Biomedical subjects

S A Patibandla

Publications and source records attributed to S A Patibandla.

12 recordsLinked to original sources

PubMed1999

Comparison of immune responses to extracellular domains of mouse and human thyrotropin receptor.

The mouse and human thyrotropin receptors show greater than 87% homology in their amino acid sequences. However, glycosylated extracellular domains of mouse (mET-gp) and human (hET-gp) thyrotropin receptors showed differences in their ability to react with patient autoantibodies to thyrotropin receptor (TSHR). To test for potential differences in their immunogenicity, we immunized BALB/c mice with either gel pure non-glycosylated ectodomain of human TSHR (ETSHR II), or hET-gp (hET-gp III), or mET-gp (mET-gp III). Alternatively, mice were primed with gel pure hET-gp or mET-gp and subsequently immunized with insect cells expressing hET-gp (hET-gp II) or mET-gp (mET-gp II) respectively. All groups of mice immunized with TSHR developed high titers of antibodies against the respective immunogens. As shown earlier, sera obtained from mice immunized with ETSHR showed strong reactivity to peptide 1 (aa 22-41) and weak reactivity to peptides 23 (aa 352-371), 24 (aa 367-386), 25 (aa 382-401), and 26 (aa 397-415). Mice immunized with hET-gp or mET-gp showed comparable titers to peptides 1 and 23 and lower reactivity to other peptides. Mice immunized with hET-gp showed higher TBII reactivity (52.2%) compared to mice immunized with either ETSHR (20.9%) or mET-gp (34.5%). Peptides from the C-terminal region of ETSHR could neutralize the TBII activities of sera from mice immunized with ETSHR or hET-gp but not mET-gp. Compared to corresponding control mice, T4 levels in mET-gp II mice were only marginally higher. These data suggested that outcome of immunization with mouse ETSHR is comparable to that seen after immunization with human ETSHR.

Amino Acid Sequence↗

PubMed1999

Selective binding of thyrotropin receptor autoantibodies to recombinant extracellular domain of thyrotropin/lutropin-chorionic gonadotropin receptor chimeric proteins.

The extracellular domain of the glycosylated human thyrotropin receptor (ET-gp) contains epitopes that can adsorb pathogenic antibodies from sera of patients with Graves' disease (GD). In an attempt to define the regions within the ETSHR with which autoantibodies interact, we expressed extracellular domains of eight thyrotropin receptor/chorionic gonadotropin receptor (TSHR/LH-CGR) chimeric proteins in insect cells. The levels of expression were high and chimeric proteins were glycosylated. Chimeric proteins designated as EMc2+4 and EMc2+3+4, in which amino acids (aa) 90-165 and 261-370, and aa 90-370, respectively, of TSHR were replaced with corresponding aa of LH-CGR, partially reversed the thyrotropin binding inhibitory immunoglobulin (TBII) activity of experimental anti-TSHR antisera (anti-ET-gp). The other six chimeras almost completely reversed the TBII activity of these anti-ET-GP antisera. Next, we tested the ability of these chimeric proteins to reverse the TBII activity of GD patients' sera. Similar to our earlier study, ET-gp protein reversed the TBII activity of all eight GD patients' sera tested. Chimera EMc2, in which aa 90-165 of TSHR has been replaced with corresponding aa of LH-CGR, and EMc2+4 partially reversed the TBII activity of only three of the eight GD patients' sera. However, the other six chimeric proteins failed to neutralize the TBII activity of any of GD patients' sera. These data showed the following: (1) There is considerable heterogeneity amongst autoantibodies in GD patients' sera, (2) The TBII activity of some, but not others, is dependent on aa 90-165 and 261-370, and (3) Most Graves' sera, with TBII activity, failed to react with chimeric proteins in which either N-terminal or C-terminal regions of the extra cellular domain of the TSHR were replaced with corresponding regions of LH-CGR. These results suggest that the TBII activity of GD patients' sera is dependent on conformational epitopes and replacement of certain regions of TSHR with homologous regions of LH-CGR results in sufficient alteration in the conformation of the protein leading to loss of reactivity.

Animals↗

PubMed1999

Direct detection of Sabin poliovirus vaccine strains in stool specimens of first-dose vaccinees by a sensitive reverse transcription-PCR method.

