Immunoelectrophoretic analysis of the antigenic structure of Sh. sonnei]

The authors studied the antigenic composition of 105 Sh. sonnei strains freshly isolated from patients suffering from acute dysentery and carriers. Immunophoregrams of pure S-and R-forms species were obtained. Up to 13 antigens differing by electrophoretic and diffusion mobility and immunological specificity were revealed among soluble Sh. sonnei antigens The position of common and specific antigens was determined on the immunophoregram. Along with the thermostable somatic O-antigen detected at the I phase of the S-forms, and two thermolabile O-antigen components at the II phase, and the R-forms, there was revealed a surface, relatively thermolabile, K-antigen of A-type capable of agglutinating live bacteria in the O-antiserum; position of the latter on the immunophoregram was also determined.     

The antigenic structure of poliovirus

We have solved the structure of the Mahoney strain of type 1 and the Sabin (attenuated vaccine) strain of type 3 poliovirus by X-ray crystallographic methods. By providing a three-dimensional framework for the interpretation of a wealth of experimental data, the structures have yielded insight into the architecture and assembly of the virus particle, have provided information regarding the entry of virus into susceptible cells, and defined the sites on the virus particle that are recognized by neutralizing monoclonal antibodies. Thus locating mutations in variants selected for resistance to neutralizing monoclonal antibodies has defined three antigenic sites of the surface of the virion, and provided clues as to the mechanisms by which viruses escape neutralization. Finally, comparison of the structures of the two strains, together with analysis of sequences of many poliovirus strains, have begun to define the structural changes associated with serotypic differences between polioviruses.     

The antigenic structure of bovine serum albumin. Evidence for multiple, different, domain-specific antigenic determinants.

Using antiserum to native bovine albumin and antigenically active fragments of the protein, we have isolated antibodies directed to each of the three domains and to several subdomains of the albumin molecule. Using albumin and these fragments as inhibitors of the reaction between 125I-albumin and any given antibody population, we have demonstrated that: (a) each domain of albumin is antigenically distinct from each of the other domains; (b) each domain possesses a minimum of two different antigenic determinants; and (c) the entire albumin molecule possesses a minimum of six different, nonrepeating, antigenic determinants.     

The precise and entire antigenic structure of native lysozyme.

The exact boundary, residue, conformational and directional definitions of the three antigenic sites of native hen's egg-white lysozyme are described. The results clearly reveal that the three antigenic sites account quantitatively for the total antigenic reactivity of the protein. Thus the entire antigenic structure of lysozyme has now been precisely determined and is briefly discussed here, together with the power of the surface-stimulation synthetic concept.     

Revision of the antigenic structure of genus Listeria

O-antigenic structure of genus Listeria was studied, using antisera (obtained from rabbits) against different O-antigens of reference strains of each serovar. The titres of sera were determined by agglutination using antigens of the same reference strains as well. Some differences from the actual scheme were found: serum antifactor-IX gave a lower titre than expected against antigens 4ab and 6b, while the titre observed against antigen 4b was higher than the expected in this case. Serum antifactor-VIII presented a higher titre than could be expected against antigen 6b. The strains of serovars 4d and 4e used in this experience were impossible to distinguish, and could have been classified in the same serovar. We could not obtain serum antifactor-XI from serovar 6b after several trials. From these differences we propose some modifications of the current antigenic scheme of genus Listeria.     

The antigenic structure ofFrancisella tularensis

The ether antigen ofFrancisella tularensis was fractionated using DEAE-cellulose and CM-cellulose chromatography, and Sephadex G-200 gel filtration. The CM-cellulose chromatography did not appear to be a suitable method for separation of individual components of the complex ether antigen. Most of the polysaccharide material and substances with a high phosphorus content were eluted already in the first peak of the elution curve. This method could be used only to separate a component, yielding one immunoelectrophoretic precipitin line, localized towards the cathode. On the other hand, the DEAE-cellulose chromatography, and particularly the Sephadex G-200 gel filtration (especially when recycling was introduced), yielded a clear separation of relatively clean components of the ether antigen. The present work provides a comparison between the immunochemical (immunoelectrophoretic) properties of fractions obtained by these methods and components isolated by salting out with ammonium sulphate, ethanol or trichloracetic acid precipitation.     

The antigenic structure ofFrancisella tularensis

The ether antigen ofFrancisella tularensis was submitted to fractionation using ammonium sulphate, ethanol and trichloracetic acid (TCA). A simple antigenic mixture was obtained by this fractionation from the original complex ether antigen. However, no separation of antigenically and chemically homogenous substances was achieved, by this procedure. The precipitation with TCA permitted the separation of an antigenic component that was found to be identical with the phenol antigen or its component migrating faster towards cathode in electrophoresis. The sediment obtained possessed common properties with the precipitate obtained by ethanol precipitation. The fraction having the highest anodic mobility could be obtained by salting out the original antigen with ammonium sulphate to 50% saturation. By increasing the concentration of ammonium sulphate to 60% saturation, all components of the ether antigen could be precipitated. The number of precipitation lines in the original antigen and its fractions depends both on the concentration of antigen and the quality of antisera.     

Monoclonal antibodies as probes of the antigenic structure of tobacco mosaic virus.

The antigenic structure of tobacco mosaic virus has been analysed by measuring the ability of nine monoclonal antibodies to distinguish between wild-type virus and 13 mutants showing single and double amino acid substitutions in the coat protein. Although the majority of antibodies detected those substitutions that were located at the outer surface of the virion, some of them also recognized conformation alterations induced by exchanges occurring deep inside the subunit. In the case of five mutants, the antibody reactivity was reduced compared with wild-type virus, while in the case of three others, it was significantly higher. Each monoclonal antibody possessed a unique discrimination pattern with respect to the different substitutions. The simultaneous presence of two exchanges led to the complete disappearance of any binding with six of the nine antibodies and to reduced binding with three others. The superior discriminatory capacity of monoclonal antibodies compared with polyclonal antisera was demonstrated by the fact that three exchanges not detected with antisera were found to alter the antigenicity when tested with monoclonal antibodies.