Characterization of human interferon species using gel extraction and monoclonal antibodies: implications on clinical use of interferon preparations

Human interferons from various sources have been characterized using sodium dodecyl sulfate polyacrylamide gel electrophoresis followed by electrotransfer onto nitrocellulose and reaction with specific polyclonal and monoclonal antibodies. When gel slices were extracted, alpha-interferon subspecies possessed antiviral activity predominantly in the 18.6-19.7K region bands, the beta-interferon in the 22.1K band, and gamma-interferon in the 16.5-18.0K bands. Three of the monoclonal antibodies (Ab 138, Ab 126, Ab 098) reacted with a characteristic triplet of biologically active bands (18.6K, 19.1K, 19.7K) obtained using the Namalwa cell interferons, while two (Ab 194 and Ab 232) reacted only with the 18.6K band and Ab 523 reacted with the 19.7K band. With the human leukocyte interferons, Ab 098, Ab 194, and Ab 232 reacted with the active 18.6K band. The Ab 138, Ab 126, and Ab 523 reacted specifically with certain lower molecular weight active bands (13K region). A comparison of the antiviral activity and reactivity towards monoclonal and polyclonal antibodies presents a differentiation of the subspecies of interferons in the wide array of closely related proteins in interferon preparations packaged for clinical use.

A sensitive radioimmunoassay for detection of antibodies to recombinant human interferon-alpha A

A radioimmunoassay (RIA) for the detection of antibodies to recombinant human leukocyte interferon A (rHuIFN-alpha A) in human serum has been developed and validated against the standard antiviral neutralization bioassay (ANB). The assay measures the binding of 125I-labeled rHuIFN-alpha A to immunoglobulins in serum. Aliquots of patients' sera are incubated with 125I-rHuIFN-alpha A and the complexes formed between antibodies in the sera and the 125I-rHuIFN-alpha A are precipitated with goat anti-human IgG serum. The radioactivity in the immune precipitate is a measure of the quantity of antibody (if present) in the serum. The sensitivity of this RIA is 5 ng of IgG/ml of serum.

Antigenic regions of bovine somatotropin as defined by monoclonal antibodies

Three distinct antigenic regions of bovine somatotropin (bST) were identified on the basis of the ability of a set of monoclonal antibodies to bind to proteolytic fragments and deletion variants of recombinant bST (rbST) in Western blot analyses. One of the regions is further subdivided into two epitopes on the basis of the cross-reaction of somatotropins from several species with the same set of antibodies in solid-phase RIA. The RIA and Western blot results suggest that amino acids 134-150, 181-190 and the amino terminus may be involved in the binding specificity of antibodies to the bovine somatotropin molecule. The total of four antigenic regions on the bST molecule parallels results described for human somatotropin. Labeled antibody competition tests were used to show that the epitope involving amino acids 134-150 is spatially separated from the other three epitopes.

Two monoclonal antibodies distinguish between human recombinant interferon-alpha 5s produced by Escherichia coli and by mouse cells

Two monoclonal antibodies against human IFN-alpha--one against natural leukocyte IFN-alpha and the other against recombinant human IFN-alpha 2 produced in E. coli--were prepared, and designated as HT-1, and 104-5-f, respectively. These monoclonal antibodies were used to examine the antigenicities of recombinant human IFN-alpha 5s produced by E. coli and by mouse cells. The HT-1 antibody could bind and neutralize recombinant human IFN-alpha 5 synthesized in mouse cells, but not recombinant human IFN-alpha 5 synthesized in E. coli. On the other hand, the 104-5-f antibody could bind and neutralize recombinant human IFN-alpha 5 synthesized in E. coli but not recombinant human IFN-alpha 5 synthesized in mouse cells. Then these monoclonal antibodies or sheep polyclonal antibody against human IFN-alpha were used to immunoprecipitate the radioactively labeled recombinant human IFN-alpha 5 synthesized either in E. coli or mouse cells, and analysed on polyacrylamide gel electrophoresis in the presence of NaDodSO4. The labeled recombinant human IFN-alpha 5 produced by mouse cells could be immunoprecipitated with the HT-1 monoclonal antibody or sheep anti-(human IFN-alpha) polyclonal antibody but not with the 104-5-f monoclonal antibody and showed a band of Mr. 17,500 on polyacrylamide gel electrophoresis in the presence of NaDodSO4. On the other hand, the labeled recombinant human IFN-alpha 5 produced by E. coli could be immunoprecipitated with the 104-5-f monoclonal antibody but not with the HT-1 monoclonal antibody and showed a band of similar Mr. on polyacrylamide gel electrophoresis.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological properties of a recombinant human immunoglobulin epsilon-chain fragment

A recombinant human immunoglobulin epsilon-chain gene expression product (rFc epsilon) was compared with a human E myeloma protein in the affinity for epsilon-chain Fc fragment receptors (Fc epsilon R) on cultured human basophils. The association-dissociation kinetics of the rFc epsilon-Fc epsilon R interaction are indistinguishable from that of E myeloma protein, indicating that rFc epsilon and IgE have identical affinity for the receptors. The recombinant gene product sensitizes cultured basophils for anti-IgE-induced histamine release. A dose-response curve of histamine release indicates that the gene product is equally efficient in transducing the signal for degranulation as the natural IgE. Both the rFc epsilon and IgE lost the affinity for Fc epsilon R by heating at 56 degrees C. Upon renaturation by passage through a solution of 6 M guanidine hydrochloride, rFc epsilon recovered both the affinity for Fc epsilon R and the original CD spectra. On the other hand, renaturation of heat-denatured IgE largely restored optical activity above 250 nm but restored neither the affinity for Fc epsilon R nor the CD spectrum below 220 nm. The results suggest that either the amino acid sequence or the carbohydrate present in the myeloma protein, but not the rFc epsilon, may interfere with refolding of the receptor-binding structures.

Dissection of suppressor cell generation in vitro

Suppressor cells (SC) that nonspecifically inhibited lymphoproliferative (LP) responses were found after culturing peripheral blood mononuclear cells: with suppressor T-cell clones, in mixed lymphocyte cultures (MLC), and with recombinant interleukin 2 (IL-2), but were not found after culture in medium alone. A monoclonal anti-IL-2 receptor (R) antibody (MoAb), TU69, which blocked LP responses of IL 2-dependent T-cell lines, also blocked SC induction by T-cell clones, but completely failed to inhibit SC generation in MLC or with IL-2. This suggests that the IL-2R epitope defined by TU69 was not involved in SC induction in the latter systems. MoAb against HLA-DQ (TU22), -DR (TU34, SG157), -DP (B7/21), or DR and DP (TU43, 58), all of which were able to block stimulation of appropriately specific clones, did not block SC induction in any of the three systems studied. In contrast, the broadly reactive moAb TU39, which binds at least DR and DP but also has additional reactivity for determinants tentatively designated "DY," blocked SC induction by T-cell clones and in MLC. Finally, an anti-HLA class I MoAb, W6/32.HL, greatly decreased SC generation in MLC, but not with rIL-2 or T-cell clones. Thus, the induction of nonspecific SC was dissected into three pathways involving: class I and TU39-defined but not DR, DQ, or DP determinants (in MLC) which was independent of the IL-2R epitope bound by TU69; only TU39-defined determinants (with T-cell clones), which were IL 2R dependent; and, neither class I, class II nor TU39-defined determinants (induction by rIL-2), which was also TU69+ IL-2R independent.