A multiplex reverse transcription-PCR method was optimized to monitor the duration of excretion of Sabin poliovirus strains in stools of vaccinees following administration of the first dose of the trivalent oral vaccine. The assay detected approximately 1 50% tissue culture infective dose of each poliovirus serotype spiked into cell culture media. Although PCR inhibitors were frequently encountered in the stool specimens, a 1:20 dilution of the extracted RNA was sufficient to obtain a positive PCR result. Analysis of 195 stool specimens collected from 26 vaccinees showed that poliovirus types 1, 2, and 3 were identified more frequently by PCR than by tissue culture isolation. The percentages of specimens positive by PCR for poliovirus types 1, 2, and 3 were 67.2, 82.6, and 53.8, respectively. In contrast, the culture method identified types 1, 2, and 3 virus in 55.4, 64.1, and 27.7% of the samples, respectively. Poliovirus type 2 excretion was detected by PCR in practically all of the oral poliovirus vaccine recipients for 4 to 8 weeks following vaccination. In contrast, excretion of type 1 and 3 viruses was more variable, with a range of 1 to 8 weeks. Shedding of type 3 virus ceased in approximately 70% of vaccinees within a week after immunization. In addition to an enhanced sensitivity for the detection of poliovirus, this PCR method permits the direct characterization of virus in stool specimens without further passage in culture, which may select for genetic variants that may not accurately reflect the virus composition in the original specimen.

Animals↗

PubMed1997

Requirement of glycosylation of the human thyrotropin receptor ectodomain for its reactivity with autoantibodies in patients' sera.

To understand the role of glycosylation on autoantibody reactivity, we expressed cDNA encoding amino acid residues 22 to 416 of the human thyrotropin receptor (TSHR), along with the baculovirus-encoded glycoprotein 67 signal sequence (ETSHR-gp) in insect cells. N-terminal sequence analysis revealed that the signal peptide was cleaved and confirmed the identity of ETSHR-gp protein. The molecular mass of the ETSHR-gp protein was 63 kDa and was higher than the expected molecular mass of 45 kDa, suggesting that the protein was glycosylated. Carbohydrate analysis showed that the protein was glycosylated and that mannose was the major oligosaccharide. A nonglycosylated recombinant ETSHR protein expressed earlier in our laboratory neutralized TSH-binding-inhibitory Ig (TBII) activity in the sera of rabbits immunized with the protein but did not neutralize TBII activity in the sera of patients. In contrast, the glycosylated ETSHR-gp protein neutralized TBII activity in the sera of both experimental animals and patients with autoimmune thyroid disorders. Furthermore, only the ETSHR-gp protein completely neutralized the activities of stimulatory and blocking Abs in the sera of patients with hyperthyroidism and hypothyroidism, respectively. These data clearly show that glycosylated ETSHR-gp, but not the nonglycosylated ETSHR protein, can react with autoantibodies in patients' sera and that it has the epitopes required for the binding of TBII, thyroid stimulatory Abs, and thyroid stimulatory blocking Abs. Moreover, these data suggest that glycosylation might be an important determinant of autoantigenicity of human TSHR.

Animals↗

PubMed1997

Differential reactivities of recombinant glycosylated ectodomains of mouse and human thyrotropin receptors with patient autoantibodies.

We expressed the extracellular domain of the mouse TSH receptor (mET-gp) using the baculovirus expression system. The recombinant protein was identified as mET-gp by immunoblotting and N-terminal amino acid sequencing. Carbohydrate analysis of the recombinant protein showed that the protein is glycosylated. Experimental antibodies raised against the extracellular domain of the human TSHr (ETSHr) were assayed for reactivity against mET-gp and glycosylated human ETSHr (ETSHr-gp) in an ELISA and found to be comparable. Similarly, both mET-gp and ETSHr-gp proteins neutralized the TSH binding inhibitory immunoglobulin (TBII) activity of rabbit anti-ETSHr antibodies in a RRA. However, when these proteins were compared for their ability to neutralize TBII and blocking activities (TSBAb) of IgG from patients with thyroid autoimmune disorders, only ETSHr-gp was able to neutralize these activities. In contrast, mET-gp partially neutralized, whereas ETSHr-gp completely neutralized the stimulatory (TSAb) activities of IgG from patients. Analyses of reactivities of these two proteins against a panel of antipeptide and monoclonal antibodies and their protein sequences showed differences in some specific epitopes. These data showed that in spite of significant homology between the two proteins, they exhibit specific epitope differences that are sufficient to cause divergence in their ability to react with patient autoantibodies to TSHr. This suggests that the two proteins might differ in their three-dimensional structure.

