Recombinant Pneumolysin of Pneumococci Induces TLR4 Expression and Maturation of Dendritic Cells In Vitro.

Pneumolysin (Ply) is a target for the development of serotype-independent pneumococcal vaccines, an important condition for the efficacy of which is their ability to activate innate immunity with the subsequent formation of adaptive immunity. In this study, the ability of recombinant full-length Ply (rPly) of pneumococci to induce TLR expression and maturation of dendritic cells generated from mouse bone marrow was evaluated. It was shown that rPly in vitro increased the number of dendritic cells expressing Toll-like receptor 4 (TLR4) on the membrane. rPly caused maturation of dendritic cells generated from mouse bone marrow, which manifested in a decrease in the number of progenitor cells (CD34), an increase in the number of cells expressing the adhesion molecule CD38, costimulatory molecules CD80 and CD86, molecules of terminal differentiation of dendritic cells CD83, as well as molecules of antigenic presentation of the major histocompatibility complex class II.

Immunization with Recombinant Pneumolysin Induces the Production of Antibodies and Protects Mice in a Model of Systemic Infection Caused by Streptococcus pneumoniae.

Immunogenic and protective activity of recombinant pneumolysin was studied in experiments on male BALB/c mice. The mice were immunized intraperitoneally with recombinant pneumolysin sorbed on Al(OH)3 (200 µg per mouse). In 2 weeks after immunization, the isotypes of antibodies to recombinant pneumolysin in the serum of immunized mice were determined by ELISA. The animals were infected with Streptococcus pneumoniae serotype 3. Immunization with recombinant pneumolysin induced the production of anti-pneumolysin antibodies, mainly of IgG1 subisotype. On day 21 after intraperitoneal infection with S. pneumoniae serotype 3 in a dose of 106 microbial cells, the survival rate of animals immunized with recombinant pneumolysin in a dose of 25 µg/mouse was 67% vs. 0% in the control (p<0.001). Recombinant pneumolysin could be considered as a promising protective antigen for inclusion in the serotype-independent vaccine against S. pneumoniae.

[ROLE OF PURINERGIC RECEPTORS IN IMMUNE RESPONSE].

Purine receptors are located on immune and somatic cells of animal and human organisms. Summation of signals from purine and TOLL-like receptors takes place on the level of inflammasome formation and results in summation of the first and second signals of innate immunity. The first signal--from PAMPs (pathogen associated molecular patterns), the second--from DAMPs (danger associated molecular patterns). Adenosine triphosphate (ATP) is the most studied DAMP. ATP connects with purine receptors which include P2 (P2X7 receptors are the best described), that results in opening of channels of these receptors and transit of ATP into the cell. In parallel exit of K⁺ from cells and entrance of Ca²âº and Na⁺ into the cells is observed, that is associated with activation of the immune competent cell. Damaged cells dying via necrosis or apoptosis are the source of extracellular ATP, as well as activated immunocytes. Signals from P2 and TOLL-like receptors are summarized in effectors of immune response, and activation of P2 receptors in lymphocytes makes a contribution into activation of cells, mediated by T-cell receptor. Negative side of purine receptor activation is a stimulating effect on proliferation and metastasis of malignant cells. The practical output of knowledge on functioning of purine receptors for clinical immunology is the application of agonists and antagonists of purine receptors, as well as explanation of effect of immune modulators from the position of launch of K⁺/Na⁺-pump; resulting in prolonged activation of immune competent cells.

[EPITOPIC SPECIFICITY OF A SYNTHETIC DISACCHARIDE, RECURRING LINK OF CAPSULE POLYSACCHARIDE CHAIN OF SEROTYPE 3 STREPTOCCUS PNEUMONIAE].

