Evaluation of New Antimicrobial Agents Based on tris(1H-Indol-3-yl)methylium Salts: Activity, Toxicity, Suppression of Experimental Sepsis in Mice

The antimicrobial activity and toxicity of three novel synthetic antibacterial agents containing tris(1H-indol-3-yl)methylium fragment were studied in vitro and in vivo. All compounds in vitro revealed high activity (minimal inhibitory concentration (MIC) 0.13–1.0 µg/mL) against bacteria that were either sensitive or resistant to antibiotics, including multidrug-resistant clinical isolates. The derivatives combining high antimicrobial activity with relatively low cytotoxicity against human donor fibroblasts HPF-hTERT were subjected to further testing on mice. In vivo they revealed fairly good tolerance and relatively low toxicity. Acute toxicity was evaluated, and the main indicators of toxicity, including LD₅₀ and LD₁₀, were determined. A study of compounds in vivo showed their efficiency in the model of staphylococcal sepsis in mice. The efficiency of compounds may be due to the ability of indolylmethylium salts to form pores in the cytoplasmic membrane of microbial cells and thereby facilitate the penetration of molecules into the pathogen.

Gausemycins A,B: Cyclic Lipoglycopeptides from Streptomyces sp.*

We report a novel family of natural lipoglycopeptides produced by Streptomyces sp. INA-Ac-5812. Two major components of the mixture, named gausemycins A and B, were isolated, and their structures were elucidated. The compounds are cyclic peptides with a unique peptide core and several remarkable structural features, including unusual positions of d-amino acids, lack of the Ca²⁺ -binding Asp-X-Asp-Gly (DXDG) motif, tyrosine glycosylation with arabinose, presence of 2-amino-4-hydroxy-4-phenylbutyric acid (Ahpb) and chlorinated kynurenine (ClKyn), and N-acylation of the ornithine side chain. Gausemycins have pronounced activity against Gram-positive bacteria. Mechanistic studies highlight significant differences compared to known glyco- and lipopeptides. Gausemycins exhibit only slight Ca²⁺ -dependence of activity and induce no pore formation at low concentrations. Moreover, there is no detectable accumulation of cell wall biosynthesis precursors under treatment with gausemycins.

Aminoalkylamides of Eremomycin Exhibit an Improved Antibacterial Activity

After decades, the glycopeptide vancomycin is still the preferred antibiotic against resistant strains of Gram-positive bacteria. Although its clinical use is strictly regulated, the gradual spread of vancomycin-resistant bacteria, such as glycopeptide-resistant and glycopeptide-intermediate Staphylococcus aureus and vancomycin-resistant Enterococcus spp., is a serious health problem. Based on the literature data and previous studies, our main goal was to assess the antimicrobial potential and to study the structure-activity relationship of new eremomycin aminoalkylamides. We designed and synthesized a series of new eremomycin amides in which eremomycin is conjugated with a hydrophobic arylalkyl group via an alkylenediamine spacer, and tested their antibacterial activities on a panel of Gram-positive strains that were sensitive and resistant to a "gold-standard" vancomycin. Based on the data obtained, the structure-activity relationships were investigated, and a lead compound was selected for in-depth testing. Research carried out using an in vivo model of staphylococcus sepsis, acute toxicity studies, and the estimated therapeutic index also showed the advantage of the selected eremomycin amide derivative in particular, as well as the chosen direction in general.

Discovery of Amphamide, a Drug Candidate for the Second Generation of Polyene Antibiotics

Amphotericin B (AmB, 1) is the drug of choice for treating the most serious systemic fungal or protozoan infections. Nevertheless, its application is limited by low solubility in aqueous media and serious side effects such as infusion-related reactions, hemolytic toxicity, and nephrotoxicity. Owing to these limitations, it is essential to search for the polyene derivatives with better chemotherapeutic properties. With the objective of obtaining AmB derivatives with lower self-aggregation and improved solubility, we synthesized a series of amides of AmB bearing an additional basic group in the introduced residue. The screening of antifungal activity in vitro revealed that N-(2-aminoethyl)amide of AmB (amphamide, 6) had superior antifungal activity compared to that of the paternal AmB. Preclinical studies in mice confirmed that compound 6 had a much lower acute toxicity and higher antifungal efficacy in the model of mice candidosis sepsis compared with that of AmB (1). Thus, the discovered amphamide is a promising drug candidate for the second generation of polyene antibiotics and is also prospective for in-depth preclinical and clinical evaluation.

