Search

ABSTRACT Staphylococcus aureus produces numerous virulence factors, each contributing different mechanisms to bacterial pathogenesis in a spectrum of diseases. Alpha toxin (AT), a cytolytic pore-forming toxin, plays a key role in skin and soft tissue infections and pneumonia, and a human anti-AT monoclonal antibody (MAb), MEDI4893*, has been shown to reduce disease severity in dermonecrosis and pneumonia infection models. However, interstrain diversity and the complex pathogenesis of S. aureus bloodstream infections suggests that MEDI4893* alone may not provide adequate protection against S. aureus sepsis. Clumping factor A (ClfA), a fibrinogen binding protein, is an important virulence factor facilitating S. aureus bloodstream infections. Herein, we report on the identification of a high-affinity anti-ClfA MAb, 11H10, that inhibits ClfA binding to fibrinogen, prevents bacterial agglutination in human plasma, and promotes opsonophagocytic bacterial killing (OPK). 11H10 prophylaxis reduced disease severity in a mouse bacteremia model and was dependent on Fc effector function and OPK. Additionally, prophylaxis with 11H10 in combination with MEDI4893* provided enhanced strain coverage in this model and increased survival compared to that obtained with the individual MAbs. The MAb combination also reduced disease severity in murine dermonecrosis and pneumonia models, with activity similar to that of MEDI4893* alone. These results indicate that an MAb combination targeting multiple virulence factors provides benefit over a single MAb neutralizing one virulence mechanism by providing improved efficacy, broader strain coverage, and protection against multiple infection pathologies. IMPORTANCE Alternative strategies to broad-spectrum antibiotics are required to combat the antibiotic resistance epidemic. Previous attempts at active or passive immunization against Staphylococcus aureus targeting single antigens have failed in clinical trials despite positive preclinical data. To provide broad disease and isolate coverage, an effective immunization strategy likely must target multiple virulence mechanisms of the pathogen. Herein, we tested a multimechanistic MAb combination targeting alpha toxin (AT) and clumping factor A (ClfA) that neutralizes AT-mediated cytotoxicity, blocks fibrinogen binding by ClfA, prevents bacterial agglutination, targets the bacteria for opsonophagocytic killing, and provides broad isolate coverage in a lethal-bacteremia model. Although each MAb alone was effective in bacteremia against some individual isolates, the MAb combination provided improved protection against other isolates. These results illustrate the importance of targeting multiple virulence mechanisms and highlight the potential for an MAb combination targeting AT and ClfA to effectively prevent S. aureus disease.

Herpes simplex virus-1 (HSV-1) establishes a latent infection in neurons and periodically reactivates to cause disease. The stimuli that trigger HSV-1 reactivation have not been fully elucidated. We demonstrate HSV-1 reactivation from latently infected mouse neurons induced by forskolin requires neuronal excitation. Stimuli that directly induce neurons to become hyperexcitable also induced HSV-1 reactivation. Forskolin-induced reactivation was dependent on the neuronal pathway of DLK/JNK activation and included an initial wave of viral gene expression that was independent of histone demethylase activity and linked to histone phosphorylation. IL-1β is released under conditions of stress, fever and UV exposure of the epidermis; all known triggers of clinical HSV reactivation. We found that IL-1β induced histone phosphorylation and increased the excitation in sympathetic neurons. Importantly, IL-1β triggered HSV-1 reactivation, which was dependent on DLK and neuronal excitability. Thus, HSV-1 co-opts an innate immune pathway resulting from IL-1 stimulation of neurons to induce reactivation., Competing Interests: SC, AS, SD, PS, JS, PK, TD, MF, BD, CB, AC No competing interests declared, (© 2020, Cuddy et al.)

Emerging multidrug-resistant bacteria are a challenge for modern medicine, but how these pathogens are so successful is not fully understood. Robust antibacterial vaccines have prevented and reduced resistance suggesting a pivotal role for immunity in deterring antibiotic resistance. Here, we show the increased prevalence of Klebsiella pneumoniae lipopolysaccharide O2 serotype strains in all major drug resistance groups correlating with a paucity of anti-O2 antibodies in human B cell repertoires. We identify human monoclonal antibodies to O-antigens that are highly protective in mouse models of infection, even against heavily encapsulated strains. These antibodies, including a rare anti-O2 specific antibody, synergistically protect against drug-resistant strains in adjunctive therapy with meropenem, a standard-of-care antibiotic, confirming the importance of immune assistance in antibiotic therapy. These findings support an antibody-based immunotherapeutic strategy even for highly resistant K. pneumoniae infections, and underscore the effect humoral immunity has on evolving drug resistance.

