RESUMO
Paramyxoviruses include many important animal and human pathogens. Most paramyxoviruses have two integral membrane proteins: fusion protein (F) and attachment proteins hemagglutinin, hemagglutinin-neuraminidase, or glycoprotein (G), which are critical for viral entry into cells. J paramyxovirus (JPV) encodes four integral membrane proteins: F, G, SH, and transmembrane (TM). The function of TM is not known. In this work, we have generated a viable JPV lacking TM (JPV∆TM). JPV∆TM formed opaque plaques compared with JPV. Quantitative syncytia assays showed that JPV∆TM was defective in promoting cell-to-cell fusion (i.e., syncytia formation) compared with JPV. Furthermore, cells separately expressing F, G, TM, or F plus G did not form syncytia whereas cells expressing F plus TM formed some syncytia. However, syncytia formation was much greater with coexpression of F, G, and TM. Biochemical analysis indicates that F, G, and TM interact with each other. A small hydrophobic region in the TM ectodomain from amino acid residues 118 to 132, the hydrophobic loop (HL), was important for syncytial promotion, suggesting that the TM HL region plays a critical role in cell-to-cell fusion.
Assuntos
Proteínas de Membrana/genética , Mutação , Paramyxovirinae/genética , Proteínas Virais/genética , Animais , Fusão Celular , Linhagem Celular , Chlorocebus aethiops , Eletroforese em Gel de Poliacrilamida , Citometria de Fluxo , Imunofluorescência , Células Gigantes/metabolismo , Glicoproteínas/genética , Glicoproteínas/metabolismo , Células HEK293 , Humanos , Proteínas de Membrana/metabolismo , Paramyxovirinae/crescimento & desenvolvimento , Paramyxovirinae/metabolismo , Ligação Proteica , Células Vero , Proteínas Virais de Fusão/genética , Proteínas Virais de Fusão/metabolismo , Ensaio de Placa Viral , Proteínas Virais/metabolismoRESUMO
BACKGROUND: Hepatic disease in psittacine birds is common but challenging to diagnose. This retrospective study evaluates the diagnostic value of plasma biochemistry, haematology, radiography and endoscopic visualisation in psittaciforms with suspected hepatic disease that underwent endoscopic liver biopsy. METHODS: Clinical records of 28 companion psittaciforms from a veterinary teaching hospital (2007-2016) were reviewed. Diagnostic results were categorised as abnormal or normal and compared with histopathology for agreement or disagreement. Statistical significance was determined by kappa test for agreement and McNemar's test for disagreement. RESULTS: 11 of 28 psittaciforms (39.3 per cent) had clinical signs considered specific for liver disease. 25 of 28 (89.3 per cent) psittaciforms had histopathological liver lesions. Gross changes radiographically and endoscopically agreed with histopathology in 57.1 per cent and 53.6 per cent of cases, respectively. Aspartate aminotransferase (AST) (48.1 per cent), creatine phosphokinase (73.1 per cent) and albumin by protein electrophoresis (50 per cent) showed the highest agreement. Kappa was not significant for any parameters, while McNemar's test for disagreement was significant for radiography, endoscopy, AST, lactate dehydrogenase, bile acid, total protein (chemistry), cholesterol, triglycerides, uric acid and glucose. CONCLUSION: Overall, changes on plasma biochemistry, radiography or endoscopy are non-specific and do not consistently agree with histopathology results. Endoscopic liver biopsy is highly recommended if there is clinical suspicion of hepatic disease.