Immunoprotection of mice against Schistosomiasis mansoni using solubilized membrane antigens

Schistosoma mansoni Adult Worm Protective and Diagnostic Proteins in n-Butanol Extracts Revealed by Proteomic Analysis

The S. mansoni adult worm n-butanol extract (Sm-AWBE) has been previously shown to contain specific S. mansoni antigens that have been used for immunodiagnosis of schistosomiasis in solid phase alkaline phosphatase immunoassay (APIA) and western blot (WB) analyses. Sm-AWBE was also used in immunoprotection studies against a fatal live-cercariae challenge in experimental mouse vaccination (~43% protection). The Sm-AWBE fraction was prepared by mixing adult worm membranous suspensions with aqueous-saturated n-butanol, centrifuging and recovering n-butanol-resistant proteins in the aqueous phase. Here we report a preliminary identification of Sm-AWBE protein components as revealed from a qualitative proteomic study after processing Sm-AWBE by 1D-gel electrophoresis, in-gel and in-solution tryptic digestions, and mass spectrometry analyses. We identified 33 proteins in Sm-AWBE, all previously known S. mansoni proteins and antigens; among them, immunomodulatory proteins and proteins mostly involved in host–parasite interactions. About 81.8% of the identified Sm-AWBE proteins are antigenic. STRING analysis showed a set of Sm-AWBE proteins configuring a small network of interactive proteins and a group of proteins without interactions. Functional groups of proteins included muscle contraction, antioxidant, GPI-anchored phosphoesterases, regulatory 14-3-3, various enzymes and stress proteins. The results widen the possibilities to design novel antigen combinations for better diagnostic and immunoprotective strategies for schistosomiasis control.

Immunization with adult Schistosoma mansoni tegument, treated with sub-curative praziquantel, partially protects mice against the infection

The tegument of schistosomes is a source of many potential anti-Schistosoma vaccine molecules. This work aimed to assess the protective effects of the adult Schistosoma mansoni tegument treated (TT) with sub-curative praziquantel (PZQ), whether in vivo (in vivo TT) or in vitro (in vitro TT), in murine schistosomiasis. In vitro TT and in vivo TT showed great similarity, and they differed from untreated tegument antigen (Teg) in terms of quantity and quality of protein bands on SDS-PAGE. Two immunization trials were performed, each with 50 mice, divided randomly into five groups of 10 mice each: (1) uninfected control mice (UC), (2) infected mice given phosphate buffer saline + adjuvant (PBS + adjuvant), (3) infected, Teg vaccinated, (4) infected, in vivo TT vaccinated, and (5) infected, in vitro TT vaccinated. All the immunizations with antigens induced mixed Th1/Th2 immune responses, as indicated by significantly high (P < 0.001) specific IgG2a and IgG1 levels, with Th1 predominating, as shown by a diminished IgG1/IgG2a ratio, as well as a high serum concentration of IFN-γ, an absence of IL-4 and increased IL-10. In vitro TT gave the most pronounced response. With respect to reduction of total worm burden, relative to PBS + adjuvant mice, in vitro TT achieved the highest significant (P < 0.001) results, followed by in vivo TT and Teg (51.8-57.04%, 44.6-50.2% and 35.2-39.3%, respectively). In scanning electron microscopy studies, all the tested antigens caused tegumental changes in adult worms, with the worst occurring with in vitro TT, such as retracted ventral sucker, an effect on the gynaecophoric canal, and changes to tubercles. In conclusion, in vitro TT, which is cheap to prepare, could be a potential vaccine against S. mansoni.

