Inactivation of DNA-Binding Response Regulator Sak189 Abrogates β-Antigen Expression and Affects Virulence of Streptococcus agalactiae

BACKGROUND: Streptococcus agalactiae is able to colonize numerous tissues employing different mechanisms of gene regulation, particularly via two-component regulatory systems. These systems sense the environmental stimuli and regulate expression of the genes including virulence genes. Recently, the novel two-component regulatory system Sak188/Sak189 was identified. In S. agalactiae genome, it was adjacent to the bac gene encoding for beta-antigen, an important virulence factor. METHODOLOGY/PRINCIPAL FINDINGS: In this study, the sak188 and sak189 genes were inactivated, and the functional role of Sak188/Sak189 two-component system in regulation of the beta-antigen expression was investigated. It was demonstrated that both transcription of bac gene and expression of encoded beta-antigen were controlled by Sak189 response regulator, but not Sak188 histidine kinase. It was also found that the regulation occurred at transcriptional level. Finally, insertional inactivation of sak189 gene, but not sak188 gene, significantly affected virulent properties of S. agalactiae. CONCLUSIONS/SIGNIFICANCE: Sak189 response regulator is necessary for activation of bac gene transcription. It also controls the virulent properties of S. agalactiae. Given that the primary functional role of Sak188/Sak189 two-component systems is a control of bac gene transcription, this system can be annotated as BgrR/S (bacgene regulatory system)

СОВРЕМЕННЫЕ ПОДХОДЫ И ТЕХНОЛОГИИ В ИНФЕКЦИОННОЙ ЭПИДЕМИОЛОГИИ (НА ПРИМЕРЕ ИНФЕКЦИЙ, ВЫЗЫВАЕМЫХ ПАТОГЕННЫМИ СТРЕПТОКОККАМИ)

The present review is based on the long term researches done at the Department of Molecular Microbiology, Research Institute of Experimental Medicine and devoted to molecular identification and characterization of pathogenic streptococci, mainly Streptococcus pyogenes and Streptococcus agalactiae. In it the basic approaches and technologies the evaluation of microbiological aspects of wide-spread streptococcal infection epidemiology were described and considered. The special attention was given to the genetic heterogeneity of causative strains at the gene and genomic levels and to their genotyping. Also, the essential role of mobile genetic elements (temperate phages, plasmids, transposons, pathogenic islands and insertion sequences) in differentiation of streptococci and analysis of their pathogenic properties were determined. Interrelation between enotypes of species and their pathogenic potentiality was traced. Some proposals were developed to improve an official registration of streptococcal diseases and their complications as well as diagnostic abilities for them.Данный обзор составлен на основании опыта многолетних исследований отдела молекулярной микробиологии НИИЭМ РАМН по молекулярной идентификации и характеристике патогенных стрептококков, Streptococcus pyogenes и Streptococcus agalactiae. В нем изложены современные подходы и технологии оценки бактериального звена в эпидемиологии широко распространенных стрептококковых заболеваний. Основное внимание уделено генетическому разнообразию возбудителей на генном и геномном уровнях, их генотипированию и роли мигрирующих генетических элементов (умеренные фаги, транспозоны, встраивающиеся последовательности, острова патогенности, плазмиды) в дифференцировке стрептококков и в анализе распространенности признаков болезнетворности. Прослежена взаимосвязь между генотипом возбудителя и вызываемой им патологией. Выдвинуты предложения по учету форм стрептококковых инфекций и регламентированию диагностических средств и подходов

MDC/CCL22 depletion in COVID-19 and post-COVID

In this article, we explore the role of macrophage-derived chemokine (MDC/CCL22) in COVID-19 immunity. The study included plasma samples of 289 patients with PCR-verified COVID-19 from specialized hospitals. The blood samples were collected at admission, approximately 7 days after the start of infection. Genetic testing of the virus was performed in nasopharyngeal swabs to determine the viral strain for each patient. We also included blood plasma of 69 convalescent patients who had recovered from COVID-19 more than a month prior to the study. Additionally, 51 healthy donors were included in the study as controls. The concentrations of MDC/CCL22 and other cytokines and chemokines were measured with multiplex analysis using Luminex MagPix Technology. The results showed that COVID-19 patients had significantly lower MDC levels in their plasma, regardless of the SARS-CoV-2 strain, compared to healthy donors. This finding suggests that MDC/CCL22 depletion may play a role in COVID-19 immunity. Furthermore, convalescent patients still showed decreased concentrations of MDC/CCL22 more than a month after infection, indicating that this depletion may persist even after recovery. We propose two mechanisms that can explain the reasons leading to MDC/CCL22 depletion. The first is binding and inactivation of this chemokine with SARS-CoV-2 peptides, making it not only undetectable for commercial kits, but also less functionally active. Another mechanism is the dysfunction of its effector cells (e.g., DCs and macrophages). Lymphopenia following COVID-19 can potentially be explained by the absence of MDC/CCL22. This may lead to a shift towards hyperactivation in the inflammatory response, potentially explaining the severity of COVID-19. This research sheds light on the importance of MDC/CCL22 in COVID-19 immunity and highlights the need for further investigation into its role in the disease. Understanding the mechanisms behind MDC/CCL22 depletion could provide new insights into the pathogenesis of COVID-19 and inform the development of potential treatments

