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At least 811 records · Page 45Linked to original sources
PubMed2007

Alpha-defensins block the early steps of HIV-1 infection: interference with the binding of gp120 to CD4.

Alpha-defensins are antibiotic peptides that act as natural inhibitors of HIV-1 infection. However, the mechanisms of such inhibition are still unclear. Here we demonstrate that alpha-defensins block the earliest steps in the viral infectious cycle, as documented using an HIV-1 envelope-mediated cell-fusion assay. A broad-spectrum inhibitory activity was observed on primary and laboratory-adapted HIV-1 isolates irrespective of their coreceptor specificity and genetic subtype. A primary mechanism of such inhibition was identified as the ability of alpha-defensins to bind specifically both to the primary HIV-1 cellular receptor, CD4, and to the viral envelope glycoprotein, gp120. Moreover, treatment of CD4+ T cells with alpha-defensins caused a dramatic downmodulation of CD4 expression. By monoclonal antibody competition, the regions of interaction with alpha-defensins were mapped to the D1 domain of CD4 and to a surface contiguous to the CD4- and coreceptor-binding sites of gp120. Consistent with these findings, alpha-defensins inhibited the binding of gp120 to CD4. These data demonstrate that alpha-defensins specifically block the initial phase of the HIV infectious cycle and modulate the expression of CD4, a critical receptor in the physiology of T-cell activation.

Binding Sites↗
PubMed2005

Inhibition of Henipavirus fusion and infection by heptad-derived peptides of the Nipah virus fusion glycoprotein.

BACKGROUND: The recent emergence of four new members of the paramyxovirus family has heightened the awareness of and re-energized research on new and emerging diseases. In particular, the high mortality and person to person transmission associated with the most recent Nipah virus outbreaks, as well as the very recent re-emergence of Hendra virus, has confirmed the importance of developing effective therapeutic interventions. We have previously shown that peptides corresponding to the C-terminal heptad repeat (HR-2) of the fusion envelope glycoprotein of Hendra virus and Nipah virus were potent inhibitors of both Hendra virus and Nipah virus-mediated membrane fusion using recombinant expression systems. In the current study, we have developed shorter, second generation HR-2 peptides which include a capped peptide via amidation and acetylation and two poly(ethylene glycol)-linked (PEGylated) peptides, one with the PEG moity at the C-terminus and the other at the N-terminus. Here, we have evaluated these peptides as well as the corresponding scrambled peptide controls in Nipah virus and Hendra virus-mediated membrane fusion and against infection by live virus in vitro. RESULTS: Unlike their predecessors, the second generation HR-2 peptides exhibited high solubility and improved synthesis yields. Importantly, both Nipah virus and Hendra virus-mediated fusion as well as live virus infection were potently inhibited by both capped and PEGylated peptides with IC50 concentrations similar to the original HR-2 peptides, whereas the scrambled modified peptides had no inhibitory effect. These data also indicate that these chemical modifications did not alter the functional properties of the peptides as inhibitors. CONCLUSION: Nipah virus and Hendra virus infection in vitro can be potently blocked by specific HR-2 peptides. The improved synthesis and solubility characteristics of the second generation HR-2 peptides will facilitate peptide synthesis for pre-clinical trial application in an animal model of Henipavirus infection. The applied chemical modifications are also predicted to increase the serum half-life in vivo and should increase the chance of success in the development of an effective antiviral therapy.

Animals↗
PubMed2000

Regulable expression of inhibin A in wild-type and inhibin alpha null mice.