Vesicular stomatitis virus encoding the IFNβ transgene (VSV-IFNβ) is a mediator of potent oncolytic activity and is undergoing clinical evaluation for the treatment of solid tumors. Emerging preclinical and clinical data suggest treatment of tumors with oncolytic viruses may sensitize tumors to checkpoint inhibitors and increase the anti-tumor immune response. New generations of immuno-oncology molecules including T cell agonists are entering clinical development and could be hypothesized to enhance the activity of oncolytic viruses, including VSV-IFNβ. Here, we show that VSV-IFNβ exhibits multiple mechanisms of action, including direct cell killing, stimulation of an innate immune response, recruitment of CD8 T cells, and depletion of T regulatory cells. Moreover, VSV-IFNβ promotes the establishment of a CD8 T cell response to endogenous tumor antigens. Our data demonstrate a significant enhancement of anti-tumor function for VSV-IFNβ when combined with checkpoint inhibitors, but not OX40 agonists. While the addition of checkpoint inhibitors to VSV-IFNβ generated robust tumor growth inhibition, it resulted in no increase in viral replication, transgene expression, or immunophenotypic changes beyond treatment with VSV-IFNβ alone. We hypothesize that tumor-specific T cells generated by VSV-IFNβ retain activity due to a lack of immune exhaustion when checkpoint inhibitors were used., (Copyright © 2017 The American Society of Gene and Cell Therapy. Published by Elsevier Inc. All rights reserved.)

Initial promising results with immune sera guided early human mAb approaches against Gram-negative sepsis to an LPS neutralization mechanism, but these efforts failed in human clinical trials. Emergence of multidrug resistance has renewed interest in pathogen-specific mAbs. We utilized a pair of antibodies targeting Klebsiella pneumoniae LPS, one that both neutralizes LPS/TLR4 signaling and mediates opsonophagocytic killing (OPK) (54H7) and one that only promotes OPK (KPE33), to better understand the contribution of each mechanism to mAb protection in an acutely lethal pneumonia model. Passive immunization 24 hours prior to infection with KPE33 protected against lethal infection significantly better than 54H7, while delivery of either mAb 1 hour after infection resulted in similar levels of protection. These data suggest that early neutralization of LPS-induced signaling limits protection afforded by these mAbs. LPS neutralization prevented increases in the numbers of γδT cells, a major producer of the antimicrobial cytokine IL-17A, the contribution of which was confirmed using il17a-knockout mice. We conclude that targeting LPS for OPK without LPS signaling neutralization has potential to combat Gram-negative infection by engaging host immune defenses, rather than inhibiting beneficial innate immune pathways.

Bacterial pneumonia, such as those caused by Staphylococcus aureus, is associated with an influx of inflammatory neutrophils into the lung tissue and airways. Regulation and clearance of recruited neutrophils is essential for preventing tissue damage by "friendly fire", a responsibility of macrophages in a process called efferocytosis. We hypothesized that S. aureus impairs efferocytosis by alveolar macrophages (AMs) through the activity of the secreted virulence factor alpha toxin (AT), which has been implicated in altering the antimicrobial function of AMs. Infection of mice lacking AMs resulted in significantly increased numbers of neutrophils in the lung, while clearance of neutrophils delivered intranasally into uninfected mice was reduced in AM depleted animals. In vitro, sublytic levels of AT impaired uptake of apoptotic neutrophils by purified AMs. In vivo, the presence of AT reduced uptake of neutrophils by AMs. Differential uptake of neutrophils was not due to changes in either the CD47/CD172 axis or CD36 levels. AT significantly reduced lung expression of CCN1 and altered AM surface localization of DD1α, two proteins known to influence efferocytosis. We conclude that AT may contribute to tissue damage during S. aureus pneumonia by inhibiting the ability of AM to clear neutrophils at the site of infection., Competing Interests: We acknowledge a potential competing interest. T.S.C., O.J., M.H., L.C., J.S., C.K.S., and B.S. are employees of MedImmune L.L.C. L.M. receives funding from MedImmune L.L.C.

The 1918 influenza pandemic caused ~50 million deaths. Many questions remain regarding the origin, pathogenicity, and mechanisms of human adaptation of this virus. Avian-adapted influenza A viruses preferentially bind α2,3-linked sialic acids (Sia) while human-adapted viruses preferentially bind α2,6-linked Sia. A change in Sia preference from α2,3 to α2,6 is thought to be a requirement for human adaptation of avian influenza viruses. Autopsy data from 1918 cases, however, suggest that factors other than Sia preference played a role in viral binding and entry to human airway cells. Here, we evaluated binding and entry of five 1918 influenza receptor binding domain variants in a primary human airway cell model along with control avian and human influenza viruses. We observed that all five variants bound and entered cells efficiently and that Sia preference did not predict entry of influenza A virus to primary human airway cells evaluated in this model., (Published by Elsevier Inc.)

