Vif counteracts a cyclophilin A-imposed inhibition of simian immunodeficiency viruses in human cells

Vif is a primate lentiviral accessory protein that is crucial for viral infectivity. Vif counteracts the antiviral activity of host deaminases such as APOBEC3G and APOBEC3F. We now report a novel function of African green monkey simian immunodeficiency virus (SIVagm) Vif that promotes replication of SIVagm in human cells lacking detectable deaminase activity. We found that cyclophilin A (CypA) was excluded from wild-type SIV particles but was efficiently packaged into vif-deficient SIVagm virions. The presence of CypA in vif-defective SIVagm was correlated with reduced viral replication. Infection of CypA knockout Jurkat cells or treatment of Jurkat cells with cyclosporine A eliminated the Vif-sensitive inhibition and resulted in replication profiles that were similar for wild-type and vif-deficient SIVagm. Importantly, the inhibitory effect of CypA was restricted to virus-producing cells and was TRIM5alpha independent. The abilities of SIVagm Vif to inhibit encapsidation of CypA and to increase viral infectivity were shared by rhesus macaque SIV Vif and thus seem to be general properties of SIV Vif proteins. Exclusion of CypA from SIVagm particles was not associated with intracellular degradation, suggesting a mode of Vif action distinct from that proposed for APOBEC3G. This is the first report of a novel vif-sensitive antiviral activity of human CypA that may limit zoonotic transmission of SIV and the first demonstration of CypA encapsidation into a virus other than human immunodeficiency virus type 1.     

Liquid chromatographic assay of abouthiouzine in plasma and its application to pharmacokinetic studies

Abouthiouzine is a newly synthesized antithyroid agent with a proposed less adverse effects profile than other currently used drugs. A simple and rapid reversed phase high performance liquid chromatography assay was developed to determine the concentration of abouthiouzine in human plasma. The procedure involved extraction of the drug and propranolol (internal standard) from the plasma using ethylacetate. The extract was evaporated under nitrogen and the residue was constituted with the mobile phase and injected onto micro-Bondapack phenyl column (10 microm, 3.9 mm x 150 mm). The mobile phase consisted of 10 mM potassium dihydrogen phosphate buffer, acetonitrile, and methanol in the ratio of 60:25:15 (v/v/v, pH=3.0), which was delivered at a rate of 1.5 ml/min. Abouthiouzine and the internal standard were monitored using UV detection at 240 nm; the run time was less than 5 min. The detection limit of abouthiouzine is 0.5 microg/ml. The within- and between-day coefficients of variation were less than 7%. Our method has been successfully used to measure abouthiouzine plasma concentrations in a rabbit model following an intravenous administration of the drug.     

Human Rhinovirus 14 Enters Rhabdomyosarcoma Cells Expressing ICAM-1 by a Clathrin-, Caveolin-, and Flotillin-Independent Pathway

Intercellular adhesion molecule 1 (ICAM-1) mediates binding and entry of major group human rhinoviruses (HRVs). Whereas the entry pathway of minor group HRVs has been studied in detail and is comparatively well understood, the pathway taken by major group HRVs is largely unknown. Use of immunofluorescence microscopy, colocalization with specific endocytic markers, dominant negative mutants, and pharmacological inhibitors allowed us to demonstrate that the major group virus HRV14 enters rhabdomyosarcoma cells transfected to express human ICAM-1 in a clathrin-, caveolin-, and flotillin-independent manner. Electron microscopy revealed that many virions accumulated in long tubular structures, easily distinguishable from clathrin-coated pits and caveolae. Virus entry was strongly sensitive to the Na⁺/H⁺ ion exchange inhibitor amiloride and moderately sensitive to cytochalasin D. Thus, cellular uptake of HRV14 occurs via a pathway exhibiting some, but not all, characteristics of macropinocytosis and is similar to that recently described for adenovirus 3 entry via α_v integrin/CD46 in HeLa cells.Human rhinoviruses (HRVs), members of the family Picornaviridae that represent a major cause of the common cold, essentially utilize two different receptor types for host cell attachment. The 12 minor group HRVs, exemplified by HRV2, bind low-density lipoprotein receptor (LDLR), LDLR-related protein (LRP) (20), and very-LDLR (VLDLR) (29) and are internalized via the well-characterized clathrin-dependent endocytic pathway (44); however, these ligands, like others, can switch to different entry portals when the clathrin-dependent pathway is blocked (4). Once the virus arrives in endosomal carrier vesicles or late endosomes, uncoating (i.e., the release of the viral RNA genome) is triggered by the acidic pH (35, 39).The 87 major group HRVs, exemplified by HRV14, bind intercellular adhesion molecule-1 (ICAM-1). Following entry, uncoating is triggered by ICAM-1 itself (3), but the low endosomal pH facilitates this process (37). Based on inhibition of infection by the dominant negative (DN) dynamin-2 mutant dyn^K44A, it was proposed that HRV14 also follows a clathrin-dependent pathway in HeLa-H1 cells (9). However, ICAM-1 lacks a clathrin localization signal and even functions as a viral receptor when its cytoplasmic tail is replaced with a glycosylphosphatidylinositol (GPI) anchor (45). Furthermore, dynamin has also been shown to be involved in pathways other than clathrin-mediated endocytosis (CME), such as caveolae- and lipid raft-dependent entry, as a function of ligand and cell type (reviewed in references 30 and 34). Additionally, dynamin might play a role in formation and closure of circular pinocytic ruffles (31). More recently, a specific entry pathway for ICAM-1 ligands into human umbilical vein endothelial cells was identified and termed “cam-mediated endocytosis”; uptake was found to be triggered upon binding of multivalent ligands, such as immunoconjugates and immunobeads, and to occur independently from clathrin and caveolin. Inhibition by amiloride, actin depolymerization, and protein kinase C inhibitors pointed to macropinocytosis (33). So far, it is not known whether these findings are relevant to the entry pathway of HRVs via ICAM-1 as the uptake kinetics was significantly dependent on particle size. For all these reasons, involvement of clathrin in HRV14 uptake is questionable. Accordingly, we explored entry of HRV14 via ICAM-1 and compared the results with the well-characterized clathrin-dependent entry pathway of HRV2 (44). Employing pharmacological compounds, specific DN inhibitors, immunofluorescence, and electron microscopy, we demonstrate that HRV14 enters rhabdomyosarcoma ICAM-1-expressing (RD-ICAM) cells via a pathway independent of clathrin, caveolin, and flotillin.     

