Potently neutralizing and protective anti-human metapneumovirus antibodies target diverse sites on the fusion glycoprotein

Human metapneumovirus (hMPV) is a leading cause of acute lower respiratory tract infections in high-risk populations, yet there are no vaccines or anti-viral therapies approved for the prevention or treatment of hMPV-associated disease. Here, we used a high-throughput single-cell technology to interrogate memory B cell responses to the hMPV fusion (F) glycoprotein in young adult and elderly donors. Across all donors, the neutralizing antibody response was primarily directed to epitopes expressed on both pre- and post-fusion F conformations. However, we identified rare, highly potent broadly neutralizing antibodies that recognize pre-fusion-specific epitopes and structurally characterized an antibody that targets a site of vulnerability at the pre-fusion F trimer apex. Additionally, monotherapy with neutralizing antibodies targeting three distinct antigenic sites provided robust protection against lower respiratory tract infection in a small animal model. This study provides promising monoclonal antibody candidates for passive immunoprophylaxis and informs the rational design of hMPV vaccine immunogens.We acknowledge the Immune Monitoring and Flow Cytometry Resource (IMFCSR) at the Norris Cotton Cancer Center at Dartmouth supported by NCI Cancer Center Support Grant 5P30CA023108-41. This work was funded in part by Welch Foundation grant number F-0003-19620604.S

Broad and potent activity against SARS-like viruses by an engineered human monoclonal antibody

The recurrent zoonotic spillover of coronaviruses (CoVs) into the human population underscores the need for broadly active countermeasures. We employed a directed evolution approach to engineer three SARS-CoV-2 antibodies for enhanced neutralization breadth and potency. One of the affinity-matured variants, ADG-2, displays strong binding activity to a large panel of sarbecovirus receptor binding domains (RBDs) and neutralizes representative epidemic sarbecoviruses with high potency. Structural and biochemical studies demonstrate that ADG-2 employs a distinct angle of approach to recognize a highly conserved epitope overlapping the receptor binding site. In immunocompetent mouse models of SARS and COVID-19, prophylactic administration of ADG-2 provided complete protection against respiratory burden, viral replication in the lungs, and lung pathology. Altogether, ADG-2 represents a promising broad-spectrum therapeutic candidate against clade 1 sarbecoviruses

Antibiotic Releasing Biodegradable Sutures for the Prevention of Surgical Site Infections

Although a necessary component of surgery, sutures have been shown to exhibit an affinity for microbial adherence and colonization. The sutures offer a conduit for bacteria directly into the wound and infection can be difficult to treat post-colonization, even with antibiotics that are traditionally very effective. Infections associated with sutures are often difficult to resolve and require extended hospitalization, therapy, or additional surgical procedures. Drug eluting sutures offer a potential solution to this issue. In order to maximize antibiotic delivery, modeling changes in suture size, placement, and concentration could provide valuable information for surgeons and manufacturers to better develop and implant sutures, reducing the number of surgical site infections (SSIs) and thus morbidity and mortality. Using COMSOL software, we first generated both a 2D and a 3D model of MONOCRYL plus antibiotic sutures in the skin. Next, we modeled antibiotic-release and biodegradation by tracing the distance the drug penetrates into the surrounding tissue while the suture and the antibiotic are simultaneously being degraded by the body’s enzymatic processes. Finally, we adjusted the distance between adjacent sutures and suture size to ensure that the minimum inhibitory concentration (MIC) of triclosan for various bacteria strains was met at the wound site, without increasing the difficulty for surgeons to implant the suture. In our model, we showed the dispersion of antibiotics into the surrounding tissue over time, demonstrating up to what time point the sutures are able to maintain at least the minimum effective concentration level of antibiotic. We show that antibiotic levels sufficient enough to inhibit bacterial growth can be reached in complex environments, such as the skin. Based on our 3D model, the maximum spacing between adjacent 4-0 sutures to maintain a MIC for S. aureus for 72 hours after suture implantation is 2 mm. Suture spacing for other strains of bacteria can be determined through our predictive equations. The duration of antibacterial properties increases as the spacing between sutures is decreased, but increasing the initial concentration of triclosan in the suture does not significantly increase the duration of antibacterial properties of the suture. The suture decreases in volume by 45% seven days after implantation in the skin, indicating proper surface erosion and a significant loss in tensile strength after that time. The integrity of the suture is necessary to keep the wound closed over the entire healing period, preventing bacteria from entering through the open site and entering the tissue and subsequently traveling through the bloodstream. In this model, we reinforce in vivo and in vitro studies that suggest the effectiveness of antibiotic releasing sutures by modeling antibiotic concentrations in the skin following suture placement. This model will help surgeons determine the spacing for a variety of commercially available sutures, based on the bacterial inhibition properties required, in an effort to reduce the number of surgical site infections that occur. By ensuring effective distribution of antibiotic, following our developed standards in the surgical suite will reduce the number of surgical site infections, significantly reducing costs, morbidity, and mortality from post-operative infections

