Opsonic antibodies evoked by hybrid peptide copies of types 5 and 24 streptococcal M proteins synthesized in tandem

The protective immunogenicity of a hybrid peptide containing tandem copies of types 5 and 24 epitopes was investigated. Carboxy-terminal peptides of the cyanogen bromide-derived fragment 7 (CB7) of type 24 M protein were chemically synthesized, and then extended to include the first 20 residues of the amino-terminus of type 5 M protein. When emulsified in CFA and injected into rabbits without conjugation to a carrier, each of the synthetic hybrid peptides, designated S-M5(1-20)-S-CB7(23-35)C and S-M5(1-20)-S-CB(19-34), evoked opsonic antibodies against both types 5 and 24 streptococci without raising heart tissue-crossreactive immunity. These results suggest that tandem hybrid peptides may provide a new approach to the development of multivalent vaccines, not only to different serotypes of group A streptococci but perhaps also to a variety of other infectious agents.

Peptide-specific antibodies identify the alpha 2 chain as the proteoglycan subunit of type IX collagen

Type IX collagen is a recently characterized product of chondrocytes. The molecules of this collagen are heterotrimers of three genetically distinct polypeptide chains. One of the three chains contains chondroitin and/or dermatan sulfate glycosaminoglycan chains, giving the molecule a proteoglycan character. In fact, Type IX collagen has been identified with the proteoglycan Lt (PG-Lt), first isolated by Noro, A., Kimata, K., Oike, Y., Shinomura, T., Maeda, N., Yano, S., Takahashi, N., and Suzuki, S. (1983) J. Biol. Chem. 258, 9323-9331 from chick embryonic tibia and femur. Based on amino acid sequences predicted from the nucleotide sequences of cDNA and genomic clones specific for two of the chains of Type IX collagen, we have synthesized oligopeptides representing portions of the two chains. In addition, an oligopeptide has been made based on a partial amino acid sequence of the third chain. Antibodies against the synthetic peptides have been generated in rabbits, and the polyclonal sera have allowed identification of the three genetically distinct polypeptide subunits of Type IX collagen. In addition, labeling with [35S]sulfate and treatment with chondroitinase ABC demonstrates that glycosaminoglycan chains are present on the subunit that has been given the designation alpha 2(IX).

Stimulation of interstitial collagenase in co-cultures of rat hepatocytes and sinusoidal cells

Although the fibrosis observed during chronic liver injury is the result of a complex process, the striking accumulation of collagen in end stage liver disease has provoked interest in the mechanisms that regulate both collagen production and degradation in the diseased liver. The present studies have examined the cell interactions that may be important in the regulation of collagen degradation. Although minimal amounts of interstitial collagenase activity were noted in cultures of normal hepatocytes and sinusoidal cells, the co-cultures of these cells in the presence of lipopolysaccharide showed a substantial increase in collagenase activity. When the hepatocytes were obtained from rats that had been treated with carbon tetrachloride in vivo, the enhanced activity seen in the co-cultures did not require the addition of lipopolysaccharide. Further characterization of this interaction suggested that the increase in collagenolytic activity was partially due to the elaboration of soluble factors by the hepatocyte, which stimulated collagenase production by the sinusoidal cell population. Elaboration of collagenase activity by the sinusoidal cells was inhibited by cycloheximide, suggesting that protein synthesis was required. The proteolytic activity was abrogated by inhibitors of metalloproteinases but not by serine or thiol proteinase inhibitors. The degradation products of type I collagen were typical of the expected products seen with vertebrate collagenases. Thus, it appears that the increased collagenolytic activity detected in this co-culture system is attributable to the production of interstitial collagenase by the sinusoidal cell population. Such cell-cell interactions may play an important role in the maintenance of normal connective tissue structure of the liver during disease processes.