Unlabelled: Clinical development of a mesogenic strain of Newcastle disease virus (NDV) as an oncolytic agent for cancer therapy has been hampered by its select agent status due to its pathogenicity in avian species. Using reverse genetics, we have generated a lead candidate oncolytic NDV based on the mesogenic NDV-73T strain that is no longer classified as a select agent for clinical development. This recombinant NDV has a modification at the fusion protein (F) cleavage site to reduce the efficiency of F protein cleavage and an insertion of a 198-nucleotide sequence into the HN-L intergenic region, resulting in reduced viral gene expression and replication in avian cells but not in mammalian cells. In mammalian cells, except for viral polymerase (L) gene expression, viral gene expression is not negatively impacted or increased by the HN-L intergenic insertion. Furthermore, the virus can be engineered to express a foreign gene while still retaining the ability to grow to high titers in cell culture. The recombinant NDV selectively replicates in and kills tumor cells and is able to drive potent tumor growth inhibition following intratumoral or intravenous administration in a mouse tumor model. The candidate is well positioned for clinical development as an oncolytic virus., Importance: Avian paramyxovirus type 1, NDV, has been an attractive oncolytic agent for cancer virotherapy. However, this virus can cause epidemic disease in poultry, and concerns about the potential environmental and economic impact of an NDV outbreak have precluded its clinical development. Here we describe generation and characterization of a highly potent oncolytic NDV variant that is unlikely to cause Newcastle disease in its avian host, representing an essential step toward moving NDV forward as an oncolytic agent. Several attenuation mechanisms have been genetically engineered into the recombinant NDV that reduce chicken pathogenicity to a level that is acceptable worldwide without impacting viral production in cell culture. The selective tumor replication of this recombinant NDV, both in vitro and in vivo, along with efficient tumor cell killing makes it an attractive oncolytic virus candidate that may provide clinical benefit to patients., (Copyright © 2016, American Society for Microbiology. All Rights Reserved.)

Broad-spectrum antibiotic use may adversely affect a patient's beneficial microbiome and fuel cross-species spread of drug resistance. Although alternative pathogen-specific approaches are rationally justified, a major concern for this precision medicine strategy is that co-colonizing or co-infecting opportunistic bacteria may still cause serious disease. In a mixed-pathogen lung infection model, we find that the Staphylococcus aureus virulence factor α toxin potentiates Gram-negative bacterial proliferation, systemic spread, and lethality by preventing acidification of bacteria-containing macrophage phagosomes, thereby reducing effective killing of both S. aureus and Gram-negative bacteria. Prophylaxis or early treatment with a single α toxin neutralizing monoclonal antibody prevented proliferation of co-infecting Gram-negative pathogens and lethality while also promoting S. aureus clearance. These studies suggest that some pathogen-specific, antibody-based approaches may also work to reduce infection risk in patients colonized or co-infected with S. aureus and disparate drug-resistant Gram-negative bacterial opportunists., (Copyright © 2016, American Association for the Advancement of Science.)

Immunocompromised individuals are at increased risk of Staphylococcus aureus pneumonia. Neutralization of alpha-toxin (AT) with the monoclonal antibody (MAb) MEDI4893* protects normal mice from S. aureus pneumonia; however, the effects of the MAb in immunocompromised mice have not been reported. In this study, passive immunization with MEDI4893* increased survival rates and reduced bacterial numbers in the lungs in an immunocompromised murine S. aureus pneumonia model. Lungs from infected mice exhibited alveolar epithelial damage, protein leakage, and bacterial overgrowth, whereas lungs from mice passively immunized with MEDI4893* retained a healthy architecture, with an intact epithelial barrier. Adjunctive therapy or prophylaxis with a subtherapeutic MEDI4893* dose combined with subtherapeutic doses of vancomycin or linezolid improved survival rates, compared with the monotherapies. Furthermore, coadministration of MEDI4893* with vancomycin or linezolid extended the antibiotic treatment window. These data suggest that MAb-mediated neutralization of AT holds promise in strategies for prevention and adjunctive therapy among immunocompromised patients., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

Primary normal human bronchial/tracheal epithelial (NHBE) cells, derived from the distal-most aspect of the trachea at the bifurcation, have been used for a number of studies in respiratory disease research. Differences between the source tissue and the differentiated primary cells may impact infection studies based on this model. Therefore, we examined how well-differentiated NHBE cells compared with their source tissue, the human distal trachea, as well as the ramifications of these differences on influenza A viral pathogenesis research using this model. We employed a histological analysis including morphological measurements, electron microscopy, multi-label immunofluorescence confocal microscopy, lectin histochemistry, and microarray expression analysis to compare differentiated NHBEs to human distal tracheal epithelium. Pseudostratified epithelial height, cell type variety and distribution varied significantly. Electron microscopy confirmed differences in cellular attachment and paracellular junctions. Influenza receptor lectin histochemistry revealed that α2,3 sialic acids were rarely present on the apical aspect of the differentiated NHBE cells, but were present in low numbers in the distal trachea. We bound fluorochrome bioconjugated virus to respiratory tissue and NHBE cells and infected NHBE cells with human influenza A viruses. Both indicated that the pattern of infection progression in these cells correlated with autopsy studies of fatal cases from the 2009 pandemic., (© The Author(s) 2015.)

