Probing the human B-cell repertoire with EBV: polyreactive antibodies and CD5+ B lymphocytes.
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Biomedical subjects
Publications and source records attributed to A L Notkins.
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An immunoglobulin G (IgG) preparation of the serum from a patient with active Graves' disease was used to isolate cDNA clones from a lambda gt11 cDNA library of human thyroid follicular carcinoma tissue by immunoscreening. One of these clones, hML-7, is further characterized herein by sequencing, Northern analysis, and chromosomal mapping. The clone reacted with IgG preparations from the sera of 14 of 19 patients with active Graves' disease but not with IgG preparations from 11 normal individuals, three patients with toxic thyroid adenoma, and three with rheumatoid arthritis. The hML-7 cDNA hybridized to a 3.6 kilobase (kb) mRNA transcript in poly(A+) RNA preparations from human thyroid tissue and continuously cultured rat thyroid cells; expression of this transcript in rat FRTL-5 thyroid cells was positively regulated by TSH. The 3.6 kb transcript was less abundant in rat liver (BRL3A) cells or differentiated rat (L6) myoblasts than in cultured rat thyroid cells and was not detectable in mouse L-M fibroblasts, human IM-9 lymphocytes, Chinese hamster ovary cells, or human cervical carcinoma cells. The cDNA from hML-7 was sequenced and compared with the sequence of cross-hybridizing cDNA clones isolated from human Graves' thyroid and rat FRTL-5 thyroid cell lambda gt11 expression libraries. A 1.05 kb open reading frame, which is highly conserved between human and rat, was defined. The predicted amino acid sequence of 348 residues exhibited a strong homology with the mitochondrial ADP/ATP carrier protein (adenine nucleotide translocase; ADP/ATP translocator) and with two other members of the same mitochondrial protein family, the phosphate carrier and the hydrogen ion uncoupling protein. The gene represented by the hML-7 cDNA has been assigned to human chromosome 10.
The frequency of cell precursors producing Ig of different classes and Ag-binding activities were determined, using EBV-infection and limiting dilution assays, in healthy subjects and patients with autoimmune disease. A large proportion of circulating B cells from healthy subjects were committed to the production of IgM antibodies that were polyreactive and bound a variety of self- and exogenous Ag, i.e., IgG Fc fragment, ssDNA, thyroglobulin, thyroid microsomal Ag, insulin, and tetanus toxoid. Similar frequencies of these polyreactive antibody-producing cells were found in patients with Hashimoto's disease and SLE. In contrast, significantly higher frequencies of cell precursors producing monoreactive IgG autoantibodies to thyroid Ag (thyroglobulin and thyroid microsomal Ag) and ssDNA were found in Hashimoto's disease and SLE patients, respectively. Calculation of the Kd revealed that monoclonal polyreactive antibodies were in general low affinity (Kd, 10(-3) to 10(-7) mol/liter), whereas monoclonal monoreactive autoantibodies were high affinity (Kd, 10(-9) to 10(-11) mol/liter). The detected frequency and high affinity of the monoreactive autoantibodies in Hashimoto's disease and SLE patients were comparable to those of anti-tetanus toxoid and anti-insulin IgG mAb produced by B cell clones from vaccinated healthy subjects and insulin-treated patients with insulin-dependent diabetes mellitus, respectively. These findings support the hypothesis that the autoimmune B cell repertoire in patients with organ-specific and systemic autoimmunity is shaped by Ag-driven responses rather than merely reflecting a polyclonal B cell activation.
In patients with rheumatoid arthritis (RA), circulating CD5+ B lymphocytes, but not CD5- B lymphocytes, are increased in number and size, exist in an activated state, spontaneously proliferate, and secrete Ig that binds to the Fc fragment of IgG. By constructing continuous mAb-secreting cell lines from CD5+ B lymphocytes, the properties and dissociation constants (Kd) of these antibodies were determined. Two types of rheumatoid factors (RFs) with discrete reactivities were produced. The first type is polyreactive and binds with relatively low affinity (Kd, 10(-5) mol/liter) to the Fc fragment of IgG. These antibodies are similar to those produced by CD5+ B cells from healthy subjects. The second type of RF is monoreactive and binds with higher affinity (Kd, 10(-7) mol/liter) to the Fc fragment of IgG. These latter autoantibodies are produced by CD5+ B cells of RA patients, but not healthy subjects. Long-term longitudinal studies are needed to determine the role of these two types of RFs in the pathogenesis of RA.
A global vaccination strategy must take into account production and delivery costs as well as efficacy and safety. A heat-stable, polyvalent vaccine that requires only one inoculation and induces a high level of humoral and cellular immunity against several diseases is therefore desirable. A new approach is to use live microorganisms such as mycobacteria, enteric bacteria, adenoviruses, herpesviruses and poxviruses as vaccine vectors. A potential limitation of live polyvalent vaccines, however, is existing immunity within the target population not only to the vector, but to any of the expressed antigens. This could restrict replication of the vector, curtail expression of antigens, and reduce the total immune response to the vaccine. Recently acquired immunity to vaccinia virus can severely limit the efficacy of a live recombinant vaccinia-based vaccine, so a strategy involving closely spaced inoculations with the same vector expressing different antigens may present difficulties. We have constructed a recombinant vaccinia virus that expresses surface proteins from two diverse pathogens, influenza A virus haemagglutinin and herpes simplex virus type 1 (HSV-1) glycoprotein D. Mice that had recently recovered from infection with either HSV-1 or influenza A virus could still be effectively immunized with the double recombinant.
