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Introduction. Human cytomegalovirus (Orthoherpesviridae: Herpesvirales: Cytomegalovirus: Cytomegalovirus humanbeta 5) (HCMV) is one of the most commonly detected viruses in recipients of allogeneic hematopoietic stem cell (allo-HSCT) transplants. However, the emergence of resistance to antiviral drugs such as ganciclovir (GCV) poses a challenge in managing these patients. This study aims to investigate the prevalence and impact of mutations in the HCMV UL97 gene associated with resistance to GCV on the course of infection among allo-HSCT patients. Materials and methods. The study examined the association between UL97 mutations and the clinical course of HCMV infection in allo-HSCT patients. Genetic sequencing was performed to identify mutations, and their impact on viral replication and resistance to GCV was assessed. Results and discussion. Six mutations were identified (D490A, T502A, C592G, C592F, E596G, C603W). C592G, C592F, E596G, and C603W are associated with resistance to antiviral drugs, while D490A and T502A described for the first time. When comparing patients with wild-type and those carrying the mutant variant, several parameters of peripheral blood were significantly lower in the former group. The median time to peak viral load following allo-HSCT, duration of viremia, and rate of virological response to high-dose therapy also differed significantly between the two groups. Conclusion. It was shown that approximately one third (4 out of 14) of allogeneic stem cell transplant recipients had mutations associated with resistance to GCV. Patients carrying the mutant variant of HCMV had longer viremia and took longer to achieve a negative virological test result after starting high-dose therapy. Performing genotyping may help make more evidence-based therapeutic decisions.

The review provides information on the mechanisms of the emergence of resistance to antiviral drugs in human viruses from the subfamily Betaherpesvirinae. Data on the principles of action of antiviral drugs and their characteristics are given. The occurrence rates of viral resistance in various groups of patients is described and information about the possible consequences of the emergence of resistance to antiviral drugs is given. Information is provided regarding the virus genes in which mutations occur that lead to viral resistance, and a list of such mutations that have described so far is given. The significance of the study of mutations leading to the resistance of the virus to antiviral drugs for medical practice is discussed.

Introduction. The published and our own data show that CTAG and, to a lesser extent, TCGA tetra-nucleotides have significantly lower concentrations in frequency profiles (FPs) of herpesvirus DNAs compared to other complete, bilaterally symmetrical tetra-nucleotides. The aim of the study is to present a comparative analysis of CTAG and TCGA tetra-nucleotide FPs in viral DNAs. Materials and methods. We have analyzed FPs and other characteristics of the two above tetramers in DNAs of at least one species of viruses of each genus (or each subfamily, if the classification into genera was not available), complying with the size limit requirements (minimum 100,000 base pairs) a total of more than 200 species of viruses. The analysis was performed using the GenBank database. Results. Two groups of characteristics of TCGA and CTAG tetramers have been described. One of them covers the results of the FP analysis for these tetranucleotides in viral DNAs and shows that DNAs with GC:AT 2 are characterized by nCGn FP symmetries while these symmetries are frequently distorted in nTAn FP due to CTAG underrepresentation. The other group of tetramer characteristics demonstrates differences in their FPs in complete viral DNAs and in their genomes (a coding part, which can reach 80% in some studied viruses, thus making the analysis of their DNAs more significant than the analysis of DNAs of cellular live forms) and suggests that these tetramers may have participated in the origin of the universal genetic code. Discussion. Assumedly, the genetic code started evolving amid C+G prevailing in "pre-code" DNA polymers; then the initial code forms evolved further to their final structure where TCGA and CTAG tetramers hold a central position, encapsulating the previous stages of this evolution. The nCGn FP symmetries typical of the "complete" DNA of Herpes simplex viruses disappear in the sequence of the second codon letters of the genome of these viruses, implying that their functions differ from functions of other letters and emphasizing the reasonableness of presenting the genetic code as a calligram where the second line is not symmetrical.

Introduction. Herpesvirus DNAs (about 90% of the total genomic sequences of the Herpesvirales family presented in GenBank) contain at a minimum concentration one of the two tetranucleotides, CTAG or TCGA. The “underrepresentation” of CTAG was previously observed only in the DNA of some bacteria and phages. The aim of the study was the further analysis of the formal characteristics of herpesvirus DNA, as well as their comparison with the density of the virus/host DNA microhomology and with the genomic macrostructure of herpes viruses.Materials and methods. Twenty strains and isolates of each of the five types of human herpes viruses (HHV1, HHV2, HHV3, HHV4, HHV5), 10 strains of HHV8, 5 strains of HHV6A, 4 strains of HHV6B and 3 strains of HHV7 were analyzed. GenBank tools were used to determine the frequency of tetranucleotides, and human DNA fragments with size matched herpesvirus DNA were used for comparison.Results. Minimum CTAG concentration in DNA of herpes viruses is mainly characteristic of two- and singlesegment genomes with direct or inverted terminal repeats (classes A,D,E), while the minimum TCGA density is characteristic mainly for DNA that is significantly less structured (classes B,C,F). By increasing CTAG density, human herpes viruses form a sequence close to the sequence of increasing the homology density of 20 nt with human DNA, which also correlates with the macrostructure of DNA. A parallel of this minimization with the DNA structure of herpes viruses or with their belonging to one or another subfamily — as well as the context of the “minimal” CpG (that is, TCGA) — is not noted in the literature. Although herpesvirus DNA is quite large (125– 295 Kb), some of them (for example, HHV4, HHV5 and HHV7 DNA) show noticeable deviations from the second DNA parity rule, and can thus serve as a component of the molecular signature.The Discussion suggests possible hypotheses for the origin of some of the observed phenomena.

We describe a novel microarray-based approach for simultaneous identification and quantification of human immunodeficiency virus type 1 (HIV-1) and hepatitis B and C viruses (HBV and HCV) in donor plasma specimens. The method is based on multiplex real-time RT-PCR performed within the microarray hydrogel pads. Double-stranded amplification products are simultaneously detected using nonspecific SYBR Green I dye due to the reaction run in separate pads bearing 5′-immobilized specific primers. Both the sensitivity and specificity of the assay, based on 132 blood specimens analyzed, were 100% (56, 26, and 8 specimens were seropositive to HBV, HCV, and HIV-1, respectively; 22 were positive to both HIV-1 and HCV, and 2 positive to all three viruses; 18 samples were pathogen-negative). The dynamic range of the quantitative analysis covered a six-order interval ranging from 100 to 106 genome equivalents per assay. The 95% detection limits were 14 gEq for HIV-1, 10 gEq (1.7 IU) for HBV, and 15 gEq (7.5 IU) for HCV per assay. The proposed approach is considered to be versatile and could be adapted for simultaneous identification and quantification of numerous genetic targets.