Faculty perceptions and knowledge of career development of trainees in biomedical science: What do we (think we) know?

The Broadening Experiences in Scientific Training (BEST) program is an NIH-funded effort testing the impact of career development interventions (e.g. internships, workshops, classes) on biomedical trainees (graduate students and postdoctoral fellows). BEST Programs seek to increase trainees' knowledge, skills and confidence to explore and pursue expanded career options, as well as to increase training in new skills that enable multiple career pathways. Faculty mentors are vital to a trainee's professional development, but data about how faculty members of biomedical trainees view the value of, and the time spent on, career development are lacking. Seven BEST institutions investigated this issue by conducting faculty surveys during their BEST experiment. The survey intent was to understand faculty perceptions around professional and career development for their trainees. Two different, complementary surveys were employed, one designed by Michigan State University (MSU) and the other by Vanderbilt University. Faculty (592) across five institutions responded to the MSU survey; 225 faculty members from two institutions responded to the Vanderbilt University survey. Participating faculty were largely tenure track and male; approximately 1/3 had spent time in a professional position outside of academia. Respondents felt a sense of urgency in introducing broad career activities for trainees given a recognized shortage of tenure track positions. They reported believing career development needs are different between a graduate student and postdoctoral fellow, and they indicated that they actively mentor trainees in career development. However, faculty were uncertain as to whether they actually have the knowledge or training to do so effectively. Faculty perceived that trainees themselves lack a knowledge base of skills that are of interest to non-academic employers. Thus, there is a need for exposure and training in such skills. Faculty stated unequivocally that institutional support for career development is important and needed. BEST Programs were considered beneficial to trainees, but the awareness of local BEST Programs and the national BEST Consortium was low at the time surveys were employed at some institutions. It is our hope that the work presented here will increase the awareness of the BEST national effort and the need for further career development for biomedical trainees.

Virus-Induced Demyelination: The Case for Virus(es) in Multiple Sclerosis

Multiple Sclerosis (MS) is the most common demyelinating disease of man with over 400,000 cases in the United States and over 2.5 million cases worldwide. There are over 64,000 citations in Pubmed dating back as far as 1887. Much has been learned over the past 129 years with a recent burst in therapeutic options (mostly anti-inflammatory) with newer medications in development that are neuroprotective and/or neuroreparative. However, with all these advancements the cause of MS remains elusive. There is a clear interplay of genetic, immunologic, and environmental factors that influences both the development and progression of this disorder. This chapter will give a brief overview of the history and pathogenesis of MS with attention to how host immune responses in genetically susceptible individuals contribute to the MS disease process. In addition, we will explore the role of infectious agents in MS as potential “triggers” of disease. Models of virus-induced demyelination will be discussed, with an emphasis on the recent interest in human herpesviruses and the role they may play in MS disease pathogenesis. Although we remain circumspect as to the role of any microbial pathogen in MS, we suggest that only through well-controlled serological, cellular immune, molecular, and animal studies we will be able to identify candidate agents. Ultimately, clinical interventional trials that either target a specific pathogen or class of pathogens will be required to make definitive links between the suspected agent and MS.

The Role of Bats as Reservoir Hosts of Emerging Neuroviruses

Recent studies have clearly shown that bats are the reservoir hosts of a wide diversity of novel viruses with representatives from most of the known animal virus families. In many respects bats make ideal reservoir hosts for viruses: they are the only mammals that fly, thus assisting in virus dispersal; they roost in large numbers, thus aiding transmission cycles; some bats hibernate over winter, thus providing a mechanism for viruses to persist between seasons; and genetic factors may play a role in the ability of bats to host viruses without resulting in clinical disease. Within the broad diversity of viruses found in bats are some important neurological pathogens, including rabies and other lyssaviruses, and Hendra and Nipah viruses, two recently described viruses that have been placed in a new genus, Henipaviruses in the family Paramyxoviridae. In addition, bats can also act as alternative hosts for the flaviviruses Japanese encephalitis and St Louis encephalitis viruses, two important mosquito-borne encephalitogenic viruses, and bats can assist in the dispersal and over-wintering of these viruses. Bats are also the reservoir hosts of progenitors of SARS and MERS coronaviruses, although other animals act as spillover hosts. This chapter presents the physiological and ecological factors affecting the ability of bats to act as reservoirs of neurotropic viruses, and describes the major transmission cycles leading to human infection.

