Biology subjects

Kizziah, J. L.

Publications and source records attributed to Kizziah, J. L..

7 recordsLinked to original sources

bioRxiv2026

Formation and role of the portal of Staphylococcus aureus bacteriophage 80α

Bacteriophages play an important role in the pathogenicity of Staphylococcus aureus, an important human pathogen. Phages are involved in generalized and specialized transduction as well as a more specific process by which they mobilize elements known as phage-inducible chromosomal islands, of which S. aureus pathogenicity islands (SaPIs) are an important group. SaPIs are mobilized at high frequency through interactions with specific "helper" bacteriophages, such as 80, leading to packaging of the SaPI genomes into virions made from structural proteins supplied by the helper. Among these structural proteins is the portal protein, which forms a ring-like portal at a fivefold vertex of the capsid, through which the DNA is packaged during virion assembly and ejected upon infection of the host. We previously showed that portal protein expressed in E. coli forms tridecameric rings, while portals found in virions are always dodecamers. To understand the role of the portal in capsid assembly, DNA packaging and ejection, we have here examined this phenomenon further. We show that portals assembled at lower temperature form unclosed rings that may represent portal assembly intermediates. By analyzing portal protein deletion mutants, we demonstrate the involvement of the different functional domains in phage assembly and protein incorporation.

microbiology↗

bioRxiv2024

Structure of the Staphylococcus aureus bacteriophage 80a neck shows the interactions between DNA, tail completion protein and tape measure protein

Tailed bacteriophages with double-stranded DNA genomes (class Caudoviricetes) play an important role in the evolution of bacterial pathogenicity, both as carriers of genes encoding virulence factors and as the main means of horizontal transfer of mobile genetic elements (MGEs) in many bacteria, such as Staphylococcus aureus. The S. aureus pathogenicity islands (SaPIs), including SaPI1, are a type of MGEs are that carry a variable complement of genes encoding virulence factors. SaPI1 is mobilized at high frequency by "helper" bacteriophages, such as 80, leading to packaging of the SaPI1 genome into virions made from structural proteins supplied by the helper. 80 and SaPI1 virions consist of an icosahedral head (capsid) connected via a unique vertex to a long, non-contractile tail. At one end of the tail, proteins associated with the baseplate recognize and bind to the host. At the other end, a connector or "neck" forms the interface between the tail and the head. The neck consists of several specialized proteins with specific roles in DNA packaging, phage assembly, and DNA ejection. Using cryo-electron microscopy and three-dimensional reconstruction, we have determined the high-resolution structure of the neck section of SaPI1 virions made in the presence of phage 80, including the dodecameric portal (80 gene product (gp) 42) and head-tail-connector (gp49) proteins, the hexameric head-tail joining (gp50) and tail terminator (gp52) proteins, and the major tail protein (gp53) itself. We were also able to resolve the DNA, the tail completion protein (gp51) and the tape measure protein (gp56) inside the tail. This is the first detailed structural description of these features in a bacteriophage, providing insights into the assembly and infection process in this important group of MGEs and their helper bacteriophages.

microbiology↗

bioRxiv2024

Potent neutralization by a receptor binding domain monoclonal antibody with broad specificity for SARS-CoV-2 JN.1 and other variants

SARS-CoV-2 continues to be a public health burden, driven in-part by its continued antigenic diversification and resulting emergence of new variants. While increasing herd immunity, current vaccines, and therapeutics have improved outcomes for some; prophylactic and treatment interventions that are not compromised by viral evolution of the Spike protein are still needed. Using a rationally designed SARS-CoV-2 Receptor Binding Domain (RBD) - ACE2 fusion protein and differential selection process with native Omicron RBD protein, we developed a recombinant human monoclonal antibody (hmAb) from a convalescent individual following SARS-CoV-2 Omicron infection. The resulting hmAb, 1301B7 potently neutralized a wide range of SARS-CoV-2 variants including the original Wuhan and more recent Omicron JN.1 strain, as well as SARS-CoV. Structure determination of the SARS-CoV-2 EG5.1 Spike/1301B7 Fab complex by cryo-electron microscopy at 3.1[A] resolution demonstrates 1301B7 contacts the ACE2 binding site of RBD exclusively through its VH1-69 heavy chain, making contacts using CDRs1-3, as well as framework region 3 (FR3). Broad specificity is achieved through 1301B7 binding to many conserved residues of Omicron variants including Y501 and H505. Consistent with its extensive binding epitope, 1301B7 is able to potently diminish viral burden in the upper and lower respiratory tract and protect mice from challenge with Omicron XBB1.5 and Omicron JN.1 viruses. These results suggest 1301B7 has broad potential to prevent or treat clinical SARS-CoV-2 infections and to guide development of RBD-based universal SARS-CoV-2 prophylactic vaccines and therapeutic approaches.

