Schistosoma mansoni: anti-SMw32 proteinase response in vaccinated and challenged baboons

An immunological and biochemical comparison of hookworm species

The successful development of diagnostic tests capable of distinguishing human hookworm species will ultimately depend on an increase in our knowledge of their comparative biochemistry. Here, David Pritchard, Paul McKean and Gerry Schad describe some aspects of the comparative biochemistry of Necator americanus and Ancylostoma duodenale, and emphasize differences between the species that could form the basis of discriminatory diagnostic tests.

Diagnostic significance of Schistosoma mansoni proteins Sm31 and Sm32 in human schistosomiasis in an endemic area in Egypt

We performed a series of ELISAs to evaluate the diagnostic significance of two Schistosoma mansoni proteins, Sm31 (cysteine proteinase, cathepsin B) and Sm32 (asparaginyl endopeptidase). Our study populations were chosen from two villages in an endemic area close to Alexandria. Using fusion proteins MS2-Sm31 and MS2-Sm32 as antigens, 70% and 78.9%, respectively, of patient sera from 134 parasitologically confirmed cases reacted positively. The percentage of seropositivity increased to 84.5% when parasite-derived proteins Sm31 and Sm32 were used. The serum levels of antibodies to these two proteins in recombinant or native forms do not correlate with intensity of infection and hence are detected even when egg counts are low, which makes proteins Sm31 and Sm32 useful antigens in the identification of S. mansoni infected cases, particularly in endemic areas in Egypt.

Immunodiagnosis of fasciolosis in ruminants using a 28-kDa cysteine protease of Fasciola gigantica adult worms

A homogeneous extract of a 28-kDa cysteine protease of Fasciola gigantica adult worms was used as the antigen for immunodiagnosis of fasciolosis in cattle, sheep and goats using the Falcon assay screening test enzyme-linked immunosorbent assay technique. This antiprotease assay technique was found to be very rapid and sensitive and may be useful as a supplementary method for the diagnosis of fasciolosis in ruminants.

Development and characterization of a monoclonal antibody reactive with a 28 kDa protease of Fasciola gigantica

A monoclonal antibody that was reactive with a 28-kDa protease of Fasciola gigantica was produced after hyperimmunizing BALB/c mice with a partially purified extract and a purified 28-kDa protease obtained from the fluke. Isotype analysis showed that the immunoglobulin is IgG3. Seven other monoclonals of isotypes IgG1, IgG2 and IgG3 which reacted with the protease and one to three other protein bands were also produced. In addition, four other clones of hybridoma produced antibodies which recognised a 27/28-kDa protein doublet but the 28-kDa component of this doublet was different from the 28-kDa protease. The reactivities and characteristics of the monoclonal antibodies were studied by enzyme-linked immunosorbent assay (ELISA), immunoblotting and immunoprecipitation tests.

Proteinases of Trichomonas vaginalis: antibody response in patients with urogenital trichomoniasis

Immunoprecipitation combined with electrophoresis in gelatin-polyacrylamide gels was successfully used for detection of antibodies against numerous proteinases of Trichomonas vaginalis in infected patients. The method proved to be highly specific as anti-proteinase antibodies were absent in women with negative cultivation of T. vaginalis and no history of trichomoniasis. Sera of 71% and vaginal washes of 86% patients with trichomoniasis were positive for these antibodies. In vaginal washes, but not in sera, antibodies were partly complexed with proteinases, possibly of trichomonad origin. It was also shown that serum antibodies as well as local anti-proteinase antibodies persisted for weeks after patients had been cured.

The purification and characterization of a cysteine protease of Fasciola gigantica adult worms

A 26-28 kDa protease was isolated from Fasciola gigantica adult worms by a two-stage purification process of column chromatography in a Sephacryl S-200 column and affinity chromatography in an L-phenylalanine-agarose column. This protease is a cysteine (thiol) proteinase with an optimum pH of 4.5 and is not inhibited by anti F. gigantica immunoglobulin G. The enzyme was inhibited by protease inhibitors known to inhibit cysteine proteases but not by metallo-, aspartate or serine protease inhibitors. The effect of several protease inhibitors and anti-F, gigantica IgG was also assessed on the total proteolytic activity of F. gigantica. There appears to be a preponderance of cysteine protease activity in F. gigantica and there was a significant inhibition of total proteolytic activity by anti-F. gigantica IgG.

Partial purification and characterisation of the proteolytic enzymes of Fasciola gigantica adult worms

The proteases of adult Fasciola gigantica whole worm were analysed by preparative isoelectric focusing and by gelatin-substrate gel electrophoresis at acidic and neutral pH (4.5 and 7.0). At least 15 bands of proteases were observed. These proteases had molecular weights ranging from 26 to 193 kDa and isoelectric points of 4.92-7.63. Protease-rich fractions were subsequently separated from whole worm preparation of the parasite by filtration in Sephacryl S-200. The proteases were able to digest bovine immunoglobulin G (IgG) and globin (derived from bovine haemoglobin) in vitro. The sizes of the proteases in these fractions were from 26 to 96 kDa, and they were inhibited by the protease inhibitors phenylmethylsulphonyl fluoride (PMSF), leupeptin and trasylol.

Primary structures of Sm31/32 diagnostic proteins of Schistosoma mansoni and their identification as proteases

We have constructed cDNA clones containing the complete nucleotide sequences coding for two highly antigenic Schistosoma mansoni adult worm proteins, Sm31 and Sm32. The predicted amino acid sequence of Sm31 shows significant homology to mouse, rat and human cathepsin B. The nucleotide sequence of Sm32 is identical to that reported by others for S. mansoni "haemoglobinase'. The different nucleotide sequences demonstrate the existence of two different proteolytic enzymes, both of which are synthesised in the form of precursor molecules. Structural homology of the schistosome cathepsin B to the mammalian ones indicates that the mature protein is processed from a propeptide. The calculated molecular weight of haemoglobinase of 47,000 suggests that post-translational processing is also involved in generating an active protease.

Cloned Schistosoma mansoni proteinase (hemoglobinase) as a putative serodiagnostic reagent

Expressed cDNA encoding a proteolytic enzyme from Schistosoma mansoni has been cloned recently. Circulating antibodies reacting with the recombinant protein have been detected in the blood of mice and humans infected with S. mansoni, S. japonicum, or S. haematobium. S. mansoni and S. haematobium infection can be distinguished by antibody titer.

Schistosome proteases

While studies of schistosome antigens have proceeded rapidly over the past ten years, studies of schistosome enzymes have also been increasing apace. Now the two `lines' of research are coming together. Parasites such as schistosomes hardly present antigens merely to stimulate a host immune response, so it is not surprising that many antigens turn out to have functions, for example, as enzymes. One type of antigenic schistosome enzyme - glutathione S-transferase - already shows promise as a vaccine candidate. Here, Jim McKerrow and Mike Doenhoff review another important class of enzyme, many of which are clearly antigenic, the schistosome proteases.