Exogenous regulation of protein expression creates the potential to examine the consequences of homeostatic Dysregulation in many physiological systems and, when used in transgenic mice, provides the capability of restoring a gene product to its knockout background without antigenicity issues. In this study, we used a mifeprisone-inducible system (the GeneSwitch system) to regulate the expression of inhibin A from the liver of mice. Inhibin is a heterodimeric protein (alpha/beta) wherein one of its subunits (beta) is capable of homodimerizing to form its physiological antagonist, activin (beta/beta). Inhibin is also expressed in two forms, A and B, as determined by the subtype of beta-subunit that dimerizes with the alpha-subunit (alpha/betaA or alpha/betaB). To utilize the GeneSwitch system, transgenic transactivator mice with liver-specific expression of a mifepristone-activated chimeric nuclear receptor (GLVP) were crossed with transgenic target mice containing a GVLP-responsive promoter upstream of polio-virus IRES (internal ribosome entry site)-linked sequences coding for the alpha- and beta-subunits of inhibin A. This intercross produced "bigenic" mice capable of regulable expression of inhibin A from the liver. Overexpression of inhibin A in wild-type mice produced a phenotype wherein males had decreased testis size and females had a block in folliculogenesis at the early antral stage, findings similar to activin type IIA receptor (ActRIIA) null mice. These phenotypes were most likely due to suppressed serum FSH, confirming that the liver-derived inhibin A was secreted into the serum to down-regulate pituitary FSH levels. Furthermore, the generation of bigenic mice in the inhibin alpha null background allowed for the induction of inhibin A in inhibin alpha null male mice with subsequent rescue of these mice from their gonadal tumor-induced lethal phenotype. This work demonstrates the in vivo production of a heterodimeric hormone from a single inducible promoter to study its therapeutic and physiological effects. In addition, these studies are the first example of an inducible system being used to prevent a lethal knockout phenotype in an animal model.

Animals↗
PubMed2005

Effect of the infectious laryngotracheitis virus (ILTV) glycoprotein G on virus attachment, penetration, growth curve and direct cell-to-cell spread.

The secreted alphaherpesvirus glycoprotein G (gG) works differently from other proteins. Analysis of the role of ILTV gG in virus attachment, penetration, direct cell-to-cell spread (CTCS) and the growth curve showed that gG or its antibody had no effect on ILTV attachment and penetration and that the gG antibody reduced the virus plaque size and the one-step growth curve on chicken embryo liver (CEL) cells, but gG did not affect the virus plaque size or the one-step growth curve on CEL cells. Laser scanning confocal microscopy (LSCM) detection showed that ILTV gG is located in the perinuclear region and the membrane of the CEL cells. These results suggested that ILTV gG might contribute to direct cell-to-cell transmission.

Animals↗
PubMed2025

Enhanced RNA replication and pathogenesis in recent SARS-CoV-2 variants harboring the L260F mutation in NSP6.

The COVID-19 pandemic has been driven by SARS-CoV-2 variants with enhanced transmission and immune escape. Apart from extensive evolution in the Spike protein, non-Spike mutations are accumulating across the entire viral genome and their functional impact is not well understood. To address the contribution of these mutations, we reconstructed genomes of recent Omicron variants with disabled Spike expression (replicons) to systematically compare their RNA replication capabilities independently from Spike. We also used a single reference replicon and complemented it with various Omicron variant Spike proteins to quantify viral entry capabilities in single-round infection assays. Viral entry and RNA replication were negatively correlated, suggesting that as variants evolve reduced entry functions under growing immune pressure on Spike, RNA replication increases as a compensatory mechanism. We identified multiple mutations across the viral genome that enhanced viral RNA replication. NSP6 emerged as a hotspot with a distinct L260F mutation independently arising in the BQ.1.1 and XBB.1.16 variants. Using mutant and revertant NSP6 viral clones, the L260F mutation was validated to enhance viral replication in cells and increase pathogenesis in mice. Notably, this mutation reduced host lipid droplet content by NSP6. Collectively, a systematic analysis of RNA replication of recent Omicron variants defined NSP6's key role in viral RNA replication that provides insight into evolutionary trajectories of recent variants with possible therapeutic implications.

SARS-CoV-2↗
PubMed2026

Repurposing screens reveal a role for PKCη and NF1 in SARS-CoV-2 infection.