AIM: Study epitopic specificity of synthetic disaccharide, recurring link of serotype 3 S. pneumoniae, conjugated with bovine serum albumin (BSA). MATERIALS AND METHODS: Conjugate of the synthetic disaccharide with BSA was obtained by squarate method. Antigenic activity of the conjugate was studied in competitive EIA. Titers of IgG against capsule polysaccharide of serotype 3 S. pneumoniae were determined in EIA by using sera of mice immunized twice with disaccharide conjugate sorbed onto aluminum hydroxide. RESULTS: Disaccharide conjugate used as a well-covering antigen (4 µg/well) in EIA was characterized by a high degree of specificity and interacted only with IgG against serotype 3 S. pneumoniae in antimicrobial sera of animals without reacting with antibodies (ABs) against other pneumococcus serotypes (6B, 10A, 19A, 19F, 23F). Disaccharide conjugated with BSA was determined in competitive EIA to inhibit bonding of ABs to disaccharide by 78.8%, bacterial capsule polysaccharide by 56.9%, BSA did not inhibit the sera activity. The study of sera of mice immunized by serotype 3 S. pneumoniae disaccharide conjugate in EIA, where capsule polysaccharide was used as a plate-sorbed antigen, has established the presence of IgG against capsule polysaccharide at a titer of 1:1600. CONCLUSION: The disaccharide that is a single recurring link of serotype 3 S. pneumoniae contains a key epitope of capsule polysaccharide. The synthetic disaccharide could be used as a component of multivalent conjugated pneumococcal vaccines and for development of diagnostic test-systems.

[STUDY OF PROTECTIVE ACTIVITY OF PROTEIN-CONTAINING ANTIGENS OF STREPTOCOCCUS PNEUMONIAE IN A HETEROLOGOUS SYSTEM].

AIM: Study protective activity of protein-containing antigens of pneumococcus, obtained from serotypes 6B, 10A, 14, 19F, 23F and 36R, against infection with heterologous strains of S. pneumoniae. MATERIALS AND METHODS: S. pneumoniae strains of serotypes 3, 6B, 10A, 14, 19F, 23F and 36R, obtained from the collection of pneumococcus strains of Mechnikov RIVS, were used in the study. Protein-containing antigens of S. pneumoniae were isolated by acetone precipitations of supernatant fraction of culture medium. Protective activity of preparations of protein-containing antigens of pneumococcus as studied in experiments of active protection of BALb/c line mice. RESULTS: The data obtained give evidence, that protein-containing antigens of pneumococcus, isolated from serotypes 6B, 10A, 14, 19F and 23F, effectively protect animals from subsequent infection with a heterologous S. pneumoniae strain of serotype 3 No. 11/56. Protection was noted at a level from 80 to 100% (p ≤ 0.05). Similar protective effect was detected in another experiment in a group of mice, immunized with preparations of protein-containing antigens of pneumococcus, obtained from serotypes 6B and 36R, against infection with a heterologous S. pneumoniae strain of serotype 3 No. 11/56. Protection was noted at a level of 90% (p ≤ 0.05). CONCLUSION: The results of the experiments carried out allow to assume, that the main role in formation of cross-protection in experiments in animals is played by pneumococcus, proteins, that are a part of the studied preparations, and not polysaccharide antigens.

[Analysis of extracellular proteome of Staphylococcus aureus 6 at the end of exponential growth phase].

AIM: Determine protein specter that Staphylococcus aureus synthesizes and secretes at early growth phase--the exponential phase. MATERIALS AND METHODS: Proteins secreted by S. aureus strain 6 into cultivation medium at the end of exponential growth phase (4.5 hours) were studied. 11 proteins were identified by liquid chromatography--mass-spectrometry method. RESULTS: Only in 3 of these proteins the presence of signal peptides was predicted, which indicates their extracellular localization; the rest of the proteins were localized predominantly in bacterial cytoplasm. 5 of 11 proteins function as enzymes of carbohydrate metabolism. Other extracellular proteins that could indicate its contamination with proteins from disrupted bacterial cells were not detected in S. aureus cultural liquid filtrate. It has been suggested that enzymes of carbohydrate metabolism can provide bacterial cells with energy necessary for passage from lag-phase into exponential growth phase. Superoxide dismutase enzyme probably provides the course of oxidation-reduction processes. Synthesis of other proteolytic enzymes and toxins is carried out at later stages of development of bacterial population. Immunization of mice with a mixture of 11 identified proteins showed their protective properties after infection by S. aureus 6 strain. CONCLUSION: Based on the above-mentioned, the complex of isolated proteins may be perspective in development of a new strategy of prophylaxis and therapy of staphylococcus infections.

