Biology subjects

Zyla, D. S.

Publications and source records attributed to Zyla, D. S..

5 recordsLinked to original sources

bioRxiv2025

Stabilized Full-Length Measles Fusion Protein Elicits Potent Immunity and Protection In Vivo

Measles virus (MeV) is a highly contagious pathogen that causes significant morbidity and mortality in populations with low vaccination coverage. Infection typically leads to immune amnesia and, in rare cases, fatal neurological disease. While current live-attenuated vaccines are highly effective, they primarily elicit neutralizing antibodies against the hemagglutinin (H) glycoprotein, with a less robust response to the fusion (F) protein, a key protein for viral entry. To improve the immunogenicity of the F protein, we designed and characterized stabilized, prefusion MeV F protein antigens. We engineered both soluble ectodomains (FECTO) and full-length, membrane-embedded proteins (FFL) with mutations that confer thermal stability. Cryo-electron microscopy confirmed that these engineered antigens faithfully maintain the native prefusion conformation. When evaluated in a cotton rat model, immunization with either FECTO or FFL constructs induced neutralizing antibodies and elicited protection against viral challenge. The most stable full-length construct (FFL 3M) elicited a more potent neutralizing antibody response than its ectodomain counterpart. Importantly, no evidence of vaccine-enhanced respiratory disease was observed. These findings establish that a thermostable, full-length F protein is a superior immunogen to its soluble ectodomain. This work presents a promising candidate for next-generation, non-replicating measles vaccines intended to complement current vaccination strategies and provide a safe option for immunocompromised individuals and others who cannot receive live-virus vaccines. One-Sentence SummaryA prefusion-stabilized, full-length measles Fusion glycoprotein immunogen induces strong neutralizing responses and offers protection against challenge with wild-type virus.

immunology↗

bioRxiv2025

Structural and Mechanistic Basis for Antibody Neutralization of the Measles Fusion Protein

Measles virus (MeV) is a highly contagious viral pathogen and remains a major global health threat. Resurgent infections, driven by insufficient vaccine coverage, waning herd immunity, and the vulnerability of immunocompromised individuals, highlight the urgent need for effective countermeasures. Monoclonal antibodies (mAbs) represent a promising strategy, both as antiviral agents and as probes of viral entry mechanisms. While most vaccine-elicited neutralizing antibodies target the hemagglutinin (H) protein, emerging evidence suggests that antibodies against the fusion (F) protein are also potent inhibitors. Still, there is insufficient information on the target sites and activities of antibodies against the F protein. Like other class I fusion proteins, MeV F exists in a metastable prefusion state that undergoes dramatic conformational changes during viral entry. Here, we selected four mAbs that recognize conformational patterns of F-prefusion and/or postfusion, characterized their epitopes, specificities, and antiviral activities. Structural analyses mapped antibody interactions onto pre- and postfusion F conformations, revealing that all three neutralizing mAbs are specific for the prefusion form, while the non-neutralizing mAb recognizes only the postfusion F. Biophysical and functional assays defined distinct mechanisms: neutralization occurs either by stabilizing the prefusion protein or by preventing the extended intermediate from completing fusion. We also describe a novel mechanism of neutralization in which an antibody prematurely triggers F activation but blocks the subsequent refolding required for viral entry. Together, these findings provide the first detailed mapping of neutralizing epitopes on the MeV F protein and establish a framework for the rational design of F-targeted intervention.

immunology↗

bioRxiv2025

Uncovering the features of Measles-targeting human antibodies elicited by the MMR vaccine

