Structural Repertoire of HIV-1-Neutralizing Antibodies Targeting the CD4 Supersite in 14 Donors.

The site on the HIV-1 gp120 glycoprotein that binds the CD4 receptor is recognized by broadly reactive antibodies, several of which neutralize over 90% of HIV-1 strains. To understand how antibodies achieve such neutralization, we isolated CD4-binding-site (CD4bs) antibodies and analyzed 16 co-crystal structures -8 determined here- of CD4bs antibodies from 14 donors. The 16 antibodies segregated by recognition mode and developmental ontogeny into two types: CDR H3-dominated and VH-gene-restricted. Both could achieve greater than 80% neutralization breadth, and both could develop in the same donor. Although paratope chemistries differed, all 16 gp120-CD4bs antibody complexes showed geometric similarity, with antibody-neutralization breadth correlating with antibody-angle of approach relative to the most effective antibody of each type. The repertoire for effective recognition of the CD4 supersite thus comprises antibodies with distinct paratopes arrayed about two optimal geometric orientations, one achieved by CDR H3 ontogenies and the other achieved by VH-gene-restricted ontogenies.

A non-neutralizing antibody broadly protects against influenza virus infection by engaging effector cells.

Hemagglutinin (HA) is the immunodominant protein of the influenza virus. We previously showed that mice injected with a monoglycosylated influenza A HA (HAmg) produced cross-strain-reactive antibodies and were better protected than mice injected with a fully glycosylated HA (HAfg) during lethal dose challenge. We employed a single B-cell screening platform to isolate the cross-protective monoclonal antibody (mAb) 651 from mice immunized with the HAmg of A/Brisbane/59/2007 (H1N1) influenza virus (Bris/07). The mAb 651 recognized the head domain of a broad spectrum of HAs from groups 1 and 2 influenza A viruses and offered prophylactic and therapeutic efficacy against A/California/07/2009 (H1N1) (Cal/09) and Bris/07 infections in mice. The antibody did not possess neutralizing activity; however, antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis mediated by natural killer cells and alveolar macrophages were important in the protective efficacy of mAb 651. Together, this study highlighted the significance of effector functions for non-neutralizing antibodies to exhibit protection against influenza virus infection.

Attitude towards hereditary cancer risk management among women with cancer in Taiwan.

BACKGROUND: Risk management intentions prior to genetic counseling predict risk management uptake following genetic testing. Limited studies examined the attitude and understanding towards genetic counseling/testing in underserved countries. The purposes of this study were to explore knowledge and attitude towards genetic counseling, testing, and risk management for breast and ovarian cancer, and to understand the factors influencing risk management intentions in women with cancer in Taiwan. METHODS: Cross-sectional with correlational design was used in this study. Participants were enrolled for genetic testing based on clinical criteria suspected of having hereditary cancer. Survey was conducted using a standardized questionnaire including (1) demographics and personal/family history of cancer; (2) prior experience or consideration of genetic testing and reasons for not considering; (3) perception and attitude towards genetic counseling; and (4) intentions for risk management with a hypothetical BRCA1 mutation status. Multinomial logistic regression was used to analyze the predictors of participants' intentions for cancer risk management strategies. RESULTS: A total of 430 women with cancer were analyzed in which 51.6% had family history of cancer in first-degree relatives. Only 30.7% had considered genetic testing and 28.4% had known about genetic counseling prior to the study. When prompted with the services of genetic counseling, the attitude towards genetic counseling was fairly positive (score of 19.8 ± 2.9 out of 25). Given hypothetical BRCA1 mutation status, enhanced breast cancer screening with annual breast MRI was much more accepted than cancer risk reducing interventions. More positive attitude towards genetic counseling (each score point increase) was associated with higher odds of intention for breast MRI (OR 1.20, 95% CI 1.09-1.32) and preventive tamoxifen (OR 1.11, 95% CI 1.02-1.22). Having considered genetic testing prior to the study was associated with higher odds of intention for all four risk management strategies: breast MRI (OR 2.99, 95% CI 1.46-6.11), preventive tamoxifen (OR 1.79, 95% CI 1.00-3.17), risk-reducing mastectomy (OR 2.24, 95% CI 1.13-4.42), and risk-reducing salpingo-oophorectomy (OR 2.69, 95% CI 1.27-6.93). CONCLUSION: Knowledge of genetic testing and positive attitude towards genetic counseling were associated with increased willingness to consider cancer risk management strategies for hereditary breast and ovarian cancer syndrome. Given the limited knowledge on genetic testing and counseling in the studied population, increasing public awareness of these services may increase adoption of the risk management strategies.

