Novel genes mapping to the critical region of the 5q- syndrome

The 5q- syndrome is a myelodysplastic syndrome with specific hematological features and a good prognosis. Using molecular mapping techniques, we have previously defined the critical region of gene loss of the 5q- chromosome in the 5q- syndrome as the approximately 5-Mb region at 5q31-q33 flanked by the genes for FGF1 and IL12B. This region is completely represented by a series of overlapping YACs, and we are currently generating a transcription map with the aim of identifying the tumor-suppressor gene associated with the development of the 5q- syndrome. In this study two techniques have been used: first, the screening of full-length cDNA libraries with radiolabeled YACs and second, the mapping of chromosome 5-specific expressed sequence tags (ESTs) to a YAC contig. A 1-Mb YAC contig encompassing the CSF1R gene has been used to screen a fetal brain cDNA library, and this has resulted in the identification of two genes comprising one known gene previously localized to the region (ADRB2) and one known gene previously unlocalized. Six of 135 chromosome 5-specific ESTs were localized by PCR screening to the YAC contig mapping to the critical region of the 5q- syndrome. IMAGE cDNA clones for each of the six ESTs have been obtained. These seven (excluding ADRB2) newly assigned cDNA clones were subjected to further analysis. The expression patterns of each of the cDNA clones have been established in a range of human tissues, including bone marrow. Six of seven cDNAs are expressed in human bone marrow. Six of seven cDNAs have no known homology to any deposited human sequences, and one (C29) is dihydropyrimidinase-related protein-3, a member of a novel gene family. Genomic localization and expression patterns would suggest that these newly assigned cDNAs represent potential candidate genes for the 5q- syndrome.

Immunization of mice with DNA encoding fragment C of tetanus toxin

Immunization of mice with Fragment C protein, the non-toxic C-terminal domain of tetanus toxin, will protect mice against lethal challenge with tetanus toxin. A plasmid, pcDNA3/tetC, which encodes a synthetic tetC gene expressed under the control of the human cytomegalovirus major intermediate early promoter/enhancer region, was constructed. Fragment C expression was observed in Chinese hamster ovary cells following transfection with pcDNA3/tetC. The immune response induced by intramuscular immunization with pure pcDNA3/tetC DNA was evaluated in a murine model. Anti-Fragment C serum immunoglobulin and proliferative responses in splenocytes were observed following two immunizations with pcDNA3/tetC. The major IgG subclass that recognized Fragment C was IgG2a and the stimulated splenocytes secreted high levels of interferon-gamma. Sufficient anti-Fragment C serum immunoglobulins were induced by DNA-mediated immunization to protect mice against lethal challenge with tetanus toxin.

Cloning and characterisation of the rabbit 5-HT1D alpha and 5-HT1D beta receptors

The genes encoding the rabbit 5HT1D alpha and 5HT1D beta receptors have been cloned. The deduced amino acid sequence of these receptors shows 91-92% amino acid sequence identity with their human homologues, and similar high sequence identity with homologues from other species. The receptors were transiently expressed in COS-7 cells and exhibit a pharmacological profile closely resembling their human homologues, including a higher affinity of ketanserin for the 5-HT1D alpha subtype. However, sumatriptan had a lower affinity for both the rabbit receptors compared to their human counterparts. This may be accounted for by differences between the primary amino acid sequences of these species homologues.

Characterization of recombinant tetanus toxin derivatives suitable for vaccine development

Recombinant derivatives of tetanus toxin (TeTx) were isolated and used to immunize mice. Recombinant TeTx light chain, a derivative of fragment C that had lost the ability to bind neurons, and a recombinant TeTx holotoxoid that could protect mice against TeTx challenge were identified.

Modulation of antigen processing by bound antibodies can boost or suppress class II major histocompatibility complex presentation of different T cell determinants

Bound antibodies can modulate antigen processing but it is not clear to what extent this affects antigen presentation. Here we show that presentation of T cell determinants in tetanus toxin can be either enhanced or suppressed as a direct consequence of antibody modulation of antigen processing in human B lymphoblastoid cells. Remarkably, a single bound antibody or its Fab fragment can simultaneously enhance the presentation of one T cell determinant by more than 10-fold while strongly suppressing the presentation of a different T cell determinant. Biochemical analysis demonstrates that both the suppressed and boosted determinants fall within an extended domain of antigen stabilized or "footprinted" by this antibody during proteolysis. These results demonstrate that bound antibodies can modulate the capture of peptides by class II major histocompatibility complex (MHC), thus manipulating the T cell response towards or away from particular determinants. Altered processing of protein-protein complexes leading to enhanced loading of class II MHC and substantially lowered threshold for T cell activation suggests a novel mechanism that might reveal "cryptic" self determinants.

