Symmetry types, systems and their multiplicity in the structure of adenovirus capsid. II. Rotational facet groups of five-, three- and two-fold symmetry axes.

The icosahedral adenovirus capsid has three rotational symmetry axes of different types. The six five-fold, ten three-fold and the fifteen two-fold axes have two superficial points each, altogether 62. The axes determine the number and location of the identical rotational facet groups and that during the different rotational phases which other regular facets and with what multiplicity shall be covered by them. The number of rotational facets of the five-, three- and two-fold rotational symmetry axes is 4, 6.66 and 10, respectively. In all the three cases, there are two kinds of possible arrangements of the facets. During the rotation--when the facets of the facet group placed on one by one to the neighbouring identical facet groups--at the five-fold axes, the facets of the rotational facet group get into cover position 12 times with all the 20 regular capsid facets, 20 times at the three-fold axes, and 30 times at the two-fold axes in a way that a different facet combination (facet hit) falls to every facet, and the original symmetry is not disturbed. After all, this means 240, 400 and 600 facet combinations, i.e. multiplicity in case of five-, three- and two-fold symmetry axes respectively, and these numbers correspond with that of the theoretically possible variations. The same results can be calculated by multiplying the number of real rotations of the capsid bringing the body into itself, i.e. the number 60 with the number of facets contributing to the five-, three- and two-fold rotational phases. The other way of the determination of multiplicity takes into account that all the facet groups of the capsid rotate simultaneously during all the rotational phases, and this multiplies the number of multiplicity with the number of the rotational types five-, three- and two-fold which result in one and the same multiplicity number in the case of five-, three- and two-fold symmetry, alike 1200. Perpendicular to the five-fold symmetry axes with the line of intersection drawn horizontally in the middle along the 6 geodetic ribbon like motifs a regular decagonal intersection forms and the capsid can be cut into two equal parts, in which the polypeptides show a 72 degree rotation from each other, but with a proper rotation the polypeptides get into a congruent position, which means 300 or 600 specific facet combinations. The capsid similar to the icosahedron has also 15 virtual mirror planes which divide the capsid into two, identically arranged halves, forming six right angle triangles on each facet, altogether 120 smaller rectangular so-called Mobius-triangles on the surface. In the three-fold symmetry axis of the facets, these triangles in two separate groups of three can be rotated symmetrically with 120 degrees according to the orientation of the polypeptide subunits in a way that the hexon and other polypeptides too nearly cover each other. Consequently, the adenovirus capsid is a symmetrically arranged body in which several various symmetry types and symmetry systems can be found and their structural symmetry elements exist simultaneously and covering each other. The icosahedral symmetry types and systems are valid and functional simultaneously and in parallel with great multiplicity, but the existence of more than 1500 structural elements in several depth levels, their order of location and distribution make the symmetry of the capsid richer and more complex.

Symmetry types, systems and their multiplicity in the structure of adenovirus capsid. I. Symmetry networks and general symmetry motifs.

