H. van Ormondt

Adenosine deaminase: characterization and expression of a gene with a remarkable promoter.

Cosmid clones containing the gene for human adenosine deaminase (ADA) were isolated. The gene is 32 kb long and split into 12 exons. The exact sizes and boundaries of the exon blocks including the transcription start sites were determined. The sequence upstream from this cap site lacks the TATA and CAAT boxes characteristic for eukaryotic promoters. Nevertheless, we have shown in a functional assay that a stretch of 135 bp immediately preceding the cap site has promoter activity. This 135‐bp DNA fragment is extremely rich in G/C residues (82%). It contains three inverted repeats that allow the formation of cruciform structures, a 10‐bp and a 16‐bp direct repeat and five G/C‐rich motifs (GGGCGGG) disposed in a strikingly symmetrical fashion. Some of these structural features were also found in the promoter region of other genes and we discuss their possible function. Knowledge of the exact positions of the intron‐exon boundaries allowed us to propose models for abnormal RNA processing that occurs in previously investigated ADA‐deficient cell lines.

Specific tumor-cell killing with adenovirus vectors containing the apoptin gene

Specificity is an essential prerequisite for cancer gene therapy. Recently we described that apoptin, a protein of 121 amino acids which is derived from the chicken anemia virus, induces programmed cell death or apoptosis in transformed and malignant cells, but not in normal, diploid cells (Danen-van Oorschot AAAM et al, Proc Natl Acad Sci USA 1997; 94: 5843–5847). This protein has an intrinsic specificity that allows it to selectively kill tumor cells, irrespective of the p53 or Bcl-2 status of these cells. Hence, it is attractive to explore the use of the apoptin gene for therapeutic applications, viz cancer gene therapy. In this paper, we describe the generation and characterization of an adenovirus vector, AdMLPvp3, for the expression of apoptin. Despite the fact that apoptin ultimately induces apoptosis in the helper cells, which are transformed by the adenovirus type 5 early region 1 (E1), the propagation kinetics and yields of AdMLPvp3 are similar to those of control vec- tors. Infection with AdMLPvp3 of normal rat hepatocytes in cell culture did not increase the frequency of apoptosis. In contrast, in the hepatoma cell lines HepG2 and Hep3b, infection with AdMLPvp3, but not with control vectors, led to a rapid induction of programmed cell death. Experiments in rats demonstrated that AdMLPvp3 could be safely administered by intraperitoneal, subcutaneous or intravenous injection. Repeated intravenous doses of AdMLPvp3 were also well tolerated, indicating that the apoptin-expressing virus can be administered without severe adverse effects. In a preliminary experiment, a single intratumoral injection of AdMLPvp3 into a xenogeneic tumor (HepG2 cells in Balb/Cnu/nu mice) resulted in a significant reduction of tumor growth. Taken together, our data demonstrate that adenovirus vectors for the expression of the apoptin gene may constitute a powerful tool for the treatment of solid tumors.

The nucleotide sequence of the transforming BglII-H fragment of adenovirus type 7 DNA

The primary structure of the HpaI-E fragment of adenovirus type 5 (Ad5) DNA has been determined, mainly by the method of Maxam and Gilbert (1977). This fragment comprises the leftmost 4.5% of the Ad5 genome, and has been shown to be the shortest DNA fragment capable of transforming cells. The identification of potential initiation and termination codons in the determined sequence indicates that two small polypeptides consisting of 186, and 81 amino acids, respectively, could be synthesized. Taking into account recent data on RNA splicing, a possibility is considered that this DNA may code also for larger polypeptides.

Comparison of nucleotide sequences of the early E1a regions for subgroups A, B and C of human adenoviruses

The early E1a regions (map position (0--4.5%) of highly oncogenic (subgroup A) adenovirus serotype 12 (Ad12), weakly oncogenic (subgroup B) adenovirus serotype 7 (Ad7) and non-oncogenic (subgroup C) adenovirus serotype 5 (Ad5) can convert cells in vitro into an immortal cell line. A comparison of the nucleotide sequences for the E1a regions of Ad12 (Sugisaki et al., 1980), Ad7 (Dijkema et al., 1980), and Ad5 (Van Ormondt et al., 1978) DNA is presented. The overall homology is about 50%, but certain segments of the E1a regions exhibit higher than average homology, for both coding and noncoding sequences. The latter may specify the initiation of DNA replication, DNA encapsidation and regulation of expression. The predicted polypeptides encoded by the E1a regions of the three serotypes exhibit a large degree of homology.

The primary structure of elongation factor EF-1 alpha from the brine shrimp Artemia.

cDNA as well as amino acid sequencing has revealed the complete primary structure of elongation factor EF‐1 alpha from the brine shrimp Artemia. A comparison with the published sequences of bacterial EF‐Tu, mitochondrial EF‐Tu and chloroplastic EF‐Tu shows that distinct areas of these polypeptide chains are conserved in evolution. The evolutionary distance between prokaryotic and eukaryotic types of EF‐Tu is larger than among bacterial and organellar EF‐ Tus . A number of regions present in both EF‐Tu and EF‐G from Escherichia coli are also found in EF‐1 alpha from Artemia.

