Baculovirus-derived human immunodeficiency virus type 1 virus-like particles activate dendritic cells and induce ex vivo T-cell responses

We have recently developed a candidate human immunodeficiency virus type 1 (HIV-1) vaccine model based on HIV-1 Pr55(gag) virus-like particles (HIV-VLPs), produced in a baculovirus expression system and presenting a gp120 molecule from a Ugandan HIV-1 isolate of clade A (HIV-VLP(A)s). The HIV-VLP(A)s show the induction in BALB/c mice of systemic and mucosal neutralizing antibodies as well as cytotoxic T lymphocytes, by intraperitoneal as well as intranasal administration. In the present article, the effects of the baculovirus-expressed HIV-VLPs on human immature monocyte-derived dendritic cells (MDDCs) have been evaluated. The HIV-VLPs efficiently induce maturation and activation of MDDCs and are incorporated into MDDCs preferentially via an actin-dependent macropinocytosis and endocytosis. The HIV-VLP-activated MDDCs show enhanced Th1- and Th2-specific cytokine production, and the effects of HIV-VLPs on MDDCs are not mediated through Toll-like receptors 2 and 4 (TLR2 and -4) signaling. Finally, HIV-VLP-loaded MDDCs are able to induce a primary and secondary response in autologous human CD4(+) T cells in an ex vivo immunization assay. Our results on the interaction and processing of baculovirus HIV-VLPs by MDDCs give an insight into the mechanisms underlying the immune response induced by HIV-VLP(A)s in vivo.

Progress toward the development of a bacterial vaccine vector that induces high-titer long-lived broadly neutralizing antibodies against HIV-1

Conformationally constrained HIV-1 Env and gp120 immunogens induce broadly cross-reactive neutralizing antibodies. Thus, it is now feasible to rationally design an HIV-1 vaccine that affords protection through humoral mechanisms. This paper reviews our progress toward the development of an oral bacterial vaccine vector that is capable of delivering an HIV-1 DNA vaccine to host lymphoid tissues and inducing broadly neutralizing antibodies to HIV-1 in the mucosal and systemic immune compartments.

Immunogenicity of DNA vaccines that direct the coincident expression of the 120 kDa glycoprotein of human immunodeficiency virus and the catalytic domain of cholera toxin

Passive antibody studies unequivocally demonstrate that sterilizing immunity against lentiviruses is obtainable through humoral mechanisms. In this regard, DNA vaccines represent an inexpensive alternative to subunit vaccine for mass vaccination programs designed to induce such responses to human immunodeficiency virus type I (HIV-1). At present, however, this vaccine modality has proven relatively ineffective at inducing humoral responses. In this report, we describe the immunogenicity of DNA vaccines that direct the coincident expression of the cholera toxin catalytic domain (CTA1) with that of the human immunodeficiency virus type I gp120 through genes either encoded in individual plasmids or in a single dicistronic plasmid. In BALB/cJ mice, coincident expression of CTA1 in either a separate plasmid or in the dicistronic plasmid in the DNA vaccines induced serum IgG responses to gp120 that were at least 1000-fold greater, and remained elevated longer than, the analogous responses in mice vaccinated with a DNA vaccine that expressed gp120 alone. In addition, mice vaccinated with CTA1 and gp120 produced significantly more gp120-specific IFN-gamma ELISPOTs than mice vaccinated with the gp120 DNA vaccine. Combined, these data show that the adjuvant properties of cholera toxin can be harnessed in DNA vaccine modalities.

Choroid plexus carcinoma presenting as an intraparenchymal mass

A 6-year-old girl with a history of a nondisplaced skull fracture diagnosed with computerized tomography (CT) scanning 3 years previously presented with a 6-week history of headaches and decreased use of her right side. On admission CT scans, a large cystic mass was identified in the left frontal lobe region of the brain. A connection between the mass and the ventricular system was not seen on radiological examination or during surgery. Gross-total resection of the mass was achieved. The histological and immunohistochemical findings in the resected tissue confirmed a diagnosis of choroid plexus carcinoma (ChPC). This is the first reported case of a ChPC arising in an extraventricular location not associated with the choroid plexus.

Mucosal and systemic HIV-1 Env-specific CD8(+) T-cells develop after intragastric vaccination with a Salmonella Env DNA vaccine vector

CD8(+) T-cell responses provide beneficial antiviral immunity against human immunodeficiency virus 1 (HIV-1). In this study, we show that intragastric vaccination with a Salmonella HIV-1 Env DNA vaccine vector generates Env-specific CD8(+) T-cells, both in mucosal and systemic lymphoid tissue. By contrast, intramuscular vaccination with the Env DNA vaccine alone only induced systemic CD8(+) T-cells. To our knowledge, this is the first report showing both mucosal and systemic CD8(+) T-cell responses following vaccination with a Salmonella vaccine vector. These data suggest that this mode of HIV-1 DNA vaccine delivery will be advantageous over parenterally administered HIV-1 DNA vaccines.

Antigenic properties of the human immunodeficiency virus envelope during cell-cell fusion

Human immunodeficiency virus (HIV) fusion and entry involves sequential interactions between the viral envelope protein, gp120, cell surface CD4, and a G-protein-coupled coreceptor. Each interaction creates an intermediate gp120 structure predicted to display distinct antigenic features, including key functional domains for viral entry. In this study, we examined the disposition of these features during the fusion of HeLa cells expressing either HIV(HXB2) envelope (Env cells) or CXCR4 and CD4 (target cells). Cell-cell fusion, indicated by cytoplasmic dye transfer, was allowed to progress for various times and then arrested. The cells were then examined for reactivity with antibodies directed against receptor-induced epitopes on gp120. Analyses of cells arrested by cooling to 4( degrees )C revealed that antibodies against the CD4-induced coreceptor-binding domain, i.e., 17b, 48d, and CG10, faintly react with Env cells even in the absence of target cell or soluble CD4 (sCD4) interactions. Such reactivity increased after exposure to sCD4 but remained unchanged during fusion with target cells and was not intensified at the Env-target cell interface. Notably, the antibodies did not react with Env cells when treated with a covalent cross-linker either alone or during fusion with target cells. Immunoreactivity could not be promoted or otherwise altered on either temperature arrested or cross-linked cells by preventing coreceptor interactions or by using a 17b Fab. In comparison, two other gp120-CD4 complex-dependent antibodies against epitopes outside the coreceptor domain, 8F101 and A32, exhibited a different pattern of reactivity. These antibodies reacted with the Env-target cell interface only after 30 min of cocultivation, concurrent with the first visible transfer of cytoplasmic dye from Env to target cells. At later times, the staining surrounded entire syncytia. Such binding was entirely dependent on the formation of gp120-CD4-CXCR4 tricomplexes since staining was absent with SDF-treated or coreceptor-negative target cells. Overall, these studies show that access to the CD4-induced coreceptor-binding domain on gp120 is largely blocked at the fusing cell interface and is unlikely to represent a target for neutralizing antibodies. However, new epitopes are presented on intermediate gp120 structures formed as a result of coreceptor interactions. Such findings have important implications for HIV vaccine approaches based on conformational alterations in envelope structures.

