Human T-cell lymphotropic virus type III (HTLV-III) core antigens: synthesis in Escherichia coli and immunoreactivity with human sera

Fragments of human T-cell lymphotropic virus type III (HTLV-III) proviral DNA carrying the gene for the core antigen (gag) was cloned in the plasmid REV. Several of the recombinants direct high levels of synthesis of the antigens. One clone, pG1, produced a hybrid protein containing 13 amino acid residues of the carboxyl terminus of the 17 kD virion protein, the entire p24, the major core protein of HTLV-III, and 74 amino acid residues of the amino terminal of the 15 kD core ribonucleoprotein. A second clone, pG2, was similar to pG1 except that it contained no p17 sequences and was missing the amino-terminal 77 amino acid residues of the p24. A third clone, pG3, was similar to pG2, except that all but 56 amino acids of the carboxyl terminus of p24 were removed. All three proteins were found to be strongly immunoreactive with anti-HTLV-III antibodies present in sera from patients with acquired immune deficiency syndrome (AIDS) or AIDS-related complex (ARC). In addition, pG1 and pG2, but not pG3, reacted with a monoclonal antibody (M26) specific for the p24 virion core protein. Whereas all three reacted with an anti-p15 monoclonal antibody, none of the clones reacted with an anti-p17 monoclonal antibody. These results provide direct evidence to support the predicted assignment of the coding region of the gag gene of HTLV-III. The product from pG2 was purified and was found to be potentially useful for the detection of anti-p24 antibodies in sera from patients with AIDS or ARC and from individuals at risk from AIDS.

Clostridium difficile colitis mimicking acute peritonitis

Five patients receiving penicillin V potassium or a cephalosporin antibiotic for 18 hours to 22 days developed fever, marked leukocytosis, and signs and symptoms that suggested right-lower-quadrant peritoneal irritation. All underwent emergency laparotomy, at which dilatation and inflammation of the ascending colon were found. Only one of the patients had profuse diarrhea, and two patients had no diarrhea prior to laparotomy. Postoperatively, Clostridium difficile colitis was diagnosed by stool toxin assay and was confirmed in one case by proctosigmoidoscopic biopsy results. Antibiotic-associated colitis must be considered in any patient who develops peritoneal signs while or after receiving antibiotics. Over a two-year period, the "acute abdomen" presentation accounted for 5.2% of all patients with C difficile colitis at our institutions. Early proctosigmoidoscopy or stool examination for C difficile or its toxin may avoid unnecessary laparotomy in such patients.

Regulation of the human immune response to HBsAg: effects of antibodies and antigen conformation in the stimulation of helper T cells by HBsAg

The role of accessory cells (antigen-presenting cells) in binding HBsAg in the response of human T cells to this antigen was studied. Antibodies to HBsAg of IgG class increased significantly the amount of HBsAg that was captured and internalized by accessory cells in vitro. On the other hand, antibodies to HBsAg of IgM class or the F(ab')2 and Fab fragments of antibodies to HBsAg of IgG class did not modify the amount of HBsAg associated to these cells. HBsAg that was subjected to various denaturing treatments (acid, organic solvents, urea and heat) was compared for its capacity to react with antibody to HBsAg and stimulate the response of helper T lymphocytes. Results presented here indicate that HBsAg denatured by treatment with formic acid was captured by accessory cells and presented to the T cells much more efficiently than the native HBsAg. These results suggest that the response of helper T lymphocytes to some antigens such as HBsAg can be affected greatly by the presence of antibodies or the antigens' conformation.

