Partial purification and characterization of cysteine proteinases from various developmental stages of Paragonimus westermani

Fifty years of the Korean Society for Parasitology

In 1959, the Korean Society for Parasitology was founded by clinical scientists, specialists of public health, and 5 core parasitologists with experience in American science and medicine. The Society this year celebrates its 50th anniversary. Due to public health importance at the time of foundation, medical parasitology was the main stream for next 3 decades. Domestic problems of niche parasitic diseases, unlisted in 6 tropical diseases of major importance, had been studied by own efforts. To cope with the demand of parasite control, evaluation system for control activity was built up. Control activity against soil-transmitted nematodes, conducted for almost 3 decades, was evaluated as a success. Evaluation of praziquantel efficacy for clonorchiasis, paragonimiasis, and neurocysticercosis, population dynamics of Ascaris lumbricoides infection in a situation of continuous reinfections, diagnostic modalities of antibody tests combined with brain imaging developed for helminthiasis of the central nervous system and researches on intestinal trematodes were achievements in the first 30 years. During the recent 2 decades, science researches, such as cell and molecular biology of parasites and immunology of parasitic infections have been studied especially on parasitic allergens and proteolytic and anti-oxidant enzymes. Experiences of international cooperation for world health have been accumulated and would be expanded in the future.

Paragonimiasis and the genus Paragonimus

The review concentrates on literature that has appeared since the 1960s. Since then, numerous species of Paragonimus have been described, mainly from Asia but also from Africa and the Americas. Some of these cause disease in humans. Recent information on life cycles and routes of transmission is summarized. All described species and their hosts are listed, with synonyms where known. For well-known species such as Paragonimus westermani, subspecific taxa and strains are reviewed and genetic studies discussed. Paragonimiasis in humans and experimental animals is discussed with emphasis on clinical manifestations and pathology, diagnosis, immune interactions with the host, treatment and public health issues.

Activities of different cysteine proteases of Paragonimus westermani in cleaving human IgG

Cleaving host immunoglobulins is a well known mechanism of evading host immune reactions exploited by helminth parasites. Secreted cysteine proteases of helminth are a part of enzymes cleaving host IgG. Paragonimus westermani produces at least six different species of the cysteine protease in its developmental stages. This study was undertaken to evaluate comparatively the activities against human IgG by the different enzymes. When the metacercariae, which secrete 27 and 28 kDa cysteine proteases, were incubated in human IgG solution, IgG was degraded at its hinge region. Further incubation resulted complete hydrolysis. From 4-week and 7-week old juveniles and 16-week old adults of P. westermani, five different enzymes at 15, 17, 27, 28 and 53 kDa have been purified, if the enzyme with the same molecular mass is regarded to be identical. In cleaving human IgG, each cysteine protease exhibited decreasing activities with age.

A cysteine protease of Paragonimus westermani eggs

Protease activity was identified in crude extracts of Paragonimus westermani eggs which were purified from infected dog lungs, isolated on 14 weeks after metacercarial challenge. The eggs were used after removing possibly contaminated host or worm tissues on their shell surfaces. In the crude egg extracts, high proteolytic activities against carboxybenzoyl-phenylalanyl-arginyl-4-methoxy-beta-naphthylamide (Cbz-phe-arg-MNA) and Azocoll were detected whereas those against succinyl-alanyl-prolyl- phenylalanyl-p-nitroanilide (Suc-ala-pro-phe-pNA) were not revealed. The enzyme exhibited the maximal activity at pH 6. Its activity was inhibited by specific cysteine protease inhibitors, 10(-5) M 1-trans-epoxysuccinylleucylamido (4-guanidino) butane (E-64) and 1 mM iodoacetamide (IAA) while potentiated by 6.5-fold in the presence of 2.5 mM dithiothreitol (DTT). When the enzyme was purified partially by Sephacryl S-300 High Resolution gel filtration, it migrated as a single homogeneous band at 35 kDa. The 35 kDa cysteine protease has been recognized neither in the metacercariae nor in the adult. These findings indicated the presence of at least one protease of cathepsin family in immature eggs of P. westermani.