Measles virus (MeV), a highly transmissible paramyxovirus, causes disease that can lead to severe complications and death, particularly in babies and young children. Deployment of the durable, highly effective, live-attenuated measles vaccine has saved an estimated 94 million lives in the past 50 years,1 yet the immunological explanation for this vaccines unique success and its landscape of antibody recognition remains unclear. Here we report the first panel of human monoclonal antibodies (mAbs) specific for the MeV hemagglutinin (H) and fusion (F) surface proteins, derived from the memory B cells of an MMR vaccinee. From over 100 cloned human mAbs, we mapped four major epitope clusters on H and another five major clusters on F, and structurally characterized 17 representative mAbs including one or more examples of each of the nine epitope clusters on the two surface antigens. We find that antibodies against both H and F can lead to potent virus neutralization and reduction of viral loads in vivo, including one mAb against F that reduces viral loads to below the limit of detection for all animals. High-resolution cryo-EM reveals contact sites of the most protective antibodies against both surface antigens. Discovery, characterization, and in vitro and in vivo success of these fully human mAbs now provide new avenues for prophylactic or therapeutic intervention against this re-emerging virus. HighlightsO_LIA large panel of Measles-specific monoclonal antibodies was isolated from a human MMR vaccinee, years after vaccination. C_LIO_LIStructural and biochemical mapping paints a landscape of antibody recognition with nine major competition groups, including four major sites on Hemagglutinin (H) and five on the fusion protein (F). C_LIO_LIAntibodies against both H and F confer in vitro neutralization and in vivo protection, including, in one case, undetectable viral load after antibody treatment. C_LIO_LIThe most protective H-specific mAbs, 4D08 and 1C08, target the receptor-binding site and the F-proximal outside of the H dimer, and likely function by interfering with receptor binding and H-F interactions, respectively. C_LIO_LIThe most protective F-specific mAbs, 3A12 and 4F09, target the sides and apex of the prefusion F trimer, and likely function by locking F into its pre-fusion state C_LI

immunology↗

bioRxiv2025

Human endogenous retrovirus K (HERV-K) envelope structures in pre- and post-fusion by Cryo-EM

The HERV-K envelope glycoprotein (Env) is aberrantly expressed in diseases including cancers and autoimmune disorders and is targeted by antibodies. The lack of structural information has hindered functional and immune recognition studies. We solved structures of the HERV-K Env in both pre- and post-fusion states with novel monoclonal antibodies using cryo-EM. The pre-fusion Env assembles as a trimer with a distinct fold and architecture compared to other retroviruses, while the post-fusion conformation features a unique "tether" helix within the TM subunit. A panel of monoclonal antibodies, elicited to facilitate structure determination, have been characterized for conformational and subunit specificity, serving as valuable research tools. These findings establish a structural framework for mechanistic studies of HERV-K Env in diseases and evaluation as a potential therapeutic target.

biochemistry↗

bioRxiv2022

Structural basis for antibody-mediated neutralization of Lymphocytic choriomeningitis virus

The mammarenavirus Lymphocytic choriomeningitis virus (LCMV) is a globally distributed zoonotic pathogen that can be lethal in immunocompromised patients and cause severe birth defects if acquired during pregnancy. Despite the fundamental importance of LCMV for studying immunobiology, the structure of the trimeric surface glycoprotein, essential for entry, vaccine design and antibody neutralization, remains unknown. In this study, we present the cryoEM structure of the LCMV surface glycoprotein (GP) in its trimeric prefusion assembly both alone and in complex with a rationally engineered monoclonal neutralizing antibody termed 18.5C-M28 (M28). Additionally, we show that passive administration of M28 protects mice from LCMV clone 13 (LCMVcl13) challenge when administered as either a prophylactic or therapeutic. Our study illuminates not only the overall structural organization of LCMV GP and the mechanism for its inhibition by M28, but also presents a promising therapeutic candidate to prevent severe or fatal disease in individuals who are at risk of infection by a virus that poses a threat worldwide. HighlightsO_LIRationally-engineered antibody M28 neutralizes lymphocytic choriomeningitis virus in vitro. C_LIO_LIFirst high-resolution cryoEM structure of the pre-fusion trimeric lymphocytic choriomeningitis virus glycoprotein alone and in complex with M28. C_LIO_LIM28 neutralizes by bridging adjacent glycoprotein protomers and locking it in the pre-fusion state. C_LIO_LIProphylactic and therapeutic administration of M28 protects mice from chronic lymphocytic choriomeningitis virus infection. C_LI

microbiology↗