Development of approaches to creation of experimental test system for evaluation of antigenic activity of synthetic oligosaccharide ligands related to fragments of the Streptococcus pneumoniae type 14 capsular polysaccharide.

A conjugate of a synthetic hexasaccharide fragment of the Streptococcus pneumoniae type 14 capsular polysaccharide with bovine serum albumin (BSA) has been prepared. The antigenic activity and specificity of this conjugate are comparable with those of natural antigens of S. pneumoniae type 14. The data suggest that the resulting synthetic conjugate can be used as a coating antigen in an experimental test system (based on enzyme immunoassay) for evaluating the antigenic activity and specificity of synthetic oligosaccharide ligands and for testing specimens of natural capsular polysaccharides and immune sera.

[Study of protective activity of Streptococcus pneumoniae protein-containing antigen complex in homologous system].

AIM: Study protective activity of S. pneumoniae protein-containing antigen complex obtained from T3No.3 strain against infection by homologous pneumococcus strain. MATERIALS AND METHODS: S. pneumoniae T3No.3 (serotype 3) strain obtained from collection of pneumococcus strains of Mechnikov Research Institute of Vaccines and Sera was used in the study. S. pneumoniae protein-containing antigen complex was isolated by precipitation by 2 volumes of acetone of supernatant fraction of cultural medium used for pneumococcus cultivation. Molecular mass of proteins contained in S. pneumoniae antigen complex was determined by SDS electrophoresis in polyacrylamide gel. Protective activity of S. pneumoniae protein-containing antigen complex was studied in BALB/c line mice active protection experiments. Activity of mice immune sera obtained against whole-cell pneumococcus culture (T3No.3 strain) was determined in vitro by solid phase indirect EIA. RESULTS: The data obtained give evidence that the isolated protein-containing antigen complex from S. pneumoniae T3No.3 strain effectively protects mice from consequent infection by a homologous S. pneumoniae strain. S. pneumoniae protein-containing antigen complex sorbed on solid phase at 5 microg dose was established by using EIA to interact with homologous mice immune sera. CONCLUSION: The results of the carried out studies allow to move to studies of cross-activity of S. pneumoniae protein-containing antigen complex isolated from T3No.3 strain.

[Immunogenic activity of a conjugate of synthetic hexasaccharide related to a streptococcus pneumoniae serotype 14 capsule polysaccharide chain fragment].

AIM: Study antigenic and immunogenic activity of a conjugate of synthetic hexasaccharide related to a S. pneumoniae serotype 14 capsule polysaccharide chain fragment with bovine serum albumin (BSA). MATERIALS AND METHODS: Synthetic glucoconjugate based on BSA protein carrier and hexasaccharide ligand reflecting capsule polysaccharide chain fragment was obtained by using squarate method. Natural polysaccharide-protein complex from S. pneumoniae serotype 14 strain was obtained from cultural fluid supernatant by acetone precipitation. IgG titer against hexasaccharide/capsule polysaccharide was determined in antimicrobial sera and sera of mice immunized with glucoconjugate by EIA method. RESULTS: Immunogenic activity ofglucoconjugate based on BSA protein carriers and synthetic hexasaccharide reflecting S. pneumoniae serotype 14 capsule protein chain fragment was established. After 2 immunizations antibodies against hexasaccharide ligand and BSA were determined in blood sera of mice. Antibody titers against hexasaccharide exceeded the level in intact mice by 4.2 times. BSA in the conjugate did not have effect on production of antibodies against hexasaccharide. CONCLUSION: The developed experimental test-system based on synthetic glucoconjugate is useful for evaluation of level of antibodies against S. pneumoniae serotype 14 in infected and, probably, carriers of bacteria.

