A colorimetric-based accurate method for the determination of enterovirus 71 titer

Stability and infectivity of enteroviruses on dry surfaces: Potential for indirect transmission control

Hand, foot, and mouth disease (HFMD) is a contagious disease mainly occurring in young children, and outbreaks commonly occur among young children in the Asia-Pacific region including Thailand. Moreover, the World Health Organization (WHO) monitors HFMD in the Western Pacific region to detect outbreaks and other significant events by the Regional Event Based Surveillance System. HFMD is mainly caused by a group of enteroviruses (EVs) transmitted through direct contact (person to person) and indirect contact with contaminated objects (surface-to-hand). However, few studies have examined the surface stability of EVs. In this study, we investigated the stability of enterovirus A71 (EV-A71) and coxsackievirus A16 (CVA16) on three different dry surfaces (wood, plastic, and stainless steel) using the endpoint titration using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) staining of viable cells and real-time polymerase chain reaction (viral genome detection). The results revealed that virus infectivity dramatically decreased within a few hours on dry surfaces. However, viral RNA could be detected on dry surfaces for up to 28 days. Concerning heat inactivation, both EV-A71 and CVA16 were inactivated after exposure to 60°C for 15 min. Information on virus stability on different dry surfaces will provide useful information for HFMD transmission control.

Improvement of Precision in Recombinant Adeno-Associated Virus Infectious Titer Assay with Droplet Digital PCR as an Endpoint Measurement

Recombinant adeno-associated virus (rAAV) has been utilized successfully for in vivo gene delivery for treatment of a variety of human diseases. To sustain the growth of recombinant AAV gene therapy products, there is a critical need for the development of accurate and robust analytical methods. Fifty percent tissue culture infectious dose (TCID50) assay is an in vitro cell-based method widely used to determine AAV infectivity, and this assay is historically viewed as a challenge due to its high variability. Currently, quantitative PCR (qPCR) serves as the endpoint method to detect the amount of replicated viral genome after infection. In this study, we optimize the TCID50 assay by adapting endpoint detection with droplet digital PCR (ddPCR). We performed TCID50 assays using ATCC AAV-2 reference standard stock material across 18 independent runs. The cell lysate from TCID50 assay was then analyzed using both qPCR and ddPCR endpoint to allow for direct comparison between the two methods. The long-term 1-year side-by-side comparison between qPCR and ddPCR as endpoint measurement demonstrated improved interassay precision when the ddPCR method was utilized. In particular, after the addition of a novel secondary set threshold for infectivity scoring of individual wells, the average infectious titer of 18 runs is 6.45E+08 with % coefficient of variation (CV) of 42.5 and 5.63E+08 with % CV of 34.9 by qPCR and ddPCR, respectively. In this study, we offer improvements of infectious titer assay with (1) higher interassay precision by adapting ddPCR as an endpoint method without the need of standard curve preparation; (2) identification of a second "set threshold" value in infectivity scoring that improves assay precision; and (3) application of statistical analysis to identify the acceptance range of infectious titer values. Taken together, we provide an optimized TCID50 method with improved interassay precision that is important for rAAV infectious titer testing during process development and manufacturing.

Analysis of ICAM-1 Expression on Bladder Carcinoma Cell Lines and Infectivity and Oncolysis by Coxsackie Virus A21

Oncolytic viruses are biological agents which can easily be delivered at high doses directly to the bladder through a catheter (intravesical), with low risk of systemic uptake and toxicity. To date, a number of viruses have been delivered intravesically in patients and in murine models with bladder cancer and antitumour effects demonstrated. Here, we describe in vitro methods to evaluate Coxsackie virus, CVA21, as an oncolytic virus for the treatment of human bladder cancer by determining the susceptibility of bladder cancer cell lines expressing differing levels of ICAM-1 surface receptor to CVA21.

