Joseph R. Francica

Human metapneumovirus (hMPV) is associated with severe disease in young children, older adults, and medically high-risk individuals. The hMPV F protein is highly immunogenic and a well-established target of neutralizing antibodies. In-depth hMPV surveillance data remain limited and may provide valuable insight into therapeutic development. Here we assembled a contemporary dataset of F gene sequences acquired from hMPV-positive nasal swab specimens collected between 2022 and 2023, together with contemporary F gene sequences from public surveillance databases, collected between 2017 and 2025. All sequences were subtyped and evaluated for residue-level similarity to reference alleles. Of 724 sequences in the combined contemporary dataset, A2 was the most predominant subtype accounting for nearly half of all sequences (50.83%). The mean F gene sequence similarity to reference alleles was 99.90%, 99.95%, and 99.84% for A2, B1, and B2, respectively; the least conserved residues were the stalk residue 518 for A2 (88.52% similarity to reference allele); BinD residue 450 for B1 (96.60% similarity); and site III residue 36 for B2 (77.88% similarity). Structural analysis showed that observed mutations were predominantly surface-exposed, with no evidence of novel N-linked glycosylation sequons, and were not predicted to significantly alter F protein structure. Overall, these findings indicate that the F protein is highly conserved across subtypes, with sequence variation unlikely to result in meaningful structural differences, thereby supporting development of F-targeted therapeutics against hMPV infection.

Local intramuscular administration of synthetic plasmid DNA (pDNA) encoding monoclonal antibodies (mAb) offers an alternative to recombinant protein-based mAb delivery. In this phase 1 dose-escalation study, we evaluated the safety, tolerability and pharmacokinetics of a pDNA cocktail encoding AZD5396 and AZD8076, modified versions of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing mAb cocktail tixagevimab/cilgavimab in healthy adults. Participants received up to four intramuscular doses of pDNA encoding both DNA-based mAbs (DMAbs), administered using CELLECTRA electroporation. The primary endpoints were safety and pharmacokinetics. All 44 participants received at least one dose; DMAbs were detected in 100% of evaluable participants (n = 39), with serum concentrations reaching a peak of 1.61 µg ml⁻¹. Sustained expression was observed in all participants during the 72 weeks of follow-up. The study product was well tolerated, with no product-related serious adverse events reported. Exploratory analyses demonstrated binding to multiple SARS-CoV-2 Spike protein variants and neutralizing activity in a standard pseudovirus assay. No antidrug antibodies were detected across approximately 1,000 serum samples using validated tiered assays. To our knowledge, these data represent the first-in-human proof-of-concept that synthetic pDNA DMAb technology permits the durable in vivo production of a functional mAb cocktail. This study further underscores the collective importance of synthetic design, formulation and delivery to achieve biologically relevant expression of gene-encoded biologics. DMAb delivery may represent a long-acting, scalable, cold-chain-independent platform against a wide range of diseases that can be targeted with mAbs and their derivatives. ClinicalTrials.gov registration: NCT05293249

Background/Objectives: SARS-CoV-2 vaccine candidates comprising the receptor binding domain (RBD) of the spike protein have been shown to confer protection against infection. Previous research evaluating vaccine candidates with SARS-CoV-2 RBD fused to ferritin (RBD-ferritin) and other scaffolds suggested that multimeric assemblies of RBD can enhance antigen presentation to improve the potency and breadth of immune responses. Though RBDs directly fused to a self-assembling scaffold can be delivered as messenger RNA (mRNA) formulated with lipid nanoparticles (LNPs), reports of SARS-CoV-2 vaccine candidates that combine these approaches remain scarce. Methods: Here, we designed RBD fused to AP205 or TIP60 self-assembling nanoparticles following a search of available structures focused on several scaffold properties. RBD-AP205 and RBD-TIP60 were tested for antigenicity following transfection and for immunogenicity and neutralization potency when delivered as mRNA in mice, with RBD-ferritin as a direct comparator. Results: All scaffolded RBD constructs were readily secreted to transfection supernatant and showed antigenicity in ELISA, though clear heterogeneity in assembly was observed. RBD-AP205 and RBD-TIP60 also exhibited robust antibody binding and neutralization titers in mice that were comparable to those elicited by RBD-ferritin or a full-length membrane-bound spike. Conclusions: These data suggest that AP205 and TIP60 can present RBD as effectively as ferritin and induce similar immune responses. By describing additional scaffolds for multimeric display that accommodate mRNA delivery platforms, this work can provide new tools for future vaccine design efforts.