Perforin-low memory CD8+ cells are the predominant T cells in normal humans that synthesize the beta -chemokine macrophage inflammatory protein-1beta

The synthesis of antiviral beta-chemokines has joined cytolysis as a potential mechanism for the control of HIV-1 infection by CD8(+) T cells. Recent evidence suggests that these two effector functions can diverge in some individuals infected with HIV-1; however, little is known about the CD8(+) T cell subsets in normal individuals that synthesize antiviral beta-chemokines. In this report, we have used mutliparameter flow cytometry to characterize the T cell subsets that secrete the antiviral beta-chemokine macrophage inflammatory protein (MIP)-1beta. These studies have shown: (i) CD8(+) cells are the predominant T cell subset that synthesizes MIP-1beta; (ii) MIP-1beta and IFN-gamma are synthesized congruently in most CD8(+) T cells; however, significant numbers of these cells synthesize only one of these effector molecules; (iii) approximately 60% of the CD8(+) T cells that synthesize MIP-1beta lack perforin; (iv) MIP-1beta is synthesized with approximately equal frequency by CD28(+) and CD28(-) subpopulations of CD8(+) T cells; (v) MIP-1beta is synthesized by three distinct CD8(+) T cell subsets defined by the expression of CD45R0 and CD62L; and (vi) MIP-1beta is not synthesized in short-term cultures of naive CD8(+) T cells. These results demonstrate substantial subset heterogeneity of MIP-1beta synthesis among CD8(+) T cells and suggest that these subsets should be evaluated as correlates of protective immunity against HIV-1.

Stimulation of HIV gp120-specific cytolytic T lymphocyte responses in vitro and in vivo using a detoxified pertussis toxin vector

CD8+ cytolytic T lymphocytes (CTL) are almost certainly an important component of a potentially protective immune response to HIV. To test the ability of pertussis toxin (PT) to deliver an HIV-derived major histocompatibility complex (MHC) class I peptide for CTL stimulation, we constructed a fusion of the gp120 P18-I10 CTL epitope with a genetically detoxified derivative of PT (PT9K/129G) and assayed this fusion for its ability to stimulate a gp120-specific CTL response in vitro and in vivo. Antigen-presenting cells incubated with this fusion protein were lysed by P18-I10-specific CTL in vitro and this activity was shown to be MHC class I restricted. The activity was inhibited by brefeldin A but was not inhibited by proteasome inhibitors, possibly because PT undergoes retrograde intracellular transport through the Golgi apparatus to the endoplasmic reticulum and delivers epitopes directly to nascent class I molecules. Mice immunized intraperitoneally with a single dose of the fusion protein without adjuvant raised a strong gp120-specific CTL response in the spleen. This CTL response was dependent on (1) the dose of fusion administered, (2) the fusion of the epitope with the toxin (since coadministration of peptide and toxin gave no response), and (3) the activity of CD8+ cells. These data demonstrate that this detoxified derivative to PT, which is already a component of a licensed vaccine for humans, could represent a useful vaccine vector molecule for stimulation of HIV-specific CTL responses.

Expression and characterization of a single-chain polypeptide analogue of the human immunodeficiency virus type 1 gp120-CD4 receptor complex

The infection of CD4(+) host cells by human immunodeficiency virus type 1 (HIV-1) is initiated by a temporal progression of interactions between specific cell surface receptors and the viral envelope protein, gp120. These interactions produce a number of intermediate structures with distinct conformational, functional, and antigenic features that may provide important targets for therapeutic and vaccination strategies against HIV infection. One such intermediate, the gp120-CD4 complex, arises from the interaction of gp120 with the CD4 receptor and enables interactions with specific coreceptors needed for viral entry. gp120-CD4 complexes are thus promising targets for anti-HIV vaccines and therapies. The development of such strategies would be greatly facilitated by a means to produce the gp120-CD4 complexes in a wide variety of contexts. Accordingly, we have developed single-chain polypeptide analogues that accurately replicate structural, functional, and antigenic features of the gp120-CD4 complex. One analogue (FLSC) consists of full-length HIV-1BaL gp120 and the D1D2 domains of CD4 joined by a 20-amino-acid linker. The second analogue (TcSC) contains a truncated form of the gp120 lacking portions of the C1, C5, V1, and V2 domains. Both molecules exhibited increased exposure of epitopes in the gp120 coreceptor-binding site but did not present epitopes of either gp120 or CD4 responsible for complex formation. Further, the FLSC and TcSC analogues bound specifically to CCR5 (R5) and blocked R5 virus infection. Thus, these single-chain chimeric molecules represent the first generation of soluble recombinant proteins that mimic the gp120-CD4 complex intermediate that arises during HIV replication.

Recent advances with recombinant bacterial vaccine vectors

Bacille Calmette-Guerin (BCG), Listeria monocytogenes, Salmonellae and Shigellae have shown promise as vaccine vectors in experimental animal models. Although disappointing results in humans and non-human primates stalled the development of this vaccination strategy, interest in this approach was reinvigorated recently by the development of bacterial DNA-vaccine-vectors. The purpose of this review is to highlight the strengths and weaknesses of bacterial vaccine vectors, and to discuss the future prospects of these vaccine delivery systems.

Soluble complexes of regulated upon activation, normal T cells expressed and secreted (RANTES) and glycosaminoglycans suppress HIV-1 infection but do not induce Ca(2+) signaling

Chemokines comprise a family of low-molecular-weight proteins that elicit a variety of biological responses including chemotaxis, intracellular Ca(2+) mobilization, and activation of tyrosine kinase signaling cascades. A subset of chemokines, including regulated upon activation, normal T cell expressed and secreted (RANTES), macrophage inflammatory protein-1alpha (MIP-1alpha), and MIP-1beta, also suppress infection by HIV-1. All of these activities are contingent on interactions between chemokines and cognate seven-transmembrane spanning, G protein-coupled receptors. However, these activities are strongly inhibited by glycanase treatment of receptor-expressing cells, indicating an additional dependence on surface glycosaminoglycans (GAG). To further investigate this dependence, we examined whether soluble GAG could reconstitute the biological activities of RANTES on glycanase-treated cells. Complexes formed between RANTES and a number of soluble GAG failed to induce intracellular Ca(2+) mobilization on either glycanase-treated or untreated peripheral blood mononuclear cells and were unable to stimulate chemotaxis. In contrast, the same complexes demonstrated suppressive activity against macrophage tropic HIV-1. Complexes composed of (125)I-labeled RANTES demonstrated saturable binding to glycanase-treated peripheral blood mononuclear cells, and such binding could be reversed partially by an anti-CCR5 antibody. These results suggest that soluble chemokine-GAG complexes represent seven-transmembrane ligands that do not activate receptors yet suppress HIV infection. Such complexes may be considered as therapeutic formulations for the treatment of HIV-1 infection.

Intracellular delivery of a cytolytic T-lymphocyte epitope peptide by pertussis toxin to major histocompatibility complex class I without involvement of the cytosolic class I antigen processing pathway

A CD8(+) cytolytic T-lymphocyte (CTL) response to antigen-presenting cells generally requires intracellular delivery or synthesis of antigens in order to access the major histocompatibility complex (MHC) class I processing and presentation pathway. To test the ability of pertussis toxin (PT) to deliver peptides to the class I pathway for CTL recognition, we constructed fusions of CTL epitope peptides with a genetically detoxified derivative of PT (PT9K/129G). Two sites on the A (S1) subunit of PT9K/129G tolerated the insertion of peptides, allowing efficient assembly and secretion of the holotoxin fusion by Bordetella pertussis. Target cells incubated with these fusion proteins were specifically lysed by CTLs in vitro, and this activity was shown to be MHC class I restricted. The activity was inhibited by brefeldin A, suggesting a dependence on intracellular trafficking events, but was not inhibited by the proteasome inhibitors lactacystin and N-acetyl-L-leucyl-L-leucyl-L-norleucinal (LLnL). Furthermore, the activity was present in mutant antigen-presenting cells lacking the transporter associated with antigen processing, which transports peptides from the cytosol to the endoplasmic reticulum for association with MHC class I molecules. PT may therefore bypass the proteasome-dependent cytosolic pathway for antigen presentation and deliver epitopes to class I molecules via an alternative route.