Each of the more than 1500 polypeptide molecules of 7 different types building up the adenovirus capsid--probably even those of their amino-acids--are in symmetrical location. Every kind of polypeptide forms a separately also symmetrical network in the capsid distributed according to their functions in the inner and outer side and the inside of the facets and edges, but always in compliance with the icosahedral symmetry. Therefore, each different polypeptide also means a general symmetry motif in the capsid in its own symmetry network. Hexons can be considered as general symmetry motifs in some special association that is because of their environmental position four kinds of hexon types can be found, which are on every facet, next to one another, like three identical groups of four (GOF) according to the three-fold rotational symmetry. Two polypeptides of a peripentonal hexon of each GOF orient toward the penton and the third toward the other penton located further on the same edge. There are two versions of the arrangement of the GOFs: the hexons surround either a polypeptide IX or a polypeptide IlIa. The two versions of GOFs on 20 facets symmetrically recurring 60 times as general hexon symmetry motifs form the capsid in combination with the network of other polypeptides. Ideally, the surface of the hexon trimer shows three-fold rotational and three-fold reflexional symmetries. In the arrangement of hexons in the facets the translational, rotational, horizontal and vertical reflexional symmetry and the combination of these, as well as the glide reflexion and the antisymmetry can be found. Each hexon has six nearest neighbours and every hexon takes part in the construction of three hexon rows. Every facet and every vertex made up of five facets has an antisymmetrical pair located on the opposite side of the capsid. Every triangular facet participates in forming three vertices and every facet has three nearest neighbouring facets. In the facets, the polypeptide subunits of polypeptide IX centered GOF hexons have identical counter-clockwise orientation but the orientation of the neighbouring facets is always opposite compared to each other. On the five-fold symmetry axis, any facet can be "turned on" to the adjacent facet or "rotated" to all the others and will take the symmetry and orientation of the facet it got turned on or rotated to. Thus, every facet together with the polypeptides attached to it shows a twenty-fold symmetry and multiplicity. An other type of symmetry and multiplicity in the capsid is that perpendicular to the 6 five-fold rotation axes run a geodetic (equatorial) ribbon like motif (superfieces) altogether six made up of 10 x 10 triangular facets and bent ten-times with an angle of 36 degrees. A triangular facet participates in forming three ribbon-like motifs, which intersect with each other on the given facet, but the same three motifs intersect repeatedly only on the antisymmetrically located facet.

Screening adenoviruses in stool samples: evaluation of a genus-specific monoclonal antibody based enzyme immunoassay.

To screen fecal samples for adenovirus antigens a genus-specific monoclonal antibody based enzyme immunoassay was developed. In a comparative analysis with commercial latex agglutination test, high sensitivity was demonstrated. The assay did not detect other viruses usually found in faeces suggesting its specificity. One hundred and eighty stool samples collected in Baranya County were tested and 13 (7.2%) of them showed reactivity. The application of our immunoassay combined with other, more sophisticated methods may help us to determine the serotype specificity of these adenovirus isolates and assess the importance of adenoviruses in viral gastroenteritis.

The endosomal epsilon-coatomer protein is involved in human adenovirus type 5 internalisation.

The effects of bafilomycin A1 and of the reduced level of endosomal epsilon-COP (coatomer protein) on the infectivity of human adenovirus type 5 were investigated in Coxsackie adenovirus receptor- (CAR-) transfected Chinese hamster ovary (CHO) cells. The endosomal proton pump inhibitor bafilomycin A1 was able to cause only partial inhibition. Using Id1F cells (an epsilon-COP thermosensitive mutant CHO cell line) the reduction of epsilon-COP level also had partial inhibitory effect. Based on these results and comparing them to existing models of the adenovirus entry, we propose a refined model in which there are two pathways of adenoviral entry: the first one involves the epsilon-COP as the downstream effector of the acidification and can be blocked by bafilomycin A1 and the second one is a pH-independent pathway.

Effect of fluoride on cariogenic oral microorganisms (an in vitro study).

The effect of sodium fluoride and sodium monofluorophosphate at concentrations of 1, 5, 10, 50, 100 and 1000 mg/l in phosphate buffer (pH 6.5) as well as in UHT milk were studied on cultures and suspensions of Streptococcus mutans, Lactobacillus acidophilus and Candida albicans. Using serial tenfold dilutions up to 10(-7) of 24-48 hour cultures, a subsequent 0, 60 and 120 min incubation caused no decrease in the number of CFUs. Growth kinetic studies in the Bioscreen biophotometer (Labsystem, Finland) revealed that sodium fluoride in different concentrations (from 0.875 mg/l up to 500 mg/l) influenced the growth dynamics of S. mutans and C. albicans: the exponential phase flattened out at the highest fluoride concentrations (500 mg/l) present in the growth media. The lag phase of C. albicans became longer. The results of these experiments indicate that sodium fluoride administered at higher concentrations than the usual caries preventive dosage made the generation time of cariogenic oral bacteria and fungi longer, slowing down their multiplication.

[Adenovirus vectors and their clinical application in gene therapy]. / Adenovírus vektorok és klinikai alkalmazásuk a génterápiában.