Antibodies mediate protection against a wide range of pathogens through binding and neutralizing the pathogen or through Fc-mediated effector functions. Human monoclonal antibodies (mAbs) CIS43LS and L9LS show high-affinity binding targeting distinct regions on the Plasmodium falciparum circumsporozoite protein (PfCSP) and are highly effective in preventing malaria in humans. However, the role of FcγR binding in protection by these mAbs has not been determined. Here, we assessed several Fc variants of CIS43LS and L9LS for protection against infection with transgenic Plasmodium berghei parasite expressing PfCSP in mice. Limiting binding to FcγRs did not reduce protection compared to the parental mAbs in mice. To determine whether protection could be improved in vivo by Fc modification, we engineered Fc variant mAbs with increased binding to distinct FcγRs. Passive transfer of CIS43LS-DE and CIS43LS-DEAL variants resulted in an approximately two- to threefold reduction in the liver-stage parasite burden in C57BL/6 or human FcγR mice compared with the parental CIS43LS after challenge. CIS43LS-DEAL also enhanced protection of mice after mosquito bite challenge. Systems serology analysis revealed that the CIS43LS-DE and CIS43LS-DEAL variants could enhance human neutrophil and monocyte phagocytosis, as well as NK cell activation, compared with CIS43LS. However, similar Fc modifications incorporated into L9LS did not increase protection compared to the parental mAb. Overall, although FcγR binding by CIS43LS and L9LS is dispensable in mouse models of malaria, enhancing the binding of CIS43LS to FcγR showed a modest increase in the potency of this mAb.

Most previously authorized clinical antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have lost neutralizing activity to recent variants due to rapid viral evolution. To mitigate such escape, we preemptively enhance AZD3152, an antibody authorized for prophylaxis in immunocompromised individuals. Using deep mutational scanning (DMS) on the SARS-CoV-2 antigen, we identify AZD3152 vulnerabilities at antigen positions F456 and D420. Through two iterations of computational antibody design that integrates structure-based modeling, machine-learning, and experimental validation, we co-optimize AZD3152 against 24 contemporary and previous SARS-CoV-2 variants, as well as 20 potential future escape variants. Our top candidate, 3152-1142, restores full potency (100-fold improvement) against the more recently emerged XBB.1.5+F456L variant that escaped AZD3152, maintains potency against previous variants of concern, and shows no additional vulnerability as assessed by DMS. This preemptive mitigation demonstrates a generalizable approach for optimizing existing antibodies against potential future viral escape.

The evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in variants that can escape neutralization by therapeutic antibodies. Here, we describe AZD3152, a SARS-CoV-2–neutralizing monoclonal antibody designed to provide improved potency and coverage against emerging variants. AZD3152 binds to the back left shoulder of the SARS-CoV-2 spike protein receptor binding domain and prevents interaction with the human angiotensin-converting enzyme 2 receptor. AZD3152 potently neutralized a broad panel of pseudovirus variants, including the currently dominant Omicron variant JN.1 but has reduced potency against XBB subvariants containing F456L. In vitro studies confirmed F456L resistance and additionally identified T415I and K458E as escape mutations. In a Syrian hamster challenge model, prophylactic administration of AZD3152 protected hamsters from weight loss and inflammation-related lung pathologies and reduced lung viral load. In the phase 1 sentinel safety cohort of the ongoing SUPERNOVA study ( ClinicalTrials.gov : NCT05648110), a single 600-mg intramuscular injection of AZD5156 (containing 300 mg each of AZD3152 and cilgavimab) was well tolerated in adults through day 91. Observed serum concentrations of AZD3152 through day 91 were similar to those observed with cilgavimab and consistent with predictions for AZD7442, a SARS-CoV-2–neutralizing antibody combination of cilgavimab and tixagevimab, in a population pharmacokinetic model. On the basis of its pharmacokinetic characteristics, AZD3152 is predicted to provide durable protection against symptomatic coronavirus disease 2019 caused by susceptible SARS-CoV-2 variants, such as JN.1, in humans.

