Showing papers in "Parasite Immunology in 1983"

Alternative pathway activation of complement by African trypanosomes lacking a glycoprotein coat.

Abstract: Summary An in vitro culture Trypanosoma congolense cell line was established using the mammalian cell feeder layer system. One of the principle characteristics of this parasite was its ability to multiply in culture at 35°C, as an uncoated trypanosome (lacking a glycoprotein surface coat) unlike the original blood stream form from which it was derived. This trypanosome was lysed when incubated in normal human serum in contrast to the parasite which possessed a surface coat. The lytic reaction was inhibited by EDTA but not EGTA and occurred in C2-deficient serum, demonstrating the involvement of the alternative pathway of complement activation. Similar results were obtained with procyclic forms of T. congolense and T. brucei brucei which also lacked surface coats. The results suggest that the glycoprotein surface coat protects the parasite by masking sites on the plasma membrane which are capable of promoting alternative pathway activation.

Nematospiroides dubius in the mouse: evidence that adult worms depress the expression of homologous immunity

Abstract: Mice immunized by a single infection with irradiated (25 krad) larvae of N. dubius were very resistant to subsequent challenge. However, when normal larvae were administered together with irradiated larvae at immunization, the acquired immunity expressed against a challenge infection was markedly depressed. It was found that as few as 50 normal N. dubius larvae interfered with the immunity that would have otherwise been elicited by the concurrently administered irradiated larvae, but this depressed response was totally alleviated when the normal worms were removed after completing their development in the intestinal mucosa and before they reached adulthood. Adult N. dubius were transplanted directly into the intestines of mice either 7 days before or after immunization by irradiated larvae; it was shown that the recipient mice were less resistant to challenge than mice which had been sham operated. Transplanted adult worms themselves stimulated very little resistance to challenge in recipient mice. These results established that adult parasites are capable of depressing the expression of homologous immunity in the mouse. The possible mechanisms by which N. dubius might modulate the host's immunological activity at the intestinal level are discussed and it is proposed that this mechanism is of benefit to the parasite in preventing the host from eliminating the worms during a chronic primary function.

Mimicry of snail host antigens by miracidia and primary sporocysts of Schistosoma mansoni

Abstract: Polyvalent antisera generated in rabbits to soluble haemolymph components from Schistosoma mansoni-susceptible (PR albino 'M line') and S. mansoni-resistant (10-R2) stocks of the snail Biomphalaria glabrata were employed as membrane probes to determine if antigens related to snail haemolymph were produced by the early larval stages of S. mansoni (PR-1 strain). Using immunofluorescence and immunoelectron microscopical methods we have demonstrated that antibodies to susceptible (anti-Suscept) and resistant (anti-Resist) snail haemolymph (Hg-depleted fraction) crossreact with miracidial epidermal and ciliary membranes as well as the surface membranes of intercellular ridges. Primary sporocysts, both transformed in vitro and maintained in culture for various time intervals in the absence of snail-derived factors, retain haemolymph-like antigens on their surface tegument although at reduced levels in comparison to miracidial stages. Furthermore prolonged cultivation of sporocysts (48 h) has little effect on the density of crossreacting tegumental antigens suggesting that as sporocysts mature these antigenic components are continually being expressed at the surface membrane. Since miracidia and sporocysts were derived in media devoid of snail host materials, shared antigens on larval surfaces are believed to be of parasite origin and constitute true molecular mimicry as defined by Damian (1979). The occurrence of crossreacting antibodies in both anti-Suscept and anti-Resist antisera further suggests that mimicked haemolymph-like antigens include at least some which are common to both snail stocks.

Antibodies to coccidia: detection by the enzyme-linked immunosorbent assay (ELISA)

Abstract: Summary The ELISA test was used for the detection of antibodies to coccidia in the serum and/or egg yolk of chickens infected with Eimeria acervulina, E. maxima or E. tenella and in the serum of rats infected with E. nieschulzi. Antigens prepared from different developmental stages of the parasite were tested and the cross-reaction between different species of Eimeria were examined. The variability in cross-reactivity of different species and the advantages and possible applications of the test are discussed.