A new monoclonal antibody, mAb 4A12, identifies a role for the glycosaminoglycan (GAG) binding domain of RANTES in the antiviral effect against HIV-1 and intracellular Ca2+ signaling

The beta-chemokine RANTES (regulated on activation, normal T cell expressed and secreted) suppresses the infection of susceptible host cells by macrophage tropic strains of HIV-1. This effect is attributed to interactions of this chemokine with a 7-transmembrane domain receptor, CCR5, that is required for virus-cell fusion and entry. Here we identify domains of RANTES that contribute to its biological activities through structure-function studies using a new monoclonal antibody, mAb 4A12, isolated from mice immunized with recombinant human RANTES. This monoclonal antibody (mAb) blocked the antiviral activity of RANTES in infectivity assays with HIV-1Bal, and inhibited the mobilization of intracellular Ca2+ elicited by RANTES, yet recognized this chemokine bound to cell surfaces. Epitope mapping using limited proteolysis, reversed phase high-performance liquid chromatography, and mass spectrometry suggest that residues 55-66 of RANTES, which include the COOH-terminal alpha-helical region implicated as the glycosaminoglycan (GAG) binding domain, overlap the determinant recognized by mAb 4A12. This is supported by affinity chromatography studies, which showed that RANTES could be eluted specifically by heparin from a mAb 4A12 immunoaffinity matrix. Removal of cell surface GAGs by enzymatic digestion greatly reduced the ability of mAb 4A12 to detect RANTES passively bound on cell surfaces and abrogated the ability of RANTES to elicit an intracellular Ca2+ signal. Taken together, these studies demonstrate that the COOH-terminal alpha-helical region of RANTES plays a key role in GAG-binding, antiviral activity, and intracellular Ca2+ signaling and support a model in which GAGs play a key role in the biological activities of this chemokine.

Lipopolysaccharide from an Escherichia coli htrB msbB mutant induces high levels of MIP-1 alpha and MIP-1 beta secretion without inducing TNF-alpha and IL-1 beta

OBJECTIVE

To identify a lipopolysaccharide (LPS) that retains the capacity to induce beta-chemokine secretion without the concomitant activation of pyrogenic cytokines.

METHODS

LPS was extracted from strain MLK986 (mLPS), an htrB1::Tn10, msbB::ocam mutant of Escherichia coli that is defective for lipid A synthesis, and from wild-type parent E coli strains, W3110 (wtLPS). The capacity of these LPS preparations to induce tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and macrophage inflammatory proteins 1 alpha (MIP-1 alpha) and MIP-1 beta was assessed using a human peripheral blood mononuclear cell (PBMC) activation assay.

RESULTS

Stimulation of PBMCs with mLPS did not induce measurable levels of pyrogenic cytokines TNF-alpha and IL-1 beta, whereas wtLPS induced high levels of these cytokines. Furthermore, mLPS antagonized the induction of TNF-alpha secretion by wtLPS. Nonetheless, mLPS retained a discrete agonist activity that induced MIP-1 alpha and MIP-1 beta secretion by PBMCs. This latter agonist activity appears to be unique to mLPS, since two previously documented LPS antagonists, Rhodobacter sphaeroides diphosphoryl lipid A and synthetic lipid IVA, did not induce MIP-1 alpha and MIP-1 beta secretion. Furthermore, synthetic lipid IVA was an antagonist of MIP-1 alpha and MIP-1 beta induction by mLPS.

CONCLUSION

These results show that mLPS exhibits a novel bipartite activity, being an effective antagonist of TNF-alpha induction by wtLPS, while paradoxically being an agonist of MIP-1 alpha and MIP-1 beta secretion.

Induction of mucosal and systemic responses against human immunodeficiency virus type 1 glycoprotein 120 in mice after oral immunization with a single dose of a Salmonella-HIV vector

Previous studies from our group showed that a Salmonella-HIV vector vaccine that expressed recombinant HIV-1 envelope protein gp120 stably in the vector cytoplasm elicited type 1 helper T cell (Th1) responses to gp120. Despite the promise of such vaccines, a major limitation in their use was that multiple immunizations were required to elicit even small responses. For this reason, we sought a modified vector configuration that would induce more potent gp120-specific T cell responses exhibiting a broader spectrum of effector functions after a single inoculation. In this article we describe the construction and immunogenicity of a Salmonella-HIV vector that displays a truncated derivative of HIV-1(IIIB) envelope in the periplasm of the vector. A single oral dose of this Salmonella vector, called H683(pW58-asd+), generated a gp120-specific proliferation response in the spleen 14 days after immunization. In agreement with our previous findings, the gp120-specific splenic CD4+ T cells elicited by H683(pW58-asd+) displayed a Th1 phenotype; however, gp120-specific splenic CD4+ Th2 cells were also evident. In addition, this strain induced strong gp120-specific IgA antibody-secreting cell (ASC) responses in the intestinal lamina propria and mesenteric lymph nodes. As many as 2% of the total lamina propria and mesenteric lymph node IgA ASCs were found to be specific for gp120 28 days after a single oral dose of H683(pW57-asd+). Because the proliferative response following a single dose of H683(pW58-asd+) was comparable to that seen previously after three doses of an analogous construct expressing recombinant gp120 in the cytoplasm, these observations suggest that Salmonella-vectored secreted HIV-1 antigens elicit higher T cell responses than their cytoplasmically bound analogs.

Oral bacterial vaccine vectors for the delivery of subunit and nucleic acid vaccines to the organized lymphoid tissue of the intestine

Bacterial vaccine vectors have the potential to deliver a number of antigens from bacterial, protozoan and viral pathogens. To further develop the utility of bacterial vaccine vectors we are currently evaluating three model systems: 1. A Salmonella-ETEC Vaccine Vector; 2. A Salmonella-HIV Vaccine Vector, and 3. Novel Live Bacterial Nucleic Acid Vaccine Vectors. Through our studies, and those of others, significant progress has been made toward bacterial vaccine vector systems that effectively deliver subunit and nucleic acid vaccines to the organized lymphoid tissue of the intestine. The practical reality of these findings is discussed.

Phage display of intact domains at high copy number: a system based on SOC, the small outer capsid protein of bacteriophage T4

Peptides fused to the coat proteins of filamentous phages have found widespread applications in antigen display, the construction of antibody libraries, and biopanning. However, such systems are limited in terms of the size and number of the peptides that may be incorporated without compromising the fusion proteins' capacity to self-assemble. We describe here a system in which the molecules to be displayed are bound to pre-assembled polymers. The polymers are T4 capsids and polyheads (tubular capsid variants) and the display molecules are derivatives of the dispensable capsid protein SOC. In one implementation, SOC and its fusion derivatives are expressed at high levels in Escherichia coli, purified in high yield, and then bound in vitro to separately isolated polyheads. In the other, a positive selection vector forces integration of the modified soc gene into a soc-deleted T4 genome, leading to in vivo binding of the display protein to progeny virions. The system is demonstrated as applied to C-terminal fusions to SOC of (1) a tetrapeptide; (2) the 43-residue V3 loop domain of gp120, the human immunodeficiency virus type-1 (HIV-1) envelope glycoprotein; and (3) poliovirus VP1 capsid protein (312 residues). SOC-V3 displaying phage were highly antigenic in mice and produced antibodies reactive with native gp120. That the fusion protein binds correctly to the surface lattice was attested in averaged electron micrographs of polyheads. The SOC display system is capable of presenting up to approximately 10(3) copies per capsid and > 10(4) copies per polyhead of V3-sized domains. Phage displaying SOC-VP1 were isolated from a 1:10(6) mixture by two cycles of a simple biopanning procedure, indicating that proteins of at least 35 kDa may be accommodated.