Characterization of a cysteine proteinase from adult worms of Paragonimus westermani

Paragonimus westermani, the lung fluke, is known to migrate to the pulmonary tissue of mammalian hosts and causes pathological changes in the lungs. An acidic thiol-dependent proteinase with a molecular weight of approximately 20,000 daltons was purified to homogeneity using ion-exchange chromatography and gel filtration chromatography. On SDS-PAGE, the molecular weight of the enzyme was 17,500 daltons. Isoelectric point was 6.45. The enzyme was similar to the acidic cysteine proteinase of vertebrates in the properties of pH 5.5 for at least two days when stored at 4 degrees C. The cysteine proteinase was capable of degrading collagen and hemoglobin. Sera of patients with paragonimiasis and mice infected with P. westermani reacted in immunoblots with the partially purified proteinase. This result suggested that the cysteine proteinase of P. westermani may play a role in migration in tissues, and in acquisition of nutrients by parasites from the host. It is also potentially an antigen for the serodiagnosis of paragonimiasis.

Infectivity of Paragonimus westermani developing in a final host to another final host

In the definitive hosts, metacercariae of Paragonimus westermani excyst in host duodenum, penetrate intestinal wall, migrate peritoneal and thoracic cavities, and develop to sexual maturity in 8 weeks. This study was undertaken to examine the age of the maturing P. westermani when their infectivity to the other definitive hosts was retained. On 3, 7, 10, 14, 21 and 28 days after feeding the metacercariae to cats through a gastric tube, the developing worms were harvested. The juveniles of different age were fed again to other experimental cats. One to 12 weeks after the oral-transfer infections, the experimental cats were examined for establishment of infections. In the cats to which 3-day and 7-day old juveniles (grown up to 1.4 mm long) were fed, 31.4% and 22.6% of the transferred worms were found infected. The worms of 10-28 days old were not infective. Early maturing stages grown up to 7 days maintained their infectivity to the other definitive hosts.

Characterization of a peroxidase in excretory-secretory product of adult Paragonimus westermani

When activity of peroxidase in adult Paragonimus westermani was monitored using o-dianisidine and H2O2 as substrates, its specific activity was 1.5 times higher in excretory-secretory product (ESP) than in crude extract. The enzyme was purified by two purification steps of Sephacryl S-300 Superfine gel permeation and DEAE-Trisacryl M anion exchange chromatographies. Its activity increased 16.9 fold with 32.3% recovery. The enzyme was inhibited totally by 1 millimoles of dithiothreitol (DTT), 2-mercaptoethanol and azide. Molecular mass was 16 kDa in reducing SDS-polyacrylamide gel electrophoresis (PAGE) or 19 kDa in TSK-Blue gel filtration high performance liquid chromatography (HPLC), respectively. Special staining for peroxidase by diaminobenzidine on SDS-PAGE confirmed the activity. The peroxidase was less reactive to a paragonimiasis serum when observed by SDS-PAGE/immunoblot. In addition, specific activities of superoxide dismutase (SOD) and catalase were also identified in the ESP. High activities of these antioxidant enzymes in ESP indicate that they are parts of defense mechanisms against reactive oxygen intermediates from host.

Molecular weight of major component proteins in crude saline extract of adult Paragonimus westermani

When the component proteins in crude saline extract of 13-week old adult Paragonimus westermani were observed by non-denaturing discontinuous-polyacrylamide gel electrophoresis (Disc-PAGE), 8 distinct bands were clearly recognized. Molecular weight (MW) of each band protein, numbered in sequence from cathodal side which appeared in 10% separating gel, was measured first by Ferguson plot utilizing different gel concentrations from 10% to 4.5%. MW of band 1 protein (known as egg protein) was 440 kDa. And MW of other band proteins were: 386 kDa in band 2, 17.4 kDa in band 3, 17 kDa in band 4, 14.3 kDa in band 5, 46 kDa in band 6, 38 kDa in band 7 and 23 kDa in band 8. When the proteins in the crude extract were separated into fractions by molecular sieve chromatography through 1.6(phi) X 70 cm sized Sephacryl S-300 Superfine column and revisualized by Disc-PAGE in 8% gel, the sequence of eluted proteins was band 1, band 2, band 6, band 7 and bands 3, 4, 5 and 8. This elution profile confirmed MW of each band protein in the crude extract as measured by Ferguson plot.