Search

Staphylococcus aureus is a significant bacterial pathogen in both community and hospital settings, and the escalation of antimicrobial‐resistant strains is of immense global concern. Vaccination is an inviting long‐term strategy to curb staphylococcal disease, but identification of an effective vaccine has proved to be challenging. Three well‐characterized, ubiquitous, secreted immune evasion factors from the staphylococcal superantigen‐like (SSL) protein family were selected for the development of a vaccine. Wild‐type SSL3, 7 and 11, which inhibit signaling through Toll‐like receptor 2, cleavage of complement component 5 and neutrophil function, respectively, were successfully combined into a stable, active fusion protein (PolySSL7311). Vaccination of mice with an attenuated form of the PolySSL7311 protein stimulated significantly elevated specific immunoglobulin G and splenocyte proliferation responses to each component relative to adjuvant‐only controls. Vaccination with PolySSL7311, but not a mixture of the individual proteins, led to a > 102 reduction in S. aureus tissue burden compared with controls after peritoneal challenge. Comparable antibody responses were elicited after coadministration of the vaccine in either AddaVax (an analog of MF59) or an Alum‐based adjuvant; but only AddaVax conferred a significant reduction in bacterial load, aligning with other studies that suggest both cellular and humoral immune responses are necessary for protective immunity to S. aureus. Anti‐sera from mice immunized with PolySSL7311, but not individual proteins, partially neutralized the functional activities of SSL7. This study confirms the importance of these SSLs for the survival of S. aureus in vivo and suggests that PolySSL7311 is a promising vaccine candidate. [ABSTRACT FROM AUTHOR]

The conserved diagonal docking mode observed in structures of T-cell receptors (TCRs) bound to peptide-MHC ligands is believed to reflect coevolution of TCR and MHC genes. This coevolution is supported by the conservation of certain interactions between the germline-encoded complementarity-determining region (CDR)1 and CDR2 loops of TCR and MHC. However, the rules governing these interactions are not straightforward, even when the same variable (V) region recognizes the same MHC molecule. Here, we demonstrate that the somatically generated CDR3 loops can markedly alter evolutionarily selected contacts between TCR and MHC ("CDR3 editing"). To understand CDR3 editing at the atomic level, we determined the structure of a human melanoma-specific TCR (G4) bound to the MHC class II molecule HLA-DR1 and an epitope from mutant triose phosphate isomerase (mutTPI). A comparison of the G4-mutTPI-DR1 complex with a complex involving a TCR (E8) that uses the same Vα region to recognize the same mutTPI-DR1 ligand as G4 revealed that CDR1α adopts markedly different conformations in the two TCRs, resulting in an almost entirely different set of contacts with MHC. Based on the structures of unbound G4 and E8, the distinct conformations of CDR1α in these TCRs are not induced by binding to mutTPI-DR1 but result from differences in the length and sequence of CDR3α that are transmitted to CDR1α. The editing of germline-encoded TCR-MHC interactions by CDR3 demonstrates that these interactions possess sufficient intrinsic flexibility to accommodate large structural variations in CDR3 and, consequently, in the TCR-binding site. [ABSTRACT FROM AUTHOR]

Excess growth hormone (GH) has been implicated in multiple cancer types and there is increasing interest in the development of therapeutic inhibitors targeting GH-GH receptor (GHR) signalling. Here we describe a panel of anti-GH monoclonal antibodies (mAbs) generated using a hybridoma approach and identify two novel inhibitory mAbs (1-8-2 and 1-46-3) that neutralised GH signalling. mAbs 1-8-2 and 1-46-3 exhibited strong inhibitory activity against GH-dependent cell growth in a Ba/F3-GHR cell viability assay, with EC50 values of 1.00 ± 0.27 and 0.5 ± 0.1 µg/mL, respectively. Cross-reactivity with the human placental hormones, placental lactogen (PL) and placental GH, was observed by ELISA, but neither antibody cross-reacted with mouse GH or human prolactin (PRL). mAb 1-8-2 had a binding affinity for GH of KD 0.62 ± 0.5 nM, while mAb 1-46-3 had a KD of 2.68 ± 0.53 nM, as determined by bio-layer interferometry. mAb 1-46-3 inhibited GH-dependent signal transduction in T-47D and LNCaP cancer cell lines and reduced GH-dependent cell growth and migration in the breast cancer cell line T-47D. mAb 1-46-3 inhibited T-47D cell viability more effectively than the GHR antagonist B2036. In conclusion, we describe two novel inhibitory anti-GH mAbs and provide in vitro evidence supporting development of these entities as anti-cancer therapeutics. [ABSTRACT FROM AUTHOR]

A correction to the article "The crystal structure of staphylococcal superantigen-like protein 11 in complex with sialyl Lewis X reveals the mechanism for cell binding and immune inhibition," that was published in 2007 issue, is presented.

Streptococcus pyogenes is an important human pathogen that causes a wide range of diseases. Using bioinformatics analysis of the complete S. pyogenes strain SF370 genome, we have identified a novel S. pyogenes virulence factor, which we termed streptococcal 5-nucleotidaseA(S5nA).Arecombinant form of S5nA hydrolyzed AMP and ADP, but not ATP, to generate the immunomodulatory molecule adenosine. Michaelis-Menten kinetics revealed a Km of 169μMand a Vmax of 7550 nmol/mg/min for the substrate AMP. Furthermore, recombinant S5nA acted synergistically with S. pyogenes nuclease A to generate macrophagetoxic deoxyadenosine from DNA. The enzyme showed optimal activity betweenpH5 andpH6.5 and between 37 and 47 °C. Like other 5'-nucleotidases, S5nA requires divalent cations and was active in the presence of Mg2+, Ca2+, or Mn2+. However, Zn2+ inhibited the enzymatic activity. Structural modeling combined with mutational analysis revealed a highly conserved catalytic dyad as well as conserved substrate and cation-binding sites. Recombinant S5nA significantly increased the survival of the non-pathogenic bacterium Lactococcus lactis during a human whole blood killing assay in a dose-dependent manner, suggesting a role as an S. pyogenes virulence factor. In conclusion, we have identified a novel S. pyogenes enzyme with 5-nucleotidase activity and immune evasion properties. [ABSTRACT FROM AUTHOR]