Raymond E. Kuhn

Mice infected with the larvae of Taenia crassiceps exhibit a Th2-like immune response with concomitant anergy and downregulation of Th1-associated phenomena.

Infection of intermediate hosts with eggs of taeniid parasites results in a larval infestation known as cysticercosis. A number of studies have indicated that cysticercosis is associated with immunosuppression, although little is known about the mechanisms involved. In the present study, mice infected with the larvae of Taenia crassiceps were found to exhibit a pronounced energy, which preferentially affected T-cells located anatomically close to the parasite. This anergy was linked to late events in the T cell activation pathway; that is, stimulation through the T cell receptor(TCR)/CD3 complex by Concanavalin-A, or plate-bound monoclonal antibodies (mAb) to TCR alpha beta or CD3 epsilon, or combinations of phorbol ester and ionomycin (all of which can bypass early membrane-related events), failed to fully activate T lymphocytes. The relative proximity of T cells to the parasite was directly related to upregulation of IL-4 and downregulation of IL-2 production. In addition, the profiles of parasite-specific Abs showed an exclusive increase of serum IgG1 during infection. Taken together, the data suggest that infection of mice with larvae of T. crassiceps alters the balance of CD4+ Th cells by upregulating Th2 and downregulating Th1 cells located in close proximity to the parasite.

The systemic immune response of BALB/c mice infected with larval Taenia crassiceps is a mixed Th1/Th2-type response

The subsets of lymphocytes and cytokines regulating the site-specific immune response in experimental cysticercosis (Taenia crassiceps) are not known. This study investigated the cells present at the site of infection (PECs) using flow cytometry and measured the cytokines produced by these cells through 50 days of infection. The results showed an expansion of B220+CD5+, B220+CD5-, alpha beta TCR+CD4+ and CD8+ cells coincident with a transient increase in IL-10 production. After the initial increase, the percentage of B220+CD5- and helper T cells decreased with a concomitant decrease in IL-10 production. CD8+ T cells continued to increase throughout infection and gamma delta TCR+ cells increased after 10 days of infection. PECs demonstrated an increased IFN-gamma and IL-4 production throughout infection when stimulated with larval antigens. Because a Th2-type polarization has been shown for spleen cells from infected BALB/c mice, cytokine profiles of spleen cells and PECs in response to ConA and larval antigens were compared. ConA and antigen-specific stimulation of spleen cells from 50-day-infected mice produced increased amounts of IL-10 while PECs showed a decreased IL-10 production suggesting that anatomically distinct lymphoid populations produce different cytokines and promote different types of responses. Surprisingly, late in infection the levels of IL-4 and IFN-gamma in serum increased substantially (460-fold and 100-fold, respectively). The systemic immune response of BALB/c mice during experimental cysticercosis, therefore, is a mixed Th1/Th2-type response.

ANTIGEN-ANTIBODY ANALYSES IN NEUROCYSTICERCOSIS

In this report we show that there are 37 polypeptides of larval Taenia solium which react with antibodies from humans with neurocysticercosis. Six of these 37 polypeptides are recognized by antibodies present in the sera of both patients and control individuals. Thus, a minimum of 31 antigens are specific for cysticerci. We describe herein the antigens more frequently recognized by the patients, and the immunoglobulin classes favored in antibody production against each of the cysticercal antigens. It was found that there are 10 major polypeptides with molecular weights of 200,000, 64,000, 62,000-61,000, 53,000, 45,000, 41,000, 36,000-35,000, 30,000 and 16,000 daltons. About 65% of the larval components found to be antigenic are glycoproteins with oligosaccharide chains containing N-acetyl-D-glycosamine and alpha-D-galactose. These results suggest that the sugar moieties of glycoproteins may play a role in the antigenicity of larval T. solium. Based on these observations polypeptides with molecular weights of 64,000, 53,000, and 32,000-30,000 daltons are probably the best choice as sources of antigen to develop an optimal immunological test for the serological diagnosis of neurocysticercosis.

TRYPANOSOMA CRUZI-INDUCED SUPPRESSION OF THE PRIMARY IMMUNE RESPONSE IN MURINE CELL CULTURES TO T-CELL-DEPENDENT AND -INDEPENDENT ANTIGENS

In vitro antisheep erythrocyte (SRBC) and antitrinitrophenyl (TNP) antibody responses of spleen cells obtained from C57BL/6 mice infected with Trypanosoma cruzi were reduced as early as 6 days postinfection and not detectable after 18 days of infection. Lymph node cells had normal antibody responses to SRBC and TNP in vitro until the 11th day of infection, after which responses were diminished. By day 31 of infection, lymph node cells were unresponsive to both SRBC and TNP in vitro. Not only were the antibody responses of spleen and lympho node cells to T-cell-dependent and -independent antigens progressively reduced as the period of infection increased, but in addition, the effect of lymphoid cell density and antigen dose on antibody production underwent several sequential changes. As the infection advanced, low densities of cultured lymphoid cells and low doses of antigen were ineffective in eliciting a detectable immune response, whereas high densities of lymphoid cells and high doses of antigen resulted in responses approximately equivalent to that observed with normal cells under the same conditions. Results of cell mixing studies have shown that a plastic-adherent, macrophage-like cell plays a major role in the suppressed humoral responses observed in this host-parasite system.

Growth and development of larval Taenia crassiceps (Cestoda)—I.: Aneuploidy in the anomalous orf strain

Abstract The diploid chromosome number for the KBS strain of larval Taenia crassiceps was found to be 16; for the ORF strain, the diploid number is 14. The chromosomes are morphologically identical in the two strains, except that one homologous pair is missing in ORF larvae. It is concluded that the morphologic, antigenic and reproductive abnormalities described for the ORF strain are a result of aneuploidy.

