Chemoattractant-mediated leukocyte trafficking enables HIV dissemination from the genital mucosa

Humanized Mouse Models for Immuno-oncology Drug Discovery

Breakthroughs in cancer treatment with immunotherapeutics have provided long-term patient benefits for many different types of cancer. However, complete response is not achieved in many patients and tumor types, and the mechanisms underlying this lack of response are poorly understood. Despite this, numerous new targets, therapeutics, and drug combinations are being developed and tested in clinical trials. Preclinical models that recapitulate the complex human tumor microenvironment and the interplay between tumor and immune cells within the cancer-immunity cycle are needed to improve our understanding and screen new therapeutics for efficacy and safety/toxicity. Humanized mice, encompassing human tumors and human immune cells engrafted on immunodeficient mice, have been widely used for many years in immuno-oncology, with developments to improve both the humanization and the translational value central to the next generation of models. In this overview, we discuss recent advances in humanized models relevant to immuno-oncology drug discovery, the advantages and limitations of such models, the application of humanized models for efficacy and safety assessments of immunotherapeutics, and the potential opportunities. © 2023 Crown Bioscience. Current Protocols published by Wiley Periodicals LLC.

Cholesterol-conjugated siRNAs silence gene expression in mucosal dendritic cells in cervicovaginal tissue in mice

BACKGROUND

RNA interference (RNAi) provides a powerful way to investigate the role of genes in disease pathogenesis and modulate gene expression to treat disease. In 2018, the FDA approved patisiran, the first RNAi-based drug, hence paving the way for a novel class of RNAi therapeutics. Harnessing RNAi to inhibit vaginal HIV transmission requires effective gene silencing in immune cells, which remains difficult. Knockdown in accessible mucosal tissues may be easier than systemic gene silencing. Vaginally applied cholesterol-conjugated small interfering RNAs (chol-siRNAs) blocked herpes simplex virus transmission in mice without tissue damage or immunostimulation.

OBJECTIVES AND METHODS

To investigate using flow cytometry, confocal microscopy, and quantitative imaging if chol-siRNAs silence gene expression in vaginal immune cells in mice.

RESULTS

Although chol-siRNAs and lipoplexed-siRNAs silence gene expression in dendritic cells (DCs) in vitro, most internalized siRNAs concentrate within multivesicular bodies, where they are inaccessible to the cellular RNAi machinery. When applied intravaginally in vivo, chol-siRNAs penetrate the vaginal mucosa, including the lamina propria, and are efficiently internalized by intraepithelial (IE) and lamina propria (LP) DCs, and CD11b⁺ CD45⁺ cells, but not by T cells. Chol-siRNAs induce partial gene silencing in IE and LP DCs throughout the genital mucosa in vivo but are inactive in F4/80⁺ CD11b⁺ macrophages and T cells.

CONCLUSION

As mucosal DCs play an essential role for mucosal viral entry and dissemination, chol-siRNAs could be harnessed to target various host factors that are critical for viral uptake, DC migration and trans-infection of virions to T cells, hence allowing the development of a preventive vaginal HIV microbicide. Furthermore, chol-siRNAs could help elucidate the pathways of HIV transmission and understand the immunologic function of DCs in the genital tract.

Anatomical and physiological aspects of the HIV infection pathogenesis in animal models

Understanding the entire pathogenesis of HIV infection, from penetration at the gates of infection to the induction of severe immunodeficiency, is an essential tool for the development of new treatment methods. Less than 40 years of research into the mechanisms of HIV infection that lead to the development of acquired immunodeficiency syndrome have accumulated a huge amount of information, but HIV's own unique variability identifies new whitespaces. Despite the constant improvement of the protocols of antiretroviral therapy and the success of its use, it has not yet been possible to stop the spread of HIV infection. The development of new protocols and the testing of new groups of antiretroviral drugs is possible, first of all, due to the improvement of animal models of the HIV infection pathogenesis. Their relevance, undoubtedly increases, but still depends on specific research tasks, since none of the in vivo models can comprehensively simulate the mechanism of the infection pathology in humans which leads to multi-organ damage. The aim of the review was to provide up-to-date information on known animal models of HIV infection, focusing on the method of their infection and anatomical, physiological and pathological features.