Inhibition of MEK-ERK pathway enhances oncolytic vaccinia virus replication in doxorubicin-resistant ovarian cancer

Oncolytic vaccinia virus (OVV) has been reported to induce cell death in various types of cancer; however, the oncolytic activity of OVV in drug-resistant ovarian cancer remains limited. In the present study, we established doxorubicin-resistant ovarian cancer cells (A2780-R) from the A2780 human ovarian cancer cell line. Both A2780 and A2780-R cells were infected with OVV to explore its anticancer effects. Interestingly, OVV-infected A2780-R cells showed reduced viral replication and cell death compared with A2780 cells, suggesting their resistance against OVV-induced oncolysis; to understand the mechanism underlying this resistance, we explored the involvement of protein kinases. Among protein kinase inhibitors, PD0325901, an MEK inhibitor, significantly augmented OVV replication and cell death in A2780-R cells. PD0325901 treatment increased the phosphorylation of STAT3 in A2780-R cells. Moreover, cryptotanshinone, a STAT3 inhibitor, abrogated PD0325901-stimulated OVV replication. Furthermore, trametinib, a clinically approved MEK inhibitor, increased OVV replication in A2780-R cells. Transcriptomic analysis showed that the MEK inhibitor promoted OVV replication via increasing STAT3 activation and downregulating the cytosolic DNA-sensing pathway. Combined treatment with OVV and trametinib attenuated A2780-R xenograft tumor growth. These results suggest that pharmacological inhibition of MEK reinforces the oncolytic efficacy of OVV in drug-resistant ovarian cancer.

Systemic Neutralizing Antibodies and Local Immune Responses Are Critical for the Control of SARS-CoV-2

Antibody measurements are primarily used to evaluate experimental and approved COVID-19 vaccines, which is unilateral considering our immune responses’ complex nature. Previously, we showed that nanoparticle plasmid DNA adjuvant system, QAC, and MVA based vaccines were immunogenic against SARS-CoV-2. Here, we report on the protective efficacy of systemic humoral and mucosal cell-mediated immune responses in transgenic mice models against SARS-CoV-2 following nanoparticle immunization. Parenteral, intramuscular administration of QAC-based plasmid DNA vaccine-encoding SARS-CoV-2 S and N led to the induction of significant serum neutralizing humoral responses, which reduced viral burden in the lungs and prevented viral dissemination to the brain. In contrast, the mucosal, intranasal administration of a heterologous vaccine elicited significant mucosal cell-mediated immune responses in the lungs that limited lung viral replication. The presented results demonstrate that serum neutralizing humoral and local lung T-cell immune responses are critical for the control of SARS-CoV-2 replication.

Quantification of Infectious SARS-CoV-2 by the 50% Tissue Culture Infectious Dose Endpoint Dilution Assay

A number of viral quantification methods are used to measure the concentration of infectious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While the traditional plaque-based assay allows for direct enumeration of replication competent lytic virions and remains the gold standard for the quantification of infectious virus, the 50% tissue culture infectious dose (TCID₅₀) endpoint dilution assay allows for a more rapid, large-scale analysis of experimental samples. In this chapter, we describe a well-established TCID₅₀ assay protocol to measure the SARS-CoV-2 infectious titer in viral stocks, in vitro cell or organoid models, and animal tissue. We also present alternative assays for scoring the cytopathic effect of SARS-CoV-2 in cell culture and comparable methods to calculate the 50% endpoint by serial dilution.

Multiplexed VaxArray immunoassay for rapid antigen quantification in measles and rubella vaccine manufacturing

Measles-containing vaccines (MCV), specifically vaccines against measles and rubella (MR), are extremely effective and critical for the eradication of measles and rubella diseases. In developed countries, vaccination rates are high and vaccines are readily available, but continued high prevalence of both diseases in developing countries and surges in measles deaths in recent years have highlighted the need to expand vaccination efforts. To meet demand for additional vaccines at a globally affordable price, it is highly desirable to streamline vaccine production thereby reducing cost and speeding up time to delivery. MR vaccine characterization currently relies on the 50% cell culture infectious dose (CCID₅₀) assay, an endpoint assay with low reproducibility that requires 10–14 days to complete. For streamlining bioprocess analysis and improving measurement precision relative to CCID₅₀, we developed the VaxArray Measles and Rubella assay kit, which is based on a multiplexed microarray immunoassay with a 5-hour time to result. Here we demonstrate vaccine-relevant sensitivity ranging from 345 to 800 IFU/mL up to 100,000 IFU/mL (infectious units per mL) and specificity that allows simultaneous analysis in bivalent vaccine samples. The assay is sensitive to antigen stability and has minimal interference from common vaccine additives. The assay exhibits high reproducibility and repeatability, with 15% CV, much lower than the typical 0.3 log₁₀ error (∼65%) observed for the CCID₅₀ assay. The intact protein concentration measured by VaxArray is reasonably correlated to, but not equivalent to, CCID₅₀ infectivity measurements for harvest samples. However, the measured protein concentration exhibits equivalency to CCID₅₀ for more purified samples, including concentrated virus pools and monovalent bulks, making the assay a useful new tool for same-day analysis of vaccine samples for bioprocess development, optimization, and monitoring.