The effect of elongation of a peptide substituent with ArgSer motif on the antimicrobial properties of hemin derivatives

The natural metalloporphyrin hemin possesses a number of properties that determine its attractiveness as a basis for creating potential medicines. The development of research in this area is restrained by hemin’s pronounced toxicity, mainly in relation to normal red blood cells, and also by its water insolubility. We previously synthesized amino acid and peptide hemin derivatives with sufficient water solubility and in some cases high antimicrobial (antibacterial and antifungal) potency [1, 2]. In order to establish the relationship between structure and function, this paper studies the peptide substituent in hemin derivatives (HD) elongated by multiplying the -ArgSer- motif and its effect on the biological and physicochemical properties of their aqueous solutions. A nonlinear nonmonotonic dependence of their physicochemical properties and biological potency on the HD concentration and the length of peptide substituent was revealed based on calculations of hydrophilic properties of substituents in HD and a study by electron and laser correlation spectroscopy of their properties in aqueous solutions.

Synthesis and antimicrobial activity of 3,4-bis(arylthio)maleimides

A series of 3,4-bis(arylthio)maleimides were synthesized and their antimicrobial activity was evaluated against Gram-positive and Gram-negative bacteria, including multidrug resistant (MDR) strains and some fungi. Most compounds turned out to be highly active, activity being dependent on substituents on phenyl rings.

Synthesis and evaluation of biological activity for dual-acting antibiotics on the basis of azithromycin and glycopeptides

One of the promising directions of the combined approach is the design of dual-acting antibiotics - heterodimeric structures on the basis of antimicrobial agents of different classes. In this study a novel series of azithromycin-glycopeptide conjugates were designed and synthesized. The structures of the obtained compounds were confirmed using NMR spectroscopy and mass spectrometry data including MS/MS analysis. All novel hybrid antibiotics were found to be either as active as azithromycin and vancomycin against Gram-positive bacterial strains or have superior activity in comparison with their parent antibiotics. One compound, eremomycin-azithromycin conjugate 16, demonstrated moderate activity against Enterococcus faecium and Enterococcus faecalis strains resistant to vancomycin, and equal to vancomycin's activity for the treatment of mice with Staphylococcus aureus sepsis.

Eremomycin pyrrolidide: a novel semisynthetic glycopeptide with improved chemotherapeutic properties

PURPOSE

Development of new semisynthetic glycopeptides with improved antibacterial efficacy and reduced pseudoallergic reactions.

METHODS

Semisynthetic glycopeptides 3-6 were synthesized from vancomycin (1) or eremomycin (2) by the condensation with pyrrolidine or piperidine. The minimum inhibitory concentration (MIC) for the new derivatives was measured by the broth micro-dilution method on a panel of clinical isolates of Staphylococcus and Enterococcus. Acute toxicity (50% lethal dose, maximum tolerated doses), antibacterial efficacy on model of systemic bacterial infection with S. aureus and pseudoallergic inflammatory reaction (on concanavalin A) of eremomycin pyrrolidide (5) were evaluated in mice according to standard procedures.

