Search

SUMMARYThe CD4 binding site (CD4bs) is a conserved epitope on HIV-1 envelope (Env) that can be targeted by protective broadly neutralizing antibodies (bnAbs). HIV-1 vaccines have not elicited CD4bs bnAbs for many reasons, including the CD4bs is occluded by glycans, immunogen expansion of appropriate naïve B cells, and selection of functional antibody mutations. Here, we demonstrate immunization of macaques with a CD4bs-targeting immunogen elicits neutralizing bnAb precursors with structural and genetic features of CD4-mimicking bnAbs. Structures of the CD4bs nAbs bound to HIV-1 Env demonstrated binding angles similar to human bnAbs and heavy chain second complementarity determining region-dependent binding characteristic of all known human CD4-mimicking bnAbs. Macaque nAbs were derived from variable and joining gene segments orthologous to the genes of human VH1-46-class bnAbs. This vaccine study initiated the B cells from which derive CD4bs bnAbs in primates, accomplishing the key first step in development of an effective HIV-1 vaccine.

A successful HIV-1 vaccine will require induction of a polyclonal neutralizing antibody (nAb) response, yet vaccine-mediated induction of such a response in primates remains a challenge. We found that a stabilized HIV-1 CH505 envelope (Env) trimer formulated with a Toll-like receptor 7/8 agonist induced potent HIV-1 polyclonal nAbs that correlated with protection from homologous simian-human immunodeficiency virus (SHIV) infection. The serum dilution that neutralized 50% of virus replication (ID 50 titer) required to protect 90% of macaques was 1:364 against the challenge virus grown in primary rhesus CD4 + T cells. Structural analyses of vaccine-induced nAbs demonstrated targeting of the Env CD4 binding site or the N156 glycan and the third variable loop base. Autologous nAb specificities similar to those elicited in macaques by vaccination were isolated from the human living with HIV from which the CH505 Env immunogen was derived. CH505 viral isolates were isolated that mutated the V1 to escape both the infection-induced and vaccine-induced antibodies. These results define the specificities of a vaccine-induced nAb response and the protective titers of HIV-1 vaccine–induced nAbs required to protect nonhuman primates from low-dose mucosal challenge by SHIVs bearing a primary transmitted/founder Env.

The impact of COVID-19 and the urgency to develop a vaccine against the SARS-CoV-2 virus cannot be overstated. The viral fusion spike (S) protein ectodomain is the primary target for vaccine development. Here we report an unexpected cold sensitivity of a stabilized SARS-CoV-2 ectodomain construct currently being widely used for immunogen design. We found that when stored at 22 or 37 °C for 1 week, the S-protein displayed well-ordered trimeric spikes by negative stain electron microscopy. However, storage at 4 °C reduced the trimeric spikes to

BibA, a group B streptococcus (GBS) surface protein, has been shown to protect the pathogen from phagocytic killing by sequestering a complement inhibitor: C4b-binding protein (C4BP). Here, the X-ray crystallographic structure of a GBS BibA fragment (BibA126–398) and a low-resolution small-angle X-ray scattering (SAXS) structure of the full-length N-terminal domain (BibA34–400) are described. The BibA126–398 fragment crystal structure displayed a novel and predominantly helical structure. The tertiary arrangement of helices forms four antiparallel three-helix-bundle-motif repeats, with one long helix from a bundle extending into the next. Multiple mutations on recombinant BibA34–400 delayed the degradation of the protein, and circular dichroism spectroscopy of BibA34–400 suggested a similar secondary-structure composition to that observed in the crystallized BibA126–398 fragment. A model was generated for the 92 N-terminal residues (BibA34–125) using structural similarity prediction programs, and a BibA34–400 model was generated by combining the coordinates of BibA34–126 and BibA126–398. The X-ray structure of BibA126–398 and the model of BibA34–400 fitted well into the calculated SAXS envelope. One possible binding site for the BibA N-terminal domain was localized to the N-terminal CCP (complement-control protein) domains of the C4BP α-chain, as indicated by the decreased binding of BibA to a ΔCCP1 C4BP α-chain mutant. In summary, it is suggested that the GBS surface protein BibA, which consists of three antiparallel α-helical-bundle motifs, is unique and belongs to a new class of Gram-positive surface adhesins.