Expression of the Bordetella pertussis P.69 pertactin adhesin in Escherichia coli: fate of the carboxy-terminal domain

The mature pertactin protein (P.69) of Bordetella pertussis can be isolated from the bacterial cell surface as a polypeptide with an apparent molecular mass of 69,000 Da as determined by sodium dodecyl sulphate gel electrophoresis. However the open reading frame of prn, the pertactin gene, encodes a polypeptide with a predicted molecular mass of 93,478 Da, referred to as P.93. Expression of the prn gene in Escherichia coli leads to the synthesis of the full-length P.93 polypeptide, which is rapidly processed to the mature P.69 protein located at the cell surface. The P.93 precursor polypeptide is processed at both termini. A 34 amino acid long signal sequence is removed from the amino-terminus and a polypeptide sequence of about 30,000 Da (P.30) is cleaved from the carboxy-terminus. Deletion of the 3' region of prn, encoding P.30, results in the expression of an intracellular form of P.69. Antiserum which recognizes P.30 was raised using synthetic peptides based on the primary amino acid sequence of the region. This anti-P.30 serum was used in a Western blot analysis of fractionated cells of B. pertussis and E. coli harbouring the intact prn gene. The P.30 polypeptide was readily detected in outer membrane fractions prepared from both of these bacterial species, although it could not be shown to be exposed at the cell surface.

Construction, expression, and immunogenicity of the Schistosoma mansoni P28 glutathione S-transferase as a genetic fusion to tetanus toxin fragment C in a live Aro attenuated vaccine strain of Salmonella

A vector has been constructed to allow genetic fusions of guest antigens via a hinge domain to the C terminus of the highly immunogenic C fragment of tetanus toxin. A fusion has been constructed with the gene encoding the protective 28-kDa glutathione S-transferase (EC 2.5.1.18) from Schistosoma mansoni. The recombinant vector has been electroporated into the nonvirulent Salmonella typhimurium aroA live vaccine strain SL3261. The corresponding chimeric protein is stably expressed in a soluble form in Salmonella as evaluated by Western blotting with fragment C and glutathione S-transferase antisera. Mice immunized intravenously with a single dose of the live recombinant bacteria elicit antibodies to both fragment C and glutathione S-transferase as detected by enzyme-linked immunosorbent assays. Furthermore, all of the mice were solidly protected when challenged with lethal doses of either tetanus toxin or the virulent Salmonella typhimurium strain C5. Mice have also elicited antibodies to fragment C and glutathione S-transferase after oral immunization. It may be that a live trivalent vaccine against typhoid, tetanus, and schistosomiasis is feasible.

Processing and presentation of tetanus toxin by antigen-presenting cells from patients with chronic granulomatous disease (CGD) to human specific T cell clones are not impaired

The capacity of peripheral blood lymphocytes (PBL) or Epstein-Barr virus (EBV)-transformed B cell lines from CGD patients to process and present tetanus toxin (tt)-specific epitopes was assessed using various tt preparations and human tt-specific T cell clones. PBL from all of the donors were able to process and present either native tt and/or denatured tt to human T cell clones specific for various tt epitopes. Furthermore, no difference was found in the antigen requirement when normal or CGD EBV-B cell lines were used as antigen-presenting cells (APC). These results suggest that the deficiency in oxygen metabolism in CGD cells does not affect tt processing and presentation.

Mutations in the connexin 32 gene in X-linked dominant Charcot-Marie-Tooth disease (CMTX1)

X-linked dominant Charcot-Marie-Tooth disease (CMTX1) is a peripheral neuropathy which maps to Xq13 and is flanked by the loci DXS106 (Xq11.2-q12) and DXS559 (Xq13.1). Contained within this interval of approximately 2-3Mb of DNA is the gene, connexin 32 (locus designation GJ beta 1). This gene encodes a gap junction protein which is expressed in large quantities within the liver and throughout a range of other mammalian tissues. We have sequenced the coding region of exon 2 of this gene from affected individuals in nine families with CMTX 1 and have found mutations which segregate with the disease in eight of these families. The mutations detected include missense point mutations at codons 15, 60, 63, 208, and 215, a nonsense point mutation at codon 220, deletions of one base in codon 72/3 producing a stop codon 12 codons down stream and a three base pair deletion which can be predicted to result in the loss of a single amino acid. These findings are consistent with the disease CMTX1 being the result of mutations affecting the gene connexin 32 (Cx32).

