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N Strick

Publications and source records attributed to N Strick.

At least 37 records · Page 2Linked to original sources
PubMed1992

Synthetic peptides and anti-peptide antibodies as probes to study interdomain interactions involved in virus assembly: the envelope of the human immunodeficiency virus (HIV-1).

Synthetic peptides and anti-peptide antibodies have been widely used as probes to map B- and T-cell epitopes on proteins. Such probes also have the potential to delineate contact sites involved generally in protein-protein interactions or in association of domains within a protein. We applied peptide/anti-peptide probes to define: (1) regions on the human immunodeficiency virus type 1 (HIV-1) envelope glycoproteins gp120 and gp41 involved in the association between these two glycoproteins; and (2) sites on gp120/gp41, essential for the association of HIV-1 with the CD4 cell receptor. Results of this examination suggested the following: (1) two segments on gp120, encompassing residues (102-126) and (425-452), contribute to the binding site for CD4 and are expected to be juxtaposed in the folded gp120 chain; (2) portions of immunodominant gp120 and gp41 epitopes, encompassing residues (303-338) and (579-611), respectively, appeared to be involved in the gp120-gp41 association, as suggested by direct binding studies and by the limited accessibility of these epitopes on HIV-1 virions: other portions of gp120 also appeared to contribute to the association between these two glycoproteins; (3) there is a partial overlap between gp41 and CD4 binding sites on gp120; (4) the fusion domain and a segment (637-666) of gp41 are not accessible to antibodies after oligomerization of gp41; and 5) the gp120-gp41 association was blocked by aurintricarboxylic acid, suggesting the possibility of developing antiviral compounds interfering with HIV-1 assembly.

Amino Acid Sequence↗
PubMed1991

Confronting the hypervariability of an immunodominant epitope eliciting virus neutralizing antibodies from the envelope glycoprotein of the human immunodeficiency virus type 1 (HIV-1)--II. Synthetic peptides linked to HIV-1 carrier proteins gag and nef.

Combining of subtype specific peptides from the hypervariable loop of the envelope glycoprotein gp120 of divergent HIV-1 isolates may help in designing a broadly protective immunogen against HIV-1 infection. To enhance the immunogenicity of such a polyvalent antigen, in the absence of oil-containing adjuvants, it is necessary to link the peptides to a protein carrier. It is preferable to use as carriers those proteins from HIV-1 itself which may contribute to eliciting protective immunity. The structural and non-structural proteins, gag P18 and nef, respectively, which can be prepared in high yields by recombinant DNA techniques in Escherichia coli, were selected for this purpose. The corresponding peptide-protein conjugates, each containing 21 distinct peptides, were prepared using the cross-linking reagents N-succinimidyl-3-(2-pyridyldithio)-propionate (SPDP) or m-maleimidobenzoyl-N-hydroxysulfosuccinimide ester (sulfo-MBS). Conjugates prepared by the second method elicited approximately 10-100 times higher levels of antibodies recognizing the homologous peptides and the HIV-1 envelope glycoproteins. The sulfo-MBS conjugation procedure preserved the antigenicity of both gag P18 and nef and the respective conjugates elicited an immune response to these proteins. Despite the low immunization dose of single peptides (10 micrograms) present in the mixture of peptides collectively linked to the carriers, antibody responses to most of the individual peptides were high (dilution endpoints 1: greater than 16,000, 1: greater than 80,000 for the nef and gag P18 conjugates, respectively). Conjugates consisting of a multitude of HIV-1 envelope-derived peptides in combination with gag P18 and nef carriers are expected to elicit broadly protective immunity against distinct HIV-1 subtypes.

Animals↗
PubMed1991

Peptides mimicking selected disulfide loops in HIV-1 gp120, other than V3, do not elicit virus-neutralizing antibodies.