Antibodyomics: bioinformatics technologies for understanding B-cell immunity to HIV-1.

Numerous antibodies have been identified from HIV-1-infected donors that neutralize diverse strains of HIV-1. These antibodies may provide the basis for a B cell-mediated HIV-1 vaccine. However, it has been unclear how to elicit similar antibodies by vaccination. To address this issue, we have undertaken an informatics-based approach to understand the genetic and immunologic processes controlling the development of HIV-1-neutralizing antibodies. As DNA sequencing comprises the fastest growing database of biological information, we focused on incorporating next-generation sequencing of B-cell transcripts to determine the origin, maturation pathway, and prevalence of broadly neutralizing antibody lineages (Antibodyomics1, 2, 4, and 6). We also incorporated large-scale robotic analyses of serum neutralization to identify and quantify neutralizing antibodies in donor cohorts (Antibodyomics3). Statistical analyses furnish another layer of insight (Antibodyomics5), with physical characteristics of antibodies and their targets through molecular dynamics simulations (Antibodyomics7) and free energy perturbation analyses (Antibodyomics8) providing information-rich output. Functional interrogation of individual antibodies (Antibodyomics9) and synthetic antibody libraries (Antibodyomics10) also yields multi-dimensional data by which to understand and improve antibodies. Antibodyomics, described here, thus comprise resolution-enhancing tools, which collectively embody an information-driven discovery engine aimed toward the development of effective B cell-based vaccines.

Germline breast cancer susceptibility gene mutations and breast cancer outcomes.

BACKGROUND: It is unclear whether germline breast cancer susceptibility gene mutations affect breast cancer related outcomes. We wanted to evaluate mutation patterns in 20 breast cancer susceptibility genes and correlate the mutations with clinical characteristics to determine the effects of these germline mutations on breast cancer prognosis. METHODS: The study cohort included 480 ethnic Chinese individuals in Taiwan with at least one of the six clinical risk factors for hereditary breast cancer: family history of breast or ovarian cancer, young age of onset for breast cancer, bilateral breast cancer, triple negative breast cancer, both breast and ovarian cancer, and male breast cancer. PCR-enriched amplicon-sequencing on a next generation sequencing platform was used to determine the germline DNA sequences of all exons and exon-flanking regions of the 20 genes. Protein-truncating variants were identified as pathogenic. RESULTS: We detected a 13.5% carrier rate of pathogenic germline mutations, with BRCA2 being the most prevalent and the non-BRCA genes accounting for 38.5% of the mutation carriers. BRCA mutation carriers were more likely to be diagnosed of breast cancer with lymph node involvement (66.7% vs 42.6%; P = 0.011), and had significantly worse breast cancer specific outcomes. The 5-year disease-free survival was 73.3% for BRCA mutation carriers and 91.1% for non-carriers (hazard ratio for recurrence or death 2.42, 95% CI 1.29-4.53; P = 0.013). After adjusting for clinical prognostic factors, BRCA mutation remained an independent poor prognostic factor for cancer recurrence or death (adjusted hazard ratio 3.04, 95% CI 1.40-6.58; P = 0.005). Non-BRCA gene mutation carriers did not exhibit any significant difference in cancer characteristics or outcomes compared to those without detected mutations. Among the risk factors for hereditary breast cancer, the odds of detecting a germline mutation increased significantly with having bilateral breast cancer (adjusted odds ratio 3.27, 95% CI 1.64-6.51; P = 0.0008) or having more than one risk factor (odds ratio 2.07, 95% CI 1.22-3.51; P = 0.007). CONCLUSIONS: Without prior knowledge of the mutation status, BRCA mutation carriers had more advanced breast cancer on initial diagnosis and worse cancer-related outcomes. Optimal approach to breast cancer treatment for BRCA mutation carriers warrants further investigation.

