Trichobilharzia regenti: Antigenic structures of intravertebrate stages

Abstract

Like several other bird schistosomes, neurotropic schistosome of Trichobilharzia regenti can invade also mammals, including humans. Repeated infections cause cercarial dermatitis, a skin inflammatory reaction leading to parasite elimination in non-specific mammalian hosts. However, in experimentally primo-infected mice, the worms escape from the skin and migrate to the central nervous system. In order to evade host immune reactions, schistosomes undergo cercaria/schistosomulum transformation accompanied with changes of surface antigens. The present study is focused on localization of the main antigens of T. regenti; cercariae, schistosomula developed under different conditions and adults were compared. Antigens were localized by immunofluorescence and ultrastructural immunocytochemistry using sera of mice repeatedly infected with T. regenti. Detected antibody targets were located in glycocalyx and penetration glands of cercariae and in tegument of cercariae, schistosomula and adults. Shedding of cercarial glycocalyx significantly reduced surface reactivity; further decrease was reported during ongoing development of schistosomula. Spherical bodies, probably transported from subtegumental cell bodies to worm surface, were identified as the most reactive tegumental structures. Based on similar results for schistosomula developed in specific, non-specific hosts and in vitro, it seems that the ability of T. regenti to decrease the surface immunoreactivity during ontogenesis is independent on the host type.

Nitric oxide and cytokine production by glial cells exposed in vitro to neuropathogenic schistosome Trichobilharzia regenti

“…Consequently, in order not to sacrifice excessive numbers of mice, LS for our stimulation experiments were prepared in vitro by mechanical transformation of cercariae. By this method, hundreds of schistosomulum-like stages resembling ex vivo schistosomula in terms of glycocalyx shedding, penetration glands emptying and immunoreactivity can be obtained [24, 32]. …”

“…Both tegumental antigens [32] and presumably parasite ESP are capable of triggering the host immune response. In this study, we demonstrated that in vitro LS induce only IL-6 secretion by exclusively astrocyte cultures.…”

Avian Schistosomes and Outbreaks of Cercarial Dermatitis

“…In the schistosome species studied so far, the glycocalyx is markedly rich in fucose residues (154,(196)(197)(198). There is an obvious loss of saccharide moieties at the surfaces of transformed schistosomula of T. szidati and T. regenti, leading to reduced immunoreactivity and attractiveness for fucose-specific lectins (154,155,199,200). Also, similar to the case for human schistosomes and members of other families of blood flukes, the trilaminar surface membrane of the outer cercarial tegument gradually changes to the doubled heptalaminar membrane of the schistosomulum, which has a protective function against the host immune system (199).…”

Antibody response of definitive hosts against antigens of two life stages of the neuropathogenic schistosome Trichobilharzia regenti

“…In particular, cercarial penetration glands as well as glycocalyx of T. regenti cercariae contained antigens triggering immune response. The latter reacted also with antibodies from human patients with known history of cercarial dermatitis and from mice experimentally infected with T. regenti ; a cross-reaction of antibodies has also been observed with heterologous antigens of the related species T. szidati and the human blood fluke Schistosoma mansoni [ 9 , 10 ]. The sera of compatible hosts recognised schistosomular and adult gut associated antigens [ 10 ].…”

“…Indeed, host antibody response is also directed towards other developmental stages that are in contact with the host. In addition to the antigens in glycocalyx, penetration glands and tegument of cercariae, also the tegument of schistosomula and adults is recognized by antibodies from infected mice [ 9 ].…”