Protective and nonprotective epitopes of chemically synthesized peptides of the NH2-terminal region of type 6 streptococcal M protein

The protective immunogenicity of chemically synthesized copies of the NH2-terminal region of type 6 streptococcal M protein was investigated. Four overlapping peptides were synthesized by copying residues 1-20, 10-20, 12-31, and 22-31. Rabbit antisera raised against whole cells of type 6 streptococci reacted at high dilutions (1/12,800 to 1/51,200) with S-M6(1-20) and S-M6(10-20), and at low dilutions (1/100-1/800) with S-M6(12-31) and S-M6(22-31), indicating that the NH2-terminal region of type 6 M protein bears immunodominant epitopes. When covalently linked to tetanus toxoid and emulsified in complete Freund's adjuvant, the synthetic peptides S-M6(1-20), S-M6(10-20), and S-M6(12-31), but not S-M6(22-31), evoked type-specific opsonic antibodies against type 6 streptococci. Although the immune sera reacted in low dilutions by enzyme linked immunoabsorbent assay (ELISA) with the heterologous M protein polypeptides pep M5, pep M19, and pep M24, they failed to opsonize the streptococci from which these M protein polypeptides were derived. Each of the immune sera reacted in high dilution by ELISA with the respective immunizing peptides. All except those against S-M6(22-31) also reacted with pep M6. None of the immune sera reacted with human cardiac tissue by immunofluorescence or with muscle myosin by ELISA. The pattern of the inhibition of opsonization by each of the synthetic peptides of each of the immune sera indicates the presence of at least three protective epitopes in the NH2-terminal region of type 6 M protein. Our results indicate that the NH2-terminal region of type 6 M protein contains both protective and nonprotective epitopes, and chemically synthesized copies of this region lack cardiac tissue cross-reactive epitopes. These studies hold promise for the development of safe and effective vaccines against group A streptococci, especially against the strains giving rise to rheumatic fever and rheumatic heart disease.

Protective and nonprotective epitopes of chemically synthesized peptides of the NH2-terminal region of type 6 streptococcal M protein

The protective immunogenicity of chemically synthesized copies of the NH2-terminal region of type 6 streptococcal M protein was investigated. Four overlapping peptides were synthesized by copying residues 1-20, 10-20, 12-31, and 22-31. Rabbit antisera raised against whole cells of type 6 streptococci reacted at high dilutions (1/12,800 to 1/51,200) with S-M6(1-20) and S-M6(10-20), and at low dilutions (1/100-1/800) with S-M6(12-31) and S-M6(22-31), indicating that the NH2-terminal region of type 6 M protein bears immunodominant epitopes. When covalently linked to tetanus toxoid and emulsified in complete Freund's adjuvant, the synthetic peptides S-M6(1-20), S-M6(10-20), and S-M6(12-31), but not S-M6(22-31), evoked type-specific opsonic antibodies against type 6 streptococci. Although the immune sera reacted in low dilutions by enzyme linked immunoabsorbent assay (ELISA) with the heterologous M protein polypeptides pep M5, pep M19, and pep M24, they failed to opsonize the streptococci from which these M protein polypeptides were derived. Each of the immune sera reacted in high dilution by ELISA with the respective immunizing peptides. All except those against S-M6(22-31) also reacted with pep M6. None of the immune sera reacted with human cardiac tissue by immunofluorescence or with muscle myosin by ELISA. The pattern of the inhibition of opsonization by each of the synthetic peptides of each of the immune sera indicates the presence of at least three protective epitopes in the NH2-terminal region of type 6 M protein. Our results indicate that the NH2-terminal region of type 6 M protein contains both protective and nonprotective epitopes, and chemically synthesized copies of this region lack cardiac tissue cross-reactive epitopes. These studies hold promise for the development of safe and effective vaccines against group A streptococci, especially against the strains giving rise to rheumatic fever and rheumatic heart disease.

Profiles of steady state levels of messenger RNAs coding for type I procollagen, elastin, and fibronectin in hamster lungs undergoing bleomycin-induced interstitial pulmonary fibrosis

We have characterized the messenger RNAs (mRNAs) coding for procollagen alpha 1(I), elastin, fibronectin, and actin in the lungs of Syrian golden hamsters by Northern blot analyses. While elastin, fibronectin, and beta-actin were each coded for by a single mRNA species of 4.1 kilobases (kb), 9.1 kb, and 2.1 kb in size, respectively, we identified a major (5.4 kb) and a minor (6.5 kb) procollagen alpha 1(I) mRNA species in the hamster lungs. The mRNAs for the three extracellular matrix proteins showed increased accumulation followed by steady decline in the bleomycin-treated lungs. There were significant differences among the three mRNAs in the relative increase and the time of maximum accumulation. After reaching the peak levels between 2-3 wk posttreatment, the levels of procollagen alpha 1(I) and elastin mRNAs declined to near normal values around the fourth week. In contrast, the accumulation of fibronectin mRNA was maximum in the first week after bleomycin treatment. The procollagen alpha 1(I) mRNA accumulated most dramatically (sevenfold above the levels in the untreated animals) compared with a five-fold increase in mRNA coding for fibronectin. Elastin mRNA increased approximately twofold above the control values. Nuclear runoff transcription experiments demonstrated a selective increase in the rates of transcription of genes coding for procollagen alpha 1(I), fibronectin, and elastin; the extent of transcriptional stimulation of procollagen alpha 1(I) and fibronectin genes was significantly greater than that of elastin. Since the amount of actin mRNA, as well as the rate of transcription of actin gene(s), varied only slightly after bleomycin treatment, we conclude that the metabolism of mRNAs coding for extracellular matrix proteins may be preferentially perturbed during pulmonary fibrosis.