Mechanisms of protective immunity against Schistosoma mansoni infection in mice vaccinated with irradiated cercariae III. Identification of a mouse strain, P/N, that fails to respond to vaccination.

Abstract: Eleven strains of inbred mice were examined for their ability to develop resistance to challenge Schistosoma mansoni infection as a result of previous exposure to homologous cercariae that had been attenuated by high-dose irradiation. Two strains, C57B1/6J and BALB/c, demonstrated consistently high levels of vaccine-induced immunity (means of 64% and 58% resistance, respectively, when compared to control groups of the same strain) and were designated as 'high responder' strains to vaccination. Six other strains fell into an intermediate category, demonstrating moderate, yet statistically significant, levels of immunity resulting from vaccination (means of 30-50% resistance). Only one of the strains examined consistently failed to respond to vaccination by the development of significant levels of immunity to challenge infection. Animals of the P/N strain demonstrated a mean of only 15% resistance to challenge in five experiments and have been classified as 'low responders' to vaccination. P/N mice have previously been characterized as deficient in their ability to mount delayed hypersensitivity reactions, produce lymphokine and display macrophage activation for cytolysis of extracellular and intracellular targets in other experimental systems, suggesting that these immune responses may be critical to the establishment of vaccine-induced resistance to S. mansoni infection. The availability of high and low responder mouse strains should facilitate a genetic approach to characterization of the immune effector mechanism(s) of vaccine-induced resistance to S. mansoni infection.

Immune depression in bovine trypanosomiasis. Effects of acute and chronic Trypanosoma congolense and chronic Trypanosoma vivax infections on antibody response to Brucella abortus vaccine

Abstract: Summary Cattle were vaccinated with Brucella abortus (S19) vaccine during acute (25 days) and chronic (25 weeks) Trypanosoma congolense and chronic Trypanosoma vivax (25 weeks) infections in order to determine the effect of such infections on the antibody response to the vaccine. It was found that the specific antibody responses of IgG1 and IgG2 sub-classes were profoundly depressed (80%) in both the acute and chronic infections with T. congolense. Whereas IgM antibody response was also profoundly depressed (90%) in cattle with the acute infection, it was only 50% depressed in those with chronic infection. There was no depression of IgG1, IgG2, or IgM in cattle infected with T. vivax. These animals, however, had no detectable parasitaemia at the time of vaccination and thereafter. These results suggest that during acute infection with T. congolense depressive mechanisms could be acting on the afferent arm of the immune response, namely, antigen recognition and/or processing.

Fasciola hepatica: development of monoclonal antibodies and their use to characterize a glycocalyx antigen in migrating flukes.

Abstract: Using mice harbouring early Fasciola hepatica infections, six monoclonal antibodies were prepared against a tegumental antigen present in T1 granules and glycocalyx of flukes. Blocking tests indicated that all monoclonals bound the same T1 epitope (or epitopes in close proximity on the antigen molecule), but this was not the determinant recognized by sheep and cattle. Localization of antibody binding at light and electron microscope levels showed that T1-type antigen also occurred in metacercarial tegument and in glycocalyx of gut cells and excretory ducts in juvenile and adult flukes. This indicates that the natural host-antibody response to F. hepatica may be to one antigen early in the infection. Protein A-gold labelling of monoclonal treated fluke sections revealed that the epitope was probably a polypeptide, unmodified by glycosylation in Golgi bodies. When isolated by immunoadsorption and separated electrophoretically under reducing conditions T1-type antigen was found to consist of a polypeptide mol. wt. 50 000, possibly linked to smaller entities mol. wt. 25-40 000. Tissue-specific variations in the antigen molecule might be conferred by linkage of different polypeptides or carbohydrate side-chains to an antigenic core polypeptide. A component of T1-type antigen was found to have mol. wt. of 25 000, possibly resembling a polypeptide of mol. wt. 24 000 from Schistosoma mansoni tegument.

The athymic nude rat. IV. Immunocytochemical study to detect T-cells, and immunological and histopathological reactions against Trichinella spiralis.