RESULTS

The eremomycin pyrrolidide (5) was the most active compound and showed a high activity against Gram-positive bacteria: vancomycin-susceptible staphylococci and enterococci (minimum inhibitory concentrations [MICs] 0.13-0.25 mg/L), as well as vancomycin-intermediate resistant Staphylococcus aureus (MICs 1 mg/L). Antimicrobial susceptibility tested on a panel of 676 isolates showed that 5 had similar activity for the genera Staphylococcus and Enterococcus with MIC90=0.5 mg/L, while vancomycin had MIC90=1-2 mg/L. The number of resistant strains of Enterococcus faecium (vancomycin-resistant enterococci) (MIC =64 mg/L) with this value was 7 (8%) for vancomycin (1) and 0 for the compound 5. In vivo comparative studies in a mouse model of systemic bacterial infection with S. aureus demonstrated that the efficacy of 5 was notably higher than that of the original antibiotics 1 and 2. In contrast to 1, compound 5 did not induce pseudoallergic inflammatory reaction (on concanavalin A).

CONCLUSION

The new semisynthetic derivative eremomycin pyrrolidide (5) has high activity against staphylococci and enterococci including vancomycin-resistant strains. Compound 5 has a higher efficacy in a model of staphylococcal sepsis than vancomycin (1) or eremomycin (2). In striking contrast to natural antibiotics, the novel derivative 5 does not induce a pseudoallergic inflammatory reaction to concanavalin A and therefore has no histamine release activity. These results indicate the advantages of a new semisynthetic glycopeptide antibiotic eremomycin pyrrolidide (5) which may be a prospective antimicrobial agent for further pre-clinical and clinical evaluations.

Two approaches to the use of benzo[c][1,2]oxaboroles as active fragments for synthetic transformation of clarithromycin. J Enzyme Inhib Med Chem 2017;32:452-456. [PMID: 28097898 PMCID: PMC6009856 DOI: 10.1080/14756366.2016.1261129]

Clarithromycin (active against Gram positive infections) and 1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole derivatives (effective for Gram negative microbes) are the ligands of bacterial RNA. The antimicrobial activities of these benzoxaboroles linked with clarithromycin at 9 or 4″ position were compared. Two synthetic pathways for these conjugates were elaborated. First pathway explored the substitution of the C-9 carbonyl group of macrolactone’s cycle via oxime linker, the second direction used the modification of the 4″-O-group of cladinose via the formation of carbamates of benzoxaboroles. 4″-O-(3-S-(1-Hydroxy-1,3-dihydro-benzo[c][1,2]oxaborole)-methyl-carbamoyl-clarithromycin showed twofold decrease in MICs for S. epidermidis and S. pneumoniae than clarithromycin. 4″-O-Modified clarithromycin demonstrated an efficacy against Gram positive strains only. Compounds with C-9 substitution were more active than 4″-O-substituted antibiotics for susceptible strains E. coli tolC and did not exceed the activity of initial antibiotics.

Hybrid Antibiotics Based on Azithromycin and Glycopeptides: Synthesis and Antibacterial Activity

A series of hybrid antibiotics on the basis of azithromycin and glycopeptides with the glycopeptide molecule attached via the aminoalkylcarbamoyl spacer to 11-position of the macrolide was synthesized. All the synthesized compounds demonstrated equal or superior to azithromycin and vancomycin antibacterial activity against 7 tested strains of grampositive bacteria. The new hybrid antibiotics were more active than azithromycin or vancomycin against S.pneumoniae ATCC 49619. Some of the compounds were active against E.faecium and E.faecalis strains resistant to vancomycin.

[Antimicrobial Properties of Eremoxylarin A Produced by Ascomycete of Sordariomycetes in Submerged Culture]

The fungal strain INA 01108 producing antibiotic substances with broad spectrum of antibacterial activity was isolated from the natural environment. By the morphological characteristics and DNA analysis it was shown to belong to Ascomycetes of Sordariomycetes. In submerged culture the strain produced at least four antibiotics. The major component of them was identified as eremophilane-type sesquiterpene eremoxylarin A. Eremoxylarin A is effective in vitro against grampositive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin group glycopeptide antibiotics resistant Leuconostoc mesenteroides VKPM B-4177. The efficacy and toxicity of eremoxylarin A was determined on a murine staphylococcal sepsis model. The dose of 6.25 mg/kg provided 100% recovery and survival of the animals, while the dose of 3.12 mg/kg was close to the ED50. The chemical structure of eremoxylarin A allows to modify the antibiotic and such studies may be relevant to design a less toxic derivative without loss of the valuable antimicrobial properties.