Head-to-Head Comparison of Soluble vs. Qβ VLP Circumsporozoite Protein Vaccines Reveals Selective Enhancement of NANP Repeat Responses

Circumsporozoite protein (CSP) of Plasmodium falciparum is a promising malaria vaccine target. RTS,S, the most advanced malaria vaccine candidate consists of the central NANP repeat and carboxy-terminal region of CSP displayed on a hepatitis B virus-like particle (VLP). To build upon the success of RTS,S, we produced a near full-length Plasmodium falciparum CSP that also includes the conserved amino-terminal region of CSP. We recently showed that this soluble CSP, combined with a synthetic Toll-like-receptor-4 (TLR4) agonist in stable oil-in-water emulsion (GLA/SE), induces a potent and protective immune response in mice against transgenic parasite challenge. Here we have investigated whether the immunogenicity of soluble CSP could be further augmented by presentation on a VLP. Bacteriophage Qβ VLPs can be readily produced in E.coli, they have a diameter of 25 nm and contain packaged E. coli RNA which serves as a built in adjuvant through the activation of TLR7/8. CSP was chemically conjugated to Qβ and the CSP-Qβ vaccine immunogenicity and efficacy were compared to adjuvanted soluble CSP in the C57Bl/6 mouse model. When formulated with adjuvants lacking a TLR4 agonist (Alum, SE and Montanide) the Qβ-CSP induced higher anti-NANP repeat titers, higher levels of cytophilic IgG2b/c antibodies and a trend towards higher protection against transgenic parasite challenge as compared to soluble CSP formulated in the same adjuvant. The VLP and soluble CSP immunogenicity difference was most pronounced at low antigen dose, and within the CSP molecule, the titers against the NANP repeats were preferentially enhanced by Qβ presentation. While a TLR4 agonist enhanced the immunogenicity of soluble CSP to levels comparable to the VLP vaccine, the TLR4 agonist did not further improve the immunogenicity of the Qβ-CSP vaccine. The data presented here pave the way for further improvement in the Qβ conjugation chemistry and evaluation of both the Qβ-CSP and soluble CSP vaccines in the non-human primate model.     

Effect of temperature on the biology of Creontiades dilutus (Stål) (Heteroptera: Miridae)

The egg and nymphal development, fecundity and survival of the green mirid, Creontiades dilutus were examined at a range of temperatures and a modified day-degree model fitted to the data. Day degree (DD) requirements for egg and nymphal development, and threshold temperatures were calculated from the fitted lines. Female fecundity and longevity, egg and nymphal development, and survival of C. dilutus were significantly influenced by temperature. Eggs and nymphs failed to complete development at temperatures below 17 and at 38°C. Females also failed to produce any eggs at 11 and 38°C. The optimum temperature range for female fecundity was found to be 26–32°C. The optimum temperature for the development of eggs was calculated from the model as 30.5°C and for nymphs as 31.5°C. The threshold temperature for development was 15.8°C for egg and 15.1°C for nymph; 69.4 and 156.7 DD were required for completing the egg and the nymphal development, respectively. At the optimum temperature, it was estimated that development from egg to adult took 15 days. Survival was highest at 26°C for eggs and at 30–32°C for nymphs.     