The development and improvement of immunodeficient mice and humanized immune system mouse models

Animal models play an indispensable role in the study of human diseases. However, animal models of different diseases do not fully mimic the complex internal environment of humans. Immunodeficient mice are deficient in certain genes and do not express these or show reduced expression in some of their cells, facilitating the establishment of humanized mice and simulation of the human environment in vivo. Here, we summarize the developments in immunodeficient mice, from the initial nude mice lacking T lymphocytes to NOD/SCID rg^null mice lacking T, B, and NK cell populations. We describe existing humanized immune system mouse models based on immunodeficient mice in which human cells or tissues have been transplanted to establish a human immune system, including humanized-peripheral blood mononuclear cells (Hu-PBMCs), humanized hematopoietic stem cells (Hu-HSCs), and humanized bone marrow, liver, thymus (Hu-BLT) mouse models. The different methods for their development involve varying levels of complexity and humanization. Humanized mice are widely used in the study of various diseases to provide a transitional stage for clinical research. However, several challenges persist, including improving the efficiency of reconstructing the human B cell immune response, extending lifespan, improving the survival rate of mice to extend the observation period, and improving the development of standardized commercialized models and as well as their use. Overall, there are many opportunities and challenges in the development of humanized immune system mouse models which can provide novel strategies for understanding the mechanisms and treatments of human disease.

Effects of Immunomodulatory Drug Fingolimod (FTY720) on Chlamydia Dissemination and Pathogenesis

Fingolimod (FTY720), an FDA-approved immunomodulatory drug for treating multiple sclerosis, is an agonist of sphingosine-1-phosphate receptor (S1PR), which has been used as a research tool for inhibiting immune cell trafficking. FTY720 was recently reported to inhibit Chlamydia dissemination. Since genital Chlamydia spreading to the gastrointestinal tract correlated with its pathogenicity in the upper genital tract, we evaluated the effect of FTY720 on chlamydial pathogenicity in the current study. Following an intravaginal inoculation, live chlamydial organisms were detected in mouse rectal swabs. FTY720 treatment significantly delayed live organism shedding in the rectal swabs. However, FTY720 failed to block chlamydial spreading to the gastrointestinal tract. The live chlamydial organisms recovered from rectal swabs reached similar levels between mice with or without FTY720 treatment by day 42 in C57BL/6J and day 28 in CBA/J mice, respectively. Thus, genital Chlamydia is able to launch a 2nd wave of spreading via an FTY720-resistant pathway after the 1st wave of spreading is inhibited by FTY720. As a result, all mice developed significant hydrosalpinx. The FTY720-resistant spreading led to stable colonization of chlamydial organisms in the colon. Consistently, FTY720 did not alter the colonization of intracolonically inoculated Chlamydia Thus, we have demonstrated that, following a delay in chlamydial spreading caused by FTY720, genital Chlamydia is able to both spread to the gastrointestinal tract via an FTY720-resistant pathway and maintain its pathogenicity in the upper genital tract. Further characterization of the FTY720-resistant pathway(s) explored by Chlamydia for spreading to the gastrointestinal tract may promote our understanding of Chlamydia pathogenic mechanisms.

HIV-Captured DCs Regulate T Cell Migration and Cell-Cell Contact Dynamics to Enhance Viral Spread

Trafficking of cell-associated HIV-1 from the genital mucosa to lymphoid organs represents a critical first step toward systemic infection. Mature DCs capture and transmit HIV-1 to T cells, but insights into DC-to-T cell viral spread dynamics within a 3-dimensional environment is lacking. Using live-cell imaging, we show that mature DCs rapidly compartmentalize HIV-1 within surface-accessible invaginations near the uropod. HIV-1 capture did not interfere with DC migration toward lymph node homing chemo-attractants and their ability to enter lymphatic vessels. However, HIV-captured DCs engaged in prolonged contacts with autologous CD4+ T cells, which led to high T cell infection. Interestingly, we show that surface bound, virion-associated Env induced signal transduction in motile T cells that facilitated prolonged DC:T cell interactions, partially through high-affinity LFA-1 expression. Together, we describe a mechanism by which surface bound HIV-1 particles function as signaling receptors that regulate T cell motility, cell-cell contact dynamics, and productive infection.