A monoclonal antibody with broad reactivity to human interferon-alpha subtypes useful for purification of leukocyte-derived interferon

A monoclonal antibody to human interferon-alpha, termed HT-1 antibody, with a broad reactivity to various subtypes of interferon-alpha was prepared. It bound and neutralized all of the four subtypes of E. coli-derived human recombinant interferon-alpha (alpha 1, alpha 2, alpha 4, and alpha 6) tested; it also neutralized human natural leukocyte interferon but only partially. Human interferon-beta and -gamma were not bound. The antibody conjugated to Sepharose beads retained over 90% of human leukocyte interferon induced by Sendai virus. The bound interferon was recovered by acid elution in good yields and in almost pure form (specific activity was about 2 X 10(8) international units/mg protein). The purified interferon showed, in SDS-polyacrylamide gel electrophoresis, an activity profile with major peaks in a mol. wt. range of 17,000-22,000, which completely agreed with the profile shown by polyclonal antibody-purified interferon. Such purified leukocyte interferon-alpha preparations containing most of the naturally occurring subtypes can be useful for clinical and other purposes.

Human oncogene-transfected tumor cells display differential susceptibility to lysis by lymphokine-activated killer cells (LAK) and natural killer cells

NIH 3T3 tertiary transfectants containing the N-ras or c-Ha-ras oncogenes derived from human tumors were tested for susceptibility to lymphokine-activated killer (LAK) cell and natural killer (NK) cell lysis. N-ras tertiary transfectants contained a human acute lymphocytic leukemia-derived N-ras oncogene. C-Ha-ras transfectants contained either the position 61-activated form of the oncogene (45.342, 45.322, and 45.3B2) or the position 12-activated form (144-162). In 4 hr 51Cr release assays, seven of seven in vivo grown human oncogene transfected NIH 3T3 fibroblasts were lysed by murine LAK effectors, whereas six of seven were lysed by human LAK effectors. There was no difference in susceptibility to lysis between cells transfected with the N-ras oncogene, the position 61 activated c-Ha-ras oncogene, or the position 12 activated c-Ha-ras oncogene. Cultured NIH 3T3 fibroblasts, as well as in vitro and in vivo grown NIH 3T3 tertiary transfectants were resistant to lysis by murine NK effectors and were relatively resistant (4/6 were not lysed) to lysis by human NK effectors. We conclude that human oncogene-transfected tumors are susceptible to lysis by both murine and human LAK cells while being relatively resistant to lysis by murine and human NK cells. Different oncogenes or the same oncogene activated by different point mutations do not specifically determine susceptibility to lysis by LAK or NK. Also the presence of an activated oncogene does not appear to be sufficient for inducing susceptibility to these cytotoxic lymphocyte populations.

Differential expression of lymphokine-activated killer cells and natural killer cells in adoptive transfer experiments utilizing fractionated bone marrow

Precursors of murine natural killer (NK) cells and lymphokine-activated killer (LAK) cells can be distinguished by utilizing an adoptive transfer system in which donor bone marrow is fractionated on Percoll discontinuous gradients. Although precursors of LAK cells are present in all fractions, one fraction (greater than 65% Percoll) contains LAK precursors and is depleted of NK precursors. Both in vitro NK activity and in vivo hybrid resistance is abrogated in recipients of bone marrow from the greater than 65% Percoll fraction, whereas LAK activity can be readily demonstrated.

Antigen-specific Lyt-2+ cytolytic T lymphocytes from mice infected with the intracellular bacterium Listeria monocytogenes

In vitro expanded T cell lines were used to determine whether antigen-specific cytolytic T lymphocytes are generated after infection with the intracellular bacterium, Listeria monocytogenes. Spleen cells from infected mice were cultured in the presence of syngeneic accessory cells, listerial antigen, and interleukin 2 containing supernatants. Cell lines were greater than 98% Thy-1+, L3T4-, Lyt-2+. Bone-marrow macrophages were used as target cells in two in vitro cytolytic assay systems. The Lyt-2+ T cells killed bone marrow macrophages only when infected with L. monocytogenes as assessed in a 4-hr 51Cr release assay and in an 18-hr neutral red uptake assay. Cytolysis was blocked by anti-LFA-1 and anti-Lyt-2 monoclonal antibodies. These cytolytic T cells produced interferon-gamma after co-stimulation with antigen, accessory cells, and recombinant interleukin 2. Bone marrow macrophages infected with Mycobacterium bovis were not killed by T cells from L. monocytogenes-infected mice but by T cell lines from M. bovis-infected mice, indicating that cytolysis was antigen specific. L. monocytogenes-infected target cells of different haplotype were lysed by the Lyt-2+ T cells. By using a low cell density split culture system, antigen-specific, H-2-restricted cytolytic T cells could be identified. These findings demonstrate that during infection with intracellular bacteria, Lyt-2+ T cells with cytolytic activity are generated that may be involved in antibacterial protection.

Ecology of orthopoxviruses and use of recombinant vaccinia vaccines

Little is known of the ways in which orthopoxviruses are maintained in nature, and the role of wild-life reservoirs requires further investigation. This lack of information is important in view of proposals to use as vaccines recombinant vaccinia viruses which carry genes for other immunising antigens. The possibility that such strains may become established in nature, as vaccinia may have in Indian buffaloes, and/or undergo genetic hybridisation with existing orthopoxviruses should be considered.

Murine leukemia virus pol gene products: analysis with antisera generated against reverse transcriptase and endonuclease fusion proteins expressed in Escherichia coli

The organization of the murine leukemia virus (MuLV) pol gene was investigated by expressing molecular clones containing AKR MuLV reverse transcriptase or endonuclease or both gene segments in Escherichia coli and generating specific antisera against the expressed bacterial proteins. Reaction of these antisera with detergent-disrupted virus precipitated an 80-kilodalton (kDa) protein, the MuLV reverse transcriptase, and a 46-kDa protein which we believe is the viral endonuclease. A third (50-kDa) protein, related to reverse transcriptase, was also precipitated. Bacterial extracts of clones expressing reverse transcriptase and endonuclease sequences competed with the viral 80- and 46-kDa proteins, respectively. These results demonstrate that the antisera are specific for viral reverse transcriptase and endonuclease. Immunoprecipitation of AKR MuLV with antisera prepared against a bacterial protein containing only endonuclease sequences led to the observation that reverse transcriptase and endonuclease can be associated as a complex involving a disulfide bond(s).

