[Development and preservation of specific T-cell immunity after COVID-19 or vaccination against this infection].

Aim evaluation of specific T-cell immunity against SARS-CoV-2 in primary and secondary response to virus antigens by screening method. MATERIALS AND METHODS: Patients were tested 11.5 months after COVID-19 and 610 months before and after vaccination. Healthy volunteers were screened before, 26 times during the vaccination course, and 68 months after revaccination with the Sputnik V vaccine. IgG and IgM antibodies to SARS-CoV-2 were detected by ELISA using commercially available kits (Vector-Best, Russia). Antigenic (AG) activation of T cells in the fraction of bloods mononuclear cells was assessed by IFN- production after AG stimulation in the wells of plates from ELISA kits intended for detection of antibodies against SARS-CoV-2. Data were processed by MS Excel and Statistica 10.0 software. RESULTS: AG-specific T cells were detected in 88.5% of vaccinated healthy volunteers, half of whom were found to have T cells appearing earlier than antibodies to AG. After 6-8 months, the level of AG activation decreases. Following the revaccination, the level of AG activation of memory T cells in vitro increases within six months in 76.9100.0% of vaccinated subjects. On the contrary, after COVID-19, 86.7% of individuals had in their blood the AG-specific T cells with high activity at the time of vaccination. The activity of T cells recognizing the RBD domain of the SARS-CoV-2 S protein and the proportion of individuals who had these cells in their blood increased after the vaccination of reconvalescents. CONCLUSION: T-cell immunity against SARS-CoV-2 antigens has been shown to persist for 6 months after illness. In vaccinated individuals without history of COVID-19, such duration of the preservation of AG-specific T cells in blood was only achieved after the revaccination.

Composition of Bacteriophages for Therapeutic and Prophylactic Use in Monkeys.

Keeping rhesus monkeys as laboratory animals requires timely prevention and treatment of infections, including diseases of bacterial etiology. Based on our own studies of the microflora of healthy and sick monkeys, as well as analysis of published reports, we identified clinically significant representatives of pathogenic and opportunistic bacteria: E. coli, Staphylococcus aureus, Klebsiella spp., Proteus spp. The isolates of these bacterial species and genera circulating in monkeys kept in the enclosure were isolated, four virulent bacteriophage strains with a wide spectrum of lytic activity against these isolates were selected and newly isolated. The composition based on virulent bacteriophage strains was tested on monkeys with assessment of its safety and its dynamics of detection of phage-specific DNA.

Features of the Humoral Response to Infection, Vaccination, and Revaccination during COVID-19.

IgM and IgG antibodies to the SARS-CoV-2 virus are detected in subjects who have recovered from COVID-19; IgM antibodies persist in a 1/3 of infected subjects up to 12 months from the moment of the disease, while IgG antibodies are present in the vast majority of cases (97%; medium and high levels antibodies were registered in 85% of cases). By the 12th month, 40% of those who recovered still have a very high level of IgG antibodies to the S-protein (>500 BAU/ml). In the feces, urine, and blood serum of patients with long-term persistent IgM antibodies, no coronavirus antigens were detected. After vaccination with the Gam-COVID-Vac vaccine, IgG antibodies to the S-protein are detected in 100% of cases and remain at a high level for 4 months, by the 5-6th month, the level of antibodies decreases. During revaccination, the level of IgG antibodies to S-protein reaches high values earlier than during primary vaccination, and remains high for 4 months (observation period). The blood sera of recovered and vaccinated patients have a high virus-neutralizing activity (at least 1:80), while its level is somewhat higher in recovered patients.

Dynamics of Antibodies to Various Antigens of the SARS-CoV-2 Coronavirus in Patients with Confirmed COVID-19 Infection.

The presence of IgG and IgM antibodies in the venous blood of 76 patients with confirmed COVID-19 infection was determined by ELISA using Russian test systems. Different levels of IgM antibodies to N-protein and receptor binding domain of the Spike protein (RBD) were revealed. The dynamics of IgG antibodies to the whole virion antigen and recombinant antigens showed high values on weeks 4-5 of the disease. The level of IgG antibodies to Nprotein remained low throughout the observation period. The characteristic dynamics of IgG measured using test systems with sorbed whole virion or recombinant spike proteins reflects the duration of the disease.

