Immunotherapy with live BCG plus heat killed Leishmania induces a T helper 1-like response in American cutaneous leishmaniasis patients

Previous work has shown that American cutaneous leishmaniasis (ACL) patients treated with viable BCG plus heat killed promastigotes of Leishmania amazonensis show the same rate of cure as patients receiving conventional chemotherapy. The treatment is safe and economical, but the immunological correlates of cure have not been examined. In the present study, T cell responses have been analysed in 43 ACL patients, including patient groups sampled before and after therapy, and in 10 endemic controls. Lymphocyte proliferation, interferon (IFN)-gamma and interleukin (IL)-5 responses to crude antigen (L. amazonensis, MEL; Mycobacterium tuberculosis PPD; M. bovis BCG) stimulation, and serum IL-5 levels, were analysed. In endemic volunteers, proliferative responses to BCG were high and IFN-gamma responses low. In contrast, localized cutaneous (LCL) and mucocutaneous (MCL) patients showed low proliferative and high IFN-gamma responses to BCG. Treatment enhanced the IFN-gamma response and further decreased the proliferative response to BCG, especially in MCL patients. LCL and MCL patients showed an increase in proliferative and IFN-gamma responses to MEL with treatment, but the response was not exaggerated in MCL patients, either before or after treatment, compared to LCL patients. IL-5 production was low in T cell assays, and > 62% of untreated patients had very low serum IL-5 levels. There were no significant changes in serum IL-5 with treatment. Overall results show enhanced antigen-specific IFN-gamma responses to the two components of the immunotherapy, live M. bovis BCG and heat killed L. amazonensis, which is consistent with a shift in balance of T cell response towards a T helper 1 response and clinical cure mediated by IFN-gamma.

IL-13 is a susceptibility factor for Leishmania major infection

Leishmania major infection is useful as an experimental model to define factors responsible for the development and maintenance of Th cell immune responses. Studies using inbred mouse strains have identified that the Th1 response characteristic of C57BL/6 mice results in healing, whereas BALB/c mice fail to control the infection due to the generation of an inappropriate Th2 response. We now demonstrate that IL-13 is a key factor in determining susceptibility to L. major infection. Overexpression of IL-13 in transgenic mice makes the normally resistant C57BL/6 mouse strain susceptible to L. major infection even in the absence of IL-4 expression. This susceptibility correlates with a suppression of IL-12 and IFN-gamma expression. Furthermore, using BALB/c mice deficient in the expression of IL-4, IL-13, or both IL-13 and IL-4, we demonstrate that IL-13-deficient mice are resistant to infection and that there is an additive effect of deleting both IL-4 and IL-13.

Intra and inter-specific microsatellite variation in the Leishmania subgenus Viannia

Leishmania species of the subgenus Viannia are responsible for a large proportion of New World leishmaniasis. Here we report the development of a set of microsatellite markers which are able to discriminate between all species within the subgenus Viannia, including the closely related species pairs: Leishmania (V.) braziliensis and Leishmania (V.) peruviana; Leishmania (V.) panamensis and Leishmania (V.) guyanensis. Potential species hybrids were uncovered in the analysis. These markers are sufficiently polymorphic such that within-species epidemiological, population and genetic studies are theoretically possible for all species analyzed.

Status of protozoan genome analysis: trypanosomatids

The three trypanosomatid genome projects have employed common strategies which include: analysis of pulsed-field gel electrophoretic chromosomal karyotypes; physical mapping using big DNA (cosmid, pacmid P1, bacterial artificial chromosome, yeast artificial chromosome) libraries; partial cDNA sequence analysis to develop sets of expressed sequence tags (ESTs) for gene discovery and use as markers in physical mapping; genomic sequencing; dissemination of information through development of web-sites and ACeDB-based fully integrated databases; and establishment of functional genomics programmes to maximize useful application of genome data. Highlights of the projects to date have been the demonstration that, despite extensive chromosomal size polymorphisms for diploid homologues within Africa trypanosomes, T. cruzi or Leishmania, the physical linkage groups for markers on each chromosome are retained across all isolates/species studied within each group. For African trypanosomes, detailed analysis of chromosome 1 has demonstrated that repetitive sequences and the two retroposon-like elements RIME and INGI are localized to a defined region at one end of the chromosome, with the bulk of the central region of the chromosome containing genes coding for expressed proteins. Comparative mapping shows that, although subtelomeric changes account for a large proportion of the polymorphism in chromosome size in African trypanosomes, there are significant expansions and contractions in regions across the entire chromosome. The highlight of the genomic sequencing projects has been the demonstration of just 2 putative transcriptional units of chromosome 1 of Leishmania major, extending on opposite strands from a point in the central region of the chromosome. A similar observation made on 93.4 kb of contiguous sequence for T. cruzi chromosome 3 suggests the presence of promoter and regulatory elements at the junctions of large polycistronic transcriptional units. All data obtained from the genome projects are made available through the public domain, which has prompted changing philosophies in how we approach analysis of the biology of these organisms, and strategies that we can employ now in the search for new therapies and vaccines.

Immunostimulatory DNA as an adjuvant in vaccination against Leishmania major

Oligodeoxynucleotides (ODN) which contain immunostimulatory CG motifs (CpG ODN) can promote T helper 1 (Th1) responses, an adjuvant activity that is desirable for vaccination against leishmaniasis. To test this, susceptible BALB/c mice were vaccinated with soluble leishmanial antigen (SLA) with or without CpG ODN as adjuvant and then challenged with Leishmania major metacyclic promastigotes. CpG ODN alone gave partial protection when injected up to 5 weeks prior to infection, and longer if the ODN was bound to alum. To demonstrate an antigen-specific adjuvant effect, a minimum of 6 weeks between vaccination and infection was required. Subcutaneous administration of SLA alone, SLA plus alum, or SLA plus non-CpG ODN resulted in exacerbated disease compared to unvaccinated mice. Mice receiving SLA plus CpG ODN showed a highly significant (P < 5 x 10(-5)) reduction in swelling compared to SLA-vaccinated mice and enhanced survival compared to unvaccinated mice. The modulation of the response to SLA by CpG ODN was maintained even when mice were infected 6 months after vaccination. CpG ODN was not an effective adjuvant for antibody production in response to SLA unless given together with alum, when it promoted production of immunoglobulin G2a, a Th1-associated isotype. Our results suggest that with an appropriate antigen, CpG ODN would provide a stable, cost-effective adjuvant for use in vaccination against leishmaniasis.

Multiple causes of size variation in the diploid megabase chromosomes of African tyrpanosomes

The chromosomes of many protozoans are polymorphic in size, but African trypanosomes contain diploid homologues which are exceptionally size-polymorphic. We present the first complete analysis of the structure of a Trypanosoma brucei megabase chromosome which reveals the concentration of repetitive sequence, non-random distribution of transposon-like elements, and a hemizygous variant surface glycoprotein gene expression site. Subsequent comparative analyses of size-polymorphic homologues show that the repetitive regions are highly polymorphic, as demonstrated in studies on the chromosomes of other protozoan parasites. We show that a large number of the transposon-like elements are located in these regions. However, although we have shown elsewhere that synteny is maintained in coding regions, homologous chromosomes may vary along their entire length. Thus, the variable chromosomal location of variant surface glycoprotein expression gene sites, the expansion and contraction of repetitive DNA, the number of putative transposons, sequence polymorphism at chromosome ends, and expansion and contraction within or between coding regions all contribute to huge chromosomal size polymorphisms in T brucei.

The Leishmania genome comes of Age

The Leishmania Genome Network (LGN) was born in Rio de Janeiro, Brazil in 1994. In the short period that has elapsed since then, the LGN has focused solely on the acquisition of the resources, and hence data, that have enabled a rational approach to genomic sequencing of the reference strain, Leishmania major Friedlin. This has now been achieved. In this review, Alasdair Ivens and Jennie Blackwell, secretary and chairman of the LGN, respectively, re-examine the approaches that were adopted, comment on some of the interesting data that have been obtained and introduce some genome-wide approaches that will facilitate functional studies of the parasite.