Streptococcus pyogenes: phenomenon of nonimmune binding of human immunoglobulins and its role in pathology

M and M-like proteins represent the main pathogenicity factors of Streptococcus pyogenes, a widely spread and potentially lethal bacterial pathogen. These proteins provide resistance of the microbe to innate and adaptive immune response, due to attraction of specific human proteins to the streptococcal surface. Nonimmune binding of immunoglobulins G (IgG) and A (IgA) via their Fc domains to M and M-like proteins was described over 40 years ago, but its role for the pathogenicity of Streptococcus pyogenes is far from definite resolution. The discovery of this phenomenon should be considered among quite significant achievements of modern microbiology, since it had a huge impact upon development of innovative approaches, technologies and tools for microbiological, immunological and molecular diagnostics. It also promoted fundamental studies in pathogenesis of distinct infectious states and their complications caused by S. pyogenes. The non-immune binding of host immunoglobulins was previously suggested to be important mainly in immune conditions on the surface of mucous membranes and their secretions, but not in blood plasma, whereas other studies have pointed to significance of this phenomenon in protecting microbes from phagocytosis in non-immune blood of the host. It was also shown that the effect of Fc-binding causes increased pathogenicity of streptococci both in primary focus of infection, and during chronical course of the process, thus contributing to development of autoimmune diseases caused by S. pyogenes infection and leading to tissue damage in experimental animals. The experimental autoimmune process can be prevented by administering purified Fc fragments of immunoglobulins to the animals, blocking this process at the early stages of its development. A significant place in pathogenesis of IgA nephropathy (IgAN) belongs to streptococcal diseases. IgAN has been described as a mesangial proliferative process, due to initial IgA-Fcα deposition in renal mesangium cells. The data from literature describe successful modeling of individual IgAN traits, and expand our understanding of pathogenic properties and functions of Fcα binding receptor M proteins of S. pyogenes. The data reviewed in the article also presume the relevance of recently proposed ideas about an important role of non-immune Ig binding in streptococcal diseases, even in cases that differ in their development mechanism. These studies, including possible search for tools and techniques of preventive and potentially therapeutic applications, require additional efforts to study the binding of Fc fragments of IgG and IgA to M and M-like proteins of Streptococcus pyogenes

Dynamics of B-Cell Populations in CSF and Blood in Patients Treated with a Combination of Rituximab and Mitoxantrone.

Background. Mitoxantrone (MTX) and Rituximab (RTX) are successfully used for treatment of multiple sclerosis (MS) and can be combined to increase efficacy. Objective. We used MTX, RTX, and methylprednisolone in a single combined regiment and observed patients prospectively. Methods. We present results of observational pilot study of combined therapy of RTX and MTX in 28 patients with active MS. Therapeutic protocol consisted of two infusions within 14 days. First infusion was 1000 mg methylprednisolone (MP) IV, 1000 mg RTX IV, and 20 mg MTX IV. On day 14, 1000 mg MP IV and 1000 mg RTX IV were given. Patients were followed prospectively from 12 to 48 months. Results and Conclusion. There were no relapses among all 28 patients during the observation period. B-cell depletion of CD19+ and CD19+/CD27+ memory B-cell subpopulation in both compartments was confirmed in all patients at 6 months. We found a more rapid reconstitution of B cells in the CSF than in the peripheral blood and longstanding depression of CD19+CD27+ memory B-cell. Conclusion. Effectiveness of combined regimen of RTX and MTX could be related to longstanding depletion of CD19+CD27+ memory B-cell subset

Impact of IgG Fc-fragments on experimental glomerulonephritis induced by <i>Streptococcus pyogenes</i> strain binding various immunoglobulin classes

