Biology subjects

Walker, F. C.

Publications and source records attributed to Walker, F. C..

4 recordsLinked to original sources

bioRxiv2025

A Microphysiologic Model of the Cervical Epithelium Recapitulates Microbial, Immunologic, and Pathogenic Properties of Sexually Transmitted Infections

Sexually transmitted infections (STIs) of the cervicovaginal mucosa are among the most common global infections. Clinical studies have revealed that susceptibility to STIs and the subsequent host responses they elicit are frequently associated with vaginal microbiota compositions that facilitate infection. Current monolayer cell culture and animal models fail to reproduce the multilevel complexity required to investigate these relationships simultaneously and/or with sufficient physiological relevance. To address this limitation, we have developed a microphysiologic system (MPS) that models human cervical tissue, its microbiota, and is susceptible to infection by two prominent genital pathogens, Chlamydia trachomatis and Neisseria gonorrhoeae. Significantly, this MPS platform recapitulates essential dynamic, polymicrobial, immune, and pathogenic features of chlamydial and gonococcal infections as they occur in humans. The lowcost MPS device requires no specialized equipment or specific expertise and was experimentally validated for both chlamydial and gonococcal infections across multiple nonengineering, remotely located laboratories, demonstrating its transferability and reproducibility. The MPS platform described herein provides a novel tool for expanded research into genital infections in a reconstituted system that closely mimics the cervical epithelium, a significant advance over existing models.

bioengineering↗

bioRxiv2025

Acinetobacter phages use distinct strategies to breach the capsule barrier

Acinetobacter baumannii is an opportunistic pathogen that is a growing threat in hospital settings due to its alarmingly high rates of antibiotic resistance. Alternative therapies are urgently needed to manage the growing burden of untreatable A. baumannii infections. Phage therapy is a promising avenue that has already seen some success in isolated compassionate-use cases, including the famous "Patterson case". A. baumannii capsule is highly diverse both in structure and composition, and provides the first immunity barrier against phages. Here, we perform a detailed molecular characterization of three recently isolated, distinct A. baumannii phages that breach the capsule via different mechanisms. Like many previously described A. baumannii phages, a specific capsule type is necessary and sufficient for StAb1 infection. We found that StAb2 and its relatives adsorb to either a specific capsule type or the conserved outer membrane protein CarO, a porin normally occluded by the capsule. Thus, this phage has a narrow host range amongst capsulated strains, but can broadly infect A. baumannii strains lacking capsule. We also show that an unclassified siphophage, StAb3, requires a conserved and uncharacterized glycan, likely containing ManNAc, that enables StAb3 to infect a broad range of A. baumannii strains without depolymerizing the capsule. We demonstrate how rationally combining phages with distinct capsule interactions reduces the rapid emergence of phage escape mutants, with potential applications for more effective phage therapy.

microbiology↗

bioRxiv2024

Interferons and tuft cell numbers are bottlenecks for persistent murine norovirus infection

Noroviruses (NoVs) are a leading cause of viral gastroenteritis. Despite global clinical relevance, our understanding of how host factors, such as antiviral cytokines interferons (IFNs), modulate NoV population dynamics is limited. Murine NoV (MNoV) is a tractable in vivo model for the study of host regulation of NoV. A persistent strain of MNoV, CR6, establishes a reservoir in intestinal tuft cells for chronic viral shedding in stool. However, the influence of host innate immunity and permissive cell numbers on viral population dynamics is an open question. We generated a pool of 20 different barcoded viruses (CR6BC) by inserting 6-nucleotide barcodes at the 3 position of the NS4 gene and used this pool as our viral inoculum for in vivo infections of different mouse lines. We found that over the course of persistent CR6 infection, shed virus was predominantly colon-derived, and viral barcode richness decreased over time irrespective of host immune status, suggesting that persistent infection involves a series of reinfection events. In mice lacking the IFN-{lambda} receptor, intestinal barcode richness was enhanced, correlating with increased viral intestinal replication. IL-4 treatment, which increases tuft cell numbers, also increased barcode richness, indicating the abundance of permissive tuft cells to be a bottleneck during CR6 infection. In mice lacking type I IFN signaling (Ifnar1-/-) or all IFN signaling (Stat1-/-), barcode diversity at extraintestinal sites was dramatically increased, implicating different IFNs as critical bottlenecks at specific tissue sites. Of interest, extraintestinal barcodes were overlapping but distinct from intestinal barcodes, indicating that disseminated virus represents a distinct viral population than that replicating in the intestine. Barcoded viruses are a valuable tool to explore the influence of host factors on viral diversity in the context of establishment and maintenance of infection as well as dissemination and have provided important insights into how NoV infection proceeds in immunocompetent and immunocompromised hosts.

microbiology↗

bioRxiv2019

CD300lf is the primary physiologic receptor of murine norovirus but not human norovirus

Murine norovirus (MNoV) is an important model of human norovirus (HNoV) and mucosal virus infection more broadly. Viral receptor utilization is a major determinant of cell tropism, host range, and pathogenesis. The bona fide receptor for HNoV is unknown. Recently, we identified CD300lf as a proteinaceous receptor for MNoV. Interestingly, its paralogue CD300ld was also sufficient for MNoV infection in vitro. Here we explored whether CD300lf is the sole physiologic receptor in vivo and whether HNoV can use a CD300 ortholog as an entry receptor. We report that both CD300ld and CD300lf are sufficient for infection by diverse MNoV strains in vitro. We further demonstrate that CD300lf is essential for both oral and parenteral MNoV infection and to elicit anti-MNoV humoral responses in vivo. In mice deficient in STAT1 signaling, CD300lf is required for MNoV-induced lethality. However, after high dose intraperitoneal challenge with MNoV in Cd300lf-/-Stat1-/- mice a single amino acid mutation in the MNoV capsid protein emerged. This substitution did not alter receptor utilization in vitro. Finally, we demonstrate that human CD300lf (huCD300lf) is not essential for HNoV infection, nor does huCD300lf inhibit binding of HNoV virus-like particles to glycans. Thus, we report huCD300lf is not a receptor for HNoV. Author SummaryHuman norovirus is the leading cause of non-bacterial gastroenteritis causing up to 200,000 deaths each year. How human norovirus enters cells is unknown. Because human norovirus is difficult to grow in the laboratory and in small animals, we use mouse or murine norovirus as a model system. We recently discovered that murine norovirus can use the either CD300ld or CD300lf as a receptor in vitro. We also showed that CD300lf deficient mice were resistant to oral challenge with a single virus strain. Here we determined that CD300lf is essential for infection of diverse murine norovirus strains in cell lines and in mice with normal immune systems demonstrating its the primary physiologic receptor for diverse murine norovirus strains independent of infection route. However, in immunodeficient mice injected with high dose virus directly into the abdominal cavity, we observed a norovirus mutant that enabled CD300lf-independent infection. Finally, we demonstrated that human CD300lf is not the elusive receptor for human norovirus.

microbiology↗