Fetal alcohol exposure and temporal vulnerability: regional differences in cell loss as a function of the timing of binge-like alcohol exposure during brain development

This study was conducted to determine the temporal and regional vulnerability of the brain as a function of exposure to alcohol during brain development. Our goal was to manipulate the timing of alcohol exposure and assess the relative risk of cell loss in two different brain regions. Groups of timed pregnant Sprague-Dawley rats received binge-like alcohol exposure during either the first 10 days (first-trimester equivalent) or second 10 days of gestation (second-trimester equivalent), or the combination of first- and second-trimester equivalents for prenatal treatments. Offspring from some of the animals exposed to alcohol during the combined first- and second-trimester equivalent were reared artificially from postnatal days (P) 4 through 9 (part of the third-trimester equivalent) and also received binge-like alcohol during this period, producing animals that were exposed to alcohol during all three trimesters equivalent. Offspring from untreated dams were also reared artificially and received alcohol from only P4-9, thus creating animals that were exposed to alcohol only during part of the third-trimester equivalent. All pups were perfused on P10. Appropriate controls (nutritional and normally reared) were matched to every alcohol treatment combination. Peak blood alcohol concentrations were not different among the treatment groups for a given sampling time. Total cell numbers in the cerebellum (Purkinje and granule cells) and the olfactory bulb (mitral and granule cells) were estimated by the unbiased stereological technique, the optical disector. In terms of temporal vulnerability, alcohol exposure during the equivalent of all three trimesters resulted in a greater reduction in cerebellar Purkinje cell numbers compared with exposure to alcohol during the third-trimester equivalent, whereas both groups had a significant reduction in cell number compared with all other timing groups. Cerebellar granule cell number was reduced after alcohol exposure during all three trimesters equivalent, compared with all other timing groups. Alcohol exposure during the third-trimester equivalent resulted in a decrement in the number of olfactory bulb mitral cell numbers compared with all other groups, but there were no differences among the timing groups in numbers of olfactory bulb granule cells. When the cell loss in the two regions was compared within each alcohol treatment group to determine the relative regional vulnerability, the primary salient finding was that cerebellar Purkinje cells were more vulnerable to alcohol-induced loss subsequent to exposure during all three trimesters equivalent. No other regional differences were detected. These results extend earlier findings by showing that alcohol exposure during different periods of brain development results in regional differences in cell loss as a function of the timing of alcohol exposure during brain development and illustrate the variability of alcohol-induced neuronal loss.

Evidence for a functional repeat polymorphism in the promoter of the human NRAMP1 gene that correlates with autoimmune versus infectious disease susceptibility

A polymorphism in the promoter of human NRAMP1 encodes a Z-DNA forming dinucleotide repeat with four alleles: (1) t(gt)5ac(gt)5ac(gt)11g; (2) t(gt)5ac(gt)5 ac(gt)10g; (3) t(gt)5ac(gt) ac(gt)9g; and (4) t(gt)5ac(gt)9g. Alleles 1 and 4 are rare (gene frequencies approximately 0.001); alleles 2 and 3 occur at gene frequencies approximately 0.20-0.25 and approximately 0.75-0.80, respectively. Here, luciferase reporter gene constructs are used to show that the four alleles differ in their ability to drive gene expression. In the absence of exogenous stimuli, alleles 1, 2, and 4 are poor promoters; allele 3 drives high expression, indicating that the repeat itself has endogenous enhancer activity. All four alleles show a similar percentage enhancement of reporter gene expression in the presence of interferon-gamma, consistent with the multiple interferon-gamma response elements both 5' and 3' of the Z-DNA forming repeat. However, while the addition of bacterial lipopolysaccharide (LPS) has no effect on alleles 1 and 4, it causes significant reduction in expression driven by allele 2 and enhances expression driven by allele 3, suggesting that the juxtaposition of LPS related response elements (NFkappaB, AP-1, NF-IL6) may be differentially affected by the two commonly occurring alleles. These results are consistent with the hypothesis that chronic hyperactivation of macrophages associated with allele 3 is functionally linked to autoimmune disease susceptibility, while the poor level of NRAMP1 expression promoted by allele 2 contributes to infectious disease susceptibility. Conversely, allele 3 protects against infectious disease and allele 2 against autoimmune disease. Hence, alleles that are detrimental in relation to autoimmune disease susceptibility may be maintained in the population because they improve survival to reproductive age following infectious disease challenge.

Tumour necrosis factor alpha and mucocutaneous leishmaniasis

Allelic associations between polymorphisms at the tumour necrosis factor (TNF) locus within the major histocompatibility complex (MHC) and susceptibility to a range of autoimmune and infectious diseases have been established in humans. Among these is the severe and debilitating mucocutaneous form of leishmaniasis (MCL) caused by Leishmania braziliensis. This was preempted by the demonstration of high levels of circulating TNF-alpha in the sera of patients presenting with clinical mucocutaneous disease. Here, Jennie Blackwell looks at the implications this might have for the diagnosis and treatment of mucocutaneous disease, and the broader implications that the positive and negative immunomodulatory roles of TNF-alpha have in maintaining apparently detrimental alleles in the population.

Genetic regulation of macrophage activation: understanding the function of Nramp1 (=Ity/Lsh/Bcg)

The Nramp1 gene was originally described as Ity/Lsh/Bcg, a single gene controlling resistance and susceptibility of inbred mice to a range of intramacrophage pathogens. Functional studies demonstrated that Ity/Lsh/Bcg had multiple pleiotropic effects on macrophage activation pathways, broadening interest in the gene to include its candidacy as an autoimmune disease susceptibility gene. In 1993 the gene was positionally cloned and found to encode a polytopic integral membrane protein of unknown function. Subsequent studies have localized the protein to late endosomal and lysosomal compartments, and demonstrated that it functions as an iron transporter. Precisely how this function influences macrophage activation pathways is still under investigation, but is likely to include direct effects on pathogen survival in the endosomal/lysosomal compartment as well as influences on intracellular signalling pathways and in regulating mRNA stability. Several studies now provide evidence for a role for NRAMP1 in determining human susceptibility to autoimmune (rheumatoid arthritis. juvenile rheumatoid arthritis, diabetes, Crohn's disease) and infectious (tuberculosis, leprosy) diseases. Amongst these. data are accumulating to support the hypothesis that a functional Z-DNA forming repeat polymorphism in the promoter region of human NRAMP1 contributes directly to disease susceptibility. Four alleles have been observed, alleles 1 and 4 are rare (gene frequencies approximately equal to 0.001), alleles 2 and 3 occur at gene frequencies approximately 0.25 and approximately 0.75, respectively. In the absence of exogenous stimuli, alleles 1, 2 and 4 are poor promoters of gene expression in a luciferase reporter gene system; allele 3 drives high expression. Allele 3 shows allelic association with autoimmune disease susceptibility, allele 2 with infectious disease susceptibility. Hence, balancing selection is likely to be maintaining these two alleles in human populations. Although the association of NRAMP1 with autoimmune disease susceptibility may be related to any one of the multiple pleiotropic effects associated with macrophage activation, the function of NRAMP1 as an iron transporter now prompts more interesting speculation that regulation of iron transport may contribute directly to the disease phenotype in arthritic disease. Patients suffering from rheumatoid arthritis show increased deposition of iron in the synovial membrane, which may contribute to free radical generation and local inflammation. Further analysis of NRAMP1 function will continue to be of importance in understanding the molecular basis to autoimmune and infectious disease susceptibility.