The positions of all 9 intrachain disulfide bonds within the envelope glycoprotein gp120 of the human immunodeficiency virus (HIV-1) have been established recently. Peptides expected to mimic some of the disulfide-bonded domains [(120-133)-(203-221); (133-138)-(164-203); (224-254); (391-425) and (385-392)-(425-452)] were synthesized. All peptides, except (120-133)-(203-221), elicited in immunized rabbits relatively high levels of antibodies reacting with gp120 in enzyme-linked immunosorbent assay (ELISA) and/or Western immunoblot assays. However, these antibodies failed to neutralize the infectivity of HIV-1. Combined with earlier reports concerning other gp120 loop peptides, these results confirm the uniqueness of the V3 (303-338) loop in encompassing a principal determinant(s) involved in virus neutralization.

Amino Acid Sequence↗
PubMed1991

Antibody responses of chimpanzees immunized with synthetic peptides corresponding to full-length V3 hypervariable loops of HIV-1 envelope glycoproteins.

Immunization of primates or humans with human immunodeficiency virus type 1 (HIV-1) glycoproteins usually elicited moderate immune responses to the principal neutralizing determinant (PND) located within the V3 hypervariable loop of gp120. Since an antibody response to the PND appears to be protective, experiments were carried out to determine the responsiveness of chimpanzees to immunization with synthetic peptides corresponding to the full-length V3 loop. Seven chimpanzees (4 preimmunized with gp160, 2 preimmunized with HIV-1 antigens unrelated to gp160, and 1 unimmunized) were vaccinated with a mixture of full-length V3 loop peptides from 21 distinct HIV-1 isolates (clones) either in unconjugated form or linked to carrier proteins from HIV-1 nef and gag P18, respectively. Six chimpanzees developed high levels of antibodies to the peptides (dilution endpoints 1: greater than 25,000), and 5 had high levels of antibodies to gp120 from HIV-1IIIB (endpoint titers 1: greater than 500,000). Chimpanzees immunized with peptide-carrier conjugates (4) had antibodies to the carrier proteins nef and gag P18, respectively (endpoint titers 1: greater than or equal to 35,000). Virus-neutralizing (VN) antibodies were detected in sera of 5 of 7 chimpanzees, but were present at titers of 1: greater than or equal to 400 only in sera of 2 chimpanzees. One of these was challenged with HIV-1 and was protected against infection, as reported elsewhere. The antibodies were primarily specific for the HIV-1 isolate used for primary immunization before boosting with peptides. The relatively low dilution endpoints of VN antibodies as compared with endpoints determined by site-specific immunoassays probably can be ascribed to imperfect mimicry of conformational epitopes by synthetic peptides. Nevertheless, sequential or simultaneous immunization with recombinant envelope glycoproteins of HIV-1 and selected synthetic peptides offers an approach for eliciting protective immunity against HIV-1.

Amino Acid Sequence↗
PubMed1990

Detection of receptors for hepatitis B virus on cells of extrahepatic origin.

Receptors for hepatitis B virus (HBV; subtype adw) were identified on the surface of human hepatoma HepG2 cells in earlier studies. The cell receptor binding site on HBV was assigned to the preS(21-47) region of the preS1 sequence of the envelope protein. Studies presented here show that (1) amino acid residue replacements within the preS(21-47) sequence distinguishing HBV subtypes adw and ayw, preserve the binding capacity of the HBV env protein for HepG2 cell receptors; (2) the inhibition of binding between HepG2 cells and preS1-specific ligands by antibodies is effective only if the subtype specificity of anti-preS1-specific antibodies and of the preS1-specific ligands are matched; (3) receptors for HBV were present on the surface of human cells of nonhepatic origin, including peripheral blood B-lymphocytes, some hematopoietic cell lines of the B-cell lineage, neuroblastoma, amnion, and embryonic carcinoma cell lines. Receptors for HBV on these cells appeared similar to the receptor on HepG2 cells by the following criteria: (a) recognition by antibodies raised against the receptor on HepG2 cells; (b) inhibitory activity of lysates prepared from these cells on the interaction between HepG2 cells and preS1-specific ligands; and (c) the inhibitory effect of lysates from HepG2 cells on the reaction of these cells with HBsAg- and preS(21-47)-cellulose. The presence of receptors for HBV on some cells of extrahepatic origin is in accordance with earlier observations indicating that hepadnaviruses are not strictly hepatotropic.

