Abstract Introduction Neutrophil antimicrobial responses are triggered by direct pathogen recognition or binding of antibody-antigen immune complexes (ICs) to cell-surface receptors. Although known to be critical for control of diverse bacterial and viral infections, neutrophil responses to HIV-1 and HIV-antibody ICs (HIV-ICs), remain poorly defined. We hypothesized that HIV-ICs enhance neutrophil antiviral activity and that antibody specificity and subclass influence virus elimination. Methods HIV-ICs were formed by incubating monoclonal antibodies (mAbs) with fluorescent HIV-1 virions. Peripheral blood neutrophils were exposed to HIV and HIV-ICs. Phagocytosis was assessed by flow cytometry and microscopy. To test viral inactivation, HIV-IC-loaded neutrophils were co-cultured with permissive cells containing an HIV-driven luciferase reporter gene. Neutrophil activation, degranulation, and reactive oxygen species (ROS) production were measured following phagocytosis. Matrix metalloproteinase-9 levels in supernatants were measured to evaluate degranulation. Results HIV-ICs formed with IgG3 mAbs induce more than double the binding and phagocytosis of HIV than IgG1 mAbs, and 30-fold more than free HIV virions. Phagocytosis effectively removed infectious HIV, though non-internalized HIV could be transferred from neutrophils to permissive cells. Surprisingly, we found that neutrophils did not produce robust ROS or significant release of cytotoxic granules in response to HIV-ICs. Consistent with these latter findings, we did not observe significant changes in the activation state of neutrophils following stimulation with HIV-ICs. Conclusion Our findings reveal that while HIV-ICs mediate neutrophil binding and phagocytosis of HIV-1, these interactions do not trigger additional antimicrobial responses. Moreover, neutrophils can transfer extracellularly bound, but not internalized, HIV-1 to permissive cells. These findings reveal that neutrophils can limit HIV transmission only through successful internalization of HIV-ICs. Funding Source NIAID P01 AI162242. H Conley is supported by NIH T32 AI007392 Topic Categories Viral Immunology (VIR)

BACKGROUND:The HVTN108 trial evaluated the safety and immunogenicity of a DNA prime, adjuvanted protein boost HIV vaccine in the United States and South Africa. The underlying factors influencing individual variation in vaccine responsiveness are unknown. In this study, we defined the IgG Fc and Fc receptor (FcR) genotypes in the HVTN108 cohort to test our hypothesis that IgG and FcR genetic variation can affect vaccine-elicited functional antibody responses. METHODS:IgG Fc and FcR alleles were determined by targeted PCR amplification and next-generation sequencing. Vaccine-elicited functional antibody responses, including binding antibody multiplex assay (BAMA), antibody-dependent cellular cytotoxicity (ADCC), and antibody-dependent cellular phagocytosis (ADCP) activity, were measured using standardized and qualified methods. Relationships between alleles and antibody responses were identified by linear regression controlling for treatment group and region. RESULTS:The distribution of many polymorphisms significantly differed between the United States and South Africa. Within the subset of the cohort tested for functional antibody responses (IgG, n = 41; FcR, n = 55), IgG genotypes such as IGHG1*12 ( P = 0.012), IGHG3*11 ( P = 0.033), IGHG2*02 ( P = 0.038), IGHG4*07 ( P = 0.076), and others were associated with ADCC antibody responses when corrected for vaccine group and regional effects. In the same way, we identified that the FCER1A rs2427827 mutation had a significant association with lower peak ADCC activity and the FCER2 rs2228137 mutation was associated with lower antibody binding to Con6 gp120 protein. CONCLUSIONS:Genetic variation in both antibodies and FcRs associated with levels of HIV-vaccine-elicited functional antibodies. Significant regional differences in distribution of this variation support the need for vaccine testing in diverse populations.

Adjuvants play an important role in modulating antigen-specific immune responses. We conducted a comparative adjuvant immunogenicity study in Rhesus macaques using HIV-1 subtype B gp120 envelope protein, B.63521, formulated with aluminum hydroxide gel (AH), or a family of liposomal adjuvants known as Army Liposome Formulation (ALF). ALF comprises saturated phospholipids, cholesterol, and monophosphoryl lipid A. Inclusion of QS-21 or adsorption of the antigen to AH, followed by the addition of ALF, generates ALFQ and ALFA, while inclusion of both immunostimulants generates ALFQA. Priming with canarypox vector ALVAC, followed by boosting with ALVAC and gp120 formulated with each of the four adjuvants, resulted in ALFQ and ALFQA outperforming AH and ALFA vaccine formulations with a high frequency of antigen-specific plasma cells in the bone marrow, robust antibodies, and Env-specific polyfunctional CD8+ T cell responses. Transcriptomic analyses revealed upregulation of antiviral and innate immune pathways, thus highlighting ALFQ as a highly potent adjuvant.

