SUMMARYA panel of eight neutralizing monoclonal antibodies (MAbs) against the fusion (F) protein of Newcastle disease virus (NDV) has been shown to locate a major antigenic site on the basis of competitive binding assay and additivity index studies. Five epitopes (A 1 to AS) have been located within this site on the F protein of the Beaudette C strain of NDV on the basis of cross-resistance plaque assays of MAb-resistant mutants raised against these MAbs. Epitopes A1, A4 and A5 are distinct; epitope A2 partially overlaps epitope A3. Nucleotide sequence analysis of the F genes of MAbresistant mutants showed that each predicted single amino acid substitutions ranging from amino acid residues 157 to 171 for epitope A4 and at residues 72, 78, 79 and 343 for epitopes A 1, A2, A3 and A5 respectively. These locations indicate that both the F 1 and F2 fragments are involved in the formation of a single antigenic site and suggest the involvement of extensive protein folding in the active form of this F protein.

Nine neutralizing monoclonal antibodies (MAbs), each of which react with the haemagglutinin-neuraminidase (HN) glycoprotein of the Beaudette C strain of Newcastle disease virus (NDV), have been used in competitive binding assays to delineate three non-overlapping antigenic sites A, B and C. Epitopes within these sites have been identified on the basis of cross-reactivity of MAb-resistant mutants against the panel of MAbs, determined by plaque assays and Western blotting. Site A contains three non-overlapping epitopes (A1, A2 and A3). A1 is the only linear epitope; all remaining epitopes are conformational. MAbs which react with epitopes A2 and A3 inhibit neuraminidase activity (NA) when assayed with neuraminlactose. Site B contains three partially overlapping epitopes (B1, B2 and B3) and site C is represented by a single epitope (C1). HN gene sequence analysis of MAb-resistant mutants showed that they each had only single amino acid substitutions which range from amino acid residues 347-460 for site A, 284-325 for site B, and at 481 for the C1 epitope. The apparent molecular mass of the HN glycoprotein of one mutant was increased from 72 to 75 kDa. This correlates well with the creation of an additional potential glycosylation site in this mutant from Asn-Ser-Pro(325) to Asn-Ser-Ser(325).

Bifunctional alkylating agents, such as those based on nitrogen mustard, form important parts of many anti-cancer chemotherapy protocols and are responsible for increased incidences of secondary tumors in successfully treated patients. These drugs generally form a majority of monofunctional DNA adducts, although the bifunctional adducts appear to be necessary for their powerful cytotoxic and antitumor effects. The relative importance of bifunctional as opposed to monofunctional adducts in the varied biological consequences of drug exposure has not been studied in detail, particularly in relation to the role and specificity of biochemical responses to therapy-related DNA damage. A simple method is described for the preparation of useful quantities of a pure monofunctional derivative of the nitrogen mustard-based drug melphalan. Monohydroxymelphalan was prepared by partial hydrolysis, purified by reversed phase chromatography, and characterized by MS, NMR, and HPLC. Contamination with melphalan was