Mohammad Shahrooei

Vaccination with SesC Decreases Staphylococcus epidermidis Biofilm Formation

ABSTRACT The increased use of medical implants has resulted in a concomitant rise in device-related infections. The majority of these infections are caused by Staphylococcus epidermidis biofilms. Immunoprophylaxis and immunotherapy targeting in vivo-expressed, biofilm-associated, bacterial cell surface-exposed proteins are promising new approaches to prevent and treat biofilm-related infections, respectively. Using an in silico procedure, we identified 64 proteins that are predicted to be S. epidermidis surface exposed (Ses), of which 36 were annotated as (conserved) hypothetical. Of these 36 proteins, 5 proteins—3 LPXTG motif-containing proteins (SesL, SesB, and SesC) and 2 of the largest ABC transporters (SesK and SesM)—were selected for evaluation as vaccine candidates. This choice was based on protein size, number of antigenic determinants, or the established role in S. epidermidis biofilm formation of the protein family to which the candidate protein belongs. Anti-SesC antibodies exhibited the greatest inhibitory effect on S. epidermidis biofilm formation in vitro and on colonization and infection in a mouse jugular vein catheter infection model that includes biofilms and organ infections. Active vaccination with a recombinant truncated SesC inhibited S. epidermidis biofilm formation in a rat model of subcutaneous foreign body infection. Antibodies to SesC were shown to be opsonic by an in vitro opsonophagocytosis assay. We conclude that SesC is a promising target for antibody mediated strategies against S. epidermidis biofilm formation.

Inhibition of Staphylococcus epidermidis Biofilm Formation by Rabbit Polyclonal Antibodies against the SesC Protein

ABSTRACT Several well-studied proteins with defined roles in Staphylococcus epidermidis biofilm formation are LPXTG motif-containing proteins. Here, we investigate the possible use of the LPXTG motif-containing protein SesC (S. epidermidis surface protein C; accession no. NP_765787) as a target for antibodies to prevent biofilm formation. In vitro and in a in vivo rat model of catheter infection, gene and protein expression analysis showed that SesC is expressed more strongly in biofilm-associated cells than in planktonic cells and is expressed particularly during the late phase of in vivo biofilm formation. Polyclonal rabbit antibodies raised against SesC reduced the fibrinogen-binding ability of S. epidermidis RP62A and Staphylococcus aureus RN4220 transformants expressing SesC, inhibited in vitro biofilm formation by S. epidermidis strains 10b and 1457, and significantly reduced the numbers of bacteria in a 1-day-old in vivo biofilm (P < 0.001, one-way analysis of variance). Our findings revealed that SesC is a promising target for prevention and treatment of S. epidermidis biofilms because it affects both the primary attachment and biofilm accumulation phases. The precise role of SesC in biofilm formation remains to be identified.

Immunoprophylaxis and immunotherapy of Staphylococcus epidermidis infections: challenges and prospects.

Previously considered a human commensal, Staphylococcus epidermidis is a frequent cause of nosocomial infections and the most common cause of device-related infections. Because the expression of toxins and other obvious virulence factors is less in S. epidermidis, the biofilm-forming capacity is its major virulence factor. Biofilm growth is characterized by high resistance to antimicrobial agents and host immune responses, making biofilm eradication tremendously difficult. The increasing prevalence of multidrug-resistant S. epidermidis strains additionally hampers antimicrobial therapy. Therefore, immunoprophylaxis and immunotherapy targeting factors expressed at some point in biofilm formation might offer new tools to combat S. epidermidis infections. So far, a limited number of targets have been examined for their immunotherapeutic potential. In this review, we focus on the already tested and possible targets for vaccine development, discuss the accompanying challenges and speculate on future possibilities with respect to immunotherapeutic solutions to deal with S. epidermidis infections.

