Biology subjects

Mousa, J.

Publications and source records attributed to Mousa, J..

4 recordsLinked to original sources

bioRxiv2026

Molecular basis for protection and cross-protection by human antibodies targeting the parainfluenza virus hemagglutinin-neuraminidase protein

Human parainfluenza viruses (PIVs) are a leading cause of respiratory illness, particularly in vulnerable populations where infection can lead to severe disease. Despite their clinical impact, there are currently no licensed vaccines or effective antiviral treatments available. PIVs have two large surface proteins, the fusion and hemagglutinin-neuraminidase (HN) proteins, both of which are targets of neutralizing antibodies. In this study, we identified and characterized two human monoclonal antibodies (mAbs), 5217-2 and 5217-9, which bind recombinant PIV3 HN protein, bind PIV3-infected cells, and are neutralizing in vitro. We determined the binding epitopes of the PIV3 HN-specific mAbs via biolayer interferometry and found mAb 5217-9 targets a previously defined neutralizing epitope while mAb 5217-2 binds a unique epitope, enabling a more complete understanding of the antigenic landscape. To further understand the newly defined epitope, we determined a cryo-electron microscopy (cryo-EM) structure of mAb 5217-2, which revealed an epitope adjacent to the PIV3 HN protein active site. We also determined the structure of the previously discovered anti-PIV3 HN mAb PIV3HN-09, which was previously shown to be partially protective in vivo. In a hamster challenge model of PIV3, mAb 5217-2 was determined to significantly reduce lung viral titers, demonstrating its protective capacity. Furthermore, as the site 2-directed mAb PIV3HN-05 was previously shown to cross-neutralize PIV1, we evaluated its protective efficacy in an animal challenge model with PIV1, which demonstrated a reduction in lung viral titers. Overall, these findings provide new insights into the antigenic epitopes on the PIV3 HN protein to support structure-based vaccine design efforts and demonstrate new protective mAbs for both PIV3 and PIV1.

immunology↗

bioRxiv2025

Structural Basis for Childhood Antibody Recognition of The Human Metapneumovirus Fusion Protein

Human metapneumovirus (hMPV) is a significant cause of acute respiratory illness in children and adults, with the majority of children being seropositive for hMPV by five years of age. Infants, older adults, and immunocompromised individuals are more susceptible to severe hMPV infections that can lead to hospitalization and death. The hMPV fusion (F) protein is the sole target of neutralizing antibodies, and while the most common neutralizing epitopes on the hMPV F protein targeted by B cells in hMPV-infected adults have been previously determined, the antibody response in hMPV-infected children remains undefined. We isolated a panel of human monoclonal antibodies (mAbs) from children previously infected with hMPV (MPV498, MPV499, MPV510, MPV511, and MPV513), and the mAbs were assessed for binding avidity, neutralization potency, epitope specificity, and in vivo efficacy. All mAbs were neutralizing, and epitope binning revealed the presence of four different epitopes targeted by the mAbs. We determined the cryo-EM structures of four mAbs in complex with the hMPV F protein, which revealed epitopes located on the hMPV F trimer surface as well as an intratrimer epitope located completely within the hMPV F trimer interface. Furthermore, we determined the prophylactic efficacy of the mAbs in protection against hMPV challenge in mice. Overall, our data reveal new insights into the immunodominant antigenic epitopes on the hMPV F protein in children and identify new mAb therapies for hMPV F disease prevention.

immunology↗

bioRxiv2022

Synergistic protection against secondary pneumococcal infection by human monoclonal antibodies targeting distinct epitopes