Methods in Screening Antiviral Drugs Against Enterovirus 71

Enteroviruses 71 (EV71) is a single-stranded, neurotrophic RNA virus responsible for the numerous outbreaks of hand, foot, and mouth disease (HFMD) in the Asia-Pacific regions. HFMD primarily affects children to cause range of infection, from mild symptoms to acute flaccid paralysis, and hemorrhage. Despite increased incidence of EV71 epidemics globally and research against EV71 becoming prioritized, no antiviral agent against EV71 has yet been licensed and approved worldwide. In this chapter, detailed EV71 antiviral screening techniques are described, including plaque assay which determines viral titers through the use of a semisolid overlay, carboxymethyl cellulose to allow even viral spread and infection across the host cellular monolayers as well as a crystal violet, a distinct counterstain to visualize circular regions of infectious zones-plaques. qRT-PCR is used to quantify the viral genomic RNA in the infected samples and MTS cell viability assay to quantify the cell viability after infection or toxicity of the compound on the cells. Furthermore, various antiviral inhibition assays including prophylactic, post infection, and virucidal assays are demonstrated for estimation of the antiviral activity of potential antiviral drugs against EV71. These methods can be effectively utilized in virology laboratories for effective high-throughput screening of antiviral molecules against EV71 that can assist in the future development of antiviral drugs.

Efficacy of Mouth Rinses Against SARS-CoV-2: A Scoping Review

Introduction:The presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in saliva and nasopharyngeal secretions has challenged the routine practice of dentistry. Use of preprocedural mouth rinses has been recommended by several organizations to potentially reduce the transmission of SARS-CoV-2. This scoping review aimed at evaluating the available evidence on the efficacy of mouth rinses against SARS-CoV-2.

Methods:A thorough literature search on electronic databases (PubMed, Scopus, and Google Scholar) was performed by two independent reviewers and data from articles addressing the aim of this article were extracted.

Results:After exclusion of articles not addressing the end point in question, 12 articles were included in this scoping review. Of the 12 articles, seven werein vitrostudies and five werein vivohuman clinical studies. Thein vitrostudies used a standardized methodology (endpoint dilution assay) to evaluate the efficacy of antimicrobial mouth rinses against SARS-CoV-2. Thein vivostudies were done utilizing polymerase chain reaction assay of samples obtained from saliva or nasopharyngeal swab or a combination of both nasopharyngeal and oropharyngeal swab. The reagents tested in these studies included povidone-iodine, chlorhexidine, hydrogen peroxide (H2O2), essential oils, and quaternary ammonium compounds and demonstrated varied efficacy against SARS-CoV-2.

Conclusion:Based on the available evidence fromin vitrostudies, it can be concluded that mouth rinses have a potential to reduce SARS-CoV-2 viral load; however, effectiveness inin vivoconditions is still inconclusive. Owing to the substantial heterogeneity in reporting of the anti–SARS-CoV-2 efficacy of mouth rinses, this review highlights the need to conduct future research with robust and standardized methodologies to confirm effectiveness of mouth rinses.

