Evagination of Taenia solium cysticerci: a histologic and electron microscopy study.

BACKGROUND: After a human being ingests a cysticercus, the larval stage of Taenia solium, the cysticercus gradually develops toward the adult parasite. In this paper, we describe the sequential progress of evagination of cysticerci. METHODS: Intact cysticerci were obtained from swine muscle, and incubated in bovine bile to stimulate evagination. Dissecting, light, and electron microscopy of whole parasites and histologic sections were used for photographic registers. RESULTS: The first event was the widening of the opening of the bladder wall for the scolex and neck to emerge. The two chambers that conform the cysticercus were identified. Histologic sections provided explanation for the conformation of the spiral canal. The scolex uncoils during evagination but does not turn inside out. CONCLUSIONS: The scolex and the neck comprise a different structure from the bladder wall, although they are contiguous.

Praziquantel treatment of muscle Taenia solium cysticercosis. 4. Reversible in vitro effect.

The in vitro effect of Praziquantel (PZQ) on Taenia solium cysticerci was analyzed. The oxygen consumption rate of the parasites was inhibited and the release of proteins was enhanced, but no statistically significant differences were found between the control group and the experimental groups. The drug had a significant, dose-dependent negative effect on the evagination ability of the larvae; 50% effect was seen at concentrations of between 10(-9) and 10(-8) M PZQ. The drug also induced morphological disturbances in the tegument of the worm and of the bladder wall. Finally, a very drastic effect was the induction of spastic paralysis in evaginated cysticerci at high drug doses and of flaccid paralysis at lower PZQ concentrations. The dose inducing these effects was various orders of magnitude lower than that inhibiting the evagination ability of intact cysts. Moreover, the latter effect was reversible after had been washed out the drug and the parasites had been cultured. We suggest that PZQ alters the Ca2+ flux in T. solium as it does in other helminths. Furthermore, we corroborated the protective role of the bladder for the invaginated worm. Finally, we think that in vivo the drug must act synergistically with the immune system components so as to eliminate the parasite.

What is the significance of the presence of MHC molecules on the surface of parasites in human neurocysticercosis?

Sixteen cysticerci excised from 15 surgery patients were examined for the presence of HLA molecules on their surface, to confirm the role of these molecules in parasite damage and to investigate if HLA products are host specific or perhaps host-like antigens synthesized by the parasite. MoAbs against monomorphic and polymorphic HLA were chosen according to the patients HLA phenotypes. MoAbs against host and non-host antigens were selected and tested on cyst slides by indirect immunofluorescence assays. Host molecules were present in 43.7% of the cysts, but non-host antigens were also apparent in 62.5%. These results suggest mimicry as a possible mechanism to explain the presence of MHC products on the surface of the parasite; inflammation may also induce the expression of HLA that could become associated with the parasite. In vitro cellular immune response to specific antigens was also performed and positive responses correlated with the presence of HLA molecules on the cyst's surface. Moreover, damaged parasites had host molecules as well. Parasites from responder patients had all kind of HLA molecules or at least, antigenic determinants while the cysts from non-responders did not have molecules on their surface. These data support the role of HLA in cyst destruction.

Taenia crassiceps: experimental model of intraocular cysticercosis.

An experimental model of Taenia crassiceps intraocular cysticercosis was developed in rabbits. The objectives of this study were to analyze the pathophysiology of this parasitic infection and to evaluate the humoral immune response. Cysticerci, inoculated in the anterior chamber of the eye, were able to grow; no inflammatory changes in the eye or anticysticercus antibodies in serum or in aqueous humor were detected during the 12-day period. In contrast, rabbits that had previously been either infected intraperitoneally with living T. crassiceps cysts or immunized intramuscularly with T. crassiceps antigenic extract developed an intense inflammatory reaction in the eye and high levels of antibodies were detected in serum and aqueous humor even before the intraocular inoculation of parasites. Furthermore, intraocular cysticerci showed minimal growth and some were eliminated. These findings support the concept that the eye is an immunologically privileged site in the nonimmunized host and the importance of the immune response in the elimination of this parasitic infection.

Morphological types of Taenia solium cysticerci.

In human brain cysticercosis, there are three morphological types of cysticercus. Teresa Robielo, Angelica Rivas and Ana Flisser describe the appearance and possible taxonomic position of these forms, and discuss their relation to the various pathologies of neurocysticercosis.

Heterogeneity of humoral immune components in human cysticercosis.

Twelve Taenia solium cysticerci, obtained from several human organs, were examined by immunofluorescence for IgG, IgM, IgA, IgE and C3b on their surfaces. Anti-cysticercus antibodies of the 4 classes of immunoglobulins were looked for in the cerebrospinal fluid of most neurologic patients, in the intraocular humors of a patient with eye cysticercosis, and in the serum of some other patients. The morphological appearance of the parasites as well as the clinical features of the patients were recorded. The distribution of components was heterogeneous among the different parasite surfaces. IgG was the most frequent, followed by IgA, IgM, C3b and IgE. No correlation was found between the presence of these molecules and signs of damage in the cysticerci, or with the classes of immunoglobulins found as anti-cysticercus antibodies. Possible explanations of these findings as well as the implications of heterogeneity in cysticercosis are discussed.

Vestibular and oculomotor abnormalities in vertebrobasilar insufficiency.

The early diagnosis of vertebrobasilar insufficiency in patients with vertigo as their only symptom was attempted using a battery of vestibulo-oculomotor tests. With this testing procedure, we were able to find abnormal vestibulo-oculomotor mechanisms that could account for the vertigo in 41 of 42 patients. These abnormalities, however, did not fall into an easily recognizable pattern that could be considered characteristic of vertebrobasilar insufficiency. The large intersubject variability probably arises from the very different and widespread lesions that occur at the vestibular and neurological levels as a consequence of vertebrobasilar insufficiency.