The pathogenesis of poststreptococcal glomerulonephritis (PSGN), a major complication of acute infections caused by group A streptococci (GAS) remains unclear. Several theories, based on the role of certain streptococcal virulence factors, as well as immunological mimicry between GAS and renal tissue, have been proposed. Earlier, we reported that many virulent clinical GAS isolates showing confirmed nephritogenic activity were capable of nonimmune Fc binding of monomeric or aggregated IgG. Moreover, a rabbit model of PSGN allowed to obtain findings regarding a crucial role of streptococcal IgG Fc binding proteins belonging to the M family surface proteins, in the onset of PSGN. Rabbits injected with inactivated IgGFcBP-positive streptococci, acquired changes in the renal tissue with deposited IgG and complement C3, as well as signs of immune inflammation characteristic for human PSGN. Also, it was shown that the induction of experimental glomerulonephritis could be inhibited after normal IgG or its purified Fc fragments were inoculated at early stages of the process. The data obtained in rabbits injected with group A streptococcal type M60 also showed pathogenic functions of the IgA Fc-binding proteins of GAS. The aim of the study was to examine inhibiting activity of the purified rabbit IgG Fc fragments on the manifestations of glomerulonephritis induced by S. pyogenes strains capable of binding diverse forms of immunoglobulins such native IgG, immune complexes, and IgA.Materials and methods. GAS strains of emml, emml2 and emm60 genotypes were used to induce PSGN or IgA-nephropa-thy in rabbits. Fc fragments derived from rabbit IgG were obtained by enzymatic digestion and purified by affinity chromatography on a protein G-sepharose FF column. Immunomorphological changes of renal tissue were estimated by morphometric analysis.Results. In the present study, using the rabbit model, we revealed pathological changes of different intensity and localization in the renal tissue. For streptococci of the emm1 and emm12 genotypes, PSGN was characterized by deposition of IgG or IgG-anti-IgG immune complexes within the basal glomerular membrane. Morphological changes were evaluated as a membranous-proliferative glomerulonephritis. Meanwhile, IgA-glomerulonephritis is characterized by deposition of IgA in mesangial cells of glomeruli, leading to the mesangial-proliferative glomerulonephritis or IgA-nephropathy. Intravenously administered purified Fc fragments derived from normal rabbit IgG varied in effects on pathological processes: (i) IgG Fc fragments of fully inhibited development of the PSGN induced by IgG Fc binding strain of emml genotype, (ii) IgG Fc fragments of partially reverted changes caused by the emm12 genotype strain, which was binding only to immune complexes, and (iii) had no effects on pathological changes caused by the emm60 genotype GAS strain, which was binding only IgA.Conclusion. The data obtained point and emergence of differences in mechanisms of renal lesions development at glomerulonephritis, depending on the emm genotype of GAS strain. In addition, it also confirmed GAS-derived involvement for various IgFc-receptor proteins in the pathology. Further studies on potential prophylactic or curative effects of IgG Fc fragments in PSGN should therefore be of interest. The findings might suggest a new therapeutic approach for non-suppurative poststreptococcal diseases

A role of streptokinase in experimental post-streptococcal glomerulonephritis

Post-streptococcal glomerulonephritis (PSGN) refers to the sequela of the acute infection, caused by Streptococcus pyogenes (group A streptococcus, GAS). This pathology has been studied for a long time, and today attempts are being made to identify the products of their life activity, able to initiate an immunopathological process in kidneys. Most attention has been paid to streptokinase, the enzyme transforming blood plasminogen into plasmin, capable, together with the plasmin receptor (NAPlr), of damaging the glomerular tissue, as well as activating the complement system. The aim of the study was to consider two tasks: to study the ability of the GAS-obtained enzyme to transform plasminogen of different species into plasmin as well as to study its role in the development of PSGN in rabbits having subcutaneously implanted tissue chambers. The animals were infected by inoculating GAS cultures into the chambers. Materials and methods. GAS strains of M types 1, 12, 22 and their ska– isogenic mutants were used in the study. Purified plasminogen preparations were isolated from fresh human, rabbit or mouse plasma by using chromatographic column with Lysine Sepharose 4B. To reveal the ability of streptokinase to activate plasminogen into plasmin, its preparation at a concentration of 1 mg/ml was added to 10 ìg of purified human, rabbit or mouse plasminogen. The concentration of plasmin was defined photometrically using S-2251 (Chromogenix, USA). To reproduce PSGN, four chambers were implanted under the skin in each rabbit; after the complete wound healing animals were infected and observed for three weeks. On day 14, the animals were treated with benzylpenicillin. The kidneys from survived rabbits were subjected to immunohistology analysis. Results. During in vitro experiments, M1, M12 and M22 GAS streptokinase showed distinct functional activity on human plasminogen, transforming it into plasmin: optical density indicators at ë = 405 nm were 0.4–0.7 compared with the negative control (ОD &lt; 0.001). Streptokinase did not activate mouse plasminogen (ОD = 0.001) and exerted quite a weak effect on transformation of the rabbit plasminogen into plasmin (ОD = 0.002). In experiments on PSGN induction in rabbits, we failed to detect streptokinase involvement, because no differences between initiation of glomerulonephritis by wild strains or ska– isogenic mutants were identified. Mutant strains deficient in the gene responsible for streptokinase synthesis but retained ability to bind rabbit and human IgG, caused morphological changes in kidney tissue, specific for PSGN. In addition, a comparative analysis of PSGN “rabbit” and “mouse” models developed by the same technology, was carried out and led to opposing conclusions regarding a role of streptokinase in pathogenesis of experimental glomerulonephritis. The role of IgG Fc-binding activity of GAS in development of experimental PSGN is discussed