Unlabelled: Staphylococcus aureus is a Gram-positive, commensal bacterium known to asymptomatically colonize the human skin, nares, and gastrointestinal tract. Colonized individuals are at increased risk for developing S. aureus infections, which range from mild skin and soft tissue infections to more severe diseases, such as endocarditis, bacteremia, sepsis, and osteomyelitis. Different virulence factors are required for S. aureus to infect different body sites. In this study, virulence gene expression was analyzed in two S. aureus isolates during nasal colonization, bacteremia and in the heart during sepsis. These models were chosen to represent the stepwise progression of S. aureus from an asymptomatic colonizer to an invasive pathogen. Expression of 23 putative S. aureus virulence determinants, representing protein and carbohydrate adhesins, secreted toxins, and proteins involved in metal cation acquisition and immune evasion were analyzed. Consistent upregulation of sdrC, fnbA, fhuD, sstD, and hla was observed in the shift between colonization and invasive pathogen, suggesting a prominent role for these genes in staphylococcal pathogenesis. Finally, gene expression data were correlated to the roles of the genes in pathogenesis by using knockout mutants in the animal models. These results provide insights into how S. aureus modifies virulence gene expression between commensal and invasive pathogens., Importance: Many bacteria, such as Staphylococcus aureus, asymptomatically colonize human skin and nasal passages but can also cause invasive diseases, such as bacteremia, pneumonia, sepsis, and osteomyelitis. The goal of this study was to analyze differences in the expression of selected S. aureus genes during a commensal lifestyle and as an invasive pathogen to gain insight into the commensal-to-pathogen transition and how a bacterial pathogen adapts to different environments within a host (e.g., from nasal colonization to invasive pathogen). The gene expression data were also used to select genes for which to construct knockout mutants to assess the role of several proteins in nasal colonization and lethal bacteremia. These results not only provide insight into the factors involved in S. aureus disease pathogenesis but also provide potential therapeutic targets., (Copyright © 2015 Jenkins et al.)

Alpha-toxin (AT) is a major virulence determinant in Staphylococcus aureus skin and soft tissue infection models. We previously demonstrated that prophylactic administration of 2A3, an AT-neutralizing monoclonal antibody (MAb), prevents S. aureus disease in a mouse dermonecrosis model by neutralizing AT-mediated tissue necrosis and immune evasion. In the present study, MEDI4893*, an affinity-optimized version of 2A3, was characterized for therapeutic activity in the dermonecrosis model as a single agent and in combination with two frontline antibiotics, vancomycin and linezolid. MEDI4893* postinfection therapy was found to exhibit a therapeutic treatment window similar to that for linezolid but longer than that for vancomycin. Additionally, when combined with either vancomycin or linezolid, MEDI4893* resulted in reduced tissue damage, increased neutrophil and macrophage infiltration and abscess formation, and accelerated healing relative to those with the antibiotic monotherapies. These data suggest that AT neutralization with a potent MAb holds promise for both prophylaxis and adjunctive therapy with antibiotics and may be a valuable addition to currently available options for the treatment of S. aureus skin and soft tissue infections., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

Background: This study was conducted to determine whether treatment with motavizumab, an anti-respiratory syncytial virus (RSV) monoclonal antibody, would decrease viral load and improve clinical outcomes in previously healthy term infants hospitalized with RSV lower respiratory tract infection., Methods: Infants hospitalized with lower respiratory tract infection and a positive RSV test performed locally were randomized to receive 1 intravenous dose of motavizumab (30 or 100 mg/kg) or placebo. Nasal wash samples were tested by real-time reverse transcriptase polymerase chain reaction at a central laboratory to determine viral load. Clinical data were collected during RSV hospitalization and at 12-month follow up., Results: Of 118 infants, 112 were confirmed RSV positive by real-time reverse transcriptase polymerase chain reaction. In each study group, median (range) RSV load (log10 copies/mL) decreased at a similar rate from baseline to study day 7 [motavizumab 30 mg/kg: 8.35 (2.5-9.5) to 5.03 (2.5-6.8); motavizumab 100 mg/kg: 8.22 (5.5-9.7) to 4.25 (2.5-8.0); placebo: 8.02 (6.7-9.8) to 5.17 (2.5-7.3)]. Median (range) duration of hospitalization was 3.05 (0.8-16.0), 2.99 (1.0-25.0) and 2.88 (0.8-11.7) days for the motavizumab 30 mg/kg, motavizumab 100 mg/kg and placebo groups, respectively. Six (8%) motavizumab and 0 placebo recipients were admitted to the intensive care unit and 4 required mechanical ventilation. The incidence of wheezing episodes during the 12-month follow up was comparable for all 3 groups., Conclusions: Motavizumab had no appreciable effect on RSV viral load measured in the upper respiratory tract of children hospitalized for RSV lower respiratory tract infection. No differences were observed for duration of hospitalization, severity of illness measures or wheezing episodes during 12-month follow up in children treated with motavizumab or placebo.