Interferon-induced tetherin restricts vesicular stomatitis virus release in neurons

Tetherin, a recently identified interferon (IFN)-inducible, type 2 transmembrane protein, has been shown to be a cellular antiviral restriction factor that retains newly formed virions in infected cells. Thus, tetherin plays an important role in the innate cell-autonomous immune response. The aim of this study was to examine the antiviral activities of tetherin in vesicular stomatitis virus infections of murine neuronal cells. Both IFN-β and IFN-γ induce the expression of tetherin mRNA and protein. Tetherin knockdown experiments were carried out by transfection of tethrin shRNA into murine neuroblastoma cells using a vector containing the pCMV-driven tGFP gene. The efficiency of transfection was monitored through GFP expression by the transfected cells. Selected transfected cells were used for further mRNA and protein analysis, fluorescent immunocytolocalization, and viral infection to study the impact of tetherin knockdown. Our research indicates that tetherin is expressed on the outer face of the plasma membrane of murine neuroblastoma cells, its expression can be induced with both IFN-γ and IFN-β, and tetherin restricts progeny virus release up to 100-fold in mammalian neurons, thus contributing to a potent antiviral state within the host cell.

Cannabinoids and Viral Infections

Exogenous cannabinoids or receptor antagonists may influence many cellular and systemic host responses. The anti-inflammatory activity of cannabinoids may compromise host inflammatory responses to acute viral infections, but may be beneficial in persistent infections. In neurons, where innate antiviral/pro-resolution responses include the activation of NOS-1, inhibition of Ca²⁺ activity by cannabinoids, increased viral replication and disease. This review examines the effect(s) of cannabinoids and their antagonists in viral infections.

Vesicular stomatitis virus modified with single chain IL-23 exhibits oncolytic activity against tumor cells in vitro and in vivo

Viruses are potentially attractive agents for development as novel oncolytic agents. Reverse genetic approaches allow for the attenuation of candidate viruses and can enhance their ability to exploit inherent cellular and molecular properties of tumors, including deficiencies in interferon (IFN) signaling. Vesicular stomatitis virus (VSV) is a promising oncolytic agent for exactly these reasons. VSV infection of immunocompetent mice is usually rapidly cleared due to the virus' sensitivity to type I IFN responses. However, in tumors that are unable to activate the IFN response, VSV is able to replicate without inhibition, resulting in cell destruction. Unfortunately, when VSV is introduced into mice intranasally or systemically via therapeutic doses into tumor-bearing rodents, hosts may develop fatal encephalitis. We have previously found that a recombinant VSV expressing the pro-inflammatory cytokine interleukin-23 (IL-23) is significantly attenuated in the central nervous system (CNS). As a result of this, we hypothesized that attenuation in the CNS is partially a result of enhanced NO response as a result of IL-23 signaling. Infection of the CNS with this virus (designated VSV23) is characterized by decreased viral replication, morbidity, and mortality. We have now extended those studies which reveal that VSV23 maintains oncolytic capacity in vitro in multiple cell lines including NB41A3 neuroblastomas, L929 adipose-derived cells, immortalized BHK-21 cells, and the murine mammary derived JC cells. Additionally, in vivo VSV23 infection results in JC tumor destruction and induces enhanced memory responses against tumor cells.

A confocal and electron microscopic comparison of interferon beta-induced changes in vesicular stomatitis virus infection of neuroblastoma and nonneuronal cells

