BackgroundSchistosomiasis remains one of the most common endemic parasitic diseases affecting over 230 million people worlwide. Schistosoma mansoni is the main species causing intestinal and hepatic schistosomiasis and the fresh water pulmonate snails of the genus Biomphalaria are best known for their role as intermediate hosts of the parasite. The development of new molecular monitoring assays for large-scale screening of snails from transmission sites to detect the presence of schistosomes is an important point to consider for snail control interventions related to schistosomiasis elimination. Our work was focussed on developing and evaluating a new LAMP assay combined with a simple DNA extraction method to detect S. mansoni in experimentally infected snails as a diagnostic tool for field conditions.Methodology/Principal findingsA LAMP assay using a set of six primers targeting a sequence of S. mansoni ribosomal intergenic spacer 28S-18S rRNA was designed. The detection limit of the LAMP assay was 0.1 fg of S. mansoni DNA at 63°C for 50 minutes. LAMP was evaluated by examining S. mansoni DNA in B. glabrata snails experimentally exposed to miracidia at different times post-exposure: early prepatent period (before cercarial shedding), light infections (snails exposed to a low number of miracidia) and detection of infected snails in pooled samples (within a group of uninfected snails). DNA for LAMP assays was obtained by using a commercial DNA extraction kit or a simple heat NaOH extraction method. We detected S. mansoni DNA in all groups of snails by using no complicated requirement procedure for DNA obtaining.Conclusions/SignificanceOur LAMP assay, named Biompha-LAMP, is specific, sensitive, rapid and potentially adaptable as a cost-effective method for screening of intermediate hosts infected with S. mansoni in both individual snails and pooled samples. The assay could be suitable for large-scale field surveys for schistosomes control campaigns in endemic areas.

Schistosomiasis is a significant public health problem in sub-Saharan Africa, China, Southeast Asia, and regions of South and Central America affecting about 189 million people. Kunitz-type serine protease inhibitors have been identified as important players in the interaction of other flatworm parasites with their mammalian hosts. They are involved in host blood coagulation, fibrinolysis, inflammation, and ion channel blocking, all of them critical biological processes, which make them interesting targets to develop a vaccine. Here, we evaluate the protective efficacy of chemically synthesized T- and B-cell peptide epitopes derived from a kunitz protein from Schistosoma mansoni. Putative kunitz-type protease inhibitor proteins were identified in the S. mansoni genome, and their expression was analyzed by RNA-seq. Gene expression analyses showed that the kunitz protein Smp_147730 (Syn. Smp_311670) was dramatically and significantly up-regulated in schistosomula and adult worms when compared to the invading cercariae. T- and B-cell epitopes were predicted using bioinformatics tools, chemically synthesized, and formulated in the Adjuvant Adaptation (ADAD) vaccination system. BALB/c mice were vaccinated and challenged with S. mansoni cercariae. Kunitz peptides were highly protective in vaccinated BALB/c mice showing significant reductions in recovery of adult females (89–91%) and in the numbers of eggs trapped in the livers (77–81%) and guts (57–77%) of mice. Moreover, liver lesions were significantly reduced in vaccinated mice (64–65%) compared to infected control mice. The vaccination regime was well-tolerated with both peptides. We propose the use of these peptides, alone or in combination, as reliable candidates for vaccination against schistosomiasis.

Schistosoma mansoni is less susceptible to the antiparasitic drug ivermectin than other helminths. By inhibiting the P-glycoprotein or cytochrome P450 3A in mice host or parasites in a murine model, we aimed at increasing the sensitivity of S. mansoni to the drug and thus preventing infection. We assigned 124 BALB/c mice to no treatment, treatment with ivermectin only or a combination of ivermectin with either cobicistat or elacridar once daily for three days before infecting them with 150 S. mansoni cercariae each. The assignment was done by batches without an explicit randomization code. Toxicity was monitored. At eight weeks post-infection, mice were euthanized. We determined number of eggs in intestine and liver, adult worms in portal and mesenteric veins. Disease was assessed by counting granulomas/cm2 of liver and studying organ weight indices and total weight. IgG levels in serum were also considered. No difference between groups treated with ivermectin only or in combination with cobicistat or elacridar compared with untreated, infected controls. Most mice treated with ivermectin and elacridar suffered severe neurological toxicity. In conclusion, systemic treatment with ivermectin, even in the presence of pharmacological inhibition of P-glycoprotein or cytochrome P450 3A, did not result in effective prophylaxis for S. mansoni infection in an experimental murine model.

