Lytic effects of normal serum on isolated postonchospheral and metacestode stages of Taenia taeniaeformis

Postonchospheral stages of Taenia taeniaeformis liberated from rat livers by enzymatic digestion at 1 to 10 days postinfection (DPI) and metacestodes dissected from infected livers at 22, 34, and 69 DPI were exposed in vitro to immune rat serum (IRS) and to normal serum from rats (NRS), human beings (NHS), or guinea pigs (NGS). The onset of rapid and destructive tegumental changes in all organisms exposed to any of the sera was demonstrated to be complement-dependent because the reaction was: (a) inhibited by treatment of serum at 56 C for 30 min; (b) inhibited by prior incubation of serum with zymosan or with complement-fixing, soluble products derived from larvae of T. taeniaeformis maintained in vitro (IVP); and (c) abolished by the addition of EDTA. Lytic effects occurred on exposure to agammaglobulinemic sheep serum, and lysis in the presence of IRS and NRS was shown to result in consumption of available hemolytic complement. Surface changes consisted of vesiculation in the microvillar or microthrix layers followed by sloughing of the tegument, eventually leading to collapse of the cystic bladder and cessation of flame cell activity, or, in the case of early postonchospheral forms, complete disintegration of the organism. When IVP was added to NHS, reduction of hemolytic complement activity was associated with the electrophoretic conversion of C3, and Factor B, but there was little or no consumption of C1. The observations support the hypothesis that complement-mediated effector mechanisms must be counteracted to ensure survival of parasites in vivo, and that the capacity for release of soluble nonspecific complement-fixing factors by taeniid larvae may have an important role to play in this process.     

Taenia taeniaeformis: evasion of complement-mediated lysis by early larval stages following activation of the alternative pathway

Activation of the alternative pathway of complement by T. taeniaeformis oncospheres and early stage metacestodes, although a factor in host defense against primary infection, does not directly lead to the killing of the parasite larvae observed prior to day 6 post-infection in innately resistant BALB/cByJ inbred mice. Immunogold labelling techniques clearly demonstrated tegument-associated C3 on in vitro-activated oncospheres incubated with non-immune mouse sera. However, C5, a protease necessary for the assembly of the membrane attack complex, was not detected. Early stage larvae cultured from in vitro-activated oncospheres escaped membrane damage and survived incubation in non-immune sera from both BALB/cByJ and taeniid-susceptible C3H/HeDub mice. Comparisons of cobra venom factor-treated and untreated C5-deficient B10.D2osn mice revealed no significant differences in parasite burden and local eosinophil infiltration at 6 days post-infection, suggesting that the terminal arm of the complement system is necessary for the previously reported role of complement in resistance to primary infection in BALB/cByJ and C3H/HeDub mice. An in vivo test of chemotaxis indicated that although both complement-intact mouse strains examined responded to intraperitoneal injections of inulin, there were lower numbers of eosinophils in C3H/HeDub mice than in BALB/cByJ mice, perhaps pointing to possible mouse strain differences in C5a generation/catabolism or eosinophil ability to respond to C5a. Lectin-binding studies showed an affinity of PNA for the exposed surface of taeniid oncospheres and 4-day post-infection metacestodes; however, binding of lectin to the carbohydrate moiety did not inhibit complement activation.     

Ovicidal effect of nematophagous fungi on Taenia taeniaeformis eggs

This work evaluated the ovicidal effect of the nematophagous fungi Monacrosporium sinense (SF53), Monacrosporium thaumasium (NF34) and Pochonia chlamydosporia (VC1) on Taenia taeniaeformis eggs in laboratory conditions. T. taeniaeformis eggs were plated on 2% water-agar with the grown isolates and control without fungus and examined at seven and fourteen days post-inoculation. At the end of the experiment, P. chlamydosporia showed ovicidal activity (P < 0.01) on T. taeniaeformis eggs unlike the other two species, mainly for internal egg colonization with percentage results of 32.2–54.0% at 7th and 14th day, respectively. The other fungi only showed lytic effect without morphological damage to eggshell. Results demonstrated that P. chlamydosporia was in vitro effective against Taenia taeniaeformis eggs unlike the other fungi. In this way, the use of P. chlamydosporia is suggested as a potential biological control agent for eggs of this cestode.     