Identification and characterisation of a functional peroxidoxin from Leishmania major

Leishmania spp. encounter damaging oxygen metabolites from endogenous metabolic processes as well as from exogenous sources, such as inside the gut of the sandfly vector and within host macrophages. The recently described peroxidoxin protein family form part of a novel pathway for metabolising hydrogen peroxide that, in trypanosomatids, links peroxide reduction to NADPH oxidation via trypanothione. Here we report the cloning and characterisation of the Leishmania major peroxidoxin gene, tryparedoxin peroxidase (TryP). TryP is a multi-copy gene arranged in a complex tandem array located on the size polymorphic homologues of chromosome 15. Northern analysis showed that TryP expresses a single 1.6 kb mRNA throughout promastigote development. TryP encodes a 22-kDa protein with two conserved cysteine-containing domains that defines it as a 2-Cys peroxidoxin. Purified recombinant TryP protein catabolised hydrogen peroxide in the presence of the tryparedoxin homologue from Crithidia fasciculata (Cf-TryX), trypanothione, trypanothione reductase and NADPH. The demonstration that L. major utilises a three-protein peroxidase system confirms that this is a mechanism of protection against oxidative damage in this parasite.

Localisation of Nramp1 in macrophages: modulation with activation and infection

The murine natural resistance-associated macrophage protein, Nramp1, has multiple pleiotropic effects on macrophage activation and regulates survival of intracellular pathogens including Leishmania, Salmonella and Mycobacterium species. Nramp1 acts as an iron transporter, but precisely how this relates to macrophage activation and/or pathogen survival remains unclear. To gain insight into function, anti-Nramp1 monoclonal and polyclonal antibodies are used here to localise Nramp1 following activation and infection. Confocal microscope analysis in uninfected macrophages demonstrates that both the mutant (infection-susceptible) and wild-type (infection-resistant) forms of the protein localise to the membranes of intracellular vesicular compartments. Gold labelling and electron microscopy defines these compartments more precisely as electron-lucent late endosomal and electron-dense lysosomal compartments, with Nramp1 colocalizing with Lamp1 and cathepsins D and L in both compartments, with macrosialin in late endosomes, and with BSA-5 nm gold in pre-loaded lysosomes. Nramp1 is upregulated with interferon-(gamma) and lipopolysaccaride treatment, coinciding with an increase in labelling in lysosomes relative to late endosomes and apparent dispersion of Nramp1-positive vesicles from a perinuclear location towards the periphery of the cytoplasm along the microtubular network. In both control and activated macrophages, expression of the protein is 3- to 4-fold higher in wild-type compared to mutant macrophages. In Leishmania major-infected macrophages, Nramp1 is observed in the membrane of the pathogen-containing phagosomes, which retain a perinuclear localization in resting macrophages. In Mycobacterium avium-infected resting and activated macrophages, Nramp1-positive vesicles migrated to converge, but not always fuse, with pathogen-containing phagosomes. The Nramp1 protein is thus located where it can have a direct influence on phagosome fusion and the microenvironment of the pathogen, as well as in the more general regulation of endosomal/lysosomal function in macrophages.

Polymorphism in tumor necrosis factor genes associated with myasthenia gravis

The aim of this study was to analyze associations between myasthenia gravis (MG) and polymorphisms in the tumor necrosis factor (TNF) region in 79 Swedish patients and 155 unrelated controls. The frequency of the TNFa2 allele of a microsatellite located 3.5 kb upstream of the lymphotoxin alpha (LT-alpha) gene in the TNF region was found to be increased in overall MG patients compared to controls. The frequency of the short 5.5 kb fragment (TNFB * 1) of a bi-allelic NcoI RFLP polymorphism located at the first intron of the LT-alpha gene was increased in patients with an early onset of disease compared to patients with a later onset.

The molecular karyotype of the megabase chromosomes of Trypanosoma brucei and the assignment of chromosome markers

We present the molecular karyotype of the megabase chromosomes of Trypanosoma brucei stock TREU927/4 (927). We have identified 11 diploid chromosomes ranging in size from 1 to 5.2 Mb approximately and pairs of homologues differ in size by up to 15%. A total of 401 cDNA probes were hybridised to T. brucei stock 927 chromosomes and 168 chromosome-specific markers were defined. Most of these markers were hybridised to the separated chromosomal DNA of two other cloned field isolates and four F1 progeny clones from a laboratory cross. The chromosomes vary in size by up to two and a half times between stocks and the DNA content of the 11 pairs of homologues varies by up to 33% in different stocks. Stock 927 contains the smallest chromosomes and the least nuclear genomic DNA. Nevertheless, all 11 syntenic groups of cDNA probes are maintained in all stocks. In the F1 hybrids only we have identified one extra PFG band to which none of our probes hybridise. We have shown that probes thought to be specific for the bloodstream-form variant surface glycoprotein expression sites hybridise to different chromosomes in different stocks and may hybridise to either one or both of a homologous pair of chromosomes. We have also determined the chromosomal location of the ribosomal RNA gene arrays.

Evidence that genetic susceptibility to Mycobacterium tuberculosis in a Brazilian population is under oligogenic control: linkage study of the candidate genes NRAMP1 and TNFA

SETTING

A study of multicase tuberculosis pedigrees from Northern Brazil.

OBJECTIVE

To determine the model of inheritance for genetic susceptibility to tuberculosis, and to test the hypothesis that TNFA and NRAMP1 are candidate susceptibility genes.

DESIGN

The study sample included 98 pedigrees, 704 individuals and 205 nuclear families. Segregation analyses were performed using the programs POINTER and COMDS. Combined segregation and linkage analysis was carried out within COMDS. Non-parametric linkage analyses were performed using BETA.

RESULTS

A sporadic model for disease distribution in families was strongly rejected, as were polygenic and multifactorial models. A codominant single gene model provided the best fit (P < 0.001) to the data using POINTER. COMDS extended the analysis to compare single-gene and two-gene models. A general two-locus model for disease control was marginally favoured (0.01 < P < 0.05) over the codominant single-gene model. No evidence was found for linkage between susceptibility to disease per se and the TNF gene cluster. Weak linkage was observed using COMDS for genes (IL8RB, P = 0.039; D2S1471, P = 0.025) tightly linked (< 150 kb) to NRAMP1, but not for NRAMP1 itself.

CONCLUSIONS

Tuberculosis susceptibility in this region of Brazil is under oligogenic control. Although a minor role for TNFA and NRAMP1 cannot be excluded, our data suggest that neither is a major gene involved in this oligogenic control.

Genetic control of immune response to recombinant antigens carried by an attenuated Salmonella typhimurium vaccine strain: Nramp1 influences T-helper subset responses and protection against leishmanial challenge

Attenuated strains of Salmonella typhimurium have been widely used as vehicles for delivery and expression of vaccine antigens in murine models of infectious disease. In mice, early bacterial replication following infection with S. typhimurium is controlled by the gene (Nramp1, formerly Ity/Lsh/Bcg) encoding the natural-resistance-associated macrophage protein (Nramp1). Nramp1 regulates macrophage activation and has multiple pleiotropic effects, including regulation of tumor necrosis factor alpha, interleukin 1beta (IL-1beta), and major histocompatibility complex class II molecules, all of which influence antigen processing and presentation. Nramp1 also has a direct effect on antigen processing, possibly by regulating the activity of proteases in the late endosomal compartment. Hence, there are multiple ways (regulation of bacterial load or recombinant antigen dose, class II molecule expression, costimulatory or adjuvant activity, and antigen processing) that Nramp1 might influence responses to recombinant salmonella vaccines. To test the hypothesis that Nramp1 influences responses to vaccination, congenic mouse strains have been used to analyze immune responses to recombinant antigens (tetanus toxoid antigen and leishmanial gp63) carried by live attenuated S. typhimurium aroA aroD mutants. Results show that congenic mice carrying the wild-type (S. typhimurium resistance) Nramp1 allele mount a predominantly T-helper-1 (IL-2 and gamma interferon) response to vaccination and show enhanced resolution of lesions following challenge infection with Leishmania major. In contrast, mice carrying mutant (S. typhimurium susceptibility) Nramp1 mount a T-helper-2 (immunoglobulin E and IL-4) response and show exacerbated lesion growth upon challenge.