CD5+ lymphocytes constitute a major subset of the normal human B cell repertoire. We found here, by transformation with EBV and limiting dilution analysis, that the majority of CD5+ B cells from healthy subjects are committed to the production of antibodies with rheumatoid factor-like activity. By fusing the EBV-transformed cells generated from CD5+ B lymphocytes with human-mouse heterohybrid cells, we constructed continuous cell lines producing mAb. These mAb bound not only to the Fc fragment of IgG but also at varying degrees to other self-Ag, such as ssDNA, thyroglobulin, and insulin, as well as to exogenous Ag, such as tetanus toxoid, LPS from Gram-negative and polysaccharides from Gram-positive bacteria. Competitive inhibition studies revealed that although each of the mAb reacted with the Fc fragment of IgG, their functional affinities for other Ag varied by as much as 1000-fold. Our studies argue that broad polyreactivity is an inherent property of the antibodies produced by CD5+ B lymphocytes and that these antibodies may be what has been referred to as the "natural antibodies" of the serum.
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Human peripheral B lymphocytes were transformed with Epstein-Barr virus and probed with an antiidiotypic antibody made against a human monoclonal autoantibody. Six cell lines were isolated that produced antibodies bearing a common idiotope. Despite the presence of this common idiotope, the antibodies showed antigen-binding specificities different from that of the parental antibody to which the antiidiotypic antibody was made. By probing Epstein-Barr virus-transformed cells with well-characterized antiidiotypic antibodies, it should now be possible to isolate and determine the frequency of B cells bearing specific idiotopes in the human repertoire and to study the antigen-binding properties of these antibodies.
Peripheral blood lymphocytes from 29 patients with autoimmune diseases and eight normal controls were cultured in vitro. Several weeks later, lymphocyte proliferation was observed in many of these cultures. Cell lines were obtained from about half of the donors, at a frequency of approximately 1 in 10(7) lymphocytes. Outgrowth occurred only in cultures from patients who had antibodies to the viral capsid antigen of Epstein-Barr virus (EBV). The proliferating cells also contained EBV nuclear antigen, an occurrence confirming that proliferation was a result of latent EBV infection of the donors. Supernatants from these cell lines were tested for autoantibodies by screening against normal tissues. About 30% of the cell lines made autoantibodies, many of which reacted with smooth muscle or epithelial cells. Because EBV is harbored in a latent form in the majority of the adult population, reactivation of latent EBV infection in vivo may explain the production of autoantibodies seen in a variety of immunoregulatory disorders.
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Previously we showed that mice immunized with a vaccinia virus vector expressing the herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) gene (vaccinia/gD) were protected against both lethal and latent infections with HSV-1 for at least 6 weeks after immunization (K. J. Cremer, M. Mackett, C. Wohlenberg, A. L. Notkins, and B. Moss, Science 228:737-740, 1985). In the experiments described here, we examined long-term immunity to HSV following vaccinia/gD vaccination, the effect of revaccination with vaccinia/gD, and the impact of previous immunity to vaccinia virus on immunization with the gD recombinant. Mice immunized with vaccinia/gD showed 100, 100, and 80% protection against lethal infection with HSV-1 at 18, 44, and 60 weeks postimmunization, respectively. Protection against latent trigeminal ganglionic infection was 70, 50, and 31% at 6, 41, and 60 weeks postvaccination, respectively. To study the effect of reimmunization on antibody levels, mice vaccinated with vaccinia/gD were given a second immunization (booster dose) 3 months after the first. These mice developed a 10-fold increase in neutralizing-antibody titer (221 to 2,934) and demonstrated a significant increase in protection against lethal HSV-1 challenge compared with animals that received only one dose of vaccinia/gD. To determine whether preexisting immunity to vaccinia virus inhibited the response to vaccination with vaccinia/gD virus, mice were immunized with a recombinant vaccinia virus vector expressing antigens from either influenza A or hepatitis B virus and were then immunized (2 to 3 months later) with vaccinia/gD. These mice showed reduced titers of neutralizing antibody to HSV-1 and decreased protection against both lethal and latent infections with HSV-1 compared with animals vaccinated only with vaccinia/gD. We conclude that vaccination with vaccinia/gD produces immunity against HSV-1 that lasts over 1 year and that this immunity can be increased by a booster but that prior immunization with a vaccinia recombinant virus expressing a non-HSV gene reduces the levels of neutralizing antibody and protective immunity against HSV-1 challenge.