Monoclonal antibody recognizing pre-S(2) epitope of hepatitis B virus: characterization of pre-S(2) epitope and anti-pre-S(2) antibody

A hybrid cell line producing monoclonal antibodies recognizing an epitope encoded by the pre-(S)2 region of hepatitis B virus (HBV) genome was obtained by fusion of mouse myeloma cells with lymphocytes from mice immunized with HBV. The monoclonal antibody Mo-F124 secreted from the hybrid line reacted with the pre-S(2) epitope expressed on the surface of both viral and recombinant HBsAg particles--pre-S(2) and S gene product--localised on 34 kD glycoprotein of the viral envelope. The pre-S(2) epitope was sensitive to digestion with V8 protease from Staphylococcus aureus. The enzyme abolished reactivity with Mo-F124 and polymerized human serum albumin (pHSA) binding activity of recombinant particles. Mo-F124 antibody was used to develop highly sensitive radioimmunoassays for determination of pre-S(2) epitope and anti-pre-S(2) antibody in sera of hepatitis B patients. Detection of a pre-S(2) epitope by the monoclonal antibody-based assay in the early phase of acute HBV infection correlated well with the presence of markers of active viral replication (HBeAg, HBV DNA). The appearance of anti-pre-S(2) antibody, usually in the third month after onset of symptoms, was followed by elimination of circulating HBsAg and seroconversion to anti-HBs in all tested cases of uncomplicated acute hepatitis followed by recovery. Anti-pre-S(2) response was not observed in patients with chronic hepatitis B or acute HBV infection progressing to chronic disease. The observed correlation of anti-pre-S(2) response with recovery suggests that the pre-S(2) epitope may represent one of the epitopes inducing antibodies that neutralize the hepatitis B virus.

Direct and cell-mediated effects of interferon-alpha and -gamma on cells chronically infected with HTLV-III

The replication of the human T lymphotropic retrovirus HTLV-III in persistently infected cells is relatively insensitive to the direct antiviral action of human interferon-alpha or -gamma (IFN-alpha or -gamma), showing only a two- to threefold reduction of HTLV-III, even though the host cells are very sensitive to IFN, as shown by vesicular stomatitis virus (VSV)-yield reduction assay (4-5 log reduction of VSV). However, IFN anticellular activity is strongly enhanced in the presence of normal peripheral blood mononuclear cells, suggesting a cell-mediated effect of IFNs.

Characteristics of murine non-specific killer cells induced in vivo by recombinant human interleukin-2

We have examined the induction of murine non-specific killer cells in vivo and in vitro by purified recombinant human interleukin-2 (rIL-2), and compared their characteristics with respect to killing ability, cell surface phenotypes, and antibody-dependent cell-mediated cytotoxicity (ADCC). C57BL/6 spleen cells cultured with rIL-2 were remarkably cytotoxic against a variety of tumour cells in a 4-hr 51Cr-release assay. Treatment with various antibodies (anti-Thy 1, anti-Lyt 1, anti-Lyt 2, and anti-asialo GM1) plus complement (C) showed that anti-Thy 1 or anti-asialo GM1 antibody plus C removed a majority of killer activity (80% and 66%, respectively). In addition, an increase in ADCC was detected in the spleen cells cultured with rIL-2. These ADCC effector cells were indistinguishable from non-specific killer cells by the cell surface phenotypes. A single administration of rIL-2 in vivo induced only transient and marginal enhancement of non-specific killer activity of spleen cells in C57BL/6 mice. On the other hand, when 10 micrograms of rIL-2 were administered daily by bolus to C57BL/6 mice, the activity increased gradually for about 10 days and reached a plateau. This enhanced non-specific killer activity rapidly decreased and returned to normal by 72 hr after the administration was stopped. The non-specific killer cells induced in vivo in this manner were not only greatly cytotoxic against natural killer (NK)-sensitive tumour cells but were also significantly cytotoxic against NK-resistant tumour cells. Most of the killer activity (more than 90%) was specifically removed by treatment with anti-Thy 1 or anti-asialo GM1 antibody plus C. An increase in ADCC was detected concurrently with an increase in non-specific killer activity in vivo, and both effector cells were indistinguishable by their cell surface phenotypes. These results indicate that a majority of non-specific killer cells induced both in vivo and in vitro by rIL-2 have some common features. Our results also suggest that these cells belong to the same lineage as NK cells, although they are thought to be at different stages from resident NK cells.

Isolation of a Treponema pallidum gene encoding immunodominant outer envelope protein P6, which reacts with sera from patients at different stages of syphilis

A phage directing the synthesis of an abundant 45-kD Treponema pallidum surface protein was isolated from an EMBL-4 bacteriophage lambda library of T. pallidum DNA. The recombinant phage was identified using an mAb that was directed toward an immunodominant, outer envelope T. pallidum protein designated P6. The recombinant P6 protein possessed the same mol mass as the native treponemal antigen detected from total T. pallidum protein preparations, confirming the cloning of the structural gene for this molecule. Furthermore, E. coli was transformed by a 4.5-kb Eco RI lambda insert fragment subcloned into the plasmid vector pUC19. These transformed cells expressed and translocated the 45-kD protein to their outer membranes. Finally, all sera from patients with different stages of syphilis (primary, secondary, and latent) contained antibody reactive to this protein.

Assembly of influenza hemagglutinin trimers and its role in intracellular transport

The hemagglutinin (HA) of influenza virus is a homotrimeric integral membrane glycoprotein. It is cotranslationally inserted into the endoplasmic reticulum as a precursor called HA0 and transported to the cell surface via the Golgi complex. We have, in this study, investigated the kinetics and cellular location of the assembly reaction that results in HA0 trimerization. Three independent criteria were used for determining the formation of quaternary structure: the appearance of an epitope recognized by trimer-specific monoclonal antibodies; the acquisition of trypsin resistance, a characteristic of trimers; and the formation of stable complexes which cosedimented with the mature HA0 trimer (9S20,w) in sucrose gradients containing Triton X-100. The results showed that oligomer formation is a posttranslational event, occurring with a half time of approximately 7.5 min after completion of synthesis. Assembly occurs in the endoplasmic reticulum, followed almost immediately by transport to the Golgi complex. A stabilization event in trimer structure occurs when HA0 leaves the Golgi complex or reaches the plasma membrane. Approximately 10% of the newly synthesized HA0 formed aberrant trimers which were not transported from the endoplasmic reticulum to the Golgi complex or the plasma membrane. Taken together the results suggested that formation of correctly folded quaternary structure constitutes a key event regulating the transport of the protein out of the endoplasmic reticulum. Further changes in subunit interactions occur as the trimers move along the secretory pathway.

