Wild Mouse Gut Microbiota Promotes Host Fitness and Improves Disease Resistance.

Laboratory mice, while paramount for understanding basic biological phenomena, are limited in modeling complex diseases of humans and other free-living mammals. Because the microbiome is a major factor in mammalian physiology, we aimed to identify a naturally evolved reference microbiome to better recapitulate physiological phenomena relevant in the natural world outside the laboratory. Among 21 distinct mouse populations worldwide, we identified a closely related wild relative to standard laboratory mouse strains. Its bacterial gut microbiome differed significantly from its laboratory mouse counterpart and was transferred to and maintained in laboratory mice over several generations. Laboratory mice reconstituted with natural microbiota exhibited reduced inflammation and increased survival following influenza virus infection and improved resistance against mutagen/inflammation-induced colorectal tumorigenesis. By demonstrating the host fitness-promoting traits of natural microbiota, our findings should enable the discovery of protective mechanisms relevant in the natural world and improve the modeling of complex diseases of free-living mammals. VIDEO ABSTRACT.

Recombinant OC43 SARS-CoV-2 spike replacement virus: An improved BSL-2 proxy virus for SARS-CoV-2 neutralization assays.

We generated a replication-competent OC43 human seasonal coronavirus (CoV) expressing the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike in place of the native spike (rOC43-CoV2 S). This virus is highly attenuated relative to OC43 and SARS-CoV-2 in cultured cells and animals and is classified as a biosafety level 2 (BSL-2) agent by the NIH biosafety committee. Neutralization of rOC43-CoV2 S and SARS-CoV-2 by S-specific monoclonal antibodies and human sera is highly correlated, unlike recombinant vesicular stomatitis virus-CoV2 S. Single-dose immunization with rOC43-CoV2 S generates high levels of neutralizing antibodies against SARS-CoV-2 and fully protects human ACE2 transgenic mice from SARS-CoV-2 lethal challenge, despite nondetectable replication in respiratory and nonrespiratory organs. rOC43-CoV2 S induces S-specific serum and airway mucosal immunoglobulin A and IgG responses in rhesus macaques. rOC43-CoV2 S has enormous value as a BSL-2 agent to measure S-specific antibodies in the context of a bona fide CoV and is a candidate live attenuated SARS-CoV-2 mucosal vaccine that preferentially replicates in the upper airway.

Distinct disease features of acute and persistent genotype 3 hepatitis E virus infection in immunocompetent and immunosuppressed Mongolian gerbils.

Hepatitis E virus (HEV) causes self-limited acute hepatitis in immunocompetent individuals and can establish chronic infection in solid organ transplant recipients taking immunosuppressive drugs. A well characterized small animal model is needed to understand HEV pathogenesis. In this study, we established a robust model to study acute and persistent HEV infection using Mongolian gerbils (Meriones unguiculatus) with or without immunosuppression. Gerbils were implanted subcutaneously with continuous release tacrolimus pellet to induce immunosuppression. Gerbils with or without tacrolimus treatment were inoculated with HEV intraperitoneally. Viremia, fecal virus shedding, serum antibody and ALT levels, liver histopathological lesions, hepatocyte apoptosis, and liver macrophage distribution were assessed. Mild to moderate self-limited hepatitis and IgM and IgG antibody responses against HEV ORF2 were observed in immunocompetent gerbils. Levels of HEV-specific IgM responses were higher and lasted longer in immunocompetent gerbils with higher peak viremia. Persistent viremia and fecal virus shedding with either weak, or absent HEV antibody levels were seen in immunosuppressed gerbils. Following HEV infection, serum ALT levels were increased, with lower and delayed peaks observed in immunosuppressed compared to immunocompetent gerbils. In immunocompetent gerbils, foci of apoptotic hepatocytes were detected that were distributed with inflammatory infiltrates containing CD68+ macrophages. However, these foci were absent in immunosuppressed gerbils. The immunosuppressed gerbils showed no inflammation with no increase in CD68+ macrophages despite high virus replication in liver. Our findings suggest adaptive immune responses are necessary for inducing hepatocyte apoptosis, CD68+ macrophage recruitment, and inflammatory cell infiltration in response to HEV infection. Our studies show that Mongolian gerbils provide a promising model to study pathogenesis during acute and persistent HEV infection.