immunology↗

bioRxiv2023

Structure of the portal complex from Staphylococcus aureus Pathogenicity Island 1 transducing particles in situ and in solution

Staphylococcus aureus is an important human pathogen, and the prevalence of antibiotic resistance is a major public health concern. The evolution of pathogenicity and resistance in S. aureus often involves acquisition of mobile genetic elements (MGEs). Bacteriophages play an especially important role, since transduction represents the main mechanism for horizontal gene transfer. S. aureus pathogenicity islands (SaPIs), including SaPI1, are MGEs that carry genes encoding virulence factors, and are mobilized at high frequency through interactions with specific "helper" bacteriophages, such as 80, leading to packaging of the SaPI genomes into virions made from structural proteins supplied by the helper. Among these structural proteins is the portal protein, which forms a ring-like portal at a fivefold vertex of the capsid, through which the DNA is packaged during virion assembly and ejected upon infection of the host. We have used high- resolution cryo-electron microscopy to determine structures of the S. aureus bacteriophage 80 portal in solution and in situ in the empty and full SaPI1 virions, and show how the portal interacts with the capsid. These structures provide a basis for understanding portal and capsid assembly and the conformational changes that occur upon DNA packaging and ejection.

microbiology↗

bioRxiv2023

Alloreactivity and autoreactivity converge to support B cell epitope targeting in transplant rejection

Donor-specific antibody (DSA) responses against human leukocyte antigen (HLA) proteins mismatched between kidney transplant donors and recipients cause allograft loss. The rules governing the immunogenicity of non-self donor HLA are poorly understood. Using single-cell, molecular, structural, and proteomic techniques, we profiled the HLA-specific B cell response in the kidney and blood of a transplant recipient with antibody-mediated rejection (AMR). We observed an immunodominant B cell antibody response focused on topographically exposed, solvent-accessible mismatched HLA residues along the peptide-binding groove - a subregion comprising only 20% of the HLA molecule. We further demonstrated that, even within a diverse cohort of transplant recipients, the B cell alloresponse consistently converges on this same immunodominant subregion on the crown of the HLA molecule. Based on these findings, we propose that B cell immunodominance in transplant rejection relies on antigenic topography, and we suggest that this link could be exploited for organ matching and therapeutics.

immunology↗

bioRxiv2022

Structure and host specificity of Staphylococcus epidermidis bacteriophage Andhra

Staphylococcus epidermidis is an opportunistic pathogen of the human skin, often associated with infections of implanted medical devices. An increase in antibiotic resistance in S. epidermidis and other bacterial pathogens has led to renewed interest in the use of bacteriophages as an alternative to conventional antibiotics. Staphylococcal picoviruses are a group of strictly lytic, short-tailed bacteriophages with compact genomes that are attractive candidates for therapeutic use. Here, we report the structure of the complete virion of S. epidermidis-infecting phage Andhra, determined using high-resolution cryo-electron microscopy, allowing atomic modeling of the capsid and tail proteins, including twelve trimers of a unique receptor binding protein, the hexameric tail knob that acts as a gatekeeper for DNA ejection, and the tail tip, which is a heterooctamer of two different lytic proteins. Our findings elucidate critical features that enable host recognition and penetration, facilitating the development of this group of phages for therapeutic applications.

microbiology↗

bioRxiv2019

Structure of the host cell recognition and penetration machinery of a Staphylococcus aureus bacteriophage

Staphylococcus aureus is a common cause of infections in humans. The emergence of virulent, antibiotic-resistant strains of S. aureus is a significant public health concern. Most virulence and resistance factors in S. aureus are encoded by mobile genetic elements, and transduction by bacteriophages represents the main mechanism for horizontal gene transfer. The baseplate is a specialized structure at the tip of bacteriophage tails that plays key roles in host recognition, cell wall penetration, and DNA ejection. We have used high-resolution cryo-electron microscopy to determine the structure of the S. aureus bacteriophage 80 baseplate at 3.7 [A] resolution, allowing atomic models to be built for most of the major tail and baseplate proteins, including two tail fibers, a trimeric receptor binding protein, and part of the tape measure protein. Our structure provides a structural basis for understanding host recognition, cell wall penetration and DNA ejection in viruses infecting Gram-positive bacteria. Comparison to other phages demonstrate the modular design of baseplate proteins, and the adaptations to the host that take place during the evolution of staphylococci and other pathogens.

microbiology↗