Determination of Bactericidal Activity Spectrum of Recombinant Endolysins of ECD7, Am24, Ap22, Si3, and St11 Bacteriophages.

The bactericidal activity of recombinant endolysins LysECD7, LysAm24, LysAp22, LysSi3 and LysSt11 was assayed in multidrug resistant strains (n=120) of Salmonella enterica, E. coli, Acinetobacter baumannii, Enterobacter spp., Pseudomonas aeruginosa, Klebsiella pneumoniae, and Campylobacter jejuni. The assay showed that the recombinant endolysins had a wide spectrum of bactericidal activity compared to endolysins of their progenitor phages. Among examined endolysins, we selected the active pharmaceutical substances with broad spectrum of bactericidal activity. Most strains were sensitive to LysECD7 (70.7%), LysAm24 (65%), and LysAp22 (58.6%), which seems to be promising causative agents for the development of finished dosage form.

Analysis of the Pharmacokinetics of Suppository Forms of Bacteriophages.

Pharmacokinetics of suppository forms of bacteriophages was studied on male Chinchilla rabbits. Suppositories with various composition of bacteriophages were administered once per rectum to rabbits, and the presence of phage particles was estimated in the blood, urine, and feces over 24 h. Pharmacokinetic study showed that the phages were detected in the blood, urine, and feces at various terms of the experiment irrespective of the size of viral particles, which confirmed the possibility of their systemic effects after rectal administration. Thus, the use of suppository form of bacteriophages can ensure the presence of phage particles even in infection foci that cannot directly contact with the preparation.

[Approaches to the estimation of some parameters of humoral and cellular immune response to bacteriophages.]

The aim of the study was to develop some approaches to evaluate the basic parameters of the humoral and cellular immune response to a bacteriophage, taking into account the multifactorial aspects of its interaction with both the pathogen and the macroorganism. The necessary reagents were obtained and a line of diagnostic ELISA test systems was designed to allow semi-quantitative assessment of the anti-bacteriophage IgG-antibody level in serum or other biological human fluids, as well as in preparations obtained from human blood. The need for neutralization reaction to determine the effect of detected antibodies on phage activity against a target bacterium has been proven. Testing the approaches used in the investigation of patients' blood sera showed that antibodies to bacteriophages synthesized during phage therapy are not always neutralizing. Also approaches have been developed to evaluate cell immunity reactions to bacteriophage namely to identify T-lymphocytes (T-helpers and cytotoxic lymphocytes) that can be activated in the presence of the phage under study (by expressing the early activation marker (CD69) and by the ability to produce IFNγ). Approbation of the technique in the study of lymphcytes in patients during phage therapy showed the presence of activated cells by both the CD69 expression and IFNγ production, the dynamics of which depended on the timing and frequency of therapy. The appearance of neutralizing anti-phage antibodies and corresponding activated T-lymphocytes should be taken into account in phage therapy, the effectiveness of which can directly depend not only on the activity of the phage against the target bacterium, but also on the response of the patient's immune system to the bacteriophage.

[COMPLEX IMMUNOGLOBULIN PREPARATION FOR THERAPY OF PERTUSSIS IN YOUNG CHILDREN].

AIM: Study the possibility of inclusion of complex immunoglobulin preparation (CIP) pos- sessing specific activity against pertussis exotoxins into complex therapy of pertussis infection in young children. MATERIALS AND METHODS: -2 groups of children with.pertussis younger than 3 years were examined. The main group (50 individuals) received CIPper os - 1 dose 1 - 2 times per day for 5 days, comparison group (34 children) received only basic therapy. Evaluation of clinical effectiveness of CIP was carried out, the content of anti-pertussis class G antibodies and total IgE in patients were studied. RESULTS: A good clinical effectiveness of the preparation was shown, as well as immune modulating activity against humoral immune response to pertussis infection. CONCLUSION: The detected positive effect of CIP on pertussis -course in children has indicated a principally novel use of this per oral drug form.