Amino Acid Sequence↗

PubMed1997

Flow cytometric analyses of antibody binding to Chinese hamster ovary cells expressing human thyrotropin receptor.

To develop a method that can be used to directly detect binding of antibodies to TSH receptor (TSHr), we employed Chinese hamster ovary (CHO) cells permanently transfected with a human TSHr complementary DNA (CHOR). These cells showed increased cAMP production when treated with either human TSH or thyroid-stimulating antibodies and decreased TSH-mediated cAMP production when treated with stimulation-blocking antibodies. We employed flow cytometry and rabbit antibodies against the extracellular domain of the TSHr (ETSHr) to test whether these cells can be used to directly detect and quantitate the binding of anti-TSHr antibodies. Rabbit anti-ETSHr bound specifically to CHOR cells, and the binding could be blocked with purified ETSHr. To test the feasibility of using these cells for epitope mapping, we tested the binding of rabbit antibodies raised against several synthetic TSHr peptides. Rabbit antipeptide 92 (amino acids 12-30) and 91 (amino acids 32-46) showed little or no binding to the CHOR cells. In contrast, antibodies raised against peptides 93 (amino acids 316-330), 95 (aa 325-345), 3A (aa 357-372), 367 (aa 367-386), and 1B (aa 362-376) showed significant binding to the CHOR cells. The specificity of binding of antipeptide antibodies was demonstrated by a complete inhibition of binding by corresponding peptides. When TSH-binding inhibitory Ig-positive sera from 15 patients with hyperthyroidism were tested, 8 of them showed specific binding to the CHOR cells compared to their relative binding to normal CHO cells; sera from all normal individuals tested did not exhibit specific binding to CHOR cells. These studies showed the usefulness of CHOR cells and flow cytometry in epitope mapping using sera with known specificities and the potential usefulness of the technique to detect anti-TSHr antibodies in patient sera.

Animals↗

PubMed1996

Purification and characterization of a recombinant human thyroid peroxidase expressed in insect cells.

Thyroid peroxidase (TPO) is an essential enzyme for thyroid hormone biosynthesis and is an autoantigen against which antibodies are found in a number of autoimmune thyroid disorders. Large quantities of pure TPO are essential for understanding its structure and role in normal thyroid function and thyroid diseases. In this study, we describe the production of human TPO (hTPO) using a baculovirus expression vector in insect cells. TPO was sequentially extracted from insect cells using various buffers and the protein was purified to homogeneity on a C4 reversed-phase semipreparative column using high-performance liquid chromatography. The purified protein was identified as hTPO by enzyme-linked immunosorbent assay, Western blot, and amino acid sequence analyses. Carbohydrate analysis of the recombinant hTPO showed that the protein is glycosylated and mannose is the major oligosaccharide. We have extended the carbohydrate analysis by establishing the occurrence of N-acetyl galactosamine which suggested that the recombinant hTPO might contain O-glycosyl moieties. Purified hTPO reacted specifically with sera from patients with Hashimoto's thyroiditis. Crude as well as purified hTPO did not show any enzymatic activity when produced in Sf9 insect cells grown in serum free medium. In contrast, hTPO produced in the presence of 10% fetal bovine serum containing 1 microgram/ml of haematin was enzymatically active. However, the enzymatic activity of the recombinant hTPO was lower than that often found with hTPO purified from thyroid tissue. Availability of purified hTPO in relatively large quantities should allow further structural and immunological studies.

Amino Acid Sequence↗

PubMed1996

Autoimmunity to the thyroid stimulating hormone receptor.

Thyroid disorders are the most common endocrine diseases and affect a large segment of the population. Most of the thyroid diseases are autoimmune in nature and can be broadly grouped into two categories; one mediated by autoimmune responses to the thyroglobulin (i.e. Hashimoto's thyroiditis), and the other mediated by autoimmunity to the thyrotropin receptor (primarily Graves' disease). Although patients with autoimmune thyroid diseases exhibit immune responses against a number of thyroid antigens, such as thyroglobulin, thyrotropin receptor and thyroid peroxidase, responses directed against a specific antigen appear to play an important role in the disease pathogenesis. For example, Hashimoto's thyroiditis is primarily mediated by T cell responses directed toward the thyroglobulin receptor, whereas Graves' disease is mediated by antibodies directed against the thyrotropin receptor. In this review we will focus on thyroid diseases mediated by autoimmune responses to the thyrotropin receptor.