Expression of P.69/pertactin from Bordetella pertussis in a baculovirus/insect cell expression system: protective properties of the recombinant protein

The surface antigen P.69/pertactin of Bordetella pertussis has been expressed using the polyhedron promoter of baculovirus in cultured insect cells. Either full-length or truncated prn DNA was used to express P.69 pertactin. The full-length gene gave rise to low levels of P.93 precursor protein, some of which was processed to P.69. The shortened prn expressed P.69 pertactin directly at levels up to 3.5 mg per litre. P.69 vaccinated animals were protected against aerosol challenge with virulent B. pertussis bacteria.

Fine mapping of the human SCIDX1 locus at Xq12-13.1

Previous linkage analysis of families with X-linked severe combined immunodeficiency (SCIDX1) mapped this locus to a large region encompassing about 10 to 20 cM at Xq12-21. We have analyzed in SCIDX1 families the segregation of 7 highly polymorphic microsatellites repeats localized to this region, including a new polymorphic microsatellite at the DXS135 locus described in this study, to refine the mapping of this disease locus. The observations of genetic recombinants within the previously defined SCIDX1-region allow us to establish new flanking markers at the DXS135 and DXS227 loci, which significantly reduce the region harboring the SCIDX1 locus to a distance estimated between 3 to 5 cM. The existence of multiple, highly polymorphic markers in the refined SCIDX1 region will greatly improve the accuracy of carrier detection and prenatal diagnosis for SCIDX1.

Crystallographic characterization of tetanus toxin fragment C

The C-terminal fragment from tetanus toxin has been crystallized. The 50 kDa protein forms prismatic crystals with an orthorhombic unit cell of dimensions a = 64.03 A, b = 76.31 A and c = 135.3 A. The space group is P2(1)2(1)2(1). Assuming one molecule per asymmetric unit, the solvent occupies 63% of the unit cell.

Characterization of a Salmonella typhimurium aro vaccine strain expressing the P.69 antigen of Bordetella pertussis

The P.69 Bordetella pertussis protective antigen was expressed by use of the trc promoter from the chromosome of a Salmonella typhimurium aro vaccine strain, BRD509, by integrating the prn gene, encoding the 93-kDa precursor of this protein, into the aroC locus. P.69 was detected on the cell surface of the S. typhimurium strain (BRD640) by agglutination and immunoelectron microscopy. BALB/c mice immunized orally or intravenously with BRD640 showed a significant level of protection against an aerosol challenge with virulent B. pertussis, compared with control animals. No anti-P.69 antibodies in the serum or anti-P.69 antibody-secreting cells in the lungs were detected in BRD640-vaccinated animals, although cells isolated from spleens showed a P.69-dependent cell proliferative response. In contrast, low levels of anti-P.69 antibodies in the serum and anti-P.69 antibody-secreting cells in the lungs were detected in immunized mice following a B. pertussis challenge.

Construction of a genetically defined Salmonella typhi Ty2 aroA, aroC mutant for the engineering of a candidate oral typhoid-tetanus vaccine

The construction of a Salmonella typhi Ty2 strain harbouring defined deletions in both the aroA and aroC genes is described. These deletions have been fully defined at the molecular level by DNA sequencing and have been introduced in such a way that no foreign DNA remains in the S. typhi genome. This strain is attenuated in mice when given by the intraperitoneal route suspended in hog gastric mucin and is attenuated to a similar level to strains harbouring deletions in aroA or aroC alone indicating that both lesions are capable of attenuating independently. We have used this defined S. typhi aroA aroC strain to express stably a non-toxic 50 kDa fragment of tetanus toxin (fragment C) from a gene incorporated into the chromosome. This strain has the advantage of harbouring no antibiotic-resistance markers and we consider it to be a candidate bivalent oral typhoid-tetanus vaccine.

Prenatal diagnosis for dystrophia myotonica using the polymerase chain reaction

The polymerase chain reaction has been used to detect an abundant class of short repeat DNA families of the form (dC-dA)n.(dG-dT)n, known as microsatellites. These units are found throughout the human genome and have been characterized for several loci including APOC2 on chromosome 19q12-q13.2. The locus APOC2 is linked to the gene for dystrophia myotonica and a microsatellite within this locus was used to derive polymorphisms in a family to predict the inheritance of the disease. Chorionic villus sampling (CVS) was performed at 15 1/2 weeks' gestation. Following DNA extraction from the CVS material and parental blood samples, microsatellite analysis was carried out by the polymerase chain reaction.

