Clinical evaluation of the efficacy of inoculating cattle with a vaccine containing Tritrichomonas foetus

To test the efficacy of a polyvalent Tritrichomonas foetus vaccine, 130 nulliparous heifers were randomly assigned to either receive the test T foetus vaccine or to serve as nonvaccinated controls. The polyvalent test vaccine consisted of a Campylobacter fetus/Leptospira canicola-grippotyphosa-hardjo-icterohaemorrhagiae-pamona bacterine containing 5 x 10(7) killed T foetus/dose. The polyvalent control vaccine consisted of the aforementioned formulation without T foetus. Heifers were administered 2 doses of control or experimental vaccine at 3-week intervals. Heifers were bred to T foetus-infected bulls and their conception and pregnancy rates were determined throughout gestation. In addition, serum samples were analyzed to determine induced concentrations of antitrichomonal antibodies and vaginal secretions were sampled to determine T foetus infection rates in control and vaccinated animals. One week after each of the 15-day breeding periods, 60% (6 of 10) of tested vaccinates and 80% (8 of 10) of tested control animals were T foetus culture-positive. The mean duration of infection of vaccinates was 3.8 weeks (+/- 7.5 days), compared with 5.4 weeks (+/- 7.5 days) of infection for control heifers. All vaccinates developed increased immunofluorescence and serum neutralizing antibody titers following the first immunization, and had additional increases of at least fourfold in response to the second injection. In contrast, no consistent increase in immunofluorescence or serum neutralizing antibodies was observed in control animals. Conception rates were 89.2% for vaccinates and 85.9% for control animals 30 days after breeding and 80 to 90% of these remained pregnant 60 days after breeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of T-cell derived cytokines in the downregulation of immune responses in parasitic and retroviral infection

Parasitic infection is frequently accompanied by a downregulation in host cell-mediated immunity. Recent studies suggest that this modulation of helper T cells and effector cell function can at least in part be attributed to the action of a set of inhibitory cytokines produced by T lymphocytes as well as by a number of other cell types. The best characterized of these inhibitory lymphokines are IL-4, IL-10 and TGF-beta. Interestingly, both IL-4 and IL-10 are produced by the Th2 but not the Th1 subset of CD4+ helper cells. The former subset dominates in many situations of chronic or exacerbated parasitic infection and is thought to suppress Th1 function as a consequence of the cross-regulatory activity of these two cytokines. The latter hypothesis is supported by recent experiments demonstrating that mAb-mediated neutralization of IL-10 reverses suppressed IFN-gamma responses and/or disease susceptibility in mice with parasitic infections. In vivo neutralization of TGF-beta has also been reported to increase host resistance to parasite challenge. In addition to suppressing T-cell differentiation, function or proliferation, IL-4, IL-10 and TGF-beta each inhibit the ability of IFN-gamma to activate macrophages for killing of both intracellular and extracellular parasites. Moreover, the three cytokines are able to synergize with each other in downregulating these parasiticidal effects. Interestingly, each of the cytokines inhibits the production of reactive nitrogen oxides, an effector mechanism previously demonstrated to play a major role in parasite killing by activated macrophages. In the case of IL-10, this suppression of nitrogen oxide production appears to result from an inhibition of TNF-alpha synthesis leading to defective macrophage stimulation. While distant from parasites in their biology and phylogeny, some retroviruses also appear to induce an over-production in downregulatory cytokines which is closely associated with the onset of immunodeficiency. Thus, in an animal model involving infection of mice with LP-BM5 MuLV and in human HIV infection, Th2 (IL-10 and/or IL-4) cytokine synthesis is increased while Th1 (IFN-gamma and/or IL-2) cytokine production is suppressed. These observations suggest that cytokine-mediated cross-regulation may play a role in the pathogenesis of acquired immune deficiency disease, contributing both to the progression of retroviral infection and the increase in susceptibility to opportunistic infections and malignancy. Observations of similar cytokine cross-regulatory activities in organisms as diverse as helminths, protozoa and retroviruses predict that comparable mechanisms may operate in a wide variety of infectious diseases.

[Parasitic diseases in patients with impaired immune response. Clinical picture and diagnosis]

Patients with impaired immune system are frequently infected with various parasitic diseases. The clinical picture is characterized by unusual manifestations and frequently severe recurrences of infections which are not normally serious. Some almost parasitic microorganisms produce symptoms exclusively in patients with impaired immune system. Parasitic infections have become increasingly common with the increasing number of patients who live for prolonged periods with impaired immune systems, often as a result of infection with HIV. Among the numerous parasitic infections which are observed in man, there are a few which occur particularly frequently in patients with impaired immune systems. This is a brief review of the clinical pictures and diagnostic options in parasitic disease in individuals with impaired immune system with particular emphasis on infections caused by: Pneumocystis carinii, Toxoplasma gondii, Cryptosporidium ssp., Microspora, Entamoeba histolytica, Leishmania ssp., and Strongyloides stercoralis. In patients with impaired immunity, parasitic infections frequently cause nonspecific symptoms and, on account of the impaired immunity, antibodies to the parasite are not always produced. The diagnosis of these infections is, therefore, based on morphological demonstration of the microorganism concerned, culture, specific antigen or DNA defections.