SARS-CoV-2 continues to circulate with the emergence of variants that evade existing immunity. However, all strains rely on conserved host factors for entry, making them attractive targets for host-directed antivirals. SARS-CoV-2 engages the ACE2 receptor and can enter cells through two alternative pathways depending on cell type: Spike cleavage at the plasma membrane by TMPRSS2, or within endocytic compartments by cathepsins. Cleavage triggers Spike-mediated membrane fusion and release of the viral genome. To discover small-molecule inhibitors of entry, we first screened compounds against live virus and active candidates were then tested using recombinant VSV expressing SARS-CoV-2 Spike, with VSV expressing its native glycoprotein serving as a control. This approach identified known and novel TMPRSS2 inhibitors, as well as Staurosporine and Retro-2.1. Both compounds inhibited infection in both TMPRSS2-dependent and -independent cell types. Entry bypass studies revealed that Staurosporine acts upstream of Spike cleavage, while Retro-2.1 functions downstream. Mechanistic studies in Calu-3 cells showed that Staurosporine, a pan-PKC inhibitor, blocks entry via PKCη, a pro-viral factor acting before Spike cleavage. Retro-2.1 targets NF1, which promotes infection downstream of Spike cleavage. Together, our screening pipeline identified inhibitors that block SARS-CoV-2 entry at distinct stages and revealed host factors that may inform the development of current and novel antiviral strategies.

Humans↗
PubMed2002

Regional status and approaches to control and eradication of foot and mouth disease in the Middle East and North Africa.

The Middle East is regarded as the region of the world most heavily affected by foot and mouth disease (FMD). The situation in the Middle East and North Africa constitutes a threat to other regions of the world, especially Europe. Risk management differs between North Africa and the Middle East due to different epidemiological situations. In the Middle East, the national cattle population is the principal target of preventive vaccination. Vaccination is used as a tool for preventing economic losses due to the disease, rather than as a means to prevent the spread of the infection. In North Africa, as FMD occurs almost cyclically, management is more focused on emergency preparedness and limitation of the spread of the disease upon diagnosis, as well as on effective control measures based on quarantine and mass vaccination. To reduce future outbreaks of FMD in the countries of the two regions, a common strategic programme should be adopted, based on effective regional co-operation at many levels. This should be complemented by efforts to restructure and consolidate the national Veterinary Services.

Africa, Northern↗
PubMed2006

Dissecting HIV fusion: identifying novel targets for entry inhibitors.

Significant momentum has been recently generated in understanding the HIV fusion process. This has led to the development of a host of HIV entry inhibitors which are currently in preclinical and/or clinical development or have been approved for clinical use. In this review we update our understanding of HIV fusion, specifically highlighting novel mechanisms and agents that inhibit this process. Major focus will be placed on three key areas. Initially viral attachment will be reviewed as recent developments in this field emphasize the importance of understanding cell type specific interactions with HIV. This has aided in identifying promising targets for the development of attachment inhibitors. Secondly, we will review the role of cellular lipids in HIV entry. Glycosphingolipids have been shown to interact with different components of the HIV fusion machinery and agents that perturb glycosphingolipid biosynthesis have inhibitory effects on HIV fusion. Likewise, manipulating ceramide biosynthesis also inhibits HIV fusion. Here, we describe how manipulating cellular lipids inhibits HIV fusion and how lipid biosynthesis can be modulated to potentially prevent HIV infection. We end this review by discussing the notion of targeting select host cell proteins for HIV therapy. We will review the role of the cellular proteins PDI, defensins and cytoskeletal proteins in facilitating the fusion reaction. As our understanding of the HIV fusion process increases, the identification of targets for developing entry inhibitors becomes more diverse. Given the rapid resistance of HIV to any selective pressure this is an important avenue in the advancement of drug therapy.

Actins↗
PubMed1999

[Gene therapy using anticancer drug-resistance genes].