Abstract: Summary The anti-parasite response was investigated after oral infection of athymic nude (rnu/rnu) rats and heterozygous (+/rnu) littermates with 1000 muscle larvae of Trichinella spiralis. No IgM, IgG and IgE antibodies were detected in serum of rnu/rnu rats. Expulsion of adult worms from the small intestine was prolonged (worms were nearly all expelled at days 14 and 91 in +/rnu and rnu/rnu rats respectively). The yield of muscle larvae in the carcasses of nude rats at day 91 was 33 times higher than in +/rnu rats. In contrast to the strong inflammatory reaction in the parasitized tongue of +/rnu rats, no infiltration was observed in rnu/rnu rats. Using an immunoperoxide method with monoclonal anti-rat T-cell antibody, no T cells were identified in spleen, mesenteric lymph node and Peyer's patches. These data support earlier studies that the nude rat lacks functional T cells. As the counts of connective tissue mast cells (CTMC), intestinal mast cells (IMC) and globule leucocytes (GL) in small intestine of uninfected rnu/rnu rats were equal or higher than in +/rnu rats, it is concluded that the origin of these cells is thymus-independent. In contrast to +/rnu rats, infection of rnu/rnu rats induced no increase of CTMC, IMC or GL. Thus, these cells depend on T cells to undergo proliferation. Finally, results of this study were inconclusive whether IMC are precursors for GL, or that they represent independent cell populations.

Kinetics of expulsion of the nematode, Nippostrongylus brasiliensis, in mast-cell deficient W/WV mice.

Abstract: Summary Mucosal mast-cell hyperplasia is frequently observed in intestinal nematode infections and it has been suggested that mast-cell responses to parasite antigens are involved in worm expulsion (self cure). To evaluate the importance of this mechanism, the course of infection and expulsion of Nippostrongylus brasiliensis was compared in mast-cell deficient W/Wv and normal (+/+) mice. Initial infectivity rates were similar, but the subsequent kinetics of expulsion of adult worms differed principally in that the onset of expulsion in mast-cell deficient mice appeared to occur 24–36 h later than that in normal mice. Expulsion was complete by the 14th day post infection in both W/Wv and normal mice. Worm fertility (as estimated by faecal egg output) also differed in W/Wv and normal mice, with maximal egg output in W/Wv mice occurring 24 h later than that in normal mice. Although a few mast cells were present in the intestinal mucosa and tongue of W/Wv mice, their numbers did not change during the course of infection with N. brasiliensis. In contrast, worm expulsion in normal mice was associated with a moderate increase in numbers of intestinal mast cells, commencing at the onset of expulsion and peaking several days after expulsion was completed.

Immunoregulation of genetically controlled acquired responses to Leishmania donovani infection in mice: the effects of parasite dose, cyclophosphamide and sublethal irradiation.

Abstract: On a B10 (Lshs) genetic background, the development of acquired T cell mediated immunity to Leishmania donovani infection in mice is under H-2 linked genetic control. Following intravenous inoculation of 10(7) amastigotes three phenotypic patterns of recovery have been described: 'early cure' (H-2r,s), 'cure' (H-2b) and 'non-cure' (H-2d,q,f). In an attempt to determine the immunological basis for this H-2 linked genetic control the effects of varying parasite dose (5 x 10(3) to 5 x 10(7) amastigotes) and of pre-treatments with cyclophosphamide (50 or 200 mg/kg body weight CY) or sublethal irradiation (100 or 550 rad) on the course of infection, and on circulating anti-leishmanial IgG levels, were examined in strains representative of the three phenotypes: B10.D2/n (H-2d), C57BL/10ScSn (H-2b) and B10.RIII (H-2r). It was found that with low parasite doses (5 x 10(3) or 5 x 10(4)) 'non-cure' mice presented a 'cure' profile whilst raising the dose (5 x 10(7)) caused some perturbation of the normal self-curing response in 'cure' (but not 'early cure') mice. The highest dose did not, however, lead to progressive disease in the genetically non-cure strain. For the parasite dose experiments circulating anti-leishmanial IgG levels were higher in the early cure and cure strains than in the H-2d non-cure strain. The higher doses of CY and sublethal irradiation administered prior to infection had a clear prophylactic effect on the non-cure strain with some effect also observed in cure and early cure strains. This was thought to be due to deletion of the precursors of T suppressor (TS) cells suppressing cell-mediated immunity. Resolution of the liver parasite load in pre-treated mice took place despite minimal or undetectable levels of circulating anti-leishmanial IgG. Similarly, the earlier resolution of parasite load in pre-treated cure and early cure mice occurred even though the antibody response was severely reduced. This suggests that the high antibody responses observed in early cure and cure strains do not normally mediate cure and may simply reflect the independent effect of H-2 on T helper function or the humoral response.

