Human enteric adenovirus type 41 binding to HEp-2 cells is specific

Genetic organization, size, and complete sequence of early region 3 genes of human adenovirus type 41

The complete nucleotide and predicted amino acid sequences for open reading frames (ORFs) of the human adenovirus type 41 (Ad41) early region 3 (E3) gene have been determined. The sequence of the Ad41 E3 gene (map units 74 to 83.9) consists of 3,373 nucleotides and has one TATA box and two polyadenylation signals (AATAAA). Analysis of the nucleotide sequence reveals that the E3 gene can encode six ORFs, designated RL1 to RL6. These are all expressed at the mRNA level, as determined by reverse transcription-PCR analysis of AD41-infected cell RNA. When compared with known E3 sequences of most other human adenoviruses deposited in GenBank, the sequences of RL1 to RL3 were found to be unique to subgroup F adenoviruses (Ad40 and Ad41). They encode putative proteins of 173 amino acids (19.4 kDa) and 276 amino acids (31.6 kDa) in one reading frame as well as a 59- amino-acid (6.7 kDa) protein in an overlapping reading frame. RL4 encodes a 90-amino-acid protein (10.1 kDa) with 40% homology to the Ad2 E3 10.4-kDa protein, which induces degradation of the epidermal growth factor receptor and functions together with the Ad2 E3 14.5-kDa protein to protect mouse cell lines against lysis. RL5 encodes a protein of 107 amino acid residues (12.3 kDa) and is analogous to the Ad E3 14.5-kDa protein. RL6 codes for a protein of 122 amino acids (14.7 kDa) that is analogous to the Ad2 14.7-kDa protein, which functions to protect Ad-infected cells from tumor necrosis factor-induced cytolysis. This finding of three unique (RL1 to RL3) E3 gene ORFs may explain why subgroup F adenoviruses differ substantially from other human adenoviruses in their host range; i.e., they replicate predominantly in the host's gastrointestinal rather than respiratory tract. A recent phylogenetic study that compared subgroup F Ad40 DNA sequences with representatives of subgroups B (Ad3), C (Ad2), and E (Ad4) reached a similar conclusion about the uniqueness of RL1 and RL2.

Fast and high-affinity binding of B-lymphotropic papovavirus to human B-lymphoma cell lines

Binding of B-lymphotropic papovavirus (LPV) to host cells differing in susceptibility to viral infection was determined by a newly established, direct, nonradioactive virus binding assay, which allows quantitative description of the binding characteristics by receptor saturation and Scatchard analysis. LPV binding to the highly susceptible human B-lymphoma cell line BJA-B K88 is specific, saturable, and noncooperative. Binding occurs very fast, with an association rate constant (k1) of 6.7 x 10(7) M-1s-1, and is of high affinity, with a dissociation constant (Kd) of 2.9 x 10(-12) M; and the virus-receptor complex is stable, with a half life of 70 min. The binding affinities of receptors on four other highly, moderately, or weakly susceptible human B-lymphoma cell lines were similar, with up to twofold variation around a mean Kd value of 3 x 10(-12) M, suggesting the presence of the same LPV receptor on all of these cell lines. This view is further supported by the finding that in all cases a terminal sialic acid is necessary for LPV binding. Tunicamycin has been shown to drastically induce LPV susceptibility and LPV binding in weakly and moderately susceptible B-lymphoma cell lines (O.T. Keppler, M. Herrmann, M. Oppenländer, W. Meschede, and M. Pawlita, J. Virol. 68:6933-6939, 1994). The hypothesis that the constitutively expressed and tunicamycin-induced LPV receptors are identical is strengthened by our finding that both receptor types displayed the same high affinity. LPV susceptibility of different B-lymphoma cell lines was correlated with receptor number but not with receptor affinity. The numbers of receptors per cell on highly and moderately susceptible cell lines ranged from 2,000 to 400 and were directly proportional to LPV susceptibility. This indicates that the number of high-affinity receptors per cell is a key regulating factor for the LPV host range.

