Size of ORV areas in European countries in km² exclusively vaccinated with one particular oral vaccine strain against rabies over the entire time span of ORV.

<p>Size of ORV areas in European countries in km² exclusively vaccinated with one particular oral vaccine strain against rabies over the entire time span of ORV.</p

Size of ORV areas in European countries in km² vaccinated with two different oral vaccine strains against rabies over the entire time span of ORV.

<p>Size of ORV areas in European countries in km² vaccinated with two different oral vaccine strains against rabies over the entire time span of ORV.</p

Number of individual vaccine doses disseminated in ORV programmes in Europe between 1978 and 2014.

<p>Approximate calculation of the numbers of vaccine doses of different oral vaccine strains against rabies over the past four decades (x axis) based on the cumulative area ever vaccinated with a single vaccine bait (y axis) and an assumed average bait density of 20 baits/km².</p

Spatial extent of ORV areas in Europe ever covered with a single vaccine bait of particular oral vaccine strains against rabies during 1978 and 2014.

<p>(A) SAG1 (orange), Vnukovo 32 (brown) and RV-97 (magenta), and (B) SAD VA1 (green), KMIEV-94 (blue) and ERA G333 (yellow).</p

Size of ORV areas in European countries in km² vaccinated with three or more different oral vaccine strains against rabies over the entire time span of ORV.

<p>Size of ORV areas in European countries in km² vaccinated with three or more different oral vaccine strains against rabies over the entire time span of ORV.</p

Implementation of ORV programmes in Europe (1978–2014).

<p>The year of (re-) implementation, duration and the year of cessation of ORV programmes including early field trials in several European countries is depicted. Red coloured bars show countries which achieved a rabies free status due to ORV and blue coloured bars represent countries in which ORV programmes are still implemented.</p

ORV effort and oral vaccine strains against rabies.

<p>Spatial extent of ORV area showing the spatial distribution of different oral vaccine strains against rabies used between 1978 and 2014. Deviating colours from those assigned to certain vaccines indicate overlapping regions.</p

Avian Influenza Virus H3 Hemagglutinin May Enable High Fitness of Novel Human Virus Reassortants

<div><p>Reassortment of influenza A virus genes enables antigenic shift resulting in the emergence of pandemic viruses with novel hemagglutinins (HA) acquired from avian strains. Here, we investigated whether historic and contemporary avian strains with different replication capacity in human cells can donate their hemagglutinin to a pandemic human virus. We performed double-infections with two avian H3 strains as HA donors and a human acceptor strain, and determined gene compositions and replication of HA reassortants in mammalian cells. To enforce selection for the avian virus HA, we generated a strictly elastase-dependent HA cleavage site mutant from A/Hong Kong/1/68 (H3N2) (Hk68-Ela). This mutant was used for co-infections of human cells with A/Duck/Ukraine/1/63 (H3N8) (DkUkr63) or the more recent A/Mallard/Germany/Wv64-67/05 (H3N2) (MallGer05) in the absence of elastase but presence of trypsin. Among 21 plaques analyzed from each assay, we found 12 HA reassortants with DkUkr63 (4 genotypes) and 14 with MallGer05 (10 genotypes) that replicated in human cells comparable to the parental human virus. Although DkUkr63 replicated in mammalian cells at a reduced level compared to MallGer05 and Hk68, it transmitted its HA to the human virus, indicating that lower replication efficiency of an avian virus in a mammalian host may not constrain the emergence of viable HA reassortants. The finding that HA and HA/NA reassortants replicated efficiently like the human virus suggests that further HA adaptation remains a relevant barrier for emergence of novel HA reassortants.</p></div

Gene composition of DkUkr63 reassortants.

<p>Gene segments originating from DkUkr63 (D) and Hk68 (H) are shown in dark and light grey, respectively (HD indicates a mixed population). Co-infections with Hk68-Ela and DkUkr63 were performed either in the presence (+) or absence (−) of TPCK-treated trypsin. Supernatants were harvested either at eight or 24 hours after co-infection, the RNA isolated and subjected to RT-PCR for genotyping. Reassortants with no detectable HA titer in the supernatant after co-infection were propagated in embryonated chicken eggs and are indicated by a super-scripted ^e.</p

Growth curves of DkUkr63 HA reassortants.

<p>The gene segment constellation of each reassortant is given next to each chart: Hk68 genes (black) and DkUkr63 genes (red). The presence of diverse additional DkUkr63 segments is indicated by the abbreviation ‘div’. From supernatants of A549 cells infected with a MOI of 10⁻³, viral titers were determined by plaque assays on MDCK cells. The growth curves of the parental viruses Hk68 (black filled circles), Hk68-Ela (black empty circles) and DkUkr63 (red filled circles) in each chart represent identical data and were drawn in for comparison. Growth curves were determined by plaque titrations of duplicate or quadruplicate infected cell cultures (in the latter case indicated by a diamond in the chart legend). Reassortants reaching titers at 48 h not less than one magnitude below Hk68 are highlighted by grey rectangles.</p