[Design of Novel Carboxamides of Eremomycin and Vancomycin with 4- or 3-Amino Methyl Phenyl Boric Acid and Their Investigation]

Amidation of the end carboxyl group of eremomycin and vancomycin by pinacolinic 4- or 3-amino methyl phenyl boron acids esters in the presence of the condensing reagent PyBOP resulted in formation of novel carboxamides of the antibiotics (IIIa-VIa). After elimination of the pinacolinic group under mild hydrolysis in weak acid aqueous medium there formed the respective derivatives with a residue of the nonprotected boric acid (III-VI). It was shown that the activity of the 4-substituted derivatives of the borole-containing eremomycin and vancomycin practically was the same as that of the initial antibiotics, while higher than that of the respective 3-substituted derivatives of the borole-containing derivatives against 8 strains of grampositive bacteria.

Regioselective acylation of congeners of 3-amino-1H-pyrazolo[3,4-b]quinolines, their activity on bacterial serine/threonine protein kinases and in vitro antibacterial (including antimycobacterial) activity

It was found by virtual screening that 3-amino-1H-pyrazolo[3,4-b]quinolines could have wide protein kinase inhibitory activity. Amides of titled amines and thioureas were synthesized regioselectively. 3-Amino-7-methoxy-1H-pyrazolo[3,4-b]quinoline demonstrated in vitro significant inhibitory activity on bacterial serine/threonine protein kinases (inhibition of resistance to kanamycin in Streptomyces lividans regulated by protein kinases). The studies of Structure Activity Relationship (SAR) showed that the substitution of the NH2 group and 1-NH of pyrazole ring or aromatic ring at the position 6 decreased or removed inhibitory activity.

Synthesis and study of the antifungal activity of new mono- and disubstituted derivatives of a genetically engineered polyene antibiotic 28,29-didehydronystatin A1 (S44HP)

Mono- and disubstituted novel derivatives of the heptaene nystatin analog 28,29-didehydronystatin A(1) (S44HP, 1) were obtained by chemical modification of the exocyclic C-16 carboxyl and/or an amino group of mycosamine moiety. The strategy of preparation of mono- and double-modified polyene macrolides was based on the use of intermediate hydrophobic N-Fmoc (9-fluorenylmethoxycarbonyl) derivatives that facilitated the procedures of isolation and purification of new compounds. The antifungal activity of the new derivatives was first tested in vitro against yeasts and filamentous fungi, allowing the selection of the most active compounds that were subsequently tested for acute toxicity in mice. 2-(N,N-dimethylamino)ethylamide of 1 (2) and 2-(N,N-dimethylamino)ethylamide of N-fructopyranosyl-28,29-didehydronystatin A(1) (2a) were then selected for further evaluation in a mouse model of disseminated candidosis, and showed high efficacy while being considerably less toxic than amphotericin B (AmB). The compound with improved water solubility (2G, L-glutamic acid salt of 2) showed better chemotherapeutic activity than AmB in the mouse model of candidosis sepsis on a leucopenic background. Very low antifungal effect was seen after treatment with AmB, even if it was used in maximum tolerated dose (2 mg kg(-1)). Unlike AmB, compound 2G exhibited high activity in doses from 0.4 up to 4.0 mg kg(-1), despite leucopenic conditions.