Vesicular stomatitis virus (VSV) replication is highly sensitive to interferon (IFN)-induced antiviral responses. Pretreatment of sensitive cultured cells with IFNbeta results in a 10(4)-fold reduction in the release of infectious VSV particles. However, differences exist between the mechanisms of reduced infectious particle titers in cell lines of neuroblastoma and nonneuronal lineage. In L929-fibroblast-derived cells, using immunofluorescence confocal microscopy, infection under control conditions reveals the accumulation of VSV matrix, phosphoprotein (P), and nucleocapsid (N) proteins over time, with induced cellular morphological changes indicative of cytopathic effects (CPEs). Upon observing L929 cells that had been pretreated with IFNbeta, neither detectable VSV proteins nor CPEs were seen, consistent with type I IFN antiviral protection. When using the same techniques to observe VSV infections of NB41A3 cells, a neuroblastoma cell line, aside from similar viral progression in the untreated control cells, IFNbeta-treated cells illustrated a severely attenuated VSV infection. Attenuated VSV progression was observed through detection of VSV matrix, P, and N proteins in isolated cells during the first 8 h of infection. However, by 18-24 h postinfection all neuroblastomas had succumbed to the viral infection. Finally, upon closer inspection of IFNbeta-treated NB41A3 cells, no detectable changes in VSV protein localization were identified compared with untreated, virally infected neuroblastomas. Next, to extend our study to test our hypothesis that virion assembly is compromised within type I IFN-treated neuroblastoma cells, we employed electron microscopy to examine our experimental conditions at the ultrastructural level. Using VSV-specific antibodies in conjunction with immuno-gold reagents, we observed several similarities between the two cell lines, such as identification of viroplasmic regions containing VSV N and P proteins and signs of stress-induced CPEs of VSV-infected cells, which had either been mock-treated or pretreated with interferon-beta (IFNbeta). One difference we observed between nonneuronal and neuroblastoma cells was more numerous actively budding VSV virions across untreated L929 plasma membranes compared with untreated NB41A3 cells. Additionally, IFNbeta-treated, VSV-infected L929 cells exhibited neither cytoplasmic viroplasm nor viral protein expression. In contrast, IFNbeta-treated, VSV-infected NB41A3 cells showed evidence of VSV infection at a very low frequency as well as small-scale viroplasmic regions that colocalized with viral N and P proteins. Finally, we observed that VSV viral particles harvested from untreated VSV-infected L929 and NB41A3 cells were statistically similar in size and shape. A portion of VSV virions from IFNbeta-treated, virally infected NB41A3 cells were similar in size and shape to virus from both untreated cell types. However, among the sampling of virions, pleomorphic viral particles that were identified from IFNbeta-treated, VSV-infected NB41A3 cells were different enough to suggest a misassembly mechanism as part of the IFNbeta antiviral state in neuroblastoma cells.

IFN-beta-induced alteration of VSV protein phosphorylation in neuronal cells

Vesicular stomatitis virus (VSV) replication is highly sensitive to interferon (IFN)-induced antiviral responses. VSV infection of well-known cell lines pretreated with IFN-beta results in a 10(4)-fold reduction in the release of infectious particles, with a concomitant abrogation in viral transcript and/or protein levels. However, in cell lines of neuronal lineage only a threefold reduction in viral transcript and protein levels was observed, despite the same 10(4)-fold reduction in released infectious virions, suggesting an assembly defect. Examination of VSV matrix (M) protein ubiquitination yielded no differences between mock- and IFN-beta-treated neuronal cells. Further analysis of potential post-translational modification events, by scintillation and two-dimensional electrophoretic methods, revealed IFN-beta-induced alterations in M protein and phosphoprotein (P) phosphorylation. Hypophosphorylated P protein was demonstrated by reduced (32)P counts, normalized by (35)S-cysteine/methionine incorporation, and by a shift in isoelectric focusing. Hypophosphorylation of VSV P protein was found to occur in neuronal cell lysates, but not within budded virions from the same IFN-beta-treated cells. In contrast, hyperphosphorylation of VSV M protein was observed in both cell lysates and viral particles from IFN-beta-treated neuronal cells. Hyperphosphorylated M protein was demonstrated by increased (32)P counts relative to (35)S-cysteine/methionine normalization, and by altered isoelectric focusing in protein populations from cell and viral lysates. Hyperphosphorylated VSV M protein was found to inhibit its association with VSV nucleocapsid, suggesting a possible mechanism for type I IFN-mediated misassembly through disruption of the interactions between ribonucleoprotein cores, and hyperphosphorylated M protein bound to the plasma membrane inner leaflet.