Complete primary structure of the human alpha 2 type V procollagen COOH-terminal propeptide

Recently we presented the partial covalent structure of a type V collagen chain. Analysis of amino acids 796-1020 in the human alpha 2(V) Gly-X-Y region showed strong conservation of charged positions with the interstitial collagens but also revealed substitutions unique to type V. To gain more information about this procollagen and primarily to resolve the ambiguous nature of the 3' noncollagenous propeptide, we sequenced several cDNA clones coding for amino acids adjacent to the carboxyl end of the alpha chain. Here we report the complete primary structure of the alpha 2(V) COOH-terminal propeptide. In general, the latter sequence (270 residues) bears a greater degree of similarity to those of the interstitial rather than the basement membrane procollagens. Compared to the interstitial procollagens, however, more divergence has occurred in alpha 2(V) surrounding the conserved N-asparaginyl-linked carbohydrate attachment site at residues 171-173, and alpha 2(V) possesses an additional potential glycosylation site (Asn-Lys-Thr) located in a hypervariable region near the NH2 terminus. Although certainly premature to form any rigid hypothesis, a pattern emerges that may be characteristic of alpha 2 versus alpha 1 chains. Both the alpha 2(I) and alpha 2(V) telopeptides are devoid of a lysine, which in alpha 1 chains forms an interchain cross-link with residue 87 of the collagenous region. Also in contrast to the interstitial alpha 1 carboxyl propeptides is the absence in alpha 2(I) and alpha 2(V) of a cysteine that probably participates in an interchain disulfide bond. Therefore, one can speculate that those alpha 2 chains, represented only once in procollagen trimers, may not be under the same selective pressure as alpha 1 chains to maintain certain residues responsible for stabilizing the triple helical molecules.

Partial covalent structure of the human alpha 2 type V collagen chain

Human cDNA libraries were screened with a cDNA fragment presumably encoding the 3' terminus of a procollagen carboxyl propeptide not identifiable as types I, II, III, or IV by protein sequence or Northern blot hybridization. One clone contained a 1350-base pair insert coding in part for 55 uninterrupted Gly-X-Y triplets. Comparison with the amino acid composition of the COOH-terminal cyanogen bromide (CB) peptides of the alpha 1 and alpha 2 type V collagen chains showed similarity only to the alpha 2(V)CB fragment. To identify the NH2 terminus of the peptide designated by methionine, an additional isolate was sequenced and found to contain a Gly-Met-Pro triplet. Thirty-one amino acids from the NH2 terminus of the alpha 2(V)CB9 fragment were then determined by Edman degradation and found to be identical to those derived from the cDNA clone. The DNA sequence encoding part of the triple helical region establishes for the first time the partial structure of a type V collagen chain. Although comparison of residues 796-1020 of the alpha 2(V) collagenous region with alpha 1 (III), alpha 1(I), and alpha 2(I) shows strong conservation of charged positions, the latter three chains appear considerably more similar to each other than to alpha 2(V). A striking feature of the alpha 2(V) sequence between 918-944 is the absence of proline residues. In the analogous region of alpha 1(I) where this amino acid is also lacking, a flexible site in the rigid triple helical structure of type I collagen has been observed (Hofmann, H., Voss, T., Kuhn, K. and Engel, J. (1984) J. Mol. Biol. 172, 325-343).