Chemical modification and biological evaluation of new semisynthetic derivatives of 28,29-Didehydronystatin A1 (S44HP), a genetically engineered antifungal polyene macrolide antibiotic

Twenty-three new derivatives of the heptaene nystatin analogue 28,29-didehydronystatin A(1) (1) (S44HP) were obtained by chemical modification of C16 carboxyl and amino groups of mycosamine. These derivatives comprised 15 carboxamides, 4 N-alkyl derivatives, 3 N-derivatives containing additional N-linked monosaccharide or disaccharide moiety (products of Amadori rearrangement), and 1 N-aminoacyl derivative. The derivatives have been tested in vitro against yeasts Candida albicans, Cryptococcus humicolus, and filamentous fungi (molds) Aspergillus niger and Fusarum oxysporum, as well as for hemolytic activity against human erythrocytes. Structure-activity relationships for the compounds obtained are discussed. The most active and least hemolytic derivative 3-(N,N-dimethylamino)propylamide of S44HP (6) was tested for acute toxicity and antifungal activity in animal model. Whereas amphotericin B and S44HP were active in vivo at doses close to the maximal tolerated dose, 6 was considerably less toxic and more active compared to these two antibiotics.

Improved antifungal polyene macrolides via engineering of the nystatin biosynthetic genes in Streptomyces noursei

Seven polyene macrolides with alterations in the polyol region and exocyclic carboxy group were obtained via genetic engineering of the nystatin biosynthesis genes in Streptomyces noursei. In vitro analyses of the compounds for antifungal and hemolytic activities indicated that combinations of several mutations caused additive improvements in their activity-toxicity properties. The two best analogs selected on the basis of in vitro data were tested for acute toxicity and antifungal activity in a mouse model. Both analogs were shown to be effective against disseminated candidosis, while being considerably less toxic than amphotericin B. To our knowledge, this is the first report on polyene macrolides with improved in vivo pharmacological properties obtained by genetic engineering. These results indicate that the engineered nystatin analogs can be further developed into antifungal drugs for human use.

N'-(alpha-aminoacyl)- and N'-alpha-(N-alkylamino)acyl derivatives of vancomycin and eremomycin. II. Antibacterial activity of N'-(alpha-aminoacyl)- and N'-alpha-(N-alkylamino)acyl derivatives of vancomycin and eremomycin

The antibacterial activities of the series of novel N'-(alpha-aminoacyl)- and N'-alpha-(N-akylamino)acyl derivatives of eremomycin and vancomycin containing hydrophobic moieties have been investigated. The N'-(N-alkylglycyl) derivatives of vancomycin are more active against vancomycin-susceptible staphylococci and enterococci and glycopeptide intermediate-resistant Staphylococcus aureus (GISA) than the corresponding eremomycin derivatives, but except for N'-[N-(p-octyloxybenzyl)glycyl-vancomycin] (28) and N'-[N-(p-octyloxybenzyl)-L-alanyl-vancomycin (33)--they are less active against glycopeptide-resistant enterococci (GRE). Derivatives 28 and 33 are the most active compounds (MIC's for glycopeptide-sensitive staphylococci and enterococci are 0.25 approximately 1 microg/ml, for GISA 1 approximately 2 microg/ml, for GRE 2 approximately 6 microg/ml). In in vivo studies, derivative 28 was active against S. aureus infections in mice with ED(50) 1 mg/kg versus 2 mg/kg for vancomycin (iv). In general N'-(N-alkylglycyl)-derivatives of vancomycin and eremomycin were more active than the corresponding N'-aminoacylated derivatives of these antibiotics containing other than glycin amino acids (L-Lys, L-Met, L-Orn, L- and D-Ala) and also L- and D-Phe or benzyl-O-L-Tyr.

[Fortification of antimicrobial barrier of the small intestine in newborn mice after oral administration of ascorbigen]

Ascorbigen, a natural product, is an indole derivative of L-ascorbic acid. Its effect on postnatal development and antibacterial resistance of the small intestine was studied on newborn mice. Ascorbigen was administered to 3-5-day old mice in a dose of 100 mg/kg orally every day for 7-10 days. 30 minutes before the last administration of the drug clinical isolates of Staphylococcus aureus or Escherichia coli were administered intragastrically to the young mice. The animals were killed in 24 hours and the frequency of the isolation of the microbes from the blood, spleen, kidneys and liver was developed. The oral use of the drug normalized the intestinal microflora, provided a reliable decrease of the bacteria isolation from the blood, spleen, kidneys and liver and prevented the animal death. The morphological examination showed that ascorbigen significantly increased the number and activity of the Paneth cells in the gland crypts, the goblet cells in the villi and mononuclear cells in the selfplate of the intestine mucous membrane vs. the intact control.