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Mature DCs compartmentalize HIV particles near the uropodia via Siglec-1 receptor

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HIV-captured DCs respond to lymph node-homing chemokines and access lymphatics

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Prolonged contacts between HIV-captured DCs and CD4 T cells facilitate virus transfer

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Surface-accessible HIV particles can induce T cell signaling via Env:CD4 engagement

Impact of Standard Bacterial Vaginosis Treatment on the Genital Microbiota, Immune Milieu, and Ex Vivo Human Immunodeficiency Virus Susceptibility

BACKGROUND

Genital immunology is a key determinant of human immunodeficiency virus (HIV) susceptibility. Both factors are modulated by bacterial vaginosis (BV) and, to some extent, by Lactobacillus iners, the genital Lactobacillus spp. that predominates in African, Caribbean, and other Black (ACB) women. We conducted a clinical trial to assess the impact of oral metronidazole treatment on the genital immune parameters of HIV acquisition risks in Kenyan women with BV.

METHODS

The primary endpoint was ex vivo cervical CD4+ T-cell HIV susceptibility after 1 month; secondary endpoints included genital cytokine/chemokine levels, cervical immune cell populations, and the composition of the cervico-vaginal microbiota by 16S ribosomal RNA gene amplicon sequencing.

RESULTS

BV resolved (Nugent score ≤ 3) at 1 month in 20/45 participants, and cervical CD4+ T-cell HIV entry was moderately reduced in all participants, regardless of treatment outcome. Resolution of BV and reduced abundances of BV-associated gram-negative taxa correlated with reduced genital interleukin (IL)-1α/β. However, BV resolution and the concomitant colonization by Lactobacillus iners substantially increased several genital chemokines associated with HIV acquisition, including interferon-γ inducible protein (IP)-10, macrophage inflammatory protein (MIP)-3α, and monokine induced by gamma interferon (MIG). In an independent cohort of ACB women, most of whom were BV-free, vaginal chemokines were again closely linked with L. iners abundance, though not other Lactobacillus spp.

CONCLUSIONS

BV treatment reduced genital CD4+ T-cell HIV susceptibility and IL-1 levels, but dramatically increased the genital chemokines that may enhance HIV susceptibility; the latter effect was related to the restoration of an Lactobacillus iners-dominated microbiota. Further studies are needed before treatment of asymptomatic BV can be recommended for HIV prevention in ACB communities.

HIV-1 and SIV Infection Are Associated with Early Loss of Lung Interstitial CD4+ T Cells and Dissemination of Pulmonary Tuberculosis

Lung interstitial CD4+ T cells are critical for protection against pulmonary infections, but the fate of this population during HIV-1 infection is not well described. We studied CD4+ T cells in the setting of HIV-1 infection in human lung tissue, humanized mice, and a Mycobacterium tuberculosis (Mtb)/simian immunodeficiency virus (SIV) nonhuman primate co-infection model. Infection with a CCR5-tropic strain of HIV-1 or SIV results in severe and rapid loss of lung interstitial CD4+ T cells but not blood or lung alveolar CD4+ T cells. This is accompanied by high HIV-1 production in these cells in vitro and in vivo. Importantly, during early SIV infection, loss of lung interstitial CD4+ T cells is associated with increased dissemination of pulmonary Mtb infection. We show that lung interstitial CD4+ T cells serve as an efficient target for HIV-1 and SIV infection that leads to their early depletion and an increased risk of disseminated tuberculosis.

Corleis et al. show that lung parenchymal CD4+ T cells are permissive to HIV-1-dependent cell death. CD4+ T cell loss is highly significant in the interstitium but not the alveolar space, and loss of interstitial CD4+ T cells is associated with extrapulmonary dissemination of M. tuberculosis.