Pharmacokinetics of adenoviral vector-mediated gene delivery to vascular smooth muscle cells: modulation by poloxamer 407 and implications for cardiovascular gene therapy

Regional in vivo delivery of therapeutic genes to the cardiovascular system at sites of localized vascular disease is feasible by catheter-mediated delivery of recombinant adenoviral vectors. Vascular smooth muscle cell (SMC) proliferation, which follows angioplasty and contributes to restenosis, is one process that may be amenable to such a gene therapy strategy. The clinical utility of localized delivery strategies such as this critically depends upon successful gene transfer to sufficient numbers of vascular cells, locally, within a clinically acceptable time period. Relatively limited information is available concerning the kinetics of gene transfer by first-generation, replication-deficient, recombinant adenovirus (Av1) vectors. In this context, we evaluated the pharmacokinetics of adenoviral vector-mediated gene delivery to vascular SMC using an Av1 reporter vector (Av1LacZ4) expressing a nuclear-targeted beta-galactosidase (beta-Gal) reporter. Bovine aortic SMC were exposed to Av1LacZ4 for various times at a range of concentrations and multiplicities of infection (MOI). After exposure, cells were washed and evaluated for transduction at 48 hr by X-Gal staining. Transduction occurred with a rate constant typically determined in the range of 10(-10) to 10(-11) events.ml/cell.virion.min. The rate of transduction was directly dependent on virion concentration, but not substantially on the virion-to-cell ratio. Relatively low fractions of the total input vector were found to be consumed, even after prolonged adsorption times. We hypothesized that the cellular transduction rate (and thus overall efficiency) would be improved by agents that could maintain a prolonged, high pericellular vector concentration. To evaluate this, cells were exposed to the vector in the presence of 15 grams/dl poloxamer 407, a viscous biocompatibile polyol, for various times followed by washout and evaluation as described above. Both cells and vector remained viable under these conditions, and poloxamer was found to increase the apparent transduction rate 10-fold or more (1-5 x 10(-9) transduction events.ml/cell.virion.min), with remarkable increases in numbers of cells transduced even after brief exposure periods. These observations demonstrate that the pharmacokinetics of adenoviral-mediated gene delivery to vascular SMC can be modulated by agents such as poloxamer 407, which may improve gene delivery by maintaining high pericellular concentrations of vector. Such modulation may permit achievement of desired levels of gene transfer while requiring lower total viral dosage and exposure time, and in turn may have important implications for in vivo gene delivery to vascular tissues.

Human adenovirus type 41 contains two fibers

DNA sequencing of the subgroup F human adenovirus serotype 41 (TAK, Ad41) fiber gene revealed the presence of two adjacent open reading frames encoding information for proteins with molecular weights of 60.6 kDa and 41.4 kDa (Pieniazek, et al; Nucleic Acids Res. 18: p. 1901, 1990). In this paper, various approaches were used to characterize the two proteins and determine whether both fibers were expressed in infected cells as well as on viral particles. We initially used a reverse transcriptase-polymerase chain reaction with primers for the short and long fiber genes to amplify mRNA from Ad41 infected HEp-2 cells at 48 h post-infection. Two distinct DNA bands; one slightly larger than 1.1 kbp and the other at about 1.7 kbp were identified. Second, we used polyclonal anti-Ad41 virion and monoclonal anti-Ad5 fiber antibodies to demonstrate that at both 24 and 36 h post-infection, Ad41 expressed two fiber proteins of the expected size. Specifically, by SDS-PAGE, one fiber (short) had a molecular weight of 40 kDa, while the other (long) had a molecular weight of 60 kDa. Third, by electron microscopy, two sizes of fibers were released from CsCl purified virions, both having a characteristic adenovirus morphology, with a knob at one end. The long fiber measured 315A in length and the short fiber was 250A long. These measurements are consistent with the two Ad41 fibers being encoded by the above open reading frames. We also performed a computer search to compare fiber sequences from other human adenovirus serotypes with that of the Ad41 short and long fiber proteins. The primary structure of both Ad41 fibers were found to be similar in that they contained tail, shaft and knob regions. Further, the tail region of both fibers (amino acids 1-42) showed a 74% overall homology to each other and contained the Ad conserved sequence NH2-F-N-P-V-Y-P-Y-COOH. An interesting difference, however, was observed in the shaft region where the long fiber (amino acids 43-389) had twenty-two 16-amino acid repeat motifs, while the short fiber (amino acids 43-233) had only twelve. Finally, we noted that the long fiber knob region was about 15% longer than that of the short fiber, and showed little overall homology. In conclusion, human adenovirus subgroup F (type 41) virions appear to differ from those of all other human adenoviruses (subgenera A-E) in that they contain two fiber genes and correspondingly, two different sized fibers.(ABSTRACT TRUNCATED AT 400 WORDS)