Immunochemical detection of antigens of larval Taenia solium and anti-larval antibodies in the cerebrospinal fluid of patients with neurocysticercosis ☆

A simple and quantitative enzyme-linked immunosorbent assay (ELISA) has been developed for the detection of antigens of larval Taenia solium in the cerebrospinal fluid (CSF) of patients with cerebral cysticercosis. Another ELISA was developed for detecting antibodies in CSF against larval antigens. The examination of sixteen patients with clinical diagnosis of cerebral cysticercosis revealed that eleven patients had both circulating larval antigens and anti-larval IgG (but not IgM) antibodies in their cerebrospinal fluids. Of these patients, those with surgically and histologically confirmed infections were all positive by the two tests. CSF samples from nine normal individuals and from six patients suffering from proven neurological disorders other than neurocysticercosis were negative for both tests. In development of these assays it was found that cross-linking of antigens to microtiter plates further improved the performance of the ELISA. The results of this study suggest that either or both of these tests may be useful in discriminating between neurocysticerosis and other clinically related diseases.

Growth and development of larval Taenia crassiceps (Cestoda). III. The relationship between larval biomass and the uptake and incorporation of 14C-leucine

Abstract The rate of increase in larval biomass in the abnormal ORF strain of Taenia crassiceps was significantly greater than in the normal KBS strain during 26 weeks of infection. Larvae of both strains (in terms of biomass) increased more rapidly in female mice than in male mice. In vitro uptake and incorporation rates of 14C-leucine were found to be inversely proportional to the increase in larval biomass of both ORF and KBS strains, when measured at intervals of 3 weeks throughout a 26-week infection period. There was no correlation between larval biomass, sex of host, and ratios of uptake rate to incorporation rate of 14C-leucine, in either strain. The mean ratio of uptake to incorporation rate of 14C-leucine was significantly less in the ORF strain, indicating that ORF larvae incorporate leucine at significantly higher rates than KBS larvae.

Ultrastructure of spermiogenesis and the spermatozoon in Taenia crassiceps strobilae WFU strain (Cestoda, Cyclophyllidea, Taeniidae) from golden hamsters

Strobilae from Taenia crassiceps (WFU strain) were obtained from outbred hamsters (Mesocricetus auratus) by feeding them viable metacestodes maintained by intraperitoneal passage in female Balb/c mice. Mature and gravid proglottids from strobilae were recovered from hamster intestines and fixed for light and electron microscopy. By light microscopy, the expected structure of taeniid proglottids was observed. Ultrastructural analysis of ten proglottids showed that testicular follicles and vas deferens contained filiform spermatids, with a single axoneme, and an elongated helicoidal nucleus inserted between the axoneme and the spiraled cortical microtubules. At the apical cone, a single crest-like body was found and mature spermatids also exhibited transverse intracytoplasmic walls. The morphology and characters of the spermatids in T. crassiceps conform to type III spermiogenesis, which has been described in other taeniids.

INFRAPOPULATION DYNAMICS OF A WILD STRAIN OF TAENIA CRASSICEPS (WFU) (CESTODA: TAENIIDAE) IN BALB/cJ MICE

Taenia crassiceps cysticerci form large infrapopulations that persist in the tissues of their rodent hosts. Early infrapopulation growth appears inhibited and is followed by rapid increases that appear not to be controlled by the host immune response. This investigation was undertaken to examine the infrapopulation growth dynamics of a normally developing strain (WFU) of T. crassiceps during a 60-day primary intraperitoneal (i.p.) infection. Three, 6, 9, 14, 28, and 60 days after i.p. inoculation of 5 cysticerci, mice were killed, and the numbers of larvae, developmental stage, and buds per larva were recorded. Larval infrapopulation abundance increased exponentially beginning on day 6 postinoculation (PI), indicating an initial lag in reproduction. A stage-structured exponential growth model, assuming no mortality, fits the larval infrapopulation dynamics in terms of the numbers of larvae in reproductive and nonreproductive stages, indicating that cysticerci evade or suppress (or both) host immune mechanisms that are parasite restrictive after the first week of infection.

Trypanosoma cruzi affects nitric oxide production by murine peritoneal macrophages

Macrophages from mice that are infected with various intracellular pathogens including Leishmania major, Trypanosoma cruzi, and Salmonella typhimurium are stimulated to produce large quantities of nitric oxide (NO). Both viable and heat-treated L. major amastigotes have been shown to be effective co-signals for NO production in vitro. NO produced by macrophages has anti-microbial and immunosuppressive functions in an immune response. We have shown previously that NO plays a complicated role in T. cruzi infections since macrophages are important both in mediating an immune response against the parasite as well as in mediating immunosuppression. In this study we examined how T. cruzi affects NO production by macrophages from C3HeB/FeJ and C57BL/6 mice in vitro. We found that live trypomastigotes neither stimulate nor decrease NO production by interferon (IFN)-gamma-activated macrophages. However, heat-treated or glutaraldehyde-fixed trypomastigotes of T. cruzi significantly decrease NO production by IFN-gamma-activated macrophages and as a result decrease macrophage-mediated trypanocidal and immunosuppressive activity. We have determined that this decrease in NO production by T. cruzi is not due to stimulation of transforming growth factor-beta production and involves tumor necrosis factor-alpha only in C3HeB/FeJ macrophages. This study demonstrates the complexity of the T. cruzi-macrophage interaction as well as confirms previously demonstrated differences between macrophages from 2 strains of mice.