Human recombinant interleukin-2 augments in vitro blastogenesis of bovine and porcine lymphocytes

The recent cloning of the human gene encoding interleukin 2 (IL-2) has provided the means for economical production of large quantities of the pure lymphokine for clinical studies. Human recombinant interleukin 2 (HrIL-2) has been reported to have in vitro and in vivo immunomodulating effects in the murine system, suggesting the cloned gene product has cross-species activity. Bovine and porcine peripheral blood lymphocytes were tested for responsiveness to HrIL-2 in a lymphocyte blastogenesis assay. Not only was the HrIL-2 highly stimulatory but it also reconstituted lymphocyte responsiveness to maximal values following incubation with suboptimal concentrations of mitogen plus exogenous lymphokine. These studies suggest that HrIL-2 has the potential of serving as an in vivo modulator of immunoresponsiveness in domestic species. The contribution to food animal medicine will be considerable if administration of the lymphokine results in augmentation of antigen-specific immune responses when applied as an adjuvant, non-specific booster of pre-existing immunity, or for therapy of immunosuppression.

Intron A (interferon alfa-2b): clinical overview and future directions

The clinical development of the recombinant alpha interferons represents a prototype for the clinical development of biological compounds. Their testing raises fundamental questions concerning phase I objectives and strategies for biologicals, eg, study design in an immune model v a cytotoxic model. However, with over 5,000 patients treated with these compounds, some general principles have emerged. There is a suggestion of dose-response relationships, and a clearer picture of schedule dependence. The extent of tumor burden and identification of sensitive subtypes of patients also appear to be critical factors in evaluating the true potential activity of biological compounds. The toxicity profile of the alpha interferons is unusual. Fever and flu-like symptoms occur almost universally in all doses and schedules, and are usually dose-limiting. Somnolence and other CNS effects occur in a small percentage of patients. Hematologic toxicity occurs but is minimal at lower doses and is noncumulative and rapidly reversible at all doses. Gastrointestinal toxicity is mild. No other unusual or unexpected toxicities have been reported, and early reports of cardiovascular toxicity have not been confirmed in large trials. The use of these pioneer recombinant DNA products raised concerns about the potential production of antibodies and serum-neutralizing factors. Reports with small patient numbers confirmed the occasional development of serum-neutralizing activity to some alpha interferons, which may coincide with a loss of detectable serum interferon and loss of clinical activity. A large study with interferon alfa-2b (Intron A) has reported a low overall incidence of neutralizing activity (2.5%) and no association with loss of clinical activity. The significance of the neutralizing activity and the reasons for an apparently higher incidence of this phenomenon with other alpha interferon preparations remain to be determined. The full role of alpha interferon by itself or in combination with other available therapies will be resolved in coming years. Efficacy data available to date and phase I combination studies are reviewed.

Functional and molecular characterization of a monoclonal antibody against human interleukin 2

Human recombinant interleukin 2 (r-IL2) was used as an immunizing antigen to yield a murine monoclonal antibody (mAb) termed BO-7. Although the antibody binds to r-IL2 more avidly, it also reacted strongly with IL2 from natural sources in an enzyme-linked immunosorbent assay (ELISA), allowing the detection of the purified lymphokine at sensitivity levels closely approaching those found with the IL2 biological assay. Binding to the antigen is specific, as deduced from the close correlation of ELISA immunoreactivity with IL2 biological activity and from immunoblot analysis of electrophoretically separated IL2 from various sources. Binding studies with synthetic IL2-derived peptides revealed the location of the epitope, which is recognized by mAb BO-7: A peptide representing amino acid residues 59-72 (peptide 84) is strongly reactive with the antibody, while an overlapping peptide (residues 48-69) is not. Peptide 84, moreover, can be applied for immunopurification of mAb BO-7 and competes for binding to the antibody with the intact IL2 molecule. In turn, another monoclonal anti-IL2 antibody (35H10), showing the same reactivity pattern with peptides, competes with mAb BO-7 for binding to IL2. The application of mAb BO-7 as a specific reagent for the quantitation of IL2 in a sandwich-type ELISA is demonstrated.

Analysis of retroviral pol gene products with antisera raised against fusion proteins produced in Escherichia coli

Portions of the pol gene of Moloney murine leukemia virus (MuLV) were expressed as fusion proteins in Escherichia coli, and the purified proteins were used to elicit antibodies in Escherichia coli, and the purified proteins were used to elicit antibodies in rabbits. The sera were used to examine the mature pol gene products contained in virion particles and identified the reverse transcriptase and a second protein, P46pol, encoded by the 3' portion of the gene. The P46 protein was not phosphorylated and was present at the same molar abundance as the reverse transcriptase. The sera were also used to detect the Pr200gag-pol intracellular precursor protein and to analyze its processing to the mature forms. The proteins formed by several Moloney MuLV mutants were analyzed. Further tests revealed cross-reactivity with Friend MuLV and feline leukemia virus proteins, but not with avian retrovirus proteins.

Reactivity of E. coli-derived trans-activating protein of human T lymphotropic virus type III with sera from patients with acquired immune deficiency syndrome

Randomly sheared DNA fragments from HTLV-III proviral DNA were cloned into an E. coli open reading frame (ORF) expression vector. The inserted ORF DNA was expressed in E. coli transformants as a polypeptide fused to the lambda CI protein at the amino terminus and to beta-galactosidase at the carboxyl terminus. The reactivity of the recombinant peptides with antibodies from sera of AIDS patients was determined by the Western blot technique. The coordinates of the DNA inserts of the immunoreactive clones were then determined by DNA sequencing. A clone, ORF 628, was found to contain a short DNA segment located between the sor and env genes (nucleotide positions 5367 to 5597), a region previously thought to be noncoding. Inspection of the DNA sequences of this clone and of other HTLV-III isolates revealed the presence of a small ORF located between nucleotide position 5411 and 5625, capable of encoding a polypeptide of 72 amino acids. The biosynthesis of the polypeptide of ORF 628 initiates from an ATG codon within the HTLV-III insert. The fusion protein of ORF 628 was partially purified by affinity chromatography on CH Sepharose 4B coupled to a beta-galactosidase ligand, and tested against a panel of sera from AIDS patients by Western blot analysis. Approximately 35% of the sera from patients with AIDS or ARC contained antibodies reactive with the peptide. The DNA region spanned by ORF 628 is now thought to be the major functional element of the trans-activator gene, tat.