Nucleotide Sequences of Adenovirus DNAs

The forty-odd identified human adenoviruses have been classified into groups A–G on the basis of DNA homology. After denaturation and renaturation of Ad DNA, single-stranded circles can be detected by electron microscopy, indicating that Ad DNA contains an inverted terminal repetition (ITR) of the type 5′ a b c ......c′ b′ a′ 3′a′b′c′ ......c b a A number of these ITRs have been elucidated at the nucleotide level, belonging to human serotype groups A–E and also comprising sequences from simian, equine, canine, prosimian (tupaia), rodent (mouse) and avian adenoviruses (Table 1.1).

Photodynamic inactivation of retroviruses by phthalocyanines: The effects of sulphonation, metal ligand and fluoride

The photodynamic inactivation of retroviruses was investigated using aluminium and zinc phthalocyanine (Pc) derivatives. The N2 retrovirus packaged in either of the two murine cell lines, Psi2 and PA317, was used as a model for enveloped viruses. AlPc derivatives were found to be more effective photodynamically for inactivation of the viruses than the corresponding ZnPc derivatives. Sulphonation of the Pc macrocycle reduced its photodynamic activity progressively for both AlPc and ZnPc. Fluoride at 5 mM during light exposure completely protected viruses against inactivation by AlPc. In the presence of F-, inactivation by the sulphonated derivatives AlPcS1 and AlPcS4 was reduced 2.5- and twofold respectively. In a biological membrane (erythrocyte ghosts), F- had no significant effect on AlPcS4-sensitized lipid peroxidation. Under similar conditions, cross-linking of spectrin monomers in ghosts is drastically inhibited (E. Ben-Hur and A. Orenstein, Int. J. Radiat. Biol., 60 (1991) 293-301). Since Pc derivatives do not inactivate non-enveloped viruses, it is hypothesized that inactivation occurs by photodynamic damage to envelope protein(s). Substitution of sulphonic acid residues reduces the binding of Pc derivatives to the envelope protein(s), thereby diminishing their photodynamic efficacy and the ability of F- to modify it.

PHOTODYNAMIC TREATMENT OF ADENOVIRAL VECTORS WITH VISIBLE LIGHT : AN EASY AND CONVENIENT METHOD FOR VIRAL INACTIVATION

Recombinant adenovirus vectors are popular tools for gene transfer and gene therapy. However biosafety constraints require that all handling of the vectors and vector-containing samples is restricted to dedicated containment laboratories, unless they had undergone a validated virus-inactivation procedure, which decontaminates the samples from any active virus. In this study we evaluated the feasibility of photodynamic treatment (PDT) with visible light to inactivate recombinant adenovirus vectors in biological samples, with minimum associated effects on other biological activities. Several photosensitizers were tested for their capacity to inactivate a model human adenovirus vector, AdCMVLuc, upon illumination. Four photosensitizers (methylene blue (MB), rose bengal (RB), uroporphyrin (UP) and aluminum phthalocynine tetrasulphonate (AlPcS4)) could inactivate the adenovirus, as measured by expression of the luciferase reporter gene and by plaque assay. Of these, MB demonstrated to be the most effective sensitizer in phosphate-buffered saline (PBS), giving >7 log10 inactivation of the adenovirus. DNA isolated from MB- and light-treated virions was inefficient as a template for transcription. Furthermore, Southern blot analysis revealed fragmentation of the viral DNA. Based on its preference for DNA, MB is suited for adenovirus inactivation in blood plasma. Spiking experiments in which AdCMVLuc was added to plasma samples demonstrated a reduction (>4 log10-fold) of reporter gene expression to almost background levels. In contrast to MB, photodynamic treatment with RB, UP or AlPcS4 did not lead to DNA damage. Although alterations of the viral capsid could not be detected, the binding pattern of the particles to target cells was significantly changed. Taken together, our data demonstrate that PDT is an efficient, convenient and useful method for the inactivation of adenovirus vectors in biological samples.

The nucleotide sequence of the transforming early region E1 of adenovirus type 5 DNA

The sequence of the leftmost 11.3% of the non-oncogenic human adenovirus type 5 (Ad5) DNA has been determined. This segment contains the entire early region E1 of the Ad5 genome which has been shown to be involved in in vitro transformation of non-permissive rodent cells (Van der Eb et al., 1980). From the DNA sequence, and from the mRNA sequence data obtained by Perricaudet et al, (1979, 1980) for the E1 mRNAs from the closely related adenovirus type 2 (Ad2), it is possible to predict the primary structure of the polypeptides encoded by this region. The function of these proteins in cell transformation is discussed. From the positions of mapped restriction endonuclease sites and termini of RNA segments in the nucleotide sequence the length of the Ad5 DNA is estimated to be 36.6 kb.

One adenosine deaminase allele in a patient with severe combined immunodeficiency contains a point mutation abolishing enzyme activity.

We have cloned and sequenced an adenosine deaminase (ADA) gene from a patient with severe combined immunodeficiency (SCID) caused by inherited ADA deficiency. Two point mutations were found, resulting in amino acid substitutions at positions 80 (Lys to Arg) and 304 (Leu to Arg) of the protein. Hybridization experiments with synthetic oligonucleotide probes showed that the determined mutations are present in both DNA and RNA from the ADA‐SCID patient. In addition, wild‐type sequences could be detected at the same positions, indicating a compound heterozygosity. Studies with ADA expression clones mutagenized in vitro showed that the mutation at position 304 is responsible for ADA inactivation.