Biology subjects

Cheng, H.-L.

Publications and source records attributed to Cheng, H.-L..

4 recordsLinked to original sources

bioRxiv2026

Mouse models with human antibody repertoires for inducing multiple lineages of HIV-1 broadly neutralizing antibodies

The complementarity determining region (CDR) 1, 2 and 3 of antibodies are the principal antigen contact sites. The heavy chain CDR3 (CDR H3) is highly variable, because it includes random nucleotide additions by the terminal deoxynucleotidyl transferase (TdT). Some broadly neutralizing antibodies (bnAbs) against the human immunodeficiency virus-1 (HIV-1) rely heavily on CDR H3 to recognize conserved epitopes on HIV-1 Envelope (Env) protein. Elicitation of comparable bnAbs is a prime goal of HIV-1 vaccine development, but the shortage of precursor antibodies with suitable CDR H3s in human repertoire is a major challenge for immunogen design. To aid this effort, we generated six mouse models for inducing bnAbs against major HIV-1 Env epitopes. In each mouse model, the immunoglobulin heavy and light chain loci were engineered to predominantly rearrange the germline V, D and J segments of a bnAb lineage. Owing to CDR3 diversity, only a small subset of the V(D)J recombination products may encode variable regions that can engage bnAb epitopes with sufficient affinity to initiate immune response. Therefore, these mouse models can be used to test and optimize immunization strategies to induce bnAbs from rare and diverse precursors in complex antibody repertoires.

immunology↗

bioRxiv2026

Maturation of HIV-1 neutralizing antibodies in a germinal center conditional expression mouse model

In germinal centers, activated B cells modify their antigen receptors through somatic hypermutation (SHM), followed by antigenic selection that favors expansion of high affinity B cells. The affinity maturation process is critical for development of broadly neutralizing antibodies (bnAbs) against the human immunodeficiency virus-1 (HIV-1). BnAbs have been isolated from some people living with HIV-1. Because these antibodies target conserved epitopes of the HIV-1 Envelope (Env) protein, they inhibit a broad spectrum of viruses. Eliciting bnAbs by vaccination is a top priority for HIV-1 prevention, but reproducing the lengthy maturation of bnAbs is a major challenge. The problem is typified by VRC01 class antibodies, which recognize the CD4 binding site of HIV-1 Env protein. To reach the CD4 binding site, antibodies need to navigate through adjacent glycans. Accommodating the glycans requires multiple SHMs in germinal center (GC) B cells, including infrequent events. For this reason, VRC01 vaccine development often stalls at this point. We have generated a mouse model aimed at providing a potential solution for navigating this vaccine design impediment. To this end, we made a mouse model that expresses a stalled VRC01 intermediate conditionally in GC B cells. This system has three advantages: 1) direct expression of the intermediate obviates prior immunization steps, thereby shortening the immunization scheme; 2) the conditional expression system bypasses tolerance control checkpoints that sometimes delete B cells expressing bnAbs; 3) the intermediate responds to immunization in GCs, the physiological site of affinity maturation. With this model, we established an immunization method to mature the VRC01 intermediate into heterologous neutralizing antibodies against viruses with a native glycan shield. Since high mutation load is common among bnAbs, the germinal center conditional expression system could provide a general tool for boost immunogen design to overcome roadblocks in the maturation pathway. Author summaryIn response to antigenic stimulation, cognate B cells become activated and form germinal centers in lymphoid tissues. Germinal center B cells modify their antigen receptors through somatic hypermutation (SHM) of immunoglobulin variable region gene exons, with antigen selecting for high affinity B cells by providing survival advantage. This mechanism accounts for antibody affinity maturaton over the gradual course of an immune response. Affinity maturation is critical for generating potent, neutralizing antibodies against diverse strains of the human immunodeficiency virus-1 (HIV-1). These broadly neutralizing antibodies (bnAbs) are heavily mutated, reflecting lengthy affinity maturation over years of chronic infection. Recapitulating the affinity maturation process is a major challenge for bnAb induction by vaccination. In immunization experiments, bnAb development often stalls at rate limiting steps that involve infrequent, but functionally important, mutational events. Overcoming such obstacles requires boost immunogens that can stimulate the stalled B cells to acquire the requisite mutations. To this end, we recapitulated the maturation arrest of a bnAb lineage by expressing a stalled antibody in mouse germinal center B cells. Using this mouse model, we developed boost immunization conditions that advanced the antibody maturation beyond a roadblock to attain neutralizing activities against heterogenous viruses.