The potential therapeutic application of the gene transfer technology with adenovirus vectors seems to be enormous. Adenovirus vectors offer several advantages over other vectors, but several important limitations of adenovirus mediated gene transfer are also known. Great number of studies in inherited diseases and in different cancer therapy clinical trials have provided information of critical importance for design of efficient clinical protocols. Clinical trials have been extended to the treatment of many other diseases, too. There are about thirty currently active gene therapy protocols for the treatment only of HIV-1 infection in the USA. These programs aim to confer protective immunity against HIV-1 transmission to individuals who are in risk of infection, to develop preventive or therapeutic vaccines for patients with AIDS and other infectious diseases. Gene therapy represents one of the most important developments in oncology, however, before this can be realised as standard treatment the technical problems of gene delivery and higher safety must be overcome. The early--first and second generation--adenovirus vectors are now likely to be phased out for most diseases, and further experiments seem to be necessary. It might be change to the third generation or other, more modern vector application in clinical trials, as the helper dependent vectors. Almost all transcriptional unit is removed from the DNA of these vectors ("gutless vectors"), therefore they cannot reproduce, give higher gene expression and far less inflammatory. Despite the latest achievement reported in vector design it is not possible to predict yet to what extent and when gene therapy will be effective.

Alternate adenovirus type-pairs for a possible circumvention of host immune response to recombinant adenovirus vectors.

With the help of monoclonal antibodies the existence of at least 18 different earlier not known intertype (IT) specific epitopes were demonstrated in different numbers and combinations on the hexons of different adenovirus serotypes. The IT specific epitopes play an important role in the experimental gene therapy and in the recombinant adenovirus vaccination because of the harmful immune response of the recipient organisms directed against the many different epitopes of the adenovirus vector. For the elimination of harmful effect the authors suggest the use of multiple vectors, each prepared from different adenovirus serotypes showing the loosest antigenic relationship to each other. The vectors would be used sequentially when second or multiple administration is needed. For this purpose the authors determined and described 31 such adenovirus type-pairs, which are probably the best alternates for sequential use in experimental gene therapy.

Recombinant adenovirus vectors for gene therapy and clinical trials.

In the last decade adenovirus (AdV) vectors have emerged as promising technology in gene therapy. They have been used for genetic modification of a variety of somatic cells in vitro and in vivo. They have been widely used as gene delivery vectors in experiments both with curative and preventive purposes. AdV vectors have been used in the experimental and in some extent in the clinical gene therapy of a variety of cancers. The combination of recombinant AdV technology with chemotherapy (pro drug system) seems to be promising, too. AdV vectors offer several advantages over other vectors. Replication defective vectors can be produced in very high titers (10(11) pfu/ml) thus allowing a substantially greater efficiency of direct gene transfer; they have the capacity to infect both replicating and nonreplicating (quiescent) cells from a variety of tissues and species. Several important limitations of adenovirus mediated gene transfer are also known, such as the relatively short-term (transient) expression of foreign genes, induction of the host humoral and cellular immune response to viral proteins and viral infected cells, which may substantially inhibit the effect of repeated treatment with AdV vectors, the limited cloning capacity and the lack of target cell specificity. However, the well-understood structure, molecular biology and host cell interactions of AdV-s offer some potential solutions to these limitations.

Serological evidence of adenovirus infection in cats.

The widespread presence of adenoviruses in various species makes it probable that infection and the carrier state also exist in cats. On the basis of these considerations, investigations were carried out to find antibodies against adenovirus in sera from different cat populations kept under different conditions. For the antibody detection, purified adenovirus was used in an indirect ELISA. To produce positive serum, SPF cats were immunized with a purified hexon preparation. Altogether 632 field sera of different origin were tested. Among field samples, adenovirus seropositivity varied between 10-26%.

Taguchi optimisation of ELISA procedures.

