The apicoplast link to fever-survival and artemisinin-resistance in the malaria parasite.

The emergence and spread of Plasmodium falciparum parasites resistant to front-line antimalarial artemisinin-combination therapies (ACT) threatens to erase the considerable gains against the disease of the last decade. Here, we develop a large-scale phenotypic screening pipeline and use it to carry out a large-scale forward-genetic phenotype screen in P. falciparum to identify genes allowing parasites to survive febrile temperatures. Screening identifies more than 200 P. falciparum mutants with differential responses to increased temperature. These mutants are more likely to be sensitive to artemisinin derivatives as well as to heightened oxidative stress. Major processes critical for P. falciparum tolerance to febrile temperatures and artemisinin include highly essential, conserved pathways associated with protein-folding, heat shock and proteasome-mediated degradation, and unexpectedly, isoprenoid biosynthesis, which originated from the ancestral genome of the parasite's algal endosymbiont-derived plastid, the apicoplast. Apicoplast-targeted genes in general are upregulated in response to heat shock, as are other Plasmodium genes with orthologs in plant and algal genomes. Plasmodium falciparum parasites appear to exploit their innate febrile-response mechanisms to mediate resistance to artemisinin. Both responses depend on endosymbiont-derived genes in the parasite's genome, suggesting a link to the evolutionary origins of Plasmodium parasites in free-living ancestors.

Epidemiologic, experimental, and clinical links between respiratory syncytial virus infection and asthma.

Virtually all children experience respiratory syncytial virus (RSV) infection at least once during the first 2 years of life, but only a few develop bronchiolitis and more severe disease requiring hospitalization, usually in the first 6 months of life. Children who recover from RSV-induced bronchiolitis are at increased risk for the development of recurrent wheeze and asthma in later childhood. Recent studies suggest that there is an association between RSV-induced bronchiolitis and asthma within the first decade of life but that this association is not significant after age 13. Despite the considerable progress made in our understanding of several aspects of respiratory viral infections, further work needs to be done to clarify the molecular mechanisms of early interactions between virus and host cell and the role of host gene products in the infection process. This review provides a critical appraisal of the literature in epidemiology and experimental research which links RSV infection to asthma. Studies to date demonstrate that there is a significant association between RSV infection and childhood asthma and that preventing severe primary RSV infections can decrease the risk of childhood asthma.

Abrogation of heat shock protein 70 induction as a strategy to increase antileukemia activity of heat shock protein 90 inhibitor 17-allylamino-demethoxy geldanamycin.

17-Allylamino-demethoxy geldanamycin (17-AAG) inhibits the chaperone association of heat shock protein 90 (hsp90) with the heat shock factor-1 (HSF-1), which induces the mRNA and protein levels of hsp70. Increased hsp70 levels inhibit death receptor and mitochondria-initiated signaling for apoptosis. Here, we show that ectopic overexpression of hsp70 in human acute myelogenous leukemia HL-60 cells (HL-60/hsp70) and high endogenous hsp70 levels in Bcr-Abl-expressing cultured CML-BC K562 cells confers resistance to 17-AAG-induced apoptosis. In HL-60/hsp70 cells, hsp70 was bound to Bax, inhibited 17-AAG-mediated Bax conformation change and mitochondrial localization, thereby inhibiting the mitochondria-initiated events of apoptosis. Treatment with 17-AAG attenuated the levels of phospho-AKT, AKT, and c-Raf but increased hsp70 levels to a similar extent in the control HL-60/Neo and HL-60/hsp70 cells. Pretreatment with 17-AAG, which induced hsp70, inhibited 1-beta-D-arabinofuranosylcytosine or etoposide-induced apoptosis in HL-60 cells. Stable transfection of a small interfering RNA (siRNA) to hsp70 completely abrogated the endogenous levels of hsp70 and blocked 17-AAG-mediated hsp70 induction, resulting in sensitizing K562/siRNA-hsp70 cells to 17-AAG-induced apoptosis. This was associated with decreased binding of Bax to hsp70 and increased 17-AAG-induced Bax conformation change. 17-AAG-mediated decline in the levels of AKT, c-Raf, and Bcr-Abl was similar in K562 and K562/siRNA-hsp70 cells. Cotreatment with KNK437, a benzylidine lactam inhibitor of hsp70 induction and thermotolerance, attenuated 17-AAG-mediated hsp70 induction and increased 17-AAG-induced apoptosis and loss of clonogenic survival of HL-60 cells. Collectively, these data indicate that induction of hsp70 attenuates the apoptotic effects of 17-AAG, and abrogation of hsp70 induction significantly enhances the antileukemia activity of 17-AAG.