The Possible Role of Staphylococcus epidermidis LPxTG Surface Protein SesC in Biofilm Formation

Staphylococcus epidermidis is the most common cause of device-associated infections. It has been shown that active and passive immunization in an animal model against protein SesC significantly reduces S. epidermidis biofilm-associated infections. In order to elucidate its role, knock-out of sesC or isolation of S. epidermidis sesC-negative mutants were attempted, however, without success. As an alternative strategy, sesC was introduced into Staphylococcus aureus 8325–4 and its isogenic icaADBC and srtA mutants, into the clinical methicillin-sensitive S. aureus isolate MSSA4 and the MRSA S. aureus isolate BH1CC, which all lack sesC. Transformation of these strains with sesC i) changed the biofilm phenotype of strains 8325–4 and MSSA4 from PIA-dependent to proteinaceous even though PIA synthesis was not affected, ii) converted the non-biofilm-forming strain 8325–4 ica::tet to a proteinaceous biofilm-forming strain, iii) impaired PIA-dependent biofilm formation by 8325–4 srtA::tet, iv) had no impact on protein-mediated biofilm formation of BH1CC and v) increased in vivo catheter and organ colonization by strain 8325–4. Furthermore, treatment with anti-SesC antibodies significantly reduced in vitro biofilm formation and in vivo colonization by these transformants expressing sesC. These findings strongly suggest that SesC is involved in S. epidermidis attachment to and subsequent biofilm formation on a substrate.

Novel Mutation of ZAP-70-related Combined Immunodeficiency: First Case from the National Iranian Registry and Review of the Literature

ABSTRACT ZAP-70 deficiency is a rare autosomal recessive form of combined immunodeficiency (CID) characterized by selective absence of circulating CD8 T cells with low, normal, or increased CD4 T cells in peripheral blood. Up to now, 14 unique mutations in the ZAP70 gene have been identified in patients with ZAP-70-related CID. We present a 3-year-old boy with a history of recurrent bacterial infections and autoimmunity. Initial laboratory findings showed a normal total lymphocyte count, but low levels of CD8 and CD4 T cells and an abnormal lymphocyte proliferation response. Immunoglobulin levels were normal, but the specific antibody response was impaired. Whole exome sequencing revealed a mutation within the kinase domain of ZAP-70. ZAP-70 deficiency should be considered in infants and young children with recurrent bacterial infections, in spite of having palpable lymph nodes, a notable thymus shadow, and a normal total lymphocyte count.

Aggregating sequences that occur in many proteins constitute weak spots of bacterial proteostasis

Aggregation is a sequence-specific process, nucleated by short aggregation-prone regions (APRs) that can be exploited to induce aggregation of proteins containing the same APR. Here, we find that most APRs are unique within a proteome, but that a small minority of APRs occur in many proteins. When aggregation is nucleated in bacteria by such frequently occurring APRs, it leads to massive and lethal inclusion body formation containing a large number of proteins. Buildup of bacterial resistance against these peptides is slow. In addition, the approach is effective against drug-resistant clinical isolates of Escherichiacoli and Acinetobacterbaumannii, reducing bacterial load in a murine bladder infection model. Our results indicate that redundant APRs are weak points of bacterial protein homeostasis and that targeting these may be an attractive antibacterial strategy.Aggregation is sequence-specific and nucleated by short aggregating protein segments (APR). Here authors use a multidisciplinary approach to show that in E.coli some frequently occurring APRs lead to protein aggregation and ultimately bacterial cell death, which could serve as antibacterial strategy.

Different Immunological Pathways Underlie the Immune Response to Pneumococcal Polysaccharides