Cytokine-modified VSV is attenuated for neural pathology, but is both highly immunogenic and oncolytic

Vesicular stomatitis virus (VSV), an enveloped, nonsegmented, negative-stranded RNA virus, is being tested by several laboratories as an antitumor agent. Unfortunately, viral infection of the central nervous system (CNS) has been observed by many groups following administration to tumor-bearing animals. In rodents, VSV encephalitis is characterized by weight-loss, paralysis, and high mortality. In order to provide protection from VSV infection of the CNS after therapeutic administration, we have attenuated VSV by the introduction of the gene encoding the proinflammatory cytokine interleukin (IL)-23, and designated the new virus VSV23. We hypothesize that while VSV23 is replicating within tumors, resulting in tumor destruction, the expression of IL-23 will enhance host antitumor and antiviral immune responses. In the event that the virus escapes from the tumor, the host's immune system will be activated and the virus will be rapidly cleared from healthy tissue. Experimental VSV23 infection of the CNS is characterized by decreased viral replication, morbidity, and mortality. VSV23 is capable of stimulating the enhanced production of nitric oxide in the CNS, which is critical for elimination of VSV from infected neurons. Intraperitoneal administration of VSV23 stimulates both nonspecific natural killer cell, virus-specific cytolytic T lymphocyte and memory virus-specific proliferative T cell responses against wild-type VSV in splenocytes. Furthermore, VSV23 is able to replicate in, and induce apoptosis of tumor cells in vitro. These data indicate that VSV23 is immunogenic, attenuated and suitable for testing as an efficacious and safe oncolytic agent.

DISTINCT MECHANISMS OF INHIBITION OF VSV REPLICATION IN NEURONS MEDIATED BY TYPE I AND TYPE II IFN

Acute viral infection of neurons presents a difficult problem to the host, since neurons are essential and not replaced, therefore cell-autonomous pathway(s) of suppressing viral replication are critical. We have examined the mechanisms by which neurons respond to exogenous interferons (IFNs) and observed that novel pathways inhibit acute vesicular stomatitis virus (VSV) replication. For both type I (IFN-beta) and Type II (IFN-gamma) interferons, post-translational modification of viral proteins contributed to the replication blockade, diminishing the efficiency of viral assembly and budding from the host neuron. IFN-gamma treatment induces the accumulation of NOS-1 in the absence of an increase of mRNA encoding this enzyme; a NOS-1-inhibiting protein, PIN, is rapidly ubiquitinated and eliminated in the presence of IFN-gamma. NOS-1 produces NO which combines with superoxide to form peroxynitrite (ONOO-), this binds tyrosines, cysteines, and serines; antagonism of NOS-1 with either non-specific or selective inhibitors block the antiviral effect of IFN-gamma. VSV proteins are decorated with -NO(2) in IFN-gamma-treated neurons, probably resulting in their diminished ability to interact properly and mature into budding virus. For IFN-beta, protein phosphorylation of the Matrix protein (M) and Phosphoprotein (P) were altered in infected neurons, with hyperphosphorylation of M (but not hypophosphorylated P) found in released virions. Hyperphosphorylated M protein does not immunoprecipitate with the viral ribonucleoprotein complex in IFN-beta-treated neurons. Thus both types of IFN interfere with viral assembly and release of infectious particles, but by distinct pathways.

Disruption of IFN-gamma- mediated antiviral activity in neurons: the role of cannabinoids

Interferon-gamma (IFN-gamma) has potent antiviral activity in neurons which is affected by the production of nitric oxide (NO). This study examines the interactions between cannabinoid receptor-1 (CB(1)), IFNgamma-induced pathways, and inhibition of vesicular stomatitis virus (VSV) replication in neuronal cells. CB(1) is abundantly expressed in neurons of the CNS and the NB41A3 neuroblastoma cell line. CB(1) activation of NB41A3 cells by the synthetic cannabinoid, WIN55,212-2, is associated with an inhibition of Ca(2+) mobilization, leading to diminished nitric oxide synthase (NOS)-1 activity and the production of NO, in vitro. This ultimately results in antagonism of IFN-gamma-mediated antiviral activity and enhanced viral replication. Therefore, activation of cells expressing CB(1) by endogenous (or exogenous) ligands may contribute to decreased inflammation and to increased viral replication in neurons and disease in the CNS.