[Sulfated polysaccharides of brown seaweeds--ligands of toll-like receptors].

The interaction of sulfated polysaccharides--fucoidans from brown seaweeds Laminaria japonica, Laminaria cichorioides and Fucus evanescens with Toll-like receptors (TLRs) expressed on membranes of embryonic human kidney epithelial cells (HEK293-null, HEK293-TLR2/CD14, HEK293-hTLR4/CD14-MD2 and HEK293-hTLR2/6) was investigated. In vitro fucoidans specifically interacted with TLR-2, TLR-4, and the heterodimer TLR-2/6 resultated in activation of transcription nuclear factor NF-kappaB. Analysis of composition the hydrolyzed fucoidan from F. evanescens was carried out by gas-liquid chromatography and chromatography-mass spectrometry. Results indicated the absence of 3-3-hydroxytetradecanoic acid (3-OHC14), the basic component of lipopolysaccharides in the preparation. Thus, the obtained results suggested that fucoidans from brown seaweeds possessing immunotropic activity are independent ligands for TLRs, and are able to induce genetically determined biochemical processes of protection organisms against pathogenic microorganisms.

Interactions between sulfated polysaccharides from sea brown algae and Toll-like receptors on HEK293 eukaryotic cells in vitro.

We studied the interactions between sulfated polysaccharides, fucoidans from sea brown algae Laminaria japonica, Laminaria cichorioides, and Fucus evanescens, with human Toll-like receptors (TLR) expressed on membranes of cultured human embryonic kidney cells (HEK293-null, HEK293-TLR2/CD14, HEK293-hTLR4/CD14-MD2, and HEK293-hTLR5). Fucoidans interacted with TLR-2 and TLR-4, but not with TLR-5, and were nontoxic for the cell cultures. L. japonica fucoidan (1 mg/ml), L. cichorioides fucoidan (100 µg/ml and 1 mg/ml), and F. evanescens fucoidan (10 µg/ml-1 mg/ml) activated transcription nuclear factor NF-Ï°B by binding specifically to TLR-2. L. japonica fucoidan (100 µg/ml and 1 mg/ml), L. cichorioides fucoidan (10 µg/ml-1 mg/ml), and F. evanescens fucoidan (1 µg/ml-1 mg/ml) activated NF-Ï°B via binding to TLR-4. These results indicated that fucoidans could induce in vivo defense from pathogenic microorganisms of various classes.

[Effect of sulfated polysaccharides from brown algae on proliferative and cytotoxic activity of mice splenocytes].

AIM: Study effect of fucoidans from brown algae on proliferative and cytotoxic activity of mice splenocytes. MATERIALS AND METHODS: Proliferative and cytotoxic activity of mice splenocytes in vitro and ex vivo were studied in lymphocyte blast transformation reaction and in cytotoxic MTT-test on K562 human erythroblast leucosis cell line. Microphotography and microscopy were performed by using Axiocam HS photosystem and computer program AxioVision 4 (Germany). RESULTS: Fucoidans from brown algae Fucus evanescens, Laminaria cichorioides and Laminaria japonica in vitro and ex vivo systems were established to increase proliferative activity of mice splenocytes which is evidenced by an increase of stimulation index. Results of in vitro and ex vivo cytotoxic activity studies demonstrate that fucoidans which are various by chemical structure stimulate activity of NK-cells and facilitate an increase of splenocyte cytotoxic potential level against NK sensitive K562 cell line. CONCLUSION: The data obtained from the study demonstrate an ability of fucoidans to stimulate splenocyte proliferation and NK-cell killer activity, and studies of relation between structure and functions of sulfated polysaccharides facilitate a more detailed understanding of aspects of their mechanism of action on innate immunity system, thus providing the basis for development of new immunobiologic preparations - modifiers/agonists of innate immunity.

