Use of flow cytometry for rapid, quantitative detection of poliovirus-infected cells via TAT peptide-delivered molecular beacons

Establishment, verification and application of rapid detection of baculovirus infectious titer by flow cytometry

Titer detection of baculovirus usually is time-consuming. It is important to establish a rapid detection method for baculovirus titer. In this report, Staining of cells with a fluorescently labeled anti-gp64 antibody allows for identification of infected insect cells. By inoculating cultures with a series of log dilutions of virus, and staining of the cultures 13-22 h post inoculation, the ratio of infected to un-infected insect cells can be determined by flow cytometry(FCM). Statistical analysis of the percentage of infected cells in the virus dilution series enables accurate infectious titer determination. The culture time, cell growth state, the concentration of GP64-APC antibody and the concentration of inactivated FBS in diluent were optimized. The generality, repeatability and intermediate precision of the method were verified. The FCM method has the advantages of simplicity, accuracy, low cost and good repeatability.

Dual-label flow cytometry-based host cell adhesion assay to ascertain the prospect of probiotic Lactobacillus plantarum in niche-specific antibacterial therapy

Host cell adhesion assays that provide quantitative insight on the potential of lactic acid bacteria (LAB) to inhibit adhesion of intestinal pathogens can be leveraged for the development of niche-specific anti-adhesion therapy. Herein, we report a dual-colour flow cytometry (FCM) analysis to assess the ability of probiotic Lactobacillus plantarum strains to impede adhesion of Enterococcus faecalis, Listeria monocytogenes and Staphylococcus aureus onto HT-29 cells. FCM in conjunction with a hierarchical cluster analysis could discern the anti-adhesion potential of L. plantarum strains, wherein the efficacy of L. plantarum DF9 was on a par with the probiotic L. rhamnosus GG. Combination of FCM with principal component analysis illustrated the relative influence of LAB strains on adhesion parameters kd and em of the pathogen and identified probiotic LAB suitable for anti-adhesion intervention. The analytical merit of the FCM analysis was captured in host cell adhesion assays that measured relative elimination of adhered LAB vis-à-vis pathogens, on exposure to either LAB bacteriocins or therapeutic antibiotics. It is envisaged that the dual-colour FCM-based adhesion assay described herein would enable a fundamental understanding of the host cell adhesion process and stimulate interest in probiotic LAB as safe anti-adhesion therapeutic agents against gastrointestinal pathogens.

Dengue Virus and Its Relation to Human Glycoprotein IIb/IIIa Revealed by Fluorescence Microscopy and Flow Cytometry

Understanding dengue virus (DENV)-induced hemorrhage remains a challenging jigsaw puzzle with many pieces missing to understand the complex interactions between DENV and blood coagulation system. To use flow cytometry studying the interactions between DENV and human platelet aggregation receptor, glycoprotein IIb/IIIa (gpIIb/IIIa), directly conjugated fluorochrome monoclonal antibody (mAb) is essential to facilitate multifluorochrome immunostaining. However, the obstacle was that no directly conjugated fluorochrome-anti-DENV mAb had been commercially available. To overcome, we directly conjugated fluorochrome to a primary anti-DENV mAb using a LYNX rapid conjugation kit. Flow cytometry analysis showed that this conjugated antibody and anti-gpIIb/IIIa mAb were able to detect DENV and CD41a simultaneously. Fluorescence microscopy analysis further demonstrated CD41a superficially and DENV intracellularly. Potentially, this strategy can facilitate virologists for directly conjugating any virus-specific primary antibodies, which are not commercially available with fluorochrome, to study the infectivity in any surface marker-specific hosts through flow cytometry. Together, DENV can interact with both human gpIIb/IIIa^- and gpIIb/IIIa⁺ cells revealed by flow cytometry and fluorescence microscopy for the first time.

The role of viruses in coral health and disease

Metagenomic and electron microscopy studies confirm that the coral microbiome contains a rich diversity and abundance of viruses. While there have been no definitive tests of disease causation by viruses in corals, viruses have been implicated as coral pathogens in a number of studies. Growing evidence also indicates that latent viral infections can compromise the algal symbionts under environmental stress and may be involved in the coral bleaching response. Conversely, bacteriophages and archaeal phage viruses are abundant in the microbiome of healthy corals and are likely to be involved in complex ecological networks, genetic material transfer and selective co-evolution within the surface mucus layers and tissues. The relative importance of viral control of bacterial and archaeal populations is unknown, but they are almost certain to be exerting some level of control on the composition and maintenance of the coral microbiome. While rapid leaps in the capability to detect viruses have been made due to advances in metagenomics and bioinformatics, these approaches need now to be integrated with in vitro culture and challenge experiments to assess the functional roles of viruses in health and disease, and it is imperative that interactions with other members of the coral microbiome are taken into account when assessing disease causation.

Rapid detection of infectious rotavirus group A using a molecular beacon assay

Rapid, sensitive and specific methods are necessary to detect and quantify infectious viruses. Cultivating and detecting enteric viruses in cell culture are difficult, thus impairing the advancement of knowledge regarding virus-induced diarrhea. Rotavirus (RV) detection has been conducted by serological or molecular biology methods, which do not provide information regarding viral infectivity. Molecular beacons (MBs) have demonstrated efficacy for viral detection in cell culture. We propose a MB assay to detect human rotavirus group A (HuRVA) in cell culture. MA104 cells were mock-infected or infected with HuRVA strains (RotaTeq(®) vaccine and K8 strains), and a specific MB for the HuRVA VP6 gene was used for virus detection. Mock-infected cells showed basal fluorescence, while infected cells exhibited increased fluorescence emission. MB hybridization to the viral mRNA target of HuRVA was confirmed. Fluorescence increased according to the increase in the number of infectious viral particles per cell (MOI 0.5-MOI 1). This technique provides quick and efficient HuRVA detection in cell culture without a need for viral culture for several days or many times until cytopathic effects are visualized. This methodology could be applied in the selection of samples for developing RV vaccines.

Fluorescent Protein Approaches in Alpha Herpesvirus Research

In the nearly two decades since the popularization of green fluorescent protein (GFP), fluorescent protein-based methodologies have revolutionized molecular and cell biology, allowing us to literally see biological processes as never before. Naturally, this revolution has extended to virology in general, and to the study of alpha herpesviruses in particular. In this review, we provide a compendium of reported fluorescent protein fusions to herpes simplex virus 1 (HSV-1) and pseudorabies virus (PRV) structural proteins, discuss the underappreciated challenges of fluorescent protein-based approaches in the context of a replicating virus, and describe general strategies and best practices for creating new fluorescent fusions. We compare fluorescent protein methods to alternative approaches, and review two instructive examples of the caveats associated with fluorescent protein fusions, including describing several improved fluorescent capsid fusions in PRV. Finally, we present our future perspectives on the types of powerful experiments these tools now offer.