Regulation of the growth and differentiation of Trypanosoma (Trypanozoon) brucei brucei in resistant (C57B1/6) and susceptible (C3H/He) mice

Abstract: Summary While Trypanosoma brucei brucei GUTat 3 were equally infective for C3H/Heand for C57B1/6 mice at doses ranging from 5 to 5 × 103 organisms and had similar prepatent periods in both strains of mice, infected C57B1/6 mice displayed lower parasitaemia, shorter times to parasite wave remission and survived for a longer time than infected C3H/He mice. Parasite growth and differentiation rates and host immune responses were similar for the first 5 days in both strains of mice after infection with 103 T.b.brucei GUTat 3 but, thereafter, parasite differentiation proceeded more rapidly and specific antibodies reached higher titres in C57B1/6 than in C3H/He mice. In contrast, parasite growth and differentiation rates were similar in irradiated mice of both strains. Furthermore, following inoculation of intact mice with irradiated T.b.brucei GUTat 3, C3H/Hemice actually mounted higher titred antibody responses than C57B1/6 mice showing that they were not intrinsically defective in their capacity to respond to GUTat 3 antigens. Parasite differentiation occurred at the same rate in irradiated (650r) C57B1/6 mice and in irradiated C57B1/6 mice reconstituted with syngeneic spleen cells although T.b.brucei GUTat 3 specific antibody was detected in the latter mice prior to peak parasitaemia. Furthermore, it was shown directly in C57B1/6 mice that there was no selective destruction of slender form T.b.brucei GUTat 3 parasites during the phase of accumulation of stumpy form parasites. These studies indicate that the more rapid differentiation of T.b.brucei GUTat 3 parasites in infected C57B1/6 mice as compared to infected C3H/Hemice was unlikely to be directly related to the more efficient antibody response in the infected C57B1/6 mice. The observations suggest that there might be an association between host mechanisms which regulate differentiation of T.b.brucei parasites and those which regulate antibody responses.

Genetic association of murine susceptibility to Brugia malayi microfilaraemia

Abstract: The influence of host genetics on susceptibility of mice to Brugia malayi microfilariae and its possible mechanism were studied. There was a strain-association for duration and peak level of microfilaraemia: CBA/CaJ, C3H/HeJ, DBA/1J, AuSs/J and A.S.w/Sn had a short duration (3-5 days) and low parasitemia (19-26 parasites/100 microliters blood) compared to C57Br/cdJ, AKR/J, C57BL/6J, 129/J, BALB/cJ, DBA/2J, B10.D2/NSn, B10.D2/OSn and SJL/J (duration of 58-73 days, peak parasitaemia of 58-74 parasites/100 microliters blood). Relative resistance to microfilariae was not related to the H-2 complex as determined in studies of congenic C3H.B10 (H-2b) and B10.H-2k mice and their background strains. This trait was inherited in a dominant fashion and involved a single or small number of genes. Serum anti-microfilarial antibodies reached highest levels in strains with a long duration compared to those with a short duration of parasitaemia (geometric mean titres of 1:13450 vs 1:284). The distribution of 51Cr-labelled microfilariae among the livers, spleens, lungs and kidneys of a resistant (CBA/CaJ) and a susceptible (C57BL/6J) strain was similar. Transfer of immune lymphoid cells or sera between histocompatible (H-2k) resistant CBA/CaJ mice and susceptible C57Br/cdJ animals did not alter the duration of microfilaraemia.

