Measurement of the gamma ray background in the Davis Cavern at the Sanford Underground Research Facility

Deep underground environments are ideal for low background searches due to the attenuation of cosmic rays by passage through the earth. However, they are affected by backgrounds from γ-rays emitted by 40K and the 238U and 232Th decay chains in the surrounding rock. The LUX-ZEPLIN (LZ) experiment will search for dark matter particle interactions with a liquid xenon TPC located within the Davis campus at the Sanford Underground Research Facility, Lead, South Dakota, at the 4,850-foot level. In order to characterise the cavern background, in-situ γ-ray measurements were taken with a sodium iodide detector in various locations and with lead shielding. The integral count rates (0--3300~keV) varied from 596~Hz to 1355~Hz for unshielded measurements, corresponding to a total flux in the cavern of 1.9±0.4~γ cm−2s−1. The resulting activity in the walls of the cavern can be characterised as 220±60~Bq/kg of 40K, 29±15~Bq/kg of 238U, and 13±3~Bq/kg of 232Th

Demonstration of loss of attenuation and extended field persistence of a live avian metapneumovirus vaccine

A live A type avian metapneumovirus (AMPV) vaccine which had been shown to be highly protective and short lived in experimental conditions was found to persist for longer periods in the field and to be associated with disease. Previously other factors such as possible secondary pathogens and management considerations had made it impossible to conclude whether the observed disease was a result of an increase in the vaccine virulence. In this study, an AMPV was isolated from poults on a farm which had been vaccinated with the same live A type vaccine. Full sequencing of the isolate, the vaccine and the vaccine progenitor confirmed its vaccine origin and further showed that generation of the vaccine had only involved nine substitutions of which three coded for amino acid changes. The isolated virus was inoculated into 1-day-old turkey poults in disease secure isolators and shown to cause disease with a severity similar to that caused by virulent field virus. Only two coding mutations were associated with this reversion to virulence

A molecular Study of Attenuation and Reversion to virulence in Live APV Vaccines

none5[RELAZIONE] Si tratta di un convegno internazionale di virologia aviare, che si svolge con cadenza biennale sui temi di virologia aviare di maggiore interesse. E' ad invito e sono ammesse solo presentazioni orali. Sono presenti i maggiori studiosi mondiali dell'argomento oggetto del simposio.noneNAYLOR C.J.; CATELLI E.; CECCHINATO M.; JONES R.C.; SAVAGE C.E.Naylor, C. J.; Catelli, E.; Cecchinato, Mattia; Jones, R. C.; Savage, C. E

FIELD AND EXPERIMENTAL EVIDENCES OF AVIAN PNEUMOVIRUS VACCINE REVERSION TO VIRULENCE

Avian pneumovirus causes an upper respiratory tract infection in turkeys leading to turkey rhinotracheitis (TRT) and in some other avian species, including chickens where it is also involved, in the etiology of multifactorial diseases such as swollen head syndrome. Since the 1980s a number of live attenuated subtype A and B APV vaccines have been developed in Europe and these have generally afforded good protection. All have been produced by repeated passages of field virus in a laboratory culture system to achieve various degrees of attenuation. They are widely used in commercial growing turkeys and to prime future layers and breeders. When tested under experimental conditions, these empirically derived vaccines were shown to be fully protective whilst not causing detectable disease themselves. However, they have not performed as well when used in the field and unstable attenuation has been considered to be a possible factor. Since pneumoviruses are single-stranded RNA viruses their relatively high mutation rates have been thought to be the underlying reason for instances of reversion to virulence observed in experimental conditions (1). This paper describes the first evidence of reversion of an APV vaccine in the field. First, systematic evidence of extended vaccine virus persistence in the field arose from a longitudinal study performed in the UK in 1995. Secondly, from an outbreak of TRT in an Italian turkey flock previously vaccinated at day old, we isolated an APV which proved to be a vaccine derivative. Finally, in order to determine whether vaccine virus or a derivative of increased virulence had been isolated, the virus was applied to 1 day old poults in secure isolation conditions. The vaccine derivative virus was shown to be able to cause clinical disease