Aided by extensive spike protein mutation, the SARS-CoV-2 Omicron variant overtook the previously dominant Delta variant. Spike conformation plays an essential role in SARS-CoV-2 evolution via changes in receptor binding domain (RBD) and neutralizing antibody epitope presentation affecting virus transmissibility and immune evasion. Here, we determine cryo-EM structures of the Omicron and Delta spikes to understand the conformational impacts of mutations in each. The Omicron spike structure revealed an unusually tightly packed RBD organization with long range impacts that were not observed in the Delta spike. Binding and crystallography revealed increased flexibility at the functionally critical fusion peptide site in the Omicron spike. These results reveal a highly evolved Omicron spike architecture with possible impacts on its high levels of immune evasion and transmissibility.

Aided by extensive spike protein mutation, the SARS-CoV-2 Omicron variant overtook the previously dominant Delta variant. Spike conformation plays an essential role in SARS-CoV-2 evolution via changes in receptor-binding domain (RBD) and neutralizing antibody epitope presentation, affecting virus transmissibility and immune evasion. Here, we determine cryo-EM structures of the Omicron and Delta spikes to understand the conformational impacts of mutations in each. The Omicron spike structure revealed an unusually tightly packed RBD organization with long range impacts that were not observed in the Delta spike. Binding and crystallography revealed increased flexibility at the functionally critical fusion peptide site in the Omicron spike. These results reveal a highly evolved Omicron spike architecture with possible impacts on its high levels of immune evasion and transmissibility.

Severe acute respiratory syndrome coronaviruses 1 (SARS-CoV) and 2 (SARS-CoV-2), including SARS-CoV-2 variants of concern, can cause deadly infections. The mortality associated with sarbecovirus infection underscores the importance of developing broadly effective countermeasures against them, which could be key in the prevention and mitigation of current and future zoonotic events. Here, we demonstrate the neutralization of SARS-CoV; bat coronaviruses WIV-1 and RsSHC014; and SARS-CoV-2 variants D614G, B.1.1.7, B.1.351, P.1, B.1.429, B.1.526, B.1.617.1, and B.1.617.2 by a receptor binding domain (RBD)–specific human antibody, DH1047. Prophylactic and therapeutic treatment with DH1047 was protective against SARS-CoV, WIV-1, RsSHC014, and SARS-CoV-2 B.1.351 infection in mice. Binding and structural analysis showed high affinity binding of DH1047 to an epitope that is highly conserved among sarbecoviruses. Thus, DH1047 is a broadly protective antibody that can prevent infection and mitigate outbreaks caused by SARS-related strains and SARS-CoV-2 variants. Our results also suggest that the conserved RBD epitope bound by DH1047 is a rational target for a universal sarbecovirus vaccine.

SARS-CoV in 2003, SARS-CoV-2 in 2019, and SARS-CoV-2 variants of concern (VOC) can cause deadly infections, underlining the importance of developing broadly effective countermeasures against Group 2B Sarbecoviruses, which could be key in the rapid prevention and mitigation of future zoonotic events. Here, we demonstrate the neutralization of SARS-CoV, bat CoVs WIV-1 and RsSHC014, and SARS-CoV-2 variants D614G, B.1.1.7, B.1.429, B1.351 by a receptor-binding domain (RBD)-specific antibody DH1047. Prophylactic and therapeutic treatment with DH1047 demonstrated protection against SARS-CoV, WIV-1, RsSHC014, and SARS-CoV-2 B1.351infection in mice. Binding and structural analysis showed high affinity binding of DH1047 to an epitope that is highly conserved among Sarbecoviruses. We conclude that DH1047 is a broadly neutralizing and protective antibody that can prevent infection and mitigate outbreaks caused by SARS-like strains and SARS-CoV-2 variants. Our results argue that the RBD conserved epitope bound by DH1047 is a rational target for pan Group 2B coronavirus vaccines.