Genetics of host resistance and susceptibility to intramacrophage pathogens: a study of multicase families of tuberculosis, leprosy and leishmaniasis in north-eastern Brazil

Genetic analysis of disease phenotypes segregating in recombinant inbred, congenic and recombinant haplotype mouse strains permitted us to effectively "scan" the murine genome for genes controlling resistance and susceptibility to leishmanial infections. Five major regions were implicated which, because they show conserved synteny with regions of the human genome, immediately provide candidate gene regions for human disease susceptibility genes. A common intramacrophage niche for leishmanial and mycobacterial pathogens, and a similar spectrum of immune response and disease phenotypes, also led to the prediction that the same genes/candidate gene regions might be responsible for genetic susceptibility to mycobacterial infections such as leprosy and tuberculosis. Indeed, one of the murine genes (Nramp1) was identified for its role in controlling a range of intramacrophage pathogens, including leishmanial, salmonella and mycobacterial infections. In recent studies, multicase families of visceral leishmaniasis, tuberculosis and leprosy, from north-eastern Brazil have been analysed to determine the role of these candidate genes/regions in humans. Complex segregation analysis provides evidence for one or two major genes controlling susceptibility to these diseases in this population. Family-based linkage analyses (e.g., combined segregation and linkage analysis; sib-pair analyses) and transmission disequilibrium testing have been used to examine the role of four regions in disease susceptibility and/or immune response phenotypes. Results to date demonstrate: (1) the major histocompatibility complex (MHC:H-2 in mouse, HLA in humans: mouse chromosome 17/human 6p; candidates class II and class III including tumour necrosis factor alpha/beta genes) shows both linkage to, and allelic association with, leprosy per se, but is only weakly associated with visceral leishmaniasis and shows neither linkage to, nor allelic association with, tuberculosis; (2) no evidence for linkage between NRAMP1, the positionally cloned candidate for the murine macrophage resistance gene Ity/Lsh/Bcg (mouse chromosome 1/human 2q35), and susceptibility to tuberculosis or visceral leishmaniasis; (3) the region of human chromosome 17q (candidates NOS2A, SCYA2-5) homologous with distal mouse chromosome 11 is linked to tuberculosis susceptibility; and (4) the "T helper 2" cytokine gene cluster (proximal murine chromosome 11/human 5p; candidates IL4, IL5, IL9, IRF1, CD14) is not linked to human disease susceptibility for any of the three infections, but shows linkage to and highly significant allelic association with ability to mount an immune response to mycobacterial antigens. The demonstration of an allelic association between IL4 and immune response to mycobacterial antigen may provide a genetic explanation for the inverse association recently demonstrated between delayed hypersensitivity T helper 1 responses to mycobacterial antigen and atopic disorder in Japanese children. These studies demonstrate that the "mouse-to-human" strategy, refined by our knowledge of the human immune response to infection, can lead to the identification of important candidate gene regions in humans.

T cell responses to crude and defined leishmanial antigens in patients from the lower Amazon region of Brazil infected with different species of Leishmania of the subgenera Leishmania and Viannia

Amazonian localized cutaneous leishmaniasis (LCL) is caused by parasites of the subgenera Leishmania and Viannia. Respectively, these parasites may cause diffuse cutaneous leishmaniasis (DCL) and mucocutaneous leishmaniasis (MCL). This, together with differing skin test responses, suggests some species-specificity in cell mediated immunity. In this study, T cell responses (proliferative and interferon-gamma) to crude and defined antigens were examined in paired samples pre and post chemotherapy. Untreated L. (L.) amazonensis LCL patients showed lower responses to crude leishmanial antigens than the L. (V.) spp. group. L. (V.) braziliensis antigen was a more potent stimulator of T cell responses than L. (L.) amazonensis antigen in all patient groups. Few positive responses were seen to the L. (L.) amazonensis glycoprotein GP46. A substantial proportion of LCL patients did respond to the L. (L.) pifanoi amastigote antigens A2, and the surface membrane glycoprotein P8. DCL patients were poor responders to all leishmanial antigens, except GP46. In contrast, MCL patients were good responders to all antigens except GP46 and A2. A significant rise in the response to P8 and A2 antigen was seen post treatment across all LCL and MCL patients, indicating that these antigens might provide suitable vaccine candidates.

Immunogenetics of leishmanial and mycobacterial infections: the Belem Family Study

In the 1970s and 1980s, analysis of recombinant inbred, congenic and recombinant haplotype mouse strains permitted us to effectively 'scan' the murine genome for genes controlling resistance and susceptibility to leishmanial infections. Five major regions of the genome were implicated in the control of infections caused by different Leishmania species which, because they show conserved synteny with regions of the human genome, immediately provides candidate gene regions for human disease susceptibility genes. A common intramacrophage niche for leishmanial and mycobacterial pathogens, and a similar spectrum of immune response and disease phenotypes, also led to the prediction that the same genes/candidate gene regions might be responsible for genetic susceptibility to mycobacterial infections such as leprosy and tuberculosis. Indeed, one of the murine genes (Nramp1) was identified for its role in controlling a range of intramacrophage pathogens including leishmania, salmonella and mycobacterium infections. In recent studies, multicase family data on visceral leishmaniasis and the mycobacterial diseases, tuberculosis and leprosy, have been collected from north-eastern Brazil and analysed to determine the role of these candidate genes/regions in determining disease susceptibility. Complex segregation analysis provides evidence for one or two major genes controlling susceptibility to tuberculosis in this population. Family-based linkage analyses (combined segregation and linkage analysis; sib-pair analysis), which have the power to detect linkage between marker loci in candidate gene regions and the putative disease susceptibility genes over 10-20 centimorgans, and transmission disequilibrium testing, which detects allelic associations over 1 centimorgan (ca. 1 megabase), have been used to examine the role of four regions in determining disease susceptibility and/or immune response phenotype. Our results demonstrate: (i) the major histocompatibility complex (MHC: H-2 in mouse, HLA in man: mouse chromosome 17/human 6p; candidates class II and class III including TNF alpha/beta genes) shows both linkage to, and allelic association with, leprosy per se, but is only weakly associated with visceral leishmaniasis and shows neither linkage to nor allelic association with tuberculosis; (ii) no evidence for linkage between NRAMP1, the positionally cloned candidate for the murine macrophage resistance gene Ity/Lsh/Bcg (mouse chromosome 1/human 2q35), and susceptibility to tuberculosis or visceral leishmaniasis could be demonstrated in this Brazilian population; (iii) the region of human chromosome 17q (candidates NOS2A, SCYA2-5) homologous with distal mouse chromosome 11, originally identified as carrying the Scl1 gene controlling healing versus nonhealing responses to Leishmania major, is linked to tuberculosis susceptibility; and (iv) the 'T helper 2' cytokine gene cluster (proximal murine chromosome 11/human 5q; candidates IL4, IL5, IL9, IRF1, CD14) controlling later phases of murine L. major infection, is not linked to human disease susceptibility for any of the three infections, but shows linkage to and highly significant allelic association with ability to mount an immune response to mycobacterial antigens. These studies demonstrate that the 'mouse-to-man' strategy, refined by our knowledge of the human immune response to infection, can lead to the identification of important candidate gene regions in man.

Nramp1 locus encodes a 65 kDa interferon-gamma-inducible protein in murine macrophages

The murine Nramp1 (natural-resistance-associated macrophage protein) locus, formerly known as Ity/Lsh/Bcg, was isolated previously on the basis of chromosomal location, and as conferring natural resistance to infection against intracellular macrophage pathogens. The gene encodes a transporter molecule of unknown function. We have prepared polyclonal antisera against the C-terminal 35 amino acids of murine Nramp1. This serum is reactive towards a 65 kDa protein, expressed in murine macrophage cells from resistant or susceptible mice stimulated with interferon-gamma and lipopolysaccharide, but not in non-macrophage cells. Evidence indicates that Nramp1 is localized in a subcellular membrane rather than at the cell surface. This evidence includes: the identification of conserved endocytic targeting motifs following inspection of human and murine Nramp sequences; the enrichment of Nramp1, following magnetic selection of phagolysosomal vesicles from activated macrophages that were allowed to phagocytose magnetic, IgG-coated beads; confocal microscopy. These studies place Nramp1 on a membrane in close proximity to obligate intracellular pathogens. A link between Nramp1 and divalent-cation transport is suggested by sequence similarity with yeast SMF1. Evidence showing modulation of Nramp1 protein levels by iron chelation provides a direct link with Nramp1 function and divalent-cation metabolism.