Amino Acid Sequence↗
PubMed1990

Antigenic mimicry of an immunoglobulin A epitope by a hepatitis B virus cell attachment site.

The preS(21-47) sequence of the hepatitis B virus (HBV) envelope protein is involved in binding of the virus to cell receptors. A protein similarity search revealed a partial homology between this sequence and a segment of the human immunoglobulin A (IgA) heavy chain constant region, suggesting that the cell attachment site for HBV might be located on secretory component representing a receptor for polymeric IgA. Data presented herein do not support this hypothesis but provide evidence for immunological cross-reactivity between IgA and the preS(21-47) region of the HBV env protein.

Amino Acid Sequence↗
PubMed1990

Confronting the hypervariability of an immunodominant epitope eliciting virus neutralizing antibodies from the envelope glycoprotein of the human immunodeficiency virus type 1 (HIV-1).

Antibody mediated and cell mediated immune responses to the envelope glycoproteins gp120 and gp41 of the human immunodeficiency virus (HIV-1) are considered important for protection against infection and for attenuation of disease symptoms after infection. Virus neutralizing antibodies are mostly subtype specific and primarily directed against epitopes on a hypervariable loop from the V3 region of HIV-1 gp120. Such epitopes are recognized by helper and cytotoxic T-cells suggesting that all protective immune responses to HIV-1 are predominantly subtype specific. The extraordinary primary sequence variability of gp120 indicates that a combination of subtype specific components will be required to design a broadly effective protective immunogen against HIV-1. Peptides from hypervariable loops of the V3 region of 21 distinct HIV-1 isolates (clones) were synthesized and used to raise rabbit antisera. The antisera contained high levels of antibodies recognizing the homologous peptides and the parent gp120 sequence. The serological cross-reactivity between the distinct peptides was evaluated and related to amino acid divergence. The corresponding relationship approximated a linear regression with a correlation coefficient r = 0.718. The 21 peptides were combined into a single immunogen which elicited broadly reactive antibodies recognizing all 21 peptides as well as gp120 from the only isolate tested, HIV-1 IIIB. The results suggest the possibility of developing broadly protective HIV-1 immunogens by combining judiciously selected subtype specific peptides derived from envelope glycoproteins of divergent virus isolates.

Amino Acid Sequence↗
PubMed1990

Search for epitope-specific antibody responses to the human immunodeficiency virus (HIV-1) envelope glycoproteins signifying resistance to disease development.

It is essential for the development of strategies for prevention and therapy of human immunodeficiency virus (HIV-1) infections to define host factors playing a dominant role in determining the clinical outcome of infection. Antibodies directed against restricted regions of the HIV-1 glycoproteins gp120 and gp41 are likely to represent important factors involved in host defense against HIV-1. Definition of qualitative and quantitative differences in the spectrum of anti-gp120 and anti-gp41 antibodies between two vastly different groups of HIV-1-infected individuals, long-term asymptomatic carriers, and individuals with acquired immunodeficiency syndrome (AIDS) who died, might reveal the epitope specificity of antibodies contributing to prevention of clinical disease. To accomplish this goal, sera from both groups were assayed for antibodies recognizing synthetic peptides from gp120/gp41 which were shown in earlier experiments to mimic epitopes on the two HIV-1 glycoproteins. None of the sera recognized all of the distinct 27 peptides from gp120 and gp41. The spectrum of antibodies was distinct for each of the sera from both groups of HIV-1-infected individuals. Nevertheless, antibody responses distinguishing the two groups from each other were discerned. In particular, it was possible to predict the unfavorable outcome of disease by comparative measurements of levels of antibodies to a peptide (303-338), corresponding to the entire V3 hypervariable loop of gp120 and/or by providing evidence for declining levels of these antibodies during the course of infection. Antibodies recognizing additional peptides [(219-245), (280-306), (425-452), (658-682), (729-758), (808-845), and (845-862)] were significantly less prevalent in AIDS patients than in asymptomatic carriers. It appears possible that maintenance of high levels of the respective antibodies would contribute to preventing AIDS in HIV-1-infected individuals. Active immunization with antigens containing epitopes defined by the respective peptides and/or administration of the corresponding antibodies may be considered as a modality for therapy of HIV-1 infections.