Streptococcus pneumoniae persists as a leading cause of bacterial pneumonia despite the widespread use of polysaccharide-based vaccines. The limited serotype coverage of current vaccines has led to increased incidence of non-vaccine serotypes, as well as an increase in antibiotic resistance among these serotypes. Pneumococcal infection often follows a primary viral infection such as influenza virus, which hinders host defense and results in bacterial spread to the lungs. We previously isolated human monoclonal antibodies (mAbs) against the conserved surface antigen pneumococcal histidine triad protein D (PhtD), and we demonstrated that mAbs to this antigen are protective against lethal pneumococcal challenge prophylactically and therapeutically. In this study, we elucidated the mechanism of protection of a protective anti- pneumococcal human mAb, PhtD3, which is mediated by the presence of complement and macrophages in a mouse model of pneumococcal infection. Treatment with mAb PhtD3 reduced blood and lung bacterial burden in mice, and mAb PhtD3 is able to bind to bacteria in the presence of the capsular polysaccharide, indicating exposure of surface PhtD on encapsulated bacteria. In a mouse model of secondary pneumococcal infection, protection mediated by mAb PhtD3 and another mAb targeting a different epitope, PhtD7, was reduced, however, robust protection was restored by combining mAb PhtD3 with mAb PhtD7, indicating a synergistic effect. Overall, these studies provide new insights into anti-pneumococcal mAb protection and demonstrate for the first time that mAbs to pneumococcal surface proteins can protect against secondary pneumococcal infection in the mouse model. Author SummaryThe persistence of Streptococcus pneumoniae as a leading cause of bacterial pneumonia despite numerous approved pneumococcal vaccines is a serious threat to public health globally. Currently, prophylactic and therapeutic options for Streptococcus pneumoniae are constrained by the limited serotype coverage of vaccines and the emergence of antibiotic resistant strains. An additional hurdle to overcome is the incidence of secondary pneumococcal infection following a viral infection, which leads to increased mortality. Here, we determined the mechanism of action of a monoclonal antibody (mAb) that targets Streptococcus pneumoniae. We found that mAb PhtD3 operates through macrophage and complement mediated functions. mAb PhtD3 was also discovered to reduce bacterial titers in the lungs and blood and bind to a related antigen PhtE. We also tested additional mAbs and discovered that two unique mAbs to the antigen PhtD conferred protection in a pneumococcal-influenza virus co-infection model. Our study provides new insights into the mechanisms and therapeutic potential of mAbs targeting conserved proteins of Streptococcus pneumoniae.

immunology↗

bioRxiv2021

The pre-existing human antibody repertoire to computationally optimized influenza H1 hemagglutinin vaccines

The computationally optimized broadly reactive antigen (COBRA) approach has previously been used to generate hemagglutinin (HA) immunogens for several influenza subtypes that expand vaccine-elicited antibody breadth. As nearly all individuals have pre-existing immunity to influenza viruses, influenza-specific memory B cells will likely be recalled upon COBRA HA vaccination. We determined the epitope specificity and repertoire characteristics of pre-existing human B cells to H1 COBRA HA antigens. Cross-reactivity between wild type HA and H1 COBRA HA proteins were observed at both the oligoclonal B cell level and for a subset of isolated monoclonal antibodies (mAbs). The mAbs bound five distinct epitopes on the pandemic A/California/04/2009 head and stem domains, and the majority of the mAbs had HAI and neutralizing activity against pandemic H1 strains. Two head-directed mAbs, CA09-26 and CA09-45, had HAI and neutralizing activity against a pre-pandemic H1 strain. One mAb, P1-05, targets the stem region of H1 HA proteins, but does not compete with known stem-targeting H1 mAbs. We determined that mAb P1-05 recognizes a recently discovered membrane proximal epitope on HA, the anchor epitope, and we identified similar mAbs using B cell repertoire sequencing. In addition, the trimerization domain distance from HA was critical to recognition of this epitope by P1-05. Overall, these data indicate that seasonally vaccinated individuals possess a population of functional H1 COBRA HA- reactive B cells that target head, central stalk, and anchor epitopes, and demonstrate the importance of structure-based assessment of subunit protein vaccine candidates to ensure accessibility of optimal protein epitopes. SignificanceInfluenza imposes significant human and economic costs every year. The current seasonal vaccine elicits primarily strain-specific antibodies, and year to year vaccine effectiveness is variable. The COBRA approach could provide longer protection and obviate the requirement for annual vaccination. Whereas COBRA HAs have previously been evaluated in animal models, the pre-existing COBRA HA-reactive human B cell population has yet to be elucidated, and is important to identify specific B cells that may be recalled by H1 HA COBRA vaccination. This work demonstrates that seasonally vaccinated individuals possess a functional B cell population targeting both head and stem domains that could be recalled with COBRA HA immunogens.

immunology↗