BACKGROUND The emergence of avian influenza A(H7N9) virus in poultry causing zoonotic human infections was reported on March 31, 2013. Development of A(H7N9) candidate vaccine viruses (CVV) for pandemic preparedness purposes was initiated without delay. Candidate vaccine viruses were derived by reverse genetics using the internal genes of A/Puerto/Rico/8/34 (PR8). The resulting A(H7N9) CVVs nee...

avian infectious bronchitis is an acute and highly contagious disease that mainly causes respiratory symptoms in poultry. a number of serotypes and variants of the viral agent with poor cross-protection are the major problem to achieve desired immunity from vaccination. the s1 subunit of s glycoprotein (spike) is the major determinant of ibv so that a minor change in amino acid sequence of this...

Experimental infection models are valuable tools for understanding and preventing the deposition of Salmonella enteritidis inside eggs. Oral inoculation is believed to closely simulate naturally occurring S. enteritidis infections of chickens, but oral infection studies have often generated relatively low frequencies of egg contamination. The present study assessed whether repeated in vivo pass...

A genetically diverse population of Haemonchus contortus was serially passaged through Merino hosts bred for either increased or decreased resistance to the parasite. After 30 parasite generations, the resulting nematode sub-populations were compared with each other and with the foundation population, by infecting lines of the selected sheep and measuring the resulting faecal egg counts (FECs) ...

The previous reports from this laboratory (Yoshino et al., 1956 a, 1956 b) indicated that both mouse passaged CVS and 7-day egg passaged Flury strains of rabies virus could infect the 1-day egg resulting in high viral concentrations in the embryo which were comparable to those usually reached in the infected mouse brain, and that these strains after adapted to the 1-day egg by serial passage co...

Allelic variation in 6 microsatellite markers was compared between frozen Schistosoma mansoni eggs and laboratory-passaged worms originating from the same 5 fecal samples obtained from Brazilian residents. Based on allelic richness values, the number of alleles detected per locus did not differ between egg and worm DNA templates. However, our ability to score loci differed between these DNA tem...

The effectiveness of the annual influenza vaccine has declined in recent years, especially for the H3N2 component, and is a concern for global public health. A major cause for this lack in effectiveness has been attributed to the egg-based vaccine production process. Substitutions on the hemagglutinin glycoprotein (HA) often arise during virus passaging that change its antigenicity and hence va...

BACKGROUND Vaccines constitute a unique selective pressure, different from natural selection, drives the evolution of influenza virus. In this study, A/Chicken/Shanghai/F/1998 (H9N2) was continually passaged in specific pathogen-free embryonated chicken eggs with or without selective pressures from antibodies induced by homologous maternal antibodies. Genetic mutations, antigenic drift, replica...

Transplacental transmission of bluetongue virus has been shown previously for the North European strain of serotype 8 (BTV-8) and for tissue culture or chicken egg-adapted vaccine strains but not for field strains of other serotypes. In this study, pregnant ewes (6 per group) were inoculated with either field or rescued strains of BTV-2 and BTV-8 in order to determine the ability of these virus...

L-type bovine spongiform encephalopathy (L-BSE) is an atypical form of BSE that is transmissible to cattle and several lines of prion protein (PrP) transgenic mice, but not to wild-type mice. In this study, we examined the transmissibility of sheep-passaged L-BSE prions to wild-type mice. Disease-associated prion protein (PrP(Sc)) was detected in the brain and/or lymphoid tissues during the lif...