Neosporosis in the aborted fetus and newborn calf

Protozoal encephalitic lesions were found in four aborted fetuses and one dead newborn calf. The organism was identified as Neospora caninum by immunoperoxidase. The brain lesions were of two forms. One was observed in three fetuses of 5 months gestation and was characterized by multifocal necrosis. The other was found in a 7-month fetus and in a newborn calf, and showed severe infiltration with macrophages and plasma cells containing IgG. This association, between the age of fetus and inflammation, may reflect development of the immune system in bovine fetuses.

Protozoan infections and HIV-1 infection: a review

Reactivation of latent infection is the principal mechanism relating Toxoplasma gondii and Pneumocystis carinii to HIV. Less common is reactivation in Leishmania donovani, Trypanosoma cruzi, and microsporidian infections. An impaired primary immune response occurs in all these infections, and also with Cryptosporidium and Isospora belli. Association of HIV infection with gut parasites including Giardia lamblia and Entamoeba histolytica, and also with Trichomonas vaginalis infection is likely to be related to sexual modes of contact that favour both HIV and the parasite. The severity of malaria is not definitely associated with HIV, but Plasmodium falciparum infection may favour more rapid evolution of the HIV infection. Both malaria and trichomoniasis favour HIV transmission; the former by necessitating blood transfusion, and the latter by enhancing viral transmission during sexual contact.

Development of an enzyme-linked immunosorbent assay (ELISA) for the detection of antibody to the parasitic dinoflagellate Amyloodinium ocellatum in Oreochromis aureus

An enzyme-linked immunosorbent assay (ELISA) using antibody to affinity-purified Oreochromis aureus immunoglobulin and antigens from the parasitic dinoflagellate amyloodinium ocellatum was developed. The ELISA was then used to evaluate the immune response of the tilapine fish to immunization with the parasite. Fish immunized with antigens of the dinospore stage, either live or sonicated, produced a specific immune response that was detectable by this ELISA. Combinations of serial dilutions of A. ocellatum antigen and fish anti-A. ocellatum serum were examined to determine which dilutions provided optimal differentiation of seropositive from seronegative fish. Fresh and heat-inactivated serum from both seropositive and seronegative fish produced similar results.

[Antimicrobial activity of NK cells]

NK Lymphocytes were first identified by their cytotoxic and cytolytic activity against tumor cells. However there is now increasing evidence that these cells are also mediators of natural resistance against viruses, fungi, protozoa and bacteria. The purpose of this review is to summarize the data on the antimicrobial activity of NK cells and to discuss the influence of corticoids and of other molecules interfering with innate resistance against pathogenic micro-organisms.

Cyclosporin A: antiparasite drug, modulator of the host-parasite relationship and immunosuppressant

Cyclosporin A (CsA), a cyclic undecapeptide with powerful properties of immunosuppression, acts on parasitic infections in laboratory animals in various ways. The outcome of drug administration in vivo varies with timing of treatment relative to infection, route of administration, dose and number of treatments applied. CsA is clearly antiparasitic against malaria, schistosomes, adult tapeworms, metacestodes and filarial nematodes. By contrast, it acts as an immunomodulator against trypanosomes and Giardia, by exacerbating infection; in the case of Leishmania spp. the drug acts variously. In some other infections CsA acts both as an antiparasite drug and as an immunosuppressant (Toxoplasma, avian coccidiosis and gastrointestinal nematodes). This range of activities is reviewed and possible modes of action discussed in the light of emerging data on in vitro drug activity and on putative receptor binding. The potential value of a non-immunosuppressive analogue of CsA in the control of parasitic infections of humans and domestic animals is considered but this paper lays particular stress on the seminal role of CsA as a laboratory tool.

Enteric infection with an obligate intracellular parasite, Encephalitozoon cuniculi, in an experimental model

Rabbits were intrarectally infected with 3 doses (5 x 10(3), 5 x 10(5), and 5 x 10(7] of an obligate intracellular parasite, Encephalitozoon cuniculi, with or without prior colonic lavages. Although chronic administration of enemas seems to interfere to some degree with the intestinal translocation of the parasite, systemic infection was observed in both manipulated and nonmanipulated animals. The animals responded with antibodies of immunoglobulin A (IgA) and IgG isotypes, reflecting the route of infection. They also produced significant amounts of circulating immune complexes composed of IgA and IgG antibodies and E. cuniculi antigens. Lesions compatible with encephalitozoonosis were seen in the liver, kidney, lung, and brain. In all instances, nonmanipulated animals had more severe lesions than manipulated rabbits given the same dose of parasites. Levels of serum antibodies, circulating immune complexes, and histopathologic changes were associated with the infection dose. The presented data suggest that human microsporidiosis may also be transmitted via the rectal route. It is, therefore, of clinical relevance in view of several reports of microsporidian infections in patients with acquired immunodeficiency.

