Isolation and comparison of the IgM heavy chain constant regions from Australian (Trichosurus vulpecula) and American (Monodelphis domestica) marsupials

cDNAs encoding IgM heavy chain constant region (Cμ) were isolated from two metatherians (marsupials) — the Australian common brushtail possum (Trichosurus vulpecula) and the South American grey short-tailed opossum (Monodelphis domestica). Analysis of the sequences suggested that they correspond to the secreted form of Cμ in both species. The domain size and structure of the marsupial Cμ sequences were compared with other Cμ sequences and a high degree of conservation throughout vertebrate evolution was observed. Amino acid sequence comparisons revealed a marked level of sequence similarity between the two marsupial sequences (79%), relatively high similarity between the marsupials and eutherians (63%), and lower similarities between marsupials and birds (45%), marsupials and amphibians (47%), marsupials and reptiles (45%) and marsupials and fish (37%). These data allow the incorporation of metatherians into the study of mammalian IgM evolution.     

Characterisation of echidna IgM provides insights into the time of divergence of extant mammals

The immunobiology of monotremes is poorly understood. In this paper, we describe the characterisation of the heavy chain of IgM from Tachyglossus aculeatus, the short-beaked echidna. The echidna heavy chain constant region of IgM (Cμ) was isolated from a spleen cDNA library using a Trichosurus vulpecula probe. It has approximately 46.5% amino acid identity to marsupial and eutherian Cμs, and approximately 30% amino acid identity with Cμs from birds and reptiles. Phylogenetic analysis of mammalian Cμ provides strong support for the Theria hypothesis, with a sister grouping of the eutherians and marsupials to the exclusion of the monotremes. Cμ sequences suggest that monotremes and therians separated approximately 170 million years ago (mya), marsupials and eutherians separated approximately 130 mya, and Australian and American marsupials separated approximately 65 mya.     

Cloning and structural analysis of IgM (mu chain) and the heavy chain V region repertoire in the marsupial Monodelphis domestica

To address the question of the Ig isotype repertoire of non placental mammals, we have examined the Ig expression in the marsupial Monodelphis domestica (grey short tailed opossum). Screening of an opossum spleen cDNA library has previously led to the isolation of full length clones for opossum IgG (γ chain), IgE ( chain) and IgA ( chain). We now present the isolation of several cDNA clones encoding the entire constant regions of the opossum IgM (μ chain). A comparative analysis of the amino acid sequences for IgM from various animal species showed that opossum IgM, within the various animals studied, is the most divergent member of its Ig class. However, it still conforms to the general structure of IgM in other vertebrates. Four Ig classes have now been identified in opossum and only one isotype is apparently present within each Ig class, IgM, IgG, IgA and IgE. Opossum has previously been shown to have a limited VH region diversity, with only two V gene families. Both of these belong to the group III of mammalian VH sequences. This limitation in variability is to some extent compensated for by a large variation in D, P and N regions, both in size and in sequence. However, evidence for the expression of only two functional J segments has so far been detected, which indicates a rather limited diversity also of the J segments in the opossum.     

Isolation and sequence of a cDNA coding for the heavy chain constant region of IgG from the Australian brushtail possum, Trichosurus vulpecula.

A brushtail possum (Trichosurus vulpecula) mesenteric lymph node cDNA library was screened with a South American short-tailed opossum (Monodlelphis domestica) immunoglobulin gamma heavy chain constant region (Cgamma) probe, resulting in the isolation of a 1518 nucleotide cDNA clone. The sequence corresponds to exons 1-3 of Cgamma. The Australian marsupial (T. vulpeculla) sequence is 70% identical at the amino acid level with the American marsupial (M. domestica) sequence, but less similar to the eutherian mammals (45-50%). These data provide the opportunity to compare the evolution of IgG between orders of marsupials separated by at least 75 million years and confirm the appearance of IgG prior to the metatherian/eutherian divergence.     

Production of interleukin-1 in a South American opossum (Monodelphis domestica)

A homologous thymocyte costimulatory assay using thymocytes from a South American opossum (Monodelphis domestica) detected and measured interleukin-1 (IL-1). Opossum IL-1 was obtained from lipopolysac-charide-stimulated macrophage and skin cultures and its molecular weight was determined to be 15,000 to 17,000. Opossum IL-1 did not stimulate proliferation of murine thymocytes; conversely, neither human nor murine IL-1 stimulated opossum thymocytes. Anti-human IL-1 antibodies were also not reactive with opossum IL-1. These observations indicate that there is no serological and functional crossreactivity between the opossum (marsupial mammals) and human and mouse (eutherian mammals) in an IL-1/thymocyte system. This is unusual because such crossreactivity occurs between rodents and distant, nonmammalian species. M. domestica has been used in our laboratory as a model for photobiological research; studies on IL-1 may provide insight into the relationship of immunosuppression and tumorigenesis induced by ultraviolet radiation.     