Parasite genome analysis. Progress in the Leishmania genome project

Genome projects have been established for 7 major groups of human parasitic infections: malaria, leishmaniasis, African trypanosomiasis, American trypanosomiasis, toxoplasmosis, schistosomiasis and filariasis. All except malaria and toxoplasmosis have come under the umbrella of the World Health Organization's Strategic Committee on Parasite Genome Analysis. The focus of this meeting of the Society was to review progress made in the Leishmania and African trypanosome genome projects. This paper introduces the genome projects and reviews briefly progress in pulsed-field gel karyotype mapping and gene identification via expressed sequence tag sequencing for the leishmaniasis genome project. The overall aim of the genome projects is to harness the latest developments in molecular genetic technology and sequence analysis for the rapid-generation of new data which may, in turn, revolutionize our approaches to the study of the biology of these organisms.

Nramp1 transfection transfers Ity/Lsh/Bcg-related pleiotropic effects on macrophage activation: influence on antigen processing and presentation

The natural resistance-associated macrophage protein (Nramp1) regulates macrophage activation. One of its pleiotropic effects on macrophage function is to regulate expression of major histocompatibility class II molecules. In this study macrophages stably transfected with the wild-type (infection-resistant) or the natural mutant (infection-susceptible) allele of the Nramp1 gene were used to study class II expression and processing and presentation of recombinant protein antigens to CD4+ T-cell hybridomas. As demonstrated previously for macrophages from Nramp1-resistant and -susceptible congenic mouse strains, transfected macrophage clones carrying the wild-type allele showed enhanced upregulation of class II molecules in response to gamma interferon compared to that shown by macrophage clones carrying an endogenous mutant allele or transfected with the mutant allele expressed under a viral long terminal repeat promoter. The wild-type allele-transfected macrophage clones also demonstrated an enhanced, lipopolysaccharide-dependent ability to process the recombinant leishmanial antigen LACK-delta 1 (the Leishmania homolog of receptors for activated C kinase) for presentation to LACK-specific CD4+ T cells. An influence on antigen processing must therefore be added to the growing list of pleiotropic effects of the Nramp1 gene potentially contributing to its role in infectious and autoimmune disease susceptibility. These results also have important implications for analysis of T-cell responses to vaccination, especially where antigens are presented to the immune system using live Salmonella species or Mycobacterium bovis BCG as a vaccine vehicle.

Analysis of the candidate gene NRAMP1 in the first 61 ARC National Repository families for rheumatoid arthritis

Maximum likelihood identity-by-descent (IBD) sib pair analysis using a 3 locus haplotype NRAMP1-IL8RB-VIL1, or NRAMP1 alone, provided preliminary evidence (maximum LOD score = 1.01, p = 0.024) for a gene in this region of human chromosome 2q35 contributing to susceptibility to rheumatoid arthritis (RA). Candidacy for NRAMP1 as the disease susceptibility gene was supported by a significant bias (p < 0.048) toward transmission of the NRAMP1 promoter region allele 3 in affected offspring.

Unravelling the Leishmania genome

The past few years have been significant advances in our understanding of eukaryotic genomes. In the field of parasitology, this is best exemplified by the application of genome mapping techniques to the study of genome structure and function in the protozoan parasite, Leishmania. Although much is known about the organism and the diseases it causes, molecular genetics has only recently begun to play a major part in elucidating some of the unusual characteristics of this interesting parasite. Mapping of the small (35 Mb) genome and determination of the functional role of genes by the application of in vitro homologous gene targeting techniques are revealing novel avenues for the development of prophylactic measures.

Linkage of rheumatoid arthritis to the candidate gene NRAMP1 on 2q35

The macrophage resistance gene NRAMP1 regulates priming/activation of macrophages for enhanced TNF alpha, IL 1 beta, and MHC class II expression. Since all of these functions are of potential importance in the induction or maintenance or both of autoimmune disease, samples from the Arthritis and Rheumatism Council's repository of multicase rheumatoid arthritis families were typed for a dinucleotide repeat in the NRAMP1 promoter region and four other 2q34 (TNP1) or 2q35 (IL8R, VIL1, DES) marker genes. Identity by descent (IBD) sib pair analysis using a three locus haplotype NRAMP1-IL8RB-VIL1, or NRAMP1 alone, provided preliminary evidence (maximum lod score = 1.01, p = 0.024) for a gene in this region contributing to suceptibility to rheumatoid arthritis. Candidacy for NRAMP1 as the disease susceptibility gene was supported by a significant bias (p = 0.048) towards transmission of the NRAMP1 promoter region allele 3 in affected offspring.

Structure and function of the natural-resistance-associated macrophage protein (Nramp1), a candidate protein for infectious and autoimmune disease susceptibility

The ability of macrophages to become activated is central to antimicrobial immunity. Microbial stimuli can elicit a cascade of gene-inductive events mediating inflammation, elimination of the invading organism and induction of T-cell memory against reinvasion. Nramp1, a gene originally identified as Ity/Lsh/Bcg for its role in controlling Salmonella typhimurium, Leishmania donovani and Mycobacterium bovis infections in mice, regulates this cascade. Here we examine how the structure of the Nramp1 protein might relate to its function, and how variable expression of the human homologue (NRAMP1) might mediate enhanced resistance to infection but cause susceptibility to autoimmune disease.

Toxoplasma gondii expressed sequence tags: insight into tachyzoite gene expression

Analysis of DNA sequences from the 5' end of 239 directionally cloned Toxoplasma gondii RH strain tachyzoite-derived cDNAs revealed significant similarity to several classes of genes/proteins including 24 ribosomal proteins, five metabolic enzymes, four cell-cycle regulators and 15 previously cloned T. gondii genes. The remaining sequences with no significant match include several which were recovered more than once. The variety and redundancy of expressed sequence tags (ESTs GenBank accession numbers T62239-T62475) in this sample suggest that the tachyzoite cDNA library reflects tachyzoite gene expression. A large scale EST effort should uncover many new genes and provide a wealth of information about genes involved with the growth and proliferation of tachyzoites.

Polymorphism in tumor necrosis factor genes associated with mucocutaneous leishmaniasis

Recent studies have shown that mucocutaneous leishmaniasis (MCL), a severe and debilitating form of American cutaneous leishmaniasis (ACL) caused by Leishmania braziliensis infection, is accompanied by high circulating levels of tumor necrosis factor (TNF)-alpha. Analysis of TNF polymorphisms in Venezuelan ACL patients and endemic unaffected controls demonstrates a high relative risk (RR) of 7.5 (P < 0.001) of MCL disease in homozygotes for allele 2 of a polymorphism in intron 2 of the TNF-beta gene, especially in females (RR = 9.5; P < 0.001) compared with males (RR = 4; P < 0.05). A significantly higher frequency (P < 0.05) of allele 2 at the -308-basepair TNF-alpha gene polymorphism was also observed in MCL patients (0.18) compared with endemic control subjects (0.069), again associated with a high relative risk of disease (RR = 3.5; P < 0.05) even in the heterozygous condition. Because both the TNF-alpha and TNF-beta polymorphisms have previously been linked with functional differences in TNF-alpha levels, these data suggest that susceptibility to the mucocutaneous form of disease may be directly associated with regulatory polymorphisms affecting TNF-alpha production.

