Lentiviral-Vector-Based Dendritic Cell Vaccine Synergizes with Checkpoint Blockade to Clear Chronic Viral Infection.

Dendritic cell vaccines are a promising strategy for the treatment of cancer and infectious diseases but have met with mixed success. We report on a lentiviral vector-based dendritic cell vaccine strategy that generates a cluster of differentiation 8 (CD8) T cell response that is much stronger than that achieved by standard peptide-pulsing approaches. The strategy was tested in the mouse lymphocytic choriomeningitis virus (LCMV) model. Bone marrow-derived dendritic cells from SAMHD1 knockout mice were transduced with a lentiviral vector expressing the GP33 major-histocompatibility-complex (MHC)-class-I-restricted peptide epitope and CD40 ligand (CD40L) and injected into wild-type mice. The mice were highly protected against acute and chronic variant CL-13 LCMVs, resulting in a 100-fold greater decrease than that achieved with peptide epitope-pulsed dendritic cells. Inclusion of an MHC-class-II-restricted epitope in the lentiviral vector further increased the CD8 T cell response and resulted in antigen-specific CD8 T cells that exhibited a phenotype associated with functional cytotoxic T cells. The vaccination synergized with checkpoint blockade to reduce the viral load of mice chronically infected with CL-13 to an undetectable level. The strategy improves upon current dendritic cell vaccine strategies; is applicable to the treatment of disease, including AIDS and cancer; and supports the utility of Vpx-containing vectors.

Lentiviral Vector-Based Dendritic Cell Vaccine Suppresses HIV Replication in Humanized Mice.

HIV-1-infected individuals are treated with lifelong antiretroviral drugs to control the infection. A means to strengthen the antiviral T cell response might allow them to control viral loads without antiretroviral drugs. We report the development of a lentiviral vector-based dendritic cell (DC) vaccine in which HIV-1 antigen is co-expressed with CD40 ligand (CD40L) and a soluble, high-affinity programmed cell death 1 (PD-1) dimer. CD40L activates the DCs, whereas PD-1 binds programmed death ligand 1 (PD-L1) to prevent checkpoint activation and strengthen the cytotoxic T lymphocyte (CTL) response. The injection of humanized mice with DCs transduced with vector expressing CD40L and the HIV-1 SL9 epitope induced antigen-specific T cell proliferation and memory differentiation. Upon HIV-1 challenge of vaccinated mice, viral load was suppressed by 2 logs for 6 weeks. Introduction of the soluble PD-1 dimer into a vector that expressed full-length HIV-1 proteins accelerated the antiviral response. The results support development of this approach as a therapeutic vaccine that might allow HIV-1-infected individuals to control virus replication without antiretroviral therapy.

Inhibition of CUL4A Neddylation causes a reversible block to SAMHD1-mediated restriction of HIV-1.

The deoxynucleoside triphosphohydrolase SAMHD1 restricts retroviral replication in myeloid cells. Human immunodeficiency virus type 2 (HIV-2) and a simian immunodeficiency virus from rhesus macaques (SIVmac) encode Vpx, a virion-packaged accessory protein that counteracts SAMHD1 by inducing its degradation. SAMHD1 is thought to work by depleting the pool of intracellular deoxynucleoside triphosphates but has also been reported to have exonuclease activity that could allow it to degrade the viral genomic RNA or viral reverse-transcribed DNA. To induce the degradation of SAMHD1, Vpx co-opts the cullin4a-based E3 ubiquitin ligase, CRL4. E3 ubiquitin ligases are regulated by the covalent attachment of the ubiquitin-like protein Nedd8 to the cullin subunit. Neddylation can be prevented by MLN4924, a drug that inhibits the nedd8-activating enzyme. We report that MLN4924 inhibits the neddylation of CRL4, blocking Vpx-induced degradation of SAMHD1 and maintaining the restriction. Removal of the drug several hours postinfection released the block. Similarly, Vpx-containing virus-like particles and deoxynucleosides added to the cells more than 24 h postinfection released the SAMHD1-mediated block. Taken together, these findings support deoxynucleoside triphosphate pool depletion as the primary mechanism of SAMHD1 restriction and argue against a nucleolytic mechanism, which would not be reversible.

