Immunological studies with synthetic polypeptides

Preparation, properties, and applications of carbohydrate conjugates of proteins and lipids

As a result of the growing awareness of the involvement of the oligosaccharide moieties of glycoproteins and glycolipids in cell surface recognition and binding phenomena, a wide variety of methods have been developed, many quite recently, for preparing glycoconjugates. The chemical methods used for the attachment of sugars and certain hydrophilic polymers (e.g., polyethylene glycol) are discussed, as are the effects of such modifications on various properties of the protein (immune response, thermal stability and resistance to proteolysis, clearance, and specific binding to cell surface receptors). Enzymatic approaches to glycoconjugate preparation are also considered, and several examples are given of the preparation of model glycolipids, useful in studying cell surface phenomena. In a final section, three areas are considered in which rapid advances seem likely to occur: improved methods for the preparation of glycoconjugates; direct modification of cell surface glycoconjugates; and modification for the purpose of studying location and environment of membrane glycoconjugates.

Polyalanylation of bovine somatotropin peptide 96-133

Polyalanylation of bovine somatotropin peptide 96-133 has been investigated. Polyalanylated peptides contained an average of 3-50 additional alanines per mole of peptide. As indicated by circular dichroism, the parent peptide and the polyalanylated peptides were helical at pH 4.0. The biological activity per mole of peptide with 50 additional alanies was approximately the same as that of the parent peptide.

Reconstitution of genetically regulated responses against random and ordered synthetic polypeptides by methylated bovine serum albumin as analyzed by isoelectric focusing

In previous publications it was shown by avidity measurements, cross-reactivity patterns and genetic analyses, that the tetrapeptide T-T-G-G is the immuno-dominant epitope of the synthetic polypeptide (T, G)-A--L. In the present study this close immunological relationship between the random multichain copolymer (T, G)-A--L and the ordered analogue (T-T-G-G)-A--L is extended by two additional criteria. First, the immune response against (T-T-G-G)-A--L in H-2k nonresponder mouse strains can be reconstituted to high antibody levels by complexing this antigen to methylated bovine serum albumin, as was tested earlier for (T,G)-A--L. The antibodies elicited upon reconstitution in both antigenic systems are directed mainly against the same determinant, T-T-G-G. Second, isoelectric focusing analysis of specific antisera developed with radiolabeled antigen revealed restricted 7 S IgG antibody populations in high responder and reconstituted high and low responder mice. The spectra were found to be of similar complexity in the (T,G)-A--L and in the (T-T-G-G)-A--L system. From these data it was concluded that the repertoires of specific B cells to T-T-G-G are very similar in high and low responder strains, and the defect in the H-2k low responder systems should be located at the level of T-B cell cooperation.

The biosynthesis of multi-L-arginyl-poly(L-aspartic acid) in the filamentous cyanobacterium Anabaena cylindrica

The cyanobacteria produce multi-L-arginyl-poly (aspartic acid), a high molecular weight (Mr=25 000-125 000) branched polypeptide consisting of a poly(aspartic acid) core with L-arginyl residues peptide bonded to each free carboxyl group of the poly(aspartic acid). An enzyme which will elongate Arg-poly(Asp) has been isolated and purified 92-fold from the filamentous cyanobacterium Anabaena cylindrica. The enzyme incorporates arginine and aspartic acid into Arg-poly(Asp) in a reaction which requires ATP, KCl, MgCl2, and a sulfhydryl reagent. The enzymatic incorporation of arginine is dependent upon the presence of L-aspartic acid but not visa versa, a finding which suggests the order of amino acid addition to the branched polypeptide-aspartic acid is added to the core followed by the attachment of an arginine branch. The elongation of Arg-poly(Asp) in-vitro is insensitive to the addition of protein synthesis inhibitors and to the addition of nucleases. These findings support the notion previosly suggested from in-vivo studies that Arg-poly(Asp) is synthesized via a non-ribosomal route and also demonstrate that amino-acetylated transfer-RNAs play no part in at least one step of the biosynthetic mechanism.