SummaryNew SARS-CoV-2 variants that have accumulated multiple mutations in the spike (S) glycoprotein enable increased transmission and resistance to neutralizing antibodies. Here, we study the antigenic and structural impacts of the S protein mutations from four variants, one that was involved in transmission between minks and humans, and three that rapidly spread in human populations and originated in the United Kingdom, Brazil or South Africa. All variants either retained or improved binding to the ACE2 receptor. The B.1.1.7 (UK) and B.1.1.28 (Brazil) spike variants showed reduced binding to neutralizing NTD and RBD antibodies, respectively, while the B.1.351 (SA) variant showed reduced binding to both NTD- and RBD-directed antibodies. Cryo-EM structural analyses revealed allosteric effects of the mutations on spike conformations and revealed mechanistic differences that either drive inter-species transmission or promotes viral escape from dominant neutralizing epitopes.HighlightsCryo-EM structures reveal changes in SARS-CoV-2 S protein during inter-species transmission or immune evasion.Adaptation to mink resulted in increased ACE2 binding and spike destabilization.B.1.1.7 S mutations reveal an intricate balance of stabilizing and destabilizing effects that impact receptor and antibody binding.E484K mutation in B.1.351 and B.1.1.28 S proteins drives immune evasion by altering RBD conformation.S protein uses different mechanisms to converge upon similar solutions for altering RBD up/down positioning.

SUMMARYBetacoronaviruses (betaCoVs) caused the severe acute respiratory syndrome (SARS) and Middle East Respiratory Syndrome (MERS) outbreaks, and now the SARS-CoV-2 pandemic. Vaccines that elicit protective immune responses against SARS-CoV-2 and betaCoVs circulating in animals have the potential to prevent future betaCoV pandemics. Here, we show that immunization of macaques with a multimeric SARS-CoV-2 receptor binding domain (RBD) nanoparticle adjuvanted with 3M-052-Alum elicited cross-neutralizing antibody responses against SARS-CoV-1, SARS-CoV-2, batCoVs and the UK B.1.1.7 SARS-CoV-2 mutant virus. Nanoparticle vaccination resulted in a SARS-CoV-2 reciprocal geometric mean neutralization titer of 47,216, and robust protection against SARS-CoV-2 in macaque upper and lower respiratory tracts. Importantly, nucleoside-modified mRNA encoding a stabilized transmembrane spike or monomeric RBD protein also induced SARS-CoV-1 and batCoV cross-neutralizing antibodies, albeit at lower titers. These results demonstrate current mRNA vaccines may provide some protection from future zoonotic betaCoV outbreaks, and provide a platform for further development of pan-betaCoV nanoparticle vaccines.

SummarySARS-CoV-2 neutralizing antibodies (NAbs) protect against COVID-19. A concern regarding SARS-CoV-2 antibodies is whether they mediate disease enhancement. Here, we isolated NAbs against the receptor-binding domain (RBD) and the N-terminal domain (NTD) of SARS-CoV-2 spike from individuals with acute or convalescent SARS-CoV-2 or a history of SARS-CoV-1 infection. Cryo-electron microscopy of RBD and NTD antibodies demonstrated function-specific modes of binding. Select RBD NAbs also demonstrated Fc receptor-γ (FcγR)-mediated enhancement of virus infectionin vitro, while five non-neutralizing NTD antibodies mediated FcγR-independentin vitroinfection enhancement. However, both types of infection-enhancing antibodies protected from SARS-CoV-2 replication in monkeys and mice. Nonetheless, three of 31 monkeys infused with enhancing antibodies had higher lung inflammation scores compared to controls. One monkey had alveolar edema and elevated bronchoalveolar lavage inflammatory cytokines. Thus, whilein vitroantibody-enhanced infection does not necessarily herald enhanced infectionin vivo, increased lung inflammation can occur in SARS-CoV-2 antibody-infused macaques.