Animals↗

PubMed1996

Experimental autoimmunity to thyrotropin receptor.

Since the cloning of a full length cDNA encoding the thyrotropin receptor (TSHr), several laboratories have been actively trying to develop an optimal animal model to understand the pathogenesis of TSHr mediated autoimmune diseases and have made considerable progress. To date, results from our laboratory have indicated that the nature of the antigen, and the adjuvant used for immunization, immunogenetic background of the animal and fine specificities of antibodies elicited might play an important role in determining the qualitative nature of the antibody response. Although an ideal animal model for either Graves' disease or primary myxedema is not yet available, ongoing studies in our laboratory and elsewhere hold promise for establishing animal models for various TSHr mediated autoimmune diseases in the near future.

Amino Acid Sequence↗

PubMed1996

Thyrotropin (TSH) receptor antibodies (TSHrAb) can inhibit TSH-mediated cyclic adenosine 3',5'- monophosphate production in thyroid cells by either blocking TSH binding or affecting a step subsequent to TSH binding.

In the present study, rabbit antibodies that possess thyroid stimulation-blocking activity were used to investigate potential mechanisms by which TSH receptor antibodies can inhibit thyroid cell function. The antibodies were produced against two synthetic peptides corresponding to amino acids 357-372 (p357) and 367-386 (p367) of the human TSHr (hTSHr). By enzyme-linked immunosorbent assay, both antisera (alpha 357 and alpha 367) had high titers ( > 1:100,000) of IgG against their respective peptides and recombinant extracellular TSHr protein (ETSHr); alpha 357 had a low IgG titer to p367 (1:800), and alpha 367 had a low IgG titer to p357 ( < 1:200). Based on competitive inhibition studies, alpha 357 and alpha 367 displayed similar relative binding affinities for their respective peptides and for recombinant ETSHr. When tested by commercial RRA, alpha 357 did not block (TSH binding inhibition index, -3.7%), whereas alpha 367 blocked TSH binding to TSHr (TSH binding inhibition index, 53.9%). The blocking effect of alpha 367 could be reversed by incubating the antiserum with p367 before assay. When applied alone to FRTL-5 cells, IgG from alpha 357 inhibited [compared to normal rabbit IgG (NRI); P < 0.01] based cAMP production by the cells, whereas IgG from alpha 367 did not. IgG from both alpha 357 and alpha 367, however, were able to inhibit (P < 0.001) TSH-mediated cAMP production by FRTL-5 cells [bovine (b) TSH, 2.5 x 10(-10) M; cAMP (mean +/- SD; picomoles per ml): NRI, 62.5 +/- 6.1; alpha 357, 12.2 +/- 2.4; alpha 367, 36.2 +/- 3.5]. Alpha 357 continued to inhibit (P < 0.05) cAMP production by FRTL-5 cells in 10(-8) M bTSH, whereas alpha 367 no longer inhibited cAMP production at bTSH concentrations above 5 x 10(-10) M. Compared to NRI, both alpha 357 and alpha 367 were also able to inhibit (P < 0.001) Graves' IgG-mediated cAMP production by FRTL-5 cells. When IgG were tested on FRTL-5 cells in the presence of 10(-7) M forskolin, only alpha 357 inhibited (P < 0.001) cAMP production (NRI, 75.1 +/- 4.8; alpha 357, 52.3 +/- 4.5; alpha 367, 77.2 +/- 1.4). To determine whether the inhibitory effect of alpha 357 on forskolin-mediated stimulation was thyroid cell dependent, IgG were tested on Chinese hamster ovary (CHO) cells transfected with the complementary DNA of the hTSHr (CHO-R). Again, alpha 357 inhibited (P < 0.005) cAMP production mediated by forskolin (at 10(-7) M; NRI, 68.7 +/- 4.4; alpha 357, 36.8 +/- 5.7; alpha 367, 64.6 +/- 8.5). alpha 357 did not inhibit forskolin-mediated cAMP production by untransfected CHO cells (CHO-N), indicating that the inhibitory effect of alpha 357 on forskolin stimulation was TSHr dependent. In addition, alpha 357 inhibited (P < 0.01) basal cAMP production by CHO-R cells, but not by CHO-N cells. alpha 367 had no effect on the basal cAMP production in either CHO-R or CHO-N cells. Neither alpha 357 nor alpha 367 inhibited cholera toxin-mediated cAMP production in FRTL-5 cells. In all relevant bioassays, the inhibitory effects of alpha 357 and alpha 367 could be reversed by preincubating the IgG with the respective peptides. From these data, we conclude that 1) alpha 367 binds to the ETSHr and blocks TSH-mediated cAMP production by inhibiting TSH from binding to its receptor; 2) alpha 357 binds to the TSHr and, without blocking TSH binding, inhibits TSH-mediated cAMP production at a step(s) subsequent to ligand binding that affects adenylate cyclase activity; and 3) forskolin-mediated cAMP production by thyroid cells can be inhibited by IgG that bind directly to the TSHr.