Neutralization of the AIDS retrovirus by antibodies to a recombinant envelope glycoprotein

Mammalian cell lines have been engineered to produce a secreted form of the AIDS retrovirus envelope glycoprotein. The recombinant protein has been isolated from growth-conditioned culture media and used to immunize animals. Antibodies directed against the recombinant molecule were found to react with the envelope glycoprotein produced in virus-infected cells. Furthermore, these antibodies were able to directly inactivate the AIDS retrovirus in a neutralization assay in vitro. The expression system reported here should provide sufficient quantities of the AIDS retrovirus envelope protein for biological and vaccination studies.

Regulation of natural killer cytotoxicity by Escherichia coli-derived human interferon gamma

The abilities of Escherichia coli-derived human interferon gamma (IFN-gamma) and E. coli-derived human interferon-alpha A (IFN-alpha A) or -alpha 2 (IFN-alpha 2) to augment natural killer (NK) cytotoxicity were compared. When low concentrations (less than 10 antiviral units/ml) of interferons were used, and equal numbers of antiviral units of E. coli-derived IFN-gamma and E. coli-derived IFN-alpha A or IFN-alpha 2 were compared for their ability to augment NK, E. coli-derived IFN-gamma was found to be more active in augmenting NK against the K562 targets, than E. coli-derived IFN-alpha A or IFN-alpha 2. Antiviral units in these experiments were determined by the standard cytopathic effect assay using vesicular stomatitis virus (VSV)-challenged human fibroblasts, trisomic for chromosome 21. However, when these interferons were compared on a weight basis (ng/ml) or on a molar basis, their ability to augment NK against the K562 targets was comparable. These differences in the relative abilities of these interferons (when their concentrations were expressed in antiviral units/ml) to augment NK, were due to an approximately 100-fold difference in their specific activities (antiviral units per mg of interferon). These were 1.8 X 10(6) units/mg for E. coli-derived IFN-gamma, 2.0 X 10(8) units/mg for E. coli-derived IFN-alpha A, and 1.8 X 10(8) units/mg for E. coli-derived IFN-alpha 2. At concentrations higher than 10 units/ml, all these interferons showed a similar ability to augment NK. Studies on the kinetics of the augmentation revealed that in vitro treatment with E. coli-derived IFN-gamma for several hours was necessary for augmentation of NK against targets from haemopoietic human tumour cell lines (K562, Daudi). In contrast, alpha interferons were able to augment NK after treatment in vitro for significantly shorter periods (30 min or less with certain donors). Augmentation of NK cytotoxicity of human peripheral blood mononuclear leucocytes by E. coli-derived IFN-gamma was not accompanied by the induction of interleukin 2 (IL-2) production, suggesting that IL-2 is not involved in the augmentation of NK by IFN-gamma. A monoclonal antibody specific for human IFN-gamma blocked augmentation of NK by E. coli-derived IFN-gamma and natural IFN-gamma, but not by E. coli-derived IFN-alpha A or staphylococcal enterotoxin A (SEA).(ABSTRACT TRUNCATED AT 400 WORDS)

Expression of the protein encoded by the 3' open reading frame of human T-cell lymphotropic virus type III in bacteria: demonstration of its immunoreactivity with human sera

The genome of human T-cell lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV), the infectious agent etiologically associated with the acquired immunodeficiency syndrome, contains, in addition to the genes for the polymerase, core, and envelope proteins, several open reading frames. To investigate whether the 3' open reading frame (3' orf) located between the envelope gene and the 3' long terminal repeat is a gene expressed in vivo in infected individuals, we inserted a fragment of 3' orf in a prokaryotic expression vector. The protein product synthesized in bacteria was purified and allowed to react with sera from individuals infected with human T-cell lymphotropic virus type III as indicated by seropositivity for other viral proteins. Two-thirds of the sera, regardless of the clinical status of the individuals, reacted with the purified protein indicating that 3' orf is a viral gene the product of which is immunogenic in vivo. A polyclonal rabbit antiserum reacting against the 3' orf gene product was obtained by serial injection of rabbits with the purified bacterial protein. The antiserum recognized a 27-kDa protein in the human T-cell lymphotropic virus type III-infected lymphocytes.

Molecular cloning of cDNA for rat liver gap junction protein

An affinity-purified antibody directed against the 27-kD protein associated with isolated rat liver gap junctions was produced. Light and electron microscopic immunocytochemistry showed that this antigen was localized specifically to the cytoplasmic surfaces of gap junctions. The antibody was used to select cDNA from a rat liver library in the expression vector lambda gt11. The largest cDNA selected contained 1,494 bp and coded for a protein with a calculated molecular mass of 32,007 daltons. Northern blot analysis indicated that brain, kidney, and stomach express an mRNA with similar size and homology to that expressed in liver, but that heart and lens express differently sized, less homologous mRNA.

Modulation of cellular immune responses in mice with disseminated histoplasmosis by recombinant interleukin-2

Depression of the cellular immune responses in mice with disseminated histoplasmosis is associated with deficient production of interleukin-2 (IL-2) by splenocytes. Therefore, we examined whether a highly purified preparation of IL-2, recombinant human IL-2 (rIL-2), could modify the cellular immune responses in infected mice and whether this lymphokine could alter the severity of histoplasmosis in animals. Exogenous rIL-2, at concentrations of up to 1,000 U/ml, failed to augment the proliferative responses to concanavalin A by unfractionated splenocytes or splenic T cells from mice infected for 1 week. In addition, rIL-2 did not modulate the plaque-forming cell response to sheep erythrocytes by splenocytes from these same mice. However, at week 3, rIL-2 in concentrations ranging from 10 to 1,000 U/ml considerably augmented the proliferative response to concanavalin A and plaque-forming cell response to sheep erythrocytes by splenocytes from infected mice. Kinetics studies demonstrated that rIL-2 exerted maximal immunoregulatory activity when added on day 0 or 1 to cultures of splenocytes. In vivo administration of rIL-2, 200 to 20,000 U/day, for 10 days to normal and 3-week-infected mice did not alter the proliferative activity of splenocytes to concanavalin A; 200,000 U of rIL-2 per day actually depressed the proliferative responses of splenocytes from normal and infected mice. In vivo, rIL-2 did not modify delayed-type hypersensitivity responses to sheep erythrocytes or to histoplasmin by normal and infected mice. Moreover, treatment with rIL-2 in vivo did not reduce the number of Histoplasma CFU in spleens of mice. Thus, despite the immunoenhancing effect of rIL-2 in vitro, this lymphokine failed to exert similar effects in vivo.