Checkpoint inhibitor-expressing lentiviral vaccine suppresses tumor growth in preclinical cancer models.

BACKGROUND: While immunotherapy has been highly successful for the treatment of some cancers, for others, the immune response to tumor antigens is weak leading to treatment failure. The resistance of tumors to checkpoint inhibitor therapy may be caused by T cell exhaustion resulting from checkpoint activation. METHODS: In this study, lentiviral vectors that expressed T cell epitopes of an experimentally introduced tumor antigen, ovalbumin, or the endogenous tumor antigen, Trp1 were developed. The vectors coexpressed CD40 ligand (CD40L), which served to mature the dendritic cells (DCs), and a soluble programmed cell death protein 1 (PD-1) microbody to prevent checkpoint activation. Vaccination of mice bearing B16.OVA melanomas with vector-transduced DCs induced the proliferation and activation of functional, antigen-specific, cytolytic CD8 T cells. RESULTS: Vaccination induced the expansion of CD8 T cells that infiltrated the tumors to suppress tumor growth. Vector-encoded CD40L and PD-1 microbody increased the extent of tumor growth suppression. Adoptive transfer demonstrated that the effect was mediated by CD8 T cells. Direct injection of the vector, without the need for ex vivo transduction of DCs, was also effective. CONCLUSIONS: This study suggests that therapeutic vaccination that induces tumor antigen-specific CD8 T cells coupled with a vector-expressed checkpoint inhibitor can be an effective means to suppress the growth of tumors that are resistant to conventional immunotherapy.

Thematic analysis to explore patients' experiences with long COVID-19: a conceptual model of symptoms and impacts on daily lives.

OBJECTIVES: There is limited qualitative research on patients' experiences with long COVID-19, and how specific symptoms impact their daily lives. The study aimed to understand patients' lived experiences of long COVID-19 and to develop a conceptual model representing the symptoms and their impact on overall quality of life. SETTING: Qualitative study consisting of a comprehensive literature review, and in-depth clinician and patient semistructured interviews. PARTICIPANTS: Forty-one adult patients with long COVID-19, of whom 18 (44%) were recruited through Regeneron Pharmaceuticals's clinical trials and 23 (56%) through recruitment agencies; 85.4% were female and 73.2% were White. Five independent clinicians treating patients with long COVID-19 were interviewed. Concept saturation was also assessed. PRIMARY AND SECONDARY OUTCOMES: Interview transcripts were analysed thematically to identify concepts of interest spontaneously mentioned by patients, including symptoms and their impacts on daily life, to guide the development of the conceptual model. RESULTS: Findings from the literature review and clinician and patient interviews resulted in the development of a conceptual model comprising two overarching domains: symptoms (upper respiratory tract, lower respiratory tract, smell and taste, systemic, gastrointestinal, neurocognitive and other) and impacts (activities of daily living, instrumental activities of daily living, physical impacts, emotional, social/leisure activities and professional impacts). Saturation was achieved for the reported impacts. The symptoms reported were heterogenic; neurocognitive symptoms, such as numbness, ringing in ears, haziness, confusion, forgetfulness/memory problems, brain fog, concentration, difficulties finding the right word and challenges with fine motor skills, were particularly pertinent for several months. CONCLUSION: The conceptual model, developed based on patient experience data of long COVID-19, highlighted numerous symptoms that impact patients' physical and mental well-being, and suggests humanistic unmet needs. Prospective real-world studies are warranted to understand the pattern of long COVID-19 experienced in larger samples over longer periods of time.