Determination of the structure of the novel polypeptide containing aspartic acid and arginine which is found in Cyanobacteria

The polypeptide contained in the cyanophycin granule, a characteristic cyanobacterial subcellular inclusion, is shown to be a highly branched structure consisting of a polyaspartic acid core to which arginyl residues are attached at each free carboxyl group of the polyaspartic acid. The evidence supporting such a model includes: (i) The resistance of the polypeptide to a variety of enzymatic procedures commonly used to degrade linear polypeptide chains. (ii) The inability to degrade the polypeptide from the amino terminal using sequential Edman degradation. (iii) The preferential relase of arginine following hydrolysis of the polypeptide in dilute acid (0.03 M acetic acid, 105 degrees C). (iv) The demonstration by chemical linkage analysis that both the carboxyl groups of aspartic acid are unavailable for reduction and must therefore by involved in covalent linkages and that many arginyl residues can be reduced and therefore must not be involved in covalent linkage. (v) The removal of approximately 75% of the arginine from the polypeptide by chemical treatment of the polypeptide using methods designed to cleave carboxyl-terminal amino acids. The highly branched structure of the cyanophycin granule polypeptide is similar in form to synthetically produced multichain polyamino acids, and using the nomenclature for describing multichain polyamino acids, it is proposed that the cyanophycin granule polypeptide be called multi-L-arginyl- -polyaspartic acid.

Synthetic antigens. II. Immunogenic, antigenic and adjuvant properties of a copolymer of styrene and maleic anhydride

Immunogenic, antigenic and adjuvant properties of a polyanionic copolymer of styrene and maleic anhydride (PSM) are described. The results obtained showed that PSM was immunogenic in BALB/c mice when administered without adjuvant, the optimal dose being 0.01 mug/mouse. Antibodies could be detected only by precipitation in gel but not by agglutination. High molecular weight polymer (290 000 daltons) was a stronger immunogen and antigen than copolymers of lower molecular weights (85 000-210 000 daltons). PSM also showed adjuvant activity and enhanced the humoral response of mice against sheep red blood cells. Adjuvanticity was found only when 1 mug of PSM/mouse was applied. The results obtained suggest that PSM interacts with B rather than T cells.

Antibody response of inbred mouse strains to ordered tetrapeptides of tyrosine and glutamic acid attached to multichain polyalanine or polyproline. Tyr-Tyr-Glu-Glu is a major determinant of the random poly-(Tyr, Glu)-polyDLAla--polyLys

Five inbred mouse strains which represent high and low responders to the random synthetic polypeptide poly(LTyr,LGlu)-polyDLAla--polyLLys, designated (T, G)-A--L, to which the immune response is controlled by an H-2-linked gene, were immunized with three ordered tetrapeptides composed of tyrosine and glutamic acid attached either to multichain poly-DL-alanine or to polyproline. Only one of the three antigenic determinants, namely tyrosyl-tyrosyl-glytamyl-glutamic acid (T-T-G-G), resembled the random peptide (T, G) in the pattern of immune responses elicited against it, and in the cross-reactivity of the specific antibodies with (T, G)-A--L. The immune response pattern to the other two ordered tetrapeptides, T-G-T-G and G-T-T-G, was different from that obtained with (T, G)-A--L, and no cross-reactivity was detected between the antibodies provoked with these peptides and (T, G)-A--L. Thus, it is suggested that T-T-G-G is a major determinant in the random (T, G)-A--L.

Thymus independence of a collagen-like synthetic polypeptide and of collagen, and the need for thymus and bone marrow-cell cooperation in the immune response to gelatin

Several inbred mouse strains were screened for their ability to respond to the ordered periodic collagen-like polymer (Pro-Gly-Pro)(n), to the random copolymer (Pro(66), Gly(34))(n), to the protein conjugate Pro-Gly-Pro-ovalbumin, to rat tail tendon collagen, rat tail tendon gelatin, and to Ascaris cuticle collagen. Differences were obtained in the magnitude of the antibody titers towards the above immunogens among the strains tested. The level of the response to the ordered polymer (Pro-Gly-Pro)(n) was not similar to that towards the random (Pro(66), Gly(34))(n), confirming differences in the antigenic determinants of the two immunogens. The role of the thymus in the immune response to (Pro-Gly-Pro)(n) and (Pro(66), Gly(34))(n) as well as to two collagens and gelatin, was studied in order to find out a possible correlation with the structural features of the immunogens. Heavily irradiated recipients were injected with syngeneic thymocytes, marrow cells, or a mixture of both cell populations and were immunized with the above-mentioned antigens. An efficient immune response to the ordered collagen-like (Pro-Gly-Pro)(n) was obtained in the absence of transferred thymocytes. The thymus independence of (Pro-Gly-Pro)(n) was confirmed when thymectomized irradiated mice were used as recipients. In contrast with these results, cooperation between thymus and marrow cells was necessary in order to elicit an immune response to (Pro(56), Gly(34))(n). Similarly, the immune response to the triple helical collagen was found to be independent of the thymus, whereas for an effective response to its denatured product, gelatin, thymus cells were required. These findings indicate that a unique three-dimensional structure of immunogens possessing repeating antigenic determinants plays an important role in determining the need for cell to cell interaction in order to elicit an antibody response.

