Schistosome serine protease inhibitors: parasite defense or homeostasis?

Serpins are a structurally conserved family of macromolecular inhibitors found in numerous biological systems. The completion and annotation of the genomes of Schistosoma mansoni and Schistosoma japonicum has enabled the identification by phylogenetic analysis of two major serpin clades. S. mansoni shows a greater multiplicity of serpin genes, perhaps reflecting adaptation to infection of a human host. Putative targets of schistosome serpins can be predicted from the sequence of the reactive center loop (RCL). Schistosome serpins may play important roles in both post-translational regulation of schistosome-derived proteases, as well as parasite defense mechanisms against the action of host proteases.

Serpinas são uma família de inibidores macromoleculares estruturalmente conservados encontrados em inúmeros sistemas biológicos. O término e a anotação dos genomas de Schistosoma mansoni e de Schistosoma japonicum permitiram a identificação por análise filogenética de dois principais clados de serpinas. S. mansoni mostra uma multiplicidade maior de genes de serpinas, talvez refletindo uma adaptação à infecção de um hospedeiro humano. Alvos putativos das serpinas de esquistossomos podem ser preditos a partir da sequência do "loop" do centro reativo. Serpinas de esquistossomos podem ter importantes papeis tanto na regulação pós-traducional de proteases derivadas do esquistossoma, quanto nos mecanismos de defesa contra a ação de proteases do hospedeiro.

Esquistosomiasis japonicum en México: informe de un caso / Schistosomiasis japonicum in Mexico: report of a case

Paciente femenina de 20 años de edad con padecimiento de cinco meses de evolución caracterizado en su inicio por plenitud posprandial, dispepsia, mareos a los cambios bruscos de posición, diaforesis noctura, disnea de medianos esfuerzos y palpitaciones. Tres meses después, se agregó aumento de volumen abdominal a expensas de hipo y mesogastrio, acompañado de dolor difuso progresivo. Se practicó ultrasonografía bdominal en la que se observó gran masa tabicada desde hipogastrio hasta cicatriz umbilical con múltiples lesiones quísticas. El estudio coproparasitoscóspico mostró sangre oculta en heces y presencia de E. hystolitica, por lo que se inició tratamiento. Sin embargo, tres semanas más tarde se intensificaron los síntomas con datos de abdomen agudo. Se practicó laparotomía exploradora, y por hallazgos anatómicos se procedió a hemicolectomía izquierda y ooferectomía bilateral. El resultado histopatológico fue esquistosomiasis con fases superpuestas de depósitos de huevecillos y fibrosis severa; serositis y epiploítis con absceso; especie de esquistosoma por morfología S. Japonicum. Se administró tratamiento con prazicoantel a dosis de 40 mg/kg durante dos días, con lo que remitieron los síntomas. Se revisa el caso para determinar la procedencia del esquistosoma japonicum en esta zona y su importancia epideiológica.

Hepatosplenic lesions induced by experimental Schistosoma malayensis in rabbits.

Two groups of three rabbits each were infected with 250 cercariae of the Baling and Koyan strain of Schistosoma malayensis. Changes induced by both strains included periportal hepatocellular necrosis and fibrosis. Vascular changes such as portal phlebitis and thrombophlebitis and varying degrees of pericholangitis were also present. Amyloid deposition was noted. A comparative study of the changes induced in rabbits by S. malayensis, S. mekongi and S. japonicum showed that the hepatic lesions induced by the Baling strain of S. malayensis were similar to that induced by S. japonicum, and were more severe than that induced by S. mekongi or the Koyan strain.

Effects of cercarial concentration and length of exposure on the infection of mice by Schistosoma japonicum and S. mekongi cercariae.

The effects of cercarial concentration and length of exposure on the infection of mice by Schistosoma japonicum and S. mekongi were studied under laboratory conditions. For all cercarial concentrations of 10, 20 and 30, mice exposed for 1 min acquired little or no infection. Total worm recovery tended to rise with an increase either in cercarial concentration or exposure time. The highest infection rate and worm burden were obtained in mice exposed for 64 min to 30 cercariae per mouse. The present investigation suggested that exposures of 1 min or less carried little risk of infection at low cercarial concentration. There was a greater risk of infection in prolonged exposure to low cercarial concentration. Prolonged exposures to high cercarial concentration carried the greatest risk of high infection rate and worm burden.

Effects of physico-chemical factors on the infection of mice with Schistosoma japonicum and S. mekongi cercariae.

The three physico-chemical characteristics of water tested-pH, temperature and salinity were found to affect the infection of mice by cercariae of S. japonicum and S. mekongi. For both species of schistosomes, the range of optimal pH that showed highest infection and worm recovery rates was between 5.4-7.4 and decreased as the pH increased. Cercariae exposed to temperatures between 15 degrees-30 degrees C showed the highest infection and worm recovery rates. As temperature decreased or increased, the infection and worm recovery rates decreased. Sodium chloride concentration at low level (0.5-200 ppm) did not have great effect on the infection and worm recovery rates. The infection and worm recovery rates decreased as salinity increased. High sodium chloride concentration at 3200 ppm for S. mekongi cercariae and at 6400 ppm for S. japonicum cereariae inhibited cercarial penetration and no infection occurred.