Extensive polymorphism at the Gp63 locus in field isolates of Leishmania peruviana

Genetic diversity within and between tandemly arrayed copies of the Gp63 gene occurs in laboratory isolates of Leishmania spp., but the extent to which this represents natural genetic diversity has not been assessed. Here, the Gp63 locus is examined in 58 fresh isolates of L. peruviana, and clones derived from them, collected throughout the Peruvian Andes. Extensive polymorphism is observed, both in size of Gp63 containing chromosomes, and for restriction-fragment-length polymorphisms (RFLPs) at the Gp63 locus. All clones within an isolate are identical, including those with two distinct Gp63-hybridising chromosomal-sized pulsed-field gel electrophoresis (PFGE) bands, consistent with diploidy but with size differences in homologous chromosomes. For RFLP analysis, three enzymes were selected to cut within the coding region (PstI), in the intergenic region (SalI) and outside (EcoRI) the Gp63 gene cluster. PstI gave identical banding patterns across all isolates/clones. For EcoRI and SalI, all clones within an isolate were identical, but isolates were polymorphic for fragments at 13 (2-30 kb) and 8 (2.6-8.8 kb) different molecular mass locations generating 19 and 16 distinct RFLP patterns or genotypes for each enzyme, respectively. EcoRI restriction patterns, analysed by PFGE, were consistent with the presence of two clusters of Gp63 genes on each homologous chromosome, one contained within EcoRI fragments large enough to carry from 3 to 10 copies of the Gp63 gene, the second on fragments which could carry 1 or 2 copies of the gene. SalI patterns indicated variable restriction sites within clusters, but not within every intergenic region. A hierarchical analysis of variance of allele frequencies, expressed in terms of Wright's F-statistic, indicated significant barriers to gene flow at all levels, valleys within regions (north/south), villages within valleys, and individuals within villages. This extreme polymorphism at the Gp63 locus of L. peruviana demonstrates the great potential for generation of genetic diversity in parasite populations.

Opposing effects of interferon-gamma on iNOS and interleukin-10 expression in lipopolysaccharide- and mycobacterial lipoarabinomannan-stimulated macrophages

Previous studies have demonstrated that, like bacterial lipopolysaccharide (LPS), arabinofuranosyl-terminated lipoarabinomannan (AraLAM) from an attenuated strain of Mycobacterium induces potent early gene (c-fos, KC, JE and TNF-alpha) responses in murine macrophages, whereas extensively alpha-Manp capped LAM (ManLAM) from virulent M. tuberculosis do not. In this study we have extended analysis of the influence of mycobacterial LAM on macrophage function by demonstrating that AraLAM (but not ManLAM), like bacterial LPS, is a potent stimulator of inducible nitric oxide synthase (iNOS) expression independent of the autocrine activity of co-stimulated tumour necrosis factor-alpha (TNF-alpha) release. The inability of ManLAM to induce iNOS expression was not due to induction of the 'deactivating' cytokine interleukin-10 (IL-10). Indeed, like LPS, AraLAM was also a potent inducer of IL-10 expression. However, analysis of AraLAM- or LPS-induced responses in the presence of interferon-gamma (IFN-gamma) showed that, whereas IFN-gamma acts as a potent co-stimulus for iNOS, it completely inhibits the IL-10 response. Hence, the presence of IFN-gamma early in infection will have an important immunomodulatory role in determining the macrophage response. These results have important implications for the pathogenesis of virulent and avirulent mycobacteria in vivo.

Nramp transfection transfers Ity/Lsh/Bcg-related pleiotropic effects on macrophage activation: influence on oxidative burst and nitric oxide pathways

BACKGROUND

The Ity/Lsh/Bcg gene on mouse chromosome 1 regulates priming/activation of macrophages for antimicrobial and tumouricidal activity. A candidate gene expressed in macrophages has been identified by positional cloning and full-length sequence analysis, and encodes the Natural resistance-associated macrophage protein (Nramp). In this study, we have tested the hypothesis that the Nramp gene corresponds to Ity/Lsh/Bcg.

MATERIALS AND METHODS

In vitro transfection was used to introduce the resistant allele into the macrophage cell line RAW 264.7 derived from the recessive susceptible BALB/c mouse strain. Expression of the transgene was monitored on the background of the endogenous susceptible allele by allele-specific oligonucleotide hybridization.

RESULTS

Expression of the transgene correlated with three Lshr-associated lipopolysaccharide/interferon-gamma-regulated macrophage activation phenotypes: respiratory burst, nitrite release, and uptake of L-arginine. Endogenous and stimulated L-arginine fluxes were inhibitable with the radical scavengers nordihydroguaiaretic acid and butylated hydroxyanisole. The mitochondrial electron transport inhibitors, rotenone and thenoyltrifluoroacetone, inhibited respiratory burst, and rotenone suppressed L-arginine flux, implying that mitochondrial-derived oxygen radicals are important mediators in Nramp-regulated signal transduction pathways.

CONCLUSIONS

These data provide the first direct evidence that Nramp is the product of the Ity/Lsh/Bcg gene, and are consistent with the hypothesis that the many pleiotropic effects of this gene on macrophage activation may all derive from the requirement for mitochondrial generation of oxygen radicals for intracellular signaling.

Genomic organization and sequence of the human NRAMP gene: identification and mapping of a promoter region polymorphism

BACKGROUND

Murine Nramp is a candidate for the macrophage resistance gene Ity/Lsh/Bcg. Sequence analysis of human NRAMP was undertaken to determine its role in man.

MATERIALS AND METHODS

A yeast artificial chromosome carrying NRAMP was subcloned and positive clones sequenced. The transcriptional start site was mapped using 5' RACE PCR. Polymorphic variants were amplified by PCR. Linkage analysis was used to map NRAMP.

RESULTS

NRAMP spans 12kb and has 15 exons encoding a 550 amino acid protein showing 85% identity (92% similarity) with Nramp. Two conserved PKC sites occur in exon 2 encoding the Pro/Ser rich SH3 binding domain, and in exon 3. Striking sequence similarities (57 and 53%) were observed with yeast mitochondrial proteins, SMF1 and SMF2, especially within putative functional domains: exon 6 encoding the second transmembrane spanning domain, site of the murine susceptibility mutation; and exon 11 encoding a conserved transport motif. No mutations comparable to the murine susceptibility mutation were found. The transcriptional initiation site mapped 148 bp 5' of the translational initiation codon. 440bp of 5' flanking sequence contained putative promoter region elements: 6 interferon-gamma response elements, 3 W-elements, 3 NF kappa B binding sites and 1 AP-1 site. Nine purine-rich GGAA core motifs for the myeloid-specific PU.1 transcription factor were identified, two combining with imperfect AP1-like sites to create PEA3 motifs. TATA, GC and CCAAT boxes were absent. A possible enhancer element containing the Z-DNA forming dinucleotide repeat t(gt),ac(gt),ac(gt),g was polymorphic (4 alleles; n = 4,9,10,11), and was used to map NRAMP to 2q35.

CONCLUSIONS

This analysis provides important resources to study the role of NRAMP in human disease.

Genetic regulation of leishmanial and mycobacterial infections: the Lsh/Ity/Bcg gene story continues

A common basis to genetic regulation of leishmanial and mycobacterial infections is provided by the action of the murine Lsh/Ity/Bcg gene in controlling the priming/activation of macrophages for antimicrobial activity. This relies on the TNF-alpha-dependent sustained expression of the inducible nitric oxide synthase (iNOS) gene responsible for the generation of large amounts of toxic nitric oxide (NO). The Lsh/Ity/Bcg gene has many pleiotropic effects, including differential expression of the early response gene KC following stimulation of macrophages with bacterial lipopolysaccharide (LPS) and mycobacterial lipoarabinomannan (LAM). The major signal transduction pathway involved in KC induction requires the generation of low levels of NO via constitutive nitric oxide synthase (cNOS) activity, leading to activation of guanylate cyclase and the cGMP-dependent kinase pathway. NO therefore appears to provide a common link between the early influence of Lsh in regulating the expression of genes which mediate many pleiotropic effects, and the later production of NO as the final effector mechanism for kill. The recently cloned candidate for Lsh/Ity/Bcg, designated Nramp for Natural resistance associated macrophage protein, encodes a polytopic integral membrane protein that has structural features common to prokaryotic and eukaryotic transporters and includes a conserved binding-protein-dependent transport motif which may be involved in interaction with peripheral ATP-binding subunits. The N-terminal sequence also carries a proline/serine rich putative SH3 binding domain, consistent with a role for tyrosine kinases in regulating Nramp function. (ABSTRACT TRUNCATED AT 250 WORDS)