Modulation of IGF2 Expression in the Murine Thymus and Thymic Epithelial Cells Following Coxsackievirus-B4 Infection

Coxsackievirus B4 (CV-B4) can infect human and murine thymic epithelial cells (TECs). In a murine TEC cell line, CV-B4 can downregulate the transcription of the insulin-like growth factor 2 (Igf2) gene coding for the self-peptide of the insulin family. In this study, we show that CV-B4 infections of a murine TEC cell line decreased Igf2 P3 promoter activity by targeting a region near the transcription start site; however, the stability of Igf2 transcripts remained unchanged, indicating a regulation of Igf2 transcription. Furthermore, CV-B4 infections decreased STAT3 phosphorylation in vitro. We also showed that mice infected with CV-B4 had an altered expression of Igf2 isoforms as detected in TECs, followed by a decrease in the pro-IGF2 precursor in the thymus. Our study sheds new light on the intrathymic regulation of Igf2 transcription during CV-B4 infections and supports the hypothesis that a viral infection can disrupt central self-tolerance to insulin by decreasing Igf2 transcription in the thymic epithelium.

Comparative Transcriptome Profiling of Human and Pig Intestinal Epithelial Cells after Porcine Deltacoronavirus Infection

Porcine deltacoronavirus (PDCoV) is an emerging infectious disease of swine with zoonotic potential. Phylogenetic analysis suggests that PDCoV originated recently from a host-switching event between birds and mammals. Little is known about how PDCoV interacts with its differing hosts. Human-derived cell lines are susceptible to PDCoV infection. Herein, we compare the gene expression profiles of an established host swine cells to potential emerging host human cells after infection with PDCoV. Cell lines derived from intestinal lineages were used to reproduce the primary sites of viral infection in the host. Porcine intestinal epithelial cells (IPEC-J2) and human intestinal epithelial cells (HIEC) were infected with PDCoV. RNA-sequencing was performed on total RNA extracted from infected cells. Human cells exhibited a more pronounced response to PDCoV infection in comparison to porcine cells with more differentially expressed genes (DEGs) in human, 7486, in comparison to pig cells, 1134. On the transcriptional level, the adoptive host human cells exhibited more DEGs in response to PDCoV infection in comparison to the primary pig host cells, where different types of cytokines can control PDCoV replication and virus production. Key immune-associated DEGs and signaling pathways are shared between human and pig cells during PDCoV infection. These included genes related to the NF-kappa-B transcription factor family, the interferon (IFN) family, the protein-kinase family, and signaling pathways such as the apoptosis signaling pathway, JAK-STAT signaling pathway, inflammation/cytokine–cytokine receptor signaling pathway. MAP4K4 was unique in up-regulated DEGs in humans in the apoptosis signaling pathway. While similarities exist between human and pig cells in many pathways, our research suggests that the adaptation of PDCoV to the porcine host required the ability to down-regulate many response pathways including the interferon pathway. Our findings provide an important foundation that contributes to an understanding of the mechanisms of PDCoV infection across different hosts. To our knowledge, this is the first report of transcriptome analysis of human cells infected by PDCoV.

Impact of dextran sulfate in culture media on titration of vesicular stomatitis virus

Viral vectors derived from vesicular stomatitis virus (VSV) are important vectors for the development of vaccines and for the treatment of cancer. The efficiency of therapy based on VSV is dependent on the dose of virus used. Therefore it is essential to measure accurately and reproducibly the amount of functional vectors in the samples to be tested. Two common methods used to measure the titer of VSV are TCID_50% and plaque assay. In the current study, we compared these two titration methods by using a recombinant VSV expressing the green fluorescent protein (VSV-GFP) as a model virus. Some culture media developed for suspension mammalian cells contain dextran sulfate. We observed that plaque assay, but not TCID_50%, can underestimate the virus titer up to 10 fold when VSV-GFP was produced in culture media containing dextran sulfate. Dextran sulfate is commonly used in serum-free culture media to reduce cell aggregation in suspension culture. The inhibitory effect of dextran sulfate on the titration of VSV-GFP was confirmed by supplementing the culture medium with this compound during virus production. Our results also demonstrated that extending the incubation time during plaque assay and TCID_50% increases virus titer.

