Humanized Mouse Model of HIV-1 Latency with Enrichment of Latent Virus in PD-1+ and TIGIT+ CD4 T Cells

Reprogramming human B cells with custom heavy-chain antibodies

The immunoglobulin locus of B cells can be reprogrammed by genome editing to produce custom or non-natural antibodies that are not induced by immunization. However, current strategies for antibody reprogramming require complex expression cassettes and do not allow for customization of the constant region of the antibody. Here we show that human B cells can be edited at the immunoglobulin heavy-chain locus to express heavy-chain-only antibodies that support alterations to both the fragment crystallizable domain and the antigen-binding domain, which can be based on both antibody and non-antibody components. Using the envelope protein (Env) from the human immunodeficiency virus as a model antigen, we show that B cells edited to express heavy-chain antibodies to Env support the regulated expression of B cell receptors and antibodies through alternative splicing and that the cells respond to the Env antigen in a tonsil organoid model of immunization. This strategy allows for the reprogramming of human B cells to retain the potential for in vivo amplification while producing molecules with flexibility of composition beyond that of standard antibodies.

Humanized mice for studying HIV latency and potentially its eradication

PURPOSE OF THE REVIEW

The quest for an HIV cure faces a formidable challenge: the persistent presence of latent viral infections within the cells and tissues of infected individuals. This review provides a thorough examination of discussions surrounding HIV latency, the use of humanized mouse models, and strategies aimed at eliminating the latent HIV reservoir. It explores the hurdles and advancements in understanding HIV pathogenesis, mainly focusing on establishing latent reservoirs in CD4 + T cells and macrophages. Introducing the concepts of functional and sterile cures, the review underscores the indispensable role of humanized mouse models in HIV research, offering crucial insights into the efficacy of cART and the ongoing pursuit of an HIV cure.

RECENT FINDINGS

Here, we highlight studies investigating molecular mechanisms and pathogenesis related to HIV latency in humanized mice and discuss novel strategies for eradicating latent HIV. Emphasizing the importance of analytical cART interruption in humanized mouse studies to gauge its impact on the latent reservoir accurately, the review underlines the ongoing progress and challenges in harnessing humanized mouse models for HIV research.

SUMMARY

This review suggests that humanized mice models provide valuable insights into HIV latency and potential eradication strategies, contributing significantly to the quest for an HIV cure.

Reprogramming human B cells with custom heavy chain antibodies

We describe a genome editing strategy to reprogram the immunoglobulin heavy chain (IgH) locus of human B cells to express custom molecules that respond to immunization. These heavy chain antibodies (HCAbs) comprise a custom antigen-recognition domain linked to an Fc domain derived from the IgH locus and can be differentially spliced to express either B cell receptor (BCR) or secreted antibody isoforms. The HCAb editing platform is highly flexible, supporting antigen-binding domains based on both antibody and non-antibody components, and also allowing alterations in the Fc domain. Using HIV Env protein as a model antigen, we show that B cells edited to express anti-Env HCAbs support the regulated expression of both BCRs and antibodies, and respond to Env antigen in a tonsil organoid model of immunization. In this way, human B cells can be reprogrammed to produce customized therapeutic molecules with the potential for in vivo amplification.

The Humanized Mouse Model: What Added Value Does It Offer for HIV Research?

In the early 2000s, novel humanized mouse models based on the transplantation of human hematopoietic stem and progenitor cells (HSPCs) into immunocompromised mice were introduced (hu mice). The human HSPCs gave rise to a lymphoid system of human origin. The HIV research community has greatly benefitted from these hu mice. Since human immunodeficiency virus (HIV) type 1 infection results in a high-titer disseminated HIV infection, hu mice have been of great value for all types of HIV research from pathogenesis to novel therapies. Since the first description of this new generation of hu mice, great efforts have been expended to improve humanization by creating other immunodeficient mouse models or supplementing mice with human transgenes to improve human engraftment. Many labs have their own customized hu mouse models, making comparisons quite difficult. Here, we discuss the different hu mouse models in the context of specific research questions in order to define which characteristics should be considered when determining which hu mouse model is appropriate for the question posed. We strongly believe that researchers must first define their research question and then determine whether a hu mouse model exists, allowing the research question to be studied.