Ultrastructural localization of alkaline phosphatase in the eggs of Hydatigera taeniaeformis (Taenia taeniaeformis)

Freshly shed gravid proglottids from a three-month-old infection of Hydatigera taeniaeformis collected from the faecal droppings of infected cats were used for this study. They were treated for transmission electron microscopy (TEM) followed by incubation using the lead precipitate method. Control sections were incubated in a substrate-free medium, a substrate medium containing 1.0 mM sodium fluoride (NaF) (an inhibitor), and the last sections were denatured at 90 degrees C for 1 min prior to incubation. Intensive alkaline phosphatase activity in the embryophoric blocks and the outer embryophoric membrane was revealed. The reaction products were also indicated in the oncospheral membrane. However, no enzyme activity was seen in any other part of the egg. The enzyme was also absent in the control sections. The presence of alkaline phosphatase activity in the outer embryophoric and oncospheral membranes suggested that this enzyme may be involved in carbohydrate metabolism and nutritional absorption, and also may play a role in the transport of nutrients and other substances from the adult to the developing embryo, respectively.     

Taenia taeniaeformis: colonic hyperplasia in heavily infected rats

Only one study previously mentioned the involvement of colon during Taenia taeniaeformis larvae infection in rats with inconsistent occurrence of lesions. Present study aimed to determine the consistency of histopathologic changes in colonic epithelia, and the proliferation of mucosal cells through BrdU and PCNA immunohistochemistry. Results demonstrated that crypt hyperplasia of the colon was found in all infected rats, although variable in degree even in a single tissue section. Cystic cavities were frequently seen in severely hyperplastic mucosa. Proliferative zone lengths were significantly increased and PCNA positive cells were observed throughout the colonic crypt lengths at 9 but not at 6 weeks post infection. Cell proliferation involving the major types of cells in the epithelial colon was also increased in infected rats at 9 weeks post infection, with labeling indices significantly greater than the control rats throughout the BrdU time course labeling. Findings suggested that massive increases in epithelial cells and depth of colonic crypts were due to a remarkable increase in cell proliferation. The study concluded that enteropathy in the colon during T. taeniaeformis infection could be consistently observed in heavily infected rats.     

Lectin binding sites in the human gallbladder and cystic duct

Summary A battery of 18 fluorescein isothiocyanate (FITC) labeled lectins was used to histochemically define the features of epithelial cells in the body, neck and the cystic duct of the human gallbladder. Surface epithelium in all three anatomic locations reacted with all lectins, either diffusely or focally, except for lectin type I from Griffonia simplicifolia and type II from Ulex europaeus. No quantitative differences were noted except for the tendency of some lectins to bind more often to the neck and cystic duct epithelium rather than the body and vice versa. In the body the surface epithelium did not differe from cells lining the crypts. On the other hand, glands of the neck and the cystic duct were essentially indistinguishable one from another but differed from the overlying surface epithelium in so far as they reacted with some lectins which were unreactive with surface epithelium and vice versa. Considerable case to case variation in the expression of lectin binding sites in each of three anatomic areas was noted. No consistent differences were noticed between gallbladders removed for cholecystitis — cholelithiasis and those removed for other incidental reasons. We conclude that all epithelial cells in the cholecysto-biliary tract are rich on glyconjugates but the pattern of expression varies depending on the anatomical location and the influence of poorly understood individual determinants.     

Taenia taeniaeformis: inactivation of metacestodes by gossypol in vitro

Gossypol, a natural biphenyl compound inhibits Taenia taeniaeformis metacestode development in vivo. In this paper, the direct effect of gossypol on metacestodes was examined. Within 24 hr of incubation at 37 degrees C in greater than or equal to 10(-5) M gossypol, shedding of the tegument from the surface of the metacestodes was observed. There was a significant decrease in [3H]thymidine uptake by T. taeniaeformis in greater than or equal to 10(-5)M gossypol. In addition, NADH lactate dehydrogenase activity of metacestodes was significantly inhibited in greater than or equal to 10(-5) M gossypol. Thus, gossypol has a direct inhibitory effect on T. taeniaeformis metacestodes in vitro.     