Structure-activity relationship studies of a series of antiviral and antibacterial aglycon derivatives of the glycopeptide antibiotics vancomycin, eremomycin, and dechloroeremomycin

N-(adamantyl-1)methyl, N-(adamantyl-2), and N-(omega-aminodecyl) amides of vancomycin, eremomycin, and dechloroeremomycin aglycons and their des-(N-Me-D-Leu) derivatives were synthesized and their antibacterial and anti-HIV activities were investigated. Carboxamides with an intact peptide core demonstrated activity against glycopeptide-susceptible and -resistant bacteria (1-32 microM). N-(adamantyl-1)methylcarboxamide of eremomycin aglycons had good antiretroviral activity (1.6 microM against HIV-1). Compounds with destroyed peptide core [des-(N-Me-D-Leu)-aglycon amides] were inactive against both glycopeptide-sensitive and -resistant bacteria. (Adamantyl-1)methylamide of des-(N-Me-D-Leu)-eremomycin aglycon had good antiretroviral activity (EC50 of 5.5 microM for HIV-1 and 3.5 microM for HIV-2). (Adamantyl-1)methylamides of eremomycin aglycon and its des-(N-Me-d-Leu)-derivative are the most promising and selective antiretroviral agents. Their ability to induce bacterial resistance to glycopeptide antibiotics during prolonged administration may be expected to be very low or absent. This might make the use of these derivatives feasible in the prolonged therapy or prophylaxis of HIV infections.

Role of the glycopeptide framework in the antibacterial activity of hydrophobic derivatives of glycopeptide antibiotics

The antibacterial properties of glycopeptide antibiotics are based on their interaction with the d-Ala-d-Ala containing pentapeptide of bacterial peptidoglycan. The hydrophobic amides of vancomycin (1), teicoplanin (2), teicoplanin aglycon (3), and eremomycin (4) were compared with similar amides of minimally or low active des-(N-methyl-d-leucyl)eremomycin (5), eremomycin aglycon (6), des-(N-methyl-d-leucyl)eremomycin aglycon (7), and a teicoplanin degradation product TB-TPA (8). All hydrophobic amides of 1, 3, 4, and 6 were almost equally active against glycopeptide-resistant enterococci (GRE) [minimum inhibitory concentrations (MIC) <or= 4 microg/mL] and had better activity against Gram-positive strains sensitive to glycopeptides than against GRE. Extensive degradation of the glycopeptide framework in amides of 7 and 8 led to a decrease of anti-GRE activity (MIC = 16-64 microg/mL), and for these derivatives MIC values for bacterial strains sensitive and resistant to glycopeptides were very close. These results suggest that in sensitive bacteria two mechanisms of action are operating for the hydrophobic derivatives of glycopeptide antibiotics with the nondamaged peptide core-interaction with the d-Ala-d-Ala moiety and the inhibition of bacterial membrane bound enzymatic reactions, whereas for GRE lacking the d-Ala-d-Ala fragment, only the second mechanism is operating. It appears that a minimal glycopeptide core is required for activity, and that more extensive degradation results in a serious decrease of antibacterial activity.

Synthesis and mode of action of hydrophobic derivatives of the glycopeptide antibiotic eremomycin and des-(N-methyl-D-leucyl)eremomycin against glycopeptide-sensitive and -resistant bacteria