Type I interferon activation and endothelial dysfunction in caveolin-1 insufficiency-associated pulmonary arterial hypertension.

Interferonopathies, interferon (IFN)-α/ß therapy, and caveolin-1 (CAV1) loss-of-function have all been associated with pulmonary arterial hypertension (PAH). Here, CAV1-silenced primary human pulmonary artery endothelial cells (PAECs) were proliferative and hypermigratory, with reduced cytoskeletal stress fibers. Signal transducers and activators of transcription (STAT) and phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) were both constitutively activated in these cells, resulting in a type I IFN-biased inflammatory signature. Cav1-/- mice that spontaneously develop pulmonary hypertension were found to have STAT1 and AKT activation in lung homogenates and increased circulating levels of CXCL10, a hallmark of IFN-mediated inflammation. PAH patients with CAV1 mutations also had elevated serum CXCL10 levels and their fibroblasts mirrored phenotypic and molecular features of CAV1-deficient PAECs. Moreover, immunofluorescence staining revealed endothelial CAV1 loss and STAT1 activation in the pulmonary arterioles of patients with idiopathic PAH, suggesting that this paradigm might not be limited to rare CAV1 frameshift mutations. While blocking JAK/STAT or AKT rescued aspects of CAV1 loss, only AKT inhibitors suppressed activation of both signaling pathways simultaneously. Silencing endothelial nitric oxide synthase (NOS3) prevented STAT1 and AKT activation induced by CAV1 loss, implicating CAV1/NOS3 uncoupling and NOS3 dysregulation in the inflammatory phenotype. Exogenous IFN reduced CAV1 expression, activated STAT1 and AKT, and altered the cytoskeleton of PAECs, implicating these mechanisms in PAH associated with autoimmune and autoinflammatory diseases, as well as IFN therapy. CAV1 insufficiency elicits an IFN inflammatory response that results in a dysfunctional endothelial cell phenotype and targeting this pathway may reduce pathologic vascular remodeling in PAH.

Erk1/2 inactivation promotes a rapid redistribution of COP1 and degradation of COP1 substrates.

Anthrax lethal toxin (LT) is a protease virulence factor produced by Bacillus anthracis that is required for its pathogenicity. LT treatment causes a rapid degradation of c-Jun protein that follows inactivation of the MEK1/2-Erk1/2 signaling pathway. Here we identify COP1 as the ubiquitin E3 ligase that is essential for LT-induced c-Jun degradation. COP1 knockdown using siRNA prevents degradation of c-Jun, ETV4, and ETV5 in cells treated with either LT or the MEK1/2 inhibitor, U0126. Immunofluorescence staining reveals that COP1 preferentially localizes to the nuclear envelope, but it is released from the nuclear envelope into the nucleoplasm following Erk1/2 inactivation. At baseline, COP1 attaches to the nuclear envelope via interaction with translocated promoter region (TPR), a component of the nuclear pore complex. Disruption of this COP1-TPR interaction, through Erk1/2 inactivation or TPR knockdown, leads to rapid COP1 release from the nuclear envelope into the nucleoplasm where it degrades COP1 substrates. COP1-mediated degradation of c-Jun protein, combined with LT-mediated blockade of the JNK1/2 signaling pathway, inhibits cellular proliferation. This effect on proliferation is reversed by COP1 knockdown and ectopic expression of an LT-resistant MKK7-4 fusion protein. Taken together, this study reveals that the nuclear envelope acts as a reservoir, maintaining COP1 poised for action. Upon Erk1/2 inactivation, COP1 is rapidly released from the nuclear envelope, promoting the degradation of its nuclear substrates, including c-Jun, a critical transcription factor that promotes cellular proliferation. This regulation allows mammalian cells to respond rapidly to changes in extracellular cues and mediates pathogenic mechanisms in disease states.