An HTLV-III peptide produced by recombinant DNA is immunoreactive with sera from patients with AIDS

Human T-cell lymphotropic retrovirus type III (HTLV-III), also called lymphadenopathy-associated virus (LAV), has been identified as the aetiological agent of acquired immune deficiency syndrome (AIDS). The sera of most patients with AIDS or AIDS-related complexes, and of asymptomatic individuals infected with HTLV-III, contain antibodies against antigens of HTLV-III. The characterization of these antibodies and their corresponding viral antigens is important not only for understanding immunity against HTLV-III and the pathology of AIDS, but also for the development of diagnostic methods and preventive vaccine for AIDS. Following the successful establishment of a long-term T-cell line permissive for HTLV-III replication, large quantities of virus have been produced, facilitating the purification of viral proteins and the development of mouse monoclonal antibodies against several viral antigens. More recently, the structure of HTLV-III proviral DNA has been elucidated. We now report the production, by genetic engineering methods, of a peptide encoded by a gene segment of HTLV-III. A 1.1-kilobase (kb) EcoRI DNA segment from an isolate of HTLV-III was inserted into a lpp and lac promoter-coupled expression vector, pIN-III-ompA. Escherichia coli transformants of this plasmid produced a peptide of relative molecular mass (Mr) 15,000 (15K) which was strongly immunoreactive with anti-HTLV-III antibodies present in sera from AIDS patients. Lysates of the clones expressing this 15K peptide inhibited the reactivity of the p31 virion protein with AIDS sera, suggesting that it is a fragment of the viral p31 protein. The peptide reacted with sera from all 20 AIDS patients but none of the 8 normal controls tested. These results suggest that the peptide may be useful for detecting anti-HTLV-III antibodies in blood samples.

Expression in Escherichia coli of open reading frame gene segments of HTLV-III

Human T-cell lymphotropic virus type III (HTLV-III), the causative agent of the acquired immune deficiency syndrome (AIDS), was recently isolated and its genomic structure analyzed by DNA cloning methods. In the studies reported here a combined cloning and expression system was used to identify HTLV-III encoded peptides that react immunologically with antibodies in sera from AIDS patients. Cloned HTLV-III DNA was sheared into approximately 500-base-pair fragments and inserted into an "open reading frame" expression vector, pMR100. The inserted DNA was expressed in Escherichia coli transformants as a polypeptide fused to the lambda CI protein at its amino terminus and to beta-galactosidase at its carboxyl terminus. Sera from AIDS patients containing antibodies to HTLV-III were then used to screen for immunoreactive fusion proteins. Twenty clones, each specifying a fusion protein strongly reactive with AIDS serum, were identified. DNA sequence analysis indicated that the HTLV-III fragments were derived from the open reading frame DNA segments corresponding to the gag and pol gene coding regions and also the large open reading frame region (env-lor) located near the 3' end of the viral genome.

Monoclonal antibodies as structural probes for oligomeric human interferon-gamma

Monoclonal antibodies (MAb) B1 and B3, specific for human interferon-gamma (IFN-gamma) failed to immunoprecipitate heat-inactivated human IFN-gamma in solution. However, both MAb retained some reactivity with denatured IFN-gamma immobilized on vinyl plates. The two MAb have been employed in a sensitive immunoradiometric assay (IRMA). In this IRMA one MAb was bound to polystyrene beads and used as immunoadsorbent. The second MAb, labeled with 125I, was used as the tracer to quantitate the amount of IFN-gamma bound to the immobilized MAb. Addition of unlabeled MAb B1 did not inhibit the binding of 125I-labeled MAb B3 (and vice versa), indicating that the two MAb react with two different and nonoverlapping epitopes. Yet, when the same MAb was used in IRMA as both immunoadsorbent and tracer, the amount of labeled MAb bound to a given concentration of natural or E. coli-derived recombinant human IFN-gamma was very similar as with two different MAb, indicating that a single IFN-gamma molecule must have two or more identical binding sites for each of the two MAb. These findings show that biologically active natural and recombinant human IFN-gamma exist in oligomeric form.

Antigen-induced production of lymphokines by human T cell clones specific for hepatitis B surface antigen

The secretion of gamma-interferon (IFN-gamma), Interleukin-2 (IL-2), and B cell growth factor (BCGF) by human T cell clones specific for hepatitis B surface antigen (HBsAg) was examined. Antigenic stimulation by HBsAg but not by influenza A virus resulted in IFN-gamma and BCGF synthesis by the T cell clones. No detectable amounts of IL-2 were obtained in the supernatants of any of the HBsAg-specific T cell clones when cultured in the presence or absence of antigen. IFN-gamma and BCGF were produced, even when cell proliferation was inhibited, suggesting that the secretion of these T cell factors occurred regardless of cell proliferation. The significance of the various factors in the immune response against hepatitis B virus infection is discussed.