We propose a new method in the field of ELISA optimization using an experimental design called the Taguchi method. This can be used to compare the net effects of different conditions which can be both qualitative and quantitative in nature. The method reduces the effects of the interactions of the optimized variables making it possible to access the optimum conditions even in cases where there are large interactions between the variables of the assay. Furthermore, the proposed special assignment of factors makes it possible to calculate the biochemical parameters of the ELISA procedure carried out under optimum conditions. Thus, the calibration curve, the sensitivity of the optimum assay, the intra-assay and inter-assay variability can be estimated. The method is fast, accessing the results in one step, compared to the traditional, time-consuming 'one-step-at-a-time' method. We exemplify the procedure with a method to optimize the detection of ScFv (single chain fragment of variable) phages by ELISA. All the necessary calculations can be carried out by a spreadsheet program without any special statistical knowledge.

Characterization of intertype specific epitopes on adenovirus hexons.

The specification and differentiation of eighteen intertype specific (IT) epitopes of adenovirus hexons defined by monoclonal antibodies are given by two groups of hexon types: on which they are and on which they are not present. The close specificity relationship among some groups of epitopes determined by pairwise analysis according to their presence on the hexon types indicate that they could be continuous (sequential), overlapping or discontinuous (topographic) epitopes. Based on the identification of the hydrophilic regions and the localization of beta-turns sixteen IT epitope sites were predicted on human adenovirus (HAdV) type 2 and nineteen on HAdV-41 hexon's amino acid (aa) sequences beside the type and genus specific ones. The 16 predicted IT epitopes on HAdV-2 hexon show good coincidency with the 14 IT epitopes demonstrated with monoclonal antibodies (MAbs) on this hexon type. The predicted number of common epitopes between HAdV types 2 and 41 also corresponds well with the eight IT epitopes determined by MAbs, but the 17 predicted non-common epitopes indicate the possibility of the existence of more epitopes on these hexon types. The location of the predicted epitopes of HAdV-2 were determined by alignment of their sequence numbers on the three dimensional ribbon representation of the hexon subunit. Most of the predicted IT epitopes were found between the type and genus specific epitopes i.e. in the "upper" regions of pedestal domains P1 and P2 orientated toward the virion surface and in the "lower" part of loop 1 region orientated inside the virion. Two peptides representing potential IT epitopes were synthesized corresponding to residues 309-320 from the "lower" part of loop 1 and 399-408 from the "upper" part of P1 region of HAdV-2 hexon. Antibodies raised against the peptide-carrier conjugates recognized different purified native hexon types in ELISA.

Fast method to remove UV absorbing agarose gel contamination from DNA samples.

Agarose gel electrophoresis and subsequent purification of DNA bands from the agarose gel is a widely used molecular biological method. There are different methods to achieve this goal, however they have different advantages and disadvantages. One major problem is the presence of different contaminants in the final sample. We developed a method which is effective in removal of the agarose contaminants.

Interrelationship of viruses and cells. The cytopathic property of adenoviruses.

The application of in vitro cell cultures in virus research has a great importance in studies on the interaction between virus and cell. A great number of the viruses causes characteristic degeneration in the infected cells, well visible in the light-microscope, and due to their cytopathic effect the existence of viruses became directly detectable. Based on characteristic changes even the serological type of virus can be determined in some cases. Thus the multilateral examination of the interaction between virus and host cell has immense importance both in virus research and in therapy.

Molecular biological characterization of adenovirus DNA.

The agarose gel electrophoresis of DNA, the ethidium bromide fluorescence detection of DNA fragments and restriction endonucleases were discovered at the end of the '60s. The methodological progress enabled institutions equipped with less sophisticated technology to achieve also unique experimental and scientific results in the field of viral DNA research. The team working on virus DNA within the adenovirus research group has constructed several new restriction endonuclease maps of the genomes of human and animal adenoviruses; contributed to the methodology of the determination of specific endonuclease sites, and genome polarity; discovered new restriction endonucleases, adenovirus subtypes, new empty capsid, and genome subpopulations; participated in cooperations leading to novel, although hypothetical approaches in AIDS therapy, taxonomic definition of viruses, and evolutionary origins of adenovirus replication and encapsidation strategy.