In vitro effects of anti-HIV immunotoxins directed against multiple epitopes on HIV type 1 envelope glycoprotein 160

We have used a panel of anti-gp160 MAbs to construct anti-HIV immunotoxins by coupling antibodies to ricin A chain (RAC). The ability of the immunotoxins to kill HIV-1-infected cells and halt the spread of infection was tested in tissue culture on persistently and acutely infected cell lines and primary lymphocyte cultures stimulated with phytohemagglutinin (PHA blasts). Laboratory strains and clinical isolates of HIV both were tested. The constitution and antigen-binding capacity of the immunotoxins were confirmed by ELISA and indirect immunofluorescence. Immunotoxins that bind epitopes exposed on the cell surface effectively killed persistently infected cells, although killing was not directly proportional to binding of immunotoxin to cell. The activity of anti-gp41, but not anti-gp120, immunotoxins was markedly enhanced in the presence of soluble CD4 or peptides corresponding to the CDR3 region of CD4. CD4-mediated enhancement of anti-gp41 immunotoxin activity was observed for laboratory strains neutralized by sCD4 and for clinical isolates that were resistant to neutralization by sCD4. Immunotoxin action was potentiated by brefeldin A, bafilomycin A1, cortisone, and an amphipathic fusion peptide, but not by cytochalasin D, nocodazol, monodansyl cadaverine, or trans-retinoic acid. Anti-HIV immunotoxins are useful tool with which to study the functional expression of gp120/gp41 antigens on the surface of HIV-infected cells, as well as potential AIDS therapeutics. Because these studies relate to the accessibility of viral antigens to antibody-mediated attack, these studies also have relevance for vaccine development.

Optimization of live oral Salmonella-HIV-1 vaccine vectors for the induction of HIV-specific mucosal and systemic immune responses

Recent evidence suggests that live oral Salmonella-HIV vaccine vectors have the potential to elicit HIV-specific T cell-mediated immunity in both the mucosal and systemic compartments. We are using the mouse-typhoid model to identify Salmonella::HIV vaccine vector constructs that elicit HIV-specific mucosal and systemic immune responses. Oral immunization of mice with a Salmonella strain that expresses recombinant gp120 (rgp120) in the cytoplasm of the vector elicits a modest gp120-specific T cell proliferation response in the spleen. However, such Salmonella constructs did not stimulate the development of gp120-specific serum IgG or cytotoxic T lymphocytes (CTLs). Interestingly, the majority of cytoplasmically-expressed rgp120 forms inclusion bodies in Salmonella. We believe that in this form rgp120 is highly susceptible to protease degradation by the vector. As such, cytoplasmic rgp120 may not persist in the host after vaccination, resulting in the modest immunogenicity of rgp120 in these constructs. To circumvent this problem we constructed Salmonella strains that express rgp120 on the surface of the vector. Preliminary data suggest that surface-expressed rgp120 is significantly more immunogenic in both the mucosal and systemic compartments than cytoplasmic rgp120. These results, therefore, support the proposal that Salmonella vectors will be a safe and inexpensive means for delivery of HIV antigens to, and the elicitation of HIV-specific T cells in, the mucosal and systemic compartments.

Construction and immunogenicity of Salmonella typhimurium vaccine vectors that express HIV-1 gp120

Since the human immunodeficiency virus (HIV-1) is transmitted either parenterally or sexually, both mucosal and systemic immune responses may be required to provide protective immunity. Attenuated Salmonella vectors expressing heterologous antigen can stimulate responses in both compartments. To evaluate the utility of Salmonella vectors as an HIV-1 vector vaccine, a gene expression cassette encoding recombinant HIV-1 gp120 (rgp120) was integrated into the hisOGD locus of Salmonella typhimurium aroA strain, SL3261 (SL3261::120). To test if increased antigen expression potentiates immunogenicity, strains were constructed that express rgp120 from a multicopy asd-stabilized plasmid (SL7207 pYA:120). Immunoblot analysis demonstrated that SL7207 pYA:120 expressed approximately 50-fold more rgp120 than SL3261::120. Oral immunization of BALB/c mice with these strains did not stimulate an env-specific CTL response or a significant rise in antigp120 antibody titer as compared to controls. However, splenic T cells from SL7207 pYA::120 immunized mice proliferated upon restimulation with gp120 in vitro while splenocytes from SL3261::120 immunized mice did not, gp120 restimulated splenic T cells from SL7207 pYA:120 immune mice also produced IFN-gamma but no IL-5. Two conclusions can be drawn from these results. First, high level expression of rgp120 in Salmonella vectors is necessary to stimulate a gp120-specific immune response in mice. Second, Salmonella::rgp120 stimulates a gp120-specific Th1 response in mice. This is the first report to describe the construction of a Salmonella::rgp120 vector vaccine that is immunogenic in mice.

Construction and characterization of a Salmonella typhi-based human immunodeficiency virus type 1 vector vaccine

Since the human immunodeficiency virus type 1 (HIV-1) is transmitted either parenterally or sexually, both systemic and mucosal immune responses might be required to provide protective immunity. One option is to express HIV proteins in attenuated Salmonella vectors that elicit immune responses in both compartments. The first step to constructing such a strain was achieved by integrating a gene expression cassette encoding recombinant HIV-1 gp120 (rgp120) into the aroC locus of an attenuated vaccine strain of S. typhi. This rgp120 expression cassette utilizes the strong constitutive promoter, P1pp/lacUV5, and produces rgp120 to 0.05-01% of the total bacterial cell protein. Immunoblot analysis shows that the S. typhi strains containing the integrated cassette express a protein that is both recognized by anti-gp120 monoclonal antibodies (mAbs) and is the appropriate size for nonglycosylated full-length gp120 (52 kDa). Immunoblot analysis also demonstrates that the recombinant S. typhi strains express the rgp120 as monomers and multimers found predominantly in the insoluble fraction of the bacteria. Antigen-capture ELISA, using antibodies specific for continuous epitopes on gp120, revealed that the exposure of these epitopes on S. typhi-expressed rgp120 differs from exposure of these epitopes on baculovirus-expressed rgp120 that binds CD4. Epitopes in the first conserved region (109-113) and the third conserved/fourth variable regions (376-380, 382-384, 395-400) are more "surface-exposed", while one epitope in the third variable region (313-324) is more "buried" relative to the corresponding epitopes of baculovirus expressed gp120. Antibodies recognizing discontinuous epitopes of the CD4 binding domain do not react with the S. typhi expressed rgp120.(ABSTRACT TRUNCATED AT 250 WORDS)

Absence of high-affinity binding sites for interferon alpha/beta in variant murine CD4+ T lymphocytes not expressing the T cell antigen receptor