Clinical significance of small-intestinal microsporidiosis in HIV-1-infected individuals

To assess the importance of microsporidiosis of the small intestine in the pathogenesis of chronic diarrhoea in HIV-1-infected individuals, duodenal biopsy samples from the following three patient groups were prospectively evaluated for bacterial, viral, and parasitic pathogens by standard methods, and for microsporidia by light microscopy: 55 consecutive HIV-1-antibody-positive subjects with unexplained diarrhoea of at least 3 weeks duration (group A); 38 HIV-1-seropositive subjects without diarrhoea (group B) who consecutively underwent upper gastrointestinal endoscopy for various reasons; and 7 patients without known risk factors for HIV infection with chronic unexplained diarrhoea (group C). In groups A and B most subjects had had previous AIDS-defining opportunistic infections and the median peripheral blood CD4 lymphocyte count was less than 0.1 x 10(9)/l. Microsporidia were detected as the single pathogen in 15 of the group A compared with 1 (in whom diarrhoea subsequently developed) of the group B patients (p = 0.001) and none of the group C patients. With the exception of 4 of the group A patients, no other intestinal pathogens were identified in any of the patients. The median peripheral blood CD4 count was significantly lower in patients with detectable microsporidia than in those without microsporidiosis (0.03 x 10(9)/l vs 0.06 x 10(9)/l; p = 0.03); in all patients with microsporidiosis, the CD4 count was equal to or less than 0.1 x 10(9)/l. 13 patients with microsporidiosis were treated with metronidazole, in 10 of whom treatment led to a substantial improvement or disappearance of diarrhoea within days of starting therapy, but did not result in eradication of the parasite in the 5 patients who underwent repeat biopsy. The findings suggest that small-intestinal microsporidiosis is an important cause of chronic unexplained diarrhoea in HIV-1-infected individuals with pronounced cellular immune deficiency. This infection should therefore be added to the list of AIDS-defining opportunistic infections.

Immunity and genetics: their relation to control of parasitic zoonoses

Effective control of parasitic zoonoses will ultimately require a combination of several approaches, including hygiene/sanitation, pasture management, chemotherapy and immunoprophylaxis. Development of vaccines, and other approaches to improving protective immunity, require a detailed understanding of parasite immunogenicity and host immune responsiveness. It is increasingly recognized that there is considerable variation in both of these parameters, and that this variation is genetically determined. Recent studies in this area and the consequences for control are discussed.

Heat shock proteins in host-parasite interactions

For most living organisms, heat shock represents an unusual stress situation, but for parasites that are transmitted between invertebrate vectors and mammalian hosts it is a frequent physiological occurrence. Because of the extraordinary conservation of heat shock proteins (HSPs) and their potential immunogenicity, much attention has recently focused on the role of HSPs in infection and immunity. In parasites, HSPs appear to play specific functions in differentiation, in protection from the host cell's killing mechanisms, including oxygen free radicals, and even in virulence. In this article, Barbara Polla uses the example of malaria to illustrate the possible role of HSPs in host-parasite relationships.

The involvement of TNF, IL-1 and IL-6 in the immune response to protozoan parasites

One early reaction of the host to infection with protozoan parasites is the secretion of an array of potent cytokines including tumor necrosis factor (TNF), interleukin (IL-1) and IL-6. The combined action of these cytokines causes fever, leukocytosis and the production of acute phase proteins such as C-reactive protein (CRP). These early responses contribute significantly to the outcome of infection by influencing the course of infection directly and by regulating the specific immune response to the parasite.

The acute phase protein response during parasitic infection

There is a paucity of comprehensive studies of the APP response in parasitic infection. This should be remedied for two reasons. First, as there is a limited number of cytokines with hepatocyte-stimulating activities, and as each one elicits a unique spectrum of protein changes, examination of the APP response during infection could provide insight into the cytokines involved. Second, the presence of IL-1, IL-6 and TNF, the mediators of the APR, in tissues and circulation have important implications for subsequent immune responses.

Lymphocytes play the music but the macrophage calls the tune

Researchers interested in immunological aspects of bacterial, fungal, protozoan and helminthic infection are too often kept apart by artificial subject boundaries. These barriers were temporarily breached by a recent workshop* in which the complex interplay between microbes and their mammalian hosts were examined from a global viewpoint. The role of T-cell subsets and their products came under close scrutiny but the most forceful image was that of the macrophage. As host for infective agents, as modulator of specific immune activity and as ultimate mediator of the host response, the macrophage plays a virtuoso's role in the host-parasite drama.

Immunoglobulin E in the feces of children and adolescents from some tropical and subtropical countries

Eighteen of 27 individuals, aged from 6 months to 19 years (mean 5 years, 7 months), from countries in the tropics or the subtropics had either intestinal parasitic infestations or intestinal enteropathogenic bacterial infections or both. Fourteen of those with intestinal pathogens had detectable concentrations of IgE in their fecal extracts, ranging from less than 0.5 to 420 IU/ml extract (mean 33 IU/ml). This rate of occurrence was significantly higher than the number of IgE-positive fecal extracts in a group of 54 healthy nonallergic Norwegian children (p less than 0.001), but did not differ from that of a group of 40 allergic children (p greater than 0.20). The individuals with intestinal helminthic infection had the highest fecal IgE concentrations. Of the 9 individuals who did not have any demonstrable intestinal pathogen, low concentrations of IgE could be detected in feces from only 2, which did not differ from the rate in the healthy Norwegian controls. The concentrations of IgE in the feces of the subjects from tropical/subtropical regions correlated linearly with the corresponding serum concentrations of IgE (r = 0.69; p less than 0.001). The results indicate that the combined load of intestinal pathogens, including helminths, protozoa, and enteropathogenic bacteria, may stimulate IgE production in the gut.

