SUMMARYImmunization of mice with the dengue 2 virus (DEN 2)-specified non-structural protein NS1 provided significant protection against intracerebral challenge with the virus in the absence of detectable neutralizing or other anti-virion antibody. NS1, purified from lysates of infected Vero cells by immunoaffinity chromatography, expressed an antigenic site(s) common to each of the four DEN serotypes, and hyperimmunization of rabbits with NS1 stimulated production of complement-fixing (CF) antibody with broad DEN serotype specificity. However, cross-protection was not observed: mice immunized with DEN 2 NS1 developed little or no heterologous CF antibody and were not protected against challenge with neurovirulent DEN 1. Induction of a protective immune response by NS1 suggests that it be considered for incorporation into possible synthetic or recombinant DNA DEN vaccines.Among the mosquito-borne flaviviruses of medical importance, the dengue viruses (DEN) are notable for their global distribution and the frequency of large-scale epidemics caused by them (Halstead, 1980). Attempts to produce a satisfactory DEN vaccine by conventional methods have met with limited success. Attenuated DEN vaccines have been prepared by intracerebral passage in mice (Sabin & Schlesinger, 1945: Schlesinger et al., 1956) but the undesirability of brain tissue in human vaccine preparations has restricted their use. More recently, tissue culture-derived attenuated DEN viruses have been considered as candidate vaccines but inconsistent neutralizing antibody responses as well as occasional genetic instability of the variants have raised doubts about their usefulness Eckels et al., 1984). The chemical synthesis of viral polypeptides or their preparation by recombinant DNA methods may provide novel alternatives for the development of a satisfactory DEN vaccine. The choice of viral proteins for incorporation into such a vaccine will depend on their capacity to stimulate a protective immune response. Although immunity to flavivirus infection has generally been related to the presence of neutralizing antibodies against the virion envelope glycoprotein, we have recently shown that immunization with a yellow fever virus (YF) non-structural (NS) glycoprotein, gp48, protects mice and monkeys against lethal YF infection (Schlesinger et al., 1985(Schlesinger et al., , 1986. This protein, currently designated NS1 (Rice et al., 1985), is highly conserved among flaviviruses and is the soluble complement-fixing (CF) antigen which is expressed on the surface of DEN-infected cells (Cardiff &Lund, 1976;Smith & Wright, 1985). The present report describes antigenic characteristics of dengue 2 virus (DEN 2) NS1 and protection against intracerebral DEN 2 challenge in mice immunized with this protein.Immunoaffinity-purified NS1 was prepared from lysates of DEN 2 (New Guinea-C)-infected Vero cells by modification of a previously described column chromatography method (Schlesinger et al., 1985). Briefly, infected cells grown in roller bottles or in suspension cu...
SUMMARYThe fusion protein of respiratory syncytial virus was purified by affinity chromatography using a monoclonal antibody. Under various conditions the protein was recovered as a 145K dimer or a 70K monomer. The 70K monomer was composed of disulphide-linked fragments of 48K and 23K. Polyclonal rabbit serum produced to the dimerized fusion protein neutralized virus but did not inhibit fusion, while rabbit serum to the 2-mercaptoethanol-treated dimerized protein neutralized virus and inhibited fusion of infected cells. Only the latter serum strongly recognized the 23K fragment when studied by Western blot analysis.
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