Origins of specificity and affinity in antibody-protein interactions.

Natural antibodies are frequently elicited to recognize diverse protein surfaces, where the sequence features of the epitopes are frequently indistinguishable from those of nonepitope protein surfaces. It is not clearly understood how the paratopes are able to recognize sequence-wise featureless epitopes and how a natural antibody repertoire with limited variants can recognize seemingly unlimited protein antigens foreign to the host immune system. In this work, computational methods were used to predict the functional paratopes with the 3D antibody variable domain structure as input. The predicted functional paratopes were reasonably validated by the hot spot residues known from experimental alanine scanning measurements. The functional paratope (hot spot) predictions on a set of 111 antibody-antigen complex structures indicate that aromatic, mostly tyrosyl, side chains constitute the major part of the predicted functional paratopes, with short-chain hydrophilic residues forming the minor portion of the predicted functional paratopes. These aromatic side chains interact mostly with the epitope main chain atoms and side-chain carbons. The functional paratopes are surrounded by favorable polar atomistic contacts in the structural paratope-epitope interfaces; more that 80% these polar contacts are electrostatically favorable and about 40% of these polar contacts form direct hydrogen bonds across the interfaces. These results indicate that a limited repertoire of antibodies bearing paratopes with diverse structural contours enriched with aromatic side chains among short-chain hydrophilic residues can recognize all sorts of protein surfaces, because the determinants for antibody recognition are common physicochemical features ubiquitously distributed over all protein surfaces.

Prediction of FMN-binding residues with three-dimensional probability distributions of interacting atoms on protein surfaces.

Flavin mono-nucleotide (FMN) is a cofactor which is involved in many biological reactions. The insights on protein-FMN interactions aid the protein functional annotation and also facilitate in drug design. In this study, we have established a new method, making use of an encoding scheme of the three-dimensional probability density maps that describe the distributions of 40 non-covalent interacting atom types around protein surfaces, to predict FMN-binding sites on protein surfaces. One machine learning model was trained for each of the 30 protein atom types to predict tentative FMN-binding sites on protein structures. The method's capability was evaluated by five-fold cross-validation on a dataset containing 81 non-redundant FMN-binding protein structures and further tested on independent datasets of 30 and 15 non-redundant protein structures respectively. These predictions achieved an accuracy of 0.94, 0.94 and 0.96 with the Matthews correlation coefficient (MCC) of 0.53, 0.53 and 0.65 respectively for the three protein structure sets. The prediction capability is superior to the existing method. This is the first structure-based approach that does not rely on evolutionary information for predicting FMN-interacting residues. The webserver for the prediction is available at http://ismblab.genomics.sinica.edu.tw/.

E339...R416 salt bridge of nucleoprotein as a feasible target for influenza virus inhibitors.

The nucleoprotein (NP) of the influenza virus exists as trimers, and its tail-loop binding pocket has been suggested as a potential target for antiinfluenza therapeutics. The possibility of NP as a drug target was validated by the recent reports that nucleozin and its analogs can inhibit viral replication by inducing aggregation of NP trimers. However, these inhibitors were identified by random screening, and the binding site and inhibition mechanism are unclear. We report a rational approach to target influenza virus with a new mechanism--disruption of NP-NP interaction. Consistent with recent work, E339A, R416A, and deletion mutant Δ402-428 were unable to support viral replication in the absence of WT NP. However, only E339A and R416A could form hetero complex with WT NP, but the complex was unable to bind the RNA polymerase, leading to inhibition of viral replication. These results demonstrate the importance of the E339…R416 salt bridge in viral survival and establish the salt bridge as a sensitive antiinfluenza target. To provide further support, we showed that peptides encompassing R416 can disrupt NP-NP interaction and inhibit viral replication. Finally we performed virtual screening to target E339…R416, and some small molecules identified were shown to disrupt the formation of NP trimers and inhibit replication of WT and nucleozin-resistant strains. This work provides a new approach to design antiinfluenza drugs.