Variable antigens of Ureaplasma urealyticum containing both serovar-specific and serovar-cross-reactive epitopes

Currently there are 14 recognized serovars of Ureaplasma urealyticum, and it has been postulated that only certain ones may be associated with disease and that lack of serovar-specific antibody may be an important risk factor. Unfortunately, ureaplasma antigens important in the human immune response and disease pathogenesis are poorly defined. By using sera from ureaplasma-infected patients and antiureaplasma monoclonal antibodies, the present study has demonstrated, for serovars 3, 8, and 10, antigens which (i) are species specific, (ii) contain both serovar-specific and cross-reactive epitope(s), (iii) are produced not only in vitro but also in vivo, (iv) undergo a high rate of structural variation in vitro, (v) are present and structurally variable on invasive ureaplasma isolates (i.e., those from placenta, lung, and cerebrospinal fluid), and (vi) are among the predominant antigens recognized during infections in humans. Furthermore, we have shown that monoclonal antibodies to these antigens can inhibit the growth of the organisms in vitro, indicating the potential for these antigens to be important for host defense.

Immunity to internal parasites

This review of internal parasitic diseases discusses methods of immune diagnosis, immune mechanisms of the host, and immunoprophylaxis against both protozoan and metazoan parasites of livestock. The limiting factors for immunodiagnosis are specificity and whether the host animals respond sufficiently to produce detectable serological responses. Because the array of antigens is so complex, the method of choice for helminths is to use excretory/secretory products of the parasite as antigens for microplate ELISA. Similarly, for protozoa, immunodiagnosis is facilitated by using a few, selected, immunodominant antigens rather than extracts of whole parasite. However, serodiagnosis does not always identify parasitised animals especially in the young, malnourished or sick host. Similarly, parasites may themselves modulate the response of the host and remain serologically undetectable. The production of recombinant, pure, parasite proteins is already facilitating diagnostic serology for several parasite species and, using recombinant DNA probes, it is now possible to distinguish inter- and intra-species differences. The central role of inflammatory cytokines, the regulatory proteins produced by activated T helper cells, in modulating both protective and potentially damaging inflammatory responses is discussed. Finally, the genetic control of the immune response and its relevance to immunoprophylaxis is considered. Several interesting developments in the production of sub-unit vaccines and the potential methods of delivery are appraised.

[The immunological reactions of fishes to parasite infection under different temperature conditions]

The dependence of immunological reactions of fishes infected with Ichthyophthirius multifiliis infusoria was elucidated. The invasion of the parasite results in the activation of the immune system, increased phagocytosis and a growth of the activity of oxydase enzymes. With the increased number and sizes of parasites a decrease of the above parameters below the control values is observed. Changes of the immunological values are most dynamic at high (20-25 degrees) and they are slower at low (10 degrees) temperatures.

Measurement of antibody in serum and genital fluids of bulls by ELISA after vaccination and challenge with Tritrichomonas foetus

An enzyme-linked immunosorbent assay (ELISA) was developed for detecting antibody to Tritrichomonas foetus using both whole cell antigen (WCA) and membrane protein antigen (MPA). The test was used to detect specific antibody in serum, preputial washings and seminal plasma samples from 7 adult bulls which were vaccinated subcutaneously on 3 occasions with a membrane protein vaccine against T. foetus var brisbane in an oil adjuvant, and from 4 unvaccinated control animals. One month after administration of the third dose of vaccine, vaccinated and control bulls were repeatedly challenged with the live vaccine strain of the T. foetus. A steady increase in serum antibody titre was detected after each inoculation of vaccine when both antigens were used in the ELISA. However, MPA was more sensitive. After challenge, vaccinated bulls developed an increased titre. No specific antibody was detected in control bulls, except in one bull after challenge in which seroconversion was detected. The serum antibody titres of both groups of animals were also measured with the microagglutination test which proved less sensitive than the ELISA. Antibody titres to both antigens, although lower than in serum, were detected in the seminal plasma of vaccinated animals. The control bulls remained non-responsive. No antibody was detected by ELISA in preputial washings from either control or vaccinated bulls prior to challenge. Post-challenge, some of the vaccinated bulls were responsive with both antigens whereas the control bulls remained negative.

Parasitic protozoa and helminths: biological and immunological challenges

Parasitic protozoans and helminths pose considerable medical as well as scientific challenges. Investigations of the complex and very different life cycles of these organisms, their adaptation to the obligate parasitic mode of life, and their ability to face the hostile host environment have resulted in many exciting discoveries. Invasion of host erythrocytes by plasmodial sporozoites and intact skin by schistosomal cercariae are outlined as examples of the elaborate mechanisms of parasitism. Isolation and characterization of single protective antigens or subunit vaccines from these two organisms are examined as models for vaccine development. Finally, developments in exploring gene regulation in protozoans and free and parasitic nematodes are briefly outlined.