Essential Role of Neutrophils in the Protective Immune Response Induced by a Live Attenuated Leishmania Vaccine.

No licensed vaccine exists against visceral leishmaniasis (VL), a disease caused by the Leishmania donovani parasite. We have previously reported both macrophages and dendritic cells play important role in the protection induced by a live attenuated centrin gene-deleted L. donovani (LdCen-/- ) parasite vaccine. The role of neutrophils in orchestrating the initial innate response to pathogens is widely recognized. To investigate the early interaction of LdCen-/- with neutrophils, we immunized mice intradermally in the ear pinna with LdCen-/- Compared with LdWT infection, LdCen-/- parasites induced higher recruitment of neutrophils to the ear dermis and ear draining lymph nodes (dLN) as early as 6-18 h after immunization, which were predominantly proinflammatory in nature. Neutrophils from ear dLN of LdCen-/- -immunized mice exhibited heightened expression of costimulatory molecules and attenuated expression of coinhibitory molecules necessary for higher T cell activation. Further phenotypic characterization revealed heterogeneous neutrophil populations containing Nα and Nß subtypes in the ear dLN. Of the two, the parasitized Nα subset from LdCen-/- -immunized mice exhibited much stronger Ag-specific CD4+ T cell proliferation ex vivo. Adoptive transfer of neutrophils bearing LdCen-/- parasites induced an increased Th1 response in naive mice. Importantly, neutrophil depletion significantly abrogated Ag-specific CD4+ T cell proliferation in LdCen-/- -immunized mice and impaired protection against virulent challenge. Conversely, replenishing of neutrophils significantly restored the LdCen-/- -induced host-protective response. These results suggest that neutrophils are indispensable for protective immunity induced by LdCen-/- parasite vaccine.

Antibody-dependent enhancement of influenza disease promoted by increase in hemagglutinin stem flexibility and virus fusion kinetics.

Several next-generation (universal) influenza vaccines and broadly neutralizing antibodies (bNAbs) are in clinical development. Some of these mediate inhibitions of virus replication at the postentry stage or use Fc-dependent mechanisms. Nonneutralizing antibodies have the potential to mediate enhancement of viral infection or disease. In the current study, two monoclonal antibodies (MAbs) 72/8 and 69/1, enhanced respiratory disease (ERD) in mice following H3N2 virus challenge by demonstrating increased lung pathology and changes in lung cytokine/chemokine levels. MAb 78/2 caused changes in the lung viral loads in a dose-dependent manner. Both MAbs increased HA sensitivity to trypsin cleavage at a higher pH range, suggesting MAb-induced conformational changes. pHrodo-labeled virus particles' entry and residence time in the endocytic compartment were tracked during infection of Madin-Darby canine kidney (MDCK) cells. Both MAbs reduced H3N2 virus residence time in the endocytic pathway, suggesting faster virus fusion kinetics. Structurally, 78/2 and 69/1 Fabs bound the globular head or base of the head domain of influenza hemagglutinin (HA), respectively, and induced destabilization of the HA stem domain. Together, this study describes Mab-induced destabilization of the influenza HA stem domain, faster kinetics of influenza virus fusion, and ERD in vivo. The in vivo animal model and in vitro assays described could augment preclinical safety evaluation of antibodies and next-generation influenza vaccines that generate antibodies which do not block influenza virus-receptor interaction.

Direct priming of antiviral CD8+ T cells in the peripheral interfollicular region of lymph nodes.

It is uncertain how antiviral lymphocytes are activated in draining lymph nodes, the site where adaptive immune responses are initiated. Here, using intravital microscopy we show that after infection of mice with vaccinia virus (a large DNA virus) or vesicular stomatitis virus (a small RNA virus), virions drained to the lymph node and infected cells residing just beneath the subcapsular sinus. Naive CD8+ T cells rapidly migrated to infected cells in the peripheral interfollicular region and then formed tight interactions with dendritic cells, leading to complete T cell activation. Thus, antigen presentation at the lymph node periphery, not at lymphocyte exit sites in deeper lymph node venules, as dogma dictates, has a dominant function in antiviral CD8+ T cell activation.

