Most monoclonal antibodies (mAbs) generated from humans infected or vaccinated with the 2009 pandemic H1N1 (pdmH1N1) influenza virus targeted the hemagglutinin (HA) stem. These anti-HA stem mAbs mostly used IGHV1-69 and bound readily to epitopes on the conventional seasonal influenza and pdmH1N1 vaccines. The anti-HA stem mAbs neutralized pdmH1N1, seasonal influenza H1N1 and avian H5N1 influenza viruses by inhibiting HA-mediated fusion of membranes and protected against and treated heterologous lethal infections in mice with H5N1 influenza virus. This demonstrated that therapeutic mAbs could be generated a few months after the new virus emerged. Human immunization with the pdmH1N1 vaccine induced circulating antibodies that when passively transferred, protected mice from lethal, heterologous H5N1 influenza infections. We observed that the dominant heterosubtypic antibody response against the HA stem correlated with the relative absence of memory B cells against the HA head of pdmH1N1, thus enabling the rare heterosubtypic memory B cells induced by seasonal influenza and specific for conserved sites on the HA stem to compete for T-cell help. These results support the notion that broadly protective antibodies against influenza would be induced by successive vaccination with conventional influenza vaccines based on subtypes of HA in viruses not circulating in humans.

New variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continue to arise and prolong the coronavirus disease 2019 (COVID-19) pandemic. Here we used a cell-free expression workflow to rapidly screen and optimize constructs containing multiple computationally designed miniprotein inhibitors of SARS-CoV-2. We found the broadest efficacy with a homo-trimeric version of the 75-residue angiotensin converting enzyme 2 (ACE2) mimic AHB2 (TRI2-2) designed to geometrically match the trimeric spike architecture. In the cryo-electron microscopy structure, TRI2 formed a tripod on top of the spike protein which engaged all three receptor binding domains (RBDs) simultaneously as in the design model. TRI2-2 neutralized Omicron (B.1.1.529), Delta (B.1.617.2), and all other variants tested with greater potency than that of monoclonal antibodies used clinically for the treatment of COVID-19. TRI2-2 also conferred prophylactic and therapeutic protection against SARS-CoV-2 challenge when administered intranasally in mice. Designed miniprotein receptor mimics geometrically arrayed to match pathogen receptor binding sites could be a widely applicable antiviral therapeutic strategy with advantages over antibodies and native receptor traps. By comparison, the designed proteins have resistance to viral escape and antigenic drift by construction, precisely tuned avidity, and greatly reduced chance of autoimmune responses.

Immunoglobulin genes are generated somatically through specialized mechanisms resulting in a vast repertoire of antigen-binding sites. Despite the stochastic nature of these processes, the V-genes that encode most of the antigen-combining site are under positive evolutionary selection, raising the possibility that V-genes have been selected to encode key structural features of binding sites of protective antibodies against certain pathogens. Human, neutralizing antibodies to human cytomegalovirus that bind the AD-2S1 epitope on its gB envelope protein repeatedly use a pair of well-conserved, germline V-genes IGHV3-30 and IGKV3-11. Here, we present crystallographic, kinetic and thermodynamic analyses of the binding site of such an antibody and that of its primary immunoglobulin ancestor. These show that these germline V-genes encode key side chain contacts with the viral antigen and thereby dictate key structural features of the hypermutated, high-affinity neutralizing antibody. Vgenes may thus encode an innate, protective immunological memory that targets vulnerable, invariant sites on multiple pathogens.

