Genetic control of immunity to Trichinella spiralis in mice. Response of rapid- and slow-responder strains to immunization with parasite antigens

Lagochilascaris minor: Susceptibility and Resistance to Experimental Infection in Mice Is Independent of H-2 Haplotype and Correlates with the Immune Response in Immunized Animals

Recently, we demonstrated that C57BL/6 mice are more susceptible to experimental lagochilascariosis than BALB/c mice. To investigate the pattern of infection and the role of the genetic background on susceptibility to infection, we studied experimental lagochilascariosis in H-2^a identical B10.A and A/J mice. Infected B10.A mice had a lower survival ratio and more severe lesions in the lungs than did A/J mice. Splenocytes of A/J mice immunized with the crude extract of the parasite showed increased proliferation and produced a higher level of interleukin 10 and interferon-γ in the presence of CE or concanavalin A when compared to B10.A mice. This suggests that resistance of A/J mice may be due to less severe lesions in lungs and other organs and a better immune response to parasite antigens. This paper provides evidence that major histocompatibility complex haplotype does not influence the survival to experimental infection with L. minor.

Nasal immunization with homogenate and peptide antigens induces protective immunity against Trichinella spiralis

Mice were successfully immunized against the intestinal nematode Trichinella spiralis by intranasal administration of a 30-mer peptide antigen with cholera toxin B. Immunized mice developed antigen-specific serum immunoglobulin G1, intestinal immunoglobulin A, and a type 2-biased cytokine response. Intranasal immunization therefore generates the Th2-mediated responses required for immunity against intestinal parasites.

Immunology and genetics of zoonotic infections involving parasites

Zoonoses involving parasites are both common and important, some causing serious diseases. The abilities of such parasites to pass between humans and a variety of vertebrates facilitates their use as experimental model systems. Much can be learned about the host-parasite relationships of zoonotic infections from laboratory-based studies, particularly where it is possible to make use of defined parasite isolates in a variety of host species or in genetically defined strains of a given host. This review focuses on our current understanding of the immunological influences upon host-parasite interactions involving zoonotic parasites and on how such influences are modified by the genetic variability found n populations of both hosts and parasites. Particular emphasis is given to data arising from work with the intestinal parasitic nematode Trichinella spiralis and other isolates of the genus Trichinella.

Oral and parenteral vaccination against Trichinella spiralis infections in high- and low-responder mice

Vaccination by different routes and with different adjuvants is known to influence profiles of immune responses and may be used to overcome genetically determined low-responsiveness to infection. A mouse model of infection with the intestinal nematode Trichinella spiralis was used to investigate the effect of mode of vaccination upon immune responsiveness and worm expulsion phenotype in high- (NIH) and low- (C57 BL/10) responder strains of mice. Muscle larval homogenate antigen was given subcutaneously in Freund's complete adjuvant (FCA) to induce a systemic immune response or with cholera toxin (CT) orally to stimulate mucosal immunity. Both approaches significantly protected NIH mice. Vaccination with FCA was correlated with elevated serum IgG after infection, whereas oral CT-vaccination resulted in increased levels of intestinal IgA. Neither type of vaccination successfully protected the low-responder C57 BL/10 strain and there were no effects on the low antibody levels that infection induced in this strain.

Immune response profiles in vaccinated and non-vaccinated high- and low-responder mice during infection with the intestinal nematode Trichinella spiralis

NIH and C57 BL/10 (B10) mice show genetically determined differences in their response to Trichinella spiralis infection. This study examines the influence of these on parameters of the immune response to infection after vaccination using muscle-larval excretory-secretory antigen in Freund's complete adjuvant. Serum antibody levels were greatly elevated when mice of both strains were vaccinated prior to infection; however, NIH produced significantly higher-level antibody responses than B10. Vaccination accelerated and increased the capacity of mesenteric lymph node T-cells to proliferate in vitro in response to specific antigen stimulation in both mouse strains but, in general, the stimulation indices of NIH cells were higher than those of the B10. The capacity of mesenteric lymph node cells (MLNC) and spleen cells (SC) to produce IL-5 and gamma IFN was measured after specific in vitro stimulation and early gamma IFN secretion was noted in the supernatants of NIH MLNC and SC, but not in B10 SC. Concentrations of IL-5 rose steadily over the first 10-14 days after infection in cell cultures from both strains. Prior vaccination of these animals appeared to enhance cytokine levels. It is postulated that the efficacy of vaccination in NIH mice is a consequence of their genetically determined capacity to produce early and high-level responses to the antigens of T. spiralis and to express these in intestinal effector mechanisms.