Lectin binding sites in the human gallbladder and cystic duct

A battery of 18 fluorescein isothiocyanate (FITC) labeled lectins was used to histochemically define the features of epithelial cells in the body, neck and the cystic duct of the human gallbladder. Surface epithelium in all three anatomic locations reacted with all lectins, either diffusely or focally, except for lectin type I from Griffonia simplicifolia and type II from Ulex europaeus. No quantitative differences were noted except for the tendency of some lectins to bind more often to the neck and cystic duct epithelium rather than the body and vice versa. In the body the surface epithelium did not differ from cells lining the crypts. On the other hand, glands of the neck and the cystic duct were essentially indistinguishable one from another but differed from the overlying surface epithelium in so far as they reacted with some lectins which were unreactive with surface epithelium and vice versa. Considerable case to case variation in the expression of lectin binding sites in each of three anatomic areas was noted. No consistent differences were noticed between gallbladders removed for cholecystitis--cholelithiasis and those removed for other incidental reasons. We conclude that all epithelial cells in the cholecysto-biliary tract are rich on glyconjugates but the pattern of expression varies depending on the anatomical location and the influence of poorly understood individual determinants.     

Stimulation of resistance to Taenia taeniaeformis in the rat by infection with Fasciola hepatica

Homologous resistance to F. hepatica and T. taeniaeformis and cross resistance between these two parasites was investigated in the rat. Rats given a primary infection with F. hepatica were challenged with either F. hepatica or T. taeniaeformis. Conversely rats given a primary infection with T. taeniaeformis were challenged with either F. hepatica or T. taeniaeformis.Infection with F. hepatica generated significant resistance against challenge with F. hepatica given 9 weeks later. Similarly, infection with T. taeniaeformis protected against challenge with T. taeniaeformis given 6 weeks later. Infection with F. hepatica also generated significant resistance against challenge with T. taeniaeformis given 4, 8 or 9 weeks later. Primary infection with T. taeniaeformis did not protect against challenge with F. hepatica.     

Studies on humoral immunity against Taenia taeniaeformis infection in rats

Rats were infected with doses of 100, 1000, 5000 and 10 000 eggs of Taenia taeniaeformis. Haemagglutinating antibody to cysticerus antigen was detected at the 4th week of infection. The appearance and levels of antibody titre did not vary greatly with the infective dose. An IgM peak appeared at the 6th week, with IgG appearing slightly later and continuing to rise. Transfer of serum from the 1st week onwards from infections with 1000 eggs however could confer significant protection. Dilutions of hyperimmune serum (1 ml volumes) of up to 1/32 conferred significant protection on normal recipients. Hyperimmune serum transferred up to 4 days before challenge could confer 80% protection whereas serum transferred 4 days after challenge was totally non-protective. The significance of this finding is discussed in the light of current knowledge of metacestode immunity.     

Morphological changes in cysticerci of Taenia taeniaeformis after mebendazole treatment.

The progressive micromorphological changes in Taenia taeniaeformis cysticerci, induced by a single parenteral treatment of the infected mice with mebendazole, are described. The time-related alterations concerned the tegument and tegumental cells and were successively: disappearance of microtubules, accumulation of secretory substances in the Golgi areas, decrease in number to complete loss of microtriches, "ballooning" of all tegumental cells with subsequent burst, vacuolization and degeneration of the tegument, and finally necrosis of the pseudoproglottids. Similar but less pronounced injuries were seen in the scolices, although microtubules disappeared as early as in the pseudoproglottids. Microtubules from the host tissues remained intact. The meaning of the apparent primary interference of mebendazole with the microtubular system in relation to the subsequently observed death of the cysticercoids is discussed.     

Taenia taeniaeformis: inhibition of metacestode development in the rat by gossypol

The effect of gossypol, a polyphenolic compound, on developing Taenia taeniaeformis larvae in the rat liver was examined. Five groups of rats were used. In group 1, subcutaneous injection of gossypol at 10 mg/kg was started 5 days prior to administration of tapeworm eggs. In group 2, gossypol injections were started 5 days after administration of eggs. Groups 3 and 4 were infected and noninfected rats, respectively, which received the vehicle (10% ethyl alcohol in 0.85% NaCl) only. Group 5 rats were noninfected but received gossypol. From each group, 5 rats were killed on days 7, 12, and 22 of infection, respectively. The number and size of larvae and the size of the livers were much less in rats gossypol injected 5 days before infection than those in the vehicle-treated group. Administration of gossypol 5 days after infection resulted in less inhibition. The size and the thickness of the fibrous capsule around larvae of the gossypol-treated rats were much smaller than those of the control-infected group. The actively developing larvae excrete or secrete a sulfated glycosaminoglycan which is specifically stained with alcian blue. There was much more alcian blue-positive substance around the larvae and the capsule of the control-infected liver compared to the gossypol-treated infected animal. The percentage body weight of the spleen was significantly greater in the gossypol-treated rats in both infected and noninfected groups. These results suggest that gossypol may directly inhibit tapeworm larval development or that elimination of the tapeworm may be resulted from gossypol-induced stimulation of host cell-mediated immunity.     