Computational Analysis of Antibody Paratopes for Antibody Sequences in Antibody Libraries.

To ensure the functionalities of the antibodies in phage-displayed synthetic antibody libraries, we use computational method to evaluate the designs of the antibody libraries. The computational methodologies developed in our lab for designing antibody library provide rich information on the function of the designed antibody sequences-adequate antibody designs for a specific antigen type should have predicted paratopes for the antigen type. This computational assessment of the designed antibody sequences helps eliminate non-functional designs before proceeding to construct the library designs in the wet lab. As such, only reasonable antibody designs are constructed for antibody discoveries.

Negligible risk of surface transmission of SARS-CoV-2 in public transportation.

BACKGROUND: Exposure to pathogens in public transport systems is a common means of spreading infection, mainly by inhaling aerosol or droplets from infected individuals. Such particles also contaminate surfaces, creating a potential surface-transmission pathway. METHODS: A fast acoustic biosensor with an antifouling nano-coating was introduced to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on exposed surfaces in the Prague Public Transport System. Samples were measured directly without pre-treatment. Results with the sensor gave excellent agreement with parallel quantitative reverse-transcription polymerase chain reaction (qRT-PCR) measurements on 482 surface samples taken from actively used trams, buses, metro trains and platforms between 7 and 9 April 2021, in the middle of the lineage Alpha SARS-CoV-2 epidemic wave when 1 in 240 people were COVID-19 positive in Prague. RESULTS: Only ten of the 482 surface swabs produced positive results and none of them contained virus particles capable of replication, indicating that positive samples contained inactive virus particles and/or fragments. Measurements of the rate of decay of SARS-CoV-2 on frequently touched surface materials showed that the virus did not remain viable longer than 1-4 h. The rate of inactivation was the fastest on rubber handrails in metro escalators and the slowest on hard-plastic seats, window glasses and stainless-steel grab rails. As a result of this study, Prague Public Transport Systems revised their cleaning protocols and the lengths of parking times during the pandemic. CONCLUSIONS: Our findings suggest that surface transmission played no or negligible role in spreading SARS-CoV-2 in Prague. The results also demonstrate the potential of the new biosensor to serve as a complementary screening tool in epidemic monitoring and prognosis.

Structure and immunological characterization of the capsular polysaccharide of a pyrogenic liver abscess caused by Klebsiella pneumoniae: activation of macrophages through Toll-like receptor 4.

The active components of a primary pyrogenic liver abscess (PLA) Klebsiella pneumoniae in stimulating cytokine expression in macrophages are still unclear. The capsular polysaccharide (CPS) of PLA K. pneumoniae is important in determining clinical manifestations, and we have shown that it consists of repeating units of the trisaccharide (→3)-ß-D-Glc-(1→4)-[2,3-(S)-pyruvate]-ß-D-GlcA-(1→4)-α-L-Fuc-(1→) and has the unusual feature of extensive pyruvation of glucuronic acid and acetylation of C(2)-OH or C(3)-OH of fucose. We demonstrated that PLA K. pneumoniae CPS induces secretion of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) by macrophages through Toll-like receptor 4 (TLR4) and that this effect was lost when pyruvation and O-acetylation were chemically destroyed. Furthermore, expression of TNF-α and IL-6 in PLA K. pneumoniae CPS-stimulated macrophages was shown to be regulated by the TLR4/ROS/PKC-δ/NF-κB, TLR4/PI3-kinase/AKT/NF-κB, and TLR4/MAPK signaling pathways.

Antibody CDR amino acids underlying the functionality of antibody repertoires in recognizing diverse protein antigens.