Repertoire-scale determination of class II MHC peptide binding via yeast display improves antigen prediction

Identifying peptides that can bind major histocompatibility complex II (MHC-II) is important for our understanding of T cell immunity and specificity. Here the authors present a yeast-display library screening approach that identifies more potential binders than various reported algorithms to help expand our understanding for antigen presentation

Vaccination reshapes the virus-specific T cell repertoire in unexposed adults

We examined how baseline CD4+ T cell repertoire and precursor states impact responses to pathogen infection in humans using primary immunization with yellow fever virus (YFV) vaccine. YFV-specific T cells in unexposed individuals were identified by peptide-MHC tetramer staining and tracked pre- and post-vaccination by tetramers and TCR sequencing. A substantial number of YFV-reactive T cells expressed memory phenotype markers and contained expanded clones in the absence of exposure to YFV. After vaccination, pre-existing YFV-specific T cell populations with low clonal diversity underwent limited expansion, but rare populations with a reservoir of unexpanded TCRs generated robust responses. These altered dynamics reorganized the immunodominance hierarchy and resulted in an overall increase in higher avidity T cells. Thus, instead of further increasing the representation of dominant clones, YFV vaccination recruits rare and more responsive T cells. Our findings illustrate the impact of vaccines in prioritizing T cell responses and reveal repertoire reorganization as a key component of effective vaccination

IL-33 Signaling Alters Regulatory T Cell Diversity in Support of Tumor Development

Regulatory T cells (Tregs) can impair anti-tumor immune responses and are associated with poor prognosis in multiple cancer types. Tregs in human tumors span diverse transcriptional states distinct from those of peripheral Tregs, but their contribution to tumor development remains unknown. Here, we use single-cell RNA sequencing (RNA-seq) to longitudinally profile dynamic shifts in the distribution of Tregs in a genetically engineered mouse model of lung adenocarcinoma. In this model, interferon-responsive Tregs are more prevalent early in tumor development, whereas a specialized effector phenotype characterized by enhanced expression of the interleukin-33 receptor ST2 is predominant in advanced disease. Treg-specific deletion of ST2 alters the evolution of effector Treg diversity, increases infiltration of CD8+ T cells into tumors, and decreases tumor burden. Our study shows that ST2 plays a critical role in Treg-mediated immunosuppression in cancer, highlighting potential paths for therapeutic intervention

Identification of Highly Cross-Reactive Mimotopes for a Public T Cell Response in Murine Melanoma

While immune checkpoint blockade results in durable responses for some patients, many others have not experienced such benefits. These treatments rely upon reinvigorating specific T cell-antigen interactions. However, it is often unknown what antigens are being recognized by T cells or how to potently induce antigen-specific responses in a broadly applicable manner. Here, we characterized the CD8+ T cell response to a murine model of melanoma following combination immunotherapy to determine the basis of tumor recognition. Sequencing of tumor-infiltrating T cells revealed a repertoire of highly homologous TCR sequences that were particularly expanded in treated mice and which recognized an antigen from an endogenous retrovirus. While vaccination against this peptide failed to raise a protective T cell response in vivo, engineered antigen mimotopes induced a significant expansion of CD8+ T cells cross-reactive to the original antigen. Vaccination with mimotopes resulted in killing of antigen-loaded cells in vivo yet showed modest survival benefit in a prophylactic vaccine paradigm. Together, this work demonstrates the identification of a dominant tumor-associated antigen and generation of mimotopes which can induce robust functional T cell responses that are cross-reactive to the endogenous antigen across multiple individuals.</jats:p

Structural and mechanistic basis of neutralization by a pan-hantavirus protective antibody

International audienceEmerging rodent-borne hantaviruses cause severe diseases in humans with no approved vaccines or therapeutics. We recently isolated a monoclonal broadly neutralizing antibody (nAb) from a Puumala virus-experienced human donor. Here, we report its structure bound to its target, the Gn/Gc glycoprotein heterodimer comprising the viral fusion complex. The structure explains the broad activity of the nAb: It recognizes conserved Gc fusion loop sequences and the main chain of variable Gn sequences, thereby straddling the Gn/Gc heterodimer and locking it in its prefusion conformation. We show that the nAb's accelerated dissociation from the divergent Andes virus Gn/Gc at endosomal acidic pH limits its potency against this highly lethal virus and correct this liability by engineering an optimized variant that sets a benchmark as a candidate pan-hantavirus therapeutic