NATURAL HISTORY OF PICOBIRNAVIRUS (PBV) INFECTION AND MOLECULAR ANALYSIS OF THE ISOLATED STRAINS

MASACHESSI GISELA; NATES SILVIA VIVIANA

LAP LAMBERT Academic Publishing

Año: 2015 p. 73

978-3-659-42702-2

Abstract Picobirnaviruses (PBVs) are emerging viruses recently classified into a new viral family, Picobirnaviridae. As regards their structure, they are uncovered viral particles that present an icosahedral symmetry and a diameter of 35 nm approximately. Their genome has two double stranded RNA segments with an estimated size of 2,4-2,6 kbp (segment 1, large) and 1,5-1,8 kbp (segment 2, small). Studies carried out at present have helped to clarify the genomic and structural characteristics of PBVs, allowing us to place them in a new viral taxon. However, there is not enough data on this viral family to provide a comprehensive overview of the virus-host-environment relationship. The general aim of this thesis was to characterize the natural history of infection by picobirnavirus (PBV) and the genomic diversity of viral strains circulating in our environment. In order to achieve that aim, it was essential to determine the range of the animal species involved in the maintenance of the virus in nature, the viral transmission route, the genomic diversity of intraspecies and interspecies viral strains and the infection model that the virus establishes in the different host species. This information was useful to classify the links of the viral transmission chain, which come together to promote the circulation of this virus in nature. The methodology consisted in the usage of serial sampling of stools belonging to 150 animal species living in the Zoo and in raising and breeding farms of rheas and pigs in Córdoba (N= 1124) and in the reanalysis of 2224 fecal samples belonging to children with diarrhea, which were collected between 1977 and 2002. In order to detect the viral genome, the fecal samples were analyzed through molecular methods (polyacrylamide gel electrophoresis and/or reverse transcription-polymerase chain reaction of the viral genome) which allowed the detection of PBV in relation to the viral load excreted and the genomic characterization of isolated viral strains. The results obtained in the present thesis have helped to arrive to the following conclusions: 1.PBVs constitute a viral group that infects a wide range of host species, breaking the animal species barrier for the infection. 2.The extensive genetic diversity, defined by a viral polymerase fragment, is an intrinsic characteristic of PBVs. This fact would suggest that these viruses exist in nature as viral quasispecies, that present nucleotide blocks in all strains as a distinctive characteristic of PBVs, independently of the animal species excreting the virus. Me parece que esta frase hay que borrarla porque en el cuerpo de la tesis no está el alineamiento de cepas de PBV aisladas de diferentes especies animales que muestra esto. Es la Figura 20 de tu tesis 3.In the field of virology, PBVs are a group of virus that establishes a persistent and asymptomatic relationship with the host, even in conditions of physiological distress and high viral excretion. Therefore, the original proposal that PBVs could be an etiological agent of diarrhea must be replaced by the concept that PBVs detected in feces only reflect the viral replication in the gastrointestinal tract, without considering the virus as an etiological agent of diarrhea. 4.The natural history of circulation of PBVs in nature is characterized by a succession of asymptomatic events between infected and susceptible hosts, becoming a silent history of viral endemic transmission, infection and circulation. 5.PBVs are likely to be found in the gastrointestinal tract, which raises questions about the molecular mechanisms that rule the persistent and asymptomatic relationship with their host, and the potential benefit for the host to maintain this interrelation.