Antibodies recognize protein antigens with exquisite specificity in a complex aqueous environment, where interfacial waters are an integral part of the antibody-protein complex interfaces. In this work, we elucidate, with computational analyses, the principles governing the antibodies' specificity and affinity towards their cognate protein antigens in the presence of explicit interfacial waters. Experimentally, in four model antibody-protein complexes, we compared the contributions of the interaction types in antibody-protein antigen complex interfaces with the antibody variants selected from phage-displayed synthetic antibody libraries. Evidently, the specific interactions involving a subset of aromatic CDR (complementarity determining region) residues largely form the predominant determinant underlying the specificity of the antibody-protein complexes in nature. The interfacial direct/water-mediated hydrogen bonds accompanying the CDR aromatic interactions are optimized locally but contribute little in determining the epitope location. The results provide insights into the phenomenon that natural antibodies with limited sequence and structural variations in an antibody repertoire can recognize seemingly unlimited protein antigens. Our work suggests guidelines in designing functional artificial antibody repertoires with practical applications in developing novel antibody-based therapeutics and diagnostics for treating and preventing human diseases.

Engineering anti-vascular endothelial growth factor single chain disulfide-stabilized antibody variable fragments (sc-dsFv) with phage-displayed sc-dsFv libraries.

Phage display of antibody fragments from natural or synthetic antibody libraries with the single chain constructs combining the variable fragments (scFv) has been one of the most prominent technologies in antibody engineering. However, the nature of the artificial single chain constructs results in unstable proteins expressed on the phage surface or as soluble proteins secreted in the bacterial culture medium. The stability of the variable domain structures can be enhanced with interdomain disulfide bond, but the single chain disulfide-stabilized constructs (sc-dsFv) have yet to be established as a feasible format for bacterial phage display due to diminishing expression levels on the phage surface in known phage display systems. In this work, biological combinatorial searches were used to establish that the c-region of the signal sequence is critically responsible for effective expression and functional folding of the sc-dsFv on the phage surface. The optimum signal sequences increase the expression of functional sc-dsFv by 2 orders of magnitude compared with wild-type signal sequences, enabling the construction of phage-displayed synthetic antivascular endothelial growth factor sc-dsFv libraries. Comparison of the scFv and sc-dsFv variants selected from the phage-displayed libraries for vascular endothelial growth factor binding revealed the sequence preference differences resulting from the interdomain disulfide bond. These results underlie a new phage display format for antibody fragments with all the benefits from the scFv format but without the downside due to the instability of the dimeric interface in scFv.

A practical synthesis of zanamivir phosphonate congeners with potent anti-influenza activity.

Two phosphonate compounds 1a (4-amino-1-phosphono-DANA) and 1b (phosphono-zanamivir) are synthesized and shown more potent than zanamivir against the neuraminidases of avian and human influenza viruses, including the oseltamivir-resistant strains. For the first time, the practical synthesis of these phosphonate compounds is realized by conversion of sialic acid to peracetylated phosphono-DANA diethyl ester (5) as a key intermediate in three steps by a novel approach. In comparison with zanamivir, the high affinity of 1a and 1b can be partly attributable to the strong electrostatic interactions of their phosphonate groups with the three arginine residues (Arg118, Arg292, and Arg371) in the active site of neuraminidases. These phosphonates are nontoxic to the human 293T cells; they protect cells from influenza virus infection with EC(50) values in low-nanomolar range, including the wild-type WSN (H1N1), the 2009 pandemic (H1N1), the oseltamivir-resistant H274Y (H1N1), RG14 (H5N1), and Udorn (H3N2) influenza strains.

Effects of signal sequence on phage-displayed disulfide-stabilized single chain antibody variable fragment (sc-dsFv) libraries.

Phage-displayed single chain variable fragment (scFv) libraries are powerful tools in antibody engineering. Disulfide-stabilized scFv (sc-dsFv) with an interface disulfide bond is structure-wise more stable than the corresponding scFv. A set of recently discovered signal sequences replacing the wild type (pelB) signal peptidase cleavage site in the c-region has been shown to be effective in rescuing the expression of sc-dsFv libraries on the phage surface. However, the effects of the other regions of the signal sequence on the expression of the sc-dsFv libraries and on the formation of the interface disulfide bond in the phage-displayed sc-dsFv have not been clear. In this work, selected novel signal sequence variants in the h-region were shown to be equally effective in promoting sc-dsFv library expression on the phage surface; the expression level and complexity of the sc-dsFv libraries were comparable to the corresponding scFv libraries produced with the wild-type (pelB) signal sequence. The interface disulfide bond in the phage-displayed sc-dsFv was proven to form to a large extent in the library variant ensemble generated with signal sequence variants in both the h-region and the c-region. The sc-dsFv engineering platform established in this work can be applied to many of the known scFv molecules which are in need of a more stable version for the applications under harsh conditions or for longer shelf-life.