Protective capacity of cercarial transformation fluid alone or in combination with crude cercarial antigen against challenge infections of Schistosoma mansoni in mice

Schistosomiasis is the second major parasitic disease in the world after malaria. It affects 201.5 million cases in Africa alone. The aim of this research was to explore alternative vaccination strategies against experimental schistosomiasis mansoni. We assessed the effect of cercarial transformation fluid (CTF) singly and in combination with crude cercarial antigen (CCA) using alum as an adjuvant. The combined antigens gave the best results, as evidenced by a significant reduction in the worm load (62.07%), tissue egg count (78.16%, 86.46%) in liver and intestine respectively, and hepatic granuloma size (29.96%). Scanning electron microscopy revealed changes in the tegument, in the form of roughness and appearance of vesicles and furrows between the tegumental tubercles. Also, resorption of the ventral sucker and dimples replacing its spines were observed. The female tegument was irregular and its posterior end showed loss of spines and sensory bulbs. Moreover, there was a significant decrease in liver enzymes (alanine transaminase (ALT) and aspartate transaminase (AST)) compared to infected control mice. A significant elevation in CD4+T-lymphocytes, denoting amelioration of the immune status, in mice that received combined antigens was also observed. It can be concluded that combined antigens demonstrate potential as a vaccine against Schistosoma mansoni.

An invertebrate smooth muscle with striated muscle myosin filaments

Muscle tissues are classically divided into two major types, depending on the presence or absence of striations. In striated muscles, the actin filaments are anchored at Z-lines and the myosin and actin filaments are in register, whereas in smooth muscles, the actin filaments are attached to dense bodies and the myosin and actin filaments are out of register. The structure of the filaments in smooth muscles is also different from that in striated muscles. Here we have studied the structure of myosin filaments from the smooth muscles of the human parasite Schistosoma mansoni. We find, surprisingly, that they are indistinguishable from those in an arthropod striated muscle. This structural similarity is supported by sequence comparison between the schistosome myosin II heavy chain and known striated muscle myosins. In contrast, the actin filaments of schistosomes are similar to those of smooth muscles, lacking troponin-dependent regulation. We conclude that schistosome muscles are hybrids, containing striated muscle-like myosin filaments and smooth muscle-like actin filaments in a smooth muscle architecture. This surprising finding has broad significance for understanding how muscles are built and how they evolved, and challenges the paradigm that smooth and striated muscles always have distinctly different components.

Improvements and Variants of the Multiple Antigen Blot Assay-MABA: An Immunoenzymatic Technique for Simultaneous Antigen and Antibody Screening

This simple, versatile, reliable, reproducible, multipurpose, and inexpensive technique is based on the adhesion of different antigens to a single nitrocellulose strip using, as template, an acrylic device containing 28 parallel channels. The inclusion of channels containing normal human serum improves the quality control of this assay. Antigen-sensitized nitrocellulose strips are cut perpendicularly to the antigen-rows, exposed to immune sera followed by the appropriate conjugate. Positive signals are recorded using chemiluminescent or precipitable colorimetric substrates. This assay allows the simultaneous qualitative demonstration of antigenicity and immunogenicity of antigens obtained as synthetic peptides, recombinant molecules, or crude preparations, with high sensitivity and specificity. Its major value is based on the rapid and simultaneous comparative evaluation of various antigenic preparations allowing the diagnosis of a variety of infectious, allergic, and autoimmune diseases. It can in general be used to detect any type of antibody or circulating antigen. Some improvements and variants of the original technique are included.

Vaccination against helminth parasite infections

Helminth parasites infect over one fourth of the human population and are highly prevalent in livestock worldwide. In model systems, parasites are strongly immunomodulatory, but the immune system can be driven to expel them by prior vaccination. However, no vaccines are currently available for human use. Recent advances in vaccination with recombinant helminth antigens have been successful against cestode infections of livestock and new vaccines are being tested against nematode parasites of animals. Numerous vaccine antigens are being defined for a wide range of helminth parasite species, but greater understanding is needed to define the mechanisms of vaccine-induced immunity, to lay a rational platform for new vaccines and their optimal design. With human trials underway for hookworm and schistosomiasis vaccines, a greater integration between veterinary and human studies will highlight the common molecular and mechanistic pathways, and accelerate progress towards reducing the global health burden of helminth infection.