Marek’s disease virus is ubiquitous and can harm not only poultry, but also be oncogenic for humans. VBM and malignant tumors induced by them are a convenient and accessible natural model for studying herpesvirus-associated carcinogenesis. To date, according to our observations, there are additional risks of human infection with the Marek’s disease virus - the disease began to appear in broiler chickens 30 days and older, i.e. contact with poultry meat carries a risk of infection. In addition, COVID-19 disease may be accompanied by folic acid deficiency, i.e. a violation of the folate cycle in humans, which increases the risk of manifestation of diseases associated with DNA viruses, since a violation of the folate cycle can reduce the activity of DNA methylation, incl. viral DNA. Methylation is carried out enzymatically in the first minutes after DNA replication, i.e. postreplicatively. Since the DNA nucleotide sequence does not change, methylation is essentially an epigenetic event. We have studied the relationship between the methylation of promoters of the Marek’s disease virus and the copy number of the virus. The assessment of the presence or absence of methylation, as well as partial methylation, was carried out on the basis of identifying the difference between the threshold cycles dC(t). The presence of unmethylated sites included in the studied promoter sequence was detected on the basis of the ability of methylsensitive restrictases AciI and GlaI. A correlation was found between the concentration of genomic DNA of the Marek’s disease virus serotype 1 strain CVI 988 in cell culture and the presence of demethylated CpG islands in the composition of promoters located at position 9413-9865 bp. and 127943 - 128193 b.p. genomic DNA of the virus. The data obtained make it possible to explain the mechanism of the increase in the pathogenicity of herpesvirus infections under conditions of a decrease in the activity of viral DNA methylation in the body.

Due to the progressive growth of the bacteria caused by the widespread use of antibiotics, treatment of streptococcosis is becoming increasingly difficult. Reliable vaccination against Streptococcus suis is necessary. Modern molecular diagnostic and genetic engineering capabilities create prospects for direct cloning of the protective epitopes of the Lmb gene of the local S. suis strain into the proposed delivery system of the pig immune system antigen. Among oral vaccine carriers, Bacillus subtilis is recognized as a relatively environmentally friendly carrier with an efficient protein secretion system and adaptive metabolism capable of spore production under relatively harsh conditions. This spore property can be used to increase the stability and reusability of vaccines. The possibility of using the protective Lmb epitopes of S. suis in B. subtilis as a carrier of an oral recombinant vaccine against Streptococcus suis was studied. The nucleotide sequences of S. suis were obtained from the GenBank database after a preliminary analysis of literature data on the known protective antigens of S. suis of various serotypes. Nucleotide sequence analysis was performed using Unipro UGENE v. 43.0. The Immune Epitope Database (IEDB) was used to search for T (CTL and Th) and B dependent epitopes of the Lmb gene. A computer-designed vaccine in which localization of CTL, B, and Th epitopes is predicted is described. The results of cloning the sequence of the antigenically active epitope of the S. suis Lmb protein in B. subtilis for subsequent oral administration and study of changes in immunological reactions and adverse reactions in animals are described. The possibility to clone the epitopes of recombinant S. suis Lmb protein into the pBE-S polylinker vector was revealed. In the long term, it seems possible to create a new inexpensive and easy-to-use vaccine against S. suis that does not require injection.