Epitopes↗
PubMed1990

B cell epitope mapping of human immunodeficiency virus envelope glycoproteins with long (19- to 36-residue) synthetic peptides.

Envelope glycoproteins, gp 120 and gp41, of the human immunodeficiency virus type 1 (HIV-1) elicit immune responses, including virus-neutralizing antibodies, which are expected to play a role in the defence against HIV-1 infection. Subregions of the gp120/gp41 sequence have immunosuppressive effects or may be implicated in autoimmune responses. Some of the immunodominant epitopes of gp120/gp41 do not contribute to protective immunity and act as immunological decoys. These circumstances emphasize the need to select from gp120/gp41 regions inducing protective responses. Towards this goal, 30 peptides covering approximately 87% of the HIV-1 strain BH10 gp120/gp41 sequence were synthesized. Antibodies in rabbit and human anti-HIV-1 sera recognized 28 and nine of the peptides, respectively, indicating that most of the gp120/gp41 sequence is immunogenic and secondly, that the antibody response to HIV-1 is restricted in infected humans. Most of the peptides, without conjugation to carriers, elicited high levels of anti-peptide (endpoints 1: greater than 10(4] and anti-gp120/gp41 (endpoints 1: greater than or equal to 10(3] antibodies. The highest levels of virus-neutralizing antibodies were elicited by peptide 306 to 338 from a hypervariable loop of gp120. Additional peptides from the full-length hypervariable loop (303 to 338) of HIV-1 BH10 and from 20 additional HIV-1 isolates were recognized differentially by human anti-HIV, suggesting that success of passive immunization may depend on a match between administered antibodies and the challenging HIV-1 strain, and also that active immunization with selected peptides from a hypervariable region of distinct HIV-1 isolates should be explored further as a method for prophylaxis against infection.

Antibody Specificity↗
PubMed1989

Hepatitis B virus surface antigen (HBsAg) as carrier for synthetic peptides having an attached hydrophobic tail.

B- and T-cell epitopes from three distinct regions of the hepatitis B virus (HBV) envelope (env) protein (preS1, preS2 and S) are involved in eliciting protective immunity. Since preS1 sequences inhibit the secretion of HBV env proteins from eukaryotic cells, it is difficult to prepare immunogens rich in preS1 sequences. This problem can be overcome by linking synthetic peptides from the preS1 region to particles containing both S and preS2 sequences. We describe here a novel approach for binding of synthetic peptides to exposed hydrophobic domains on HBV env proteins. Long chain fatty acids or mercaptans are covalently linked to synthetic peptides. Peptides with the attached hydrophobic tails interact strongly with HBV env proteins (S + preS2), whereby hybrid immunogens are generated. Such immunogens can be used in combination with alum, the only adjuvant approved for human use. The combination of the preS1 peptide [preS(12-47)] with particles containing the S and preS2 regions resulted in an immunogen which: (1) elicits a broad spectrum of protective antibodies; (2) circumvents the nonresponsiveness to: (a) preS1 epitopes in preS1-nonresponder strains of mice; and (b) S-protein in S-protein-nonresponder strains of mice; and (3) augments the immune response to S-protein. The combination of HBV env proteins with a synthetic peptide from the envelope of the human immunodeficiency virus (HIV-1) resulted in an immunogen eliciting anti-HIV-1. Hybrid immunogens consisting of viral proteins and of synthetic peptides represent a feasible approach for the design of future vaccines.

Animals↗
PubMed1989

Antibodies to synthetic peptides from the preS1 region of the hepatitis B virus (HBV) envelope (env) protein are virus-neutralizing and protective.