Sequence differences of Escherichia coli 30S ribosomal proteins as determined by immunochemical methods

Antisera specific for each of the 21 homogenous ribosomal proteins from 30S subunits of Escherichia coli were used to investigate, by immunodiffusion and immunoprecipitation, whether there are any extensive sequence homologies among these proteins. No immunological crossreactions were detected between any of the proteins. Therefore, we conclude that no significant common sequences exist among any of the 21 30S ribosomal proteins of E. coli.

Specific immune response genes of the guinea pig. I. Dominant genetic control of immune responsiveness to copolymers of L-glutamic acid and L-alanine and L-glutamic acid and L-tyrosine

The immunogenicity of three random copolymers of amino acids with L-glutamic acid and L-alanine (GA), L-glutamic acid and L-tyrosine (GT), or L-glutamic acid, L-alanine, and L-tyrosine (GAT), administered in complete Freund's adjuvant, was studied in several inbred and random-bred guinea pig strains. The animals were tested for delayed sensitivity and their sera were assayed for the presence of antibody directed against the immunizing polymer. All of the guinea pigs developing delayed hypersensitivity also had significant antibody levels in their sera. Inbred strain 2 guinea pigs responded to immunization with GA, but failed to form detectable responses to GT. Inbred strain 13 animals, on the other hand, responded to GT, but not to GA. The (2 x 13)F(1) hybrids responded to both GA and GT with both delayed hypersensitivity and circulating antibody. Thus, the ability of these inbred guinea pigs to respond immunologically to GA or GT is controlled by distinct autosomal dominant genes. A variable percentage of random-bred guinea pigs, depending on their source as well as their strain, responded to immunization with GA and with GT. All guinea pigs, both inbred and random bred, responded to immunization with GAT. The ability to respond immunologically to GAT, therefore, does not seem to be under simple genetic control. However, the levels of anti-GAT antibody found in the sera of animals lacking the ability to respond to GA were much lower than those detected in GA responder animals.

Antibodies reactive with native lysozyme elicited by a completely synthetic antigen

A synthetic peptide consisting of the aminoacid sequence of residues 64-82 of lysozyme, with alanine replacing cysteine as residue 76, was prepared by the solid-phase technique. Mild reduction followed by reoxidation in air of the deprotected peptide led to the formation of a closed loop containing an intrachain disulfide bond. A conjugate consisting of this "loop" attached to multi-poly(DL-alanyl)-poly(L-lysine) elicited, in rabbits and goats, the formation of antibodies capable of reacting with lysozyme and with the loop peptide prepared from it. These immunological interactions can be inhibited by either lysozyme or the loop peptide, but not by the performic acid-oxidized open-chain peptide. Thus, the antibodies elicited by the completely synthetic antigen show specificity toward the "loop" structure (residues 64-80) of native lysozyme.

Contribution of bone marrow cells and lack of expression of thymocytes in genetic controls of immune responses for two immunopotent regions within poly-(Phe,Glu)-poly-Pro--poly-Lys in inbred mouse strains