Des-(N-methyl-D-leucyl)eremomycin was obtained by Edman degradation of eremomycin. Derivatives with a hydrophobic substituent at the exterior of the molecule were then synthesized, and their antibacterial activities were compared with similar derivatives of eremomycin. Comparison of derivatives of eremomycin containing the n-decyl or p-(p-chlorophenyl)benzyl substituent in the eremosamine moiety (N') and n-decyl or p-(p-chlorophenyl)benzylamides with similar derivatives of eremomycin possessing the damaged peptide core (a defective binding pocket) showed that compounds of both types are almost equally active against glycopeptide-resistant strains of enterococci (GRE), whereas eremomycin derivatives are more active against staphylococci. Hydrophobic 7d-alkylaminomethylated derivatives of eremomycin (9, 10) demonstrated similar antibacterial properties. Since the basic mode of action of glycopeptide antibiotics involves binding to cell wall intermediates terminating in -D-Ala-D-Ala and this interaction is seriously decreased in the hexapeptide derivatives (lacking the critical N-methyl-D-leucine), we suggest that these hydrophobic derivatives may inhibit peptidoglycan synthesis in the absence of dipeptide binding. NMR binding experiments using Ac-D-Ala-D-Ala show that binding constants of these hexapeptide derivativies are decreased in comparison with the corresponding heptapeptides with intact binding pocket. This is in agreement with the decreased biological activity of the hexapeptide derivatives against vancomycin-sensitive strains in comparison with the activity of parent compounds. Binding to the lactate cell wall analogue Ac-D-Ala-D-Lac with decylamide of eremomycin 8 was not observed, demonstrating that the interaction with this target in GRE does not occur. While hydrophobic glycopeptide derivatives retain the ability to inhibit the synthesis of peptidoglycan in manner of natural glycopeptides, biochemical investigation supports the hypothesis that they inhibit the transglycosylase stage of bacterial peptidoglycan biosynthesis even in the absence of dipeptide or depsipeptide binding.

[The immunological consequences of congenital infections]

Mice of different strains were inoculated with type A influenza virus or Mycoplasma arthritidis in the second half of pregnancy. A part of the animals born after this inoculation were characterized by a sharp retardation of growth. The study of the immune status of such animals revealed that their proliferative response to mitogenic/superantigenic factors of the infective agents introduced during pregnancy was suppressed or absent, and the cells of their immune system began to recognize syngeneic intact stimulators in the mixed lymphocytes culture as heterogeneous ones. The spleen of the experimental animals was found to contain suppressor cells, both specific and nonspecific with respect to the infective agent. After inoculation with M. arthritidis areactivity was observed only in mice, sensitive to mycoplasmal superantigen. The data thus obtained suggest that the penetration of infecting agents producing mitogenic/superantigenic factors induced changes in the immune system, contributing to the persistence of the infective agent in the host body.

[The humoral immunity system of mice with experimental slow influenzal infection]

The status of the interferon system and level of immunoglobulins were studied in C57BL6 mice with slow influenza infection. These mice showed signs of immunosuppression: low endogenous interferon production, synthesis of alpha- and gamma-interferon by splenocytes of these mice in vitro 4-8 times lower than by those of the controls, lower levels of IgG in the blood serum. These data indicate general suppression of humoral immunity.

[The use of T-activin for the prevention of congenital influenzal infection in mice and the correction of the immune deficiency]

Viremia accompanying influenza infection and the possibility of transplacental passage of the virus into the fetus make it expedient to develop measures for the prophylaxis of intrauterine infection of the fetus in case of influenza during pregnancy. The work presents the optimum scheme of administration of T-activin for prophylactic purposes to pregnant mice with acute influenza infection. Besides, the use of T-activin for immunocorrection in case of established congenital influenza infection in mice is proposed.

[Characteristics of immune reactions to the influenza virus in mice with a slow influenzal infection]

It had previously been shown that intrauterine infection of mice with influenza virus resulted in growth retardation and significant immunosuppression to various nonspecific agents and influenza virus. The present study demonstrated that such mice also had lower production of specific antibody and reduced capacity to form the delayed hypersensitivity to influenza virus. Despite the lack of specific immune response, such mice had high levels of response to influenza virus in adoptive transfer. The reasons for which lymphocytes of mice with slow influenza infection fail to manifest their immunological potentials in situ require further study.