Determination of reference values for TREC and KREC in circulating blood of the persons over 18 years

Increasing attention is being paid to methods for detecting primary and secondary T and/or B cell immunodeficiencies. Their implementation into laboratory diagnostics would contribute to the early diagnostics of immunodeficiencies. Currently, the number of identified adult patients with immunodeficiencies of various origins is steadily increasing. Age, gender and ethnicity of patients may be significant factors of immunity. Hence, determination of the population reference intervals for TREC and KREC DNA excision rings in peripheral blood of adult persons is an urgent laboratory task for in-depth examination of both congenital and acquired immunodeficiency conditions. Our purpose was to determine the reference intervals for the quantitative assay of TREC and KREC fragments in peripheral blood among the adult population of St. Petersburg. We studied whole blood samples obtained from 717 apparently healthy volunteers aged 18 to 108 years within the program of population immunity assessment among residents of St. Petersburg. The exclusion criterion included immunodeficiency of any origin, viral hepatitis A, B, C, HIV infection. Quantitation of the target TREC and KREC DNA fragments was carried out using a set of reagents for the quantitative determination of excisional rings TREC and KREC by Real-time PCR (TREC/KREC-AMP PS). The reference intervals were determined by the direct method according to the recommendations of the International Federation of Clinical Chemistry and the Russian State Standard (GOST) R 53022.3-2008. The volunteers were divided into six age groups: 18-29, 30-39, 40-49, 50-59, 60-69 years old, and the persons over 70. The amounts of TREC and KREC in each blood sample were determined for all age groups. Upon correlation analysis, we have revealed a negative relationship between the concentration of TREC molecules in blood samples, and the age of study participants (Spearman correlation coefficient r = -0.80 (p-value &lt; 0.0001)). Significant differences in TREC levels between different age groups were revealed. No correlations were detected between KREC contents in blood samples and age as well as any differences between age groups. Reference intervals of the TREC level were determined for each mentioned age group. A unified reference range was established for the KREC levels. The established reference intervals for TREC and KREC molecules in adults are significantly lower than in newborns. The obtained results enable determination of reference intervals for TREC and KREC levels among adults, thus contributing to effective personalized laboratory diagnosis of immunodeficiency states of various origins

Analysis of blood plasma cytokine profile in healthy residents of the Republic of Guinea

