Host-parasite relationships of Fasciola hepatica in the white mouse. VIII. Successful vaccination with culture incubate antigens and antigens from sonic disruption of immature worms

Mice were successfully vaccinated using culture incubate and sonicate antigens from 16-day-old flukes. Various injection schedules using the culture incubate antigen decreased challenge worm counts by 54 to 86%. The best results were achieved when the culture incubate was injected at 12 and 24 hr of incubation. Host mortality in the natural immunity controls ranged from 33 to 42%, and in the vaccinated animals from 12.5 to 25%. Functional antigens were present by 12 hr of incubation. A single immunizing injection with the sonicate antigen decreased challenge worm counts by 86%. Two immunizing injections with this antigen decreased challenge worm counts by 82%. However, the pathologic process in the liver was more severe than in animals that received a single injection.     

Host-parasite relationships of Fasciola hepatica in the white mouse. VII. effects of anti-worm incubate sera on transferred worms and successful vaccination with a crude incubate antigen.

Mouse antisera against the 16-day-old worm incubate and sera from 25-day infections in mice debilitated migrating flukes in recipient animals as measured by worm recovery and host mortality. Mouse antisomatic and 100-day infection sera produced no such effects. Host mortality was significantly lower after challenge in mice given one ip immunizing injection of the worm incubate; however, worm recovery was not significantly reduced. Injections at 2, 7, 12, and 24 hr with the worm incubate elaborated over a 24-hr period protected 75% of the mice from infection after challenge, and reduced the worm burden by 83.3%.     

Immunity to Fasciola hepatica in the rat. Successful transfer of immunity by lymphoid cells and by serum

Experiments were carried out which demonstrated an acquired immunity to Fasciola hepatica in the rat. It was shown that this immunity could be transferred to recipients using either lymphoid cells or serum from infected donor rats. The extent of the protection obtained by cells appeared to be related to the quantity and persistence of the antigenic stimulus in the donor. Likewise, the degree of immunity conferred by immune serum was dependent upon the volume transferred. The significance of these results in relation to the mechanism of immunity to fascioliasis is discussed.     

Fasciola hepatica in rats: transfer of immunity by serum and cells from infected to F. hepatica naive animals

Immune, hyperimmune, and nonimmune serum samples were collected from inbred rats following 10 to 15 weeks of one [5 metacercariae (mc)/rat], two (5 mc followed by 30 mc/rat) or no (uninfected) exposure to Fasciola hepatica. Lymphoid cells also were collected from these donors. Inbred, naive rats in groups receiving immune serum, hyperimmune serum, nonimmune serum (serum control), immune cells, hyperimmune cells, and nonimmune cells (cell control) received intraperitoneally either a total of 20 ml of serum or a total of 3 x 10(8) viable lymphoid cells. A challenge infection of 30 mc/rat was administered orally at about the time of serum or cell transfer. The transfer of immunity was evaluated by examining recipient rats for parasites 4 and 8 weeks after challenge. Some hematological parameters and the precipitating antibody response of the recipients were monitored also. Hyperimmune serum, unlike immune serum, consistently provided a significant degree of protection in recipient rats. The precipitating antibody titre of this serum was higher than that obtained from the immune donor group. The importance of a second sensitization to obtain sufficiently potent serum was demonstrated. Lymphoid cells from infected donors did not consistently confer protection on recipients. Thus, the expression of protective immunity against F. hepatica seemed to be more dependent on the presence of antibodies than on cells. The hematological parameters of the recipients, in general, supported this observation. The precipitating-antibody response of protected rats was lower than that of unprotected animals following challenge, presumably because the development of fewer worms in the former provided less antigenic stimulation.     

Fasciola hepatica: development of tegument during migration in mouse.

T-0 granules of the type 0 tegumental cells of newly excysted juveniles appear in the syncytium of juveniles recovered from the abdominal cavity of mice 12 hr postinfection (p.i.). They undergo exocytosis and/or add their contents to the glycocalyx of the syncytial apical plasma membrane. While in the abdominal cavity the syncytial ground cytoplasm has an increased electron density. After arrival in the liver the type 0 cells metamorphose into type 1 cells of the adult and begin to synthesize T-1 granules. The type 2 cells of the adult arise by differentiation of embryonic cells in the parenchyma, 2–3 days p.i., and subsequently form protoplasmic tubular connections with the syncytium. On arrival in the bile ducts, 4 wk p.i., T-2 granules, formed in the type 2 cells, congregate in the apical cytoplasm of the thickened syncytium and the apical plasma membrane becomes much invaginated. The discussion correlates the development of the tegument with the changes in environment and a mechanism of spine growth is proposed.     

The demonstration of pre-hepatic immune response to Fasciola hepatica in the mouse.

Harness E., Hughes D. L. and Doy T. G. 1976. The demonstration of a pre-hepatic immune response to Fasciola hepatica in the mouse. International Journal for Parasitology6: 15–17. Two groups of mice were immunized with either one oral dose of 20 irradiated metacercariae per mouse or 2 such doses given 7 days apart. Twenty-one days after immunization these mice together with non immunized controls were orally dosed with 100 normal metacercariae. Two days later immature flukes were recovered from the peritoneal cavity and counted. The numbers of flukes recovered from both immunized groups of mice were significantly lower than those obtained from the controls; this is taken to indicate that a protective mechanism operates at the intestinal wall.     