An Efficient Humanized Mouse Model for Oral Anti-Retroviral Administration

HIV anti-retrovirals (ARVs) have vastly improved the life expectancy of people living with HIV (PLWH). However, toxic effects attributed to long-term ARV use also contribute to HIV-related co-morbidities such as heart disease, bone loss and HIV-associated neurocognitive disorders (HAND). Unfortunately, mouse models used to study the effects of ARVs on viral suppression, toxicity and HIV latency/tissue reservoirs have not been widely established. Here, we demonstrate an effective mouse model utilizing immune-compromised mice, reconstituted with infected human peripheral blood mononuclear cell (PBMCs). ARVs areincorporated into mouse chow and administered daily with combination ARV regimens includingAtripla (efavirenz, tenofovir disoproxil fumarate, and emtricitabine) and Triumeq (abacavir, dolutegravir and lamivudine). This model measures HIV-infected human cell trafficking, and ARV penetration throughout most relevant HIV organs and plasma, with a large amount of trafficking to the secondary lymphoid organs. Furthermore, the HIV viral load within each organ and the plasma was reduced in ARV treated vs. untreated control. Overall, we have demonstrated a mouse model that is relatively easy and affordable to establish and utilize to study ARVs' effect on various tissues, including the co-morbid conditions associated with PLWH, such as HAND, and other toxic effects.

Identification of CD98 as a Novel Biomarker for HIV-1 Permissiveness and Latent Infection

Human immunodeficiency virus type 1 (HIV-1) can integrate viral DNA into host cell chromosomes to establish a long-term stable latent reservoir, which is a major obstacle to cure HIV-1 infection. The characteristics of the HIV-1 latent reservoir have not been fully understood. Here, we identified 126 upregulated plasma membrane proteins in HIV-1 latently infected cells by a label-free liquid chromatography-tandem mass spectrometry analysis. The higher levels of CD98 expression in multiple HIV-1 latently infected cell lines and primary CD4+ T cells compared to uninfected cells were further confirmed by quantitative reverse transcription PCR (RT-qPCR) and flow cytometry analyses. In addition, CD98high CD4+ T cells displayed hyper-permissiveness to HIV-1 infection and possessed distinct immune phenotypic profiles associated with Th17 and peripheral follicular T helper (pTFH) characteristics. Notably, the CD98high resting memory CD4+ T cells harbored significantly higher cell-associated viral RNA and intact provirus than CD98low counterparts in HIV-1-infected individuals receiving combined antiretroviral therapy. Furthermore, CD98high CD4+ T cells exhibited a robust proliferative capacity and significantly contributed to the clonal expansion of the HIV-1 latent reservoir. Our study demonstrates that CD98 can be used as a novel biomarker of HIV-1 latently infected cells to indicate the effect of various strategies to reduce the viral reservoir. IMPORTANCE Identification of cellular biomarkers is the crucial challenge to eradicate the HIV-1 latent reservoir. In our study, we identified CD98 as a novel plasma membrane biomarker for HIV-1 permissiveness and latent infection. Importantly, CD98high CD4+ T cells exhibited a hyper-permissiveness to HIV-1 infection and significantly contributed to the clonal expansion of the HIV-1 latent reservoir. CD98 could be targeted to develop therapeutic strategies to reduce the HIV-1 latent reservoir in further research.

HIV-1 infected humanized DRAGA mice develop HIV-specific antibodies despite lack of canonical germinal centers in secondary lymphoid tissues