Mechanisms of Schistosoma mansoni egg excretion: parasitological observations in immunosuppressed mice reconstituted with immune serum.

Abstract: Summary CBA mice which had been deprived of their T cells by a combination of adult thymectomy and injection of rabbit anti-mouse thymocyte serum failed to excrete as many Schistosoma mansoni eggs in their faeces as immunologically intact controls. This failure of parasite egg excretion was not obviously attributable to any marked change in the amount of faecal matter produced, or to a change in the size of the worm burden, or to the number or distribution of eggs in the tissues as a result of T-cell deprivation. S. mansoni eggs freshly isolated from T-cell-deprived mice and injected intravenously into normal animals, induced lung granulomas which were the same size as those induced by injection of eggs from normal donors. The rate of S. mansoni egg excretion was not affected by the density of eggs in the tissues, in as much as there was a linear relationship between the number of tissue-bound eggs and the number of eggs detected in the faeces. Treatment of infected mice with the immunosuppressant hydrocortisone acetate also induced a marked reduction in the rate of egg excretion. Injections of serum derived from chronically infected normal mouse donors increased the rate of egg excretion in both T-cell-deprived and steroid-treated mice, but the degree of reconstitution obtained by daily serum injections was only partial relative to normal egg excretion rates. Treatment of infected normal or deprived serum-treated mice with cobra venom factor to reduce serum complement C3 levels had no effect on the rate of S. mansoni egg excretion.

Antibody‐dependent ingestion of P. falciparum merozoites by human blood monocytes

Abstract: Summary The binding of malarial antibodies to peripheral blood monocytes and the ability of these armed monocytes to attach to and ingest P. falciparum merozoites and schizont infected erythrocytes was evaluated by an in vitro assay. Monocytes from normal unsensitized subjects were preincubated with sera from individuals with various states of immunity to malaria and sera from normal controls. A marked difference in the level of merozoite phagocytosis was observed depending on immune status of the individuals whose sera were tested, but not on the antibody levels measured by fluorescence or precipitation tests. By protein-A-sepharose fractionation of these sera it appeared that the merozoite phagocytosis was mediated by immunoglobulin of the IgG class. Immunoglobulins eluted from these preincubated monocytes were able to bind to the parasites as detected by indirect fluorescent test. Similar assays performed with different strains and antibodies from various geographical areas indicated that the merozoite recognition and ingestion was not strain specific. The monocyte-immunoglobulin co-operation was effective in the phagocytosis of merozoites but not of schizont infected erythrocytes or normal erythrocytes. However, some degree of adhesion to the schizonts was recorded. These data seem to indicate that human blood monocytes can be specifically armed in vitro by cytophilic IgG with antimalarial specificity, and that such an effect is able to enhance markedly the clearance of free parasites but not of intact schizonts.

Murine malaria: dissociation of natural killer (nk) cell activity and resistance to plasmodium chabaudi.

Abstract: Summary Striking differences in the resistance to P. chabaudi infection among different inbred mouse strains have previously been correlated with the level of both the spontaneous and the infection-induced enhanced level of NK cell activity. We have examined this putative correlation in individual animals of backcross progeny derived from A/J (malaria-susceptible, low NK cell activity) and BIO-A (malaria-resistant, high NK cell activity) progenitors. We have found that NK cell activity and resistance to malaria segregated independently. Furthermore, C57BL/6-bg/bg mice which are deficient in NK cell activity were found to be as resistant to malaria as their heterozygous C57BL/6-bg/+ siblings. We conclude that low NK cell activity, characteristic of A/J strain mice, is not a sufficient determinant of the exquisite susceptibility of these animals to infection with Plasmodium chabaudi.