Background: Antibody-dependent cell-mediated cytotoxic (ADCC) response mediated by natural killer (NK) cells correlates with decreased infection risk in studies involving simian immunodeficiency virus (SIV)/simian-human immunodeficiency virus (SHIV), and human immunodeficiency virus (HIV) vaccine candidates. Currently, the heterogeneities of the functional subset of rhesus macaque natural killer (RMNK) cells are under-characterized. Method: We engaged the RMNK cells with ADCC-mediating anti-HIV-1 monoclonal antibodies (ADCCAbs) or anti-CD16 antibodies and used CD107a expression as the surrogate marker for RMNK cells actively involved in ADCC. CD107a+ and CD107a– populations were analyzed individually using single-cell RNA sequencing. Results: Subsets of CD107a+ RMNK cells produced more chemokines than the others, suggesting that these cells not only eliminate infected cells but also provide immunoregulatory signals and potentially curb HIV-1 replication. Crosslinking of Fc gamma receptor IIIa via anti-CD16 antibodies resulted in a significantly higher percentage of degranulating cells than via ADCCAbs. However, the magnitude of degranulation and chemokine production was reduced by 6- to 30-fold. Conclusion: The quality and quantity of receptor engagement are important determinants of achieving an optimal level of the RMNK response.

BACKGROUND:Sequential multivalent immunizations are used to counter diversity in rapidly mutating viruses. Here, we evaluated the effect of HIV-1 immunogen formats on the binding profile of memory B-cells elicited in two independent Rhesus macaque trials. METHODS:In one trial, female Rhesus macaques were immunized with a multiclade HIV-1 gp120 envelope glycoprotein (Env) cocktail and bled two weeks post final immunization. In another trial, male and female Rhesus macaques were sequentially immunized with clonally-related Env glycoproteins: Four immunogens were administered as non-stabilized gp140 Envs and the fifth as a specially stabilized gp140 Env trimer (SOSIP); animals were bled before and after SOSIP immunization. Immunogen-binding peripheral memory B-cells were sorted and cultured at limiting dilution. Culture supernatants were assessed by ELISA for binding to individual immunogens. RESULTS:In the first trial, 81% (591/734) of B-cells cross-react with multiple Envs and most bind to all immunogens. In the second trial, 81% (331/410) of B-cells isolated before SOSIP administration react with all non-stabilized gp140 Env immunogens and 27% also cross-react with the yet-to-be-administered SOSIP-stabilized Env. However, after SOSIP administration, SOSIP-stabilized trimer-reactive B-cells increase to 86% (219/256) but most (82%) do not cross-react with the preceding immunogens. CONCLUSIONS:Multiclade and sequential regimens before SOSIP-stabilized Env immunization elicited B-cells that converge on shared epitopes. A change in immunogen format results in a divergent B-cell response that vastly fails to engage prior responses. Critically, B-cell priming with non-stabilized Env cannot modify the effect of the epitope immunodominance hierarchy in a SOSIP trimer. These results suggest that a change in immunogen format may cause off-target B-cell engagement, but also that B-cell repriming is possible despite pre-existing immunity.

Evaluation of HIV cure strategies requires antiretroviral therapy (ART) interruption, but ethical and clinical considerations make this difficult in children. Here, we used a pediatric preclinical model of simian-HIV (SHIV) infection to uncover features associated with time to viral rebound (TTR) and posttreatment control (PTC) of rebound viremia after ART interruption to inform the design of studies testing cure interventions. We assessed 141 variables in SHIV-infected infant rhesus macaques in three staggered ART initiation groups and during subsequent analytical treatment interruption (ATI). Viral rebound occurred in 25 of 30 macaques within 7 to 98 days of ATI, with TTR delayed in the early ART group compared with the intermediate and late ART groups. Peak plasma viral load pre-ART was the most important correlate of TTR, with increased model performance through the successive inclusion of six additional viral and immune variables. The odds of PTC were reduced with higher SHIV RNA in rectal CD4+ T cells pre-ATI; conversely, higher frequencies of Ki67+ effector memory CD8+ T cells in lymph nodes increased the likelihood of PTC. RNA sequencing of CD4+ T cells pre-ATI revealed a down-regulated metabolic and immune gene signature in macaques with PTC. Analysis of the early ART group alone implicated transforming growth factor-β signaling genes in lack of viral rebound off ART. This comprehensive investigation reveals major determinants of viral rebound dynamics after ART interruption that should be validated and explored as potential biomarkers to screen children with HIV being considered for ATI.

