Identification of Prevotella Oralis as a possible target antigen in children with Enthesitis related arthritis.

OBJECTIVES: Patients with Crohn's disease often produce antibodies against flagellated intestinal bacteria. There are mixed data as to whether such antibodies are present in patients with spondyloarthritis. Our objectives were to evaluate for the presence of antibodies against intestinal organisms in children with enthesitis related arthritis (ERA). METHODS: Children with ERA and healthy controls were recruited at three sites. Sera were plated on a nitrocellulose array and incubated with labelled antibodies to human IgA and IgG. RESULTS: At UAB, patients and controls had similar antibody levels against the majority of the bacteria selected, with the exception of increased IgA antibodies among ERA patients against Prevotella oralis (1231 [IQR 750, 2566] versus 706 [IQR 428, 1106], p = .007.) These findings were partially validated at a second but not at a third site. CONCLUSIONS: ERA patients may produce increased IgA antibodies against P. oralis. The possible significance of this finding bears further exploration.

Commensal A4 bacteria inhibit intestinal Th2-cell responses through induction of dendritic cell TGF-ß production.

It has been shown that while commensal bacteria promote Th1, Th17 and Treg cells in lamina propria (LP) in steady-state conditions, they suppress mucosal Th2 cells. However, it is still unclear whether there are specific commensal organisms down-regulating Th2 responses, and the mechanism involved. Here we demonstrate that commensal A4 bacteria, a member of the Lachnospiraceae family, which produce an immunodominant microbiota CBir1 antigen, inhibits LP Th2-cell development. When transferred into the intestines of RAG(-/-) mice, CBir1-specific T cells developed predominately towards Th1 cells and Th17 cells, but to a lesser extent into Th2 cells. The addition of A4 bacterial lysates to CD4(+) T-cell cultures inhibited production of IL-4. A4 bacteria stimulated dendritic cell production of TGF-ß, and blockade of TGF-ß abrogated A4 bacteria inhibition of Th2-cell development in vitro and in vivo. Collectively, our data show that A4 bacteria inhibit Th2-cell differentiation by inducing dendritic cell production of TGF-ß.

Human seroreactivity to gut microbiota antigens.

BACKGROUND: Although immune responses directed against antigens from the intestinal microbiota are observed in certain diseases, the normal human adaptive immune response to intestinal microbiota is poorly defined. OBJECTIVE: Our goal was to assess the adaptive immune response to the intestinal microbiota present in 143 healthy adults and compare this response with the response observed in 52 children and their mothers at risk of having allergic disease. METHODS: Human serum was collected from adults and children followed from birth to 7 years of age, and the serum IgG response to a panel of intestinal microbiota antigens was assessed by using a novel protein microarray. RESULTS: Nearly every subject tested, regardless of health status, had serum IgG that recognized a common set of antigens. Seroreactivity to the panel of antigens was significantly lower in atopic adults. Healthy infants expressed the highest level of IgG seroreactivity to intestinal microbiota antigens. This adaptive response developed between 6 and 12 months of age and peaked around 2 years of age. Low IgG responses to certain clusters of microbiota antigens during infancy were associated with allergy development during childhood. CONCLUSIONS: There is an observed perturbation of the adaptive response to antigens from the microbiota in allergic subjects. These perturbations are observable even in childhood, suggesting that optimal stimulation of the adaptive immune system by the microbiota might be needed to prevent certain immune-mediated diseases.

Downregulation of microRNA-107 in intestinal CD11c(+) myeloid cells in response to microbiota and proinflammatory cytokines increases IL-23p19 expression.

Commensal flora plays an important role in the development of the mucosal immune system and in maintaining intestinal homeostasis. However, the mechanisms involved in regulation of host-microbiota interaction are still not completely understood. In this study, we examined how microbiota and intestinal inflammatory conditions regulate host microRNA expression and observed lower microRNA-107 (miR-107) expression in the inflamed intestines of colitic mice, compared with that in normal control mice. miR-107 was predominantly reduced in epithelial cells and CD11c(+) myeloid cells including dendritic cells and macrophages in the inflamed intestines. We demonstrate that IL-6, IFN-γ, and TNF-α downregulated, whereas TGF-ß promoted, miR-107 expression. In addition, miR-107 expression was higher in the intestines of germ-free mice than in mice housed under specific pathogen-free conditions, and the presence of microbiota downregulated miR-107 expression in DCs and macrophages in a MyD88- and NF-κB-dependent manner. We determined that the ectopic expression of miR-107 specifically repressed the expression of IL-23p19, a key molecule in innate immune responses to commensal bacteria. We concluded that regulation of miR-107 by intestinal microbiota and proinflammatory cytokine serve as an important pathway for maintaining intestinal homeostasis.