Betacoronaviruses caused the outbreaks of severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome, as well as the current pandemic of SARS coronavirus 2 (SARS-CoV-2)1-4. Vaccines that elicit protective immunity against SARS-CoV-2 and betacoronaviruses that circulate in animals have the potential to prevent future pandemics. Here we show that the immunization of macaques with nanoparticles conjugated with the receptor-binding domain of SARS-CoV-2, and adjuvanted with 3M-052 and alum, elicits cross-neutralizing antibody responses against bat coronaviruses, SARS-CoV and SARS-CoV-2 (including the B.1.1.7, P.1 and B.1.351 variants). Vaccination of macaques with these nanoparticles resulted in a 50% inhibitory reciprocal serum dilution (ID50) neutralization titre of 47,216 (geometric mean) for SARS-CoV-2, as well as in protection against SARS-CoV-2 in the upper and lower respiratory tracts. Nucleoside-modified mRNAs that encode a stabilized transmembrane spike or monomeric receptor-binding domain also induced cross-neutralizing antibody responses against SARS-CoV and bat coronaviruses, albeit at lower titres than achieved with the nanoparticles. These results demonstrate that current mRNA-based vaccines may provide some protection from future outbreaks of zoonotic betacoronaviruses, and provide a multimeric protein platform for the further development of vaccines against multiple (or all) betacoronaviruses.

The SARS-CoV-2 spike (S) protein is the target of vaccine design efforts to end the COVID-19 pandemic. Despite a low mutation rate, isolates with the D614G substitution in the S protein appeared early during the pandemic, and are now the dominant form worldwide. Here, we explore spike conformational changes and the effects of the D614G mutation on a soluble S ectodomain construct. Cryo-EM structures reveal altered RBD disposition; antigenicity and proteolysis experiments reveal structural changes and enhanced furin cleavage efficiency of the G614 variant. Furthermore, furin cleavage alters the up/down ratio of the Receptor Binding Domains (RBD) in the G614 S ectodomain, demonstrating an allosteric effect on RBD positioning triggered by changes in the SD2 region, that harbors residue 614 and the furin cleavage site. Our results elucidate SARS-CoV-2 spike conformational landscape and allostery, and have implications for vaccine design., Graphical Abstract, Highlights • SARS-CoV-2 S 2P mutations do not impact its structure, stability or antigenicity. • D614G mutation increases RBD “up” state and enhances S1/S2 junction proteolysis. • Structure and antigenicity reveal allostery between the S1/S2 junction and RBD. • SD2 anchors the mobile RBD and NTD, separating large S1 subunit motions from S2., SARS-CoV-2 spike undergoes large conformational changes during cell fusion. Gobeil et al. identify a subdomain anchor that limits large motions in the receptor binding subunit of the pre-fusion spike from propagating to its fusion subunit. They demonstrate that the D614G mutation increases rate of furin cleavage, which may impact infectivity.

The SARS-CoV-2 spike (S) protein is the target of vaccine design efforts to end the COVID-19 pandemic. Despite a low mutation rate, isolates with the D614G substitution in the S protein appeared early during the pandemic, and are now the dominant form worldwide. Here, we analyze the D614G mutation in the context of a soluble S ectodomain construct. Cryo-EM structures, antigenicity and proteolysis experiments suggest altered conformational dynamics resulting in enhanced furin cleavage efficiency of the G614 variant. Furthermore, furin cleavage altered the conformational dynamics of the Receptor Binding Domains (RBD) in the G614 S ectodomain, demonstrating an allosteric effect on the RBD dynamics triggered by changes in the SD2 region, that harbors residue 614 and the furin cleavage site. Our results elucidate SARS-CoV-2 spike conformational dynamics and allostery, and have implications for vaccine design.HighlightsSARS-CoV-2 S ectodomains with or without the K986P, V987P mutations have similar structures, antigenicity and stability.The D614G mutation alters S protein conformational dynamics.D614G enhances protease cleavage susceptibility at the S protein furin cleavage site.Cryo-EM structures reveal allosteric effect of changes at the S1/S2 junction on RBD dynamics.