Genetic and physical mapping of 2q35 in the region of the NRAMP and IL8R genes: identification of a polymorphic repeat in exon 2 of NRAMP

Recent interest has focused on the region of conserved synteny between mouse chromosome 1 and human 2q33-q37, particularly over the region encoding the murine macrophage resistance gene Ity/Lsh/Bcg (candidate Nramp) and members of the Il8r interleukin-8 (IL8) receptor gene cluster. In this paper, identification of a restriction fragment length polymorphism in the IL8RB gene in 35 pedigrees previously typed for markers in the 2q33-q37 interval provided evidence (lod scores > 3) for linkage between IL8RB and the 2q34-q35 markers FN1, TNP1, VIL1, and DES. Physical mapping, using yeast artificial chromosomes isolated with VIL1, confirmed that IL8RA, IL8RB, and the IL8RB pseudogene map within the NRAMP-VIL1 interval, with the physical distance (155 kb) from 5' LSH to 3' VIL1 representing approximately 3-fold that observed in the mouse. Partial sequencing of NRAMP confirmed the presence of the N-terminal proline/serine-rich putative SH3 binding domain in exon 2 of the human gene. Further analysis of Brazilian leprosy and visceral leishmaniasis pedigrees identified a rare second allele varying in a 9-nucleotide repeat motif of the exon 2 sequence but segregating independently of the disease phenotype.

Immune response in healthy volunteers vaccinated with BCG plus killed leishmanial promastigotes: antibody responses to mycobacterial and leishmanial antigens

Antibody (IgG) responses to mycobacterial (BCG; PPD; Mycobacterium leprae soluble antigen, MLSA) and leishmanial (Leishmania mexicana LV4) antigens were measured in 208 initially PPD and leishmanin skin-test negative volunteers divided into four vaccine groups as follows: 68 received BCG plus killed promastigotes (group A), 47 received BCG alone (group B), 47 received killed promastigotes alone (group C), and 46 formed the diluent control (placebo, group D). Three vaccine doses were administered at 8-12 week intervals. Vaccinees were bled immediately prior to each vaccination, and again at 3- and 12-month follow-up. Skin tests were performed prevaccination, and again at the 3- and 12-month follow-up. Anti-BCG, anti-PPD and anti-MLSA IgG levels increased significantly in groups A and B receiving BCG. The presence of leishmanial antigen (with BCG) in the inoculum suppressed the IgG response to Mycobacterium tuberculosis/Mycobacterium bovis-related (PPD and BCG), but not M. leprae-related (MLSA)-related, antigens. A small but significant increase (relative to prevaccination level) in response to MLSA, but not to BCG or PPD was observed in the non-BCG-vaccinated groups. The background level of response to mycobacterial and leishmanial antigens was higher in the Venezuelan vaccinees than in non-endemic (British) volunteers. Responses to leishmanial antigen were not enhanced in the two vaccine groups receiving killed promastigotes (with/without BCG) compared with the BCG alone and placebo groups. Instead, all vaccine groups showed a pattern of response consistent with either (i) a response to the skin-test antigen or, more likely, (ii) seasonal endemic exposure to leishmanial antigen. Interestingly, this endemic response to leishmanial antigen was enhanced in the vaccine groups receiving BCG, despite the fact that group B received no leishmanial antigen in the vaccine inoculum. When prevaccination IgG levels (mean + 3 standard deviations) were used to determine a negative cut-off, a low percentage (< 38%) of vaccinees converted to responder status for either anti-mycobacterial or anti-leishmanial responses, and those who did would be classified as 'low-responder' status compared with titres observed in severe forms of disease. Hence, although there was evidence for a background endemic response to both leishmanial and mycobacterial antigens, there was no evidence that vaccination per se led to a potentially disease exacerbatory level of TH2-associated antibody response especially with respect to the anti-leishmanial response.(ABSTRACT TRUNCATED AT 400 WORDS)

Selective disruption of hypermnesia for pictures and words

In this study, we investigated the effects of various interpolated tasks on hypermnesia (improved recall across repeated tests) for pictures and words. In five experiments, subjects studied either pictures or words and then completed two free-recall tests, with varying activities interpolated between the tests. The tasks performed between tests were varied to test several hypotheses concerning the possible factor(s) responsible for disruption of the hypermnesic effect. In each experiment, hypermnesia was obtained in a control condition in which there was no interpolated task between tests. The remaining conditions showed that the effect of the interpolated tasks was related to the overlap of the cognitive processes involved in encoding the target items and performing the interpolated tasks. When pictures were used as the target items, no hypermnesia was obtained when subjects engaged in imaginal processing interpolated tasks, even when these tasks involved materials that were very distinct from the target items. When words were used as the target items, no hypermnesia was obtained when the interpolated tasks required verbal/linguistic processing, even when the items used in these tasks were auditorily presented. The results are discussed in terms of a strength-based model of associative memory.

Influence of macrophage resistance gene Lsh/Ity/Bcg (candidate Nramp) on Toxoplasma gondii infection in mice

Functional studies have shown that the murine macrophage resistance gene Lsh/Ity/Bcg (candidate Nramp) regulates macrophage priming/activation for antimicrobial activity via the tumour necrosis factor-alpha (TNF-alpha)-dependent production of reactive nitrogen intermediates. Since Toxoplasma gondii also parasitizes macrophages, is a stimulator of endogenous TNF-alpha release, and is sensitive to nitric oxide-mediated killing in activated macrophages, studies were carried out using chromosome 1 congenic mouse strains to determine whether Lsh influences T. gondii infection. Two interesting observations were made: (i) contrary to expectation, mice carrying the Lsh-resistant allele died earlier over the acute phase of infection than Lsh-susceptible mice; and (ii) Lsh-resistant mice which survived this acute phase of infection showed lower brain cyst numbers than the Lsh-susceptible mice. Whilst the latter occurred independently of route of inoculation (oral, intraperitoneal, or subcutaneous), the former was influenced both by the route of inoculation and the genetic background on which the Lsh-resistant allele had been isolated. Hence, following oral administration of 20 brain cysts of the RRA strain of T. gondii, mice carrying the Lsh-resistant allele on a B10 genetic background showed a significantly enhanced rate of mortality over the acute (first 8-12 days) phase of infection than B10 Lsh-susceptible mice. Although this acute phase of infection in B10 background mice was accompanied by an increase in serum TNF-alpha levels in both Lsh-resistant and -susceptible mouse strains, early mortality preceded the TNF-alpha peak, and administration of neutralizing rabbit anti-TNF-alpha did not significantly enhance survival. Hence, inflammatory mediators other than TNF-alpha appear to be responsible for the increased rate of acute mortality observed in resistant mice. Infection intraperitoneally led to delayed mortality in B10 mice, with the mean time to 50% mortality now being significantly longer in Lsh-resistant than in Lsh-susceptible mice. On a BALB genetic background, it was the i.p. route of infection which led to acute mortality and more rapid death in the Lsh-resistant strain. When a less virulent inoculum was used and mortality delayed, Lsh-susceptible mice died more rapidly, and i.p. administration of rabbit anti-TNF-alpha led to 100% mortality between days 8 and 10 of infection in both susceptible and resistant mouse strains, consistent with a crucial protective role for TNF-alpha during this phase of infection.(ABSTRACT TRUNCATED AT 400 WORDS)

NH2-terminal sequence of macrophage-expressed natural resistance-associated macrophage protein (Nramp) encodes a proline/serine-rich putative Src homology 3-binding domain

The Lsh/Ity/Bcg locus on mouse chromosome 1 regulates macrophage (m phi) priming/activation for antimicrobial activity against intracellular pathogens. A candidate Bcg gene, designated natural resistance-associated m phi protein (Nramp), recently isolated from a pre-B cell cDNA library encodes a polytopic integral membrane protein with structural features common to prokaryotic and eukaryotic transporters. In the present study, an activated m phi cDNA library yielded new Nramp clones that differ in the 5' region from the published pre-B cell-derived clone sequence, resulting in addition of 64 amino acids at the NH2 terminus of the predicted protein. This new domain is rich in proline, serine, and basic amino acids, and includes three protein kinase C phosphorylation sites and a putative Src homology 3 binding domain. RNAs containing this domain are the only form found in the m phi. Hence, the protein encoded by this RNA is the candidate molecule mediating natural resistance to intra-m phi pathogens.