Molecular evolution of cystine-stabilized miniproteins as stable proteinaceous binders.

Small cystine-stabilized proteins are desirable scaffolds for therapeutics and diagnostics. Specific folding and binding properties of the proteinaceous binders can be engineered with combinatorial protein libraries in connection with artificial molecular evolution. The combinatorial protein libraries are composed of scaffold variants with random sequence variation, which inevitably produces a portion of the library sequences incompatible with the parent structure. Here, we used artificial molecular evolution to elucidate structure-determining residues in a smallest cystine-stabilized scaffold. The structural determinant information was then applied to designing cystine-stabilized miniproteins binding to human vascular endothelial growth factor. This work demonstrated a general methodology on engineering artificial cystine-stabilized proteins as antibody mimetics with simultaneously enhanced folding and binding properties.

Structure-based Development of Human Interleukin-1ß-Specific Antibody That Simultaneously Inhibits Binding to Both IL-1RI and IL-1RAcP.

Interleukin-1ß (IL-1ß) is a potent pleiotropic cytokine playing a central role in protecting cells from microbial pathogen infection or endogenous stress. After it binds to IL-1RI and recruits IL-1 receptor accessory protein (IL-1RAcP), signaling culminates in activation of NF-κB. Many pathophysiological diseases have been attributed to the derailment of IL-1ß regulation. Several blocking reagents have been developed based on two mechanisms: blocking the binding of IL-1ß to IL-1RI or inhibiting the recruitment of IL-1RAcP to the IL-1ß initial complex. In order to simultaneously fulfill these two actions, a human anti-IL-1ß neutralizing antibody IgG26 was screened from human genetic phage-display library and furthered structure-optimized to final version, IgG26AW. IgG26AW has a sub-nanomolar binding affinity for human IL-1ß. We validated IgG26AW-neutralizing antibodies specific for IL-1ß in vivo to prevent human IL-1ß-driving IL-6 elevation in C56BL/6 mice. Mice underwent treatments with IgG26AW in A549 and MDA-MB-231 xenograft mouse cancer models have also been observed with tumor shrank and inhibition of tumor metastasis. The region where IgG26 binds to IL-1ß also overlaps with the position where IL-1RI and IL-1RAcP bind, as revealed by the 26-Fab/IL-1ß complex structure. Meanwhile, SPR experiments showed that IL-1ß bound by IgG26AW prevented the further binding of IL-1RI and IL-1RAcP, which confirmed our inference from the result of protein structure. Therefore, the inhibitory mechanism of IgG26AW is to block the assembly of the IL-1ß/IL-1RI/IL-1RAcP ternary complex which further inhibits downstream signaling. Based on its high affinity, high neutralizing potency, and novel binding epitope simultaneously occupying both IL-1RI and IL-1RAcP residues that bind to IL-1ß, IgG26AW may be a new candidate for treatments of inflammation-related diseases or for complementary treatments of cancers in which the role of IL-1ß is critical to pathogenesis.

Endosomal TLR3 co-receptor CLEC18A enhances host immune response to viral infection.