A major barrier in the use of humanized mice as models of HIV-1 (HIV) infection is the inadequate generation of virus-specific antibody responses. Humanized DRAGA (hDRAGA) mice generate antigen-specific class switched antibodies to several pathogens, but whether they do so in HIV infection and the extent to which their secondary lymphoid tissues (sLT) support germinal center responses is unknown. hDRAGA mice were evaluated for their ability to support HIV replication, generate virus-specific antibody responses, develop splenocyte subsets, and organize sLT architecture. hDRAGA mice supported persistent HIV replication and developed modest levels of gp41-specific human IgM and IgG. Spleens from uninfected and HIV infected hDRAGA mice contained differentiated B and CD4+ T cell subsets including germinal center (GC) B cells and T follicular helper cells (TFH); relative expansions of TFH and CD8+ T cells, but not GC B cells, occurred in HIV-infected hDRAGA mice compared to uninfected animals. Immunofluorescent staining of spleen and mesenteric lymph node sections demonstrated atypical morphology. Most CD4+ and CD8+ T cells resided within CD20hi areas. CD20hi areas lacked canonical germinal centers, as defined by staining for IgD-Ki67+cells. No human follicular dendritic cells (FDC) were detected. Mouse FDC were distributed broadly throughout both CD20hi and CD20lo regions of sLT. HIV RNA particles were detected by in situ hybridization within CD20+ areas and some co-localized with mouse FDC. Viral RNA+ cells were more concentrated within CD20hi compared to CD20lo areas of sLT, but differences were diminished in spleen and eliminated in mesenteric lymph nodes when adjusted for CD4+ cell frequency. Thus, hDRAGA mice recapitulated multiple aspects of HIV pathogenesis including HIV replication, relative expansions in TFH and CD8+ T cells, and modest HIV-specific antibody production. Nevertheless, classical germinal center morphology in sLT was not observed, which may account for the inefficient expansion of GC B cells and generation of low titer human antibody responses to HIV-1 in this model.

Three-dimensional models of the cervicovaginal epithelia to study host-microbiome interactions and sexually transmitted infections

2D cell culture systems have historically provided controlled, reproducible means to analyze host-pathogen interactions observed in the human reproductive tract. Although inexpensive, straightforward, and requiring a very short time commitment, these models recapitulate neither the functionality of multilayered cell types nor the associated microbiome that occurs in a human. Animal models have commonly been used to recreate the complexity of human infections. However, extensive modifications of animal models are required to recreate interactions that resemble those in the human reproductive tract. 3D cell culture models have emerged as alternative means of reproducing vital elements of human infections at a fraction of the cost of animal models and on a scale that allows for replicative experiments. Here, we describe a new 3D model that utilizes transwells with epithelial cells seeded apically and a basolateral extracellular matrix (ECM)-like layer. The model produced tissues with morphologic and physiological resemblance to human cervical and vaginal epithelia, including mucus levels produced by cervical cells. Infection by Chlamydia trachomatis and Neisseria gonorrhoeae was demonstrated, as well as the growth of bacterial species observed in the human vaginal microbiota. This enabled controlled mechanistic analyses of the interactions between host cells, the vaginal microbiota, and STI pathogens. Affordable and semi high-throughput 3D models of the cervicovaginal epithelia that are physiologically relevant by sustaining vaginal bacterial colonization, and facilitate studies of chlamydial and gonococcal infections.

Baseline and time-updated factors in preclinical development of anionic dendrimers as successful anti-HIV-1 vaginal microbicides

Although a wide variety of topical microbicides provide promising in vitro and in vivo efficacy, most of them failed to prevent sexual transmission of human immunodeficiency virus type 1 (HIV-1) in human clinical trials. In vitro, ex vivo, and in vivo models must be optimized, considering the knowledge acquired from unsuccessful and successful clinical trials to improve the current gaps and the preclinical development protocols. To date, dendrimers are the only nanotool that has advanced to human clinical trials as topical microbicides to prevent HIV-1 transmission. This fact demonstrates the importance and the potential of these molecules as microbicides. Polyanionic dendrimers are highly branched nanocompounds with potent activity against HIV-1 that disturb HIV-1 entry. Herein, the most significant advancements in topical microbicide development, trying to mimic the real-life conditions as closely as possible, are discussed. This review also provides the preclinical assays that anionic dendrimers have passed as microbicides because they can improve current antiviral treatments' efficacy. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Expression Profile and Biological Role of Immune Checkpoints in Disease Progression of HIV/SIV Infection