Introduction: A major pathophysiologic mechanism in sepsis is impaired host immunity which results in failure to eradicate invading pathogens and increased susceptibility to secondary infections. Although many immunosuppressive mechanisms exist, increased expression of the inhibitory receptor programmed cell death 1 (PD-1) and its ligand (PD-L1) are thought to play key roles. The newly recognized phenomenon of T cell exhaustion is mediated in part by PD-1 effects on T cells. This study tested the ability of anti-PD-1 and anti-PD-L1 antibodies to prevent apoptosis and improve lymphocyte function in septic patients., Methods: Blood was obtained from 43 septic and 15 non-septic critically-ill patients. Effects of anti-PD-1, anti-PD-L1, or isotype-control antibody on lymphocyte apoptosis and interferon gamma (IFN-γ) and interleukin-2 (IL-2) production were quantitated by flow cytometry., Results: Lymphocytes from septic patients produced decreased IFN-γ and IL-2 and had increased CD8 T cell expression of PD-1 and decreased PD-L1 expression compared to non-septic patients (P<0.05). Monocytes from septic patients had increased PD-L1 and decreased HLA-DR expression compared to non-septic patients (P<0.01). CD8 T cell expression of PD-1 increased over time in ICU as PD-L1, IFN-γ, and IL2 decreased. In addition, donors with the highest CD8 PD-1 expression together with the lowest CD8 PD-L1 expression also had lower levels of HLA-DR expression in monocytes, and an increased rate of secondary infections, suggestive of a more immune exhausted phenotype. Treatment of cells from septic patients with anti-PD-1 or anti-PD-L1 antibody decreased apoptosis and increased IFN-γ and IL-2 production in septic patients; (P<0.01). The percentage of CD4 T cells that were PD-1 positive correlated with the degree of cellular apoptosis (P<0.01)., Conclusions: In vitro blockade of the PD-1:PD-L1 pathway decreases apoptosis and improves immune cell function in septic patients. The current results together with multiple positive studies of anti-PD-1 and anti-PD-L1 in animal models of bacterial and fungal infections and the relative safety profile of anti-PD-1/anti-PD-L1 in human oncology trials to date strongly support the initiation of clinical trials testing these antibodies in sepsis, a disorder with a high mortality.

Alpha-toxin (AT) is a major virulence factor in the disease pathogenesis of Staphylococcus aureus. We previously identified a monoclonal antibody (MAb) against AT that reduced disease severity in a mouse dermonecrosis model. Here, we evaluate the activity of an affinity-optimized variant, LC10, in a mouse model of S. aureus pneumonia. Passive immunization with LC10 increased survival and reduced bacterial numbers in the lungs and kidneys of infected mice and showed protection against diverse S. aureus clinical isolates. The lungs of S. aureus-infected mice exhibited bacterial pneumonia, including widespread inflammation, whereas the lungs of mice that received LC10 exhibited minimal inflammation and retained healthy architecture. Consistent with reduced immune cell infiltration, LC10-treated animals had significantly lower (P < 0.05) proinflammatory cytokine and chemokine levels in the bronchoalveolar lavage fluid than did those of the control animals. This reduction in inflammation and damage to the LC10-treated animals resulted in reduced vascular protein leakage and CO2 levels in the blood. LC10 was also assessed for its therapeutic activity in combination with vancomycin or linezolid. Treatment with a combination of LC10 and vancomycin or linezolid resulted in a significant increase (P < 0.05) in survival relative to the monotherapies and was deemed additive to synergistic by isobologram analysis. Consistent with improved survival, the lungs of animals treated with antibiotic plus LC10 exhibited less inflammatory tissue damage than those that received monotherapy. These data provide insight into the mechanisms of protection provided by AT inhibition and support AT as a promising target for immunoprophylaxis or adjunctive therapy against S. aureus pneumonia.

An optimal host response against Staphylococcus aureus skin and soft tissue infections (SSTI) is dependent on IL-1β and IL-17 mediated abscess formation. Alpha toxin (AT), an essential virulence factor for SSTI, has been reported to damage tissue integrity; however its effect on the immune response has not been investigated. Here, we demonstrate that infection with USA300 AT isogenic mutant (Δhla), or passive immunization with an AT neutralizing mAb, 2A3, 24 h prior to infection with wild type USA300 (WT), resulted in dermonecrotic lesion size reduction, and robust neutrophil infiltration. Infiltration correlates with increase in proinflammatory cytokines and chemokines, as well as enhanced bacterial clearance relative to immunization with a negative control mAb. In addition, infection with Δhla, or with WT +2A3, resulted in an early influx of innate IL-17(+)γδT cells and a more rapid induction of an adaptive immune response as measured by Th1 and Th17 cell recruitment at the site of infection. These results are the first direct evidence of a role for AT in subverting the innate and adaptive immune responses during a S. aureus SSTI. Further, these effects of AT can be overcome with a high affinity anti-AT mAb resulting in a reduction in disease severity.

Distinct roadblocks prevent translating basic findings in viral pathogenesis into therapies and implementing potential solutions in the clinic. An ongoing partnership between the Volkswagen Foundation and Nature Medicine resulted in an interactive meeting in 2012, as part of the "Herrenhausen Symposia" series. Current challenges for various fields of viral research were recognized and discussed with a goal in mind--to identify solutions and propose an agenda to address the translational barriers. Here, some of the researchers who participated at the meeting provide a concise outlook at the most pressing unmet research and clinical needs, identifying these key obstacles is a necessary step towards the prevention and cure of human viral diseases.