Phagebiotics in treatment and prophylaxis of healthcare-associated infections.

We have developed a phagebiotic composition using 8 virulent bacteriophages (2 strains of each species) which are able to lyse Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus. The unique character of the developed composition is ensured by particular properties of each bacteriophage comprising the preparation, including their range of lytic activity toward specific bacterial pathogens, morphology of their plaques, cycle of their development, restriction profile of their DNAs, specificity of their genomes (based on complete genome sequencing), and other properties. The preparation did not produce any signs of acute or chronic intoxication in the experimental animals. Therapeutic and prophylactic efficiency of the phagebiotic composition was demonstrated in the prevention and treatment of the experimental acute K. pneumoniae infection in mice. The investigations have shown that the preparation possesses a high therapeutic efficiency and is highly competitive with ciprofloxacin which is very effective against the infective strain K. pneumoniae. Our small-scale clinical trial was aimed to evaluate therapeutic effectiveness of the phagebiotic composition in an epidemiological emergency situation in an intensive care unit, caused by multi-resistant strains of Acinetobacter baumannii, Klebsiella pneumoniae and Pseudomonas aeruginosa. Seventy nine per cent of the initial samples from 14 patients' endotracheal aspirate, blood and urine were contaminated. Twenty-four hours after the 3-day phage therapy (20 ml of cocktail at a titer for each phage 108 pfu/ml were introduced intragastrically through a tube once a day) contamination level dropped to 21%. Hence the obtained results enabled us to create a new phagebiotic composition that may be used as an alternative to antibiotics to treat these healthcare-associated infections.

A small-scale experiment of using phage-based probiotic dietary supplement for prevention of E. coli traveler's diarrhea.

Traveler's diarrhea (TD) is caused by Escherichia coli in 30% of cases. We have developed a phage cocktail for prophylaxis of TD caused by E.coli, Shigella flexneri, Shigella sonnei, Salmonella enterica, Listeria monocytogenes or Staphylococcus aureus, and investigated its effectiveness against infection caused by the non-pathogenic Lac (-) strain of E.coli K12 C600 in animal and human trials. On the 6th day of both animal and human trials E. coli K12 C600 strain was detected in titer of 104 CFU/g of mice feces and 106 CFU/g of human feces in the control (untreated) groups, while it was not detected in the samples of either of the study (phage-treated) groups. These results have great significance because the original coliphages included in the cocktail have a broad host-range including ETEC, EAEC and EHEC strains which cause severe cases of TD.

[Quantitative and qualitative composition of axilla microbiota in practically healthy individuals].

AIM: Characteristics of quantitative and qualitative composition of cultured microorganisms isolated from axilla skin of practically healthy individuals. MATERIALS AND METHODS: 77 practically healthy individuals aged 18 to 40 years were examined. Species identification of microorganisms was carried out byculture-morphologic, tinctorial and biochemical properties using time-of-flight mass spectrometer and rpoB gene amplification with subsequent direct sequencing. RESULTS: Quantitative evaluation of microbial composition of axilla skin microbiota in most of the practically healthy individuals varied in the 4-5 lg CFU/ml interval, whereas seeding of skin by this microbiota at the level of 8 lg CFU/ml was not detected. 158 strains of 24 microorganism species were identified in this biotope. Most of these strains (68.9%) belonged to Corynebacterium genus, 21.6% of strains--to Staphylococcus genus, 7.6% of strains--to Micrococcus genus and 1.9% of strains--Candida albicans. 16 species of corynebacteria were isolated with predomination of C. tuberculostearicum (40.3%), C. amycolatum (18.4%) and C. ureicelerivorans (14.8%) strains. The microbial landscape in most of the examined individuals (77.9%) was presented by microorganism association. CONCLUSION: Quantitative and qualitative species composition of cultured microorganisms isolated from axilla skin biotope of practically healthy individuals was characterized for the first time.