Antigenic determinants of proteins of defined sequences

Cytotoxic and helper T-lymphocyte responses to antibody recognition regions on influenza virus hemagglutinin

We have previously localized and synthesized twelve antibody recognition sites on influenza virus hemagglutinin (HA). These peptides correspond to exposed surface areas in the 3-D structure of HA. Using intact X31 virus as the immunogen, we have determined the recognition of these synthetic peptides by proliferative T-helper lymphocytes (ThL), delayed type hypersensitivity (DTH), and cytotoxic T-lymphocytes (CTL) responses. The responses to the individual determinants in each of these immune compartments were under separate Ir gene control. Conversely, using the peptides as immunogens, we have determined the ability of various peptide-specific antibodies (in outbred mice) and ThLs (in H-2k, H-2d, H-2s and H-2b mice) to recognize intact virus. Whereas most of the peptides primed the mice for an anti-peptide proliferative ThL response, only very few of these cross-reacted with the virus. The identity of the peptide(s) eliciting virus cross-reactive ThLs varied with the strain. The importance of antibody, ThL, CTL and DTH responses in protection against viral infection and in vaccine design is discussed.

RISH IV. Immunoglobulin diversity

RISH considers that cell surface components involved in like cell identification are not involved in the structure of the plasma membrane per se and are attached to a part of their mRNA. the mRNA then acts as a template for the synthesis of DNA. Thus the component at the cell surface is attached to an RNA/DNA receptor. If there is a conformational change in the component (antigen) this will cause a distortion in its RNA/DNA receptor. This distortion is then detected by a tissue specific T lymphocyte which removes all or part of the RNA/DNA receptor from the aberrant cell and the lymphocyte then undergoes replication. During this process receptor RNA/DNA is incorporated into the daughter lymphocyte which becomes a B lymphocyte/plasma cell producing immunoglobulin. The initial tissue specific T lymphocyte becomes a dual functional helper/suppressor cell. The B lymphocytes use the RNA from the RNA/DNA receptor to synthesize the variable region of the first antibody, IgM1. This antibody (IgM1) does not react with the antigen, ie. the distorted component, or the receptor RNA, but with receptor DNA. The DNA of the receptor base pairs with its complementary strand in the B lymphocyte, and the complementary DNA acts as a template for mRNA synthesis. This results in the production of IgM2 and IgG that can bind the antigen and receptor RNA. These antibodies (IgM1, IgM2 and IgG) when endocytosed by the stimulating cell will also complex cytoplasmic mRNA and nuclear DNA and prevent the synthesis of the antigen that initiated the immune response. If other classes of antibodies are to be produced they will follow a similar pattern (IgM1, IgA and IgG or IgM1, IgE and IgG). From the codons of the known amino acids, the codons for amino acids from translation of the complementary DNA strand have been calculated. The amino acids derived from the complementary codons are considered to represent sequences of amino acids in the antigen as represented by the DNA of an RNA/DNA receptor. For these sequences of amino acids, each has a complementary amino acid as defined by the normal codon. These complementary amino acids are then used in the synthesis of the variable region of the antibody.

The immune response to Epstein-Barr nuclear antigen: conformational and structural features of antibody binding to synthetic peptides

Naturally developing human antibodies to the Epstein-Barr nuclear antigen recognize synthetic peptides containing sequences from the unusual glycine-alanine region of this protein. We tested antibody binding to a series of peptides of from five to 20 amino acids in length. Peptides as small as seven amino acids could bind but optimal results required chain lengths of 15. Binding was extremely sensitive to small changes in the length and sequence of the peptide, and also to the temp of the reaction. The changes can be ascribed to two factors: (1) deletion of the site of antigen binding and (2) loss of peptide secondary structure.

Use of peptide synthesis to probe viral antigens for epitopes to a resolution of a single amino acid

A procedure is described for rapid concurrent synthesis on solid supports of hundreds of peptides, of sufficient purity to react in an enzyme-linked immunosorbent assay. Interaction of synthesized peptides with antibodies is then easily detected without removing them from the support. In this manner an immunogenic epitope of the immunologically important coat protein of foot-and-mouth disease virus (type O1) is located with a resolution of seven amino acids, corresponding to amino acids 146-152 of that protein. Then, a complete replacement set of peptides in which all 20 amino acids were substituted in turn at every position within the epitope was synthesized, and the particular amino acids conferring specificity for the reaction with antibody were determined. It was found that the leucine residues at positions 148 and 151 were essential for reaction with antisera raised against intact virus. A lesser contribution was derived from the glutamine and alanine residues at positions 149 and 152, respectively. Aside from the practical significance for locating and examining epitopes at high resolution, these findings may lead to better understanding of the basis of antigen-antibody interaction and antibody specificity.