The T cell antigen receptor complex (CD3/Ti) plays a role in specific antigen recognition as well as in signal transduction, with its surface expression required for the function of several other structurally distinct receptor systems, including CD2, Ly-6(TAP), and Thy-1. In this communication, evidence is presented suggesting an association between the surface expression of CD3/Ti and that of the type 1 interferon (IFN) receptor in a CD4+ murine T cell clone. We tested the proliferative responses and their capacity to be inhibited by type 1 IFN with the wild-type, CD3/Ti-positive T cell clone and its CD3/Ti-negative variants did not respond to specific antigen or anti-CD3 antibody stimulation but they did respond to T cell growth factor (TCGF), stimulation as did the wild-type parental cells. Therefore, the type 1 IFN inhibition of TCGF-stimulated proliferative responses of wild-type and variant cells were compared. Both natural and recombinant type 1 IFNs inhibited TCGF-induced tritiated thymidine (3H-TdR) incorporation in the wild-type T cell clone, with a ID50 of 60-80 U/ml. By contrast, the variants required much higher doses of type 1 IFN. The ID50 with natural murine IFN-beta was 10,000 U/ml, but this same dose of human IFN-alpha A/D gave only a marginal inhibitory effect. Accompanying the loss of IFN responsiveness, these variants also exhibited a loss of high-affinity type 1 IFN receptors. Taken together, these data suggest that the CD3/Ti complex plays a role in the surface expression of the type 1 IFN receptor in a CD4+ T cell clone.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunological evidence for interactions between the first, second, and fifth conserved domains of the gp120 surface glycoprotein of human immunodeficiency virus type 1

We have used a combination of genetic and immunological techniques to explore how amino acid substitutions in the second conserved (C2) domain of gp120 from human immunodeficiency virus type 1 (HIV-1) affect the conformation of the protein. It was reported previously (R. L. Willey, E. K. Ross, A. J. Buckler-White, T. S. Theodore, and M. A. Martin. J. Viol. 63:3595-3600, 1989) that an asparagine-glutamine (N/Q) substitution at C2 residue 267 of HIV-1 NL4/3 reduced virus infectivity, but that infectivity was restored by a compensatory amino acid change (serine-glutamine; S/N) at residue 128 in the C1 domain. Here we show that the 267 N/Q substitution causes the abnormal exposure of a segment of C1 spanning residues 80 to 120, which compromises the integrity of the CD4-binding site. The reversion substitution at residue 128 restores the normal conformation of the C1 domain and recreates a high-affinity CD4-binding site. The gp120 structural perturbation caused by changes in C2 extends also to the C5 domain, and we show by immunological analysis that there is a close association between areas of the C1 and C5 domains. This association might be important for forming a complex binding site for gp41 (E. Helseth, U. Olshevsky, C. Furman, and J. Sodroski. J. Virol. 65:2119-2123, 1991). Segments of the C1 and C2 domains are predicted to form amphipathic alpha helices. We suggest that these helices might be packed together in the core of the folded gp120 molecule, that the 267 N/Q substitution disrupts this interdomain association, and that the 128 S/N reversion substitution restores it.

Adherence-mediated T cell activation in multiple sclerosis and other neurological disorders

Peripheral blood T cells were isolated from chronic progressive multiple sclerosis patients using a stepwise protocol of density gradient centrifugation, erythrocyte rosetting and adherent cell depletion, after which T cells were cultured with no added stimulus. These cultures exhibited as much as 10-fold higher 'background' proliferative activity (designated hyperactivity) than similarly prepared cultures from normal healthy control individuals. Hyperactivity was also found with T cell cultures from patients with other neurological disorders, i.e. namely, Guillain-Barré syndrome, acute stroke, myasthenia gravis or seizures. Characterizing the hyperactivity, kinetic studies showed that it was not evident until 6 days and became maximal in 8-10 day cultures; it occurred concomitantly with an increase in activated cells; and it was inhibited by anti-HLA-DR antibody, implicating the role of CD4+ T cells. Taken together, these results suggest that the hyperactivity was the result of in vitro stimulation. In further support of this view, hyperactivity was dependent on the adherence step used in the T cell isolation procedure. Although the T cell stimulus and the mechanism underlying the adherence effect is currently speculative, the hyperactivity appears to be the result of a feature common to the diseases in which it was found. The possible roles of inflammatory events in vivo and an autologous mixed lymphocyte response in vitro are discussed.

Epitope mapping and topology of baculovirus-expressed HIV-1 gp160 determined with a panel of murine monoclonal antibodies

To define protein folding patterns of HIV-1 Env subunit vaccines, we have isolated a set of 30 monoclonal antibodies (MAbs) from BALB/c mice immunized with a recombinant gp160 vaccine (rgp160) expressed in a baculovirus system. This article describes epitope mapping for the MAb panel and topology of the epitopes for rgp160 and a recombinant gp120 (rgp120) also expressed in a baculovirus system. The following results are reported: (1) rgp160 harbors a minimum of 4 antigenic domains, 3 mapping to the C1, C2, and C3/V4 regions of gp120 and 1 mapping to the cytoplasmic tail of gp41; (2) there are at least 3 adjacent or overlapping epitopes in each antigenic domain; (3) a minimum of 14 independent epitopes were mapped, all of which are continuous sites; (4) each of the epitopes is exposed on rgp160 without prior manipulation of the protein; and (5) by contrast, 6 of the 8 epitopes mapping to the C1, C2, and C3/V4 regions are not exposed on rgp120, but become exposed when the protein is denatured. Taken together, these results show that rgp160 and rgp120 are folded differently, illustrating the use of this MAb panel to compare epitope topographies of recombination HIV-1 Env proteins. This MAb panel may aid in the refinement of HIV-1 Env subunit vaccines.

Actin polymerization and pseudopod reorganization accompany anti-CD3-induced growth arrest in Jurkat T cells

T cell activation via CD3/Ti linked pathways results in the polymerization and reorganization of actin. However, little is known about the morphology and temporal appearance of filamentous actin (F-actin) after activation. Similarly, little is known about the relationship between F-actin and changes in cell shape or other parameters of activation, such as the appearance of proteins newly phosphorylated on tyrosine, that occur after stimulation via the CD3/Ti complex. Accordingly, we have characterized changes in cell shape and F-actin morphology occurring in the Jurkat T cell leukemia attached to the surface of culture vessels by immobilized anti-CD3 antibodies (OKT3, UCHT-1, SPV-T3b). These antibodies induced activation within 30 min as measured by increased protein tyrosine kinase activity and conversion of the proto-oncogene product, lck, from 56 kDa to 60 kDa (p56lck conversion), and after 12 to 96 h as measured by growth arrest and, in some experiments, IL-2 production. Activation was not seen when cells were attached to the substrates using antibodies directed to other cell surface proteins including CD71 (transferrin receptor), CD7, and CD11a (LFA-1), demonstrating the specificity of activation for immobilized anti-CD3 antibodies. Temporal changes in cell shape and F-actin morphology were characterized in Jurkat cells attached by immobilized anti-CD3 antibodies (stimulatory antibodies) and compared with the patterns obtained obtained in Jurkat cells attached by antibodies specific for the other markers (nonstimulatory antibodies). In these experiments, Jurkat cells were incubated with antibody-coated substrates for 1 to 30 min at 37 degrees C and actin rearrangements were visualized on fixed, detergent-permeabilized cells using rhodamine-conjugated phalloidin. Analysis of cell shape and F-actin morphology during the first 30 min of activation revealed a unique pattern that was observed only when cells were stimulated with anti-CD3 antibodies. Jurkat cells attached by either stimulatory or nonstimulatory antibodies reorganized their actin similarly after the first minute of culture, as characterized by the formation of small, F-actin rich pseudopods at the sites of attachment. After 5 min of culture in cells attached by stimulatory antibodies, the actin was polymerized into a dense collar rimming the inner edge of the cell. From 15 to 60 min, this collar was replaced by numerous F-actin rich, branched pseudopods. These branched pseudopods were larger and had longer microfilament bundles than their earlier counterparts. By contrast, in cells attached by nonstimulatory antibodies, the initial configuration was maintained for at least 60 min, except that a decrease in microfilament bundle length was noted.(ABSTRACT TRUNCATED AT 400 WORDS)