Myelosuppression is a major dose-limiting factor in cancer chemotherapy. Introduction of drug-resistance genes into bone marrow cells of cancer patients has been proposed to overcome this limitation. In theory, any gene whose expression protects cells against the toxic effects of chemotherapy should be useful in vivo for this purpose. Among such genes, human multidrug-resistance gene (MDR1) has been studied most extensively for this purpose, and clinical trials of drug-resistance gene therapy have been started in the US for cancer patients who undergo high-dose chemotherapy with autologous hematopoietic stem cell transplantation. In Japan, our clinical protocol of MDR1 gene therapy "A clinical study of drug-resistance gene therapy to improve the efficacy and safety of chemotherapy against breast cancer" has been submitted to the government. To improve the efficacy and safety of this drug-resistance gene therapy, we have constructed a series of MDR1-bicistronic retrovirus vectors using a retrovirus backbone of Harvey murine sarcoma virus and internal ribosome entry site (IRES) from picornavirus to co-express a second gene with the MDR1 gene. MDR1-MGMT bicistronic vectors can be used to protect bone marrow cells of cancer patients from combination chemotherapy with MDR1-related anticancer agents and nitrosoureas. In addition, MDR1-bicistronic retrovirus vectors can be designed to use the MDR1 gene as an in vivo selectable marker to enrich the transduced cells which express therapeutic genes, if disease is curable by the expression of a single-peptide gene in any types of bone marrow cells or peripheral blood cells.

Bone Marrow Cells↗
PubMed1999

Overexpressed Human TNF Receptor-75 Can Independently Mediate hTNFalpha-induced Cytotoxicity in BHK-21 Cells.

A recombinant bicistronic expression vector was constructed containing human TNF receptor-75 gene and encephalomyocarditis virus(EMCV)internal ribosome entry site(IRES), followed by a neomycin phosphotransferase gene as selectable marker. BHK-21 cells were transfected with this vector using electroporation method and positive clones overexpressing the genes of interest were obtained after selection with G-418. The expression of two hTNFRs in those cells at RNA transcriptional and the protein translation levels had been proved by RT-PCR and indirect ELISA. It was found that the hTR75 could mediate cytotoxicity independently in BHK-21 cells after those cells were treated by hTNFalpha. Furthermore, hTR55 did not display the synergistic activity on this function of hTR75. These results put forward a new way for further studies on structure and function relationships of hTR75 and the interactions between two hTNFRs.

Journal Article↗
PubMedDate not supplied

[Virological and serological examination of wild birds during the spring migrations in the region of the Manych Reservoir, Rostov Province].

In accordance with the Soviet-American collaboration program on influenza and ARD, cooperative field studies were undertaken in 1975 in the USSR in order to test the field and laboratory methods for studies on influenza virus ecology. In the Rostov region of the USSR, virological and serological examinations of 321 birds of 25 species were carried out. Virological tests were performed with 678 biological specimens and in various serological tests 308 blood serum specimesn from wild birds were examined. Examinations of specimens of washings and organs of birds revealed no hemagglutinating agents. The paper presents the results of studies of avian blood serum specimens in the HI test, neuraminidase activity inhibition test and the immunodiffusion test.

Animal Population Groups↗
PubMed1992

Suspected buttercup (Ranunculus bulbosus) toxicosis with secondary photosensitization in a Charolais heifer.

A presumptive diagnosis of buttercup toxicosis with photosensitization secondary to hepatotoxicity was made in an 18-mo-old Charolais heifer. The differential diagnosis included salmonellosis, aflatoxicosis, bovine virus diarrhea, internal parasite infestation, and plant toxicosis with either primary or secondary photosensitization. All these possibilities were excluded except buttercup toxicosis with photosensitization secondary to hepatotoxicity. While this diagnosis was not absolutely confirmed, it was the most likely cause of the disease and raised the intriguing possibility that protoanemonin, buttercup's toxic principle, is hepatotoxic.

Animals↗