The immune response in cattle infected with Tritrichomonas foetus

Holando-Argentina calves (males and females) were experimentally infected with Tritrichomonas foetus var. Belfast (T. foetus) by introducing 10(7) protozoa into the preputial and vaginal cavities, in order to analyse the course of the immune response to infection. Samples of serum, vaginal mucus and preputial secretion were taken periodically and assayed by means of microagglutination of living protozoa. The serum antibody titre, which averaged 32 before infection and was equivalent to titres in a non-infected group, increased to 512 in the heifers 11 weeks later and to 128 in the bulls 4 months post-infection. Agglutinating antibodies were not detected in the preputial cavity, but heifers showed antibodies in the vaginal mucus and became trichomoniasis free after 4 months. Conversely, genital secretions from the bulls gave rise to positive cultures during the whole period of experimentation. The intradermal sensitivity was checked using a soluble antigen from T. foetus. The diameter of the papula increased up to three times in heifers, while in bulls the results were no different than those from the non-infected group. Serum antibodies were of the IgG2 subclass, while those isolated from vaginal mucus were characterized as IgG1, an opsonizing antibody. Heifers were refractory to challenge infection after 1 year. The poor immune response in bulls is consistent with their role as carriers of T. foetus.

Neospora caninum (Protozoa: apicomplexa) infections in mice

Groups of mice were given 0 mg, 4 mg, or 2 mg of methylprednisolone acetate (MPA) 7 days prior to, the day of, and 7 days after subcutaneous inoculation with 0 or 2 x 10(5) tachyzoites of Neospora caninum. Clinical signs of disease were seen only in mice given both MPA and N. caninum tachyzoites. Mice given 4 mg MPA and N. caninum tachyzoites developed severe disseminated neosporosis and most died or were killed when comatose 11-13 days postinoculation (PI). Acute pneumonia, polymyositis, encephalitis, hepatitis, and pancreatitis were the main lesions in these mice. Mice given 2 mg MPA and N. caninum developed mild pneumonia and many mice began showing neurological signs 14 days PI. Neurological signs consisted mainly of pronounced head-tilting and associated impairment of movement. Grossly visible 1-2-mm single or multiple, white areas of discoloration were seen in the brains of many of these mice. Encephalitis, ganglioradiculoneuritis, pneumonia, and polymyositis were the main changes seen in these mice. Tissue cysts of N. caninum were only seen in mice given 2 mg MPA and were first seen 21 days PI. Tissue cysts were 16-34 by 13-29 microns and had a 1.5-3.0-microns-thick cyst wall. Tissue cysts were seen only in the brain. Mice given 4 mg MPA and tachyzoites and host cells that had been frozen for 1 wk did not develop clinical signs of infection, indicating that freezing kills tachyzoites and that viruses or other agents were not involved in the genesis of disease seen in mice given MPA and viable tachyzoites.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of resistance/susceptibility to murine encephalitozoonosis

Mechanisms of resistance/susceptibility to the obligate intracellular protozoan Encephalitozoon cuniculi were studied in resistant BALB/c and susceptible C57BL/6 mice. Three immunological functions were examined: the production of lymphokine(s) (LK) by T-lymphocytes, the proliferative response of spleen cells to parasite spore fragments, and the ability of splenic and thioglycollate-induced peritoneal macrophages to act as accessory cells in antigen-induced T-cell proliferation. The two strains showed differences in the time required for LK production in vitro but not in their ability to generate LK. Spore fragment-induced lymphoblastogenesis was found in spleen cells of infected BALB/c and C57BL/6 mice. There was no difference between the two strains in dose response and time of maximal response, but the magnitude of maximal response was significantly less in C57BL/6 mice. Indomethacin was found to augment the lymphoproliferative response of C57BL/6 but not BALB/c mice, suggesting that prostaglandin production may be involved in immunosuppression in C57BL/6 mice. C57BL/6 mice required more splenic adherent cells to achieve the same proliferative response as found in BALB/c mice. The ability of thioglycollate-induced peritoneal macrophages to act as accessory cells in antigen-induced T-cell proliferation was less in C57BL/6 mice than in BALB/c mice. Thus, it appeared that the relative susceptibility of C57BL/6 mice to encephalitozoonosis may be due to defective accessory cell function of splenic and peritoneal macrophages, depressed lymphoproliferation against spore fragments (possibly due to prostaglandin-mediated suppression) and a delay in LK production. There was no significant difference between the survival times of BALB/c-nu and C57BL/6-nu mice, suggesting that non-immune mediated resistance did not play a role in determining resistance/susceptibility.

Some aspects of Leucocytozoon caulleryi reinfection in chickens

The role of first- and second-generation schizonts in acquired immunity to Leucocytozoon caulleryi in chickens was studied. The chickens, which had recovered from a primary infection with various doses of sporozoites at 22-95 days of age, were challenged with sporozoites. First-generation merozoites were found in all of the challenged chickens, but no second-generation merozoites and gametocytes were seen in 30 of 32 chickens challenged with sporozoites. Almost all of the chickens that had recovered from a primary infection with sporozoites showed complete resistance to reinfection, and those that had recovered from a primary infection with first-generation merozoites showed resistance to reinfection with sporozoites. These results indicate that the second-generation schizont of L. caulleryi appears to be more immunogenic than the first-generation schizont and that some immune factors acquired by the chickens in the second generation of schizogony may inhibit the development of second-generation schizonts.