A Multiple siRNA-Based Anti-HIV/SHIV Microbicide Shows Protection in Both In Vitro and In Vivo Models.

Human immunodeficiency virus (HIV) types 1 and 2 (HIV-1 and HIV-2) are the etiologic agents of AIDS. Most HIV-1 infected individuals worldwide are women, who acquire HIV infections during sexual contact. Blocking HIV mucosal transmission and local spread in the female lower genital tract is important in preventing infection and ultimately eliminating the pandemic. Microbicides work by destroying the microbes or preventing them from establishing an infection. Thus, a number of different types of microbicides are under investigation, however, the lack of their solubility and bioavailability, and toxicity has been major hurdles. Herein, we report the development of multifunctional chitosan-lipid nanocomplexes that can effectively deliver plasmids encoding siRNA(s) as microbicides without adverse effects and provide significant protection against HIV in both in vitro and in vivo models. Chitosan or chitosan-lipid (chlipid) was complexed with a cocktail of plasmids encoding HIV-1-specific siRNAs (psiRNAs) and evaluated for their efficacy in HEK-293 cells, PBMCs derived from nonhuman primates, 3-dimensional human vaginal ectocervical tissue (3D-VEC) model and also in non-human primate model. Moreover, prophylactic administration of the chlipid to deliver a psiRNA cocktail intravaginally with a cream formulation in a non-human primate model showed substantial reduction of SHIV (simian/human immunodeficiency virus SF162) viral titers. Taken together, these studies demonstrate the potential of chlipid-siRNA nanocomplexes as a potential genetic microbicide against HIV infections.

Respiratory syncytial virus (RSV) infection in elderly mice results in altered antiviral gene expression and enhanced pathology.

Elderly persons are more susceptible to RSV-induced pneumonia than young people, but the molecular mechanism underlying this susceptibility is not well understood. In this study, we used an aged mouse model of RSV-induced pneumonia to examine how aging alters the lung pathology, modulates antiviral gene expressions, and the production of inflammatory cytokines in response to RSV infection. Young (2-3 months) and aged (19-21 months) mice were intranasally infected with mucogenic or non-mucogenic RSV strains, lung histology was examined, and gene expression was analyzed. Upon infection with mucogenic strains of RSV, leukocyte infiltration in the airways was elevated and prolonged in aged mice compared to young mice. Minitab factorial analysis identified several antiviral genes that are influenced by age, infection, and a combination of both factors. The expression of five antiviral genes, including pro-inflammatory cytokines IL-1ß and osteopontin (OPN), was altered by both age and infection, while age was associated with the expression of 15 antiviral genes. Both kinetics and magnitude of antiviral gene expression were diminished as a result of older age. In addition to delays in cytokine signaling and pattern recognition receptor induction, we found TLR7/8 signaling to be impaired in alveolar macrophages in aged mice. In vivo, induction of IL-1ß and OPN were delayed but prolonged in aged mice upon RSV infection compared to young. In conclusion, this study demonstrates inherent differences in response to RSV infection in young vs. aged mice, accompanied by delayed antiviral gene induction and cytokine signaling.

Mucosal delivery of a double-stapled RSV peptide prevents nasopulmonary infection.