Action of leishmanial excreted factor (EF) on human lymphocyte blast transformation

Abstract: The effect of Leishmania tropica major excreted factor (EF) on human immune and normal mononuclear peripheral blood cells has been studied. The response of lymphocytes to stimulation either specifically with leishmanial antigens or non-specifically with phytohemagglutinin (PHA) in the presence of EF was tested by the uptake of 3 [H]thymidine. The results showed that EF inhibits the response of cells from immune donors to leishmanial antigens and from normal donors to PHA or PPD. Adherent and non-adherent cells were separated and the effect of EF on both populations was analysed. The results showed that EF inhibited blast transformation if both EF and antigen were presented to each of the separate populations. The inhibition of the adherent cells (mainly monocytes) was more marked than the inhibition of the non-adherent population (mainly lymphocytes).

Sj23, the target antigen in Schistosoma japonicum adult worms of an immunodiagnostic hybridoma antibody.

Abstract: Summary An IgG2a mouse hybridoma-derived antibody (designated I.134) has been identified which binds to Schistosoma japonicum adult worms and which has immunodiagnostic potential (for detection of antibody) in schistosomiasis japonica in the Philippines. The target epitope of this hybridoma antibody is contained in a 23 000 molecular weight protein of adult worms as analysed by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis of immunoprecipitates and a gel overlay technique. This adult worm antigen has been labelled biosynthetically using35 S-methionine as well as exogenously using lactoperoxidase-catalysed radioiodination and the Bolton and Hunter reagent with intact worms. As anticipated, the low molecular weight protein antigen (designated Sj23) appears to be one of several major immunogenic proteins of worms which induce antibodies in infected Philippine patients.

Studies on the development of anti‐schistosomular surface antibodies by mice exposed to irradiated cercariae, adults and/or eggs of 5. mansoni

Abstract: Levels of antibody a binding to the schistosomulum surface and b mediating in vitro eosinophil-dependent cytotoxicity of schistosomula were studied and compared to the in vivo levels of resistance to cercarial challenge in mice infected with irradiated cercariae, unirradiated cercariae of single or mixed sex, or injected with eggs. Antibody-binding was assessed by counting the number of IgG-Fc-receptor bearing cells (P388D1 cells) adhering to mechanically-transformed schistosomula. Significant levels of adherence occurred with sera taken from 1--2 weeks following exposure to irradiated cercariae, the level increasing gradually thereafter and being enhanced by repeated exposure. Sera from the bisexual infection showed a dramatic increase in binding activity between weeks 5--8, and with the single sex infections there was a steady rise up to week 10 followed by a sharp rise between weeks 10--12. Weekly injections of eggs produced a steady rise in serum binding activity. Sera taken just before challenge were also tested for their ability to mediate killing of schistosomula by eosinophil-enriched preparations of heterologous rat peritoneal exudate cells in vitro. Significant levels of killing occurred with all sera, but the greatest lethal activity was found in sera from the egg-injected, chronically-infected and 200 male cercariae-infected groups. This ranking did not correlate with in vivo resistance against challenge as assessed by worm recovery, the egg-injected and single sex-infected groups failing to manifest significant resistance.

Specific antibody responses to the variable surface glycoproteins of Trypanosoma congolense in infected cattle

Abstract: Summary Sera from cattle infected with three Trypanosoma congolense clones (ILNat 2.1, ILNat 3.1 and ILRAD 588) derived from different stocks were analysed for the presence of specific antibodies against the surface glycoproteins (VSGs) of the infecting trypanosomes using the solid and liquid-phase radioimmunoassays and the neutralization of infectivity test. High levels of IgM, IgGi and IgG2 antibodies against the VSGs of the infecting variable antigen types (VATs) as well as other VATs that arose during the course of infection were detected. In addition, 11 out of 12 infected animals showed recurrent peaks of antibody activity against the infecting trypanosomes. The recurrent peaks of antibody activity against the VSGs of the infecting organisms would suggest either a reappearance of trypanosomes of the infecting types or emergence of organisms that bear similar surface determinants. In contrast to the studies on murine trypanosomiasis, there was little or no antibody activity against 2, 4, 6-trinitrophenylated bovine serum albumin (TNP-BSA) in sera from these cattle.

Site of expression of immunity to Naegleria fowleri in immunized mice.