Purpose: Chronic viral infections such as CMV, HIV, and HCV are associated with an expansion of CD8 T cells that adopt Natural Killer cell (NK)-like transcriptional profile and functions. Most of these cells are a subset of Terminally Differentiated Effector Memory (TEMRA) CD8, cell type that is enriched in the lungs of patients with COPD and has been associated with rejection in kidney transplant. A subset of NK-like TEMRA CD8 express CD16, the receptor that allow NK cells to eliminate cells bound by donor specific antibodies (DSA).

Background. The clinical success of liver transplantation has led to increased demand, requiring further expansion of the donor pool. Therapeutic interventions to optimize organs from donation after circulatory death (DCD) have significant potential to mitigate the organ shortage. Dysfunction in DCD liver grafts is mediated by microvascular thrombosis during the warm ischemic period, and strategies that reduce this thrombotic burden may improve graft function. We hypothesized that the administration of the fibrinolytic enzyme plasmin to the donor organ during the cold storage period would reduce the thrombotic burden and improve DCD liver graft function. Methods. In 2 separate cohorts, 32 syngeneic orthotopic rat liver transplants were performed in Lewis rats. Livers were procured from donors with 45 min of warm ischemic injury. Liver grafts were flushed with histidine-tryptophan-ketoglutarate preservation solution mixed with either plasmin (experimental group) or albumin (control group). All investigators were blinded to treatment group. After preparing the liver for implant using a modified cuff technique, the liver was stored for 1 h by static cold storage at 4 °C. Immediately before implantation, the liver graft was flushed, and this effluent was analyzed for fibrin degradation products to determine graft clot burden. Twenty-four hours following transplantation, animals were euthanized, and samples were collected. Results. Recipient survival was significantly higher for DCD liver grafts treated with plasmin compared with control. Moreover, histology of liver graft tissue immediately before implant reflected significantly reduced congestion in plasmin-treated livers (score, mean ± SD: 0.73 ± 0.59 versus 1.12 ± 0.48; P = 0.0456). The concentration of fibrin degradation products in the final flush before implantation was significantly reduced in plasmin-treated livers (743 ± 136 versus 10 919 ± 4642 pg/mL; P = 0.0001), reflecting decreased clot burden in the graft. Conclusions. The present study demonstrates that plasmin improves survival and may reduce thrombotic burden in DCD liver grafts with prolonged warm ischemic injury, meriting further study.

Sterile inflammation is the immune response to damage-associated molecular patterns (DAMPs) released during cell death in the absence of foreign pathogens. In the setting of solid organ transplantation, ischemia-reperfusion injury results in mitochondria-mediated production of reactive oxygen and nitrogen species that are a major cause of uncontrolled cell death and release of various DAMPs from the graft tissue. When properly regulated, the immune response initiated by DAMP-sensing serves as means of damage control and is necessary for initiation of recovery pathways and re-establishment of homeostasis. In contrast, a dysregulated or overt sterile inflammatory response can inadvertently lead to further injury through recruitment of immune cells, innate immune cell activation, and sensitization of the adaptive immune system. In liver transplantation, sterile inflammation may manifest as early graft dysfunction, acute graft failure, or increased risk of immunosuppression-resistant rejection. Understanding the mechanisms of the development of sterile inflammation in the setting of liver transplantation is crucial for finding reliable biomarkers that predict graft function, and for development of therapeutic approaches to improve long-term transplant outcomes. Here, we discuss the recent advances that have been made to elucidate the early signs of sterile inflammation and extent of damage from it. We also discuss new therapeutics that may be effective in quelling the detrimental effects of sterile inflammation.

