Selecting targets for the diagnosis of Schistosoma mansoni infection: An integrative approach using multi-omic and immunoinformatics data

Abstract

In order to effectively control and monitor schistosomiasis, new diagnostic methods are essential. Taking advantage of computational approaches provided by immunoinformatics and considering the availability of Schistosoma mansoni predicted proteome information, candidate antigens of schistosomiasis were selected and used in immunodiagnosis tests based on Enzime-linked Immunosorbent Assay (ELISA). The computational selection strategy was based on signal peptide prediction; low similarity to human proteins; B- and T-cell epitope prediction; location and expression in different parasite life stages within definitive host. Results of the above-mentioned analysis were parsed to extract meaningful biological information and loaded into a relational database developed to integrate them. In the end, seven proteins were selected and one B-cell linear epitope from each one of them was selected using B-cell epitope score and the presence of intrinsically disordered regions (IDRs). These predicted epitopes generated synthetic peptides that were used in ELISA assays to validate the rational strategy of in silico selection. ELISA was performed using sera from residents of areas of low endemicity for S. mansoni infection and also from healthy donors (HD), not living in an endemic area for schistosomiasis. Discrimination of negative (NEG) and positive (INF) individuals from endemic areas was performed using parasitological and molecular methods. All infected individuals were treated with praziquantel, and serum samples were obtained from them 30 and 180 days post-treatment (30DPT and 180DPT). Results revealed higher IgG levels in INF group than in HD and NEG groups when peptides 1, 3, 4, 5 and 7 were used. Moreover, using peptide 5, ELISA achieved the best performance, since it could discriminate between individuals living in an endemic area that were actively infected from those that were not (NEG, 30DPT, 180DPT groups). Our experimental results also indicate that the computational prediction approach developed is feasible for identifying promising candidates for the diagnosis of schistosomiasis and other diseases.

A novel synthetic peptide microarray assay detects Chlamydia species-specific antibodies in animal and human sera

“…The idea of using synthetic peptides derived from immunological determinants to specifically capture cognate antibodies emerged more than a decade ago 13 – 15 . A number of studies investigating antibody responses to bacterial 16 , 17 , viral 18 – 21 and parasite 22 – 24 infections in humans and animals have been published. In Chlamydia research, the major outer membrane protein OmpA or MOMP was the first antigen molecule to be systematically investigated for its immunogenic capacity, and peptides derived from its epitopes were used as capture antigens in a number of studies.…”

Serological proteomic screening and evaluation of a recombinant egg antigen for the diagnosis of low-intensity Schistosoma mansoni infections in endemic area in Brazil

“…Diagnosis using antibodies [37, 45, 46], antigens [65, 66] or DNA [8, 16, 67] show high sensitivity, but reduced specificity compared to egg-based methods [7, 14, 48]. Improvements on immunoassays have been the most studied aspect of mapping, due to promising ability to detect individuals with low-intensity infections undiagnosed by standard KK [29, 37, 45, 65, 66, 68–70]. In addition, they have paved the way for less laborious rapid tests that are useful both in communities in endemic areas and at point-of-care facilities [66, 71].…”

Diagnosis of Schistosoma mansoni infections: what are the choices in Brazilian low-endemic areas?

“… 70 , 81 , 82 Given these limitations, antibody-based detection methods are not currently the first choice for endemic areas; however, the determination of immunoreactivity against different schistosome antigens can identify infections with loads as low as 1 EPG. 24 , 68 , 83 , 84 , 85 , 86 This fact had led to the introduction of these methods as a complementary tool during epidemiological surveys in low-endemic areas. Its use decreases false-negative cases seen when few K-K slides are applied in conditions of low egg excretion.…”

“… 92 Pooled synthetic peptides were tested as antigens in ELISA using samples from Brazilian endemic individuals, and these provided a sensitivity of 86.8% and a specificity of 94.2%. 84 Carvalho et al, 85 using computational tools, selected and produced seven synthetic peptides that were then tested in ELISA against endemic human sera and exhibited specificities of 46.15% to 100%, while sensitivities varied from 53.85% to 96.15%.…”