Cloning, expression, and characterization of recombinant Hev b 3, a Hevea brasiliensis protein associated with latex allergy in patients with spina bifida.

BACKGROUND: Two natural rubber latex proteins, Hev b 1 and Hev b 3, have been described in spina bifida (SB)-associated latex allergy. OBJECTIVE: The aim of this study was to clone and express Hev b 3 and to obtain the immunologic active and soluble recombinant allergen for diagnosis of SB-associated latex allergy. METHODS: A complementary DNA (cDNA) coding for Hev b 3 was amplified from RNA of fresh latex collected from Malaysian rubber trees (Hevea brasiliensis). PCR primers were designed according to sequences of internal peptide fragments of natural (n) Hev b 3. The 5'-end sequence was obtained by specific amplification of cDNA ends. The recombinant (r) Hev b 3 was produced in Escherichia coli as a 6xHis tagged protein. Immunoblotting and inhibition assays were performed to characterize the recombinant allergen. RESULTS: An Hev b 3 cDNA clone of 922 bp encoding a protein of 204 amino acid residues corresponding to a molecular weight of 22.3 kd was obtained. In immunoblots 29/35, latex-allergic patients with SB revealed IgE binding to rHev b 3, as did 4 of 15 of the latex-sensitized group. The presence of all IgE epitopes on rHev b 3 was shown by its ability to abolish all IgE binding to nHev b 3. Hev b 3 is related to Hev b 1 by a sequence identity of 47%. Cross-reactivity between these 2 latex allergens was illustrated by the large extent of inhibition of IgE binding to nHev b 1 by rHev b 3. CONCLUSION: rHev b 3 constitutes a suitable in vitro reagent for the diagnosis of latex allergy in patients with SB. The determination of the full sequence of Hev b 3 and the production of the recombinant allergen will allow the epitope mapping and improve diagnostic reagents for latex allergy.     

Cloning and functional expression of Rpn1, a regulatory-particle non-ATPase subunit 1, of proteasome from Trypanosoma cruzi

Non-lysosomal protein degradation in eukaryotic cells involves a proteolytic complex referred to as 26S proteasome that consists of a 20S core particle and one or two 19S regulatory particles. We have cloned the gene RPN1 encoding Rpn1 (regulatory-particle non-ATPase subunit 1), one of the largest subunits of proteasome, from Trypanosoma cruzi. It contains 2712 bp and encodes 904 amino acid residues with a calculated molecular mass of 98.2 kDa and an isoelectric point of 5.2. The predicted amino acid sequence of the trypanosomatid Rpn1 shares 39.0 and 32.0% overall identities with human Rpn1 and Saccharomyces cerevisiae Nas1 (non-ATPase subunit 1), an Rpn1 homolog, respectively, while the sequence identities among T. cruzi, Plasmodium falciparum, and Entamoeba histolytica Rpn1 are approximately 30%. T. cruzi Rpn1 contains nine repeats of about 36 amino acid residues conserved in Rpn1s from various organisms. T. cruzi RPN1 is located on the 2300- and 1900-kb chromosomal DNA, displays a putative allelic variation as RPN1-1 and RPN1-2 with 98.8% identity between these two putative gene products, and is transcribed from both alleles at a comparable level throughout the three developmental stages of the parasite, epimastigotes, trypomastigotes, and amastigotes. The expression of the trypanosomatid Rpn1 in the temperature-sensitive nas1 yeast mutant rescued the growth defect at the restrictive temperature, indicating that Rpn1 functions as a Nas1 and probably assembles into the 19S regulatory particle of the yeast 26S proteasome.     