Directly injected lentiviral vector-based T cell vaccine protects mice against acute and chronic viral infection.

Lentiviral vector-based dendritic cell vaccines induce protective T cell responses against viral infection and cancer in animal models. In this study, we tested whether preventative and therapeutic vaccination could be achieved by direct injection of antigen-expressing lentiviral vector, obviating the need for ex vivo transduction of dendritic cells. Injected lentiviral vector preferentially transduced splenic dendritic cells and resulted in long-term expression. Injection of a lentiviral vector encoding an MHC class I-restricted T cell epitope of lymphocytic choriomeningitis virus (LCMV) and CD40 ligand induced an antigen-specific cytolytic CD8+ T lymphocyte response that protected the mice from infection. The injection of chronically infected mice with a lentiviral vector encoding LCMV MHC class I and II T cell epitopes and a soluble programmed cell death 1 microbody rapidly cleared the virus. Vaccination by direct injection of lentiviral vector was more effective in sterile alpha motif and HD-domain containing protein 1-knockout (SAMHD1-knockout) mice, suggesting that lentiviral vectors containing Vpx, a lentiviral protein that increases the efficiency of dendritic cell transduction by inducing the degradation of SAMHD1, would be an effective strategy for the treatment of chronic disease in humans.

Recent Advances in Lentiviral Vaccines for HIV-1 Infection.

The development of an effective HIV vaccine to prevent and/or cure HIV remains a global health priority. Given their central role in the initiation of adaptive immune responses, dendritic cell (DC)-based vaccines are being increasingly explored as immunotherapeutic strategies to enhance HIV-specific T cells in infected individuals and, thus, promote immune responses that may help facilitate a functional cure. HIV-1-based lentiviral (LV) vectors have inherent advantages as DC vaccine vectors due to their ability to transduce non-dividing cells and integrate into the target cell genomic DNA, allowing for expression of encoded antigens over the lifespan of the cell. Moreover, LV vectors may express additional immunostimulatory and immunoregulatory proteins that enhance DC function and direct antigen-specific T cells responses. Recent basic and clinical research efforts have broadened our understanding of LV vectors as DC-based vaccines. In this review, we provide an overview of the pre-clinical and clinical LV vector vaccine studies for treating HIV to date. We also discuss advances in LV vector designs that have enhanced DC transduction efficiency, target cell specificity, and immunogenicity, and address potential safety concerns regarding LV vector-based vaccines.

Corrigendum: Recent Advances in Lentiviral Vaccines for HIV-1 Infection.

[This corrects the article on p. 243 in vol. 7, PMID: 27446074.].

HIV type 1 infection of plasmacytoid and myeloid dendritic cells is restricted by high levels of SAMHD1 and cannot be counteracted by Vpx.

Dendritic cells are professional antigen-presenting cells of the immune system and are major producers of type-I interferon. Their role in HIV-1 infection is not well understood. They express CD4 and CCR5 yet appear to be resistant to infection. In culture, infection of the cells with HIV-1 is inhibited by the host cell restriction factor SAMHD1. Lentiviruses such as HIV-2/SIVmac counteract the restriction by encoding Vpx, a virion-packaged accessory protein that induces the proteasomal degradation of SAMHD1. In this study we investigated SAMHD1-mediated restriction in the two major dendritic cell subsets: plasmacytoid dendritic cells (pDC) and myeloid dendritic cells (mDC). The cells were highly resistant to HIV-1 and expressed high levels of SAMHD1. SAMHD1 amino acid residue T592, a target of CDK1 phosphorylation, was unphosphorylated, corresponding to the antiviral form of the enzyme. The resistance to infection was not counteracted by Vpx and SAMHD1 was not degraded in these cells. Treatment of pDCs with a cocktail of antibodies that blocked type-I interferon signaling partially restored the ability of Vpx to induce SAMHD1 degradation and caused the cells to become partially permissive to infection. pDCs and mDCs responded to HIV-1 virions by inducing an innate immune response but did not appear to sense newly produced Gag protein. The findings suggest that in vivo, dendritic cells serve as sentinels to alert the immune system to the virus but do not themselves become infected by virtue of high levels of SAMHD1.