immunology↗

bioRxiv2020

An In Vivo Method for Diversifying the Functions of Therapeutic Antibodies

V(D)J recombination generates mature B cells that express huge repertoires of primary antibodies as diverse immunoglobulin heavy (IgH) and light chains (IgL) of their B cell antigen receptors (BCRs). Cognate antigen binding to BCR variable region domains activates B cells into the germinal center (GC) reaction in which somatic hypermutation (SHM) modifies primary variable region-encoding sequences, with subsequent selection for mutations that improve antigen-binding affinity, ultimately leading to antibody affinity maturation. Based on these principles, we developed a humanized mouse model approach to diversify an anti-PD1 therapeutic antibody and allow isolation of variants with novel properties. In this approach, component Ig gene segments of the anti-PD1 antibody underwent de novo V(D)J recombination to diversify the anti-PD1 antibody in the primary antibody repertoire in the mouse models. Immunization of these mouse models further modifies the anti-PD1 antibodies through SHM. Known anti-PD1 antibodies block interaction of PD1 with its ligands to alleviate PD1-mediated T cell suppression, thereby boosting anti-tumor T cell responses. By diversifying one such anti-PD1 antibody, we derived many new anti-PD1 antibodies, including anti-PD1 antibodies with the opposite activity of enhancing PD1/ligand interaction. Such antibodies theoretically might suppress deleterious T cell activities in autoimmune diseases. The approach we describe should be generally applicable for diversifying other therapeutic antibodies. Significance StatementThe immune system is capable of producing enormous varieties of antibodies to counter pathogenic infections. In this study, we devised a method to harness the power of the immune system to produce potentially therapeutic antibodies. As a test, we used this method to generate antibodies against the human PD1 molecule, a negative regulator of T cell activity. Available anti-PD1 therapeutic antibodies inhibit the function of PD1, thereby boosting T cell activity against tumor cells. Through our approach, we diversified one such anti-PD1 antibody in our mouse models. From this work, we obtained multiple new anti-PD1 antibodies, some of which can stimulate, rather than inhibit, PD1 function in vitro. Such PD1 stimulatory antibodies could potentially be used to suppress pathogenic T cell activities in autoimmune diseases. This method could be used to diversify the functions of other therapeutic antibodies.

immunology↗

bioRxiv2020

Conditional Antibody Expression to Avoid Central B Cell Deletion in a Humanized HIV-1 Vaccine Mouse Models

HIV-1 vaccine development aims to elicit broadly neutralizing antibodies (bnAbs) against diverse viral strains. In some HIV-1 infected individuals, bnAbs evolve from precursor antibodies through affinity maturation. To induce bnAbs, a vaccine must mediate a similar process of antibody maturation. One way to test vaccination strategies is to immunize mouse models that express human bnAb precursors. Such immunization experiments can assess whether the vaccine can convert precursor antibody into bnAb. A major problem with such mouse models is that bnAb expression often hinders B cell development in the bone marrow. Such developmental blocks may be attributed to unusual properties of bnAb variable regions, such as poly-reactivity and long antigen-binding loops, which are often under negative selection during primary B cell development. To address this problem, we devised a method to circumvent B cell developmental block by expressing bnAbs conditionally in mature B cells. We validated this method by expressing the unmutated common ancestor (UCA) of the human VRC26 bnAb in transgenic mice. Constitutive expression of combined immunoglobulin heavy and light chains of VRC26UCA led to developmental arrest of B cell progenitors in the bone marrow; poly-reactivity of VRC26UCA and poor pairing of VRC26UCA IgH chain with mouse surrogate light chain may contribute to the phenotype. The conditional expression strategy circumvented this developmental impediment, allowing the VRC26UCA to be expressed in mature peripheral B cells. This method should be generally applicable for expressing other antibodies that are under negative selection during B cell development. Significance statementMouse models can provide fast and cost-effective systems to test HIV-1 vaccine candidates at the pre-clinical stage. To serve this purpose, mouse models are engineered to express the precursors of human bnAbs against diverse HIV-1 strains. Immunization of such mouse models can evaluate the ability of vaccines to mature the precursor antibodies into bnAbs. However, due to unusual properties of bnAbs, mouse models expressing their precursors often have B cell developmental defects. In this study, we devised and validated a strategy to address this problem. This method could also facilitate the expression of other clinically relevant antibodies in mature B cells in transgenic mice; immunization of such mice could be used to generate novel antibodies with desirable properties.

immunology↗