Amelia Escolano, Ph.D.

An efficacious antibody-based vaccine against HIV-1 should elicit broadly neutralizing antibodies (bNAbs) targeting conserved epitopes of its envelope (Env) protein. Our previous work showed that common vaccination strategies using repeated boost immunization with the same Env immunogen could not elicit bNAbs. Instead, a new form of vaccination involving sequential immunization was required to elicit highly mutated anti-HIV-1 bNAbs. The reported sequential immunization protocol involved prime immunization with an engineered Env immunogen followed by a series of four additional immunizations with Env immunogens that gradually resembled the native-looking Env. This immunization protocol elicited bNAbs in an immunoglobulin knock-in mouse model with a monoclonal B cell repertoire engineered to carry the inferred germline precursor of a human bNAb (Escolano et al, Cell, 2016). These immunization experiments were the first showing that anti-HIV-1 bNAbs can be elicited by vaccination, and fueled subsequent vaccine design studies. However, despite this significant achievement, no vaccination protocols have been reported that are able to elicit protective levels of bNAbs in wild type organisms with a polyclonal B cell repertoire. 

Wild type organisms mount polyclonal antibody responses when encountering complex antigens such as the HIV-1 Env protein. A predominant component of antibody responses elicited by Env immunogens are antibodies to non-conserved or strain-specific epitopes of Env, with no potential to broadly neutralize HIV-1. These antibodies significantly interfere with the development of bNAbs.
 
The Escolano lab investigates the humoral and cellular immune responses to sequential immunization to establish guidelines for vaccine design. We design and evaluate immunogens and sequential immunization strategies to elicit anti HIV-1 broadly neutralizing antibodies in wild type organisms. Our specific goal is to devise approaches to modulate the immunodominance properties of vaccine candidates aiming to focus the antibody responses to the conserved, neutralization-sensitive epitopes of Env.

Using state-of-the-art technologies for single cell analysis and different animal models including wild type mice, rhesus macaques and a series of recently generated immunoglobulin knock-in and reporter mice, we investigate the process of antibody maturation and the evolution of the different immune compartments upon sequential immunization.
 

Our laboratory has vast experience designing strategies to isolate antigen-specific B cells from wild type mice, humanized mice and non-human primates, and cloning their antibody genes. 

Antibody cloning from single B cells is an essential tool for characterizing humoral immune responses and obtaining valuable therapeutic and analytical reagents. Antibody cloning from individuals with high serologic titers to HIV-1, influenza, malaria, ZIKV, and SARS-CoV-2 has led to new insights that inform vaccine design efforts. 

We have designed cost-effective protocols to identify and purify single antigen-specific B cells, and subsequently clone and produce monoclonal antibodies. 

We are using the newly developed methods to isolate and characterize HIV-1-specific B cells from naïve and immunized mice, from vaccinated or simian-human immunodeficiency virus (SHIV)-infected rhesus macaques and from humans. Remarkably, using our approach, we have isolated one of the first anti-HIV-1 bNAbs from a SHIV-infected rhesus macaque, validating the use of macaques as preclinical models for HIV-1 vaccination studies. 

The Escolano laboratory uses this state-of-the-art methodology to isolate antibodies against bacteria, tumor neoantigens and viruses, including cancer-associated viruses. Characterization of the isolated antibodies is providing very valuable information to guide vaccine design efforts and the development of new preventative and therapeutic approaches. 

The use of animal models in biomedical research has been crucial to investigate the mechanisms of human pathophysiology, evaluate candidate interventions and predict treatment outcomes in humans. Animal Models have been extensively used by the scientific community to examine the cellular and humoral responses to infection and vaccination. Unfortunately, none of these models faithfully recapitulates the setting of a human immune response. 

Humanized mice genetically engineered to recapitulate different aspects of the human humoral and/or cellular immune response are highly desirable. In particular, human immunoglobulin knock-in mice (Ig KI mice) are remarkably valuable for vaccine development and drug discovery, as well as for basic immunology studies related to the analysis of B and T cell responses to infection, vaccination, autoimmunity, or cancer. However, current methods to produce Ig KI mice are inefficient, labor-intensive and require special equipment and expertise to perform zygote microinjections. 

We have developed a novel technology to efficiently and more easily generate monoclonal Ig KI mice using CRISPR/Cas9. The new technology remarkably simplifies the mouse production process, increases knock-in efficiency and reduces breeding time, thus accelerating the production process and reducing cost. 

We are currently using the new technology for high-throughput production of Ig KI mice carrying anti-HIV-1 antibodies, which we use for vaccine design purposes. 

Interestingly, this methodology can be adapted to introduce other genetic modifications in the mouse genome including gene insertions and deletions, thus being of great value to other scientific disciplines. The new technology is especially valuable for engineering events involving insertions of long DNA fragments or genetic modification of more than one locus.