Animals↗

PubMed1996

Influence of adjuvants on the induction of autoantibodies to the thyrotropin receptor.

To determine the influence of adjuvant on the induction of antibodies to thyrotropin receptor (TSHR), we immunized BALB/c mice with a extracellular domain of the TSHR (ETSHR) protein in complete Freund's adjuvant (CFA), Titer Max (TM) and Gerbu. Similarly, control groups of mice were immunized with bovine serum albumin (BSA) in each of the different adjuvants. As determined by ELISA, ETSHR given along with CFA elicited high titers of antibodies to ETSHR which were mainly restricted to the IgG1 subclass. Mice immunized with ETSHR in TM also developed high titers of anti-ETSHR antibodies but had higher levels of both IgG1 and IgG2a. However, immunization with ETSHR in Gerbu resulted in low titers of antibodies, restricted to IgG1 subclass. Immunization of mice with BSA in each of the three adjuvants induced higher antibody titers to BSA. The subclass of antibodies in mice immunized with BSA in CFA and TM were predominantly IgG1 and IgG2a with lower levels of IgG2b, whereas in Gerbu treated group, antibody to BSA was restricted to IgG1 subclass. Analysis of specificity of antibodies against ETSHR, in mice immunized with ETSHR, revealed that irrespective of the adjuvant used, the dominant reactivity was against peptide 1 (AA 22-41) with weaker reactivity against several other. peptides. The only exception was in mice immunized with ETSHR in TM which also showed significant reactivity against peptide 23 (AA 352-371). Mice immunized with the ETSHR in CFA or in TM showed elevated levels of serum TSH binding inhibitory immunoglobulins (TBII). However, mice immunized with ETSHR in Gerbu, which had lower titers of antibodies to ETSHR, showed normal TBII levels. These studies showed that adjuvant composition could influence the titer, subclass and fine specificity of antibodies to ETSHR which in turn could affect the development of TBII activity.

Adjuvants, Immunologic↗

PubMed1995

Thyrotropin receptor-specific antibodies in BALB/cJ mice with experimental hyperthyroxinemia show a restricted binding specificity and belong to the immunoglobulin G1 subclass.

Immunization with the extracellular domain of TSH receptor (TSHR) led to the development of hyperthyroxinemia in BALB/cJ, but not C57BL/6J, SJL/J, and B10.BR, mice. Earlier, human studies had shown that thyroid-stimulating antibodies are predominantly of the immunoglobulin G1 (IgG1) subclass with a narrow specificity to TSHR, and antibodies that block thyroid function could be of any subclass with a broader specificity. Therefore, antibody responses in susceptible (BALB/cJ) and resistant (SJL/J) mice were characterized. There were no significant differences in the titers, relative affinities, or isotypes of antibodies against the TSHR. BALB/cJ and SJL/J sera reacted with 2 and 7 of 26 overlapping peptides from the extracellular domain of the TSHR. The ability of sera from BALB/cJ and SJL/J mice to block TSH binding to TSHR was reversed by 1 and 6 of the reactive peptides, respectively. BALB/cJ mice showed predominantly an IgG1 response against the TSHR and peptides, whereas SJL/J mice showed varying levels of all IgG subclasses. Although SJL/J sera reacted with peptides to which blocking antibodies bind, they did not show hypothyroidism, suggesting that their sera contained a mixture of blocking and stimulating antibodies that negated the effects of each other. In contrast, some TSHR-specific antibodies in BALB/cJ probably represented stimulating antibodies.

Animals↗