Actin polymerization and pseudopod reorganization accompany anti-CD3-induced growth arrest in Jurkat T cells

T cell activation via CD3/Ti linked pathways results in the polymerization and reorganization of actin. However, little is known about the morphology and temporal appearance of filamentous actin (F-actin) after activation. Similarly, little is known about the relationship between F-actin and changes in cell shape or other parameters of activation, such as the appearance of proteins newly phosphorylated on tyrosine, that occur after stimulation via the CD3/Ti complex. Accordingly, we have characterized changes in cell shape and F-actin morphology occurring in the Jurkat T cell leukemia attached to the surface of culture vessels by immobilized anti-CD3 antibodies (OKT3, UCHT-1, SPV-T3b). These antibodies induced activation within 30 min as measured by increased protein tyrosine kinase activity and conversion of the proto-oncogene product, lck, from 56 kDa to 60 kDa (p56lck conversion), and after 12 to 96 h as measured by growth arrest and, in some experiments, IL-2 production. Activation was not seen when cells were attached to the substrates using antibodies directed to other cell surface proteins including CD71 (transferrin receptor), CD7, and CD11a (LFA-1), demonstrating the specificity of activation for immobilized anti-CD3 antibodies. Temporal changes in cell shape and F-actin morphology were characterized in Jurkat cells attached by immobilized anti-CD3 antibodies (stimulatory antibodies) and compared with the patterns obtained obtained in Jurkat cells attached by antibodies specific for the other markers (nonstimulatory antibodies). In these experiments, Jurkat cells were incubated with antibody-coated substrates for 1 to 30 min at 37 degrees C and actin rearrangements were visualized on fixed, detergent-permeabilized cells using rhodamine-conjugated phalloidin. Analysis of cell shape and F-actin morphology during the first 30 min of activation revealed a unique pattern that was observed only when cells were stimulated with anti-CD3 antibodies. Jurkat cells attached by either stimulatory or nonstimulatory antibodies reorganized their actin similarly after the first minute of culture, as characterized by the formation of small, F-actin rich pseudopods at the sites of attachment. After 5 min of culture in cells attached by stimulatory antibodies, the actin was polymerized into a dense collar rimming the inner edge of the cell. From 15 to 60 min, this collar was replaced by numerous F-actin rich, branched pseudopods. These branched pseudopods were larger and had longer microfilament bundles than their earlier counterparts. By contrast, in cells attached by nonstimulatory antibodies, the initial configuration was maintained for at least 60 min, except that a decrease in microfilament bundle length was noted.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunochemical analysis of the gp120 surface glycoprotein of human immunodeficiency virus type 1: probing the structure of the C4 and V4 domains and the interaction of the C4 domain with the V3 loop

We have probed the structure of the C4 and V3 domains of human immunodeficiency virus type 1 gp120 by immunochemical techniques. Monoclonal antibodies (MAbs) recognizing an exposed gp120 sequence, (E/K)VGKAMYAPP, in C4 were differentially sensitive to denaturation of gp120, implying a conformational component to some of the epitopes. The MAbs recognizing conformation-sensitive C4 structures failed to bind to a gp120 mutant with an alteration in the sequence of the V3 loop, and their binding to gp120 was inhibited by both V3 and C4 MAbs. This implies an interaction between the V3 and C4 regions of gp120, which is supported by the observation that the binding of some MAbs to the V3 loop was often enhanced by amino acid changes in an around the C4 region.

A hidden region in the third variable domain of HIV-1 IIIB gp120 identified by a monoclonal antibody

The third variable domain (V3 domain) of HIV-1 gp120 is involved in virus neutralization by antibody, in determination of cell tropism, and in syncytium-inducing/non-syncytium-inducing capacity. Antibodies are highly specific tools to delineate the role of different V3 amino acid sequences in these processes, and to dissect events occurring during synthesis of gp120/160, gp120-CD4 interaction, cellular infection, and syncytium formation. We describe here an IgG1 murine monoclonal antibody (MAb), coded IIIB-V3-01, that was raised with a synthetic peptide (FVTIGKIGNMRQAHC) derived from the carboxy-terminal flank of the HIV-1 IIIB V3 domain. The binding site of this antibody was mapped to the sequence IGKIGNMRQ, using Pepscan analysis. In ELISA, this antibody binds to E. coli-derived gp120 from HIV-1 IIIB, which is denatured and not glycosylated. The antibody showed no neutralizing activity against HIV-1 IIIB, MN, SF2, or RF in a virus neutralization assay and in a syncytium formation inhibition assay. In addition, this antibody did not react with gp120 expressed on the surface of IIIB-infected MOLT-3 cells in FACS analysis. To assess whether the epitope defined by MAb IIIB-V3-01 is hidden on native gp120, reactivity of the antibody with SDS-DTT-denatured or DTT-denatured glycosylated gp120 (CHO cell produced) was tested. Both these treatments exposed the epitope for binding. From these data we conclude that the epitope defined by MAB IIIB-V3-01 is hidden on glycosylated recombinant gp120, and is not accessible on gp120 expressed on the membrane of HIV-1, IIIB-infected cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Differences in the antibody response to human immunodeficiency virus-1 envelope glycoprotein (gp160) in infected laboratory workers and vaccinees

Studies of the immune response to the human immunodeficiency virus (HIV) have been hampered by the antigenic diversity of the HIV envelope protein. In an effort to predict the efficacy of vaccination we have compared the systemic anti-envelope antibody response in seronegative volunteers immunized with recombinant gp160 (either in vaccinia or as soluble protein produced in baculovirus) derived from the HTLV-IIIB strain of HIV-1 and in two laboratory workers accidentally infected with the same strain. 11 of 14 vaccinees responded to immunization by producing anti-gp160 of similar titer and the same isotype as that seen in the laboratory workers. Four vaccinees also had antibody to the principal neutralizing domain (V3 loop) that was comparable in titer with that seen in the laboratory workers, but the fine specificity of anti-V3 antibody was qualitatively different in the two groups. Antibody that can block the interaction between CD4 and gp120 was present at comparable levels in three vaccines and the lab workers. Neutralizing antibody titers were markedly lower in the vaccinees than in the laboratory workers. In seven of the vaccinees, an immunodominant epitope was at amino acid 720-740. Analyses of monoclonal antibodies to this region indicate that they do not neutralize, bind to infected cells, nor function as immunotoxins. Although the anti-gp160 antibody response was of similar magnitude in both infected and vaccinated individuals, there were important qualitative differences.

Effects of human salivas on recombinant HIV-1 proteins

Human saliva appears to contain factors that are inhibitory to HIV-1 infectivity in vitro. We investigated the effect of incubating human whole, parotid, labial minor salivary gland and sublingual/submandibular salivas with recombinant HIV-1 envelope protein (gp160). Saliva/gp160 mixtures were run on polyacrylamide gels, transferred to nitrocellulose, and assayed for the presence of gp160 using monoclonal antibodies or HIV-1-positive sera. Incubation of the gp160 with whole saliva reduced the intensity of gp160 bands to 35% of control values. Minor salivary gland saliva reduced the band intensities to 65% of control values, while other saliva types diminished gp160 to 75% of control values. Protease inhibitors had no effect. Components of untreated whole human saliva prevent the detection of the HIV-1 envelope protein gp160 by antibodies to gp120 and gp41 in immunoblots. The results suggest that complexes between whole saliva factors and certain domains of gp160 block monoclonal antibody binding or are unable to migrate through polyacrylamide gels.