Expulsion of Trichostrongylus colubriformis by high and low responder guinea-pigs

Guinea-pigs with genetically determined susceptibility to infection with Trichostrongylus colubriformis (or low responders) rejected both primary and secondary infections with this parasite more slowly than resistant animals (high responders). Low responders were not protected with a vaccination procedure which was highly effective in outbred animals. The relatively poor protective immune responses that develop in low responder guinea-pigs are evocative of the responses of the natural host to infection with this parasite and suggest that low responder guinea-pigs have potential for the study of T. colubriformis protective antigens and for the development of adjuvants to enhance antiparasitic effector responses in vaccinated hosts.

Immune response profiles in responsive and non-responsive mouse strains infected with Heligmosomoides polygyrus

The immune response to a primary infection with Heligmosomoides polygyrus was monitored in three strains of mice (SJL, BALB/c, CBA) with different degrees of susceptibility to the infection. Parameters measured included circulating leucocyte numbers, T and B cell numbers in the mesenteric lymph nodes, the mucosal mast cell response, and quantitative and qualitative antibody responses to parasite antigens. From these data it would appear that resistance was governed by the relative speed and magnitude of the immune response mounted by the host. The possible immunological mechanisms governing this process are discussed.

Immunization against experimental coccidiosis produces contrasting results in inbred mice of differing susceptibility to infection

Pretreatment of inbred mice with intravenous and/or intraperitoneal injection of an antigen prepared from sporozoites of Eimeria vermiformis modulated the course of infection with the parasite in a manner that depended on the resistance-susceptibility phenotype of the host. Mice with a resistant background (BALB) produced more oocysts and those with a susceptible background (C57BL) produced fewer oocysts than their respective controls. The optimum conditions for producing these effects were established, and evidence is presented which suggests that the phenomenon might also apply in the target host, the chicken.

Genetic variation in resistance to parasitic infection: experimental approaches and practical applications

Parasitic infections remain a major threat to the successful maintenance of domestic livestock. Control is still centered around management and husbandry, and the use of chemotherapeutic compounds. However, the spread of drug resistance in many important protozoal and helminth infections is placing an increasing emphasis on the development of alternative forms of control. At the present time vaccination is available for only a limited number of parasites, and may never be practical or cost-effective for some of the most important infections. This review examines current views of the mechanisms, control and likely value of genetically determined differences in resistance to parasitic infection. There is an extensive literature dealing with experimental analyses of genetic variation to parasitic infection in both laboratory and domestic species, and a growing interest in the application of this information in the field of practical parasite control.

The immune response of male DSN hamsters to a primary infection with Ancylostoma ceylanicum

The immune response of hamsters to a chronic hookworm infection has been investigated. Ancylostoma ceylanicum caused long term infections in hamsters which were associated with prominent changes in secondary lymphoid organs. The mesenteric lymph nodes and spleens increased rapidly in size stabilizing at approximately 3-4 times the weight in control animals by weeks 3-7. Cells from both the mesenteric lymph node and spleen, after an initial period of increased blast cell activity, became less reactive in the latter stages of infection. Serum antibody responses were marked, commencing in weeks 3-4 and increasing in intensity throughout the 10 week period of measurement. The results are discussed in relation to their contribution to the understanding of human hookworm infection.

Nature and nurture: overcoming constraints on immunity

Parasitic infections in man and domestic animals exhibit two striking characteristics (a) their prevalence is high, but infections are unequally distributed among individuals within populations and (b) immunity is often slow to develop and appears, at best, only partially effective. Recent immunological and epidemiological studies suggest that effective immunity can develop, but that high prevalence within populations reflects the operation, not only of socio-economic and climatic factors, or husbandry practices, but also of powerful environmentally induced constraints upon the development of resistance. Immunogenetic studies suggest the operation of additional constraints upon the development of resistance. Immunogenetic studies suggest the operation of additional constraints which reflect individual genetic characteristics, and which influence the ability to develop and express effective immunity. A full understanding of all constraints is necessary before levels of population and individual resistance to infection can be increased; the need for such understanding has become more pressing with the prospect that anti-parasite vaccines may become available. Two aspects of environmentally induced constraints are considered, those arising from nutritional inadequacies and those resulting from exposure to infection in early life. Both are discussed primarily in terms of helminth parasites. Genetically determined constraints are discussed with reference to MHC-restricted recognition of malarial peptide vaccines and in terms of Class II molecule-directed control of T-cell function in Leishmania infections. Genetic influences are also considered from the standpoint of inflammatory cell function, in immunity against intestinal nematodes and in vaccine-induced immunity against Schistosoma. Finally, parasite-induced constraints, particularly those which down-regulate protective responses are discussed briefly.