33 FINE SPECIFICITY OF ANTIBODIES PRECIPITATING DANE PARTICLES IN HEPATITIS B (HB)

D.Cavalletto, P. Pontisso, F. Belussi*and A. A~berti Istituto di Medicina Clini- ca, Clinlca Medica II, University of Padova and *Ospedale S Maria delle Grazie, Venezia (Italy).

In 1978 antibodies precipitating Dane particles (the HB virion) were identified in acute hepa- titis B sera and proposed as relevant for virus clearance. More recently, their relation to preS encoded proteins of the virus envelope has been demonstrated. To define the epitopic spe- cificity of these antibodies, we studied acute hepatitis B sera with a variety of methods, de- signed to detect antibodies to sequential and conformational preS1 and preS2 antigens. These methods included: 1)radioimmunoprecipitation of radiolabelled virions and of recombinant part ! cles; 2)solid phase ELISA with synthetic peptides; 3)competition assays with monoclonal anti- preS antibodies of defined sequence specificity; 4)immunoblotting. Acute phase sera, obtained at clinical onset or during the first 10 days of illness were reactive with virions while anti- preS2 negative. These sera were found to contain anti-preS1 antibodies which were directed a- gainst conformational epitopes on native virions in most samples, while only 20% also contained antibodies to sequential epitopes. These were located in the N-terminus portion(16-30 sequenc~ of preS1 in most cases, but sera reactive with C-terminus(95-107 sequence)were also identifie~ Anti-preS2 became positive in 80% of acute hepatitis B sera after maximum liver damage and re- mained detectable during convalescence, being found, in selected cases, even 7 years after re- covery. All anti-preS2 positive sera reacted with a (120-150) preS2 peptide, being therefore directed against a linear epitope. Anti-preS2 with identical specificity was also detected in serum in 50% of 40 recipients of a plasma-derived HB vaccine. These results indicate that an- tibodies to Dane particles include antibodies to preS1, directed against conformational(mainly) and sequential epitopes and produced early in acute infection, and antibodies to sequential preS2 epitopes, which appear later during acute phase. These findings are relevant for deve- lopment of diagnostic assays and of preS containing vaccines.

34 EFFECTS OF CLUCACON ON SYSTEMIC AND SPLANCHNIC CIRCULATION IN CONSCIOUS mATS WITH BILIARY CIRRHOSIS. R. C e r i n i , A. Koshy, A. Hadensue , S .S . Lee, P. G a r n i e r , D. Lebrec INSERM U24, H S p i t a l Beau jon , C l i c h y , and F o n d a t i o n de Recherche en Hormono log ie , F r e s n e s , France

It has been demonstrated that both hyperglucagonemia and a hyperkinetic circulation are present in patients with cirrhosis. It has therefore been suggested that glucagon may be responsible for the hyperkinetic circulation observed in portal hypertension. This study was undertaken to elucidate the hemodynamic effects of glucagon infusion at physiologic and supraphysiologic doses in conscious rats with portal hypertension due to cirrhosis.

Cardiac output and splanchnic organ blood flows were measured by the radioactive microsphere method before and 30 min after glucagon infusion at doses of 2, 5, and i0 ng/min. Infusion of glucagon raised serum glucagon from basal level of 92 ± 49 pg/ml to 399 ± 252, 1151 ± 385, and 1898 ± 929 pg/ml, respectively in sham-operated rats and from 743 ± 212 pg/min to 1497 ± 558, 1583 ± 695, and 2957 ± 1837 pg/min, respectively in cirrhotic animals at 2, 5, and i0 ng/min doses. In both groups, cardiac output did not change after glucagon infusion at 2 and 5 ng/min doses, suggesting that factors other than glucagon are primarily responsible for the systemic hyperdynamic state of cirrhosis. Portal tributary blood flow increased significantly after glucagon infusion in sham-operated rats from 4.4 ± 0.9 to 5.9 ± 1.4 and 7.0 ± 1.2 ml/min.100 g body wt, respectively; and in cirrhotic rats from 8.3 ± 2.2 to 9.1 ± 2.4 and 10.9 ± 1.9 ml/min.lO0 g body wt, at doses of 5 and i0 ng/min, respectively. However, portal tributary blood flow did not change after glucagon infusion at the physiologic dose of 2 ng/min.

This study shows that glucagon at a physiologic dose does not increase splanchnic blood flow although it increases it at supraphysiologic doses. The discrepancy between blood glucagon levels and splanchnic hemodynamic responses suggests that glucagon plays only a minor role in the hyperdynamic state of the splanchnic circulation of cirrhosis.

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