SummaryThe HIV-1 envelope (Env) is comprised by mass of over 50% glycans. A goal of HIV-1 vaccine development is the induction of Env glycan-reactive broadly neutralizing antibodies (bnAbs). The 2G12 bnAb recognizes an Env glycan cluster using a unique variable heavy (VH) domain-swapped conformation that results in fragment antigen-binding (Fab) dimerization. Here we describe Fab-dimerized glycan (FDG)-reactive antibodies without VH-swapped domains from simian-human immunodeficiency virus (SHIV)-infected macaques that neutralized heterologous HIV-1 isolates. FDG precursors were boosted by vaccination in macaques, and were present in HIV-1-naïve humans with an average estimated frequency of one per 340,000 B cells. These data demonstrate frequent HIV-1 Env glycan-reactive bnAb B cell precursors in macaques and humans and reveal a novel strategy for their induction by vaccination.HighlightsDiscovery of Fab-dimerized HIV-1 glycan-reactive antibodies with a non-domain-swapped architectureFab-dimerized antibodies neutralize heterologous HIV-1 isolates.Antibodies with this architecture can be elicited by vaccination in macaques.Fab-dimerized antibodies are found in HIV-1 naïve humans.

SummaryThe COVID-19 pandemic caused by SARS-CoV-2 has escalated into a global crisis. The spike (S) protein that mediates cell entry and membrane fusion is the current focus of vaccine and therapeutic antibody development efforts. The S protein, like many other viral fusion proteins such as HIV-1 envelope (Env) and influenza hemagglutinin, is glycosylated with both complex and high mannose glycans. Here we demonstrate binding to the SARS-CoV-2 S protein by a category of Fab-dimerized glycan-reactive (FDG) HIV-1-induced broadly neutralizing antibodies (bnAbs). A 3.1 Å resolution cryo-EM structure of the S protein ectodomain bound to glycan-dependent HIV-1 bnAb 2G12 revealed a quaternary glycan epitope on the spike S2 domain involving multiple protomers. These data reveal a new epitope on the SARS-CoV-2 spike that can be targeted for vaccine design.HighlightsFab-dimerized, glycan-reactive (FDG) HIV-1 bnAbs cross-react with SARS-CoV-2 spike.3.1 Å resolution cryo-EM structure reveals quaternary S2 epitope for HIV-1 bnAb 2G12.2G12 targets glycans, at positions 709, 717 and 801, in the SARS-CoV-2 spike.Our studies suggest a common epitope for FDG antibodies centered around glycan 709.