Influenza A Virus Negative Strand RNA Is Translated for CD8+ T Cell Immunosurveillance.

Probing the limits of CD8+ T cell immunosurveillance, we inserted the SIINFEKL peptide into influenza A virus (IAV)-negative strand gene segments. Although IAV genomic RNA is considered noncoding, there is a conserved, relatively long open reading frame present in segment 8, encoding a potential protein termed NEG8. The biosynthesis of NEG8 from IAV has yet to be demonstrated. Although we failed to detect NEG8 protein expression in IAV-infected mouse cells, cell surface Kb-SIINFEKL complexes are generated when SIINFEKL is genetically appended to the predicted C terminus of NEG8, as shown by activation of OT-I T cells in vitro and in vivo. Moreover, recombinant IAV encoding of SIINFEKL embedded in the negative strand of the neuraminidase-stalk coding sequence also activates OT-I T cells in mice. Together, our findings demonstrate both the translation of sequences on the negative strand of a single-stranded RNA virus and its relevance in antiviral immunosurveillance.

Determinants in the Ig Variable Domain of Human HAVCR1 (TIM-1) Are Required To Enhance Hepatitis C Virus Entry.

Hepatitis C virus (HCV) is the leading cause of chronic hepatitis in humans. Several host molecules participate in HCV cell entry, but this process remains unclear. The complete unraveling of the HCV entry process is important to further understand viral pathogenesis and develop therapeutics. Human hepatitis A virus (HAV) cellular receptor 1 (HAVCR1), CD365, also known as TIM-1, functions as a phospholipid receptor involved in cell entry of several enveloped viruses. Here, we studied the role of HAVCR1 in HCV infection. HAVCR1 antibody inhibited entry in a dose-dependent manner. HAVCR1 soluble constructs neutralized HCV, which did not require the HAVCR1 mucinlike region and was abrogated by a mutation of N to A at position 94 (N94A) in the Ig variable (IgV) domain phospholipid-binding pocket, indicating a direct interaction of the HAVCR1 IgV domain with HCV virions. However, knockout of HAVCR1 in Huh7 cells reduced but did not prevent HCV growth. Interestingly, the mouse HAVCR1 ortholog, also a phospholipid receptor, did not enhance infection and a soluble form failed to neutralize HCV, although replacement of the mouse IgV domain with the human HAVCR1 IgV domain restored the enhancement of HCV infection. Mutations in the cytoplasmic tail revealed that direct HAVCR1 signaling is not required to enhance HCV infection. Our data show that the phospholipid-binding function and other determinant(s) in the IgV domain of human HAVCR1 enhance HCV infection. Although the exact mechanism is not known, it is possible that HAVCR1 facilitates entry by stabilizing or enhancing attachment, leading to direct interactions with specific receptors, such as CD81.IMPORTANCE Hepatitis C virus (HCV) enters cells through a multifaceted process. We identified the human hepatitis A virus cellular receptor 1 (HAVCR1), CD365, also known as TIM-1, as a facilitator of HCV entry. Antibody blocking and silencing or knockout of HAVCR1 in hepatoma cells reduced HCV entry. Our findings that the interaction of HAVCR1 with HCV early during infection enhances entry but is not required for infection support the hypothesis that HAVCR1 facilitates entry by stabilizing or enhancing virus binding to the cell surface membrane and allowing the correct virus-receptor positioning for interaction with the main HCV receptors. Furthermore, our data show that in addition to the phospholipid-binding function of HAVCR1, the enhancement of HCV infection involves other determinants in the IgV domain of HAVCR1. These findings expand the repertoire of molecules that HCV uses for cell entry, adding to the already complex mechanism of HCV infection and pathogenesis.

Varied Role of Ubiquitylation in Generating MHC Class I Peptide Ligands.