Programmed Cell Death 5 from Toxoplasma gondii: a secreted molecule that exerts a pro-apoptotic effect on host cells

Although parasite-infected host cells become resistant to apoptosis, uninfected bystander cells undergo apoptosis during Toxoplasma gondii infection. The Programmed Cell Death 5 (TgPDCD5) gene, a homologue of the human apoptosis-related molecule, was cloned from a T. gondii full-length cDNA database and subsequently characterized. The native TgPDCD5 was located in the cytosol and also detected in the secreted fraction. Immuno-electron microscopic analysis showed TgPDCD5 was primarily located close to the rhoptries or vesicle-like structures near the surface membrane of the parasite. Studies using recombinant TgPDCD5 (rTgPDCD5) demonstrated that host cells internalize the molecule in a heparan sulfate proteoglycan-binding motif-dependent manner. Furthermore, the addition of rTgPDCD5 to culture medium resulted in the enhancement of host-cell apoptosis triggered by etoposide in macrophage cell line J774A.1 and leukemic cell line HL-60 cells. Additionally, rTgPDCD5 induced apoptosis in J774A.1 cells in the presence of IFN-γ. This report is the first to identify a parasitic molecule of T. gondii that has a pro-apoptotic effect on host cells.     

Molecular characterisation of the tammar wallaby (Macropus eugenii) CD3 epsilon chain cDNA.

The cDNA encoding the epsilon chain of the tammar wallaby CD3 complex (CD3epsilon) was isolated by PCR. This is the first CD3 component to be cloned in a marsupial. The tammar wallaby cDNA coding region was 61.7 and 63.0% identical to the human and mouse cDNA coding sequences, respectively. Similarly, the predicted amino acid sequence was 56.5 and 52.9% identical to the human and mouse sequences. When compared with other known CD3epsilon peptide sequences, the most conserved region of the tammar wallaby CD3epsilon chain peptide was the cytoplasmic domain and the least conserved was the extracellular portion. Phylogenetic reconstruction based on the deduced amino acid sequence placed the tammar wallaby sequence in its expected position outside of all the eutherian mammals.     

Interferon-gamma suppresses the growth of Toxoplasma gondii in human fibroblasts through starvation for tryptophan

The effect of human recombinant interferon-γ (IFN-γ) on Toxoplasma gondii in cultured human fibroblasts is predominantly parasitostatic. This effect is dependent upon the induction in the host cell of a potent indoleamine 2,3-dioxygenase that converts tryptophan to N-formylkynurenine. This product is, in turn, degraded to kynurenine by a formamidase. Within 24 h of treatment with IFN-γ most of the tryptophan originally present in the medium is converted to these products together with some minor metabolites. When added to the medium of infected cultures at concentrations equimolar to the tryptophan content, neither N-formylkynurenine nor kynurenine suppresses the growth of T. gondii, although at higher concentrations they are effective. The medium of uninfected cultures treated with IFN-γ for 24 h has no effect on the growth of T. gondii, when transferred to fresh cultures provided that the residual IFN-γ is first removed by ultrafiltration or neutralized with a specific monoclonal antibody. Thus minor metabolites produced from tryptophan in response to IFN-γ and excreted into the medium are not parasitostatic. When cultures treated with IFN-γ for 24 h are incubated with medium that contains [³H]tryptophan, the radioactive amino acid is converted to N-formylkynurenine and kynurenine as rapidly as it enters the cell. This degradation not only results in a very low intracellular concentration of tryptophan but also produces intracellular concentrations of tryptophan metabolites that are significantly higher than the tryptophan concentration in control cells. However, it is unlikely that either metabolite reaches intracellular concentrations that are sufficient to suppress the growth of the parasite. The parasitostatic effect of IFN-γ is most likely to result from the starvation of T. gondii for tryptophan.     

Protective effect and granuloma down-modulation promoted by RP44 antigen a fructose 1,6 bisphosphate aldolase of Schistosoma mansoni

A Schistosoma mansoni adult worm cDNA expression library was screened using rabbit IgG against PIII, an adult worm protein fraction, already known to possess protective and immunomodulating effects to a challenge infection in mice. A positive cDNA clone was selected and characterized. The cDNA screened encodes a protein (P44) with an ORF of 1089 bp and an amino acid sequence of 363 residues with a predictable molecular weight of 44 kDa. The P44 amino acid sequence exhibits 100% identity to the fructose 1,6 bisphosphate aldolase of S. mansoni, 66% to Homo sapiens and 66% to Mus musculus. The cDNA was cloned into a pGEX-4T-3 vector and expressed in Escherichia coli as a fusion protein (GST/P44). Mice vaccinated with recombinant P44 were able to develop high levels of IgG or IgG1 and displayed low levels of IgG2a isotype. Moreover, immunization of mice with this antigen induced a significant protection of 57% against a challenge infection and significant decrease in hepatic granuloma formation. Our results demonstrate that granuloma modulation can be targeted for pathology elimination through vaccination. This represents an advance in schistosome vaccinology and allows for the development of a therapeutic as well as a prophylactic vaccine.     