The cytokine system is a large group of humoral factors  produced by immune cells and involved in the  pathogenesis of most  human diseases.  To assess the  significance of changes  in cytokines/chemokines under  pathological conditions, appropriate reference values are required for healthy  people.  As known  from existing literature, most studies of various cytokine/chemokine concentrations in blood plasma were performed in healthy  subjects from Western Europe and North America.  Certain inter-population differences are known, with  respect  to production of distinct cytokines in different  racial  and  national groups.  Only  single studies concern normal levels of distinct cytokines in blood  plasma  of healthy  African  residents. The purpose  of this study was to determine the blood plasma cytokine profile in healthy  residents of the Republic of Guinea (RG), and to establish normal cytokine values.We have  examined 24  healthy  RG  residents and  23  residents of St.  Petersburg. Concentrations  of 40 cytokines/chemokines were determined in blood plasma.  The study was performed using multiplex analysis by xMAP technology.The  following  cytokine/chemokine levels  were  significantly   increased in  the  blood  plasma  of the  RG residents: IFNγ, IL-2, IL-4, IL-6, IL-10, TNFα, CCL1/I-309, CCL3/MIP-1α, CCL7/MCP-3, CCL17/ TARC, CCL19/MIP-3β,  CCL20/MIP-3α,  CCL21/6Ckine, CXCL2/Gro-β,  CXCL5/ENA-78, CXCL6/ GCP-2, CXCL9/MiG, CX3CL1/Fractalkine (р &lt; 0.001).  For  the  CCL8/MCP-2, CCL22/MDC, CXCL1/ Gro-α and CXCL12/SDF-1α+β chemokines a trend for increased concentration was revealed, in comparison with residents of St. Petersburg (р &lt; 0.05). Moreover, the levels of CCL23/MPIF-1 and MIF were significantly lower (р &lt; 0.0001) in the RG residents. There was a tendency for decreased levels (р &lt; 0.05) for CCL2/MCP-1 and CCL24/Eotaxin-2 chemokines in blood plasma taken from RG residents. There were no differences in levels of cytokines/chemokines for the studied  groups: GM-CSF, IL-1β, IL-16, CCL11/Eotaxin, CCL13/MCP-4, CCL15/Leukotactin-1, CCL25/TECK, CCL26/Eotaxin-3, CCL27/CTACK, CXCL8/IL-8, CXCL10/IP-10, CXCL11/I-TAC, CXCL13/BCA, and  CXCL16/SCYB16. Hence, this study  has presented for the  first time the normal limits for a wide range of cytokines/chemokines in blood plasma  of the African inhabitants. Interpopulation differences were found, including those  for constitutive chemokines. Different levels of CCL19/ MIP-3β and CCL21/6Ckine chemokines (the CCR7 receptor ligands) for the two populations may indirectly indicate the physiological features of T-cell maturation. Increased levels of CXCR2 receptor ligands in the blood plasma  of Guineans, i.e.,  CXCL2/Gro-β, CXCL5/ENA-78 and  CXCL6/GCP-2, may be due  to additional function of these chemokines as ligands for atypical DARC chemokine receptor, which neutralizes chemokines from the blood flow, whereas 95% of West Africans have mutations in the DARC gene and do not express this receptor. Increased levels of proinflammatory IL-6  and TNFα cytokines, and chemokine CCL20/MIP-3α in blood plasma  from RG  residents may suggest inflammatory processes  in the liver, since 100% of the examined Guineans had antibodies against the hepatitis A virus, 48% had antibodies to hepatitis B virus (anti-HBs), and 12% had antibodies against hepatitis C virus. In summary, the differences in cytokine/chemokine level may be related  to specific environment, circulation of infectious diseases, composition of intestinal, skin and mucosal microbiota, as well as distinct genetic  features

ROLE OF CXCR3 CHEMOKINE RECEPTOR AND ITS LIGANDS IN CERTAIN DISEASES

Chemokines are a special family of cytokines whose main function is to control cell migration; they are key players in the innate and adaptive immune responses. Directed chemotaxis of specific leukocyte subpopulations is necessary not only to maintain homeostasis, but also in development of some immunopathological conditions such as cancer, inflammation, infection, allergies and autoimmune disorders. Chemokines are pleiotropic molecules that are involved in physiological and pathophysiological processes. For example, the CXCR3 chemokine receptor is expressed on various cells: activated T and B lymphocytes, natural killers, eosinophils and neutrophils, dendritic cells, fibroblasts, endothelial and epithelial cells. Hence, CXCR3 and its ligands have a wide range of functional activity. CXCR3 ligands are the IFNγ-induced chemokines: CXCL9, CXCL10, CXCL11, and platelet-derived chemokines: CXCL4, CXCL4L1. All the CXCR3 ligands share common angiostatic properties due to lack of the Glu-Leu-Arg (ELR) motif. IFNγ-induced ligands of the CXCR3 are proinflammatory chemokines, they mainly recruit activated T cells and exert an effect on T cell polarization. Due to wide spectrum of biological activity, the ligands of CXCR3 receptor are involved in pathogenesis of various disorders, such as inflammation, infection, cancer, allergies and autoimmune disorders. In this review, we discuss the role of CXCR3 ligands in immunopathogenesis of various diseases, including the results of our studies in chronic hepatitis C, rheumatoid arthritis and pulmonary tuberculosis. Moreover, we have also discussed the potential laboratory diagnostic applicability of the chemokines in various diseases. This review illustrates a universal role of IFNγ-induced chemokines as mediators of immune responses in various diseases. The studies of CXCR3 ligands, their isoforms and receptors, interactions between themselves and with their receptors can provide a significant contribution to our understanding of the chemokine network. Understanding the system of IFNγ-dependent chemokines may have clinical implications, both for diagnostic tasks, and for therapeutic purposes