Evidence for selective incorporation of host immunoglobulin by strobilocerci of Taenia taeniaeformis

Strobilocerci of Taenia taeniaeformis were obtained from laboratory rats 90 days after experimental infection. Cyst fluid, whole parasite homogenate, and rat serum each were fractionated by SDS-PAGE, immobilized on nitrocellulose by western blot, and probed with conjugated goat anti-rat IgG. Reactive bands with relative mobilities corresponding to rat IgG were found in all 3 samples. Additional bands in cyst fluid and parasite homogenate may represent enzymatic degradation of IgG. The pattern of reactive bands in the homogenate discounts the nonspecific adsorption of host molecules onto the tegument and suggests selective incorporation of serum proteins. The presence of an IgG-like molecule of atypical molecular weight is consistent with either molecular mimicry or enzymatic cleavage of IgG bound to the tegument. The relevance of serum protein utilization by the parasite to evasion of the host immune response is discussed.     

Gastric hyperplasia and parietal cell loss in Taenia taeniaeformis inoculated immunodeficient mice

Immunodeficient mice were studied to determine their suitability as models in investigating the role of Taenia taeniaeformis larval products in the development of gastric hyperplasia. Recombinant active gene 2 (RAG2)-deficient and severe combined immune-deficient (SCID) mice were studied as candidate animal models. RAG2-deficient mice inoculated orally with T. taeniaeformis eggs developed gastric hyperplasia with alcian blue-periodic acid-Schiff-positive cell proliferation similar to those of rats. SCID mice inoculated with different doses and routes of T. taeniaeformis in vitro-hatched oncospheres and those orally inoculated with eggs resulted also in different degrees of gastric hyperplasia. Influence of inoculation forms of parasite, doses and routes of inoculation on initiation of hyperplastic gastropathy was suggested to be dependent on number and size of developed larvae. Both RAG2-deficient and SCID mice with hyperplastic mucosa were observed with significant loss of parietal cells. Apparent decrease in parietal cell number was observed in SCID mice at 2 weeks after intraperitoneal inoculation with oncospheres before hyperplastic lesions developed. Earliest occurrence of gastric hyperplasia in SCID mice was observed at 3 weeks after oral inoculation of in vitro-hatched oncospheres, sooner than orally inoculated rats. The results suggested that these immunodeficient mice could be used as animal models to study factors involved in T. taeniaeformis-induced gastric mucous cell hyperplasia.     

Morphological studies on the early development of Taenia taeniaeformis larvae in susceptible mice

Bortoletti G. and Ferretti G. 1985. Morphological studies on the early development of Taenia taeniaeformis larvae in susceptible mice. International Journal for Parasitology15: 365–375. Taenia taeniaeformis larvae which develop into infective strobilocerci in C3H mice have been studied from the 5th to the 15th day of development (L5–L15), both at light and electron microscope level. The L5 were initially compact, without a central cavity but then become vacuolized. Until stages L7–L8 they were surrounded by a perilarval amorphous layer (PAL) made up of a finely granular material which prevented the host cells from making contact with the larval tegument. The larval volume increased considerably between stages L6 and L8, remained unchanged from L9 to L13, but continued to increase thereafter. The larval cellular layer, which appeared as a single, large ‘syncitial system’, grow until stages L14–L15 when the scolex anlagen began to form. The tegument was initially incompletely organized and was covered by microvilli. These were completely replaced by microtriches from stage L8 onward. Sometimes both microvilli and microtriches were together observed in stage L7. Microvilli fragments, sometimes beaded, could be observed at L5 within the damaged cytoplasm of host cell debris. Very often they were branched at different heights, especially in stages L5–L7. In L10–L15 all undamaged microtriches increased in density and formed bundles which invaded the host cells. In stages L5–L8 and in some L9, muscular bundles started to become organized inside the tegumental distal cytoplasm (TDC), and after become independent in the subtegumental cellular layer (SCL). Until L8–L9 the larvae were surrounded by host cells debris. From stages L8–L10 onwards the adjacent host cells were less damaged though the larval microtriches penetrated them deeply. In stages L5–L7 neutrophils together with macrophages and some damaged hepatocytes were detected, while eosinophils were present only from L8 onward. In the other stages neutrophils clearly diminished in numbers, whereas macrophages had increased. No mastcells and few plasma cells were observed.