CD8+ T cell immunosurveillance is based on recognizing oligopeptides presented by MHC class I molecules. Despite decades of study, the importance of protein ubiquitylation to peptide generation remains uncertain. In this study, we examined the ability of MLN7243, a recently described ubiquitin-activating enzyme E1 inhibitor, to block overall cytosolic peptide generation and generation of specific peptides from vaccinia- and influenza A virus-encoded proteins. We show that MLN7243 rapidly inhibits ubiquitylation in a variety of cell lines and can profoundly reduce the generation of cytosolic peptides. Kinetic analysis of specific peptide generation reveals that ubiquitylation of defective ribosomal products is rate limiting in generating class I peptide complexes. More generally, our findings demonstrate that the requirement for ubiquitylation in MHC class I-restricted Ag processing varies with class I allomorph, cell type, source protein, and peptide context. Thus, ubiquitin-dependent and -independent pathways robustly contribute to MHC class I-based immunosurveillance.

TACI deficiency leads to alternatively activated macrophage phenotype and susceptibility to Leishmania infection.

The TNF family member, transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI), is a key molecule for plasma cell maintenance and is required in infections where protection depends on antibody response. Here, we report that compared with WT mouse, TACI KO Μϕs expressed lower levels of Toll-like receptors (TLRs), CD14, myeloid differentiation primary response protein 88, and adaptor protein Toll/IL-1 receptor domain-containing adapter-inducing IFN-ß and responded poorly to TLR agonists. Analysis of Μϕ phenotype revealed that, in the absence of TACI, Μϕs adapt the alternatively activated (M2) phenotype. Steady-state expression levels for M2 markers IL-4Rα, CD206, CCL22, IL-10, Arg1, IL1RN, and FIZZ1 were significantly higher in TACI KO Μϕ than in WT cells. Confirming their M2 phenotype, TACI-KO Mϕs were unable to control Leishmania major infection in vitro, and intradermal inoculation of Leishmania resulted in a more severe manifestation of disease than in the resistant C57BL/6 strain. Transfer of WT Μϕs to TACI KO mice was sufficient to significantly reduce disease severity. TACI is likely to influence Mϕ phenotype by mediating B cell-activating factor belonging to the TNF family (BAFF) and a proliferation inducing ligand (APRIL) signals because both these ligands down-regulated M2 markers in WT but not in TACI-deficient Μϕs. Moreover, treatment of Μϕs with BAFF or APRIL enhanced the clearance of Leishmania from cells only when TACI is expressed. These findings may have implications for understanding the shortcomings of host response in newborns where TACI expression is reduced and in combined variable immunodeficiency patients where TACI signaling is ablated.

The exception that reinforces the rule: crosspriming by cytosolic peptides that escape degradation.

The nature of crosspriming immunogens for CD8(+) T cell responses is highly controversial. By using a panel of T cell receptor-like antibodies specific for viral peptides bound to mouse D(b) major histocompatibility complex class I molecules, we show that an exceptional peptide (PA(224-233)) expressed as a viral minigene product formed a sizeable cytosolic pool continuously presented for hours after protein synthesis was inhibited. PA(224-233) pool formation required active cytosolic heat-shock protein 90 but not ER g96 and uniquely enabled crosspriming by this peptide. These findings demonstrate that exceptional class I binding oligopeptides that escape proteolytic degradation are potent crosspriming agents. Thus, the feeble immunogenicity of natural proteasome products in crosspriming can be attributed to their evanescence in donor cells and not an absolute inability of cytosolic oligopeptides to be transferred to and presented by professional antigen-presenting cells.

Expression, Purification, and Biological Characterization of Babesia microti Apical Membrane Antigen 1.