Hepatitis B virus (HBV) envelope (env) proteins contain three antigenic domains designated S, preS2 and preS1. Studies with synthetic peptide immunogens demonstrated the role of preS2 epitopes in protection against HBV infection. The preS1 domain is implicated in virus-cell receptor interactions suggesting that anti-preS1-specific antibodies should neutralize the infectivity of HBV by blocking virus attachment to cells. We present here evidence that an antiserum to a peptide from the preS1 sequence, anti-preS(21-47), is virus-neutralizing and that active immunization of chimpanzees with a longer peptide derived from the preS1 sequence, preS(12-47), elicits antibodies protective against HBV infection. These results establish the role of the preS1 domain in the process of virus neutralization and the potential of synthetic preS1 analogues for hepatitis B vaccination.

Animals↗
PubMed1988

Antibodies recognizing human serum albumin are not elicited by immunization with preS2 sequences of the hepatitis B virus envelope protein.

Antibodies to the preS2 region of the hepatitis B virus (HBV) envelope protein and to human serum albumin (HSA) were allegedly detected at about the same level in sera of humans with acute or chronic hepatitis B [Hellström et al., 1986]. It was claimed that anti-HSA arises as a result of an immune response to the preS2 sequence and that it was involved in hepatocellular damage. Over 100 sera from animals and humans immunized with HBsAg containing preS2 sequences, or with synthetic peptides from the preS1, preS2, and S regions of the HBV env protein were assayed for anti-HSA. The results revealed the following: 1) Immunization with the native preS2 sequence or with unconjugated synthetic peptides derived from that sequence does not result in elicitation of anti-HSA. Therefore the alleged appearance of anti-HSA during hepatitis B cannot be directly related to an anti-preS2-specific immune response. 2) Some synthetic peptides, whether or not they were derived from the preS2 sequence, when linked to certain carriers, but not to others, elicited in rabbits an anti-HSA response, which was markedly lower than the response to the homologous peptide. These anti-HSA antibodies could be separated from anti-preS2-specific antibodies by affinity chromatography and did not recognize the synthetic peptide used for immunization. The use in active immunoprophylaxis of hepatitis B of unconjugated peptides from the preS2 sequence with proven high immunogenicity will avoid carrier/linker-mediated induction of antibodies not relevant to protection against HBV.

Animals↗
PubMed1987

Antibodies to synthetic peptides from the pre-S1 and pre-S2 regions of one subtype of the hepatitis B virus (HBV) envelope protein recognize all HBV subtypes.

Immunodominant B and T cell epitopes have been demonstrated recently on the preS1 and PreS2 regions of the hepatitis B virus (HBV) envelope protein. Synthetic peptide analogs corresponding to the preS2 region elicit virus-neutralizing antibodies and protect chimpanzees against HBV infection. Antibodies raised by immunization with peptides derived from the preS1 sequence block the site involved in HBV attachment to cell receptors, and are expected to be virus-neutralizing. Results presented here show that antisera raised against synthetic peptide analogs carrying the immunodominant epitope of the preS1 and preS2 sequence, respectively, and corresponding to two HBV subtypes, adw2 and ayw, each recognized preS1 and preS2 specific epitopes on all serological subtypes of the HBV envelope protein. Thus, the sequence variability within the preS1 and preS2 regions does not represent an impediment to the development of synthetic peptide or genetically engineered hepatitis B preS immunogens for worldwide immunization.

Amino Acid Sequence↗
PubMed1987

Immunological cross-reactivity between preS2 sequences of the hepatitis B virus envelope proteins corresponding to serological subtypes adw2 and ayw.