Cloning of the panallergen profilin from lychee fruit and its cross-reactivity with birch pollen profilin Bet v 2

Lychee fruits can cause severe anaphylactic reactions and has cross-reactivity with other allergens. Panallergen profilin is partly responsible for the cross-reactivity between allergens. In the present study, the cDNA of lychee profilin was performed by RT-PCR and 3'RACE from total RNA. The lychee profilin cDNA includes an open reading frame coding for 131 amino acids. The deduced amino acid sequence of the corresponding protein show high identity with other allergenic profilins. Expression of the recombinant lychee profilin was carried out in Escherichia coli BL21 (DE3) using vector PET-28a, and the purification of the recombinant protein was performed via affinity chromatography with Ni⁺ coupled to sepharose. IgE reactivity of recombinant lychee profilin was investigated by immunoblot, and five of 15 lychee-allergic patients tested presented specific IgE antibodies to recombinant lychee profilin. IgE inhibition and ELISA inhibition experiments were performed to analyze lychee profilin cross-reactivity with profilins from birch pollen, and a high cross-reactivity between lychee profilin and birch profilin has been found in sera from lychee allergic patients.     

Evidence for an early appearance of modern post-switch immunoglobulin isotypes in mammalian evolution (II); cloning of IgE,IgG1 and IgG2 from a monotreme,the duck-billed platypus,Ornithorhynchus anatinus

To trace the emergence of the modern post-switch immunoglobulin (Ig) isotypes in vertebrate evolution we have studied Ig expression in mammals distantly related to eutherians. We here present an analysis of the Ig expression in an egg-laying mammal, a monotreme, the duck-billed platypus (Ornithorhynchus anatinus). Fragments of platypus IgG and IgE cDNA were obtained by a PCR-based screening using degenerate primers. The fragments obtained were used as probes to isolate full-length cDNA clones of three platypus post-switch isotypes, IgG1, IgG2, and IgE. Comparative amino acid sequence analysis against IgY, IgE and IgG from various animal species revealed that platypus IgE and IgG form branches that are clearly separated from those of their eutherian (placental) counterparts. However, the platypus IgE and IgG still conform to the general structure displayed by the respective Ig isotypes of eutherian and marsupial mammals. According to our findings, all of the major evolutionary changes in the expression array and basic Ig structure that have occurred since the evolutionary separation of mammals from the early reptile lineages, occurred prior to the separation of monotremes from marsupial and placental mammals. Hence, our results indicate that the modern post-switch isotypes appeared very early in the mammalian lineage, possibly already 310-330 million years ago.     

Potential influence of interleukin-1 haplotype IL-1 beta-511*T-IL-1RN*1 in conferring low risk to middle third location of esophageal cancer: a case-control study

Interleukin (IL)-1 gene polymorphisms affect several inflammatory diseases, including cancer. Therefore, we studied genetic association of biallelic (-511C>T) polymorphism of IL-1β and 86-bp VNTR polymorphism of IL-1RN in 159 patients with esophageal cancer (EC) and 194 age- and gender-matched healthy controls. Genetic analysis for IL-1 polymorphisms was performed by polymerase chain reaction-restriction fragment length polymorphism. The frequencies of IL-1β (-511C>T) and IL-1RN (variable number tandem repeat) genotypes, alleles, and haplotypes did not differ significantly between patients and controls. However, IL-1β -511TT genotype and T1+ haplotype combination illustrated low risk for disease at the middle third location of the tumor (odds ratio [OR] = 0.27; 95% confidence interval [CI] = 0.11–0.62; p = 0.002; OR = 0.462; 95% CI = 0.253–0.845, p = 0.01). In conclusion, subjects with IL-1β -511TT genotype or IL-1β*T-IL-1RN*1 (T1) haplotype had lower risk for middle third tumor location of EC in a northern Indian population.     