[Morphometric analysis of immunologic deficiency in newborn mice developing after transplacental transmission of live or inactivated influenza A virus]

Morphometric evaluation of the thymus and spleen was used to characterize the complex immunological deficiency in suckling mice developing as a result of transplacental transmission of both live and inactivated influenza virus.

[The role of suppressor cells in congenital influenza infection in mice]

Young mice with congenital influenza infection have lower immune responsiveness of lymphocytes to nonspecific mitogens and influenza virus antigens. Lymphocytes of such animals inhibit proliferation of normal lymphoid cells activated with concanavalin A and immune lymphocytes activated with influenza virus antigens. It is assumed that in congenital influenza infection one of the possible mechanisms of immunosuppression in mice is the activation of suppressor T-cells.

[Immunologic analysis of the pathology developing in mice as a results of intrauterine infection with the influenza virus]

The progency of C57BL/6 mice consisting of three groups: with signs of slow influenza infection ("dwarf"), "nude-like" resembling nude mice, and "nude-like" with spontaneous fur growth, was examined. The slow influenza infection in "dwarf" mice was found to be characterized by marked immunosuppression manifested by a sharp reduction of the number of antibody- and rosette-forming cells and blasttransformation of spleen lymphocytes into T- and B-mitogens. The most marked immuno-suppression was found in the "dwarfs" born to the females infected with the virus enriched with standard virions. "Nude-like" animals also had marked immunosuppression (particularly with regard to the rosette-formation), however, the "dwarfs" appeared to have more marked affection of B-cells as compared with "nude-like" mice. Gradual restoration of fur in a portion of "nude-like" animals (spontaneous growth) was due to sharp stimulation of immune responsiveness in them as manifested by a two-fold (as compared with the controls) increase in the number of antibody- and rosette-forming cells and normalization of spleen cell response to T- and B-mitogens. Differences between nude and "nude-like" mice consisting in the latter in the affection of not only T- but also B-link of immunity are discussed.

[Slow influenzal infection developing in the progeny of mice as a result of infection of the females during pregnancy]

Transplacental transmission of influenza virus from female mice infected during pregnancy may be detected as early as one day after virus inoculation, and the concentration of the infectious virus in fetal tissues is proportional to the infective dose. The intrauterine infection of fetuses leads to the development in a portion of progeny of slow influenza infection the frequency of which depends on the size of the dose used for inoculation of pregnant females. The slow influenza infection developed with similar effectiveness in the progeny of SHK colony mice and C57BL/6 line. As a result of influenza virus infection of pregnant C57BL/6 mice, there were specimens among their progeny devoid of body fur resembling the line of athymic nude mice. It is suggested that the birth of such nude mice is due to reversible changes in the thymus occurring under the influence of influenza virus.

[Experimental slow influenza infection in mice]

In baby mice born to mothers--virus carriers (surviving for various periods after intranasal administration of influenza virus), infectious persisting influenza virus in titres of 10(0.5) to 10(2.5) EID50/0.1 ml was found in the blood, lungs, livers, kidneys, spleens, and brains. Not infrequently, such animals developed a severe pathological process accompanied by growth retardation and characterized by progressive involvement of the hypothalamus, immunocompetent organs, endocrine system and always terminating by the death of the animals. Possible mechanisms of the described slow form of influenza infection are discussed.

[Possible ways of modeling latent influenzae infection in mice]

A latent influenza infection was produced experimentally in three ways: after experiencing the disease, after immunization with a live virus, as a result of vertical transmission of the virus persisting in females. In the latent influenza infection forming after the disease the duration of virus persistence was 112 days postinfection. The persisting virus from the animals receiving a single immunization was isolated only up to 35 days postinoculation. Both after the disease and immunization with a live virus the persisting infectious virus was found in the lungs in low titres not exceeding 1 lg EID50/0.2 ml. In contrast, a latent influenza infection in mice born to mothers-virus carriers was characterized by virus persistence in the blood and viscera in titres of 10(1) to 10(2) EID50/0.1 ml. Features of influenza virus persistence and conditions of its formation in mammals by the three ways mentioned are discussed.