Human retroplacental sera inhibit the expression of class II major histocompatibility antigens

Since factor(s) present in human pregnancy sera may interfere with HLA-DR expression on antigen-presenting cells which could account for fetal immune tolerance, we decided to investigate HLA-DR expression on the human myeloid macrophage cell line U937 using the monoclonal antibody RF DR2 and flow cytometry. Following incubation of U937 cells with recombinant interferon gamma (rIFN gamma) and fetal calf serum, 76% of the cells were HLA-DR positive. In contrast, when U937 cells were incubated with retroplacental serum (RP) only 40% of them were positive for HLA-DR and the mean fluorescent intensity for the cell population was significantly diminished. By performing these experiments at 37 and at 4 degrees C we concluded that a factor or factors present in RP bind onto and mask class II major histocompatibility (MHC) antigen expression.

Immunogenicity of Plasmodium falciparum antigenic determinants produced by Escherichia coli recombinant clones

The immunogenicity of two parasite antigens produced by Escherichia coli as proteins fused to beta-galactosidase was investigated in three animal species: mice, rabbits and squirrel monkeys. 2L protein carries 71 amino acids of a parasite antigen and 11.1 protein carries 23 repeats of a 9-amino-acid repetitive unit. The humoral response was studied using indirect immunofluorescence and immunoprecipitation. The results indicate that immunization of mice, rabbits and squirrel monkeys using SDS-denatured 2L fusion protein induced antibodies able to bind to parasite antigen 2L in the IFA or in the immunoprecipitation assays. Immunization using the native fusion protein did not induce antibodies able to immunoprecipitate the 2L parasite antigen. The same observation was made for the animals immunized with 11.1 recombinant protein. In this case, the antibody response was also measured by ELISA using synthetic dimers of the repeat as antigen. In mice and rabbits, high titres of anti-11.1 antibodies were found by ELISA. However, when the antigen produced by the parasite itself was used to evaluate the response, low titres were found. This indicates that the animals produced high levels of antibodies to a structure which is not exposed in the parasite. In squirrel monkeys, the same observation was made, but the overall levels of the response to 11.1 antigen were considerably lower than those observed in mice or rabbits.

Localization of the v-rel protein in reticuloendotheliosis virus strain T-transformed lymphoid cells

The protein (p59rel) encoded by the transforming gene of reticuloendotheliosis virus strain T (REV-T) has been identified in REV-T-transformed avian lymphoid cells by using antisera raised against synthetic peptides whose sequences were derived from three nonoverlapping regions of v-rel (N. R. Rice, T. D. Copeland, S. Simek, S. Oroszlan, and R. V. Gilden, Virology 149:217-229, 1986). To obtain polyclonal antibodies directed against a larger number of p59rel epitopes, a 262-amino acid segment was expressed in bacteria. Antisera raised against this fusion protein (v-delta-rel) precipitated p59rel from lysates of [35S]methionine-labeled REV-T-transformed cells, thus confirming previous results obtained with the peptide antisera. We used this new antiserum to localize p59rel in REV-T-transformed cells by subcellular fractionation using differential centrifugation and by indirect immune fluorescent staining. After fractionation and immune precipitation, the majority of p59rel was found in the cytosolic fraction. Indirect immunofluorescence experiments also gave results consistent with the cytoplasmic localization of the v-rel protein in transformed lymphoid cells. In previous studies (Rice et al., Virology 149:217-229, 1986) it was shown that immune precipitates formed with one of the three p59rel peptide antisera possessed in vitro protein kinase activity. Immune precipitates formed with the fusion protein antiserum also showed kinase activity in the in vitro assay. Most of this activity was found in the soluble cytoplasmic fraction, indicating that the kinase may be p59rel or a protein closely associated with it.

Inhibitory effects of interferon-gamma on the T suppressor cell circuit in contact sensitivity

The effects of a partially purified, splenocyte-derived murine interferon (MuIFN-gamma N) and a recombinant IFN-gamma (MuIFN-gamma R) on the T suppressor pathway and on the T effector cells of delayed type hypersensitivity were investigated in a 2,4-dinitrofluorobenzene contact sensitivity model. Various T cell subpopulations, suppressor T cells of afferent and efferent types, and an auxiliary T suppressor cells as well as a T effector cell of delayed type hypersensitivity were induced and the functions assessed in transfer experiments. Confirming the results of earlier experiments obtained with IFN-alpha, beta, the MuIFN-gamma N preparation and the rec. MuIFN-gamma R: enhanced the decreased response in animals sensitized with an antigen overload to an optimal response; inhibited the afferent-acting T suppressor cell in vivo and in vitro; inhibited the Ts-eff response; blocked the auxiliary T suppressor cell response after intravenous injection to recipients of Ts-eff cells on day 0 and 1; and did not suppress the activity of the T effector cell of delayed type hypersensitivity in vivo and in vitro (the MuIFN-gamma R was not tested). We conclude that IFN-gamma preferentially inhibited the T suppressor cell circuit of contact allergy. These results are similar to our observations on the inhibitory effects of a pure interferon-alpha, beta on the regulatory T suppressor cell circuit in contact allergy. Selective suppression of different T subpopulations by IFN-gamma may be an important regulatory mechanism in delayed type hypersensitivity.

Production and immunological analysis of recombinant hepatitis B vaccine

The synthesis of the hepatitis B surface antigen (HBsAG) in cells of Saccharomyces cerevisiae and its subsequent isolation, purification and analysis is described. The final, purified HBsAg particle exhibits close structural and biochemical similarities to particles derived from the plasma of chronically infected humans. Particles of yeast and human origin have been found, by chimpanzee efficacy studies and by various in vitro analyses, to be immunologically equivalent. The antigenic expression of a determinant-specific epitopes, as measured by antibody binding to synthetic peptides, has also been shown to be equivalent.

Serological characterization and gene localization of an Escherichia coli-expressed 37-kilodalton Treponema pallidum antigen

A recombinant plasmid containing a 5.6-kilobase-pair DNA fragment of the Treponema pallidum genome was characterized by endonuclease mapping, and the encoded proteins were expressed in Escherichia coli and analyzed by use of in vitro transcription and translation. One of the proteins, identified as having a molecular weight of 37,000 (37K protein), was selected for further study. Initially, the seroreactivity of the partially purified 37K antigen was demonstrated by immunoblotting. After its purification to near homogeneity, the cloned T. pallidum protein was assessed for diagnostic significance by radioimmunoassay. Although first identified as seroreactive by screening with secondary syphilitic sera (T. E. Fehniger, A. M. Walfield, T. M. Cunningham, J. D. Radolf, J. N. Miller, and M. A. Lovett, Abstr. Annu. Meet. Am. Soc. Microbiol. 1985, B156, p. 44), the antigen was shown to be serologically reactive with antibodies in serum from all stages of syphilis but was not recognized by serum from controls by both immunoblotting and radioimmune assay. Further, a monospecific polyclonal rabbit antiserum generated to the 37K antigen recognized a polypeptide of the same molecular weight from T. pallidum but did not efficiently recognize proteins from five nonpathogenic treponemes tested. Therefore, because of reactivity with and specificity for T. pallidum antibodies, the 37K antigen may be of serodiagnostic value in the detection of syphilis.