Human alpha 1(III) and alpha 2(V) procollagen genes are located on the long arm of chromosome 2

The multigene procollagen family encodes probably greater than 20 genetically distinct but structurally related polypeptide chains. Recent characterization of human procollagen clones has allowed determination of functional domains within the proteins, genomic organization, and chromosomal location. Previously, we assigned the coordinately expressed type I genes (alpha 1 and alpha 2) to chromosomes 17 and 7, respectively, and now other investigators have mapped the type II gene to chromosome 12 [Strom, C. M., Eddy, R. L. & Shows, T. B. (1984) Somatic Cell Genet. 10, 651-655]. Recently, we isolated cDNA clones encoding the fourth interstitial procollagen, type III, and the alpha 2 chain of the type V cytoskeletal components. To determine whether these genes were clustered with alpha 1(I), alpha 2(I), or alpha 1(II) or were further dispersed in the genome, in situ hybridization of the alpha 1(III) and alpha 2(V) probes to metaphase chromosomes was carried out. Here we report a fourth autosome with procollagen gene loci but the first cytological evidence for linkage. By using normal and translocated cell lines, our results show that both the alpha 1(III) and alpha 2(V) procollagen genes map to the q24.3----q31 region of chromosome 2.

Hormonal and drug effects on the degradation of human myelin basic protein peptide 43-88 by alkaline proteolytic activity in the rat kidney

The microsomal brush-border fraction of rat renal tissue contains enzymatic activity, optimally active at pH 9, that is capable of degrading human myelin basic protein (BP) peptide 43-88. In the present study, this degradation and the effect on it of selected drugs and hormones were examined further. Of the substances tested, 10(-2) M chloroquine and 10(-5) M ACTH 1-24 were found to be the most effective inhibitors followed by 10(-5) M ACTH 1-39; parathormone, glucagon and insulin were found to be inhibitors an order of magnitude weaker than ACTH 1-24. Hydrocortisone, dexamethasone, maleic acid and ACTH 4-10 were found to have minimal or no inhibitory effect on the peptide degrading activity. Gel filtration of the degradation products indicated that the rate of degradation of BP peptide 43-88 at pH 9 had been retarded by ACTH 1-24. These studies indicate that the clearance and catabolism of this peptide may be altered by available therapeutic agents.

Biochemical and immunological characterization of the secreted forms of human neutrophil gelatinase

Human neutrophils contain a neutral metalloproteinase which degrades denatured collagens and potentiates the action of interstitial collagenase. This gelatinase is rapidly secreted from neutrophils stimulated with phorbol myristate acetate. The secreted enzyme has been purified by a combination of chromatography on DEAE-cellulose and gelatin-Sepharose. The purified enzyme was latent and had a specific activity of 24,000 units. Estimated molecular weight obtained by gel filtration was 150,000-180,000. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme showed three bands with relative molecular weights of 225,000, 130,000, and 92,000. Electrophoresis in the presence of a reducing agent revealed a single band of Mr = 92,000. All the proteins seen on the unreduced gel were found to contain proteolytic activity against gelatin and native type V collagen. Polyclonal antibodies were prepared against the Mr = 130,000 and 92,000 proteins. When analyzed by immunoblotting, both antibodies recognized all three proteins. Furthermore, the identical three proteins were identified by the antibodies when crude culture medium was immunoblotted. The purified enzyme was inhibited by EDTA and 1,10-phenanthroline but not by serine or thiol proteinase inhibitors, suggesting that the enzyme is a metalloendoproteinase. The enzyme had little or no activity against common protein substrates such as bovine serum albumin or casein. Native type I collagen was not cleaved under conditions where native type V collagen was extensively degraded.

Purification of a type V collagen degrading metalloproteinase from rabbit alveolar macrophages

A proteinase capable of degrading the helical region of native human type V collagen was identified in serum-free culture medium from "in vivo-activated" rabbit alveolar macrophages. This enzyme was purified to homogeneity using a combination of gel-filtration, ion-exchange and affinity chromatography. Analysis of the purified material by gel electrophoresis revealed a single broad band with relative molecular mass of 82,000 daltons Enzyme activity was eluted from the gel in a region corresponding to the stained band. The protein band was also found to stain positively using the periodic acid-Schiff technique indicating that it was glycosylated. Amino acid analysis revealed a composition rich in acidic residues. The enzyme cleaved type V collagen into three large molecular weight doublets consistent with two cleavage sites within the helix but was inactive against native type I collagen. However, when type I or type V collagen was heat-denatured, the enzyme degraded the alpha chains to small molecular weight peptides.

