Novalia Pishesha

Through screening of a VHH phage display library constructed from an alpaca immunized with the recombinantly expressed murine myelin oligodendrocyte (MOG)-specific 2D2 T cell receptor (TCR), we identified nanobodies that reduced antigen-driven 2D2 T cell activation in vitro. Immunoblotting and staining confirmed TCRβ chain reactivity and Vβ11-associated recognition in polyclonal T cell populations. Site-specific sortase-mediated conjugation with desferrioxamine and 89Zr enabled nanobody-based immuno-PET/CT. In vivo imaging showed tracer accumulation in secondary lymphoid organs in settings enriched for Vβ11-expressing 2D2 T cells. In mice symptomatic for experimental autoimmune encephalomyelitis that had received MOG-specific 2D2 T cells, we observed a spinal cord-associated signal. This corresponded to accumulation of transferred Vβ11-expressing 2D2 T cells within inflamed spinal cord tissue. Compared with full-length immunoglobulins and multimeric peptide-MHC reagents that primarily support ex vivo detection of antigen-specific T cells, TCR-specific nanobodies show rapid clearance and improved tissue penetration that favor high-contrast immuno-PET/CT imaging of defined T cell populations in vivo.

Monoclonal antibodies have revolutionized cancer therapy, with approved therapeutics belonging predominantly to the immunoglobulin G (IgG) class. These IgGs mediate antitumor effects predominantly through engagement of Fcγ receptors on immune cells. This engagement results in therapy-activating Fc effector functions such as antibody-dependent cellular cytotoxicity, antibody-dependent cellular phagocytosis, and complement-dependent cytotoxicity. Limitations nonetheless include suboptimal effector engagement and adverse immunological side effects. These drawbacks have driven the search for and optimization of Fc-engineering strategies, including Fc mutations, glycan modification, and choice of Ig isotype, to enhance therapeutic efficacy and tailor immune interactions.

We describe the production and use of nanobody drug conjugates that comprise of VHH _kappa , a nanobody that recognizes mouse immunoglobulin kappa light chains, and one or more copies of the small molecule influenza virus neuraminidase (NA) inhibitor, zanamivir. Such compounds achieve half-life extension of zanamivir, while recruiting polyclonal immunoglobulins of all isotypes regardless of specificity to infected cells for antibody-dependent cell-mediated cytotoxicity and complement-dependent cellular cytotoxicity. Since the influenza A virus (IAV) NA is a tetramer, we produced VHH _kappa adducts with 1, 2, or 4 zanamivir molecules attached in a site-specific manner, to allow multivalent engagement of NA. Administration of a VHH _kappa adduct modified with 4 zanamivir molecules (VHH _kappa –Zan ₄ ) was ~10-fold more potent in protection against infection with IAV than VHH _kappa –Zan carrying only a single zanamivir molecule. VHH _kappa –Zan ₄ can be given intranasally to confer full protection against a lethal IAV challenge. The neutralizing antibody titers in the respiratory mucosa and in the circulation, as well as the serum IgG antibody response against the hemagglutinin and nucleoprotein, are higher in VHH _kappa –Zan ₄ treated mice that survived the lethal challenge than in controls infected with a sublethal dose of virus. VHH _kappa –Zan ₄ affords protection even when given intranasally weeks prior to a challenge with a lethal dose of IAV. This type of adduct can therefore be applied prophylactically and therapeutically and does not require prior immunization for protection against a lethal dose of IAV.

This year at JEM, we are highlighting women in science by sharing their stories and amplifying their voices. In this Viewpoint, we hear from a cross section of women, across multiple research fields, discussing their science and the process of setting up a lab as an independent researcher.

The alpha-variant wave of the COVID-19 pandemic provided a unique opportunity to study, at single-cell resolution, how near-universal exposure to the same pathogen can lead to either effective or dysfunctional immune responses in humans. Although single-cell RNA-sequencing studies have characterized immune cellular features of COVID-19, they have not shown how tocilizumab treatment changes these features at single-cell resolution, or which features might persist into convalescence. In this study, we analyzed 2.5 million circulating immune cells from 428 patients across time points (840 PBMC samples), encompassing three contemporaneous SARS-CoV-2 cohorts: acutely infected patients across five WHO disease severity levels and three time points, patients from the first randomized control trial to study the efficacy of tocilizumab in the management of COVID-19, and convalescent patients three months after infection. We used linear modeling to integrate multiple data types – including single-cell RNA-seq, CITE-seq, TCR and BCR sequencing, viral load measurements, viral neutralization assays, detection of 75 autoantibodies, HLA genotype data, and serum proteomics covering 1,463 targets – to derive the most comprehensive view to-date of the biological features of COVID-19 disease severity. Our findings show that myeloid-derived suppressor cells (MDSCs) act as a key immunologic pivot point in severe COVID-19. Myeloid dysfunction, which is marked by impaired antigen presentation, drives a non-productive adaptive immune response, as reflected by reduced expression of B and T cell gene programs involved in antigen recognition, immune synapse formation, and cytotoxicity. Severe disease is also linked to autoantibodies targeting type I interferons, influenced by specific HLA-DQB1 allelic variants, and strongly correlated with serum IL-6 levels. Tocilizumab treatment eliminates CLU -expressing MDSCs and ISG-positive myeloid subsets, restores antigen presentation, and reactivates productive adaptive immunity. These changes align with improved clinical outcomes and better clinical laboratory measures, including reduced CRP. While many immunologic abnormalities in acute severe COVID-19 resolve during convalescence 3-months post-infection, we observed persistently high ICOS expression in regulatory T cells, potentially linking acute infection to chronic post-COVID syndromes. Overall, we define distinct innate and adaptive host immune responses associated with acute, IL-6–responsive, and convalescent SARS-CoV-2 infection. Our multimodal and high-dimensional dataset with curated clinical metadata provides a foundational and clinically relevant resource for modeling host immune response biology in health and disease.