Impact of Endemic Infections on HIV Susceptibility in Sub-Saharan Africa

Human immunodeficiency virus (HIV) remains a leading cause of global morbidity with the highest burden in Sub-Saharan Africa (SSA). For reasons that are incompletely understood, the likelihood of HIV transmission is several fold higher in SSA than in higher income countries, and most of these infections are acquired by young women. Residents of SSA are also exposed to a variety of endemic infections, such as malaria and various helminthiases that could influence mucosal and systemic immunology. Since these immune parameters are important determinants of HIV acquisition and progression, this review explores the possible effects of endemic infections on HIV susceptibility and summarizes current knowledge of the epidemiology and underlying immunological mechanisms by which endemic infections could impact HIV acquisition. A better understanding of the interaction between endemic infections and HIV may enhance HIV prevention programs in SSA.

In Vivo Imaging-Driven Approaches to Study Virus Dissemination and Pathogenesis

Viruses are causative agents for many diseases and infect all living organisms on the planet. Development of effective therapies has relied on our ability to isolate and culture viruses in vitro, allowing mechanistic studies and strategic interventions. While this reductionist approach is necessary, testing the relevance of in vitro findings often takes a very long time. New developments in imaging technologies are transforming our experimental approach where viral pathogenesis can be studied in vivo at multiple spatial and temporal resolutions. Here, we outline a vision of a top-down approach using noninvasive whole-body imaging as a guide for in-depth characterization of key tissues, physiologically relevant cell types, and pathways of spread to elucidate mechanisms of virus spread and pathogenesis. Tool development toward imaging of infectious diseases is expected to transform clinical diagnosis and treatment.

Cell-Associated Simian Immunodeficiency Virus Accelerates Initial Virus Spread and CD4+ T-Cell Depletion in the Intestinal Mucosa

Cell-free and cell-associated human immunodeficiency virus (HIV) may differently affect the immune system and the efficacy of prevention strategies. Here we examined mucosal events in simian immunodeficiency virus (SIV) infection, using infected cells together with cell-free virus and cell-free virus alone. Intravenously inoculated SIV-infected cells disseminated virus to the intestine within 16 hours. Infection with both virus forms accelerated viral dissemination in the intestinal mucosa and the loss of mucosal CD4+ T cells as compared to infection with cell-free virus only. As all natural sources of HIV infection contain both virus forms, future prevention studies should focus on efficacy against both cell-free and cell-associated virus.

HIV-1 Balances the Fitness Costs and Benefits of Disrupting the Host Cell Actin Cytoskeleton Early after Mucosal Transmission

HIV-1 primarily infects T lymphocytes and uses these motile cells as migratory vehicles for effective dissemination in the host. Paradoxically, the virus at the same time disrupts multiple cellular processes underlying lymphocyte motility, seemingly counterproductive to rapid systemic infection. Here we show by intravital microscopy in humanized mice that perturbation of the actin cytoskeleton via the lentiviral protein Nef, and not changes to chemokine receptor expression or function, is the dominant cause of dysregulated infected T cell motility in lymphoid tissue by preventing stable cellular polarization required for fast migration. Accordingly, disrupting the Nef hydrophobic patch that facilitates actin cytoskeletal perturbation initially accelerates systemic viral dissemination after female genital transmission. However, the same feature of Nef was subsequently critical for viral persistence in immune-competent hosts. Therefore, a highly conserved activity of lentiviral Nef proteins has dual effects and imposes both fitness costs and benefits on the virus at different stages of infection.

Live attenuated varicella-zoster virus vaccine does not induce HIV target cell activation

BACKGROUND

Varicella-zoster virus (VZV) is under consideration as a promising recombinant viral vector to deliver foreign antigens including HIV. However, new vectors have come under increased scrutiny, since trials with adenovirus serotype 5-vectored (Ad5-vectored) HIV vaccine demonstrated increased HIV risk in individuals with pre-immunity to the vector that was thought to be associated with mucosal immune activation (IA). Therefore, given the prospect of developing an HIV/VZV chimeric vaccine, it is particularly important to define the impact of VZV vaccination on IA.