An immune response to epitopes localized on the preS region of the hepatitis B virus (HBV) envelope (env) is elicited during recovery from HBV infection and appears to play a role in virus clearance. Anti-preS antibodies (Ab) are expected to be protective against HBV infection as indicated by the virus-neutralizing capacity of Ab to a preS2-specific synthetic peptide preS(120-145). However, there is considerable amino acid variability between preS regions corresponding to distinct serological subtypes of HBV, raising the question whether the preS sequences are sufficiently related immunologically to have the potential of inducing cross-protective immunity. To answer this question concerning the preS2 region, antisera to synthetic peptides preS(120-153) and preS(128-153) corresponding to subtypes adw2 and ayw, as well as to the native env [ayw] protein were raised. Using the resulting polyclonal Ab, an immunological relatedness between preS2 sequences of subtypes adw2 and ayw was demonstrated. On the other hand, Ab selected by affinity chromatography or by cloning hybridoma cells may recognize with strong preference subtype-specific determinants within the preS2 region when the compared antigens are in solution rather than on the solid phase. These findings have implication for the design of: (1) preS2-specific immunogens and (2) immunoassays for quantitation of preS2 sequences in HBV env proteins.

Amino Acid Sequence↗
PubMed1986

Identification and chemical synthesis of a host cell receptor binding site on hepatitis B virus.

Hepatitis B virus (HBV) has not yet been propagated in vitro, and knowledge concerning its reaction with receptors on target cells remained scant. We have located within the HBV envelope proteins a sequence mediating the attachment of HBV to human hepatoma HepG2 cells. A synthetic peptide analog (PLGFFPDHQLDPAFGANSNNPDWDFNP) is recognized by both cell receptors and anti-HBV antibodies and elicits antibodies reacting with native HBV. The synthetic peptide is a promising immunogen expected to elicit protective antibodies based on the concept of the attachment blockade pathway of virus neutralization. The approach described here, based on anti-peptide antisera and the binding of peptide analogs to cell receptors is generally applicable for the delineation of cell receptor binding sites on viruses with known gene sequences.

Amino Acid Sequence↗
PubMed1986

Characterization of monoclonal antibodies specific for the pre-S2 region of the hepatitis B virus envelope protein.

Monoclonal antibodies (McAb) specific for the pre-S region of the hepatitis B virus (HBV) envelope protein were prepared using HBV particles of hepatitis B surface antigens (HBsAg) as immunogens. The antibodies reacted in Western blot analyses and in ELISA with pre-S2 sequences of the HBV envelope protein. Pepsin or protease V8 treatment of the antigen abolished reactivity. The fine specificity of one of the McAb (F376) was established by immunoassays using synthetic peptides and a pre-S2-beta-galactosidase fusion protein expressed in E. coli. The shortest peptide recognized by F376 is demarcated by residues pre-S(132) at the N-terminal and pre-S(140)-pre-S(145) at the C-terminal. The corresponding amino acid sequence (for HBV subtype adw2) is: QDPRVRGLY(LPAGG). Additional amino acid residues at the N-terminal, and possibly at the C-terminal ends contribute to the binding of McAb, probably due to conformational influences. The McAb was applied to immunoassays of pre-S2 sequences in purified HBsAg and in human sera containing HBsAg.

Antibodies, Monoclonal↗
PubMed1986

Antibodies to a synthetic peptide from the preS 120-145 region of the hepatitis B virus envelope are virus neutralizing.

Studies with synthetic peptides have provided evidence for the presence of preS coded sequences in the envelope (env) proteins of hepatitis B virus (HBV) and indicated that these sequences are involved in the specific attachment of HBV to liver cells. Scanning of the preS sequence for immunodominant continuous epitopes identifies the sequence within residues preS (120-145) as the most immunogenic in eliciting antibodies recognizing HBV and as the most efficiently binding antibodies from sera of rabbits and humans immunized with HBV env proteins. To assess the potential of preS (120-145) as a synthetic vaccine against hepatitis B, in vitro neutralization of the virus by rabbit antiserum to the peptide was assayed in chimpanzees. The animals, subsequently proven to be susceptible to HBV infection, did not develop hepatitis B as judged by negative serological tests for HBV-associated antigens and antibodies and by normal serum alanine aminotransferase levels and normal liver biopsies. These results establish the role of preS domains in the process of virus neutralization and the potential of synthetic preS analogues for hepatitis B vaccination.

Animals↗