Reliable and Standardized Animal Models to Study the Pathogenesis of Bluetongue and Schmallenberg Viruses in Ruminant Natural Host Species with Special Emphasis on Placental Crossing

Starting in 2006, bluetongue virus serotype 8 (BTV8) was responsible for a major epizootic in Western and Northern Europe. The magnitude and spread of the disease were surprisingly high and the control of BTV improved significantly with the marketing of BTV8 inactivated vaccines in 2008. During late summer of 2011, a first cluster of reduced milk yield, fever, and diarrhoea was reported in the Netherlands. Congenital malformations appeared in March 2012 and Schmallenberg virus (SBV) was identified, becoming one of the very few orthobunyaviruses distributed in Europe. At the start of both epizootics, little was known about the pathogenesis and epidemiology of these viruses in the European context and most assumptions were extrapolated based on other related viruses and/or other regions of the World. Standardized and repeatable models potentially mimicking clinical signs observed in the field are required to study the pathogenesis of these infections, and to clarify their ability to cross the placental barrier. This review presents some of the latest experimental designs for infectious disease challenges with BTV or SBV. Infectious doses, routes of infection, inoculum preparation, and origin are discussed. Particular emphasis is given to the placental crossing associated with these two viruses.

Development of a Rapid Fluorescent Immunochromatographic Test to Detect Respiratory Syncytial Virus

Human respiratory syncytial virus (RSV) is one of the most common viruses infecting the respiratory tracts of infants. The rapid and sensitive detection of RSV is important to minimize the incidence of infection. In this study, novel monoclonal antibodies (mAbs; B11A5 and E8A11) against RSV nucleoprotein (NP) were developed and applied to develop a rapid fluorescent immunochromatographic strip test (FICT), employing europium nanoparticles as the fluorescent material. For the FICT, the limits of detection of the antigen and virus were 1.25 µg/mL and 4.23 × 10⁶ TCID₅₀/mL, respectively, corresponding to 4.75 × 10⁶ ± 5.8 ×10⁵ (mean ± SD) RNA copy numbers per reaction mixture for RSV NP. A clinical study revealed a sensitivity of 90% (18/20) and specificity of 98.18% (108/110) for RSV detection when comparing the performance to that of reverse transcription polymerase chain reaction (RT-PCR), representing a 15% improvement in sensitivity over the SD Bioline rapid kit. This newly developed FICT could be a useful tool for the rapid diagnosis of RSV infection.

NDV entry into dendritic cells through macropinocytosis and suppression of T lymphocyte proliferation

Newcastle disease virus (NDV) causes major economic losses in the poultry industry. Previous studies have shown that NDV utilizes different pathways to infect various cells, including dendritic cells (DCs). Here, we demonstrate that NDV gains entry into DCs mainly via macropinocytosis and clathrin-mediated endocytosis. The detection of cytokines interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), interleukin-12 (IL-12), interleukin-4 (IL-4) and interleukin-10 (IL-10) indicates that NDV significantly induces Th1 responses and lowers Th2 responses. Furthermore, NDV entry into DCs resulted in the upregulation of TNF-related apoptosis-inducing ligand (TRAIL) and cleaved caspase-3 proteins, which in turn activated the extrinsic apoptosis pathway and induced DCs apoptosis. Transwell® co-culture demonstrated that direct contact between live NDV-stimulated DCs and T cells, rather than heated-inactivated NDV, inhibited CD4⁺ T cell proliferation. Taken together, these findings provide new insights into the mechanism underlying NDV infections, particularly in relation to antigen presentation cells and suppression of T cell proliferation.

MicroRNA-34a regulates proliferation and apoptosis of gastric cancer cells by targeting silent information regulator 1

