Biology subjects

Menis, S.

Publications and source records attributed to Menis, S..

6 recordsLinked to original sources

bioRxiv2025

Vaccination with mRNA-encoded membrane-bound HIV Envelope trimer induces neutralizing antibodies in animal models

A protective vaccine against HIV will likely need to induce broadly neutralizing antibodies (bnAbs) that engage relatively conserved epitopes on the HIV envelope glycoprotein (Env) trimer. Nearly all vaccine strategies to induce bnAbs require the use of relatively complex immunization regimens involving a series of different immunogens, most of which are Env trimers. Producing protein-based clinical material to evaluate such relatively complex regimens in humans presents major challenges in cost and time. Furthermore, immunization with HIV trimers as soluble proteins induces strong non-neutralizing responses to the trimer base, which is normally occluded on the virion. These base responses could potentially detract from the induction of nAbs and the eventual induction of bnAbs. mRNA vaccine platforms offer potential advantages over protein delivery for HIV vaccine development, including increased production speed, reduced cost, and the ability to deliver membrane-bound trimers that might facilitate improved immuno-focusing to non-base epitopes. We report the design of mRNA-delivered soluble and membrane-bound forms of a stabilized native-like Env trimer (BG505 MD39.3), initial immunogenicity evaluation in rabbits that triggered clinical evaluation, and more comprehensive evaluation of B cell, T cell, and antibody responses in non-human primates. mRNA-encoded membrane-bound Env immunization elicited reduced off-target base-directed Env responses and stronger neutralizing antibody responses, compared with mRNA-encoded soluble Env. Overall, mRNA delivery of membrane-bound Env appears promising for enhancing B cell responses to subdominant epitopes and facilitating rapid translation to clinical testing, which should assist HIV vaccine development. One Sentence SummaryHIV envelope trimer mRNA enables membrane-bound expression and represents a functional immunogen in pre-clinical mammalian models.

immunology↗

bioRxiv2024

Diverse competitor B cell responses to a germline-targeting priming immunogen in human Ig loci transgenic mice

Broadly neutralizing antibodies (bnAbs) have promise to protect against HIV infection, but induction of bnAbs by immunization is an unsolved vaccine design challenge. Germline-targeting priming immunogens aim to initiate the induction of bnAbs by specifically activating rare bnAb-precursor B cells that can subsequently be matured using suitable heterologous boosting and shepherding immunogens. Several pre-clinical studies, and the IAVI G001 human clinical trial, have demonstrated the ability of a germline-targeting priming immunogen, eOD-GT8 60mer, to induce precursors of the VRC01 class of bnAbs. However, much less is known about B cells induced against other epitopes of the immunogen. Here, we performed unbiased analysis of B cells induced by eOD-GT8 60mers in Intelliselect Transgenic mice (Kymice) that are transgenic for the human Ig loci and produce human-like BCRs. B cells isolated with intact eOD-GT8 60mer nanoparticles showed a large diversity of non-VRC01-class B cells, with 38% unique clonotypes and only 5% of BCRs belonging to public lineages shared among all animals. We found that many competitors recognize epitopes in close proximity to or overlapping with the VRC01 epitope. These results indicate that optimal boosting of VRC01-class bnAb-precursor B cells primed by eOD-GT8 60mer might require a first-boost immunogen that minimizes recognition of competitor B cells, and such competitors isolated from Kymice could serve as valuable reagents for boost development.

immunology↗

bioRxiv2022

Use of Transient Transfection for cGMP Manufacturing of eOD-GT8 60mer, a Self-Assembling Nanoparticle Germline-Targeting HIV-1 Vaccine Candidate

We describe the current Good Manufacturing Practice (cGMP) production and subsequent characterization of eOD-GT8 60mer, a glycosylated self-assembling nanoparticle HIV-1 vaccine candidate germline-targeting priming immunogen. Production was carried out by transient expression in the human embryonic kidney 293 (HEK293) cell line followed by a combination of purification techniques. A large scale cGMP (200 L) production run yielded 354 mg of the purified eOD-GT8 60mer drug product material, which was formulated at 1 mg/mL in 10% sucrose in phosphate-buffered saline (PBS) at pH 7.2. The clinical trial material was comprehensively characterized for purity, antigenicity, glycan composition, amino acid sequence, aggregation, and by several safety-related tests during cGMP lot release. A comparison of purified products produced at 1 L scale and 200 L cGMP scale demonstrated consistency and robustness of the transient transfection upstream process and the downstream purification strategies. The cGMP clinical trial material is being tested in a phase 1 clinical trial (NCT03547245) and is currently stored at -80{degrees}C and on a stability testing program as per regulatory guidelines. The methods described here illustrate the utility of transient transfection for cGMP production of complex products such as glycosylated self-assembling nanoparticles.