Intrinsic immunogenicity of an internal VP1 T-B epitope pair of type 1 poliovirus

We describe the intrinsic immunogenicity of a poliovirus T-B epitope pair that is located in the N-terminus of the capsid protein VP1. This peptide is unusual in that it is located on the interior of the native virion at the VP1-VP3 interface in a region that becomes exposed after cell binding, proteolysis, or heating of the virus. Immunization of mice with either the virion or free peptide leads to anti-peptide antibody production. Anti-peptide immunity is under genetic control and 1-Ak restricted T cell proliferative responses have been identified. SJL/J (H-2s) mice that are low responders to this T-B epitope pair are also low responders to PSV-1 itself, suggesting that this site may be important in the production of neutralizing anti-PSV-1 antibodies. Interestingly, seropositive humans also have significant anti-peptide titers suggesting that immunization with poliovirus in a species permissive for infection also leads to anti-peptide antibody production. Collectively, these data suggest that a T-B epitope pair located on the interior of a protein or virion can be immunogenic. Several mechanisms whereby internal T-B epitope pairs might become immunogenic are discussed.

Variant-specific monoclonal and group-specific polyclonal human immunodeficiency virus type 1 neutralizing antibodies raised with synthetic peptides from the gp120 third variable domain

The third variable (V3) domain of the human immunodeficiency virus type 1 (HIV-1) external membrane glycoprotein gp120 is of crucial importance in eliciting neutralizing antibodies in infected persons. Polyclonal (PAb) and monoclonal (MAb) antibodies directed against selected epitopes in the V3 domain are valuable tools for analysis of the involvement of such sequences in neutralization and for definition of the relation between amino acid variability and immunological cross-reactions. The aim of this study was to obtain such site-specific antibodies. By using synthetic peptides derived from the V3 domain, a group-specific neutralizing PAb, two high-affinity HIV-1 IIIB neutralizing MAb, and two nonneutralizing MAb were raised. A 15-amino-acid peptide overlapping the tip of the V3 domain of HIV-1 MN was used to produce a rabbit PAb (W0/07). This PAb inhibited syncytium formation induced by HIV-1 IIIB and four field isolates. A similar IIIB-derived peptide was used to generate two murine immunoglobulin G1 (IgG1) MAb (IIIB-V3-13 and IIIB-V3-34). Pepscan analysis mapped the binding site of IIIB-V3-34 to the sequence IRIQRGPGR. The Kds of IIIB-V3-13 and IIIB-V3-34 for gp120 were 6.8 x 10(-11) and 1.6 x 10(-10) M, respectively. These MAb neutralized IIIB but not MN and inhibited syncytium formation induced by IIIB. They are applicable in enzyme-linked immunosorbent assays, immunocytochemistry, and flow cytometry. A peptide covering the left base of the V3 domain was used to generate two murine IgG1 MAb (IIIB-V3-21 and IIIB-V3-26). The binding site of IIIB-V3-21 was mapped to the sequence INCTRPN. These MAb did not neutralize HIV-1 and did not inhibit syncytium formation. This study supports the notion that HIV-1 neutralizing antibodies suitable for multiassay performance can be obtained with synthetic peptides and that high-affinity MAb can be generated. Such site-specific antibodies are useful reagents in the analysis of HIV-1 neutralization. In addition, the cross-neutralization of different viral strains by PAb generated through single-peptide immunization is directly relevant to vaccine development.

Characterization of the binding of radioiodinated hybrid recombinant IFN-alpha A/D to murine and human lymphoid cell lines

The hybrid recombinant human interferon (IFN) rIFN-alpha A/D was radioiodinated. Specific binding of [125I]rIFN-alpha A/D was observed with both human and murine cell lines. The binding of [125I]rIFN-alpha A/D to human Daudi cells had similar characteristics to the previously described binding of [125I]rIFN-alpha A or -alpha 2. The following lines of evidence demonstrated that [125I]rIFN-alpha A/D bound with high affinity to the same receptor on murine cells as murine IFN-alpha and -beta: (i) the binding of [125I]rIFN-alpha A/D to murine LBRM cells was inhibited to a similar extent by natural murine IFN-alpha, natural murine IFN-beta, and rIFN-A/D; (ii) the Kd (approximately 2 X 10(-10) M) obtained from both competition experiments and saturation binding experiments with [125I]rIFN-alpha A/D was comparable to the previously reported Kd for the binding of natural murine IFN-alpha and -beta to other murine cell lines; (iii) the size of the cross-linked [125I]rIFN-alpha A/D receptor complex formed on murine LBRM cells was similar to the previously reported cross-linked complex formed after binding radioiodinated natural murine IFN-beta to other murine cell lines. Due to the current lack of readily available recombinant murine IFN-alpha or -beta for radiolabeling and the previously demonstrated biological activity of rIFN-alpha A/D on murine cells, [125I]rIFN-alpha A/D should prove to be a useful reagent for further studies of murine IFN receptors.

Arsonate-specific murine T cell clones. III. Correlation between clonotype expression and fine specificity for analogs of L-tyrosine-p-azobenzenearsonate

Despite recent advances in our understanding of T cell antigen receptor structure, relatively little is known about the role of this receptor in MHC-restricted antigen recognition. To study this problem, we have developed a panel of ABA-Tyr-reactive, I-Ak-restricted T cell clones that differ in their ability to recognize structural analogs of ABA-Tyr. Three fine specificity groups have been defined. In each group, ABA-Tyr elicited the strongest response of any of the antigens tested. Group I clones responded to ABA-conjugated hydroxyphenyl-ethanol (ABA-HPE). Group II clones responded to ABA-conjugated hydroxyphenyl-methanol (ABA-HPM) but not to ABA-HPE, and group III clones responded only to ABA-Tyr. These studies show that differences as small as a single methylene group can dramatically affect fine specificity. Because these clones are all I-Ak-restricted, it was possible to correlate receptor serology with fine specificity. To this end, monoclonal anti-clonotypes were made against clone 16-F2 from group I and used to study the relationship between fine specificity and clonotype expression. A panel of 15 T cell clones studied with four anti-clonotype antibodies showed a strict correlation between clonotype expression and fine specificity. Taken together, these data suggest that the structure recognized by the anti-clonotype antibodies is a determinant of receptor fine specificity.

Arsonate-specific murine T cell clones. III. Correlation between clonotype expression and fine specificity for analogs of L-tyrosine-p-azobenzenearsonate

Despite recent advances in our understanding of T cell antigen receptor structure, relatively little is known about the role of this receptor in MHC-restricted antigen recognition. To study this problem, we have developed a panel of ABA-Tyr-reactive, I-Ak-restricted T cell clones that differ in their ability to recognize structural analogs of ABA-Tyr. Three fine specificity groups have been defined. In each group, ABA-Tyr elicited the strongest response of any of the antigens tested. Group I clones responded to ABA-conjugated hydroxyphenyl-ethanol (ABA-HPE). Group II clones responded to ABA-conjugated hydroxyphenyl-methanol (ABA-HPM) but not to ABA-HPE, and group III clones responded only to ABA-Tyr. These studies show that differences as small as a single methylene group can dramatically affect fine specificity. Because these clones are all I-Ak-restricted, it was possible to correlate receptor serology with fine specificity. To this end, monoclonal anti-clonotypes were made against clone 16-F2 from group I and used to study the relationship between fine specificity and clonotype expression. A panel of 15 T cell clones studied with four anti-clonotype antibodies showed a strict correlation between clonotype expression and fine specificity. Taken together, these data suggest that the structure recognized by the anti-clonotype antibodies is a determinant of receptor fine specificity.