PIN: a novel protein involved in IFN-gamma accumulation of NOS-1 in neurons

In this study we investigate the role of the protein inhibitor of NOS-1 (PIN) in the interferon-gamma (IFN-gamma)-mediated posttranscriptional accumulation of nitric oxide synthase-1 (NOS-1) and the anti-vesicular stomatitis virus response in neuronal cells. IFN-gamma-induced enhancement of NOS-1 activity is crucial for its antiviral activity in the central nervous system. IFN-gamma treatment of neuronal cells results in an increase of total NOS-1 and decrease of total PIN proteins without alteration in their respective mRNA levels. PIN/NOS-1 complexes decreased after IFN-gamma treatment. Transfection of cells with small interfering RNA (siRNA) for PIN results in a higher constitutive activity of NOS-1 and inhibition of viral replication. IFN-gamma treatment did not change the amount of NOS-1 detectable by Western blot, when PIN is diminished by RNAi treatment. Overexpression of PIN results in lower constitutive NOS-1 expression and activity, and diminishes activation of NOS-1 by IFN-gamma. Our findings indicate that in neurons, IFN-gamma upregulates NOS-1 through proteasomal degradation of PIN.

Peripheral, but not central nervous system, type I interferon expression in mice in response to intranasal vesicular stomatitis virus infection

Type I interferon (IFN) is critical for resistance of mice to infection with vesicular stomatitis virus (VSV). Wild type (wt) VSV infection did not induce type I IFN production in vitro or in the central nervous system (CNS) of mice; however IFN-beta was detected in lungs, spleen, and serum within 24 h. The M protein mutant VSV, T1026R1 (also referred to as M51R), induced type I IFN production in vitro and in the CNS, with poor expression in spleens. In addition, VSV T1026R1 was not pathogenic to mice after intranasal infection, illustrating the importance of IFN in controlling VSV replication in the CNS. Experiments with chemical sympathectomy, sRAGE, and neutralizing antibody to VSV were performed to investigate the mechanism(s) utilized for induction of peripheral IFN; neither sRAGE infusion nor chemical sympathectomy had an effect on peripheral IFN production. In contrast, administration of neutralizing antibody (Ab) readily blocked the response. Infectious VSV was transiently present in lungs and spleens at 24 h post infection. The results are consistent with VSV traffic from the olfactory neuroepithelium to peripheral lymphoid organs hematogenously or via lymphatic circulation. These results suggest that VSV replicates to high titers in the brains of mice because of the lack of IFN production in the CNS after intranasal VSV infection. In contrast, replication of VSV in peripheral organs is controlled by the production of large amounts of IFN.

Gene expression contributing to recruitment of circulating cells in response to vesicular stomatitis virus infection of the CNS

During acute Vesicular Stomatitis Virus (VSV) infection of the mouse central nervous system, neutrophils, natural killer (NK) cells, macrophages, and CD4+ and CD8+ T cells are recruited from the circulation in response to chemokines and cytokines. This study elucidated the production of these factors and infiltration of these peripheral cells. Chemokines that were observed included CCL1, CXCL10 (IP-10), CCL5 (RANTES), CCL3 (MIP-1alpha), CCL4 (MIP-1beta), CXCL1 (MIP-2), CCL2 (MCP-1), and CCL11 (eotaxin). Cytokines produced in response to the infection include IL-1 and interferon-gamma, but not type I interferons. Neutrophils are the first recruited cell type, appearing as early as 24 h after intranasal application of the virus. NK cells follow, but T cells are not detected until 6 days postinfection.

The role of the proteasome-ubiquitin pathway in regulation of the IFN-gamma mediated anti-VSV response in neurons

Pharmacologic inhibition of the proteasome resulted in increased NOS-1 protein levels and increased NO production by neuronal cells. This correlated with an increased antiviral effect of IFN-gamma against the replication of vesicular stomatitis virus (VSV) replication in vitro. We also observed that a regulatory protein, Protein Inhibitor of NOS-1 (PIN) was down-regulated by IFN-gamma treatment, and more ubiquitinated PIN accumulated in IFN-gamma treated neurons. In cells of the reticuloendothelial system, IFN-gamma treatment induces the expression of a set of low molecular weight MHC-encoded proteins (LMPs), which replace the beta-subunit of the proteasome complex during the proteasome neosynthesis, resulting in a complex termed the immunoproteasome. LMP2, -7, and -10 were induced and the immunoproteasome was generated by IFN-gamma treatment in neuronal cells. Importantly, we observed that IFN-gamma induced inhibition of VSV protein synthesis was not dependent on ubiquitination.