Human T lymphocyte clones with killer or natural killer activity

We describe a reliable method for obtaining a significantly higher frequency of human cloned T lymphocytes with killer and/or NK-like activity. Human peripheral blood mononuclear cells were treated with recombinant interferon-gamma (rIFN-gamma) and recombinant interleukin-2 (rIL-2) in a culture medium containing autologous serum and were then cloned by single cell micromanipulation. The cloned T lymphocyte populations were tested simultaneously for their ability to proliferate in response to exogenous IL-2, to exhibit lectin-dependent cytolysis and to kill the tumor cell line K562. Results indicate that the cloning technique allowed each isolated T lymphocyte to undergo cell expansion. Furthermore when T cells were pretreated with rIFN-gamma and rIL-2, 88% of the T cell clones were capable of mediating cytotoxicity in the presence of PHA. Moreover one third of the clones which exhibited lectin-dependent lysis were able to kill K562 target cells.

Production and characterization of monoclonal antibodies against recombinant human tumor necrosis factor/cachectin

Tumor necrosis factor is a monokine, which causes cytolysis of many transformed cells. In this study we have found that in addition to cytotoxicity recombinant Escherichia coli-derived human tumor necrosis factor, like cachectin, inhibited the lipoprotein lipase of 3T3-L1 preadipocytes. Both effects were inhibited by monoclonal anti-tumor necrosis factor antibodies. Monoclonal antibodies against recombinant human tumor necrosis factor were produced by fusing splenocytes of immune mice with P3X63Ag8 653 myeloma cells. The monoclonal antibodies, namely BG 2-4, were of IgG2a, IgG, and IgG2a subclasses. These monoclonal antibodies neutralized the cytotoxicity of natural and recombinant human tumor necrosis factor but not that of rabbit or mouse tumor necrosis factor. They also neutralized the cachectin activity of human tumor necrosis factor in the 3T3-L1 embryonic cell assay. These results indicate that the functional structure(s) of human tumor necrosis factor responsible for the cytotoxicity and cachectin activities are likely to be closely related.

Comparison of the antigenicities of native human growth hormone (hGH) and three forms of recombinant hGHs using monoclonal antibodies

A panel of hybridomas producing antibodies specific for human growth hormone (hGH) were prepared by using a recombinant hGH [methionylsomatotropin (r-hGH)] as an immunogen. Thirteen representative monoclonal antibodies which showed different reactivity patterns were used to analyze the antigenicities of four different forms of hGHs by RIA inhibition studies. Native hGH and r-hGH showed almost the same antigenicities with these monoclonal antibodies. A Cys-substituted recombinant hGH (r-hGH-165) retained the epitopes recognized by 11 monoclonals but not those recognized by two monoclonals. All except one of the monoclonals showed little or no reactivity with a recombinant hGH fragment (r-hGH-AB). On the basis of these results, the differences in the structures and antigenicities of the recombinant hGH proteins were discussed.

Natural and recombinant interferons inhibit epithelial cell invasion by Shigella spp

The effect of natural and recombinant interferons (IFNs) on the abilities of Shigella flexneri, S. sonnei, and Salmonella typhimurium to invade different human and murine cells was examined. Pretreatment of cell monolayers with natural and recombinant IFNs reduced the number of Shigella-infected cells in a dose-dependent manner. Establishment of an anti-invasive cellular state was time dependent, requiring 10 h for 50% inhibition of bacterial invasion. The inhibitory effect of IFN was species specific, with human or murine IFN effective against homologous but not heterologous cells. Gamma IFN was slightly more potent than alpha IFN at inhibiting bacterial invasion. Inhibition of Shigella invasion was dependent on the challenge dose of bacteria. Little inhibition of invasion was seen when cells were pretreated with low concentrations of IFN and challenged with high multiplicities of infection of Shigella sp. In contrast to Shigella invasion, the maximum inhibitory effect of IFN on Salmonella invasion of cells was observed at low levels (5 to 50 U) of IFN. These results suggest that Shigella and Salmonella invasions occur at unique sites on eucaryotic cells or by different penetration mechanisms. More importantly, these data suggest that IFN may play a significant role in host defense against Shigella and Salmonella infections.

Synthesis of fusion proteins containing antigenic determinants of foot-and-mouth disease virus

Part of the genome of foot-and-mouth disease virus (FMDV) type 01,BFS, including the sequence encoding the capsid polypeptide VP1, was cloned in Escherichia coli following a new cloning strategy. The clone containing the VP1 sequence was used for the construction of two expression plasmids encoding VP1 fusion proteins. Subsequently, substantial amounts of the two VP1-beta-galactosidase fusion proteins, containing either one (amino acid region 140-160) or two (amino acid regions 140-160 and 200-213) antigenic determinants of the virus, were synthesized by E. coli bacteria. The protein containing the amino acid region 140-160 of VP1 fused to beta-galactosidase efficiently induced antibodies in rabbits specifically reacting with FMDV type 01,BFS. The same protein was also capable of eliciting neutralizing antibodies. The fusion protein containing both antigenic determinants did not efficiently induce antibodies reacting with FMDV.

Recognition of cloned vesicular stomatitis virus internal and external gene products by cytotoxic T lymphocytes

It has generally been assumed that most if not all CTL specific for vesicular stomatitis virus (VSV)-infected cells recognize the viral glycoprotein (G), an integral membrane protein abundantly expressed on infected cell surfaces. Using recombinant vaccinia viruses containing copies of cloned VSV genes to examine CTL recognition of VSV, we have confirmed that G is recognized by VSV-specific CTL. More interestingly, however, we have also found that nucleocapsid protein (N), an internal virion protein, can be detected on infected cell surfaces using mAb, and serves as a major target antigen for VSV-specific CTL. In contrast to the highly serotype-specific recognition of G, N is recognized by a major population of CTL able to lyse cells infected with either the Indiana or New Jersey VSV serotypes. Using target cells expressing a cloned MHC class I gene, we could directly show that CTL recognition of N occurs in the context of the MHC Ld molecule.