Hsp47, a 47 kDa heat shock protein whose expression level parallels that of collagen, has been regarded as a collagen-specific molecular chaperone. Studies from other laboratories have established the association of Hsp47 with the nascent as well as the triple-helical procollagen molecule in the endoplasmic reticulum and its dissociation from procollagen in the Golgi. One of several roles suggested for Hsp47 in collagen biosynthesis is the prevention of aggregation of procollagen in the endoplasmic reticulum. However, no experimental evidence has been available to verify this suggestion. In the present study we have followed the aggregation of mature triple-helical collagen molecules into fibrils by using turbidimetric measurements in the absence and presence of Hsp47. In the pH range 6-7, fibril formation of type I collagen, as monitored by turbidimetry, proceeds with a lag of approx. 10 min and levels off by approx. 60 min. The addition of Hsp47 at pH 7 effectively inhibits fibril formation at and above a 1:1 molar ratio of Hsp47 to triple-helical collagen. This inhibition is markedly pH-dependent, being significantly diminished at pH 6. CD and fluorescence spectral data of Hsp47 in the pH range 4.2-7.4 reveal a significant alteration in its structure at pH values below 6.2, with a decrease in alpha-helix and an increase in beta-structure. This conformational change is likely to be the basis of the decreased binding of Hsp47 to collagen in vitro at pH 6.3 as well as its inability to inhibit collagen fibril formation at this pH. Our results also provide a functional assay for Hsp47 that can be used in studies on collagen and Hsp47 interactions.

Human granulocyte macrophage colony-stimulating factor (hGM-CSF) is a haematopoietic growth factor and proinflammatory cytokine. Recombinant hGM-CSF is important not only as a research tool but also as a biotherapeutic. However, rhGM-CSF expressed in E. coli is known to form inclusion bodies of misfolded, aggregated protein. Refolding and subsequent purification of rhGM-CSF from inclusion bodies is difficult with low yields of bioactive protein being produced. Here we describe a method for the isolation, refolding and purification of bioactive rhGM-CSF from inclusion bodies. The method is straightforward, not requiring extensive experience in protein refolding nor purification and using standard laboratory equipment.

The origin of pathogenic autoantibodies remains unknown. Idiopathic pulmonary alveolar proteinosis is caused by autoantibodies against granulocyte–macrophage colony-stimulating factor (GM-CSF). We generated 19 monoclonal autoantibodies against GM-CSF from six patients with idiopathic pulmonary alveolar proteinosis. The autoantibodies used multiple V genes, excluding preferred V-gene use as an etiology, and targeted at least four nonoverlapping epitopes on GM-CSF, suggesting that GM-CSF is driving the autoantibodies and not a B-cell epitope on a pathogen cross-reacting with GM-CSF. The number of somatic mutations in the autoantibodies suggests that the memory B cells have been helped by T cells and re-entered germinal centers. All autoantibodies neutralized GM-CSF bioactivity, with general correlations to affinity and off-rate. The binding of certain autoantibodies was changed by point mutations in GM-CSF that reduced binding to the GM-CSF receptor. Those monoclonal autoantibodies that potently neutralize GM-CSF may be useful in treating inflammatory disease, such as rheumatoid arthritis and multiple sclerosis, cancer, and pain.

Hsp47 is a collagen-specific molecular chaperone whose activity has been implicated in the pathogenesis of fibrotic diseases. Here, we describe the development of an assay for screening libraries of chemical compounds for inhibitors of Hsp47. A preliminary screen of 2080 compounds identified four that demonstrated inhibitory activity against Hsp47 in vitro, with IC(50) values ranging from 3 to 27 muM. Compounds identified through this method may provide the basis for development of novel antifibrotic therapeutics.

The human Ab response to certain pathogens is oligoclonal, with preferred IgV genes being used more frequently than others. A pair of such preferred genes, IGVK3-11 and IGVH3-30, contributes to the generation of protective Abs directed against the 23F serotype of the pneumonococcal capsular polysaccharide of Streptococcus pneumoniae and against the AD-2S1 peptide of the gB membrane protein of human CMV. Structural analyses of Fab fragments of mAbs 023.102 and pn132p2C05 in complex with portions of the 23F polysaccharide revealed five germline-encoded residues in contact with the key component, l-rhamnose. In the case of the AD-2S1 peptide, the KE5 Fab fragment complex identified nine germline-encoded contact residues. Two of these germline-encoded residues, Arg91L and Trp94L, contact both the l-rhamnose and the AD-2S1 peptide. Comparison of the respective paratopes that bind to carbohydrate and protein reveals that stochastic diversity in both CDR3 loops alone almost exclusively accounts for their divergent specificity. Combined evolutionary pressure by human CMV and the 23F serotype of S. pneumoniae acted on the IGVK3-11 and IGVH3-30 genes as demonstrated by the multiple germline-encoded amino acids that contact both l-rhamnose and AD-2S1 peptide.