Respiratory syncytial virus (RSV) infection accounts for approximately 64 million cases of respiratory disease and 200,000 deaths worldwide each year, yet no broadly effective prophylactic or treatment regimen is available. RSV deploys paired, self-associating, heptad repeat domains of its fusion protein, RSV-F, to form a fusogenic 6-helix bundle that enables the virus to penetrate the host cell membrane. Here, we developed hydrocarbon double-stapled RSV fusion peptides that exhibit stabilized α-helical structure and striking proteolytic resistance. Pretreatment with double-stapled RSV peptides that specifically bound to the RSV fusion bundle inhibited infection by both laboratory and clinical RSV isolates in cells and murine infection models. Intranasal delivery of a lead double-stapled RSV peptide effectively prevented viral infection of the nares. A chitosan-based nanoparticle preparation markedly enhanced pulmonary delivery, further preventing progression of RSV infection to the lung. Thus, our results provide a strategy for inhibiting RSV infection by mucosal and endotracheal delivery of double-stapled RSV fusion peptides.

Nanotechnology Applications to HIV Vaccines and Microbicides.

Human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) remains one of the most serious threats to global health. Today there are no HIV vaccines which can prevent HIV infection. All of the candidates being studied are in the experimental stage. Preventive vaccine candidates are being tested in HIV-negative people to see if they can prevent infection. With of the development of a safe and effective vaccine still likely to be years away, topical microbicide formulations that are applied vaginally and rectally are receiving greater interest as an effective alternative to slow down the global spread of HIV. Current microbicide trials that aim to prevent the sexual transmission of HIV are using gels, creams, rings, films and there is also work underway to explore other types of 'delivery' systems. There have been numerous reports on safety and lack of toxicity of the application of nanotechnology for targeted delivery and slow, sustained release of drugs, proteins, peptides or nucleic acids by any route to maximize effectiveness and minimize adverse effects. The application of nanotechnology for targeting drugs and macromolecules to specific tissues or cells is one of the most important areas in nanomedicine research. Thus far nanoparticles provide a strong platform to combine protein and DNA based vaccines/microbicides and will facilitate the production, preclinical evaluation and clinical testing in the future.

Respiratory syncytial virus NS1 protein colocalizes with mitochondrial antiviral signaling protein MAVS following infection.

Respiratory syncytial virus (RSV) nonstructural protein 1(NS1) attenuates type-I interferon (IFN) production during RSV infection; however the precise role of RSV NS1 protein in orchestrating the early host-virus interaction during infection is poorly understood. Since NS1 constitutes the first RSV gene transcribed and the production of IFN depends upon RLR (RIG-I-like receptor) signaling, we reasoned that NS1 may interfere with this signaling. Herein, we report that NS1 is localized to mitochondria and binds to mitochondrial antiviral signaling protein (MAVS). Live-cell imaging of rgRSV-infected A549 human epithelial cells showed that RSV replication and transcription occurs in proximity to mitochondria. NS1 localization to mitochondria was directly visualized by confocal microscopy using a cell-permeable chemical probe for His(6)-NS1. Further, NS1 colocalization with MAVS in A549 cells infected with RSV was shown by confocal laser microscopy and immuno-electron microscopy. NS1 protein is present in the mitochondrial fraction and co-immunoprecipitates with MAVS in total cell lysatesof A549 cells transfected with the plasmid pNS1-Flag. By immunoprecipitation with anti-RIG-I antibody, RSV NS1 was shown to associate with MAVS at an early stage of RSV infection, and to disrupt MAVS interaction with RIG-I (retinoic acid inducible gene) and the downstream IFN antiviral and inflammatory response. Together, these results demonstrate that NS1 binds to MAVS and that this binding inhibits the MAVS-RIG-I interaction required for IFN production.

A small-molecule E2F inhibitor blocks growth in a melanoma culture model.