Human and monoclonal antibodies to hepatitis B core antigen recognise a single immunodominant epitope

Monoclonal antibodies were raised against hepatitis B core antigen (HBcAg) synthesized in Escherichia coli. They identified a single immunodominant determinant on both liver-derived and E. coli-derived HBcAg. Cross-inhibition studies demonstrated that HBsAg-containing human sera which contained antibodies to HBcAg (anti-HBc) together with either hepatitis B e antigen (HBeAg) or its antibody (anti-HBe) essentially only recognised the same single determinant as the murine antibodies. The identification of a single dominant HBcAg determinant may be important if future hepatitis B virus vaccines contain HBcAg.

Development and characterization of antiserum to murine granulocyte-macrophage colony-stimulating factor

The expression in yeast of a cDNA clone encoding murine granulocyte-macrophage colony-stimulating factor (GM-CSF) has made possible the purification of large quantities of this recombinant protein. Rabbits immunized with pure recombinant GM-CSF generated antibodies that were shown to be specific for both recombinant GM-CSF and GM-CSF isolated from natural sources. Other lymphokines, including IL 1 beta, IL 2, IL 3, and recombinant human GM-CSF did not react with the antiserum. The antiserum, together with recombinant GM-CSF that had been radiolabeled with 125I to high specific activity, formed the foundation for a rapid, sensitive, and quantitative radioimmunoassay specific for murine GM-CSF. Furthermore, the antiserum was found to inhibit the biologic activities of GM-CSF as measured in both a bone marrow proliferation assay and a colony assay, and thus should prove to be a useful reagent for dissecting the complex growth factor activities involved in murine hematopoiesis.

Treatment of Turner's syndrome with methionyl human growth hormone for six months

Twenty patients with Turner's syndrome were treated with methionyl human growth hormone (met-hGH) produced by recombinant DNA technology. Plasma non-esterified fatty acid (NEFA) (mean +/- SEM) increased significantly from 0.52 +/- 0.06 to 1.30 +/- 0.09 mEq/l at 4 h after the first administration of 4 IU of met-hGH (P less than 0.001). Basal plasma somatomedin C (SM) levels were within the normal range; however, they increased significantly at 24 h after the first three daily injections of 4 IU of met-hGH (basal, 0.92 +/- 0.14; 24 h, 1.39 +/- 0.16; 48 h, 1.68 +/- 0.19; 72 h, 1.91 +/- 0.22 U/ml; P less than 0.001). For long-term treatment, the patients were given 16 IU of met-hGH per week for 6 months. The height increase during treatment was greater in 16 patients, but smaller in 4 than before treatment. The heights increased between 1.4 and 3.7 cm during 6 months of treatment, which corresponds to between 2.8 and 7.4 cm/year. The mean increase of 5.7 +/- 0.4 cm/year was greater than the pretreatment value of 3.7 +/- 0.2 cm/year (P less than 0.001). There was a positive correlation between growth rate and maximum increase in SM (r = 0.51, P less than 0.05). Antibody against hGH appeared in 3 patients after 2 months; 10 of the 20 patients had antibody after 6 months of treatment. However, the antibody did not suppress the growth effect of met-hGH. Otherwise there were no significant changes in physical, blood, or urine examinations. These results indicate that hGH treatment is useful for the acceleration of growth velocity in patients with Turner's syndrome.

Qualitative differences in effects of recombinant alpha-, beta- and gamma-interferons on human peripheral blood leukocytes in vitro

The in vitro effects of bacteria-produced human interferons alpha 2, beta and gamma on several properties of peripheral blood leukocytes from different healthy donors were compared. Treatment with HuIFN-alpha 2 or HuIFN-beta resulted in inhibition of the proliferative response to phytohaemagglutinin and in closely parallel induction of 2'-5'-oligoadenylate synthetase activity. In contrast, HuIFN-gamma had no significant effect on these two activities. However, all three HuIFN were able to enhance natural killer cell cytotoxicity and the expression of HLA-DR surface antigens, with only quantitative variations from donor to donor. Similar results were observed with glycosylated recombinant hamster-cell-derived HuIFN-gamma and with natural HuIFN-gamma. These data demonstrate qualitative differences in the effects of HuIFN-gamma compared to those of HuIFN-alpha 2 or -beta on cells of the immune system.

The surface of virulent Treponema pallidum: resistance to antibody binding in the absence of complement and surface association of recombinant antigen 4D

The binding of immunoglobulin G present in syphilitic immune rabbit serum, syphilitic human serum, and rabbit antiserum to purified recombinant Treponema pallidum antigen 4D by T. pallidum, Nichols strain, was studied by immunoelectron microscopy. Treponemes were incubated with antiserum under the conditions of the T. pallidum immobilization test, in which T. pallidum-specific antibody renders the organism nonmotile and avirulent only in the presence of complement after a 16-h incubation period in an anaerobic environment. Antibody was not demonstrable on the surface of T. pallidum incubated with nonimmune rabbit serum or normal human serum in the presence of complement. Similarly, in the absence of complement, little or no antibody was found on the treponemal surface after incubation with syphilitic immune rabbit serum, syphilitic human serum, or rabbit antiserum directed against the recombinant 4D antigen. The addition of complement to syphilitic immune rabbit serum, syphilitic human serum, and anti-4D antibody resulted in immobilization and the deposition of antibody on the entire surface of the immobilized organisms. These results corroborate earlier work by other investigators demonstrating the resistance of freshly isolated T. pallidum to antibody binding in a variety of serological tests. Detection of 4D antigen on the surface of immobilized T. pallidum strongly implies that the use of T. pallidum immobilization test conditions provides a means to demonstrate the association of individual surface antigens on virulent T. pallidum. The resistance of T. pallidum to antibody binding may be relevant to the pathogenesis of syphilis.

Native surface association of a recombinant 38-kilodalton Treponema pallidum antigen isolated from the Escherichia coli outer membrane

A recombinant plasmid designated pAW305, containing a 6-kilobase insert of Treponema pallidum DNA, directed the expression of a 38-kilodalton (kDa) treponemal antigen in Escherichia coli. The 38-kDa antigen copurified with the outer membrane fraction of the E. coli cell envelope after treatment with nonionic detergents or sucrose density gradient centrifugation. Rabbits immunized with the recombinant 38-kDa antigen developed antibodies which reacted specifically with a 38-kDa T. pallidum antigen on immunoblots, and 38-kDa antisera specifically immobilized T. pallidum in a complement-dependent manner in the T. pallidum immobilization test. Antisera to the 38-kDa recombinant antigen were also used to demonstrate its native surface association on T. pallidum by immunoelectron microscopy.