Abstract: An experiment was performed which confirmed a previous finding that mice are protected against Naegleria fowleri infection by immunization with amoeba-free supernatant from amoeba cultures. Histological observations suggested that this protection is expressed mainly at the nasal mucosa and possibly results from the combined effects of polymorphonuclear leucocyte-mediated killing of the amoeba and mechanical elimination of the organisms by extensive shedding of necrotic epithelium.

IgE production in rat fascioliasis

Abstract: SummaryF hepatica infection of rats caused a prolonged elevation of serum total IgE reflecting the continued presence of live worms in the host Infection with 40 metacercariae stimulated higher total IgE levels than infection with 20 metacer-cariae The parasite specific IgE response was biphasic, the first peak coinciding with the migratory phase in the liver parenchyma and the second with the establishment of flukes in the bile ducts

Selection, by major histocompatibility type (BoLA), of lymphoid cells derived from a bovine chimaera and transformed by Theileria parasites.

Abstract: Summary A means of selecting cells on the basis of histocompatibility type within bovine lymphoblastoid cell lines (LCL's) infected with protozoan parasites of the genus Theileria is described. Using this technique it has been possible to demonstrate that T. parva may have a more restricted target cell population in the particular in vitro systems studied than T. annulata.

Protection against experimental echinococcosis by non‐specifically stimulated peritoneal cells

Abstract: Summary Infection of cotton rats with Echinococcus multilocularis or vaccination with BCG, or its cell walls, activates peritoneal cells to kill the protoscolices of the parasite in vitro and protects laboratory animals against the cestode. To determine whether other ‘non-specific’ stimuli would also protect against the parasite, cotton rat peritoneal cells were activated in vivo with PHA and transferred to recipients 3 days later. The recipients, controls and PHA-treated animals were then inoculated with the parasite; 3 days after inoculation other untreated infected animals received cells activated in vivo with PHA. PHA-activated cells, the PHA treatment itself and immunization with a homogenate of the parasite stimulated a leucocytosis and protected against infection by E. multilocularis; carrageenan abrogated protection in PHA-treated animals. The results of this study confirm that protection against echinococcosis can be induced non-specifically; these results suggest that immunity in hydatid disease may have an important component in the inflammatory reaction.

Immune mechanisms in C57B1 mice genetically resistant to Trypanosoma congolense infection. I. Effects of immune modulation

Abstract: The effect of immune modulation on the pattern and course of infection with T. congolense was investigated in a strain of mice (C57Bl) which is known to possess a significant degree of trypanotolerance, and a susceptible strain (CFLP) which rapidly succumbs to infection. Immunosuppression of C57Bl mice by splenectomy, cyclophosphamide treatment or gamma irradiation reduced their survival to near that of susceptible strains of mice. In contrast, attempts to enhance the immune response of susceptible CFLP mice using either a variety of immunostimulants, simultaneous vaccination with irradiated parasites at the time of infection, passive immunization or reducing the number of parasites used for infection, failed to confer a level of protection comparable to that of C57Bl mice. It was concluded that the basis of trypanotolerance, although immunological in nature, is associated with, as yet, undetermined factors.

Activation of complement in C-reactive protein positive sera by phosphorylcholine-bearing component isolated from parasite extract.

Abstract: Summary Phosphorylcholine-bearing component levels in extracts of various parasites were determined by a capillary precipitin test using anti-phosphorylcho-line Ig A myeloma protein, TEPC-15. Phosphorylcholine was demonstrated as a structural component not only in nematodes but also in trematodes and cestodes. The phosphorylcholine-bearing component was isolated from an extract of Toxocara canis larvae using a TEPC-15-Sepharose 4B column. The component reacted with C-reactive protein in sera to form one precipitin line in Immunoelectrophoresis. The component provided two Brilliant Coomassie Blue positive bands in SDS-polyacrylamide gel electrophoresis. It reacted with C-reactive protein to activate complement in serum.

Characterization of macrophage function in Mycobacterium lepraemurium-infected mice: sensitivity of mice to endotoxin and release of mediators and lysosomal enzymes after endotoxin treatment.