Fasciola hepatica: influence of extrahepatic adult flukes on infections and immunity in rats

Surgical transfer of adult Fasciola hepatica from sheep, goats, and cattle to subcutis of rats 4 wk before infection with metacercariae resulted in a 50% decrease in infection rate as compared to nonoperated controls.Infection was established in 25 out of 77 rats with F. hepatica implants, while 54 out of 79 were infected in the control group. The protective effect of the fluke implantation is discussed. It is suggested that production of protective antibodies is stimulated by the undamaged living flukes, although the antigen itself has not been demonstrated.     

Scanning electron microscopy of Fasciola hepatica L. during growth and maturation in the mouse.

Throughout the entire life of the fluke the spines anterior to the ventral sucker are arranged in approximately 60 rings each of 60 to 70 spines. The spines on the posterior body are scattered without any pattern of rings and by 1 week post infection (p.i.) their numbers have doubled (from 3,000 on the newly excysted juvenile) to 6,000 and by 3 weeks p.i. their numbers have multiplied by 8 to 24,000. Just prior to entry into the bile ducts, between 2 and 3 weeks p.i., all spines, anterior and posterior, have metamorphosed from single pointed to multipointed forms by division at the spine tips. Spines on the anterior body of mature flukes recovered from the bile ducts of mice 26 weeks p.i. have between 10 and 15 points whereas those on the posterior body have up to 30 points. The tegument forms a rectangular pattern of plateaux and valleys around each spine on the posterior body of mature flukes but this pattern is not present on the anterior body.     

Studies on the induction of translocations in mouse spermatogonia. IV. Effects of acute gamma-irradiation

The rate of induction of reciprocal translocations by 56–816 R exposures of mouse spermatogonia to acute γ-irradiation (95 R/min) was determined by cytological examination of descendant spermatocytes. The dose-response relationship did not differ significantly from linearity and had a regression coefficient of 1.8·10⁻⁴ per R with respect to translocations per spermatocyte. Further analysis at exposures below 816 R (considered less likely to produce distortion) showed that the quadratic regression of best fit had too small a square-law component to account for the very low frequency of translocations obtained after chronic γ-exposures in a previous experiment. The possibility is discussed that there is some extra factor, besides the diminution of the square-law component, which operates to reduce the yield after protracted exposures.     

Disruption of spermatogenesis in Fasciola hepatica by some anthelmintics.

Eight-weeks old F. hepatica were recovered from rabbits and rats that had been treated with known fasciolicides and anthelmintics between 4 and 40 h previously. Examination of the surviving flukes showed that spermatogenesis was significantly disrupted by most of the fasciolicides but by none of the other anthelmintics. It is suggested that disruption of spermatogenesis is particularly associated with compounds showing activity against mature F. hepatica.     

Host-parasite relationships among group A streptococci. IV. Suppression of antibody response by streptococcal pyrogenic exotoxin

In rabbits, purified streptococcal pyrogenic exotoxin, at 0.002 of the ld(50) dose, suppressed the antibody response to injected sheep erythrocytes. The antibody suppressed was determined by density gradient ultracentrifugal analysis to be of the 19S class. Background serum antibody (50% hemolytic units), as determined photometrically, correlated well with background antibody-forming spleen cells, as determined by the hemolytic-plaque technique. The exotoxin induced neither positive nor negative changes in background antibody levels, but suppressed the early secondary response to injected antigen. A comparison and control experiment showed that purified gram-negative bacterial endotoxin at identical protocol did not induce antibody suppression, but did induce the well-known adjuvant effect. Because streptococcal pyrogenic exotoxin is known to inhibit the phagocytic function of the reticuloendothelial system (RES), these data strongly support the concept that antigen is processed by cells of the RES before it evokes a secondary immune response. The results also demonstrated that streptococcal pyrogenic exotoxin may play a unique role in lowering the acquired defense of the host against infection. If the anamnestic immune response of the host is temporarily suppressed, then the host-parasite balance would be upset in favor of the parasite.     

Studies of the immunological capacity of germ-free mouse radiation chimeras. IV. Cell-mediated immunity

The cell-mediated immune (CMI) response of germ-free mouse radiation chimeras was compared with that of conventional mice. Spleen or thymus cells from chimeric or normal mice were injected intravenously into lethally irradiated, allogeneic hosts. Spleens of the irradiated hosts were assayed for effector cells using the ⁵¹Cr release assay. Spleen cells from syngeneic and allogeneic chimeras and normal mice were equally active in giving rise to effector cells. However, thymus cells from allogeneic chimeras were completely inactive within 9 months post-bone marrow transplant while thymus cells from syngeneic chimeras and normal mice still remained functional. Although allogeneic chimeras contain cells potentially reactive toward host antigens, cells cytotoxic to host antigens were not detectable. In addition, these studies indicate the helper cell and effector cell, both associated with T-derived lymphocytes, represent two different populations.