[Novel type of vaccine with a combination of Toll like receptor agonists--TLR 1/2, 4, 5/6, 9].

AIM: Proof of therapeutic efficacy of a novel type of vaccine with a combination of natural Toll like receptor agonists (TLR) 1/2, 4, 5/6, 9 in infectious and noninfectious human pathology. MATERIALS AND METHODS: Immunovac-VP-4 vaccine, containing antigens of opportunistic microorganisms that are TLR 1/2, 4, 5/6, 9 ligands, was used for experiments and clinical trials. RESULTS: Immunovac-VP-4 activates innate immunity by inducing maturation of dendritic cells with expression of costimulating molecules on their membrane (CD40+, CD80+, CD86+), terminal differentiation molecules--CD83+ and antigen-presenting molecules (MHC class I and II); activates proinflammatory (TNFalpha, IL-6) and regulatory (IL-12, INFgamma) cytokine synthesis that programs T-lymphocyte differentiation by Th1 pathway; increases cytotoxic activity of natural killer cells, inhibits melanoma B16 growth and Lewis lung carcinoma metastasis. Therapeutic effect of Immunovac-VP-4 was evident regardless of pathology by a significant decrease of quantity and severity of recidives, improvement of all clinical parameters, reduction of quantity of administered pharmaceutical preparations including antibiotics and glucocorticosteroids. The rate of intercurrent acute respiratory viral illnesses and their bacterial complications decreased. Immunovac-VP-4 therapy modified course of illness from severe into milder forms. Positive therapeutic effect was 69.2 - 100%. CONCLUSION: High therapeutic effect of vaccine therapy is based on innate immunity activation by combining TLR agonists. Immunovac-VP-4 contains an optimal combination of natural TLR agonists that ensure high therapeutic effect in various nosological forms of infectious and noninfectious human pathology.

[Protective activity of Immunovac-VP-4 vaccine against avian influenza virus H5N2 administered by different methods].

AIM: To experimentally assess protective effect of Immunovac-VP-4 vaccine against avian influenza virus H5N2. MATERIALS AND METHODS. Immunization of mice with polycomponent vaccine Immunovac-VP-4 was performed using oral or mucosal route of administration (intranasally, orally, and with combined nasal-oral method). Immunized mice were inoculated intranasally by influenza virus H5N2 adapted for mice. Survival of mice in experimental and control (intact) groups was assessed daily during 14 days. Survival and death rates of mice were determined. Levels of cytokines in sera of mice from both groups were measured by enzyme immunoassay. RESULTS: Half of experimental animals survived after triple subcutaneous administration of vaccine in dose 20 mcg and subsequent intranasal challenge with avian influenza virus H5N2. Single subcutaneous immunization with dose 400 mcg resulted in survival of 80 +/- 12.6% of mice after challenge. Triple intranasal and combined intranasal-oral immunization as well as after triple subcutaneous immunization resulted in survival of half of challenged mice. In control group challenge was lethal for 90 - 100% of mice. Same methods of immunization lead to increase of IL-6, IL-12, IL-15, and IFN-gamma levels. CONCLUSION: Data about significant protective effect after immunization with Immunovac-VP-4 against avian influenza virus H5N2 were obtained. Immunovac-VP-4 administered by mentioned routes activated nasal-associated lymphoid tissue providing first line defense at entry site of influenza infection, which demonstrates need to further study of this vaccine during development of strategy for non-specific prophylaxis of influenza infection.

[Pneumococcal surface protein A and new approaches for pneumococcal vaccine development].

