Broad tissue and cell tropism of avian bornavirus in parrots with 1 proventricular dilatation disease

24 Avian bornaviruses (ABV), representing a new genus within the family Bornaviridae, were 25 recently discovered in parrots with proventricular dilatation disease (PDD) from North 26 America and Israel. We show here that closely related viruses are also present in captive 27 European parrots of various species with PDD. The six ABV strains that we identified in 28 clinically diseased birds are new members of the previously defined ABV genotypes 2 and 4. 29 Viruses of both genotypes readily established persistent, non-cytolytic infections in quail and 30 chicken cell lines, but did not grow in cultured mammalian cells in which classical Borna 31 disease virus strains replicate very efficiently. ABV antigens were present in both the 32 cytoplasm and nucleus of infected cells, suggesting nuclear replication of ABV like classical 33 Borna disease virus. The genome organization of avian and mammalian bornaviruses is 34 highly conserved, except that ABV lacks a distinct control element in the 5’-non-coding 35 region of the bicistronic mRNA encoding the viral proteins X and P. RT-PCR analysis 36 demonstrated the presence of virus in many if not all organs of birds with PDD. Viral nucleic 37 acid was also found in feces of diseased birds, suggesting virus transmission by the fecal38 oronasal route. Immunohistochemical analysis of organs from birds with PDD revealed that 39 infection with ABV is not restricted to cells of the nervous system. Thus, ABV exhibits a 40 broad tissue and cell tropism that is strikingly different from classical Borna disease virus. 41 on O cber 8, 2017 by gest http/jvi.asm .rg/ D ow nladed fom Bornaviruses in parrots with PDD 3 INTRODUCTION 42 Proventricular dilatation disease (PDD) is an inflammatory disease of birds, first described in 43 the 1970s as Macaw Wasting Disease during an outbreak among macaws (4, 6, 12, 22). PDD 44 primarily affects the autonomic nerves of the upper and middle digestive tract, including the 45 esophagus, crop, proventriculus, ventriculus, and duodenum. Clinically, PDD cases usually 46 present with gastrointestinal tract dysfunction such as dysphagia, regurgitation, and presence 47 of undigested food in feces. A dilated proventriculus and ventriculus is a typical radiographic 48 finding and paper-thin walls and spontaneous ruptures of these parts of the digestive tract are 49 frequently seen during necropsy (2). Neurological symptoms such as ataxia and abnormal gait 50 may accompany the gastrointestinal tract symptoms. PDD is generally fatal, although the 51 disease may not always progress fast. Microscopically, PDD is recognized by the presence of 52 immune cell infiltrates at enteric ganglia and nerves. Similar infiltrates may also be present in 53 the brain, spinal cord, peripheral nerves, conductive tissue of the heart, smooth and cardiac 54 muscle, and adrenal glands (1). At present, clinical diagnosis is based on biopsy of crop wall 55 and demonstration of inflammatory cell infiltrates at ganglion cells (11) 56 Two independent searches for a viral etiology of PDD led to the identification of a group of 57 novel viruses that form a new genus in the family Bornaviridae (17, 19). RNA products 58 derived from these viruses, now collectively designated avian bornaviruses (ABV), were 59 found in tissue samples from parrots with PDD but not in healthy birds from North America 60