The present study aimed to identify whether microRNA (miRNA/miR)-34a regulates the proliferation and apoptosis of gastric cancer cells by targeting silent information regulator 1 (SIRT1). The expression of miR-34a and SIRT1 and cell viability was investigated in gastric cancer cells. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was applied to determine miR-34a expression in gastric adenocarcinoma, normal pericarcinomatous tissues, human normal gastric mucosa epithelial cell line GES and various gastric cancer cell strains. A bioinformatics method was then used to predict the target gene of miR-34a. A human miR-34a over expression lentiviral vector system was constructed and then used for transfection of the gastric cancer cell line SCG-7901 to determine the expression of SIRT1 mRNA and SIRT1 protein using RT-qPCR and western blot analysis. The MTT method and flow cytometry was used to measure cell proliferation and apoptosis. The relative expression of miR-34a in gastric cancer tissues was significantly decreased compared with that in normal tissues (P<0.01). miR-34a expression was also significantly decreased in low differentiated N2, N3 gastric cancer tissues (P<0.01). However, tumor size and filtration degree were not significantly associated with miR-34a expression. The relative expression of miR-34a was decreased in gastric cancer cells, especially in the SGC-7901 cell line (P<0.01) compared with the GES group. The relative expression of SIRT1 protein was decreased in the miR-34a group compared with the negative control (P<0.01). The rate of proliferation was significantly decreased, whereas the rate of apoptosis was significantly increased in the miR-34a group compared with the NC group (P<0.01). Therefore, the present results suggested that miRNA-34a serves a pivotal role in gastric cancer as a cancer suppressor gene by targeting SIRT1 to regulate the proliferation and apoptosis of gastric cancer cells.

Impairing the function of MLCK, myosin Va or myosin Vb disrupts Rhinovirus B14 replication

Together, the three human rhinovirus (RV) species are the most frequent cause of the common cold. Because of their high similarity with other viral species of the genus Enterovirus, within the large family Picornaviridae, studies on RV infectious activities often offer a less pathogenic model for more aggressive enteroviruses, e.g. poliovirus or EV71. Picornaviruses enter via receptor mediated endocytosis and replicate in the cytosol. Most of them depend on functional F-actin, Rab proteins, and probably motor proteins. To assess the latter, we evaluated the role of myosin light chain kinase (MLCK) and two myosin V isoforms (Va and Vb) in RV-B14 infection. We report that ML-9, a very specific MLCK inhibitor, dramatically reduced RV-B14 entry. We also demonstrate that RV-B14 infection in cells expressing dominant-negative forms of myosin Va and Vb was impaired after virus entry. Using immunofluorescent localization and immunoprecipitation, we show that myosin Va co-localized with RV-B14 exclusively after viral entry (15 min post infection) and that myosin Vb was present in the clusters of newly synthesized RNA in infected cells. These clusters, observed at 180 min post infection, are reminiscent of replication sites. Taken together, these results identify myosin light chain kinase, myosin Va and myosin Vb as new players in RV-B14 infection that participate directly or indirectly in different stages of the viral cycle.

Antiviral activity and possible mechanism of action of constituents identified in Paeonia lactiflora root toward human rhinoviruses

Human rhinoviruses (HRVs) are responsible for more than half of all cases of the common cold and cost billions of USD annually in medical visits and missed school and work. An assessment was made of the antiviral activities and mechanisms of action of paeonol (PA) and 1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose (PGG) from Paeonia lactiflora root toward HRV-2 and HRV-4 in MRC5 cells using a tetrazolium method and real-time quantitative reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay. Results were compared with those of a reference control ribavirin. Based on 50% inhibitory concentration values, PGG was 13.4 and 18.0 times more active toward HRV-2 (17.89 μM) and HRV-4 (17.33 μM) in MRC5 cells, respectively, than ribavirin. The constituents had relatively high selective index values (3.3->8.5). The 100 μg/mL PA and 20 μg/mL PGG did not interact with the HRV-4 particles. These constituents inhibited HRV-4 infection only when they were added during the virus inoculation (0 h), the adsorption period of HRVs, but not after 1 h or later. Moreover, the RNA replication levels of HRVs were remarkably reduced in the MRC5 cultures treated with these constituents. These findings suggest that PGG and PA may block or reduce the entry of the viruses into the cells to protect the cells from the virus destruction and abate virus replication, which may play an important role in interfering with expressions of rhinovirus receptors (intercellular adhesion molecule-1 and low-density lipoprotein receptor), inflammatory cytokines (interleukin (IL)-6, IL-8, tumor necrosis factor, interferon beta, and IL-1β), and Toll-like receptor, which resulted in diminishing symptoms induced by HRV. Global efforts to reduce the level of synthetic drugs justify further studies on P. lactiflora root-derived materials as potential anti-HRV products or lead molecules for the prevention or treatment of HRV.