Studies on cross-immunity in Herpetosoma trypanosomes of Microtus, Clethrionomys and Apodemus

Laboratory-bred rodents of three species were inoculated with heterologous Herpetosoma trypanosome species as follows: Microtus agrestis with Trypanosoma evotomys or T. grosi, Apodemus sylvaticus with T. evotomys or T. microti and Clethrionomys glareolus with T. grosi or T. microti. The three rodent species were subsequently challenged with their natural trypanosome parasite, i.e. T. microti for M. agrestis, T. grosi for A. sylvaticus and T. evotomys for C. glareolus. The parasitaemias and courses of infection that developed were followed. All challenged animals showed some degree of cross-immunity; not all became infected, and those that did had lower levels of parasitaemia and shorter patent periods than control animals. No C. glareolus previously inoculated with T. microti developed T. evotomys infections on challenge, and an infection was observed in just one of ten M. agrestis inoculated first with T. evotomys and later with T. microti.

The influence of Encephalitozoon cuniculi on neural tissue responses to implanted biomaterials in the rabbit

Laboratory rabbits are commonly used for testing the tissue response of neural device biomaterials. Rabbits of many colonies in the U.S. are infected by the intracellular microsporidian parasite, Encephalitozoon cuniculi, with rates of infection ranging from 15 to 76% (1). Several authors have suggested that infection by this parasite may alter immune system response and experimental results. We report that infection by E. cuniculi made the interpretation of results more difficult and altered the animals' responsiveness to implanted platinum wires coated with various polymers such as glow discharge methane, Parylene C, or polyimide. Edema, neuronal and glial reaction, and inflammatory responses to the coated wires were quantitated at four sites in each animal. Inconsistency of response in all measured parameters was found, both between animals and between sites in infected animals. Infected animals showed the greatest variability, primarily in the degree of inflammatory reaction. Parylene C was found to induce the most severe inflammatory reaction, an unexpected finding. No consistent reaction to any of the coating materials was found in this study. We believe that this variability in response was primarily due to infection by E. cuniculi. Our results suggest that rabbits should not be used for tissue compatibility testing of neural device biomaterials until the animals are free of E. cuniculi infestation as demonstrated by serologic screening.

Encephalitozoon cuniculi infection in MRL/MPJ-LPR (lymphoproliferation) mice

Experiments were conducted to determine (a) whether mice bearing the single autosomal recessive gene lpr (lymphoproliferation) are more susceptible to encephalitozoonosis than syngeneic mice without the lpr gene and (b) whether infection with Encephalitozoon cuniculi in autoimmune MRL/MPJ mice accelerates and/or exacerbates the development of hypergammaglobulinemia, a manifestation of encephalitozoonosis in dogs and foxes. The results suggested that the lpr gene does not influence susceptibility to murine encephalitozoonosis. Infection with E. cuniculi changed neither the onset nor the severity of the spontaneous, age-related hypergammaglobulinemia in MRL/MPJ mice. Hypergammaglobulinemic lpr mice with encephalitozoonosis did not develop more severe lesions than lpr mice without encephalitozoonosis nor was their death accelerated.

Pneumocystis carinii infection of the small intestine in a patient with acquired immune deficiency syndrome

The authors describe a patient with acquired immune deficiency syndrome (AIDS) who presented with an acute abdomen. A plaque-like tumor of the small intestine was resected and found to consist of masses of Pneumocystis carinii organisms. The organisms also exhibited a perivascular and intravascular distribution. Identical changes were found in regional lymph nodes. In addition to silver stains and electron microscopy, an immunohistochemical method for the demonstration of P. carinii was employed. The technique may have advantages over silver staining, as it identifies trophozoites in addition to cysts. A review of the literature concerning extrapulmonary pneumocystosis indicates that affected patients nearly always have concurrent pulmonary infection. The pattern of organ involvement and the finding of perivascular and intravascular organisms are consistent with lymphatic or hematogenous dissemination from the pulmonary focus. Pulmonary pneumocystosis was not documented in the patient described herein, although there were radiographic densities in one pulmonary lobe.

Detection of anticytauxzoon antibodies in cats infected with a Cytauxzoon organism from bobcats

A microfluorometric immunoassay was developed for the detection of antibodies to a Cytauxzoon organism of bobcat origin. A homogenated antigen of RBC-parasite lysate was used to measure antibody levels in sera from cats experimentally infected with the non-pathogenic erythrocyte form of the bobcat Cytauxzoon organism. Antibody levels in sera collected at weekly intervals, expressed as FIAX values, were correlated with parasitemia levels and erythrocyte packed cell volume (PCV). The antibody levels tended to be highest and the PCV lowest at or near the peak parasitemias. Splenectomized cats developed higher antibody and parasitemia levels than non-splenectomized cats. Single serum samples collected from 31 cats were used to establish a baseline response level for normal domestic cat populations.