Interaction with extracellular matrix proteins influences Lsh/Ity/Bcg (candidate Nramp) gene regulation of macrophage priming/activation for tumour necrosis factor-alpha and nitrite release

The murine resistance gene Lsh/Ity/Bcg regulates activation of macrophages for tumour necrosis factor-alpha (TNF-alpha)-dependent production of nitric oxide mediating antimicrobial activity against Leishmania, Salmonella and Mycobacterium. As Lsh is differentially expressed in macrophages from different tissue sites, experiments were performed to determine whether interaction with extracellular matrix (ECM) proteins would influence the macrophage TNF-alpha response. Plating of bone marrow-derived macrophages onto purified fibrinogen or fibronectin-rich L929 cell-derived matrices, but not onto mannan, was itself sufficient to stimulate TNF-alpha release, with significantly higher levels released from congenic B10.L-Lshr compared to C57BL/10ScSn (Lshs) macrophages. Only macrophages plated onto fibrinogen also released measurable levels of nitrites, again higher in Lshr compared to Lshs macrophages. Addition of interferon-gamma (IFN-gamma), but not bacterial lipopolysaccharide or mycobacterial lipoarabinomannan, as a second signal enhanced the TNF-alpha and nitrite responses of macrophages plated onto fibrinogen, particularly in the Lshr macrophages. Interaction with fibrinogen and fibronectin also primed macrophages for an enhanced TNF-alpha response to leishmanial parasites, but this was only translated into enhanced nitrite responses in the presence of IFN-gamma. In these experiments, Lshr macrophages remained superior in their TNF-alpha responses throughout, but to a degree which reflected the magnitude of the difference observed on ECM alone. Hence, the specificity for the enhanced TNF-alpha responses of Lshr macrophages lay in their interaction with fibrinogen and fibronectin ECM, while a differential nitrite response was only observed with fibrinogen and/or IFN-gamma. The results are discussed in relation to the possible function of the recently cloned candidate gene Nramp, which has structural identity to eukaryote transporters and an N-terminal cytoplasmic proline/serine-rich putative SH3 binding domain.

Induction of early-response genes KC and JE by mycobacterial lipoarabinomannans: regulation of KC expression in murine macrophages by Lsh/Ity/Bcg (candidate Nramp)

The murine chromosome 1 gene Lsh/Ity/Bcg (candidate Nramp) regulates macrophage activation for antimicrobial activity against Salmonella typhimurium, Leishmania donovani, and Mycobacterium spp. To determine early events in the activation pathway, the ability of mycobacterial lipoarabinomannan (LAM) to induce early gene (KC and JE) expression in macrophages from susceptible (S) C57BL/10ScSn (Lshs) and congenic resistant (R) B10.L-Lshr mice was investigated. Stimulation with 1.8 microgram of arabinofuranosyl-terminated LAM (AraLAM) per ml resulted in similar kinetics for KC or JE expression in S and R macrophages. However, whereas JE/glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA ratios remained equivalent, R macrophages consistently showed enhanced KC/GAPDH ratios within 30 to 40 min of stimulation compared with S macrophages. Significant differences in KC/GAPDH ratios were observed throughout the peak period (0.5 to 6 h) of the KC response and with doses of AraLAM ranging from 0.01 to 2.5 micrograms/ml. Heavily mannosylated LAM from virulent Mycobacterium tuberculosis Erdman, in doses of up to 2.5 micrograms/ml, failed to stimulate KC or JE in S or R macrophages. Gamma interferon alone (25 U/ml) stimulated equivalent JE expression in S and R macrophages and synergized with AraLAM to enhance JE in both. In contrast, AraLAM-induced KC expression was inhibited in the presence of gamma interferon. Agonist/inhibitor studies were undertaken to determine the signal transduction pathways mediating KC expression. The protein kinase C (PKC) inhibitor Calphostin C (200 nM) inhibited AraLAM-induced KC by 34% +/- 4% in S macrophages and 43% +/- 5% in R macrophages; the cyclic AMP-dependent PKA inhibitor KT5720 (2 microM) inhibited AraLAM-induced KC by 33% +/- 4% (S) and 25% +/- 5% (R). A role for Ca2+ was indicated because ionophore alone stimulated KC expression and synergized with AraLAM to give a dramatically enhanced response. Induction of KC was also inhibited by (i) blocking constitutive nitric oxide (NO) production by preincubation of macrophages with NG-monomethyl-L-arginine (400 microM) (48% +/- 8% [S] and 40% +/- 11% [R]) and (ii) incubation of macrophages with the cyclic GMP-dependent kinase inhibitor KT5823 (4 microM) (65% +/- 4% [S] and 72% +/- 6% [R]). The manner in which these PKC-, PKA-, and Ca(2+)-dependent, NO-mediated cyclic GMP-dependent kinase signal transduction pathways may relate to function of the candidate Lsh/Ity/Bcg gene Nramp is discussed.

Mapping of genes controlling Leishmania major infection in CXS recombinant inbred mice

Previous studies demonstrated that growth of the primary lesion following Leishmania major infection in inbred mice comes under the control of a single major gene designated Scl-1. Preliminary mapping studies had suggested a chromosome 8 location for the gene. In this paper a more detailed study of different disease phenotypes (lesion growth, splenomegaly, liver parasite load) in 14 CXS recombinant inbred (RI) mouse strains was undertaken in order to obtain a more definitive map location for the gene. Using the Kruskal-Wallis generalization of the Wilcoxon Rank-Sum Test to assign RI strains to parental phenotypes, high concordances with genes at the mid (Il-3) to distal end (Dlb-1, Hox-2, Sigje, Mtv-3 and Es-3) of chromosome 11 were demonstrated with two strains (LV39 and NIH173) of L. major given as promastigotes subcutaneously into the shaven rump. The results suggest that the most likely location for the previously described single major gene (Scl-1) regulating early lesion expansion is at the distal end of mouse chromosome 11, with the possibility that a gene located more proximally influences later phases of the infection.

Influence of genes within the MHC on mortality and brain cyst development in mice infected with Toxoplasma gondii: kinetics of immune regulation in BALB H-2 congenic mice

Previous work has shown that genes within the major histocompatibility complex (MHC) of the mouse influence resistance and susceptibility to Toxoplasma gondii infection. Initial studies presented here using B10 H-2 congenic and recombinant haplotype mice inoculated via the oral route with the low virulence Beverley strain of T. gondii confirm the D region localization of MHC-linked control of brain cyst number. All B10 mice were, however, exquisitely sensitive to minor changes in virulence of the parasite inoculum resulting in high mortality during the early acute phase of infection. Further experiments examining mortality and brain cyst number in BALB MHC congenic mice inoculated via different routes indicated that the BALB background would provide a more favourable genetic environment in which to analyse kinetics of MHC controlled immune regulation following infection via the natural (oral) route. In studies comparing d and k haplotype mice a dramatic inverse relationship between splenic CD4:CD8 T cell ratios and brain cyst number was observed, particularly in the strain (BALB/K; H-2k) most susceptible to high brain cyst numbers and subsequent toxoplasmic encephalitis. Of particular interest was the observation that splenomegaly and the relative increase in the splenic CD8 T cell population preceded and accompanied the very dramatic and rapid increase in brain cyst formation. The results suggest that the too rapid development of a potent anti-parasite response in the viscera may drive the parasite to encyst in the brain.