Molecular cloning and characterization of the aroD gene encoding 3-dehydroquinase from Salmonella typhi

The aroD gene from Salmonella typhi, encoding 5-dehydroquinate hydrolyase (3-dehydroquinase), has been cloned into Escherichia coli and the DNA sequence determined. The aroD gene was isolated from a cosmid gene bank by complementation of an S. typhimurium aroD mutant. Analysis of the DNA sequence revealed the presence of an open reading frame capable of encoding a protein of 252 amino acids with a calculated Mr of 27706. Comparison of the deduced S. typhi 3-dehydroquinase protein sequence with that elucidated for E. coli revealed 69% homology. Alignment of the S. typhi sequence and equivalent Aspergillus nidulans and Saccharomyces cerevisiae sequences showed that homology was lower, at 24%, but still significant. Use of a minicell expression system demonstrated that a polyclonal antibody raised against E. coli 3-dehydroquinase cross-related with its S. typhi counterpart.

Oral Salmonella typhimurium (AroA-) vaccine expressing a major leishmanial surface protein (gp63) preferentially induces T helper 1 cells and protective immunity against leishmaniasis

The gp63 gene of Leishmania major was transformed into the AroA- vaccine strain of Salmonella typhimurium (SL3261). The construct (SL3261-gp63), which stably expresses the gp63 Ag in vitro, was used to immunize CBA mice by the oral route. Spleen cells from mice inoculated with SL3261-gp63 developed antibody and proliferative T cell response to L. major. They did not express detectable delayed-type hypersensitivity reactivity. The activated T cells are mainly CD4+ and secrete IL-2 and IFN-gamma but no IL-4. The orally immunized mice developed significant resistance against a challenge L. major infection. We have, therefore, demonstrated the feasibility of oral vaccination against leishmaniasis and that the oral route of antigen delivery via the heterologous carrier may preferentially induce Th1 subsets of CD4+ cells.

Oral Salmonella typhimurium (AroA-) vaccine expressing a major leishmanial surface protein (gp63) preferentially induces T helper 1 cells and protective immunity against leishmaniasis

The gp63 gene of Leishmania major was transformed into the AroA- vaccine strain of Salmonella typhimurium (SL3261). The construct (SL3261-gp63), which stably expresses the gp63 Ag in vitro, was used to immunize CBA mice by the oral route. Spleen cells from mice inoculated with SL3261-gp63 developed antibody and proliferative T cell response to L. major. They did not express detectable delayed-type hypersensitivity reactivity. The activated T cells are mainly CD4+ and secrete IL-2 and IFN-gamma but no IL-4. The orally immunized mice developed significant resistance against a challenge L. major infection. We have, therefore, demonstrated the feasibility of oral vaccination against leishmaniasis and that the oral route of antigen delivery via the heterologous carrier may preferentially induce Th1 subsets of CD4+ cells.

Stable expression of foreign antigens from the chromosome of Salmonella typhimurium vaccine strains

A simple and versatile system has been developed using a new cloning vector which can serve as a vehicle for integrating DNA fragments, which direct the expression of heterologous antigens, into the aroC gene on the Salmonella chromosome. The system is based on Escherichia coli plasmid vectors which contain the DNA fragment, cloned from the chromosome of S. typhimurium C5, which encodes the aroC gene. The aroC gene was modified using synthetic oligodeoxyribonucleotides so that it contained several unique restriction sites into which DNA, directing the expression of heterologous antigens, could be cloned. DNA was integrated into the S. typhimurium chromosome at aroC by transferring the vectors into S. typhimurium polA mutants and allowing homologous recombination to occur between the cloned and chromosomal aroC genes. The vectors were used to integrate nucleotide sequences into the S. typhimurium chromosome which directed the expression of tetanus toxin fragment C and the Treponema pallidum lipoprotein. The expression of both antigens was detected by Western blotting.

Linkage in a family with X-linked Charcot-Marie-Tooth disease

The gene for the X-linked form of Charcot-Marie-Tooth disease (CMT Peroneal Muscular Atrophy, X-linked: McKusick No. 30280) has been shown in a single family to be linked to DXYS1 with a lod score of 4.55 at a recombination fraction of 0.03 and to PGK1 with a lod score of 3.34 at zero recombination. This is in agreement with previous work based on several families. Pooled data from this family and 7 previously reported families give a maximum lod score of 12.04 at theta max of 0.05 for linkage between CMTX and DXYS1 loci.