The intraerythrocytic apicomplexan Babesia microti, the primary causative agent of human babesiosis, is a major public health concern in the United States and elsewhere. Apicomplexans utilize a multiprotein complex that includes a type I membrane protein called apical membrane antigen 1 (AMA1) to invade host cells. We have isolated the full-length B. microti AMA1 (BmAMA1) gene and determined its nucleotide sequence, as well as the amino acid sequence of the AMA1 protein. This protein contains an N-terminal signal sequence, an extracellular region, a transmembrane region, and a short conserved cytoplasmic tail. It shows the same domain organization as the AMA1 orthologs from piroplasm, coccidian, and haemosporidian apicomplexans but differs from all other currently known piroplasmida, including other Babesia and Theileria species, in lacking two conserved cysteines in highly variable domain III of the extracellular region. Minimal polymorphism was detected in BmAMA1 gene sequences of parasite isolates from six babesiosis patients from Nantucket. Immunofluorescence microscopy studies showed that BmAMA1 is localized on the cell surface and cytoplasm near the apical end of the parasite. Native BmAMA1 from parasite lysate and refolded recombinant BmAMA1 (rBmAMA1) expressed in Escherichia coli reacted with a mouse anti-BmAMA1 antibody using Western blotting. In vitro binding studies showed that both native BmAMA1 and rBmAMA1 bind to human red blood cells (RBCs). This binding is trypsin and chymotrypsin treatment sensitive but neuraminidase independent. Incubation of B. microti parasites in human RBCs with a mouse anti-BmAMA1 antibody inhibited parasite growth by 80% in a 24-h assay. Based on its antigenically conserved nature and potential role in RBC invasion, BmAMA1 should be evaluated as a vaccine candidate.

Genetically Modified Live Attenuated Leishmania donovani Parasites Induce Innate Immunity through Classical Activation of Macrophages That Direct the Th1 Response in Mice.

Visceral leishmaniasis (VL) causes significant mortality and there is no effective vaccine. Previously, we have shown that genetically modified Leishmania donovani parasites, here described as live attenuated parasites, induce a host protective adaptive immune response in various animal models. In this study, we demonstrate an innate immune response upon infection with live attenuated parasites in macrophages from BALB/c mice both in vitro and in vivo. In vitro infection of macrophages with live attenuated parasites (compared to that with wild-type [WT] L. donovani parasites) induced significantly higher production of proinflammatory cytokines (tumor necrosis factor alpha [TNF-α], interleukin-12 [IL-12], gamma interferon [IFN-γ], and IL-6), chemokines (monocyte chemoattractant protein 1/CCL-2, macrophage inflammatory protein 1α/CCL-3, and IP-10), reactive oxygen species (ROS), and nitric oxide, while concomitantly reducing anti-inflammatory cytokine IL-10 and arginase-1 activities, suggesting a dominant classically activated/M1 macrophage response. The classically activated response in turn helps in presenting antigen to T cells, as observed with robust CD4(+) T cell activation in vitro. Similarly, parasitized splenic macrophages from live attenuated parasite-infected mice also demonstrated induction of an M1 macrophage phenotype, indicated by upregulation of IL-1ß, TNF-α, IL-12, and inducible nitric oxide synthase 2 and downregulation of genes associated with the M2 phenotype, i.e., the IL-10, YM1, Arg-1, and MRC-1 genes, compared to WT L. donovani-infected mice. Furthermore, an ex vivo antigen presentation assay showed macrophages from live attenuated parasite-infected mice induced higher IFN-γ and IL-2 but significantly less IL-10 production by ovalbumin-specific CD4(+) T cells, resulting in proliferation of Th1 cells. These data suggest that infection with live attenuated parasites promotes a state of classical activation (M1 dominant) in macrophages that leads to the generation of protective Th1 responses in BALB/c mice.

Hemin activation of innate cellular response blocks human immunodeficiency virus type-1-induced osteoclastogenesis.