BackgroundThe DHVI Division of Structural Biology seeks to use atomic level structural information for design of an effective HIV-1 vaccine. Through visualization of the HIV-1 envelope (Env) and its interactions with the human immune system, we obtain structural information that we translate into the rational development vaccine immunogensMethodsWe use negative stain electron microscopy (NSEM), cryo-electron microscopy (cryo-EM), and x-ray crystallography as the major structural techniques for visualization of HIV-1 Env, and combine these with biochemical and biophysical studies, as well as computational methods to obtain a basic understanding of the functions and interactions of the HIV-1 Env.Results:1.The DHVI NSEM pipeline runs on a daily basis to quality control vaccine immunogens for animal studies and other applications. Offering rapid sample turnover and economical operations, the NSEM pipeline is the most widely utilized resource of the DHVI Division of Structural Biology. Over the last year, the NSEM team has focused efforts on improving operational speed and data processing allowing high-quality visualization of a large variety of samples including HIV-1 Env immunogens, antibodies, nanoparticles, and VLPs. In the last year we have also expanded our NSEM studies to the analyses of serum samples and mucosal fluids.2.To understand the mechanism of HIV-1 entry we have determined structures of HIV-1 entry intermediates. We have determined a 3.8 Å resolution structure of a single CD4 bound to a closed HIV-1 Env trimer revealing new contacts of CD4 with Env. We have also structurally characterized an Env designed to prevent CD4-induced rearrangements by targeted disruption of an allosteric network modulating Env conformational changes.3.We have structurally characterized the HIV-1 glycan-V3 targeting DH270 Broadly Neutralizing Antibody Lineage. The structures revealed movements in the V1 loop and interactive glycans, shifts in antibody orientations, antibody VH-VL orientations, and antibody elbow angles, as the lineage progressed to maturation.4.We have solved a structure in complex with the HIV-1 Env immunogen Man5-enriched CH505.N279K.G458Y.SOSIP.664 of the unmutated common ancestor (UCA) of the HIV-1 CD4-binding site targeting CH235 Broadly Neutralizing Antibody Lineage. The structure revealed interactions of the N279K and G458Y mutations with the CDR L3 loop of CH235 UCA thus providing a structural understanding of the role of these mutations in facilitating binding to the CH235 UCA. (see also Henderson et al abstract)5.Using NSEM and cryo-EM we have characterized the structural properties of a novel class of 2G12-mimetic, yet non domain-swapped Fab dimer glycan-reactive (FDG) antibodies. These studies showed that the Fab-dimerized 2G12-like motif is more common than previously thought, and that creation of a Fab-dimerized paratope for an HIV-1 neutralizing antibody does not require VH domain-swapping.6.Finally, the structural team is an integral part of the CHAVD Kalma Immunogen Design Team, wherein we are defining the structural basis of bnAb affinity maturation to guide sequential immunogen design.Conclusions:These results highlight the power of structural information on HIV-1 vaccine design, from leveraging a basic understanding of HIV-1 entry mechanism for immunogen design, to rapid visualization of Env immunogens by NSEM for quality control, discovery of novel antibody interactions, and atomic level visualization of antibody/Env interactions.

The Gram-positive bacteriumStreptococcus pneumoniae, a major human pathogen, is a regular colonizer of the upper and lower respiratory tracts. Pneumococcal adherence and virulence factor A (PavA), a fibronectin-binding bacterial protein, fromS. pneumoniaeis an important facilitator of its colonization of host cells. In this study, the crystal structure of the N-terminal domain of PavA (SpPavA-N) determined at a resolution of 2.39 Å is reported. Each monomer of the dimeric protein consists of two domains (domains I and II) and a short α-helix (α6) at the C-terminus that are connected by elongated loops. Comparison of the SpPavA-N structure with that of its homolog fromStreptococcus suis(FBPS-N) revealed differences in α5, α6 and the domain II/α6 inter-loop region within domain II. The α5 helix of FBPS-N folds back toward domain I, whereas in SpPavA-N it adopts an elongated rod shape.

Extracellular serine protease (Esp) from Staphylococcus epidermidis is a glutamyl endopeptidase that inhibits the growth and formation of S. aureus biofilms. Previously, crystal structures of the matured and active Esp have been determined. Interestingly, many of the staphylococcal glutamyl endopeptidase zymogens, including V8 from Staphylococcus aureus and Esp from S. epidermidis, contain unusually long pro-peptide segments; however, their function is not known. With the aim of elucidating the function of these pro-peptide segments, crystal structures of the Esp zymogen (Pro-Esp) and its variants were determined. It was observed that the N-terminus of the Pro-Esp crystal structure is flexible and is not associated with the main body of the enzyme, unlike in the known active Esp structure. In addition, the loops that border the putative substrate-binding pocket of Pro-Esp are flexible and disordered; the structural components that are responsible for enzyme specificity and efficiency in serine proteases are disordered in Pro-Esp. However, the N-terminal locked Pro-Esp variants exhibit a rigid substrate-binding pocket similar to the active Esp structure and regain activity. These structural studies highlight the role of the N-terminus in stabilizing the structural components responsible for the activity and specificity of staphylococcal glutamyl endopeptidases.

