Assessment of hemagglutination activity of porcine deltacoronavirus.

Porcine deltacoronavirus (PDCoV) is an emerging swine enteric coronavirus that causes diarrhea in piglets. However, the biological characteristics of PDCoV are unclear. In this study, the hemagglutination (HA) abilities of two PDCoV strains (CH-01 and HNZK-04) were investigated. Our results showed that PDCoV has the ability to agglutinate rabbit erythrocytes after virion pretreatment with trypsin or neuraminidase. Additionally, the HA assay results showed a significant positive correlation with the infectious viral titer. Our results suggest that assessing the HA activity of PDCoV may be a useful diagnostic method for investigating and surveilling PDCoV infections.

Relating influenza virus membrane fusion kinetics to stoichiometry of neutralizing antibodies at the single-particle level.

The ability of antibodies binding the influenza hemagglutinin (HA) protein to neutralize viral infectivity is of key importance in the design of next-generation vaccines and for prophylactic and therapeutic use. The two antibodies CR6261 and CR8020 have recently been shown to efficiently neutralize influenza A infection by binding to and inhibiting the influenza A HA protein that is responsible for membrane fusion in the early steps of viral infection. Here, we use single-particle fluorescence microscopy to correlate the number of antibodies or antibody fragments (Fab) bound to an individual virion with the capacity of the same virus particle to undergo membrane fusion. To this end, individual, infectious virus particles bound by fluorescently labeled antibodies/Fab are visualized as they fuse to a planar, supported lipid bilayer. The fluorescence intensity arising from the virus-bound antibodies/Fab is used to determine the number of molecules attached to viral HA while a fluorescent marker in the viral membrane is used to simultaneously obtain kinetic information on the fusion process. We experimentally determine that the stoichiometry required for fusion inhibition by both antibody and Fab leaves large numbers of unbound HA epitopes on the viral surface. Kinetic measurements of the fusion process reveal that those few particles capable of fusion at high antibody/Fab coverage display significantly slower hemifusion kinetics. Overall, our results support a membrane fusion mechanism requiring the stochastic, coordinated action of multiple HA trimers and a model of fusion inhibition by stem-binding antibodies through disruption of this coordinated action.

[Nonspecific antiviral preparations: hopes and realities (a review of the literature)]. / Nespetsificheskie protivovirusnye preparaty: nadezhdy i realii (obzor literatury).

The review of the literature presents the information about the properties of antiviral drugs, spectrum of action and theoretical bases of their development. It is shown that unspecific drugs surpass the traditional vaccinal and serous agents that are of importance in terms of military medicine. The conclusion is made that it is reasonable to direct the development of therapeutic strategy and tactics in virus infections to the search of optimal combinations of unspecific and immunobiological drugs with pathognomic and symptomatic medicaments.

High-capacity in vitro assessment of anti-hepatitis B virus compound selectivity by a virion-specific polymerase chain reaction assay.

An integrated assessment system specific for hepatitis B virus (HBV) Dane particle DNA was developed to examine the activity of potential anti-HBV compounds in chronic HBV-producing HepG2-derived 2.2.15 cells. Cell culture, immunoaffinity purification, polymerase chain reaction, and hybrid-capture detection were performed in the microtiter format to facilitate increased throughput by automation. The high sensitivity afforded by the assay provided quantitative detection of less than 0.5 fg of extracellular HBV DNA from 25 microliters of cell culture supernatants, and drug-induced reductions in HBV titers greater than 100-fold were easily measured. Fluorometric determination of total cellular DNA from the same 96-well proliferating cell cultures allowed simultaneous evaluation of inhibition of cell growth, thus providing the ability to assess the overall selectivities of candidate compounds in a single experiment. The potent activities of three anti-HBV compounds, the (+) and (-) enantiomers of cis-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxythiolane-5-yl]cytosine (FTC) and D-carbocyclic-2'-deoxyguanosine (CDG), were confirmed by this method. (-)-FTC was more active than its (+) enantiomer (50% inhibitory concentrations, 0.033 +/- 0.006 and 0.723 +/- 0.160 microM [standard error of the mean; SEM], respectively), while both enantiomers demonstrated a lack of cytotoxicity at 200 microM. CDG was more potent (50% inhibitory concentration, 0.0063 +/- 0.0007 microM [SEM]) but was also significantly more toxic, inhibiting cell growth by 50% at 32 +/- 6 microM (SEM). These results demonstrate the usefulness of this immunoaffinity-based, quantitative polymerase chain reaction system as a high-capacity in vitro tool for assessment of anti-HBV compound selectivity.