Durable humoral immunity is mediated by long-lived plasma cells (LLPCs) that reside in the bone marrow. It remains unclear whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein vaccination is able to elicit and maintain LLPCs. Here, we describe a sensitive method to identify and isolate antigen-specific LLPCs by tethering antibodies secreted by these cells onto the cell surface. Using this method, we found that two doses of adjuvanted SARS-CoV-2 spike protein vaccination are able to induce spike protein–specific LLPC reservoirs enriched for receptor binding domain specificities in the bone marrow of nonhuman primates that are detectable for several months after vaccination. Immunoglobulin gene sequencing confirmed that several of these LLPCs were clones of memory B cells elicited 2 weeks after boost that had undergone further somatic hypermutation. Many of the antibodies secreted by these LLPCs also exhibited improved neutralization and cross-reactivity compared with earlier time points. These findings establish our method as a means to sensitively and reliably detect rare antigen-specific LLPCs and demonstrate that adjuvanted SARS-CoV-2 spike protein vaccination establishes spike protein–specific LLPC reservoirs.

Viral pandemics and epidemics pose a significant global threat, with emerging and re-emerging viruses responsible for four pandemics in the 21st century alone. While macaques have been utilized as a model for understanding viral disease in a controlled setting, it remains unclear how conserved the antiviral responses to diverse viruses are between macaques and humans. To address this critical knowledge gap, we conducted a comprehensive cross-species analysis of transcriptomic data from over 6000 blood samples from macaques and humans infected with one of 31 viruses, including Lassa, Ebola, Marburg, Zika, and dengue. Our findings demonstrate that irrespective of primate or viral species, there are conserved antiviral responses which are consistent regardless of infection phase (acute, chronic, or latent) and viral genome type (DNA or RNA viruses). Moreover, by leveraging longitudinal data from experimental challenges, we identified virus-specific response dynamics such as host responses to Coronaviridae and Orthomyxoviridae infections peaking 1-3 days earlier than responses to Filoviridae and Arenaviridae viral infections. Additionally, through comparative analysis of immune responses across viruses, we identified a unique enrichment of lymphoid cellular response modules in macaque Flaviviridae infection that persists in human responses to dengue. Our results underscore macaque studies as a powerful tool for gaining new insights into viral pathogenesis and immune responses that translate to humans, which can inform viral therapeutic development and enable pandemic preparedness. One sentence summary: Using longitudinal macaque viral challenge studies, we identified shared and virus-specific responses to infection that replicate in human viral disease - thereby demonstrating the utility of macaque models of viral infection to understand antiviral biology and for pandemic preparedness.

The monoclonal antibody CIS43 targets the Plasmodium falciparum circumsporozoite protein (PfCSP) and prevents malaria infection in humans for up to 9 mo following a single intravenous administration. To enhance the potency and clinical utility of CIS43, we used iterative site-saturation mutagenesis and DNA shuffling to screen precise gene-variant yeast display libraries for improved PfCSP antigen recognition. We identified several mutations that improved recognition, predominately in framework regions, and combined these to produce a panel of antibody variants. The most improved antibody, CIS43_Var10, had three mutations and showed approximately sixfold enhanced protective potency in vivo compared to CIS43. Co-crystal and cryo-electron microscopy structures of CIS43_Var10 with the peptide epitope or with PfCSP, respectively, revealed functional roles for each of these mutations. The unbiased site-directed mutagenesis and screening pipeline described here represent a powerful approach to enhance protective potency and to enable broader clinical use of antimalarial antibodies.