Cloning of the MHC class II DRB cDNA from the brushtail possum (Trichosurus vulpecula)

The cell-surface glycoproteins encoded by the major histocompatibility complex (MHC) bind to processed foreign antigens and present them to T lymphocytes. Two classes of MHC molecules and their corresponding gene sequences have been extensively studied in eutherian mammals and birds, but data on the marsupial MHC are limited. Marsupials split from eutherian mammals about 125 million years ago and represent a distinct branch in mammalian evolution. Here the cDNA cloning of MHC class II genes of the brushtail possums (Trichosurus vulpecula) is reported. The sequences obtained were found to be relatively conserved when compared to the red-necked wallaby (Macropus rufogriseus) and an South American marsupial, Monodelphis domestica. The T. vulpecula sequence shared an average overall sequence identity of 75.4% at the deduced amino acid level with M. rufogriseus and M. domestica, respectively.     

Molecular cloning and characterization of actin genes from Echinococcus granulosus

An Echinococcus granulosus genomic library has been screened with a mouse β-actin cDNA probe. Two clones carrying DNA fragments of about 15 kb, possibly derived from the same genome region, have been isolated. This 15-kb genomic region includes 2 actin-related sequences (EgactI and EgactII) separated by about 4 kb. The nucleotide sequences of both genes were determined. The EgactI sequence presents no introns, but an intron of 591 bp was observed in the EgactII sequence. The genes potentially encode 375 and 376 amino-acid-long actins, respectively, with a homology of 85.3%. The deduced amino acid sequences from both genes were compared to the actin sequences from other organisms, showing similarities ranging from 63.5% to 90.6%. The nucleotide sequence of a partial actin cDNA clone has been determined. The deduced amino acids sequence showed a homology of 90.3% and 88.0% in relation to the EgactI and EgactII sequences respectively, suggesting the existence of at least one more actin gene in E. granulosus. This hypothesis is reinforced by the number of bands detected in the Southern blot analysis. Experiments based on the amplification of DNA segments using 3′-specific actin primers indicate that the EgactI gene is transcribed in protoscoleces.     

Cloning of a cDNA encoding phosphoenolpyruvate carboxykinase from Haemonchus contortus.

Biochemical and metabolic data have led to the conclusion that the enzyme phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.32) contributes to a critical point of divergence in energy conservation pathways between mammals and nematodes. To facilitate the determination of the molecular basis for host vs parasite differences in PEPCK, we have cloned a cDNA encoding this enzyme from a parasitic nematode of ruminants, Haemonchus contortus. H. contortus PEPCK was cloned by functional complementation of a PEPCK, malic enzyme strain of Escherichia coli (E1786) using an egg stage H. contortus cDNA library in λZAPII. Selection was for growth on malate as the sole carbon source (malate phenotype). We isolated a plasmid, pPEPCK, which reproducibly confers a malate phenotype in E1786. The sequence of the 2.0-kb EcoRI insert of pPEPCK predicts a 612-amino acid protein which shows about 74% similarity to Drosophila melanogaster and chicken PEPCK. Extracts of E1786[pPEPCK], but not E1786, contain IDP- or GDP-dependent PEPCK enzyme activity. Sequence analysis revealed that the open reading frame (ORF) in pPEPCK lacked a 5′ initiation codon and was probably expressed as an in-frame fusion protein with β-galactosidase. A strategy combining library screening with PCR analysis of positive clones led to the identification of a clone encoding 6 additional NH₂-terminal amino acids, including a Met, which, by comparison with known PEPCK amino acid sequences, is likely to be the translation initiation site.     

Cloning and structural analysis of IgM (μ chain) and the heavy chain V region repertoire in the marsupial Monodelphis domestica

To address the question of the Ig isotype repertoire of non placental mammals, we have examined the Ig expression in the marsupial Monodelphis domestica (grey short tailed opossum). Screening of an opossum spleen cDNA library has previously led to the isolation of full length clones for opossum IgG (γ chain), IgE ( chain) and IgA (α chain). We now present the isolation of several cDNA clones encoding the entire constant regions of the opossum IgM (μ chain). A comparative analysis of the amino acid sequences for IgM from various animal species showed that opossum IgM, within the various animals studied, is the most divergent member of its Ig class. However, it still conforms to the general structure of IgM in other vertebrates. Four Ig classes have now been identified in opossum and only one isotype is apparently present within each Ig class, IgM, IgG, IgA and IgE. Opossum has previously been shown to have a limited VH region diversity, with only two V gene families. Both of these belong to the group III of mammalian VH sequences. This limitation in variability is to some extent compensated for by a large variation in D, P and N regions, both in size and in sequence. However, evidence for the expression of only two functional J segments has so far been detected, which indicates a rather limited diversity also of the J segments in the opossum.