HLM006474 was identified using a computer-based virtual screen and the known crystal structure of the DNA-bound E2F4/DP2 heterodimer. Treatment of multiple cell lines with HLM006474 resulted in the loss of intracellular E2F4 DNA-binding activity as measured by electrophoretic mobility shift assay within hours. Overnight exposure to HLM006474 resulted in down-regulation of total E2F4 protein as well as known E2F targets. The effects of HLM006474 treatment on different cell lines varied but included a reduction in cell proliferation and an increase in apoptosis. HLM006474 induced apoptosis in a manner distinct from cisplatin and doxorubicin. E2F4-null mouse embryonic fibroblasts were less sensitive than wild-type counterparts to the apoptosis-inducing activity of the compound, revealing its biological specificity. A375 cells were extremely sensitive to the apoptosis-inducing activity of the compound in two-dimensional culture, and HLM006474 was a potent inhibitor of melanocytes proliferation and subsequent invasion in a three-dimensional tissue culture model system. Together, these results suggest that interference with E2F activity using small molecules may have clinical application in cancer therapy.

Infectious genomic RNA of Rhopalosiphum padi virus transcribed in vitro from a full-length cDNA clone.

Availability of a cloned genome from which infectious RNA can be transcribed is essential for investigating RNA virus molecular mechanisms. To date, no such clones have been reported for the Dicistroviridae, an emerging family of invertebrate viruses. Previously we demonstrated baculovirus-driven expression of a cloned Rhopalosiphum padi virus (RhPV; Dicistroviridae) genome that was infectious to aphids, and we identified a cell line (GWSS-Z10) from the glassy-winged sharpshooter, that supports RhPV replication. Here we report that RNA transcribed from a full-length cDNA clone is infectious. Transfection of GWSS-Z10 cells with the RhPV transcript resulted in cytopathic effects, ultrastructural changes, and accumulation of progeny virions, consistent with virus infection. Virions from transcript-infected cells were infectious in aphids. This infectious transcript of a cloned RhPV genome provides a valuable tool, and a more tractable system without interference from baculovirus infection, for investigating replication and pathogenesis of dicistroviruses.

A glassy-winged sharpshooter cell line supports replication of Rhopalosiphum padi virus (Dicistroviridae).

Rhopalosiphum padi virus (RhPV) (family Dicistroviridae; genus Cripavirus) is an icosahedral aphid virus with a 10kb positive-sense RNA genome. To study the molecular biology of RhPV, identification of a cell line that supports replication of the virus is essential. We screened nine cell lines derived from species within the Lepidoptera, Diptera and Hemiptera for susceptibility to RhPV following RNA transfection. We observed cytopathic effects (CPE) only in cell lines derived from hemipterans, specifically GWSS-Z10 cells derived from the glassy winged sharp shooter, Homalodisca coagulata and DMII-AM cells derived from the corn leaf hopper, Dalbulus maidis. Translation and appropriate processing of viral gene products, RNA replication and packaging of virus particles in the cytoplasm of GWSS-Z10 cells were examined by Western blot analysis, Northern blot hybridization and electron microscopy. Infectivity of the GWSS-Z10 cell derived-virus particles to the bird cherry-oat aphid, R. padi, was confirmed by RT-PCR and Western blot. The GWSS-Z10 cell line provides a valuable tool to investigate replication, structure and assembly of RhPV.

A baculovirus-expressed dicistrovirus that is infectious to aphids.

Detailed investigation of virus replication is facilitated by the construction of a full-length infectious clone of the viral genome. To date, this has not been achieved for members of the family Dicistroviridae. Here we demonstrate the construction of a baculovirus that expresses a dicistrovirus that is infectious in its natural host. We inserted a full-length cDNA clone of the genomic RNA of the dicistrovirus Rhopalosiphum padi virus (RhPV) into a baculovirus expression vector. Virus particles containing RhPV RNA accumulated in the nuclei of baculovirus-infected Sf21 cells expressing the recombinant RhPV clone. These virus particles were infectious in R. padi, a ubiquitous aphid vector of major cereal viruses. The recombinant virus was transmitted efficiently between aphids, despite the presence of 119 and 210 vector-derived bases that were stably maintained at the 5' and 3' ends, respectively, of the RhPV genome. The maintenance of such a nonviral sequence was surprising considering that most RNA viruses tolerate few nonviral bases beyond their natural termini. The use of a baculovirus to express a small RNA virus opens avenues for investigating replication of dicistroviruses and may allow large-scale production of these viruses for use as biopesticides.