A novel approach for localization of the continuous protein antigenic sites by comprehensive synthetic surface scanning: antibody and T-cell activity to several influenza hemagglutinin synthetic sites

The determination in this laboratory of the complete antigenic structures of several proteins initially relied on a multi-approach complex chemical strategy and revealed that antigenic sites are surface locations which could be either 'continuous' or 'discontinuous' in architecture. More recently, we introduced a simplified comprehensive synthetic approach for the localization of the continuous antigenic sites of a protein. The approach depends on the synthesis of consecutive overlapping peptides, of uniform size and overlaps, and encompass the entire protein chain, from the beginning to the end. The latter approach is rather costly and labor-intensive, especially when applied to large protein molecules. All these studies showed, however, that protein antigenic sites occupy surface areas on a protein molecule. In order to render the determination of protein antigenic sites more feasible within a reasonable period of time, we considered that only the protein surface needs to be examined. Thus, for a protein of known three-dimensional structure, the protein surface can be readily screened for the continuous antigenic sites by the systematic synthesis and examination of immunochemical activity of all exposed segments of the protein. We have applied this approach here to influenza A virus hemagglutinin. Twelve peptides (11 reported for the first time here, and one reported previously), representing continuous surface segments of the molecule, have so far been synthesized, purified, characterized and their immunochemical activity studied. The peptides were found to bind anti-viral antibodies raised in outbred mice and antibodies in human sera from individuals that had suffered a recent influenza A infection. In one mouse strain (Balb/c; H-2d) so far examined, several of the peptides stimulated an in vitro proliferative response of T cells from virus (X-31)- primed mice. Finally, antisera to the peptides were raised in mice and, as expected, were found to bind to intact virus. In most cases, anti-peptide antibodies, did not bind disrupted virus. These studies indicate that protein 'continuous' antigenic sites can be localized by systematic synthetic scanning of the surface. It is emphasized that the approach is useful only for the localization of 'continuous' sites. The results also reveal that the antigenic structure of influenza virus hemagglutinin is more complex than has hitherto been suspected.

Chemically synthesized peptides of hepatitis B surface antigen duplicate the d/y specificities and induce subtype-specific antibodies in chimpanzees

Synthetic peptides, predicted from the nucleotide sequence of the S gene of hepatitis B virus were analyzed in terms of the established specificities of the hepatitis B surface antigen. The analysis indicated that the group-specific alpha antigen is composed of at least three nonoverlapping sequences and that a relatively hydrophilic region of the surface antigen protein, spanning amino acid residues 110-137, specifies the major d and y subtype system. The d/y subtype appears to depend on changes in one or more variable amino acids at positions 127, 131, and 134 of the hepatitis B surface antigen protein. Peptide 49 (consisting of amino acid sequences of the y subtype for the region 110-137), coupled to a carrier protein and mixed with an adjuvant, stimulated a brisk anti-y response in chimpanzees, the relevant model of human response to hepatitis B virus immunization and infection. Experimental challenge with homologous hepatitis B virus resulted in a pattern of partial protection. The results offer promise for the application of chemically synthesized peptides as vaccines in the prophylaxis of hepatitis B virus disease.

An antiactin antibody that distinguishes between cytoplasmic and skeletal muscle actins

We elicited antibodies in rabbits to actin purified from body wall muscle of the marine mollusc, Aplysia californica. We found that this antiactin has an unusual specificity: in addition to reacting with the immunogen, it recognizes cytoplasmic vertebrate actins but not myofibrillar actin. Radioimmunoassay showed little or no cross-reaction with actin purified from either chicken gizzard or rabbit skeletal muscle. Immunocytochemical studies with human fibroblasts and L6 myoblasts revealed intense staining of typical cytoplasmic cables. Myofibrils were not stained after treatment of human and frog skeletal muscle with the antibody, although the distribution of immunofluorescence suggested that cytoplasmic actin is associated with membrane systems in the muscle fiber. The antibody may therefore be especially suited for studying the localization of cytoplasmic actin in skeletal muscle cells even in the presence of a great excess of the myofibrillar form.

Localization of Escherichia coli ribosomal protein S4 on the surface of the 30S ribosomal subunit by immuno electron microscopy. I. Distribution of antibody-binding sites as obtained with immunoglobulins and monovalent antibody fragments from various S4-specific antisera

The location of the ribosomal protein S4 on the surface of the 30S subunit of E. coli ribosomes was determined by immuno electron microscopy. Immunoglobulins from six separate S4-specific antisera were investigated. In accordance with earlier findings protein S4 was shown to have an elongated conformation within the antisera. Protein S4 has therefore definitely an extended or fibrous shape in the intact ribosome (Lake et al., 1974; Stöffler and Tischendorf, 1975; Tischendorf et al., 1975). S4 specific antibodies bind at four distinct sites of 30S ribosomal subunits, designated A, B, C and D. Two antibody binding sites (A and B) are located on the "head", they were shown to be separated by 70-85 A. The distance between these sites and the two sites C and D on the "body" of the subunit amounts to at least 90-125 A; hence protein S4 should be extended to a total length of approximately 160-200 A. At least three of the four S4-specific antibody binding sites were observed with antibodies from each of the six investigated. These sites were observed independently of whether isolated S4 protein, an S4-16S rRNA complex or 30S ribosomes were used as the antigen. They could also be visualized with monovalent antibody fragments (Fab). S4-specific antibodies enriched by affinity chromatography bound at identical sites which conclusively ensures that antibody binding at these sites is specific for protein S4 and is not due to the presence of contaminating antibodies in the intact ribosome. The implications of these results with respect of the correlation of each of the sites to their respective antigenically active fragments within protein S4 are discussed.