The problem of pneumococcal infections is pressing for the whole world. Existing vaccines based only on pneumococci polysaccharide antigens or polysaccharide antigens and diphtherial anatoxin are not capable of protecting from all serotypes of the microorganism. Reasonability of creation of pneumococcal vaccine based on surface proteins of Streptococcus pneumoniae is discussed in the literature. One of such key pneumococcal proteins is pneumococcal surface protein A (PSPA), because it is detected in all the S. pneumoniae strains, has cross activity and switches B-cell immune response to T-cell. Currently the development of conjugated vaccine based on surface proteins and capsule polysaccharides of pneumococcus seems promising.

Growth-dependent release of carbohydrate metabolism-related and antioxidant enzymes from Staphylococcus aureus strain 6 as determined by proteomic analysis.

Proteins released into the culture medium by Staphylococcus aureus (S. aureus) strain 6 were determined at the end of the exponential growth phase (4.5 h). Eleven proteins were identified by liquid chromatography coupled with mass spectrometry. Three proteins were predicted to have signal peptides indicating their extracellular localization. The other proteins were presumably located in the cytoplasm of the bacteria. Five out of the 11 proteins were involved in carbohydrate metabolism. Other intracellular proteins of S. aureus were not detected in the culture medium. This indicates that the release of these 11 proteins was specific and that unspecific protein release due to damaged or dying bacteria did not play a role. It is suggested that enzymes associated with carbohydrate metabolism may provide the energy necessary for the transition of bacteria from a resting to a proliferative state. Another enzyme released by S. aureus, superoxide dismutase, may catalyze redox reactions in this context. The production of other proteolytic enzymes and toxins may take place at later stages of bacterial growth. A cocktail of these 11 proteins was used for the immunization of mice. Indeed, vaccination with these proteins prolonged the survival times of mice upon infection with S. aureus strain 6. Therefore, these proteins may have implications for the development of novel strategies for the prevention and therapy of S. aureus infections.

[Production of cytokines by murine bone marrow dendritic cells in vitro mediated by sulfated polysaccharides obtained from sea brown algae].

AIM: To assess in vitro cytokine production by murine bone marrow dendritic cells (DC) matured under the effect of sulfated polysaccharides--fucoidanes from sea brown algae Laminaria cichorioides and Laminaria japonica. MATERIALS AND METHODS: CBA line mice were used to obtain bone marrow origin precursors of DC. Isolation and study of chemical composition and structure of fucoidanes were performed using modern research methods. Expression of surface markers was determined by flow cytometry (FACS-analysis) using monoclonal antibodies to respective antigens. Levels of cytokine production were measured by t-ELISA using kits manufactured by Biosource (Belgium). RESULTS: I was determined that fucoidans induce maturation of DC that was evident by expression of terminal differentiation marker CD83, activation marker CD38, enhanced expression of costimulating CD86, antigen-presenting MHC II and adhesive CD11c molecules. Fucoidanes stimulate DC to produce proinflammatory (TNF-alpha, IL-6, IL-1beta) and regulatory (IL-12) cytokines. Fucoidanes enhance expression of TLR-2 and TLR-4 but do not influence on expression of TLR-9. CONCLUSION: It was shown that fucoidanes from sea brown algae L. cichorioides and L. japonica activate innate immunity system that is evident by enhanced expression of surface molecules associated with DC maturation and increased production of proinflammatory and regulatory cytokines by DC. Enhanced expression of TLR-2 and TLR-4 allows to suppose that studied fucoidanes could have anti-infective effect in vivo.

[Effect of methods of application of bacterial ligands on activation of lymphoid organs' effectors in mice].