Multistep transformation by defined fragments of herpes simplex virus type 2 DNA: oncogenic region and its gene product

Diploid Syrian hamster embryo cells transfected with Bgl II C fragment of herpes simplex virus type 2 DNA acquired a neoplastic phenotype. Cultures transfected with its left-hand 64% subclone EcoRI/HindIII fragment AE (0.419-0.525 map unit) grew into established but nontumorigenic lines. Transfection of EcoRI/HindIII AE-immortalized cells with a 4.4-kilobase Sac I/BamHI subfragment within BamHI E (0.554-0.584 map unit; overlaps the right-hand 16% of Bgl II C) converted them to tumorigenicity. The 4.4-kilobase subfragment encodes a 144-kDa protein immunologically and structurally similar to an infected cell protein designated ICP 10. DNA extracted from cells transformed with the 4.4-kilobase subfragment exhibited discrete hybridizing bands homologous to BamHI E fragment. Monoclonal antibody to ICP 10 precipitated a 144-kDa protein from the transformed cells and stained them in immunofluorescence. A tumor derivative established with the transformed cells did not stain with this antibody, but approximately equal to 25% of the cells stained with a monoclonal antibody to c-myc protooncogene products.

Isolation of monoclonal antibodies specific for human c-myc proto-oncogene product

Six monoclonal antibodies have been isolated from mice immunized with synthetic peptide immunogens whose sequences are derived from that of the human c-myc gene product. Five of these antibodies precipitate p62c-myc from human cells, and three of these five also recognize the mouse c-myc gene product. None of the antibodies sees the chicken p110gag-myc protein. All six antibodies recognize immunoblotted p62c-myc. These reagents also provide the basis for an immunoblotting assay by which to quantitate p62c-myc in cells.

Idiotypic properties of the murine anti-arsonate antibody response: B- and T-cell influences

In a previous report characterizing the arsonate (ABA)-specific plaque-forming cell (PFC) responses of A/J mice induced by ABA-KLH, two interesting characteristics of the idiotypic (Id) profile were noted: (1) an apparent Id selectivity in the isotype switch since the earliest appearing IgG PFC in the primary response were significantly more "cross-reactive Id" (CRI)-dominant than the IgM PFC population, and, (2) a temporal waning of CRI dominance with time among IgG PFC, from 75-100% CRI+ PFC to about 25-45% CRI+ PFC in secondary responses. Experiments were performed to determine whether these effects are largely attributable to T or to B cells. Mice were immunized with a T-independent (TI) form of ABA (ABA-Brucella abortus) and apparent Id selectivity was observed; the earliest IgG PFC averaged 75% CRI+ while IgM PFC were only 39% CRI+. Due to the TI nature of the Ag, this provides suggestive, but not conclusive, evidence that the Id asymmetry in the isotype switch may be attributable to the direct interaction of Ag with B cells. Other studies addressed the temporal shift in CRI dominance. First, it was found that preexposure of mice to either KLH or to ABA (on an irrelevant carrier) resulted in diminished CRI dominance in subsequent "primary" responses to ABA-KLH. Secondly, adoptive transfer experiments with B and T cells from virgin mice (Bv, Tv) or ABA-KLH-primed mice (Bp, Tp) showed that recipients of Bv + Tp or Bp + Tv generated anti-ABA PFC responses with intermediate CRI levels. The Tv cells had some preferential tendency to activate CRI+ clones in the Bp population. The results demonstrate that CRI levels are jointly determined by the immune status of both B and T cells. A simple model is offered which accounts for early Id dominance and its gradual decline and has as its central postulate the assumption that CRI+ B cells in the virgin ABA-specific repertoire have an affinity advantage over CRI- clones.

Antibodies to the scrapie protein decorate prion rods

Scrapie is a degenerative, transmissible neurologic disease of sheep and goats which occurs in the absence of any detectable host immune response. Antibodies to the scrapie agent have been produced after immunization of rabbits with either scrapie prions or the prion protein, PrP 27-30, purified from infected hamster brain. Immunoreactivity of the antisera was assessed by dot and Western immunoblots with purified prions and PrP 27-30. Antibodies raised against infectious prions were more immunoreactive with native than denatured preparations, whereas those raised against PrP 27-30 were more reactive with denatured prion preparations. As determined by second antibody-colloidal gold, both antisera were found to decorate scrapie prion rods in purified preparations. Antibodies to cellular filamentous proteins failed to react with PrP 27-30 or the scrapie prion rods; conversely, antibodies to PrP 27-30 did not exhibit immunoreactivity with cellular filamentous proteins. The monospecificity of the rabbit antiserum raised against PrP 27-30 was established by its reactivity after affinity purification. The purified antibodies reacted with PrP 27-30 on Western blots and with the prion rods. Considerable evidence indicates that the scrapie rods are aggregates of infectious prions; the findings presented here provide an immunologic demonstration that PrP 27-30 is a structural component of the prion rods.

Antibodies to the scrapie protein decorate prion rods

Scrapie is a degenerative, transmissible neurologic disease of sheep and goats which occurs in the absence of any detectable host immune response. Antibodies to the scrapie agent have been produced after immunization of rabbits with either scrapie prions or the prion protein, PrP 27-30, purified from infected hamster brain. Immunoreactivity of the antisera was assessed by dot and Western immunoblots with purified prions and PrP 27-30. Antibodies raised against infectious prions were more immunoreactive with native than denatured preparations, whereas those raised against PrP 27-30 were more reactive with denatured prion preparations. As determined by second antibody-colloidal gold, both antisera were found to decorate scrapie prion rods in purified preparations. Antibodies to cellular filamentous proteins failed to react with PrP 27-30 or the scrapie prion rods; conversely, antibodies to PrP 27-30 did not exhibit immunoreactivity with cellular filamentous proteins. The monospecificity of the rabbit antiserum raised against PrP 27-30 was established by its reactivity after affinity purification. The purified antibodies reacted with PrP 27-30 on Western blots and with the prion rods. Considerable evidence indicates that the scrapie rods are aggregates of infectious prions; the findings presented here provide an immunologic demonstration that PrP 27-30 is a structural component of the prion rods.

Arsonate-specific murine T cell clones. II. Delayed-type hypersensitivity induced by P-azobenzenearsonate-L-tyrosine (ABA-Tyr)

To study T cell idiotype expression at the functional level, we developed a hapten-specific delayed-type hypersensitivity (DTH) system by which we avoid the complication of anti-hapten antibody and which is specific only for the immunizing hapten, and not for conjugate specific determinants. Immunization with ABA-Tyr and challenge with ABA diazonium induced footpad swelling with the characteristics of DTH. Anti-ABA antibodies did not contribute to this reaction, as they were undetectable in mice immunized with ABA-Tyr. Furthermore, this ABA-Tyr-specific DTH was under Ir gene control identical to that reported for ABA-Tyr-specific lymphocyte proliferation. All mouse strains tested responded to ABA-Tyr except those of the b haplotype across the entire Ia region. In contrast, contact sensitivity induced by ABA diazonium was not under apparent Ir gene control, probably reflecting 1) different specificities of the induced T cells and 2) the production of anti-ABA antibodies that contribute to the footpad swelling via an Arthus reaction. Having shown that ABA-Tyr can induce T cells mediating DTH, we then examined ABA-Tyr-reactive T cell clones, propagated in vitro, for their ability to mediate DTH. Such clones elicited a response identical to that seen with in vivo immunization with respect to dose dependency, I-Ak restriction, and antigen specificity.