Combined effects of novel tyrosine kinase inhibitor AMN107 and histone deacetylase inhibitor LBH589 against Bcr-Abl-expressing human leukemia cells.

AMN107 (Novartis Pharmaceuticals, Basel, Switzerland) has potent in vitro and in vivo activity against the unmutated and most common mutant forms of Bcr-Abl. Treatment with the histone deacetylase inhibitor LBH589 (Novartis) depletes Bcr-Abl levels. We determined the effects of AMN107 and/or LBH589 in Bcr-Abl-expressing human K562 and LAMA-84 cells, as well as in primary chronic myelogenous leukemia (CML) cells. AMN107 was more potent than imatinib mesylate (IM) in inhibiting Bcr-Abl tyrosine kinase (TK) activity and attenuating p-STAT5, p-AKT, Bcl-x(L), and c-Myc levels in K562 and LAMA-84 cells. Cotreatment with LBH589 and AMN107 exerted synergistic apoptotic effects with more attenuation of p-STAT5, p-ERK1/2, c-Myc, and Bcl-x(L) and increases in p27 and Bim levels. LBH589 attenuated Bcr-Abl levels and induced apoptosis of mouse pro-B BaF3 cells containing ectopic expression of Bcr-Abl or the IM-resistant, point-mutant Bcr-AblT315I and Bcr-AblE255K. Treatment with LBH589 also depleted Bcr-Abl levels and induced apoptosis of IM-resistant primary human CML cells, including those with expression of Bcr-AblT315I. As compared with either agent alone, cotreatment with AMN107 and LBH589 induced more loss of cell viability of primary IM-resistant CML cells. Thus, cotreatment with LBH589 and AMN107 is active against cultured or primary IM-resistant CML cells, including those with expression of Bcr-AblT315I.

Inhibition of histone deacetylase 6 acetylates and disrupts the chaperone function of heat shock protein 90: a novel basis for antileukemia activity of histone deacetylase inhibitors.

The hydroxamic acid (HAA) analogue pan-histone deacetylase (HDAC) inhibitors (HDIs) LAQ824 and LBH589 have been shown to induce acetylation and inhibit the ATP binding and chaperone function of heat shock protein (HSP) 90. This promotes the polyubiquitylation and degradation of the pro-growth and pro-survival client proteins Bcr-Abl, mutant FLT-3, c-Raf, and AKT in human leukemia cells. HDAC6 is a member of the class IIB HDACs. It is predominantly cytosolic, microtubule-associated alpha-tubulin deacetylase that is also known to promote aggresome inclusion of the misfolded polyubiquitylated proteins. Here we demonstrate that in the Bcr-abl oncogene expressing human leukemia K562 cells, HDAC6 can be co-immunoprecipitated with HSP90, and the knock-down of HDAC6 by its siRNA induced the acetylation of HSP90 and alpha-tubulin. Depletion of HDAC6 levels also inhibited the binding of HSP90 to ATP, reduced the chaperone association of HSP90 with its client proteins, e.g. Bcr-Abl, and induced polyubiquitylation and partial depletion of Bcr-Abl. Conversely, the ectopic overexpression of HDAC6 inhibited LAQ824-induced acetylation of HSP90 and alpha-tubulin and reduced LAQ824-mediated depletion of Bcr-Abl, AKT, and c-Raf. Collectively, these findings indicate that HDAC6 is also an HSP90 deacetylase. Targeted inhibition of HDAC6 leads to acetylation of HSP90 and disruption of its chaperone function, resulting in polyubiquitylation and depletion of pro-growth and pro-survival HSP90 client proteins including Bcr-Abl. Depletion of HDAC6 sensitized human leukemia cells to HAA-HDIs and proteasome inhibitors.