METHODS

Healthy VZV-seropositive Kenyan women (n = 44) were immunized with high-dose live attenuated VZV vaccine, and we assessed the expression on CD4+ T cells isolated from blood, cervix, and rectum of IA markers including CD38 and HLA-DR and of markers of cell migration and tissue retention, as well as the concentration of genital and intestinal cytokines. A delayed-start group (n = 22) was used to control for natural variations in these parameters.

RESULTS

Although immunogenic, VZV vaccination did not result in significant difference in the frequency of cervical activated (HLA-DR+CD38+) CD4+ T cells (median 1.61%, IQR 0.93%-2.76%) at 12 weeks after vaccination when compared with baseline (median 1.58%, IQR 0.75%-3.04%), the primary outcome for this study. VZV vaccination also had no measurable effect on any of the IA parameters at 4, 8, and 12 weeks after vaccination.

CONCLUSION

This study provides the first evidence to our knowledge about the effects of VZV vaccination on human mucosal IA status and supports further evaluation of VZV as a potential vector for an HIV vaccine.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02514018.

FUNDING

Primary support from the Canadian Institutes for Health Research (CIHR). For other sources, see Acknowledgments.

B cells are the predominant mediators of early systemic viral dissemination during rectal LCMV infection

Determining the magnitude of local immune response during mucosal exposure to viral pathogens is critical to understanding the mechanism of viral pathogenesis. We previously showed that vaginal inoculation of lymphocytic choriomeningitis virus (LCMV) fails to induce a robust innate immune response in the lower female reproductive tract (FRT), allowing high titer viral replication and a delay in T-cell-mediated viral control. Despite this immunological delay, LCMV replication remained confined mainly to the FRT and the draining iliac lymph node. Here, we show that rectal infection with LCMV triggers type I/III interferon responses, followed by innate immune activation and lymphocyte recruitment to the colon. In contrast to vaginal exposure, innate immunity controls LCMV replication in the colon, but virus rapidly disseminates systemically. Virus-induced inflammation promotes the recruitment of LCMV target cells to the colon followed by splenic viral dissemination by infected B cells, and to a lesser extent by CD8 T cells. These findings demonstrate major immunological differences between vaginal and rectal exposure to the same viral pathogen, highlighting unique risks associated with each of these common routes of sexual viral transmission.

Frequency of Human CD45+ Target Cells is a Key Determinant of Intravaginal HIV-1 Infection in Humanized Mice

Approximately 40% of HIV-1 infections occur in the female genital tract (FGT), primarily through heterosexual transmission. FGT factors determining outcome of HIV-1 exposure are incompletely understood, limiting prevention strategies. Here, humanized NOD-Rag1^−/− γc^−/− mice differentially reconstituted with human CD34+ -enriched hematopoietic stem cells (Hu-mice), were used to assess target cell frequency and viral inoculation dose as determinants of HIV-1 infection following intravaginal (IVAG) challenge. Results revealed a significant correlation between HIV-1 susceptibility and hCD45+ target cells in the blood, which correlated with presence of target cells in the FGT, in the absence of local inflammation. HIV-1 plasma load was associated with viral dose at inoculation and frequency of target cells. Events following IVAG HIV-1 infection; viral dissemination and CD4 depletion, were not affected by these parameters. Following IVAG inoculation, HIV-1 titres peaked, then declined in vaginal lavage while plasma showed a reciprocal pattern. The greatest frequency of HIV-1-infected (p24+) cells were found one week post-infection in the FGT versus blood and spleen, suggesting local viral amplification. Five weeks post-infection, HIV-1 disseminated into systemic tissues, in a dose-dependent manner, followed by depletion of hCD45+ CD3+ CD4+ cells. Results indicate target cell frequency in the Hu-mouse FGT is a key determinant of HIV-1 infection, which might provide a useful target for prophylaxis in women.