Epstein-Barr virus (EBV) was purified and biotinylated without significant loss of its cell-transforming activity. The use of biotinylated virus in conjunction with antibodies specific for selected cell surface molecules and flow cytometric analysis allowed for the positive identification of the virus-binding lymphocytes among a heterogeneous mononuclear cell population. Biotinylated EBV efficiently bound to all B lymphocytes, including those bearing surface mu, delta, gamma, and alpha immunoglobulin heavy chains or the surface CD5 (Leu-1) marker, but not to T lymphocytes, natural killer cells, or monocytes. By using biotinylated EBV and specific monoclonal antibodies in competitive inhibition experiments, it was also found that the virus attaches to an epitope on the CR2 molecule (the receptor for C3d and EBV), which is close to or identical with the one recognized by OKB7 monoclonal antibody, and that cell surface structures other than CR2 cannot mediate attachment of EBV. Moreover, studies on the binding of the virus to induced B lymphocytes (cells in S through G2 phase), and this was associated with the disappearance of the surface CR2 molecule and the inability of the virus to attach to these cells. The approach described here should be useful in studying the attachment of other viruses, identifying the specific cell types involved, and analyzing the effect of the cell cycle on virus binding.
Mice infected with reovirus type 1 developed a mild thyroiditis characterized by focal destruction of acinar tissue, infiltration of inflammatory cells, and autoantibodies to thyroglobulin and microsomal antigens. Thyroid involvement appears to be part of a more generalized virus-induced polyendocrine disease.
The possible role of viruses as the cause of some thyroid disorders was evaluated in three strains of mice neonatally infected with lymphocytic choriomeningitis virus. We report the first definitive evidence that viruses can persist in the thyroid gland, particularly thyroid epithelial cells in which thyroglobulin is synthesized. Concomitant with the infection of these cells was a significant reduction in the level of thyroglobulin mRNA and circulating thyroid hormones. Another virus that causes persistent infection but does not replicate in the thyroid gland failed to alter serum levels of thyroid hormones, indicating the thyroid dysfunction was not a generalized result of stress accompanying a persistent infection. This alteration in thyroid homeostasis during persistent infection with lymphocytic choriomeningitis virus is not caused by autoantibodies to the thyroid. Moreover, despite infection of the thyroid gland, neither necrosis nor inflammation occurs. Thyroid dysfunction was noted both when persistence was initiated at birth and in utero during congenital infection. These observations in an experimental model raise the issue that viruses may play a role in the pathogenesis of some thyroid disorders in man.
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Since its discovery, lactic dehydrogenase virus (LDV) has remained unique as a model of long-term enzyme elevation due to impairment of enzyme clearance. The present study shows that mice inoculated with silica develop an increase in plasma lactate dehydrogenase (LDH) lasting for at least 6 months and that the enzyme elevation is due, at least in part, to impairment of clearance. The extent of the enzyme elevation is dependent on both the dose and route of silica administration and mice that had received both silica and LDV showed a more profound impairment of LDH clearance than mice that had received silica or LDV alone. Examination of the factors that regulate circulating enzyme levels in normal mice revealed that whereas there was no difference in resting enzyme levels among several inbred strains of mice (BALB/cAnN, NZBWF1/J,B10.D2/nSnN, and A/J mice), when mice were stressed by the administration of an enzyme load, certain inbred strains (BALB/cAnN) cleared the enzyme rapidly and others (B10.D2/nSnN) cleared the enzyme slowly. Moreover, in B10.D2/nSnN mice, enzyme clearance was age-related. When different strains of mice were infected with LDV, LDH levels were substantially higher in the circulation of slow enzyme clearers as compared to rapid enzyme clearers. It is concluded that both environmental and genetic factors influence the clearance of LDH and that impairment of enzyme clearance may be a more important factor than previously suspected in regulating enzyme levels in disease states.
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Previously we reported on the production and characteristics of a number of human monoclonal autoantibodies. All of these autoantibodies were of the IgM class and reacted with antigens in multiple organs. In this study we generated IgG murine monoclonal anti-idiotypic antibodies against five human monoclonal autoantibodies, (i.e., MOR-h2, MOR-h3, MOR-h4, CG1, and CG2). These anti-idiotypic antibodies reacted strongly with the corresponding human monoclonal autoantibody, but minimally or not at all with other human monoclonal autoantibodies. By using these anti-idiotypic antibodies as probes, we screened sera obtained from normal individuals and patients with insulin-dependent diabetes mellitus, Hashimoto's thyroiditis, and systemic lupus erythematosus for the expression of idiotopes. Our study showed that the idiotopes recognized by three of the anti-idiotypic antibodies, i.e., anti-CG1, anti-CG2, and anti-MOR-h2, were not expressed, but the idiotopes recognized by two of the anti-idiotypic antibodies, i.e., anti-MOR-h3 and anti-MOR-h4, were expressed in normal individuals. In patients with autoimmune disorders, there was no increase in the expression of the CG1, CG2, and MOR-h2 idiotopes, but 45 and 23% of the patients with systemic lupus erythematosus showed a significant increase in the expression of the MOR-h3 and MOR-h4 idiotopes respectively. These findings show that there is widespread expression in the B cell repertoire of certain autoantibody-associated idiotopes.