Transcriptional regulation of type I collagen genes in cultured fibroblasts by a factor isolated from thioacetamide-induced fibrotic rat liver

Recently Hatahara and Seyer (Hatahara, T., and Seyer, J.M. Biochim. Biophys. Acta (1982) 716, 377-382) isolated a factor from fibrotic rat liver which stimulates collagen synthesis in cultured fibroblasts without affecting their rate of proliferation. To investigate the mechanism of fibrogenic factor-mediated enhancement of type I collagen synthesis, we quantitated the levels of mRNAs coding for pro-alpha 1(I) and pro-alpha 2(I) chains in rat dermal fibroblasts. Cell-free translation experiments revealed that the fibrogenic factor caused greater than 5-fold increase in the translatable levels of type I mRNAs. We also quantitated collagen mRNAs by techniques of Northern blotting of glyoxylated poly(A+) RNA followed by hybridization to nick-translated human cDNA clones containing the coding sequence of pro-alpha 1(I) and pro-alpha 2(I) chains. Furthermore, we investigated the relative rates of collagen mRNA transcription in the isolated nuclei of treated and control fibroblasts. Similar quantitation of beta-actin mRNA transcription, which remains unaffected by the treatment with fibrogenic factor, was used as an internal control. We demonstrate that the fibrogenic factor causes a 4-6-fold increase in the rate of transcription of pro-alpha 1(I) and pro-alpha 2(I) genes. Finally, we also show that the rate of intracellular degradation of collagen is not significantly altered in cells treated with fibrogenic factor. These results combined with data on cell-free translation strongly suggest that the increased accumulation of type I collagen mRNA in fibrogenic factor-treated fibroblasts is a consequence of enhanced rates of collagen mRNA transcription.

Degradation of bovine P2 protein by bovine brain cathepsin D

Bovine brain cathepsin D cleaved bovine P2 protein to produce three major and several minor peptides. The major P2 peptides formed were shown by amino acid analysis and partial sequencing to be peptides 17-54, 20-58 and 65-131 with the latter predominating. In preliminary experiments, P2 peptide 65-131 did not induce experimental allergic neuritis in Lewis rats in equimolar amounts to the neuritogenic P2.

Lymphocyte modulation of fibroblast function in vitro: stimulation and inhibition of collagen production by different effector molecules

Increased collagen deposition is a common feature of granulomatous and nongranulomatous inflammation associated with certain types of cell-mediated immune reactions in vivo. In the present study, we found that normal human peripheral blood mononuclear leukocytes cultured in vitro and stimulated by antigens or T cell mitogens release a 100 to 170 K m.w., heat-labile, trypsin-sensitive protein that stimulates dermal fibroblasts to produce increased quantities of type I and III collagens. Our data suggest that this collagen production protein is of T lymphocyte origin and that it preferentially stimulates production of collagen. We also observed that human mononuclear leukocytes release a different effector molecule with an m.w. of 55 K that inhibits fibroblast collagen production. Mononuclear leukocytes in culture are capable of releasing both the stimulator and the inhibitor of collagen production. The relative amounts of each of these factors elaborated by mononuclear leukocytes in culture appear to be influenced by several variables, such as cell density, type of stimulant used, and the duration of the culture period. These observations suggest that collagen production by fibroblasts in close proximity to sites in vivo where cell-mediated immune reactions are occurring might be regulated by both of these effector molecules.

Lymphocyte modulation of fibroblast function in vitro: stimulation and inhibition of collagen production by different effector molecules

Increased collagen deposition is a common feature of granulomatous and nongranulomatous inflammation associated with certain types of cell-mediated immune reactions in vivo. In the present study, we found that normal human peripheral blood mononuclear leukocytes cultured in vitro and stimulated by antigens or T cell mitogens release a 100 to 170 K m.w., heat-labile, trypsin-sensitive protein that stimulates dermal fibroblasts to produce increased quantities of type I and III collagens. Our data suggest that this collagen production protein is of T lymphocyte origin and that it preferentially stimulates production of collagen. We also observed that human mononuclear leukocytes release a different effector molecule with an m.w. of 55 K that inhibits fibroblast collagen production. Mononuclear leukocytes in culture are capable of releasing both the stimulator and the inhibitor of collagen production. The relative amounts of each of these factors elaborated by mononuclear leukocytes in culture appear to be influenced by several variables, such as cell density, type of stimulant used, and the duration of the culture period. These observations suggest that collagen production by fibroblasts in close proximity to sites in vivo where cell-mediated immune reactions are occurring might be regulated by both of these effector molecules.