Cleavage of single-stranded DNA by plasmid pT181-encoded RepC protein.

RepC protein encoded by plasmid pT181 has single-stranded endonuclease and topoisomerase-like activities. These activities may be involved in the initiation (and termination) of pT181 replication by a rolling circle mechanism. RepC protein cleaves the bottom strand of DNA within the origin of replication at a single, specific site when the DNA is in the supercoiled or linear (double or single-stranded) form. We have found that RepC protein will also cleave single-stranded DNA at sites other than the origin of replication. We have mapped the secondary cleavage sites on pT181 DNA. When the DNA is in the supercoiled, or linear, double-stranded form, only the primary site within the origin is cleaved. However, when the DNA is present in the single-stranded form, several strong and weak cleavage sites are observed. The DNA sequence at these cleavage sites shows a strong similarity with the primary cleavage site. The presence of Escherichia coli SSB protein inhibited cleavage at all of the secondary nick sites while the primary nick site remained susceptible to cleavage.     

Evaluation of accuracy and applicability of protein models: retrospective analysis of biological and biomedical predictions

In order to study protein function and activity structural data is required. Since experimental structures are available for just a small fraction of all known protein sequences, computational methods such as protein modelling can provide useful information. Over the last few decades we have predicted, with homology modelling methods, the structures for numerous proteins. In this study we assess the structural quality and validity of the biological and medical interpretations and predictions made based on the models. All the models had correct scaffolding and were ranked at least as correct or good by numerical evaluators even though the sequence identity with the template was as low as 8%. The biological explanations made based on models were well in line with experimental structures and other experimental studies. Retrospective analysis of homology models indicates the power of protein modelling when made carefully from sequence alignment to model building and refinement. Modelling can be applied to studying and predicting different kinds of biological phenomena and according to our results it can be done so with success.     

Targeting of specific domains of diphtheria toxin by site-directed antibodies.

Antibodies highly selective for two functionally distinct regions of diphtheria toxin (DTx) were prepared using synthetic peptide conjugates as immunogens. Three peptides were selected for synthesis: sequence DTx141-157 on fragment A, which contains the putative protein elongation factor (EF-2) ADP-ribosyltransferase site; DTx224-237 on fragment B, selected on the basis of forming a predicted surface loop; and DTx513-526 on fragment B, forming a part of the region containing the putative receptor binding domain. All of the anti-peptide antibodies recognized the corresponding peptide, and also reacted with the toxin, specifically with the fragment containing the sequence against which they were raised, confirming the utility of this approach in generating fragment-specific antibodies. The anti-peptide antibody with the highest binding titre both to the peptide and to the native toxin was the one prepared against the sequence with the highest surface and loop likelihood indices of the three peptides selected. The similarity of the reactivity profiles with peptide and native and denatured toxin is consistent with the prediction that the region selected occurs in a surface loop and that the structure of the peptide is similar to the conformation of this region in the native protein. The epitopes for two of the anti-peptide antibodies were mapped. The results indicated that even though the antisera were raised to peptides containing 14 amino acids (aa) they were directed predominantly against a narrow region within the peptide, consisting of only 5-6 aa residues.(ABSTRACT TRUNCATED AT 250 WORDS)     

Assessment of Maturity,Reproduction and Reproductive Potentials of Torpedo Scad, <Emphasis Type="Italic">Megalaspis cordyla</Emphasis> (Linnaeus, 1758) from Northern Arabian Sea Coast of Pakistan

Port landing specimens of torpedo scad, Megalaspis cordyla were collected at monthly intervals from August 2013 to June 2014 from the northern Arabian Sea coast of Pakistan. The life history characteristics revealed that torpedo scad has a prolonged breeding season which occurred with two peaks: from May to June and from November to February. The spawning seasonality was also validated with microscopic gonad examination.The highest GSI value was noted in May and January whereas the lowest in November was recorded for both sexes. The age at which individuals of both sexes become 50% mature (t₅₀) was estimated as 2.44 year. Life span (t_max) calculated as 3.96 years for male and females. The size of 270 and 265 mm at which 50% individuals attained sexual maturity (L₅₀) was determined for males and females respectively. The reproductive potential (fecundity)was made from ten ripe females ranged from 29–43.8 cm TL and weighing 220–540 g of IV–V developmental stage was enumerated as 32306–236677 eggs (CV = 2.135) with an average number of eggs 86544 counted per ripe female/season. This study contains fundamental data of an important fish species in the northern Arabian Sea coast of Pakistan. It provides vital information to the fisheries managers for implementation on sustainable use of the resource during spawning season.