biochemistry↗

bioRxiv2020

B cells expressing authentic naive human VRC01-class BCRs can be primed and recruited to germinal centers in multiple independent mouse models

Animal models of human antigen-specific B cell receptors (BCR) generally depend on "inferred germline" sequences, and thus their relationship to authentic naive human B cell BCR sequences and affinities is unclear. Here, BCR sequences from authentic naive human VRC01-class B cells from healthy human donors were selected for the generation of three new BCR knock-in mice. The BCRs span the physiological range of affinities found in humans, and use three different light chains (VK3-20, VK1-5, and VK1-33) found among subclasses of naive human VRC01-class B cells and HIV broadly neutralizing antibodies (bnAbs). The germline-targeting HIV immunogen eOD-GT8 60mer is currently in clinical trial as a candidate bnAb vaccine priming immunogen. To attempt to model human immune responses to the eOD-GT8 60mer, we tested each authentic naive human VRC01-class BCR mouse model under rare human physiological B cell precursor frequency conditions. B cells with high (HuGL18HL) or medium (HuGL17HL) affinity BCRs were primed, recruited to germinal centers, accrued substantial somatic hypermutation, and formed memory B cells. Precursor frequency and affinity interdependently influenced responses. Taken together, these experiments utilizing authentic naive human VRC01-class BCRs validate a central tenet of germline-targeting vaccine design and extend the overall concept of the reverse vaccinology approach to vaccine development.

immunology↗

bioRxiv2020

Targeting HIV Env immunogens to B cell follicles in non-human primates through immune complex or protein nanoparticle formulations

Following immunization, high affinity antibody responses develop within germinal centers (GCs), specialized sites within follicles of the lymph node (LN) where B cells proliferate and undergo somatic hypermutation. Antigen availability within GCs is important, as B cells must acquire and present antigen to follicular helper T cells to drive this process. However, recombinant protein immunogens such as soluble HIV envelope (Env) trimers do not efficiently accumulate in follicles following traditional immunization. Here we demonstrate two strategies to concentrate HIV Env immunogens in follicles, via the formation of immune complexes (ICs) or by employing self-assembling protein nanoparticles for multivalent display of Env antigens. Using rhesus macaques, we show that within a few days following immunization, free trimers were present in a diffuse pattern in draining LNs, while trimer ICs and Env nanoparticles accumulated in B cell follicles. Whole LN imaging strikingly revealed that ICs and trimer nanoparticles concentrated in as many as 500 follicles in a single lymph node within 2 days after immunization. Imaging of LNs collected 7 days post-immunization showed that Env nanoparticles persisted on follicular dendritic cells in the light zone of nascent germinal centers. These findings suggest that the form of antigen administered in vaccination can dramatically impact localization in lymphoid tissues and provides a new rationale for the enhanced immune responses observed following immunization with immune complexes or nanoparticles.

immunology↗

bioRxiv2018

Slow delivery immunization enhances HIV neutralizing antibody and germinal center responses via modulation of immunodominance

The observation that humans can produce broadly neutralizing antibodies (bnAbs) against HIV-1 has generated enthusiasm about the potential for a bnAb vaccine against HIV-1. Conventional immunization strategies will likely be insufficient for the development of a bnAb HIV vaccine and vaccines to other difficult pathogens, due to the significant immunological hurdles posed, including B cell immunodominance and germinal center (GC) quantity and quality. Using longitudinal lymph node fine needle aspirates, we found that two independent methods of slow delivery immunization of rhesus macaques (RM) resulted in larger GCs, more robust and sustained GC Tfh cell responses, and GC B cells with improved Env-binding, which correlated with the development of ~20 to 30-fold higher titers of tier 2 HIV-1 nAbs. Using a new RM genomic immunoglobulin loci reference sequence, we identified differential IgV gene usage between slow delivery immunized and conventional bolus immunized animals. The most immunodominant IgV gene used by conventionally immunized animals was associated with many GC B cell lineages. Ab mapping of those GC B cell specificities demonstrated targeting of an immunodominant non-neutralizing trimer base epitope, while that response was muted in slow delivery immunized animals. Thus, alternative immunization strategies appear to enhance nAb development by altering GCs and modulating immunodominance of non-neutralizing epitopes.

immunology↗