SARS-CoV-2-neutralizing antibodies (NAbs) protect against COVID-19. A concern regarding SARS-CoV-2 antibodies is whether they mediate disease enhancement. Here, we isolated NAbs against the receptor-binding domain (RBD) or the N-terminal domain (NTD) of SARS-CoV-2 spike from individuals with acute or convalescent SARS-CoV-2 or a history of SARS-CoV infection. Cryo-electron microscopy of RBD and NTD antibodies demonstrated function-specific modes of binding. Select RBD NAbs also demonstrated Fc receptor-γ (FcγR)-mediated enhancement of virus infection in vitro, while five non-neutralizing NTD antibodies mediated FcγR-independent in vitro infection enhancement. However, both types of infection-enhancing antibodies protected from SARS-CoV-2 replication in monkeys and mice. Three of 46 monkeys infused with enhancing antibodies had higher lung inflammation scores compared to controls. One monkey had alveolar edema and elevated bronchoalveolar lavage inflammatory cytokines. Thus, while in vitro antibody-enhanced infection does not necessarily herald enhanced infection in vivo, increased lung inflammation can rarely occur in SARS-CoV-2 antibody-infused macaques., Graphical abstract, Convalescent human-derived SARS-CoV-2 RBD and NTD antibodies mediated neutralization as well as infection enhancement in vitro, yet infusion of these antibodies in mice or cynomolgus macaques resulted in suppression of virus replication.

Natural antibodies (Abs) can target host glycans on the surface of pathogens. We studied the evolution of glycan-reactive B cells of rhesus macaques and humans using glycosylated HIV-1 envelope (Env) as a model antigen. 2G12 is a broadly neutralizing Ab (bnAb) that targets a conserved glycan patch on Env of geographically diverse HIV-1 strains using a unique heavy-chain (VH) domain-swapped architecture that results in fragment antigen-binding (Fab) dimerization. Here, we describe HIV-1 Env Fab-dimerized glycan (FDG)-reactive bnAbs without VH-swapped domains from simian-human immunodeficiency virus (SHIV)-infected macaques. FDG Abs also recognized cell-surface glycans on diverse pathogens, including yeast and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike. FDG precursors were expanded by glycan-bearing immunogens in macaques and were abundant in HIV-1-naive humans. Moreover, FDG precursors were predominately mutated IgM+IgD+CD27+, thus suggesting that they originated from a pool of antigen-experienced IgM+ or marginal zone B cells., Graphical abstract, Structural and functional analyses identify a category of glycan-reactive antibodies in macaques and humans that are marked by the dimerization of the antigen-binding fragment. These antibodies are involved in HIV neutralization and also recognize the S2 protein of SARS-CoV-2.

The second complement component C2 is a multidomain serine protease that provides catalytic activity to the C3 and C5 convertases of classical and lectin pathways of complement. Formation of these convertases requires the Mg-dependent binding of C2 to C4b and subsequent cleavage of C2 by C1s or mannose-binding lectin-associated serine protease 2, respectively.

Background: Esp, a secreted protease of Staphylococcus epidermidis, blocks biofilm formation of Staphylococcus aureus and its ability to colonize human nares. Results: Esp cleaves autolysin, thereby preventing the release of staphylococcal DNA as biofilm matrix. Conclusion: Secreted proteases control S. aureus biofilm development and host colonization. Significance: Methods that promote autolysin degradation may also prevent S. aureus colonization of humans., Staphylococcus epidermidis, a commensal of humans, secretes Esp protease to prevent Staphylococcus aureus biofilm formation and colonization. Blocking S. aureus colonization may reduce the incidence of invasive infectious diseases; however, the mechanism whereby Esp disrupts biofilms is unknown. We show here that Esp cleaves autolysin (Atl)-derived murein hydrolases and prevents staphylococcal release of DNA, which serves as extracellular matrix in biofilms. The three-dimensional structure of Esp was revealed by x-ray crystallography and shown to be highly similar to that of S. aureus V8 (SspA). Both atl and sspA are necessary for biofilm formation, and purified SspA cleaves Atl-derived murein hydrolases. Thus, S. aureus biofilms are formed via the controlled secretion and proteolysis of autolysin, and this developmental program appears to be perturbed by the Esp protease of S. epidermidis.