Human cytomegalovirus (HCMV) profoundly modulates host T and natural killer (NK) cells across the lifespan, expanding unique effector cells bridging innate and adaptive immunity. Though HCMV is the most common congenital infection worldwide, how this ubiquitous herpesvirus impacts developing fetal T and NK cells remains unclear. Using computational flow cytometry and transcriptome profiling of cord blood from neonates with and without congenital HCMV (cCMV) infection, we identify major shifts in fetal cellular immunity marked by an expansion of Fc{gamma} receptor III (Fc{gamma}RIII)-expressing CD8+ T cells (FcRT) following HCMV exposure in utero. FcRT cells from cCMV-infected neonates express a cytotoxic NK cell-like transcriptome and mediate antigen-specific antibody-dependent functions including degranulation and IFN{gamma} production, the hallmarks of NK cell antibody-dependent cellular cytotoxicity (ADCC). FcRT cells may represent a previously unappreciated effector population with innate-like functions that could be harnessed for maternal-infant vaccination strategies and antibody-based therapeutics in early life.

A better understanding of the impact of early innate immune responses after vaccine priming on vaccine-elicited adaptive immune responses could inform rational design for effective HIV vaccines. The current study compared the whole blood molecular immune signatures of a 3M-052-SE adjuvanted HIV Env protein vaccine to a regimen combining the adjuvanted Env protein with simultaneous administration of a modified Vaccinia Ankara vector expressing HIV Env in infant rhesus macaques at days 0, 1, and 3 post vaccine prime. Both vaccines induced a rapid innate response, evident by elevated inflammatory plasma cytokines and altered gene expression. We identified 25 differentially-expressed genes (DEG) on day 1 compared to day 0 in the HIV protein vaccine group. In contrast, in the group that received both the Env protein and the MVA-Env vaccine only two DEG were identified, implying that the MVA-Env modified the innate response to the adjuvanted protein vaccine. By day 3, only three DEG maintained altered expression, indicative of the transient nature of the innate response. The DEG represented immune pathways associated with complement activation, type I interferon and interleukin signaling, pathogen sensing, and induction of adaptive immunity. DEG expression on day 1 was correlated to Env-specific antibody responses, in particular antibody-dependent cytotoxicity responses at week 34, and Env-specific follicular T helper cells. Results from network analysis supported the interaction of DEG and their proteins in B cell activation. These results emphasize that vaccine-induced HIV-specific antibody responses can be optimized through the modulation of the innate response to the vaccine prime.

BackgroundSubnormothermic machine perfusion (SNMP) of liver grafts is currently less clinically developed than normothermic and hypothermic approaches, but may have logistical advantages. At intermediate temperatures, the oxygen demand of the graft is low enough to be satisfied with an acellular perfusate, obviating the need for oxygen carrying molecules. This intermediate metabolic rate, however, is sufficient to support the production of bile, which is emerging as an important indicator of graft injury and viability. In this study, we hypothesized that the biliary compartment would be more sensitive than perfusate in detecting graft injury during SNMP.MethodsTo test this hypothesis in a rat model, we performed liver transplants with DCD and control liver grafts after 1 h of acellular room temperature machine perfusion (acRTMP) or static cold storage (SCS). Point of care liver function tests were measured in biliary and perfusate samples after 1 h of machine perfusion. Following transplantation, rats were sacrificed at 24 h for assessment of post-transplant graft function and histology.ResultsAll point-of-care liver function tests were significantly more concentrated in the biliary compartment than the perfusate compartment during acRTMP. DCD liver grafts could be distinguished from control liver grafts by significantly higher markers of hepatocyte injury (AST, ALT) in the biliary compartment, but not in the perfusate compartment. Classical markers of cholangiocyte injury, such as gammy-glut amyl transferase (GGT), amylase (AML), and alkaline phosphatase were detectable in the biliary compartment, but not in the perfusate compartment. In comparison to SCS, graft preservation by acRTMP produced a significant survival benefit in DCD liver transplantation (75 vs. 0%, p < 0.0030).ConclusionTogether, these findings demonstrate that during acRTMP, the biliary compartment may be a more sensitive indicator of graft injury than the perfusate compartment. Moreover, acRTMP provides superior graft preservation to SCS in rat DCD liver transplantation.

Additional file 2. Table S3: Genes upregulated in each cluster in scRNA-seq total PBMC.

