In chronic HCV patients, hypobetalipoproteinemia occurs already in the early stages of HCV infection before the development of liver cirrhosis. The correlation between apo B levels and HCV viral load seems to confirm the interaction between hepatitis C infection and beta-lipoprotein metabolism.

Chemical and enzymic cleavages of the F~ subunit of the fusion (F) protein of respiratory syncytial (RS) virus showed that the sequence 184-Gly to 314-Trp reacted with neutralizing monoclonal antibodies (MAbs). Twelve synthetic peptides covering a part of this sequence were analysed for their immunoreactivity with neutralizing MAbs and anti-RS virus rabbit serum. Two sequential antigenic domains corresponding to amino acids 200 to 225 and 255 to 278 were defined with anti-RS virus rabbit serum. The peptides 205-225 and 259-278, belonging to these antigenic domains, inhibited binding to the F protein and the neutralizing activity of the anti-RS virus rabbit serum. One MAb (RS-348) reacted with peptides containing amino acids 200 to 225. Moreover, the peptide 205-225 induced an anti-peptide rabbit serum neutralizing RS virus in vitro. These results indicate that the sequence from residues 200 to 225 was present in one of the immunodominant sites of the F protein.

Addition of heparin to the virus culture inhibited syncytial plaque formation due to respiratory syncytial virus (RSV). Moreover, pretreatment of the virus with heparinase or an inhibitor of heparin, protamine, greatly reduced virus infectivity. Two anti-heparan sulfate antibodies stained RSV-infected cells, but not noninfected cells, by immunofluorescence. One of the antibodies was capable of neutralizing RSV infection in vitro. These results prove that heparin-like structures identified on RSV play a major role in early stages of infection. The RSV G protein is the attachment protein. Both anti-heparan sulfate antibodies specifically bound to this protein. Enzymatic digestion of polysaccharides in the G protein reduced the binding, which indicates that heparin-like structures are on the G protein. Such oligosaccharides may therefore participate in the attachment of the virus.

Chemical cleavage of the VP6 protein of bovine rotavirus showed that VP6-specific monoclonal antibodies (MAbs) reacted with the amino acid sequence between glycine 48 and asparagine 107. Furthermore, three synthetic peptides (amino acids 48 to 64, 60 to 75 and 91 to 108) containing part of this sequence and 22 consecutive overlapping heptapeptides corresponding to the region between amino acids 48 and 75 were analysed for their immunoreactivity using groupspecific MAbs. The MAbs recognized peptides 48-64 and/or 60-75, and a set of overlapping heptapeptides located between residues 53 (asparagine) and 67 (glycine), which have two short sequences in common: IRNW (residues 56 to 59), recognized by MAb RV-133, and (NW)NFD (residues 58/60 to 62), recognized by MAbs RV-50, -1026 and -443. These results indicate that the sequence between amino acid residues 48 and 75 is present in one of the immunodominant sites of VP6.

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