Epitope-specific protective immunogenicity of chemically synthesized 13-, 18-, and 23-residue peptide fragments of streptococcal M protein

The ability of chemically synthesized subpeptides of type 24 streptococcal M protein to evoke protective antibodies in rabbits was investigated. We synthesized copies of the COOH-terminal 13, 18, and 23 amino acid residues of cyanogen bromide fragment 7 (CB7) of pepsin-extracted type 24 M protein, except that methionine was substituted for homoserine as the COOH-terminal residue. An additional residue of cysteine was added at the COOH terminus of the 13-residue peptide. Each of the peptides, designated S-CB7-(23-35)-Cys, S-CB7-(18-35), and S-CB7-(13-35), when conjugated to lysylated tetanus toxoid with glutaraldehyde, was capable of stimulating formation of protective anti-type 24 M protein antibodies in rabbits. The smallest peptide, S-CB7-(23-35)-Cys, elicited immune responses equally as strong, if not stronger, than those to the longer peptides. A single Lys/Gly substitution in this 13-residue peptide resulted in its failure to stimulate protective antibodies. None of the antisera reacted with heterologous serotypes of M protein and none reacted with frozen sections of human heart tissue. These results indicate that a chemically synthesized peptide fragment corresponding to as few as 13 amino acid residues of streptococcal M protein is capable of evoking protective anti-streptococcal antibodies without evoking antibodies crossreactive with cardiac tissue.

Repeating covalent structure and protective immunogenicity of native and synthetic polypeptide fragments of type 24 streptococcal M protein. Mapping of protective and nonprotective epitopes with monoclonal antibodies

The complete amino acid sequences of three cyanogen bromide peptide fragments (CB3, CB4, and CB50 of type 24 M protein extracted from Streptococcus pyogenes by limited pepsin digestion were determined by automated Edman degradation of the uncleaved peptides and their tryptic peptides. CB3 and CB4 each contain 35 amino acid residues, whereas CB5 contains 37. The sequence of CB3 was found to be: (formula: see text) (where Hse represents homoserine). The sequence of CB4 was identical except for amino acid substitutions of arginine and glutamine at positions 23 and 24, respectively. The sequence of CB5 also was identical with that of CB3 except for substitutions of aspartic acids at positions 28 and 29; leucine, glutamic acid, and glycine at positions 33, 34, and 35, respectively; and an additional two amino acids, alanine and homoserine, at positions 36 and 37, respectively. A comparison of the structures of these three peptide fragments with those previously reported for CB6 and CB7 revealed as few as one to six amino acid substitutions among the five repeating peptides; CB4 and CB6 differed only by a single Asp/Glu substitution at position 26. When covalently linked to polylysine and injected as an emulsion in complete Freund's adjuvant, CB3, CB4, and CB5 each evoked high titers of type-specific opsonic and bactericidal antibodies in rabbits. A chemically synthesized peptide identical with native CB3 except that it contained methionine instead of homoserine at its COOH terminus was similarly immunogenic. None of the conjugated native or synthetic peptides raised antibodies at reacted in immunofluorescence tests with sarcolemmal membranes of human heart tissue. Mapping studies with monoclonal antibodies revealed a number of distinct protective and nonprotective epitopes. The single Asp/Glu substitution between CB4 and CB4 rendered the 35-residue peptide unrecognizable by protective monoclonal antibodies but recognizable by a nonprotective one. Our studies demonstrate that the repeating covalent structures of native and chemically synthesized polypeptide fragments of streptococcal M protein possess several unique as well as repeating epitopes that evoke opsonic and presumably protective, but not heart cross-reactive, antibodies against a rheumatogenic strain of S. pyogenes.

Type-specific immunogenicity of a chemically synthesized peptide fragment of type 5 streptococcal M protein

We determined the antigenic specificity and protective immunogenicity of two chemically synthesized peptides of type 5 streptococcal M protein. The synthetic peptides, designated S-M5(1-20) and S-M5(20-40), represent the amino-terminal amino acid sequence of the native pepsin-extracted M5 molecule, which is known to contain at least one heart cross-reactive epitope. Initial studies showed that neither of the synthetic peptides was able to bind purified heart-reactive M5 antibodies. In addition, S-M5(1-20), but not S-M5(20-40), contained type-specific antigenic determinants as measured by enzyme-linked immunosorbent inhibition assays. When covalently linked to tetanus toxoid, S-M5(1-20), but not S-M5(20-40), evoked significant levels of type-specific, opsonic (and presumably protective) antibodies in rabbits without evoking heart cross-reactive antibodies.