Human rhinovirus species C (HRV-C) was recently discovered using molecular diagnostic techniques and is associated with lower respiratory tract disease, particularly in children. HRV-C cannot be propagated in immortalized cell lines, and currently sinus organ culture is the only system described that is permissive to HRV-C infection ex vivo. However, the utility of organ culture for studying HRV-C biology is limited. Here, we report that a previously described HRV-C derived from an infectious cDNA, HRV-C15, infects and propagates in fully differentiated human airway epithelial cells but not in undifferentiated cells. We demonstrate that this differentiated epithelial cell culture system supports infection and replication of a second virus generated from a cDNA clone, HRV-C11. We show that HRV-C15 virions preferentially bind fully differentiated airway epithelial cells, suggesting that the block to replication in undifferentiated cells is at the step of viral entry. Consistent with previous reports, HRV-C15 utilizes a cellular receptor other than ICAM-1 or LDLR for infection of differentiated epithelial cells. Furthermore, we demonstrate that HRV-C15 replication can be inhibited by an HRV 3C protease inhibitor (rupintrivir) but not an HRV capsid inhibitor previously under clinical development (pleconaril). The HRV-C cell culture system described here provides a powerful tool for studying the biology of HRV-C and the discovery and development of HRV-C inhibitors.

Introduction: Factors explaining the greater susceptibility of preterm infants to severe lower respiratory infections with respiratory syncytial virus (RSV) remain poorly understood. Fetal/newborn lambs are increasingly appreciated as a model to study key elements of RSV infection in newborn infants due to similarities in lung alveolar development, immune response, and susceptibility to RSV. Previously, our laboratory demonstrated that preterm lambs had elevated viral antigen and developed more severe lesions compared to full-term lambs at seven days post-infection. Here, we compared the pathogenesis and immunological response to RSV infection in lungs of preterm and full-term lambs., Methods: Lambs were delivered preterm by Caesarian section or full-term by natural birth, then inoculated with bovine RSV (bRSV) via the intratracheal route. Seven days post-infection, lungs were collected for evaluation of cytokine production, histopathology and cellular infiltration., Results: Compared to full-term lambs, lungs of preterm lambs had a heightened pro-inflammatory response after infection, with significantly increased MCP-1, MIP-1α, IFN-γ, TNF-α and PD-L1 mRNA. RSV infection in the preterm lung was characterized by increased epithelial thickening and periodic acid-Schiff staining, indicative of glycogen retention. Nitric oxide levels were decreased in lungs of infected preterm lambs compared to full-term lambs, indicating alternative macrophage activation. Although infection induced significant neutrophil recruitment into the lungs of preterm lambs, neutrophils produced less myeloperoxidase than those of full-term lambs, suggesting decreased functional activation., Conclusions: Taken together, our data suggest that increased RSV load and inadequate immune response may contribute to the enhanced disease severity observed in the lungs of preterm lambs.

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection in children worldwide. The understanding of neonatal RSV pathogenesis depends on using an animal model that reproduces neonatal RSV disease. Previous studies from us and others demonstrated that the neonatal lamb model resembles human neonatal RSV infection. Here, we provide an extensive and detailed characterization of the histopathology, viral load, cellular infiltration, and cytokine production in lungs and tracheobronchial lymph nodes of lambs inoculated with human RSV strain A2 over the course of infection. In the lung, RSV titers were low at day 3 postinfection, increased significantly by day 6, and decreased to baseline levels at day 14. Infection in the lung was associated with an accumulation of macrophages, CD4(+) and CD8(+) T cells, and a transcriptional response of genes involved in inflammation, chemotaxis, and interferon response, characterized by increased IFNγ, IL-8, MCP-1, and PD-L1, and decreased IFNβ, IL-10, and TGF-β. Laser capture microdissection studies determined that lung macrophage-enriched populations were the source of MCP-1 but not IL-8. Immunoreactivity to caspase 3 occurred within bronchioles and alveoli of day 6-infected lambs. In lung-draining lymph nodes, RSV induced lymphoid hyperplasia, suggesting an ability of RSV to enhance lymphocytic proliferation and differentiation pathways. This study suggests that, in lambs with moderate clinical disease, RSV enhances the activation of caspase cell death and Th1-skewed inflammatory pathways, and complements previous observations that emphasize the role of inflammation in the pathogenesis of RSV disease.