Schistosomiasis is a parasitic disease that affects 143 million people in endemic countries. This work analyzed overexpressed sequences from the cercaria phase to the early schistosomulum phase using bioinformatics tools to predict host interaction and selected proteins for predicting T cell epitopes. The final peptides were chemically synthesized, and their toxicity was evaluated in vitro. Peptides were formulated in the Adjuvant Adaptation (ADAD) vaccination system and injected into BALB/c mice that were challenged with S. mansoni cercariae to assess protection and immunogenicity. A total of 39 highly expressed S.mansoni proteins were identified as being of potential interest. Three T cell peptides predicted to bind MHC mouse and human class II were synthesized and formulated for vaccination. SmGSP and SmIKE reduced the number of eggs trapped in the liver by more than 50% in challenged BALB/c mice. The liver of mice vaccinated with either SmGSP or SmTNP had a significantly reduced affected liver surface. Transcriptome-based T cell peptides elicit partial protection and could be candidates for a multiantigen vaccine.

High levels of infection and severe liver fibrosis in schistosomiasis appear only in a few cases of infected people with high susceptibility. Tissue damage is caused by the inflammatory response to eggs trapped in the liver. The genetic background influences susceptibility to schistosome infection. To assess the genetic basis of susceptibility to schistosomiasis and identify the chromosomic regions involved, we used a backcross strategy to generate a mouse cohort with high variation in schistosomiasis susceptibility. Thus, we crossed the resistant C57BL/6 mouse strain with the susceptible CBA one; and later; the F1 females (C57 x CBA) were backcrossed with CBA males generating the F1BX cohort. The spectrum of phenotypes in the F1BX mice showed gradation from mild to severe disease, lacking a fully resistant group. We differentiated four levels of infection intensity using cluster and principal component analyses and K-means based on parasitological, pathological and immunological trait measurements. Mice were massively genotyped with 961 informative SNPs. We identify 19 new quantitative trait loci (QTL) associated with phenotype indicators of parasite burden, liver lesion, white blood cell populations, and antibody responses evaluated in the backcross cohort. Two QTLs on chromosomes 15 and 18 were simultaneously linked to the number of granulomas, grade of liver lesion and IgM levels. The human syntenic regions are located in chromosomes 8 and 18. None of the significant QTL identified coincided with previously reported mice association or were syntenic with human chromosomes.Author summaryHigh number of cases of infection and high levels of infection and liver fibrosis in schistosomiasis appear only in a few cases of people with high susceptibility, because the genetic background influences this susceptibility. To assess this, we used a backcross strategy crossing a resistant strain of mouse C57BL/6 with another susceptible CBA, and later F1 females were backcrossed with males susceptible, generating the F1BX cohort, which showed gradation from mild to severe disease. We differentiated four levels of infection according to cluster, principal component analysis and K-means, and based on parasitological, pathological and immunological measurements. Mice were massively genotyped and 19 quantitative trait loci (QTL) were identified, associated with phenotype indicators evaluated in backcross cohort. Two QTLs on chromosomes 15 and 18 were simultaneously linked to the number of granulomas, grade of liver lesion and IgM levels. None of the significant QTL identified coincided with previously reported mice association or were syntenic with human chromosomes.

Schistosomiasis is a significant public health problem in sub-Saharan Africa, China, South-East Asia and regions of South and central America affecting about 189 million people. Kunitz-type serine protease inhibitors have been identified as important players in the interaction of other flatworm parasites with their mammalian hosts. Here, we evaluate the protective efficacy of chemically synthesized of T- and B-cell peptide epitopes derived from a kunitz protein from Schistosoma mansoni. Putative kunitz-type protease inhibitor proteins were identified in the S. mansoni genome and their expression analyzed by RNA-seq. Gene expression analyses showed that the kunitz protein Smp_147730 (Syn. Smp_311670) was dramatically and significantly up-regulated in schistosomula and adult worms when compared to the invading cercariae. T- and B-cell epitopes were predicted using bioinformatics tools, chemically synthesized and formulated in the Adjuvant Adaptation (ADAD) vaccination system. BALB/c mice were vaccinated and challenged with S. mansoni cercariae. Kunitz peptides were highly protective in vaccinated BALB/c mice showing significant reductions in recovery of adult females (89-91%), and in the numbers of eggs trapped in the livers (77-81%) and guts (57-77%) of mice. Moreover, liver lesions were significantly reduced in vaccinated mice (64-65%) compared to infected control mice. The vaccination regime was well tolerated with both peptides. We propose the use of these peptides, alone or in combination, as reliable candidates for vaccination against schistosomiasis.