HBsAg-serum protein complexes stimulate immune T lymphocytes more efficiently than do pure HBsAg

HBsAg from plasma of chronic hepatitis B carriers was purified by affinity chromatography using a mouse monoclonal antibody specific for HBsAg. Elution with buffer at two different pH values separated HBsAg into two fractions: one contained high amounts of immune complexes associated with HBsAg; the other contained larger quantities of the HBsAg polypeptides P24 and GP27 and only small amounts of immunoglobulin. When compared for effects on stimulating the proliferative response of freshly isolated lymphocytes and an HBsAg-specific T cell clone, the HBsAg fraction containing a high proportion of immunoglobulin was much more potent than HBsAg with low amounts of immunoglobulins or pure HBsAg, which was isolated from the culture supernatant of the human hepatoma cell line (PLC/PRF/5). The plasma-derived HBsAg with low amounts of complexed immunoglobulins became more immunogenic in the presence of an anti-HBsAg monoclonal IgG. The present results, combined with earlier findings, suggest that HBsAg associated with immune complexes is a more potent stimulator of T cells than purer HBsAg preparations due to an increase in the efficiency of monocytes to capture the antigen through binding to immune complexes for subsequent processing and presentation of the antigen. These observations could be of relevance for the preparation of effective hepatitis B vaccines from recombinant DNA and peptide synthesis technologies.

Regulation of T-cell function by antibodies: enhancement of the response of human T-cell clones to hepatitis B surface antigen by antigen-specific monoclonal antibodies

Eight mouse monoclonal antibodies specific for hepatitis B surface antigen (HBsAg) were examined for their effects on the antigen-induced proliferative response and lymphokine production of human HBsAg-specific T-cell clones in vitro. While all specifically enhanced the T-cell proliferative response, antibodies of the IgG class were generally more effective than those of the IgM class. Both the divalent F(ab')2 and the monovalent Fab fragments of an IgG monoclonal antibody had no effects, indicating that the Fc portion of the antibody molecules was required. Since antigen-presenting cells bear surface receptors for the Fc of IgGs and fewer or none for that of IgMs, the above results also suggest that antibodies enhance the capture of antigens by antigen-presenting cells as a result of the binding of antigen-antibody complexes to the Fc receptors on these cells. In addition to potentiating the proliferation of the T-cell clones, antibodies also increased the antigen-induced production of interferon-gamma by these cells. The present in vitro studies suggest that antibodies may regulate immune responses and do so by enhancing antigen presentation and thus augmenting antigen-induced activation and clonal expansion of T cells.

Vesiculobullous lesions caused by cytomegalovirus infection in an immunocompromised adult

Skin involvement in cytomegalovirus (CMV) infection is very rare. Reported cutaneous manifestations are nonspecific and include petechial, purpuric, and morbilliform rashes. We describe an immunocompromised patient who developed a vesiculobullous eruption. A simple Tzanck preparation from the base of a blister revealed multinucleate giant cells suggestive of a viral infection. Subsequent viral cultures and electron microscopic studies confirmed the diagnosis of CMV infection. Consideration of this infection should be included in the differential diagnosis of multinucleate giant cells seen on Tzanck preparations of cutaneous vesicles.

In vitro response to HBsAg of peripheral blood lymphocytes from recipients of hepatitis B vaccine

Lymphocytes isolated from recipients of hepatitis B vaccine were studied for their immune response to HBsAg in vitro. Peripheral blood mononuclear cells (PBMs) from 70 to 80% of 40 vaccinees yielded proliferative indices larger than 2 after 5 to 7 days incubation with HBsAg. This in vitro proliferative response could be augmented by incubating the cells with HBsAg and supernatants of activated T cells for 2 weeks or longer. After 7 to 10 days, in vitro stimulation with antigen, PBMs (1 X 10(6] could yield 5 to 15 HBsAg-specific antibody-secreting plaque-forming cells. The antibody to HBsAg produced in vitro was greatly increased in cultures that contained antigen-specific B cells enriched by panning with HBsAg-coated plates and a T cell growth factor-dependent, HBsAg-specific autologous T cell line. The results indicate that HBsAg-specific B and T cells are present, although at low frequencies, in the circulation of hepatitis B vaccinees.

