Immunization with cathepsin L proteinases CL1 and CL2 secreted by Fasciola hepatica elicit a preferential type 1 response based on IgG2a antibodies in rats

An update on proteases and protease inhibitors from trematodes

Trematodes, a class of parasitic flatworms, are responsible for a variety of devastating diseases in humans and animals, with schistosomiasis and fascioliasis being prominent examples. Trematode proteolytic systems involved in the host-parasite interaction have emerged as key contributors to the success of trematodes in establishing and maintaining infections. This review concentrates on diverse proteases and protease inhibitors employed by trematodes and provides an update on recent advances in their molecular-level characterization, with a focus on function, structure, and therapeutic target potential.

Immunization with the recombinant myosin regulatory light chain (FhrMRLC) in Adjuplex® adjuvant elicits a Th1-biased immune response and a reduction of parasite burden in Fasciola hepatica infected rats

The aim of this study was to assess the immune response and the protective efficacy elicited by the vaccination with the recombinant Fasciola hepatica myosin regulatory light chain (FhrMRLC) in Adjuplex® adjuvant against the infection with F. hepatica in rats. Four groups of 15 animals each were used for the study, one group was immunized with the recombinant F. hepatica MRLC in Adjuplex® adjuvant and the other groups remained as adjuvant, positive and negative control groups. The parasitological study showed that a statistically significant reduction of 65.1% and 82.1% in fluke burden and fecal egg count, respectively, was detected in vaccinated animals. In addition, vaccination with FhrMRLC induced a well-defined humoral and cellular immune response characterized by a significant production of specific IgG and IL-2, IL-12, TNF-α and IFN-γ; which confirms the immunogenic capacity of the FhrMRLC.

Juvenile-specific cathepsin proteases in Fasciola spp.: their characteristics and vaccine efficacies

Fasciolosis, caused by Fasciola hepatica and Fasciola gigantica, is one of the most neglected tropical zoonotic diseases. One sustainable control strategy against these infections is the employment of vaccines that target proteins essential for parasites' invasion and nutrition acquiring processes. Cathepsin proteases are the most abundantly expressed proteins in Fasciola spp. that have been tested successfully as vaccines against fasciolosis in experimental as well as large animals because of their important roles in digestion of nutrients, invasion, and migration. Specifically, juvenile-specific cathepsin proteases are the more effective vaccines because they could block the invasion and migration of juvenile parasites whose immune evasion mechanism has not yet been fully developed. Moreover, because of high sequence similarity and identity of cathepsins from juveniles with those of adults, the vaccines can attack both the juvenile and adult stages. In this article, the characteristics and vaccine potentials of juvenile-specific cathepsins, i.e., cathepsins L and B, of Fasciola spp. were reviewed.

Biochemical characterization and differential expression of a 16.5-kilodalton tegument-associated antigen from the liver fluke Fasciola hepatica

A cDNA encoding a 16.5-kDa protein termed FhTP16.5 was identified by immunoscreening of a cDNA library from Fasciola hepatica adult flukes using pooled sera from rabbits infected with F. hepatica for 4 weeks. Quantitative reverse transcriptase PCR (qPCR) analysis revealed that FhTP16.5 is not expressed in unembryonated eggs. It is poorly expressed in miracidia and highly expressed at the juvenile and adult stages; however, significant differences were found between the expression levels of FhTP16.5 in juveniles versus adult flukes. Recombinant FhTP16.5 was expressed at high levels in Escherichia coli, purified by affinity chromatography, and used to raise anti-FhTP16.5 polyclonal antibodies in rabbits. Immunoblot analysis using the anti-FhTP16.5 IgG antibody identified FhTP16.5 in crude and tegumental extracts and in excretory-secretory products of F. hepatica. The protein was not detected in crude extracts of Schistosoma mansoni or Schistosoma japonicum. Antibodies to FhTP16.5 were detected in the sera of rabbits at 3 to 12 weeks of F. hepatica infection as well as in the sera of humans with chronic fascioliasis; these findings suggest that FhTP16.5 could be a good antigen for serodiagnosis of fascioliasis. Immunohistochemistry demonstrated that FhTP16.5 localizes to the surface of the tegument of various developmental stages and in parenchymal tissues of the adult fluke. Such specific localization makes FhTP16.5 an attractive target for immunoprophylaxis or chemotherapy.