During HIV/SIV infection, the upregulation of immune checkpoint (IC) markers, programmed cell death protein-1 (PD-1), cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), T cell immunoglobulin and ITIM domain (TIGIT), lymphocyte-activation gene-3 (LAG-3), T cell immunoglobulin and mucin domain-3 (Tim-3), CD160, 2B4 (CD244), and V-domain Ig suppressor of T cell activation (VISTA), can lead to chronic T cell exhaustion. These ICs play predominant roles in regulating the progression of HIV/SIV infection by mediating T cell responses as well as enriching latent viral reservoirs. It has been demonstrated that enhanced expression of ICs on CD4⁺ and CD8⁺ T cells could inhibit cell proliferation and cytokine production. Overexpression of ICs on CD4⁺ T cells could also format and prolong HIV/SIV persistence. IC blockers have shown promising clinical results in HIV therapy, implying that targeting ICs may optimize antiretroviral therapy in the context of HIV suppression. Here, we systematically review the expression profile, biological regulation, and therapeutic efficacy of targeted immune checkpoints in HIV/SIV infection.

Inducing Long-Term HIV-1 Latency in the TKO-BLT Mouse Model

Multiple humanized mouse models have been produced for the study of HIV-1 infection and treatment. Humanized mice produced using the bone marrow, liver, thymus (BLT) method particularly have well-reconstituted and functional human immune systems, providing an excellent model for HIV-1 cure strategies that aim to harness the human immune system as part of the cure approach. The TKO-BLT humanized mouse model is especially useful for long-term studies as it is highly resistant to the wasting syndrome and graft-versus-host disease (GVHD ) that can limit the use of other BLT-models. Here we describe the methods used to induce latency in TKO-BLT mice, using both injectable and free-fed combination antiretroviral therapy (cART) regimens, for use in the study of HIV-1 latency and evaluation of HIV-1 cure interventions.

Transient HIV Reservoirs and Interleukin-6 Increase After Anti-Programmed Death-1 Antibody Infusion in HIV Patients with Lung Cancer

Background

The purpose of this study is to examine the dynamic effects of anti-programmed death (PD)-1 antibody treatment on HIV reservoirs and inflammatory cytokines in patients with HIV infections who were diagnosed with non-small cell lung cancer (NSCLC).

Methods

This is a clinical trial in which three HIV patients with NSCLC were administered 14 infusions of anti-PD-1 antibody at 21-day intervals. Blood samples were collected from the participants before each infusion (0 h), and at 2 h, 24 h, and 7 days after each infusion of anti-PD-1 monoclonal antibody. The levels of cell-associated HIV RNA (CA-HIV-RNA), HIV DNA, and inflammatory cytokines (including interferon [IFN]-α, IFN-γ, tumor necrosis factor [TNF]-α, interleukin [IL]-2, IL-4, IL-6, IL-10, and IL-17A) were assessed at each timepoint.

Results

A significant increase in CA-HIV-RNA (P = 0.049) and HIV DNA (P = 0.042) was observed 24 h after each infusion of anti-PD-1 monoclonal antibody. The Z-score for IL-6 increased from −0.46 ± 0.53 to 0.28 ± 0.78 at 24 h after infusion (P = 0.02), and further increased to 0.61 ± 1.0 at 7 days after each infusion (P = 0.007). A significant correlation was observed between IL-6 and HIV DNA (P = 0.02).

Conclusion

The CA-HIV-RNA, HIV DNA, and IL-6 levels significantly increased after infusion of anti-PD-1 monoclonal antibody in the three HIV-infected patients with NSCLC. These results support an early transient effect of anti-PD-1 monoclonal antibody infusion on HIV reservoirs. However, the long-term effect needs to be investigated in a larger cohort with a longer follow-up period.

Knockdown of Astrocytic Monocarboxylate Transporter 4 in the Motor Cortex Leads to Loss of Dendritic Spines and a Deficit in Motor Learning

Monocarboxylate transporters (MCTs) shuttle molecules, including L-lactate, involved in metabolism and cell signaling of the central nervous system. Astrocyte-specific MCT4 is a key component of the astrocyte-neuron lactate shuttle (ANLS) and is important for neuroplasticity and learning of the hippocampus. However, the importance of astrocyte-specific MCT4 in neuroplasticity of the M1 primary motor cortex remains unknown. In this study, we investigated astrocyte-specific MCT4 in motor learning and neuroplasticity of the M1 primary motor cortex using a cell-type specific shRNA knockdown of MCT4. Knockdown of astrocyte-specific MCT4 resulted in impaired motor performance and learning on the accelerating rotarod. In addition, MCT4 knockdown was associated with a reduction of neuronal dendritic spine density and spine width and decreased protein expression of PSD95, Arc, and cFos. Using near-infrared-conjugated 2-deoxyglucose uptake as a surrogate marker for neuronal activity, MCT4 knockdown was also associated with decreased neuronal activity in the M1 primary motor cortex and associated motor regions including the dorsal striatum and ventral thalamus. Our study supports a potential role for astrocyte-specific MCT4 and the ANLS in the neuroplasticity of the M1 primary motor cortex. Targeting MCT4 may serve to enhance neuroplasticity and motor repair in several neurological disorders, including Parkinson's disease and stroke.