Use of monoclonal antibodies as sensitive and specific probes for biologically active human gamma-interferon

Mouse monoclonal antibodies B1 and B3 are specific for natural and Escherichia coli-derived recombinant human gamma-interferon (IFN-gamma). The two antibodies recognize different epitopes of the IFN-gamma molecule and do not compete with each other's binding. We have used these two antibodies to construct a solid-phase, sandwich immunoradiometric assay for human IFN-gamma. Purified antibody B1 was coated on polystyrene beads (0.64 cm in diameter) and used as the solid-phase immunoadsorbent and antibody B3 was labeled with 125I and used as tracer. This assay can be completed in about 4 hr and is capable of detecting IFN-gamma levels in human serum or tissue culture fluids as low as 0.1 NIH reference unit/ml. Recombinant human IFN-gamma derived from E. coli was detectable at a concentration of 0.02 ng/ml. The assay appears to be specific for the biologically active forms of IFN-gamma, since after exposure to pH 2, 37 degrees C, or 56 degrees C, biological activity and reactivity in the immunoradiometric assay decreased in parallel. The immunoradiometric assay can be employed for the analysis of the structural characteristics of the human IFN-gamma molecule.

Antibodies to hepatitis B surface antigen potentiate the response of human T lymphocyte clones to the same antigen

Human t-helper lymphocyte clones specific for hepatitis B virus surface antigen (HBsAg) proliferate on stimulation with HBsAg in vitro. Antibodies specific for HBsAg, but no other antibodies, augment this proliferative response. In the presence of antibodies to HBsAg, the maximum response could be achieved at HBsAg concentrations that were 1 percent of those required in the absence of the antibodies. These findings suggest that antigen-specific antibodies exert regulatory controls on T cells that recognize the same antigens.

A cDNA clone encoding a product of activated human T lymphocytes

A cDNA cloning approach was used to study the regulation of gene expression in human T lymphocytes upon mitogen stimulation. Poly(A)+ mRNA was prepared from phytohemagglutinin A (PHA) and 12-O-tetradecanoyl phorbol 13-acetate (TPA) activated human T cells and a cDNA clone library was constructed. After screening by colony hybridization with [32P]cDNA probes made from resting and activated T cell mRNA, several clones whose mRNA increased at least 10 to 20-fold upon stimulation were isolated. Northern blot analysis of the mRNA from various cell types using these cDNA clones as probes revealed that one of the cDNA clones, pNC5A, encoded a gene expressed only in PHA and TPA-stimulated human T lymphocytes and in a human neoplastic T cell line HUT102-SH9. Less than 20 copies of this mRNA species per cell was detected in resting human T lymphocytes, B lymphocytes and monocytes and in two other T cell lymphoma lines (CEM and MOLT4), two B lymphoblastoid cell lines (WIL2-729-HF2 and HFB-1), a myeloid cell line (HL60) and a human embryonic lung fibroblast cell line (MRC-5). Hybrid selection translation and sodium dodecyl sulfate/polyacrylamide gel electrophoretic analysis of the translated product indicated that a polypeptide of 30,000 to 32,000 Mr is encoded by this particular cDNA clone. Thus, this cDNA clone may define a novel gene that is expressed only in activated human T cells.

Hepatitis B virus-reactive human T lymphocyte clones: antigen specificity and helper function for antibody synthesis

To study immunity to hepatitis B surface antigen (HBsAg) at the cellular level, lymphocytes were obtained from the peripheral blood of hepatitis B vaccine recipients and were examined for various immune responses to HBsAg in vitro. The peripheral blood mononuclear cells (PBM) from most of the vaccinees did not proliferate to a great extent to HBsAg in vitro. However, HBsAg-reactive lymphocyte lines and clones were obtained from some of these individuals if the PBM were stimulated in vitro with HBsAg and were maintained in the presence of T cell growth supplement. Most of the HBsAg-reactive T cell clones obtained were found to be antigen-specific and some of them provided help in the production of anti-HBsAg antibodies by a cell population enriched for HBsAg-binding cells. These results indicate that HBsAg-specific T and B cells exist in the circulation of hepatitis B vaccine recipients, although they are at limiting concentrations for the in vitro cell proliferation and antibody production assays.

