon schistosomiasis. The objectives for achieving this goal were: (i) to develop a molecular probe complementary to baboon IL-10 messenger RNA (mRNA) for in situ hybridization; (ii) to measure intracellular IL-10 expression in baboon peripheral blood mononuclear cells (PBMC) during infection with S. mansoni; (iii) to simultaneously measure IL-10 levels in baboon sera; and (iv) to correlate the above finding with parasitological and pathological status of baboons with different infection histories.;A 270 base nucleic acid probe complementary to baboon IL-10 mRNA was developed for in situ hybridization. Highly conserved IL-10 amino acid sequences from mammals were aligned for the design of oligomer primers flanking the target complementary DNA (cDNA). RNA was isolated from concanavalin-A stimulated baboon PBMC. IL-10 cDNA was amplified from isolated RNA by the reverse transcription polymerase chain reaction (RT-PCR) with IL-10 oligonucleotide primers. Cloning and sequencing of the RT-PCR product confirmed that it was of baboon IL-10 origin. Southern blot analysis showed that this IL-10 probe hybridized to a 7.9 Kbp or 8.6 Kbp band of baboon genomic DNA digested with Bam H1 or Eco R1, respectively. In situ hybridization with an antisense (Sal 1/T3) riboprobe derived from this sequence demonstrated that IL-10 mRNA was present in hepatic schistosome egg granulomas and in the spleen at post-acute infection.;Staining with fluorescent antibodies to intracellular IL-10 followed by flow cytometry was performed in this study to test for IL-10 dynamic expression in PBMC. IL-10 expression peaked in PBMC at the post-acute phase of primary infections with S. mansoni, but these periods of peak IL-10 expression shifted to an earlier stage of infection among the baboons exposed to secondary or more intense parasite infections.;A solid phase sandwich enzyme-linked immunosorbant assay (ELISA) was used to detect IL-10 in sera. Serum levels of IL-10 were low and peaked at week 5 to 10 in this study, during the post-acute stage of infection.;The results from biopsies, PBMC and sera indicate that IL-10 is expressed and peaks at a transitional stage from acute to post-acute schistosomiasis mansoni in the baboon. IL-10 may play important functions for amelioration of this disease.