Humanized Mice for Infectious and Neurodegenerative disorders

Humanized mice model human disease and as such are used commonly for research studies of infectious, degenerative and cancer disorders. Recent models also reflect hematopoiesis, natural immunity, neurobiology, and molecular pathways that influence disease pathobiology. A spectrum of immunodeficient mouse strains permit long-lived human progenitor cell engraftments. The presence of both innate and adaptive immunity enables high levels of human hematolymphoid reconstitution with cell susceptibility to a broad range of microbial infections. These mice also facilitate investigations of human pathobiology, natural disease processes and therapeutic efficacy in a broad spectrum of human disorders. However, a bridge between humans and mice requires a complete understanding of pathogen dose, co-morbidities, disease progression, environment, and genetics which can be mirrored in these mice. These must be considered for understanding of microbial susceptibility, prevention, and disease progression. With known common limitations for access to human tissues, evaluation of metabolic and physiological changes and limitations in large animal numbers, studies in mice prove important in planning human clinical trials. To these ends, this review serves to outline how humanized mice can be used in viral and pharmacologic research emphasizing both current and future studies of viral and neurodegenerative diseases. In all, humanized mouse provides cost-effective, high throughput studies of infection or degeneration in natural pathogen host cells, and the ability to test transmission and eradication of disease.

Perspectives on Non-BLT Humanized Mouse Models for Studying HIV Pathogenesis and Therapy

A variety of humanized mice, which are reconstituted only with human hematopoietic stem cells (HSC) or with fetal thymus and HSCs, have been developed and widely utilized as in vivo animal models of HIV-1 infection. The models represent some aspects of HIV-mediated pathogenesis in humans and are useful for the evaluation of therapeutic regimens. However, there are several limitations in these models, including their incomplete immune responses and poor distribution of human cells to the secondary lymphoid tissues. These limitations are common in many humanized mouse models and are critical issues that need to be addressed. As distinct defects exist in each model, we need to be cautious about the experimental design and interpretation of the outcomes obtained using humanized mice. Considering this point, we mainly characterize the current conventional humanized mouse reconstituted only with HSCs and describe past achievements in this area, as well as the potential contributions of the humanized mouse models for the study of HIV pathogenesis and therapy. We also discuss the use of various technologies to solve the current problems. Humanized mice will contribute not only to the pre-clinical evaluation of anti-HIV regimens, but also to a deeper understanding of basic aspects of HIV biology.

Humanized Mice for the Evaluation of Novel HIV-1 Therapies

With the discovery of antiretroviral therapy, HIV-1 infection has transitioned into a manageable but chronic illness, which requires lifelong treatment. Nevertheless, complete eradication of the virus has still eluded us. This is partly due to the virus’s ability to remain in a dormant state in tissue reservoirs, ‘hidden’ from the host’s immune system. Also, the high mutation rate of HIV-1 results in escape mutations in response to many therapeutics. Regardless, the development of novel cures for HIV-1 continues to move forward with a range of approaches from immunotherapy to gene editing. However, to evaluate in vivo pathogenesis and the efficacy and safety of therapeutic approaches, a suitable animal model is necessary. To this end, the humanized mouse was developed by McCune in 1988 and has continued to be improved on over the past 30 years. Here, we review the variety of humanized mouse models that have been utilized through the years and describe their specific contribution in translating HIV-1 cure strategies to the clinic.