Immunologic and clinicopathologic evaluation of adult dogs inoculated with Encephalitozoon cuniculi

Beagle dogs inoculated intravenously with 1.75 x 10(9) viable Encephalitozoon cuniculi spores at 12.5 months of age were monitored for 18 months to assess infection in the adult dog. Parameters monitored included packed cell volume, total and differential leukocyte counts, and humoral and cellular responses to infection. Immunoglobulin M and G antibodies directed against the parasite tegument were present throughout the 18 months. Peripheral blood monocytes treated with lymphokines, either antigen specific (E. cuniculi) or nonspecific (concanavalin A), killed E. cuniculi spores in vitro. Pretreatment of E. cuniculi spores with normal dog serum or infected dog serum enhanced the killing of the parasite (normal dog serum less than infected dog serum) by canine monocytes. Histologic examination of selected tissues revealed microfocal plasma cell and lymphocyte aggregates at the renal corticomedullary junction and in the medullary interstitium. The results of these experiments suggest that the adult dog is able to mount an effective defense to infection, to minimize host tissue damage, and to eliminate the parasite through complex interactions between monocytes-macrophages and lymphocytes.

Relationships between Cytauxzoon felis and African piroplasmids

A cat which had recovered from Cytauxzoon felis infection following treatment with the anti-theilerial drug, parvaquone, showed an increase in piroplasm parasitemia after splenectomy and its blood was suitable for the preparation of antigen smears for the indirect fluorescent antibody test. High levels of antibodies were found in this cat after recovery, in two other cats sub-lethally infected with piroplasms and in sera of naturally infected bobcats. Cats recovered from piroplasm infection died from cytauxzoonosis when challenged with organ material containing C. felis schizonts. Tests with piroplasm antigens and positive sera of C. felis, South African Babesia felis and African Theileria taurotragi showed no significant serological relationship between C. felis and the African parasites. C. felis was not shown to be infective for splenectomized sheep.

An enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to Encephalitozoon cuniculi and its use in determination of infections in man

An enzyme-linked immunosorbent assay (ELISA) was used to detect antibodies to Encephalitozoon cuniculi in man, using spores derived from tissue culture as antigen. Negligible cross-reactions were found with other microsporidia of vertebrate or of invertebrate origin and there was no cross-reaction with Toxoplasma gondii, using ELISA, immunoperoxidase or immunofluorescence staining. A high prevalence of antibodies to E. cuniculi was found in patients suffering from schistosomiasis, malaria and neurological and psychiatric disorders, but not in healthy individuals.

Experimental encephalitozoonosis in neonatal dogs

The in vivo infection of neonatal dogs by the microsporidian protozoan parasite, Encephalitozoon cuniculi, was studied. Microscopic examination of tissues from infected animals showed granulomatous nephritis, meningoencephalitis, hepatitis, and pneumonitis. A large component of the inflammatory infiltrate consisted of plasma cells and lymphocytes. In addition, hyperplasia of B-lymphocyte-dependent regions of lymph nodes and erythrophagocytosis were consistently seen in infected dogs. Infected dogs developed lymphocytosis, hypergammaglobulinemia, anti-encephalitozoon antibodies, and an antigen-specific blastogenic response to E. cuniculi spores. Lymphocyte blastogenic responses to the lectin phytohemagglutinin A (PHA) were depressed compared to controls. Dogs dying during the 2-month experimental trial were bacteremic. The findings of these experiments suggest that postnatal infection results in a demonstrable although seemingly ineffective immune and inflammatory response without detectable clinical disease.

Cultivation of Besnoitia besnoiti and evaluation of susceptibility of laboratory animals to cultured parasites

Cultivation of Besnoitia besnoiti on five mammalian cell types showed that Vero (green monkey kidney), L929 (mouse fibroblasts) and BEK (bovine embryo kidney) cells were highly susceptible and were almost destroyed after 5 days of incubation, while MDBK (Madin-Darby bovine kidney) and BL (Theileria annulata-infected bovine lymphoid) cells were less affected. Intraperitoneal infection with culture-derived endozoites was fatal for gerbils (Meriones tristrami) and sand rats (Psammomys obesus). Rabbits showed fever, conjunctivitis and orchitis, but survived the infection. Mice, rats, guinea pigs, hamsters and Microtus guentheri did not show signs of illness, but developed specific antibodies to B. besnoiti. B. besnoiti subcultivated for 2 years in BL cells remained virulent for gerbils.

Gastrointestinal mucus, a medium for survival and for elimination of parasitic nematodes and protozoa

Mucus is a sticky visco-elastic material which coats all mucosal surfaces. Florey, in 1955, noted the following three functions for gastrointestinal mucus: protection of the underlying mucosa from chemical and physical injury, lubrication of the mucosal surface to facilitate passage of luminal contents, and removal of parasites by binding and entrapment. In the 31 years since Florey's review, detailed analyses of the composition of mucus and of the biochemistry of mucin glycoproteins, as well as measurements of the physical properties of mucus from different organs and sites have yielded information at the molecular level which provide additional support for his views on its function (Allen, 1981; Forstner, Wesley & Forstner, 1982).