Abstract: Mycobacterium lepraemurium (MLM) infection increases the sensitivity of mice to lipopolysaccharide (LPS) as do infections with other intracellular parasites. Tumour necrosis factor (TNF), lymphocyte activating factor (LAF) and increased levels of various lysosomal and cytoplasmic enzymes were found in serum samples taken 2 h after intravenous injection of a small dose of LPS suggesting that damage to a variety of cell types, including macrophages, had occurred. Sera from moribund MLM-infected mice not injected with LPS also demonstrated significant levels of TNF compared with controls. Intravenous injections of silica into leprous mice also led to increased levels of serum lysosomal and cytoplasmic enzymes but did not give rise to a significant amount of TNF or LAF. Moreover, in contrast to LPS treatment, the injection of silica did not lead to the death of leprous mice. These findings suggest that the phagocytic cells of the infected animals did not contribute to the production of these mediators after LPS challenge. Rather, the non-phagocytic granuloma macrophages or other unidentified cell types seemed to provide the main source of the monokines TNF and LAF in vivo in the present model. These mediators may have important implications for the immunopathology of MLM infection.

The primary humoral immune response of European green lizards (Lacerta viridis) to Leishmania agamae

Abstract: European green lizards, Lacerta viridis, produced relatively thermostable, dithiothreitol-sensitive, non-precipitating, agglutinins and complement-fixing antibodies (CFA) to Leishmania agamae administered subcutaneously (SC), intraperitoneally (IP) or orally (OR). Antibodies were also detected by the immobilization test (IMM) and by enzyme-linked immunosorbent assay (ELISA). The most sensitive method for the detection of stimulated immunoglobulins was ELISA. Antibodies were detected as early as 3 days post-infection with ELISA and between 5 and 7 for CFA, direct agglutination (DA) and indirect haemagglutination (IHA). In the case of IMM, the times of first detection varied from 14 to 28 days. Maximum CFA (2(-8)), DA (2(-8)), IHA (2(-11)) and ELISA (2(-16)) titres were reached from 42 to 49 days with significantly higher values occurring in the OR and IP groups. With IMM, maxima occurred after 5 or 6 weeks. Following exposure, two- to five-fold significant increases in serum lysozyme levels were demonstrated but the concentrations in sera following SC, IP or OR routes of antigen administration were not significantly different when the groups were compared with each other. The highest lysozyme values (approximately 12.3 - 12.5 micrograms ml(-1)) were found in the SC and OR groups when compared to the IP (7.40 micrograms ml(-1)).

Interference with anti-trypanosome immune responses in rabbits infected with cyclically-transmitted Trypanosoma congolense.

Abstract: Summary Rabbits were infected with two clones of antigenically distinct stocks of Trypanosoma congolense transmitted through Glossina morsitans. Local skin reaction development and the appearance of neutralizing antibodies were followed in animals infected with one or other of the trypanosome stocks, with both stocks simultaneously or with both stocks consecutively. There was little difference in local skin reaction development on rabbits infected with a single stock or with both stocks simultaneously but, in rabbits exposed to a heterologous stock 14 or 21 days after a primary infection reactions were reduced in size or completely absent. Neutralizing antibodies against metacyclic-derived trypano-somes were detected 21 days after infection in animals infected with a single trypanosome stock and, in rabbits infected with both stocks simultaneously, antibodies against each stock were also detected 21 to 28 days after infection. In rabbits challenged 14 or 21 days after primary infection the appearance of trypanocidal antibodies against the stock used for challenge was delayed from 28 to 49 days.

Suppression of primary and secondary antibody responses and inhibition of antigen priming during Babesia microti infections in mice.

Abstract: The antibody response to sheep red blood cells (SRBC) has been measured in C57Bl mice infected with the intra-erythrocytic piroplasm Babesia microti. The primary antibody response is severely reduced or abolished when antigen is administered at the time of maximum parasitaemia. The secondary antibody response of infected mice, which had been primed with SRBC, is reduced but retains the characteristics of a secondary response. Mice injected with SRBC at maximum parasitaemia failed to become primed to that antigen: these mice gave a primary antibody response to a second injection of SRBC given after the infection had become sub-patent. B. microti, therefore, can completely prevent the induction of memory, but only partially inhibit the expression of memory.