Human metapneumovirus (HMPV) is a paramyxovirus causing acute respiratory tract infections in humans. The effects of a monoclonal antibody (MAb 338, MedImmune, Inc.) directed against the HMPV fusion protein were assessed in vivo. Different groups of BALB/c mice received an intraperitoneal injection of 25 or 50mg/kg of MAb 338 either 24h before or 48h after viral infection. Lung samples were collected on days 5 and 42 after infection for determination of viral titers and histopathological changes. Pulmonary functions were also evaluated by plethysmography. On day 5 post-infection, lung viral titers were significantly decreased in mice treated with 25 or 50mg/kg before or after viral infection compared to HMPV-infected control mice. Similarly, HMPV copy numbers on day 42 were decreased for all prophylactic and therapeutic interventions. Histopathological changes were also less severe in all treated groups of mice on days 5 and 42 post-infection, correlating with decreased airways obstruction. Finally, on day 42, all treated groups had a significant decrease in airways hyperresponsiveness following treatment with MAb 338. Both prophylactic and, to a lesser extent, therapeutic administration of MAb 338 improved acute and late consequences of HMPV infection in a relevant mouse model., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Previously healthy children hospitalized with respiratory syncytial virus (RSV) received motavizumab (3, 15, or 30 mg/kg intravenously), an RSV-specific monoclonal antibody, or placebo. Safety, tolerability, motavizumab concentrations, and immunogenicity were assessed. Cultivatable RSV in the upper respiratory tract was significantly reduced with motavizumab compared with placebo day 1 post-treatment. No adverse events were considered motavizumab-related by site investigators.

We have compared the cytotoxic activity of rituximab with that of blinatumomab (MT103/MEDI-538), a single-chain CD19-/CD3-bispecific antibody engaging human T cells. Blinatumomab consistently led to a higher degree of lysis of human lymphoma lines than rituximab, and was active at much lower concentration. The cytotoxicity mediated by blinatumomab and rituximab both caused a potent activation of pro-caspases 3 and 7 in target cells, a key event in induction of granzyme-mediated apoptotic cell death. Combination of rituximab with blinatumomab was found to greatly enhance the activity of rituximab, in particular at low effector-to-target cell ratios and at low antibody concentration.

Although respiratory syncytial virus (RSV) infection is the most important cause of bronchiolitis in infants, the pathogenesis of RSV disease is poorly described. We studied histopathologic changes in a panel of lung tissue specimens obtained from infants with fatal cases of primary RSV infection. In these tissues, airway occlusion with accumulations of infected, apoptotic cellular debris and serum protein was consistently observed. Similar observations were found after RSV infection in New Zealand black (NZB) mice, which have constitutive deficiencies in macrophage function, but not in BALB/c mice. A deficiency in the number of alveolar macrophages in NZB mice appears to be central to enhanced disease, because depletion of alveolar macrophages in BALB/c mice before RSV exposure resulted in airway occlusion. In mice with insufficient numbers of macrophages, RSV infection yielded an increased viral load and enhanced expression of type I interferon-associated genes at the height of disease. Together, our data suggest that innate, rather than adaptive, immune responses are critical determinants of the severity of RSV bronchiolitis.

Human metapneumovirus (hMPV) is genetically related to respiratory syncytial virus (RSV); both cause respiratory tract illnesses ranging from a mild cough to bronchiolitis and pneumonia. The F protein-directed monoclonal antibody (mAb) palivizumab has been shown to prevent severe lower respiratory tract RSV infection in animals and humans. We have previously reported on a panel of mAbs against the hMPV F protein that neutralize hMPV in vitro and, in two cases, in vivo. Here we describe the generation of hMPV mAb-resistant mutants (MARMs) to these neutralizing antibodies. Sequencing the F proteins of the hMPV MARMs identified several neutralizing epitopes. Interestingly, some of the epitopes mapped on the hMPV F protein coincide with homologous regions mapped previously on the RSV F protein, including the site against which the broadly protective mAb palivizumab is directed. This suggests that these homologous regions play important, conserved functions in both viruses.

Background: Human metapneumovirus (hMPV) is one of the most frequent causes of respiratory tract infections in children. Our objective was to assess the prophylactic benefit of a monoclonal antibody (mAb) against the hMPV fusion protein in a murine model., Methods: BALB/c mice received one intramuscular injection of either 5 or 10 mg/kg of mAb 338 (MedImmune, Inc.) and were infected intranasally 24 h later with 1x10(8) TCID50 (50% tissue culture infectious dose) of hMPV. On days 5 and 42 post-infection, lung samples were collected for determination of viral titres and for histopathological studies. Pulmonary function was characterized by plethysmography., Results: Mean lung viral titres were significantly lower in mice treated with 5 or 10 mg/kg of mAb 338 compared with infected controls on day 5 (283, 45.6 and 1.49x10(5) TCID50/g, respectively; P<0.05). Similarly, lung viral RNA copies were significantly reduced in treated mice on day 42 (292, 101 and 607 copies per 0.01 g of lungs for mice that received 5 mg/kg, 10 mg/kg or no mAb, respectively; P<0.05). Histopathological changes characterized by important alveolar and interstitial inflammation were less severe in treated mice on days 5 and 42 compared with control. Airways obstruction was also significantly reduced in both treated groups on days 5 and 42, but development of hyperresponsiveness following the acute phase of infection was only significantly reduced in 10 mg/kg treated mice., Conclusions: Prophylactic administration of mAb 338 attenuates acute and late consequences of hMPV disease in this mouse model.