Previous cellular studies on the genetic regulation of immunological responsiveness for two immunopotent regions within the branched chain synthetic polypeptide (Phe, G)-Pro--L demonstrated a direct correlation between the number of detectable immunocompetent splenic precursor cells and the response patterns of SJL, DBA/1, and F(1) mice (21). In order to establish the cellular origin(s) of the genetic defect, the present study first demonstrated that thymus and bone marrow cell cooperation was required for (Phe, G)- and Pro--L-specific immune responses. Secondly, limiting dilution experiments, in which several graded and limiting inocula of marrow cells were mixed with a non-limiting number of 10(8) thymocytes and injected into irradiated, syngeneic recipients, indicated that the low responsiveness of the SJL and DBA/1 strains to the (Phe, G) and Pro--L specificities, respectively, could be attributed to a reduced number of precursor cells found in bone marrow. About five times more marrow precursors were detected in SJL mice for Pro--L than for (Phe, G), whereas about five times as many precursor cells were estimated for (Phe, G) as for Pro--L in the DBA/1 strain. These differences are similar to those obtained using spleen cells from unimmunized SJL and DBA/1 donors (21), and indicate that these genetically determined variations in responsiveness can be accounted for by differences in the frequencies of monospecific populations of immunocompetent cells present in bone marrow. In contrast, limiting dilution transfers of thymocytes or thymus-derived cells with an excess of syngeneic marrow cells resulted in equally frequent (Phe, G) and Pro--L responses for both SJL ad DBA/1 strains. This finding in conjunction with the observation that the generation of (Phe, G)- and Pro--L-specific responses were associated in individual recipients injected with limiting inocula of thymocytes indicated that a single population of thymocytes was stimulated by (Phe,G)-Pro--L. Therefore, it is improbable that the thymic population of immunocompetent cells contributes to expression of these genetically controlled defects.

Immune response to chemically modified flagellin. I. Induction of antibody tolerance to flagellin by acetoacetylated derivatives of the protein

Flagellin (mol. wt. 40,000) from S. adelaide organisms was acetoacetylated to varying extents with diketene (acetoacetic anhydride). Chemical studies demonstrated that the amino groups of flagellin were more readily acetoacetylated than the hydroxyl groups. Several antigenic tests revealed that as flagellin was acetoacetylated to increasing extents there was a steady decline in the affinity of the molecule for anti-flagellin antibodies. Loss in antigenic activity following acetoacetylation was not related to the number of acetoacetyl groups attached but was determined by the type of residue substituted. Reactive lysine residues were much less important anti-genically than easily substituted hydroxyl groups. Acetoacetylation very readily destroyed the antibody-forming capacity of flagellin in rats. This fall in immunogenicity was related to the antigenic activity of the preparations. In fact, only a 40% reduction in the antigenic activity of flagellin produced a 90-95% reduction in primary antibody formation. The more heavily acetoacetylated flagellins produced no detectable antibody and, in fact, rendered adult rats tolerant (in terms of antibody formation) to a subsequent challenge of flagellin. Tolerance was induced by acetoacetylated flagellins which had drastically reduced affinities for anti-flagellin antibodies. These results were interpreted as indicating that the affinity of antigen for receptors on cells appears to be of crucial importance in determining whether antibody formation or immunological tolerance (antibody suppression) occurs.

Studies on the immune response to a characterized antigenic determinant of the tobacco mosaic virus protein

THE FOLLOWING PEPTIDES HAVE PREVIOUSLY BEEN SHOWN TO BIND SPECIFICALLY WITH ANTIBODIES TO TMVP: (a) An eicosapeptide representing residues 93-112 of TMVP and having the sequence Ileu-Ileu-Glu-Val-Glu-AspNH(2)-GluNH(2)-Ala-AspNH(2)-Pro-Thr-Thr-Ala-Glu-Thr-Leu-Asp-Ala-Thr-Arg. (b) Its C-terminal decapeptide. (c) Its C-terminal pentapeptide. (d) N-octanoyl-C-terminal-tripeptide. (e) (Lys)(4)-C-terminal-pentapeptide. (f) (Lys)(7) C-terminal-pentapeptide. The present communication deals with the investigation of several parameters of the immunological activity of the peptides. The results show that none of the peptides tested were immunogenic in guinea pigs, nor did they stimulate the incorporation of (14)C-thymidine by spleen cells derived from TMVP-primed animals. Results also showed that all of the peptides tested could elicit specific delayed and immediate skin reactions in TMVP-sensitized guinea pigs, and furthermore, that the peptides could specifically inhibit the migration of peritoneal exudate cells derived from these animals. The elicitation of delayed skin reactions and the ability to inhibit migration of peritoneal exudate cells were independent of carrier specificity.