Heterologous antagonistic and synergistic interactions between helminths and between helminths and protozoans in concurrent experimental infection of mammalian hosts

Experimental concurrent infection with two or more parasite species in mammalian host models may result in heterologous antagonistic and synergistic interactions ranging in magnitude from reduced/enhanced growth and fecundity to blockage/enhancement of establishment/expulsion. With some exceptions only, there is a reasonable correlation between the levels of interaction monitored by parasitological and by clinico-pathological parameters. Heterologous antagonistic interactions mediated by functional and specific immunological cross-reactivity occur between closely related parasite species exhibiting a marked immunobiological similarity. In contrast, antagonistic interactions between antigenetically more remote species of helminths, protozoan-induced resistance to helminth infection and helminth-induced suppression of concurrent protozoan infection generally appear mediated by immunologically non-specific factors like macrophage activation and inflammatory reactions. Synergistic heterologous interactions between helminths, helminth-induced enhancement of concurrent protozoan infection and interference with the development and maintenance of resistance to helminth infection in response to concurrent protozoan infection are generally thought to be mediated by non-specific parasite-induced immunosuppression. Concurrent experimental infection is very complex. There are problems and limitations in extrapolating from experimental studies on concurrent infection in laboratory animals to natural polyparasitism. This fact, coupled with the complex influence of ecological factors on the pattern and frequency of concurrent natural infection means that major consequences of natural concurrent parasite infection have not been definitively demonstrated. Appropriately planned and controlled field studies and further laboratory experiments on primate and domestic animal models are imperative for elucidation of the importance of heterologous interactions in concurrent parasite infection for the disease pattern in man and domestic stock. Experimental studies hitherto conducted on concurrent parasite infection pointing to natural heterologous interactions may be a valuable starting point for further studies.

Characterization of Tritrichomonas foetus antigens, using bovine antiserum

Tritrichomonas foetus antigens were identified, using the serum of an Angus heifer that had been repeatedly immunized with suspensions of 1 X 10(8) organisms in Freund's complete adjuvant. Antibody activity against T foetus was determined by dot-blot analysis, using horse-radish peroxidase-conjugated anti-bovine immunoglobulin to detect bound antibody. The antiserum contained antibodies against surface and flagellar components of live or fixed T foetus, as determined by use of immunofluorescence. The antiserum reacted with approximately 38 proteins in a pool of 55 to 60 components resolvable by polyacrylamide-gel electrophoresis of T foetus extracts.

Production and preliminary characterization of murine monoclonal antibodies to Ichthyophthirius multifiliis, a protozoan parasite of fish

An initial panel of 34 hybridomas, each secreting antibodies reactive with an infective theront stage of an Ichthyophthirius multifiliis isolate, was produced. Three of these cell lines, each producing immunoglobulin M class antibodies, were cloned by limiting dilution and were expanded as ascites-producing tumors in syngeneic mice. Three monoclonal antibodies (MAB) reacted with intact whole theronts in an enzyme-linked immunosorbent assay to dilutions of 1:10,000 in ascitic fluids and had a similar pattern of surface and cytoplasmic staining in indirect immunofluorescent tests. Only antigen specified by MAB E6 could be characterized by acrylamide gel electrophoresis and immunoblotting; initial data indicated a molecular weight of 200,000. Physicochemical properties of the determinants recognized by the 3 MAB were tested by pronase digestion and periodate oxidation. Seemingly, a protein, glycoprotein, and carbohydrate were recognized by MAB E6, FE10, and AC8, respectively.

Humoral antibody response of rabbits to experimental infection with Encephalitozoon cuniculi

Six female rabbits (Oryctolagus cuniculus) were experimentally infected intravenously with approximately 1.5 X 10(7) live spores of Encephalitozoon cuniculi. Head tilt was observed as the single clinical sign in only one of the six animals. Antibody response was registered over 68 days postinfection using the indirect immunofluorescence test (IFT) for IgM and IgG, and the carbon immunoassay (CIA). IgG titers reached a level of 160-2560 after a latent phase of 13-28 days, followed by a 2-4 week relatively steep increase. The IgM seroconversion was faster than that of IgG and occurred at the beginning of the antibody response. Thus, simultaneous detection of both IgM and IgG allowed the infection to be identified as recent. Long, short, and episodic antibody responses could be distinguished: the IgG titer continued to increase on Day 68 in one animal (long response) and began to decrease between Days 45 and 63 in three other animals (short response). In two additional animals the seroconversion was very short, occurring between Days 13 and 41, and 28 and 52, respectively (episodic response). The CIA proved to be specific, reliable, and simple to perform; titers were slightly higher than in the IFT. Parasite pseudocysts were detected scattered throughout the brain on Day 68 in four of the six rabbits. The persistence of antigen in the brain did not correlate with antibody response, which in most cases was shorter.

Acquired resistance of black mollies Poecilia latipinna to infection by Ichthyophthirius multifiliis

Changes in the response of black mollies Poecilia latipinna to infection with Ichthyophthirius multifiliis subsequent to single I. multifiliis infections were examined experimentally. Incomplete resistance to infection was established, the degree of which did not depend on the intensity of the initial infection. Resistance was maintained for longer periods, however, by those fish with higher initial levels of infection. Previous experience of infection by their hosts had a significant, though small, effect on the time for which trophozoites remained on the fish. The influence of these results on the population dynamics of the Ichthyophthirius-fish interaction is examined with the aid of simple mathematical models.