Neuraminidase activity was expressed as the arbitrary units of lu

Neuraminidase activity was expressed as the arbitrary units of luminescence signals or as calculated units. Neuraminidase Inhibition Assay with Zanamivir Samples were diluted with PBS to give approximate neuraminidase activity selleck compound of 5,000 arbitrary units of luminescence signals and mixed with an equal volume of ten-fold serial dilutions of zanamivir (from 10 mM to 0.1 nM in PBS) or DANA (from 10 mM to 0.1 ��M in PBS). The final concentrations in the mixtures ranged from 5 mM to 0.05 nM for zanamivir and 5 mM to 0.05 ��M for DANA. The mixtures were incubated at 37��C for 30 min and assayed for neuraminidase activity. The IC50 value was read on the inactivation dose response curve. Plaque Assay The infectivity of viruses was determined by plaque assay as described below.

Ten-fold serial dilutions of virus samples were made in Hanks balanced salt solution (HBSS; GIBCO, Gland Island, NY, USA) and 0.1 ml of the dilutions was inoculated on MDCK cell monolayers in 6-well tissue culture plates (Corning, Lowell, MA, USA). After adsorption of the virus onto the cells for 30 min at room temperature, 1.6 ml of Leibovitz��s L15 medium (GIBCO, Gland Island, NY, USA) containing 0.6% SeaKem ME agarose (Lonza, Basel, Switzerland), 1.5% gelatin (Nacalai, Kyoto, Japan) and 2.5 ��g/ml TPCK-trypsin was added to each well and allowed to solidify. The plates were incubated for 3 days at 34��C and the number of plaques was counted. Infectivity was expressed as plaque forming units (pfu) per ml.

Virus Growth Inhibition Assay The inhibition of virus growth by neuraminidase inhibitors in the presence or absence of bacterial neuraminidase was assayed by measuring the released progeny virus in the culture fluid of infected cells. MDCK cells seeded on 12-well tissue culture plates were inoculated with 50 ��l of virus suspension at a MOI of 0.001 or 0.01. After the adsorption for 1 h on ice, 1 ml MEM supplemented with 2.5 ��g/ml TP
Understanding host-parasite interactions represents a major challenge in evolutionary biology. Parasites cause substantial deleterious effects on their hosts, and therefore represent a major driving force for their evolution [1]. In parallel, parasites have to cope with the evolving host-defence mechanisms, i.e. they must co-evolve with their host to avoid elimination.

This antagonistic co-evolution in host-parasite interactions can be illustrated by an arms race in which both host and parasite develop mechanisms to circumvent weapons developed by their opponent. In this context, evolutionary hypotheses like the Red Queen Hypothesis [2] predict that diversity and polymorphism of molecules occurs especially on AV-951 molecules that play key roles in the host-parasite interplay [3]. In vertebrate host/parasite interactions, adaptive immunity is the ultimate outcome of this molecular arms race.

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