Human C-type lectin member 18A (CLEC18A) is ubiquitously expressed in human, and highest expression levels are found in human myeloid cells and liver. In contrast, mouse CLEC18A (mCLEC18A) is only expressed in brain, kidney and heart. However, the biological functions of CLEC18A are still unclear. We have shown that a single amino acid change (S339 →R339) in CTLD domain has profound effect in their binding to polysaccharides and house dust mite allergens. In this study, we further demonstrate that CLEC18A and its mutant CLEC18A(S339R) associate with TLR3 in endosome and bind poly (I:C) specifically. Compared to TLR3 alone, binding affinity to poly (I:C) is further increased in TLR3-CLEC18A and TLR3-CLEC18A(S339R) complexes. Moreover, CLEC18A and CLEC18A(S339R) enhance the production of type I and type III interferons (IFNs), but not proinflammatory cytokines, in response to poly (I:C) or H5N1 influenza A virus (IAV) infection. Compared to wild type (WT) mice, ROSA-CLEC18A and ROSA-CLEC18A(S339R) mice generate higher amounts of interferons and are more resistant to H5N1 IAV infection. Thus, CLEC18A is a TLR3 co-receptor, and may contribute to the differential immune responses to poly (I:C) and IAV infection between human and mouse.

Eradicating mesothelin-positive human gastric and pancreatic tumors in xenograft models with optimized anti-mesothelin antibody-drug conjugates from synthetic antibody libraries.

Mesothelin (MSLN) is an attractive candidate of targeted therapy for several cancers, and hence there are increasing needs to develop MSLN-targeting strategies for cancer therapeutics. Antibody-drug conjugates (ADCs) targeting MSLN have been demonstrated to be a viable strategy in treating MSLN-positive cancers. However, developing antibodies as targeting modules in ADCs for toxic payload delivery to the tumor site but not to normal tissues is not a straightforward task with many potential hurdles. In this work, we established a high throughput engineering platform to develop and optimize anti-MSLN ADCs by characterizing more than 300 scFv CDR-variants and more than 50 IgG CDR-variants of a parent anti-MSLN antibody as candidates for ADCs. The results indicate that only a small portion of the complementarity determining region (CDR) residues are indispensable in the MSLN-specific targeting. Also, the enhancement of the hydrophilicity of the rest of the CDR residues could drastically increase the overall solubility of the optimized anti-MSLN antibodies, and thus substantially improve the efficacies of the ADCs in treating human gastric and pancreatic tumor xenograft models in mice. We demonstrated that the in vivo treatments with the optimized ADCs resulted in almost complete eradication of the xenograft tumors at the treatment endpoints, without detectable off-target toxicity because of the ADCs' high specificity targeting the cell surface tumor-associated MSLN. The technological platform can be applied to optimize the antibody sequences for more effective targeting modules of ADCs, even when the candidate antibodies are not necessarily feasible for the ADC development due to the antibodies' inferior solubility or affinity/specificity to the target antigen.

SIGLEC-3 (CD33) serves as an immune checkpoint receptor for HBV infection.

Chronic hepatitis B (CHB) infection is rarely eradicated by current antiviral nucleos(t)ide analogues. We found that α2,6-biantennary sialoglycans of HBV surface antigen (HBsAg) bound human SIGLEC-3 (CD33) by IP and ELISA, and the binding affinity between SIGLEC-3 and α2,6-biantennary sialoglycans was determined by biolayer interferometry (equilibrium dissociation constant [KD]: 1.95 × 10-10 ± 0.21 × 10-10 M). Moreover, HBV activated SIGLEC-3 on myeloid cells and induced immunosuppression by stimulating immunoreceptor tyrosine-based inhibitory motif phosphorylation and SHP-1/-2 recruitment via α2,6-biantennary sialoglycans on HBsAg. An antagonistic anti-SIGLEC-3 mAb reversed this effect and enhanced cytokine production in response to TLR-7 agonist GS-9620 in PBMCs from CHB patients. Moreover, anti-SIGLEC-3 mAb alone was able to upregulate the expression of molecules involved in antigen presentation, such as CD80, CD86, CD40, MHC-I, MHC-II, and PD-L1 in CD14+ cells. Furthermore, SIGLEC-3 SNP rs12459419 C, which expressed a higher amount of SIGLEC-3, was associated with increased risk of hepatocellular carcinoma (HCC) in CHB patients (HR: 1.256, 95% CI: 1.027-1.535, P = 0.0266). Thus, blockade of SIGLEC-3 is a promising strategy to reactivate host immunity to HBV and lower the incidence of HCC in the CHB patient population.