ABSTRACT Current efforts toward human immunodeficiency virus (HIV) eradication include approaches to augment immune recognition and elimination of persistently infected cells following latency reversal. Natural killer (NK) cells, the main effectors of the innate immune system, recognize and clear targets using different mechanisms than CD8 + T cells, offering an alternative or complementary approach for HIV clearance strategies. We assessed the impact of interleukin 15 (IL-15) treatment on NK cell function and the potential for stimulated NK cells to clear the HIV reservoir. We measured NK cell receptor expression, antibody-dependent cell-mediated cytotoxicity (ADCC), cytotoxicity, interferon gamma (IFN-γ) production, and antiviral activity in autologous HIV replication systems. All NK cell functions were uniformly improved by IL-15, and, more importantly, IL-15-treated NK cells were able to clear latently HIV-infected cells after exposure to vorinostat, a clinically relevant latency-reversing agent. We also demonstrate that NK cells from HIV-infected individuals aviremic on antiretroviral therapy can be efficiently stimulated with IL-15. Our work opens a promising line of investigation leading to future immunotherapies to clear persistent HIV infection using NK cells. IMPORTANCE In the search for an HIV cure, strategies to enhance immune function to allow recognition and clearance of HIV-infected cells following latency reversal are being evaluated. Natural killer (NK) cells possess characteristics that can be exploited for immunotherapy against persistent HIV infection. We demonstrate that NK cells from HIV-positive donors can be strongly stimulated with IL-15, improving their antiviral and cytotoxic potential and, more importantly, clearing HIV-infected cells after latency reversal with a clinically relevant drug. Our results encourage further investigation to design NK cell-based immunotherapies to achieve HIV eradication.

The benefits of mucosal vaccines over injected vaccines are difficult to ascertain since mucosally administered vaccines often induce serum antibody responses of lower magnitude than those induced by injected vaccines. This study aimed to determine if mucosal vaccination using a modified vaccinia Ankara expressing HIV-1 gp120 (MVA-g120) prime and HIV-1 gp120 protein boost could be optimized to induce serum antibody responses similar to those induced by an intramuscularly (IM) administered MVA prime/gp120 boost to allow comparison of an IM immunization regimen to a mucosal vaccination regimen for their ability to protect against a low dose rectal SHIV challenge while inducing similar serum anti-HIV-1 antibody responses. A 3-fold higher antigen dose was required for intranasal (IN) immunization with gp120 to induce serum anti-gp120 IgG responses not significantly different than those induced by IM immunization. Gp120 fused to the Adenovirus type 2 fiber binding domain (gp120-Ad2F), a mucosal targeting ligand, exhibited enhanced IN immunogenicity when compared to gp120 alone. MVA-gp120 was more immunogenic after IN delivery than gastric or rectal delivery, although serum antibodies induced by IN immunization were lower than those induced by intramuscular immunization. Using these optimized vaccines, an IN MVA-gp120 prime, combined IM (gp120) and IN (gp120-Ad2F) boost regimen (IN/IM+IN) induced serum anti-gp120 antibody titers similar to those induced by the intramuscular prime/boost regimen (IM/IM) in rabbits and non-human primates. Despite the induction of similar systemic anti-HIV-1 antibody responses, neither the IM/IM nor the IN/IM+IN regimen induced elevated anti-HIV-1 mucosal IgA responses nor protected against a repeated low-dose rectal SHIV challenge. These results demonstrate that immunization regimens utilizing the IN route are able to induce serum antigen-specific antibody responses similar to those induced by systemic immunization IMPORTANCE Mucosal vaccination is proposed as a method of immunization able to induce protection against mucosal pathogens that is superior to protection provided by parenteral immunization. However, mucosal vaccination often induces serum antigen-specific immune responses of lower magnitude than those induced by parenteral immunization, making the comparison of mucosal and parenteral immunization difficult. We identified vaccine parameters that allowed an immunization regimen consisting of an IN prime followed with boosters administered by both IN and IM routes to induce serum antibody responses similar to those induced by IM prime/boost vaccination. Additional studies are needed to determine the potential benefit of mucosal immunization for HIV-1 and other mucosally-transmitted pathogens.

Without novel strategies to prevent mother-to-child HIV-1 transmission, more than 5% of HIV-1-exposed infants will continue to acquire HIV-1, most through breastfeeding. This study of rhesus macaque dam-and-infant pairs is the first preclinical study to investigate the protective role of transplacentally transferred HIV-1 vaccine-elicited antibodies and HIV-1 vaccine-elicited breast milk antibody responses in infant oral virus acquisition. It revealed highly variable placental transfer of potentially protective antibodies and emphasized the importance of pregnancy immunization timing to reach peak antibody levels prior to delivery. While there was no discernible impact of maternal immunization on late infant oral virus acquisition, we observed a strong correlation between the percentage of activated CD4 + T cells in infant peripheral blood and a reduced number of challenges to infection. This finding highlights an important consideration for future studies evaluating alternative strategies to further reduce the vertical HIV-1 transmission risk.