The anterior esophageal region of Schistosoma japonicum is a secretory organ

Abstract

BackgroundThe esophagus of blood-feeding schistosomes has been largely neglected although its posterior portion was designated as a gland decades ago. However, we recently showed it plays a pivotal role in blood processing. It is clearly demarcated into anterior and posterior compartments, both surrounded by a mass of cell bodies. Feeding movies revealed that erythrocytes accumulate in the anterior compartment before entering the posterior, indicating that a distinct process is executed there. We therefore investigated ultrastructural aspects and possible functions of the anterior region.MethodsThe heads of adult Schistosoma japonicum were detached and prepared for both transmission and scanning electron microscopy to define the detailed ultrastructure of the anterior esophagus. Cryosections of heads were also prepared for immunocytochemistry and confocal microscopy to define the pattern of intrinsic host antibody binding in the anterior esophageal lining.ResultsThe anterior syncytial lining of the esophagus is highly extended by long, thin corrugations of cytoplasm projecting towards the lumen. Strikingly in the male worm, the tips of the corrugations are further expanded by numerous threads of cytoplasm, producing a spaghetti-like appearance in the central lumen. Flattened, pitted cytoplasmic plates are interspersed in the tangled mass of threads. Abundant, morphologically distinct light vesicles of varied size and contents are manufactured in the cell bodies, from where they traffic through cytoplasmic connections to the corrugations and out to the tips. Clusters of vesicles accumulate in expanded tips in males, together with occasional mitochondria whilst females have more mitochondria but fewer vesicles. The membranous contents of light vesicles are secreted mainly from the tips, but also from the sides of the corrugations. They coat the surfaces and then form organised self-adherent membrane figures when shed into the lumen. Host antibody binds strongly in a characteristic pattern to the anterior esophageal lining indicating that the secretions are highly immunogenic.ConclusionsWe suggest that the anterior esophageal region is an independent secretory organ. The contents of light vesicles are released into the esophageal lumen via the tips of corrugation to interact with incoming blood. Our immediate task is to establish their composition and role in blood processing.

Evidence That Rhesus Macaques Self-Cure from a Schistosoma japonicum Infection by Disrupting Worm Esophageal Function: A New Route to an Effective Vaccine?

“…To detect the presence of host antibodies, permeabilized worms recovered from macaques were incubated with FITC-labelled rabbit anti-monkey IgG (H+L;Sigma-Aldrich, Poole, UK for two days at 4°C and given extensive washes in AbD before viewing. To explore details of intrinsic bound antibody in the esophageal lumen, worm head cryosections were prepared as described by Li et al [ 18 ] and reacted with 1:100 dilution of FITC- labelled rabbit-anti monkey IgG. The musculature and nuclei were visualized by staining of f-actin with a 1:100 dilution of AF555-conjugated phalloidin (Invitrogen, Molecular Probes) plus 4',6-diamidino-2-phenylindole (DAPI; diluted in 1:600 in 10% Normal Goat serum in PBS; Sigma-Aldrich, Poole, Dorset, UK), respectively, for 30 minutes.…”

“…The structure of the esophageal region in representative worms from self-cured rhesus macaques, showing little or no gut pigment, was examined by TEM and SEM exactly as described by Li et al [ 18 ].…”

“…The posterior region is surrounded by a gland and, in S . japonicum at least, the anterior esophageal region is also a morphologically distinct secretory organ [ 18 ]. Very little is known about the products of these two glands, in part due to their minute size.…”

Caracterização molecular de proteínas secretadas da família VAL (Venon Allergen-Like Protein) de <i>Schistosoma mansoni</i> e avaliação como antígenos vacinais.

“…O ensaio de Western Blot pode não ter funcionado para estas proteínas por estarem na região anterior dos vermes, concentradas numa área pequena (glândula esofágica anterior) formada por poucas células, aproximadamente 700 células nos machos e um pouco menos nas fêmeas (LI et al, 2014), em comparação ao restante do corpo e aos outros órgãos, como testículos e ovários que ocupam grande volume do corpo dos vermes adultos. No caso das proteínas de cercárias, as glândulas acetabulares constituem 2/3 do volume do corpo dos parasitas deste estágio (DORSEY et al, 2002) e por isso, seu conteúdo é abundante e mais fácil de ser detectado.…”

“…Já a SmVAL7 (utilizada como controle positivo) pôde ser identificada uma vez que é secretada pela glândula esofágica posterior durante o processo de alimentação sanguíneo que ocorre somente quando os parasitas chegam ao fígado (aproximadamente 21 dias após infecção) )Também não foi possível localizar as proteínas nativas de vermes adultos por Imunohistoquímica. Nesse caso, uma explicação para este resultado seria o fato das proteínas nativas SmVAL 13 e 14 estarem na glândula esofágica anterior e em menor abundância do que a SmVAL7, participando dos processos iniciais da alimentação pelos parasitas, e, dessa forma, secretadas antes do que a SmVAL7, localizada na glândula esofágica posterior (LI et al, 2013;LI et al, 2014;ROFATTO et al, 2012).…”