The normal skeletal developmental and homeostatic process termed osteoclastogenesis is exacerbated in numerous pathological conditions and causes excess bone loss. In cancer and HIV-1-infected patients, this disruption of homeostasis results in osteopenia and eventual osteoporesis. Counteracting the factors responsible for these metabolic disorders remains a challenge for preventing or minimizing this co-morbidity associated with these diseases. In this report, we demonstrate that a hemin-induced host protection mechanism not only suppresses HIV-1 associated osteoclastogenesis, but it also exhibits anti-osteoclastogenic activity for non-infected cells. Since the mode of action of hemin is both physiological and pharmacological through induction of heme oxygenase-1 (HO-1), an endogenous host protective response to an FDA-licensed therapeutic used to treat another disease, our study suggests an approach to developing novel, safe and effective therapeutic strategies for treating bone disorders, because hemin administration in humans has previously met required FDA safety standards.

Sustained antigen delivery improves germinal center reaction and increases antibody responses in neonatal mice.

Neonates and young infants are known to have limited responses to pediatric vaccines due to reduced germinal center formation. Extended vaccine antigen dosing was previously shown to expand germinal center formation and improve humoral responses in adult mice. We report that sustained antigen delivery through sequential dosing overcomes neonatal limitations to form germinal center reactions and improves humoral immunity. Thus, vaccine strategies that extend the release of vaccine antigens may reduce the number of doses, and time needed, to achieve protective immunity in neonates and young infants.

Long-term engraftment and maturation of autologous iPSC-derived cardiomyocytes in two rhesus macaques.

Cellular therapies with cardiomyocytes produced from induced pluripotent stem cells (iPSC-CMs) offer a potential route to cardiac regeneration as a treatment for chronic ischemic heart disease. Here, we report successful long-term engraftment and in vivo maturation of autologous iPSC-CMs in two rhesus macaques with small, subclinical chronic myocardial infarctions, all without immunosuppression. Longitudinal positron emission tomography imaging using the sodium/iodide symporter (NIS) reporter gene revealed stable grafts for over 6 and 12 months, with no teratoma formation. Histological analyses suggested capability of the transplanted iPSC-CMs to mature and integrate with endogenous myocardium, with no sign of immune cell infiltration or rejection. By contrast, allogeneic iPSC-CMs were rejected within 8 weeks of transplantation. This study provides the longest-term safety and maturation data to date in any large animal model, addresses concerns regarding neoantigen immunoreactivity of autologous iPSC therapies, and suggests that autologous iPSC-CMs would similarly engraft and mature in human hearts.

Inhibition of hepatitis C virus by the cyanobacterial protein Microcystis viridis lectin: mechanistic differences between the high-mannose specific lectins MVL, CV-N, and GNA.

Plant or microbial lectins are known to exhibit potent antiviral activities against viruses with glycosylated surface proteins, yet the mechanism(s) by which these carbohydrate-binding proteins exert their antiviral activities is not fully understood. Hepatitis C virus (HCV) is known to possess glycosylated envelope proteins (gpE1E2) and to be potently inhibited by lectins. Here, we tested in detail the antiviral properties of the newly discovered Microcystis viridis lectin (MVL) along with cyanovirin-N (CV-N) and Galanthus nivalis agglutinin (GNA) against cell culture HCV, as well as their binding properties toward viral particles, target cells, and recombinant HCV glycoproteins. Using infectivity assays, CV-N, MVL, and GNA inhibited HCV with IC50 values of 0.6 nM, 30.4 nM, and 11.1 nM, respectively. Biolayer interferometry analysis demonstrated a higher affinity of GNA to immobilized recombinant HCV glycoproteins compared to CV-N and MVL. Complementary studies, including fluorescence-activated cell sorting (FACS) analysis, confocal microscopy, and pre- and post-virus binding assays, showed a complex mechanism of inhibition for CV-N and MVL that includes both viral and cell association, while GNA functions by binding directly to the viral particle. Combinations of GNA with CV-N or MVL in HCV infection studies revealed synergistic inhibitory effects, which can be explained by different glycan recognition profiles of the mainly high-mannoside specific lectins, and supports the hypothesis that these lectins inhibit through different and complex modes of action. Our findings provide important insights into the mechanisms by which lectins inhibit HCV infection. Overall, the data suggest MVL and CV-N have the potential for toxicity due to interactions with cellular proteins while GNA may be a better therapeutic agent due to specificity for the HCV gpE1E2.