CD32+CD4+ memory T cells are enriched for total HIV-1 DNA in tissues from humanized mice

CD32 has raised conflicting results as a putative marker of the HIV-1 reservoir. We measured CD32 expression in tissues from viremic and virally suppressed humanized mice treated relatively early or late after HIV-1 infection with combined antiretroviral therapy. CD32 was expressed in a small fraction of the memory CD4+ T-cell subsets from different tissues in viremic and aviremic mice, regardless of treatment initiation time. CD32+ memory CD4+ T cells were enriched in cell-associated (CA) HIV-1 DNA but not in CA HIV-1 RNA as compared to the CD32-CD4+ fraction. Using multidimensional reduction analysis, several memory CD4+CD32+ T-cell clusters were identified expressing HLA-DR, TIGIT, or PD-1. Importantly, although tissue-resident CD32+CD4+ memory cells were enriched with translation-competent reservoirs, most of it was detected in memory CD32-CD4+ T cells. Our findings support that CD32 labels highly activated/exhausted memory CD4+ T-cell subsets that contain only a small proportion of the translation-competent reservoir.

Tracking HIV Rebound following Latency Reversal Using Barcoded HIV

HIV latency prevents cure of infection with antiretroviral therapy (ART) alone. One strategy for eliminating latently infected cells involves the induction of viral protein expression via latency-reversing agents (LRAs), allowing killing of host cells by viral cytopathic effects or immune effector mechanisms. Here, we combine a barcoded HIV approach and a humanized mouse model to study the effects of a designed, synthetic protein kinase C modulating LRA on HIV rebound. We show that administration of this compound during ART results in a delay in rebound once ART is stopped. Furthermore, the rebounding virus appears composed of a smaller number of unique barcoded viruses than occurs in control-treated animals, suggesting that some reservoir cells that would have contributed virus to the rebound process are eliminated by LRA administration. These data support the use of barcoded virus to study rebound and suggest that LRAs may be useful in HIV cure efforts.

Immune Checkpoints in Viral Infections

As evidence has mounted that virus-infected cells, such as cancer cells, negatively regulate the function of T-cells via immune checkpoints, it has become increasingly clear that viral infections similarly exploit immune checkpoints as an immune system escape mechanism. Although immune checkpoint therapy has been successfully used in cancer treatment, numerous studies have suggested that such therapy may also be highly relevant for treating viral infection, especially chronic viral infections. However, it has not yet been applied in this manner. Here, we reviewed recent findings regarding immune checkpoints in viral infections, including COVID-19, and discussed the role of immune checkpoints in different viral infections, as well as the potential for applying immune checkpoint blockades as antiviral therapy.

TIGIT is upregulated by HIV-1 infection and marks a highly functional adaptive and mature subset of natural killer cells

OBJECTIVE

Our objective was to investigate the mechanisms that govern natural killer (NK)-cell responses to HIV, with a focus on specific receptor--ligand interactions involved in HIV recognition by NK cells.

DESIGN AND METHODS

We first performed a mass cytometry-based screen of NK-cell receptor expression patterns in healthy controls and HIV individuals. We then focused mechanistic studies on the expression and function of T cell immunoreceptor with Ig and ITIM domains (TIGIT).

RESULTS

The mass cytometry screen revealed that TIGIT is upregulated on NK cells of untreated HIV women, but not in antiretroviral-treated women. TIGIT is an inhibitory receptor that is thought to mark exhausted NK cells; however, blocking TIGIT did not improve anti-HIV NK-cell responses. In fact, the TIGIT ligands CD112 and CD155 were not upregulated on CD4 T cells in vitro or in vivo, providing an explanation for the lack of benefit from TIGIT blockade. TIGIT expression marked a unique subset of NK cells that express significantly higher levels of NK-cell-activating receptors (DNAM-1, NTB-A, 2B4, CD2) and exhibit a mature/adaptive phenotype (CD57, NKG2C, LILRB1, FcRγ, Syk). Furthermore, TIGIT NK cells had increased responses to mock-infected and HIV-infected autologous CD4 T cells, and to PMA/ionomycin, cytokine stimulation and the K562 cancer cell line.

CONCLUSION

TIGIT expression is increased on NK cells from untreated HIV individuals. Although TIGIT does not participate directly to the response to HIV-infected cells, it marks a population of mature/adaptive NK cells with increased functional responses.