Conditional therapeutics that rely on disease microenvironment-specific triggers for activation are a promising strategy to improve therapeutic cargos. Among the investigated triggers, protease activity is used most often, because of its dysregulation in several diseases. How to optimally fine-tune protease activation for different therapeutic cargos remains a challenge. Here, we designed nanobody-targeted conditional antimicrobial therapeutics to deliver a model therapeutic peptide and protein to the site of bacterial infection. We explored several parameters that influence proteolytic activation. We report the use of targeting nanobodies to enhance the activation of therapeutics that are otherwise activated inefficiently, despite extensive optimization of the cleavable linker. Specifically, pairing of Ly6G/C or ADAM10-targeting nanobodies with ADAM10-cleavable linkers improved activation via proximity-enabled reactivity. More broadly, this optimization framework provides a guideline for the development of conditional therapeutics to treat various diseases where protease activity is dysregulated.

The distribution of Ly6C/G-positive cells in response to an infection of the mouse respiratory tract with influenza A virus was followed noninvasively over time by immuno-positron emission tomography. We converted nanobodies that recognize Ly6C and Ly6G, markers of neutrophils and other myeloid cells, as well as an influenza hemagglutinin–specific nanobody, into ⁸⁹ Zr-labeled PEGylated positron emission tomography (PET) imaging agents. The PET images showed strong accumulation of these imaging agents in the lungs of infected mice. Immunohistochemistry of influenza virus–infected mice and control mice, injected with a biotinylated and PEGylated version of the Ly6C/G-specific nanobody, showed the presence of abundant Ly6C/G-positive myeloid cells and positivity for Ly6C/G on bronchial epithelium in influenza virus–infected mice. This is consistent with focal inflammation in the lungs, a finding that correlated well with the immuno-PET results. No such signals were detected in control mice. Having shown by PET the accumulation of the Ly6C/G-specific nanobody in infected lungs, we synthesized conjugates of Ly6C/G-specific nanobodies with dexamethasone to enable targeted delivery of this immunosuppressive corticosteroid to sites of inflammation. Such conjugates reduced the weight loss that accompanies infection, while the equivalent amount of free dexamethasone was without effect. Nanobody-drug conjugates thus enable delivery of drugs to particular cell types at the appropriate anatomic site(s). By avoiding systemic exposure to free dexamethasone, this strategy minimizes its undesirable side effects because of the much lower effective dose of the nanobody-dexamethasone conjugate. The ability to selectively target inflammatory cells may find application in the treatment of other infections or other immune-mediated diseases.

SARS-CoV-2 Omicron variants have generated a world-wide health crisis due to resistance to most approved SARS-CoV-2 neutralizing antibodies and evasion of antibodies induced by vaccination. Here, we describe the SARS-CoV-2 neutralizing SP1-77 antibody that was generated from a humanized mouse model with a single human V _H 1-2 and Vκ1-33-associated with immensely diverse complementarity-determining-region-3 (CDR3) sequences. SP1-77 potently and broadly neutralizes SARS-CoV-2 variants of concern and binds the SARS-CoV-2 spike protein receptor-binding-domain (RBD) via a novel-CDR3-based mode. SP1-77 does not block RBD-binding to the ACE2-receptor or endocytosis step of viral entry, but rather blocks membrane fusion. Our findings provide the first mechanistic insight into how a non-ACE2 blocking antibody potently neutralizes SARS-CoV-2, which may inform strategies for designing vaccines that robustly neutralize current and future SARS-CoV-2 variants.

Low plasma levels of Proprotein Convertase Subtilisin/Kexin 9 (PCSK9) are associated with decreased low-density lipoprotein (LDL) cholesterol and a reduced risk of cardiovascular disease. PCSK9 binds to the epidermal growth factor-like repeat A (EGFA) domain of LDL receptors (LDLR), very low-density lipoprotein receptors (VLDLR), apolipoprotein E receptor 2 (ApoER2), and lipoprotein receptor–related protein 1 (LRP1) and accelerates their degradation, thus acting as a key regulator of lipid metabolism. Antibody and RNAi—based PCSK9 inhibitor treatments lower cholesterol and prevent cardiovascular incidents in patients, but their high-cost hampers market penetration. We sought to develop a safe, long-term and one-time solution to treat hyperlipidemia. We created a cDNA encoding a chimeric protein in which the extracellular N- terminus of red blood cells (RBCs) specific glycophorin A was fused to the LDLR EGFA domain and introduced this gene into mouse bone marrow hematopoietic stem and progenitor cells (HSPCs). Following transplantation into irradiated mice, the animals produced RBCs with the EGFA domain (EGFA-GPA RBCs) displayed on their surface. These animals showed significantly reduced plasma PCSK9 (66.5% decrease) and reduced LDL levels (40% decrease) for as long as 12 months post-transplantation. Furthermore, the EGFA- GPA mice remained lean for life and maintained normal body weight under a high-fat diet. Hematopoietic stem cell gene therapy can generate red blood cells expressing an EGFA—glycophorin A chimeric protein as a practical and long-term strategy for treating chronic hyperlipidemia and obesity.