Hepatitis B virus-reactive human T lymphocyte clones: antigen specificity and helper function for antibody synthesis

To study immunity to hepatitis B surface antigen (HBsAg) at the cellular level, lymphocytes were obtained from the peripheral blood of hepatitis B vaccine recipients and were examined for various immune responses to HBsAg in vitro. The peripheral blood mononuclear cells (PBM) from most of the vaccinees did not proliferate to a great extent to HBsAg in vitro. However, HBsAg-reactive lymphocyte lines and clones were obtained from some of these individuals if the PBM were stimulated in vitro with HBsAg and were maintained in the presence of T cell growth supplement. Most of the HBsAg-reactive T cell clones obtained were found to be antigen-specific and some of them provided help in the production of anti-HBsAg antibodies by a cell population enriched for HBsAg-binding cells. These results indicate that HBsAg-specific T and B cells exist in the circulation of hepatitis B vaccine recipients, although they are at limiting concentrations for the in vitro cell proliferation and antibody production assays.

Binding of cells to matrixes of distinct antibodies coated on solid surface

The present studies investigate the potential of simultaneous multiple determinations of specific cell surface antigens in one reaction incubation by employing orderly arranged antibody spots on a solid surface. Antibodies of distinct specificities were coated on very small areas in close proximity forming matrix-like arrays on glass cover slips. These antibody spots were found to be capable of serving as minute specific immunoadsorbents for cells bearing on their surface the antigens with which the antibodies reacted. Antibody spots of 1.0, 0.5 and 0.25 mm diameter could adsorb maximally about 17,000, 4500, and 1100 mononuclear cells. An area of 1 cm2 could be coated with 25, 100, or 400 of these spots, respectively. In matrixes that contained anti-Lyt 2.1 and anti-Lyt 2.2 antibody spots, AKR (Lyt 2.1+) thymocytes adhered only to anti-Lyt 2.1 spots, BALB/c (Lyt 2.2+) thymocytes only to anti-Lyt 2.2 spots, and thymocytes of (AKR X BALB/c) F1 to both spots. The potential of this method for determining allotypes of HLA antigens and for determining in a mixed cell population the proportions of subsets bearing specific differentiation antigens is discussed.

Quantitative of anti-NP (4-hydroxy-3-nitrophenyl)-acetyl idiotype expression on spleen and thymus cells

Direct binding of 125I-labeled rabbit anti-NPb idiotype antibodies (RaId) was used to quantitate the expression by immune spleen and thymus cells of NPbId, the characteristic Id of the lambda 1-containing antibodies made by C57BL/6 (B6) mice to the (4-hydroxy-3-nitrophenyl)acetyl (NP) group. Direct binding of RaId by B and T cell preparations reached a maximum of 12 ng RaId per 10(8) cells at 7 days after immunization. Spleen T cell preparations maintained similar levels of binding after positive selection for Thy-1.2+ cells and overnight culture. RaId binding was also demonstrated for immune B6 thymus cells and for spleen and thymus cells of immune SJL mice, which have the appropriate heavy chain allotype for NPbId expression but have only barely detectable serum Id. However, the NPbId of T and B cell preparations were indistinguishable by (a) the susceptibility of RaId binding by the cells to inhibition by hapten or by antibodies to the variable regions of lambda light chains (anti-V lambda) and by (b) the ability of anti-V lambda and of monoclonal antibodies to the constant region of lambda 1 chains (anti-C lambda 1) to immunoprecipitate antigen (NP10-bovine serum albumin)-binding proteins from detergent extracts of isotopically labeled cells. The results strongly imply that virtually all of the NPbId of T cell preparations is due to conventional NPbId antibody that is tightly bound to T cells. The results do not, however, exclude the possibility that the T cell preparations contain a trace amount (less than or equal to 1 ng/10(8) cells) of unusual NPbId-like molecules that lack lambda chains.