Potato virus Y group C isolates (PVY C ) have been characterized according to biological, molecular and genetic criteria. Two genetic strains, PVY C1 and PVY C2, were identified on the basis of genetic distances (among them and other PVY strains), host range (ability or inability to infect pepper), MAb response (ELISA recognition with MAb 10E3) and

Potato virus Y (PVY) isolates have been classified into genetic strains by a host-independent criterion using a molecular typing method. The method used extracts from infected tissue, and included immunocapture-RT-PCR-RFLP analysis using 5 different restriction endonucleases (Dde I, Eco RV, Hinf I, Rsa I and Taq I). Genetic distances between the different PVY "restrictotypes" were calculated and used to define the PVY genetic strains. Three main clusters were found: PVYO, PVYN, and non-potato PVY (PVYNP), in good agreement with classical PVY strain definitions that combine different biological criteria. Our approach was incomparably quicker and more reliable and reproducible than biotyping. The potential of this approach for very quick, simple and automatable molecular epidemiological studies is discussed.

Woodchuck hepatitis virus (WHV) and hepatitis B virus (HBVHepatitis B virus (HBV) is a partially double-stranded DNA virus encoding envelope (pre-S1, pre-S2, HBsAg), nucleocapsid (HBcAg, HBeAg), trans-activating (X), and polymerase (Pol) proteins (46). Clinical manifestations of HBV infection range from acute and chronic hepatitis to cirrhosis and hepatocellular carcinoma in humans (6). There are more than 350 million chronic HBV carriers worldwide (54), and HBV is an important cause of morbidity and mortality in the Third World.Several reports have shown that the immune response plays a significant role in both HBV clearance and pathogenesis of hepatitis B (13). A vigorous polyclonal and multispecific cellular response to HBV has been associated with recovery from acute infection. Cytotoxic T lymphocytes (CTLs) and T-helper (Th) cells with specificity for HBcAg and most HBV proteins can be detected in the circulation during acute infection (22,34,37). In contrast, defective CTL and Th cell responses are observed in chronic HBV carriers, except during exacerbation (48). As has been reported for several viral infections, a pref-

No abstract

Interferon-alpha (IFN-alpha) is a key element in the defense against viral infection because, in addition to a direct antiviral effect, it exhibits potent immunostimulatory activity. To investigate the function of this cytokine in the woodchuck model of chronic hepatitis B, the woodchuck IFN-alpha gene (IFNA) family was cloned and examined. The data indicate that this is a multigenic family from which 12 IFNA functional sequences and four pseudogene sequences were isolated. The overall identity of the amino acid sequence among the members of the woodchuck IFN-alpha family is 85%, and the identity with the IFN-alpha family from other species such as mice and humans is 50%. The analysis of hepatic expression of IFNA genes showed that wIFNA5a was the subtype transcribed preferentially in the woodchuck liver. The wIFNA genes transcribed in the liver were tested in an eukaryotic expression system and were found to enhance 2-5-oligoadenylate synthetase (2-5-OAS) mRNA levels and to posses a potent antiviral activity. Cloning of woodchuck IFNA genes will allow testing diverse forms of IFN-alpha delivery as well as different combination therapies in woodchuck hepatitis virus infection, thus providing useful information for the design of new strategies for the treatment of patients with chronic hepatitis B.