Orthopedic surgical site infections: analysis of causative bacteria and implications for antibiotic stewardship.

Data that can be used to guide perioperative antibiotic prophylaxis in our era of emerging antibiotic resistance are limited. We reviewed orthopedic surgeries complicated by surgical site infections (SSIs). Eighty percent of 69 arthroplasty and 80 spine fusion SSIs were infected with Gram-positive bacteria; most were staphylococcal species; and more than 25% of Staphylococcus aureus and more than 65% of coagulase-negative staphylococci were methicillin-resistant. Gram-negative bacteria were isolated from 30% of arthroplasty SSIs and 25% of spine fusion SSIs. Resistance to cefazolin was higher than 40%. A significant proportion of SSIs were caused by resistant organisms, and antibiotic guidelines were altered to provide more adequate surgical prophylaxis.

Vanishing bile duct syndrome in human immunodeficiency virus infected adults: a report of two cases.

Vanishing bile duct syndrome (VBDS) is a group of rare disorders characterized by ductopenia, the progressive destruction and disappearance of intrahepatic bile ducts leading to cholestasis. Described in association with medications, autoimmune disorders, cancer, transplantation, and infections, the specific mechanisms of disease are not known. To date, only 4 cases of VBDS have been reported in human immunodeficiency virus (HIV) infected patients. We report 2 additional cases of HIV-associated VBDS and review the features common to the HIV-associated cases. Presentation includes hyperbilirubinemia, normal liver imaging, and negative viral and autoimmune hepatitis studies. In HIV-infected subjects, VBDS occurred at a range of CD4+ T-cell counts, in some cases following initiation or change in antiretroviral therapy. Lymphoma was associated with two cases; nevirapine, antibiotics, and viral co-infection were suggested as etiologies in the other cases. In HIV-positive patients with progressive cholestasis, early identification of VBDS and referral for transplantation may improve outcomes.

Markers of endothelial dysfunction, coagulation and tissue fibrosis independently predict venous thromboembolism in HIV.

OBJECTIVE: HIV infection is associated with coagulation abnormalities and significantly increased risk of venous thrombosis. It has been shown that higher plasma levels of coagulation and inflammatory biomarkers predicted mortality in HIV. We investigated the relationship between venous thrombosis and HIV-related characteristics, traditional risk factors of hypercoagulability, and pre-event levels of biomarkers. DESIGN: A retrospective case-control study of 23 HIV-infected individuals who experienced an incident venous thromboembolic event while enrolled in National Institutes of Health studies from 1995 to 2010 and 69 age-matched and sex-matched HIV-infected individuals without known venous thromboembolism (VTE). METHODS: Biomarkers of inflammation, endothelial dysfunction, coagulation, tissue fibrosis, and cytomegalovirus (CMV) reactivation were assessed by ELISA-based assays and PCR using plasma obtained prior to the event. RESULTS: VTE events were related to nadir CD4 cell count, lifetime history of multiple opportunistic infections, CMV disease, CMV viremia, immunological AIDS, active infection, and provocation (i.e., recent hospitalization, surgery, or trauma). VTE events were independently associated with increased plasma levels of P-selectin (P = 0.002), D-dimer (P = 0.01), and hyaluronic acid (P = 0.009) in a multivariate analysis. No significant differences in antiretroviral or interleukin-2 exposures, plasma HIV viremia, or other traditional risk factors were observed. CONCLUSION: Severe immunodeficiency, active infection, and provocation are associated with venous thromboembolic disease in HIV. Biomarkers of endothelial dysfunction, coagulation, and tissue fibrosis may help identify HIV-infected patients at elevated risk of VTE.