Measurement of the antibody response to Pneumovax®/ Pneumo23®, a 23-valent pneumococcal polysaccharide vaccine, is an established method to evaluate B cell function. Such evaluation typically involves measurement of preand post-vaccination serotype-specific antibody levels. It is generally believed that the immune response to pneumococcal polysaccharides is MHC class II-independent. This is based on the observation that various polysaccharides (including pneumococcal polysaccharides) do not bind to MHC class II molecules (explaining the Tcell independence of polysaccharide antigens) and that MHC class II-deficient mice mount antibodies to the T cell-independent antigens dextran, phosphorylcholine, and levan [1, 2]. However, emerging evidence suggests that bacterial zwitterionic polysaccharides (which carry positively and negatively charges within one unit) are processed to low molecular weight carbohydrates and presented to T cells through the MHC class II endocytic pathway [3]. Examples of zwitterionic polysaccharides include polysaccharide A from Bacteroides fragilis and Streptococcus pneumoniae serotype 1 (most other pneumococcal polysaccharides are anionic) [3]. Although it is well recognized that the immune response to pneumococcal polysaccharides is complex and serotype dependent, little attention has been given to the difference between major histocompatibility complex class II (MHC class II)-dependent and MHC class II-independent pathways. In this letter, we illustrate that the immune response to the zwitterionic pneumococcal serotype 1 differs from the immune response to a non-zwitterionic (e.g., anionic) pneumococcal serotype (serotype 3 or serotype 4). In a first step, we immunized MHC class II knockout mice and control mice with Pneumo23® and measured the antibody response to serotype 1, serotype 3, and serotype 4. We found thatMHC class II knockout micemounted antibodies to serotype 3 but failed to do so (p < 0.0001) for serotype 1 (Fig. 1a), thereby confirming that the immune response to the zwitterionic serotype 1 is MHC class II-dependent. Neither wild type nor MHC class II knockout mice mounted detectable antibodies to serotype 4. Next, we evaluated the immune response to Pneumo23® in an 18-year-old MHC class II-deficient patient and in three controls. This patient has homozygous RFXANK deletion [4] and developed chronic bronchiectasis. He receives intravenous immunoglobulin substitution and prophylactic cotrimoxazole (P35 in [4]). Because the patient received immunoglobulin substitution, the immune response was evaluated by quantification of the antibody secreting cells (by ELISPOT) 7 days after vaccination. Antibodies to serotype 1 and serotype 4 were quantified (serotype 3 could not be reliably coated on the ELISPOT plates). In the MHC class II* Xavier Bossuyt xavier.bossuyt@uzleuven.be

Whole exome sequencing identifies both nuclear and mitochondrial variations in an Iranian family with non-syndromic hearing loss

Genetic contributing factors to non-syndromic hearing loss (NSHL) are remarkably diverse spanning over autosomal to X-linked to mitochondrial inheritance patterns. Facing a quite unconventional pedigree, here we report implementation of whole exome sequencing (WES) to uncover mitochondrial pathogenic variant in a six-generation Iranian family with four cases affected with hereditary NSHL of variable severity. As a result, heteroplasmic transition of A to G at position 1555 of MT-RNR1 gene was identified in all affected individuals co-existing with nuclear c.28G > T (p.A10S) variant in the TRMU gene, only in some patients. The reliability of WES to infer nuclear as well as mitochondrial variants in hearing loss were discussed.

Ses proteins as possible targets for vaccine development against Staphylococcus epidermidis infections

OBJECTIVES The opportunistic pathogen Staphylococcus epidermidis is progressively involved in device-related infections. Since these infections involve biofilm formation, antibiotics are not effective. Conversely, a vaccine can be advantageous to prevent these infections. In view of vaccine development, predicted surface proteins were evaluated on their potential as a vaccine target. METHODS Immunoglobulins directed against S. epidermidis surface proteins SesB, M, O, Q and R were used to firstly affirm their surface location. Further, inhibitory effects of these IgGs on biofilm formation were determined in vitro on polystyrene and polyurethane surfaces and in vivo using a subcutaneous catheter mouse model. We also examined the opsonophagocytotic capacity of these IgGs. RESULTS Surface localization of the five Ses proteins was demonstrated both for planktonic and sessile cells, though to a variable extent. Ses-specific IgGs added to planktonic cells had a variable inhibitory effect on cell adhesion to polystyrene, while only anti-SesO IgGs decreased cell attachment to polyurethane catheters. Although phagocytic killing was only obtained after opsonization with SesB-specific IgGs, a significant reduction of in vivo formed biofilms was observed after administration of SesB-, SesM- and SesO-specific IgGs. CONCLUSIONS Regardless of their characterization or function, S. epidermidis surface proteins can be adequate targets for vaccine development aiming the prevention of device-related infections caused by invasive S. epidermidis strains.

X-linked hyper-IgM syndrome associated with pulmonary manifestations: A very rare case of functional mutation in CD40L gene in Iran

Hyper IgM (HIGM) syndromes are a complex of primary immunodeficiency disorders. A 4-years-old boy with recurrent fever and chills, dyspnea, sort throat for a month was admitted to emergency department. In the current case, whole exome sequencing followed by Sanger sequencing were employed in order to screen probable functional mutations. Molecular analysis revealed a functional mutation across the CD40L gene (NM_000074: exon5: c.T464C) resulted in amino acid change p.L155P attributed to X-linked hyper IgM syndrome. The findings of the current study signify the critical role of microbial infection as well as XHIGM screening, particularly in those children cases with respiratory symptoms.