AIM: Evaluation of differentiation dynamics and localization of various populations of lymphocytes as well as their expression of TLRs during different methods of administration (intranasal, oral, and subcutaneous) of bacterial ligands of opportunistic microorganisms (Immunovac-VP-4 vaccine) in experiment on mice. MATERIALS AND METHODS: Polycomponent vaccine Immunovac-VP-4 consisting of ligands of 4 opportunistic bacteria was administered to CBA line mice. Groups of mice were immunized orally, subcutaneously, or intranasally. Number of mononuclear leukocytes, as well as levels of cytokines, lymphocytic antigens, and cytotoxic activity of cells were measured. RESULTS: It was demonstrated that modification of immunophenotype of lymphocytes and cytotoxic activity of NK cells depends from route of administration of Immunovac-VP-4 because the most intensive activation of cells occurred in organs proximal to place of vaccine application. However, already 1 day after administration of vaccine there was intensive exchange between lymphoid cells not only in nasal associated lymphoid tissue, bronchial associated lymphoid tissue, and gut associated lymphoid tissue but also in spleen that points to integration of fine mechanisms of mucosal and systemic immune response regulation. CONCLUSION: Development of noninvasive methods of vaccination is an optimal way of safe and mass prevention of infectious diseases.

[Expression of Toll-like receptors in spleen and lymphatic nodes after immunization by mucosal routes].

AIM: To determine level of Toll-like receptors (TLRs) expression in spleen and lymphatic nodes of mice after immunization by mucosal routes. MATERIALS AND METHODS: Mice were immunized with polycomponent vaccine Immunovac either by mucosal or subcutaneous route. Expression of TLRs in spleen, respiratory tract-associated lymphatic nodes as well as in small intestine was measured in immunized mice by flow cytomentry method. RESULTS: After immunization of mice by subcutaneous, intranasal and oral routes level of TLRs expression was different. Significant expression of TLR9 and absence of TLR2 expression was noted after non-parenteral methods of immunization. After oral immunization expression of TLRs was identified in gut-and respiratory tract-associated lymphoid tissue as well as in spleen; after intranasal immunization--in respiratory tract-associated lymphoid tissue, and after subcutaneous immunization--in spleen and respiratory tract-associated lymphoid tissue. CONCLUSION: After oral immunization expression of TLRs was identified in all studied organs, including spleen. Involvement of spleen to this process allows to assume establishment of not only local but also systemic immunity.

[Immunovac-VP-4 for prevention of acute respiratory diseases in children's communities].

AIM: Assessment of prophylactic effect of Immunovac-VP-4 against acute respiratory diseases (ARDs) in collectives of children. MATERIALS AND METHODS: Immunovac-VP-4 was used for prophylaxis of ARDs in communities of children (daycare centers, boarding school). During 3 consecutive controlled studies performed during peak incidence of epidemic influenza and ARD (1st study) and during pre-epidemic period (2nd and 3rd studies) the incidence of ARDs was studied in groups of vaccinated and non-vaccinated children. Criteria for assessment of ARDs incidence and their severity were as follows: number of ARD episodes per child, number of children with recurrent episodes of ARD during period of follow-up, duration of ARDs, and number of children with bacterial complications (bronchitis, otitis, etc.). Effect of intervention on immunologic parameters was assessed on levels of sIgA, IgG, IgA, and antibody titers in saliva. Schedule of vaccine administration was 3 daily intranasal and 6 - 9 oral administration of the vaccine with 3 - 4 days interval. RESULTS: Results of all three studies were virtually the same: decrease of number of ARD episodes and their duration; 3.1-fold reduction of number of children with recurrent infections during 14 months of follow-up, and 10.9--12-fold reduction during first 7 months of follow-up; decrease of bacterial complications rate (1.9% in children in intervention group, 11.9%--in control group). Increase of total immunoglobulin level and antibody titers to antigenic components of the vaccine from low baseline level was observed in saliva of vaccinated children. CONCLUSION: Immunovac-VP-4 results in enhanced and prolonged prophylactic effect on ARDs incidence and recommended for building of optimal system of prevention of polyetiologic complex of ARDs.