BiTE molecules comprise a new class of bispecific single-chain antibodies redirecting previously unstimulated CD8+ and CD4+ T cells for the elimination of target cells. One example is MT103 (MEDI-538; bscCD19xCD3), a CD19-specific BiTE that can induce lysis of normal and malignant B cells at low picomolar concentrations, which is accompanied by T cell activation. Here, we explored in cell culture the impact of the glucocorticoid derivative dexamethasone on various activation parameters of human T cells in response to MT103. In case cytokine-related side effects should occur with BiTE molecules and other T cell-based approaches during cancer therapy it is important to understand whether glucocorticoids do interfere with the cytotoxic potential of T cells. We found that MT103 induced in the presence of target cells secretion by peripheral T cells of interleukin (IL)-2, tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), IL-6, IL-10 and IL-4 into the cell culture medium. Production of all studied cytokines was effectively reduced by dexamethasone at a concentration between 1 and 3x10(-7) M. In contrast, upregulation of activation markers CD69, CD25, CD2 and LFA-1 on both CD4+ and CD8+ T cells, and T cell proliferation were barely affected by the steroid hormone analogue. Most importantly, dexamethasone did not detectably inhibit the cytotoxic activity of MT103-activated T cells against a human B lymphoma line as investigated with lymphocytes from 12 human donors. Glucocorticoids thus qualify as a potential co-medication for therapeutic BiTE molecules and other cytotoxic T cell therapies for treatment of cancer.

An effective virus-like particle (VLP) based prophylactic vaccine designed to protect against persistent infection with human papillomavirus (HPV) types 16 and 18 and subsequent lesion development will need to induce a strong humoral and cellular immune response capable of providing long-term protection. Our objective was to evaluate the ability of an HPV16/18 L1 VLP vaccine formulated with the AS04 adjuvant system (3-O-desacyl-4'-monophosphoryl lipid A (MPL) and aluminium salt) to induce an immune response of higher magnitude and persistence compared to a vaccine formulated with aluminium salt only. We demonstrated that MPL adsorbed onto aluminium salt retains its capacity to activate an innate immune response as assessed by the production of TNFalpha by human monocytes (U937). In addition, vaccination of mice, monkeys or human subjects with AS04 formulations induced higher total anti-L1 VLP16 and L1 VLP18 antibody responses (1.6-8.5-fold) than the aluminium salt only formulations. The enhanced antibody response induced by the AS04 vaccine formulation (1.6-4.1-fold) in monkeys and humans was shown to be targeted to functional neutralising L1 VLP16 and L1 VLP18 epitopes as assessed by V5/J4 specific ELISAs or HPV16 and HPV18 pseudo-neutralization assays. The enhanced immune profile observed with the AS04 formulation in terms of both total, V5/J4 specific and neutralizing antibodies was shown to persist for at least 3.5-year post-vaccination in human subjects. Finally, using the newly developed B cell ELISPOT assay we also demonstrated that the AS04 formulation elicited an increased frequency (2.2-5.2-fold) of HPV L1 VLP specific memory B cells when compared with the aluminium salt only formulations. These data strongly support the role of the AS04 adjuvant, which includes the immunostimulant MPL, in triggering a persistent vaccine-induced immune response of high quality.

A patient with respiratory syncytial virus (RSV) infection and severe combined immunodeficiency was studied during a 3-month period of bone marrow transplantation and palivizumab infusion. No RSV isolates with palivizumab escape mutations were identified. Donor lymphocytes, including CD8 cells, appeared to markedly reduce the RSV load but increased the pulmonary symptoms. Immunosuppressive therapy ameliorated lung disease but allowed the RSV load to rebound.

The organotypic (raft) culture system has allowed the study of the entire differentiation-dependent life cycle of human papillomaviruses (HPVs), including virion morphogenesis. We introduced linearized HPV45 genomic DNA into primary keratinocytes, where it recircularized and maintained episomally at a range of 10-50 copies of HPV genomic DNA. Following epithelial stratification and differentiation in organotypic culture, virion morphogenesis occurred. HPV45 virions were purified from raft cultures and were able to infect keratinocytes in vitro. By testing a panel of HPV VLP antisera, we were able to demonstrate that the infection was neutralized not only with human HPV45 VLP-specific antiserum, but also with human HPV18 VLP-specific antiserum, demonstrating serological cross-reactivity between HPV18 and HPV45.

Nuclei isolated from wheat embryos synthesize 4.5S precursor tRNAs and 5S rRNA in vitro. The precursor tRNAs can be processed to 4S tRNAs. Transcription of the tRNA and 5S rRNA genes is carried out by endogenous RNA polymerase III, and addition of exogenous wheat RNA polymerase III results in increased transcription on these genes. A number of experimental results suggest that proper initiation and accurate transcription of the tRNA and 5S rRNA genes occurs with isolated wheat nuclei.