A positively charged lysine residue at VP2 131 position allows for the enhanced adaptability of foot-and-mouth disease virus serotype A in BHK-21 cells

Field outbreak strains of foot-and-mouth disease virus (FMDV) infect host cells through certain Arg-Gly-Asp (RGD) dependent integrin family of cellular receptors. In contrast, FMDV adapted in non-host cell cultures are reported to acquire the ability to infect cells via heparin sulphate (HS) or other unidentified cell surface molecules. It has been reported that during the serial passage of FMDV serotype A in BHK-21 cell culture, VP2 E131K (E2131K) substitution was fixed within the heparin sulphate binding site. The fixation of positively charged residue at position VP2 131 of serotype A is considered to associate with the ability to utilise alternative receptor. In this study, an infectious full-length cDNA clone for Indian FMDV vaccine strain A IND 40/2000 was constructed. Through site-directed mutagenesis on the cDNA clone, recombinant virus containing positive charged amino acid residue at position VP2 131 was rescued. The recombinant mutated virus was shown to have specific and strong affinity for HS and demonstrated an enhanced infectivity in BHK-21 cell line. The introduction of lysine residue at VP2 131 position that allows cell culture adaptation of FMDV serotype A could be exploited for the generation of vaccine seed stocks with improved growth properties in BHK-21 cell line.

Initial evidence on differences among Enterovirus 71, Coxsackievirus A16 and Coxsackievirus B4 in binding to cell surface heparan sulphate

Cell surface heparan sulphate (HS) mediates infection for many viruses from diverse families. We demonstrated significant antiviral potencies for a number of HS mimetics against a cloned strain of Enterovirus 71 (EV71) in a previous study. Thus, the involvement of HS in mediating viral infection of isolates of human enteroviruses was investigated in Vero and human neural cells in the present work. In both cell lines, heparin and pentosan polysulphate significantly inhibited both infection and attachment of low passage clinical isolates of EV71 and Coxsackievirus A16 (CVA16) but showed no affect on Coxsackievirus B4 (CVB4) (p < 0.05). In addition, enzymatic removal of cell surface HS by heparinase I prevented binding of the clinical EV71 by nearly 50 % but failed to significantly inhibit CVA16 or CVB4 binding in Vero cells. Overall, the findings of this study provides evidence that whilst highly sulphated domains of HS serve as an essential attachment co-receptor for EV71, HS might be used as an alternative attachment receptor by the other member of Human Enterovirus group A, CVA16. In addition, HS may not mediate early infection in CVB4.

Identification of traditional medicinal plant extracts with novel anti-influenza activity

The emergence of drug resistant variants of the influenza virus has led to a need to identify novel and effective antiviral agents. As an alternative to synthetic drugs, the consolidation of empirical knowledge with ethnopharmacological evidence of medicinal plants offers a novel platform for the development of antiviral drugs. The aim of this study was to identify plant extracts with proven activity against the influenza virus. Extracts of fifty medicinal plants, originating from the tropical rainforests of Borneo used as herbal medicines by traditional healers to treat flu-like symptoms, were tested against the H1N1 and H3N1 subtypes of the virus. In the initial phase, in vitro micro-inhibition assays along with cytotoxicity screening were performed on MDCK cells. Most plant extracts were found to be minimally cytotoxic, indicating that the compounds linked to an ethnomedical framework were relatively innocuous, and eleven crude extracts exhibited viral inhibition against both the strains. All extracts inhibited the enzymatic activity of viral neuraminidase and four extracts were also shown to act through the hemagglutination inhibition (HI) pathway. Moreover, the samples that acted through both HI and neuraminidase inhibition (NI) evidenced more than 90% reduction in virus adsorption and penetration, thereby indicating potent action in the early stages of viral replication. Concurrent studies involving Receptor Destroying Enzyme treatments of HI extracts indicated the presence of sialic acid-like component(s) that could be responsible for hemagglutination inhibition. The manifestation of both modes of viral inhibition in a single extract suggests that there may be a synergistic effect implicating more than one active component. Overall, our results provide substantive support for the use of Borneo traditional plants as promising sources of novel anti-influenza drug candidates. Furthermore, the pathways involving inhibition of hemagglutination could be a solution to the global occurrence of viral strains resistant to neuraminidase drugs.