Prospective observational study of treatment pattern, effectiveness and safety of zoledronic acid therapy beyond 24 months in patients with multiple myeloma or bone metastases from solid tumors.

PURPOSE: To study the treatment patterns, effectiveness and safety of zoledronic acid (ZOL) beyond 2 years of therapy, given the paucity of data on long-term treatment in daily clinical practice. METHODS: Patients with multiple myeloma (MM) or solid tumor bone metastases (STM) and at least 24 months of regular q3-4w ZOL therapy were followed prospectively for an additional 18 months beyond the 24 months required for study entry. End-points included ZOL exposure, incidence of skeletal related events (SRE), and safety. RESULTS: In all, 298 evaluable patients were enrolled. The mean continuation rate of ZOL was 90.6%. Exposure to ZOL decreased with time in all patients, but was lower (50.0% vs. 67.6%; p<0.001) and with higher discontinuation rates (incidence rate ratio [IRR]=1.95; p=0.002) in MM compared to the STM group. ZOL suppressed the rate of SREs similarly during the study as compared to before inclusion (0.12 vs. 0.13 events per person-year; p=0.7). At 18 months, 84.5% remained SRE-free. In STM patients, persistent ZOL therapy was associated with lower SRE risk (hazard ratio [HR]=0.42; p=0.01), but not in MM. Renal deterioration occurred in 3.7% and osteonecrosis of the jaw (ONJ) developed in 6.0%, with dental trauma increasing ONJ risk (HR=4.67; p=0.002). CONCLUSIONS: Beyond 2 years of therapy, treatment patterns of ZOL were heterogeneous and SRE rates were low. The safety profile of ZOL was acceptable, and interrupting ZOL in patients with solid tumors was associated with a higher risk of SREs.

Immune checkpoint inhibitor refractory colitis leading to total colectomy in a melanoma patient.

Immunotherapy is becoming more and more relevant in the treatment of advanced melanoma. Proper management of its side effects can prevent severe complications. We describe the case of a 73-year-old patient with severe refractory colitis secondary to immunotherapy. The patient has been treated for 6 months with Nivolumab, an anti-PD-1, as adjuvant therapy for locally advanced melanoma. He was admitted to the hospital with a deteriorating general condition associated with severe diarrhea and rectal bleeding for 3 weeks. Despite three lines of treatment (high dose corticosteroids, infliximab, mycophenolate mofetil), the patient still presented clinical and endoscopic colitis, with additional infectious complications. The patient required surgical management for total colectomy. In this article we present one of the rare cases of autoimmune colitis that did not respond to various immunosuppressive treatments and required surgery.

Treatment of patients with newly diagnosed metastatic hormone sensitive prostate cancer (mHSPC) in Belgium: a real world data analysis.

INTRODUCTION: Abiraterone acetate + prednisone (AAP) and docetaxel have proven their efficacy in the treatment of patients with newly diagnosed metastatic hormone-sensitive prostate cancer (mHSPC) in clinical trials. However, real-world data are scarce. The goal of this study is to evaluate real-world data on the efficacy and safety of these therapies in mHSPC patients. PATIENTS AND METHODS: Records of 93 patients from 21 different centres were retrospectively reviewed. Primary and secondary endpoints were radiographic and PSA progression-free survival (RPFS - PSA-PFS) and cancer specific and overall survival (CSS - OS), respectively. Adverse events (AEs) were evaluated according to the Common Terminology Criteria for Adverse Events version 5.0. Differences in oncological outcome and AEs were evaluated between three treatment groups: ADT only (N=26) - ADT + AAP (N=48) - ADT + docetaxel (N=19). Survival analysis was performed using Kaplan-Meier statistics. RESULTS: Median RPFS was 13 months (95% confidence interval [CI]: 9-17) for ADT only, 21 months (95% CI: 19-23) for ADT + AAP and 12 months (95% CI: 11-14) for ADT + docetaxel (p = 0.004). The 1-year PSA-PFS, CSS and OS were 73.5%, 90.7% and 88.7%, respectively, with no significant differences between the three groups. Adverse events of grade 3 or higher were not observed more frequently. CONCLUSION: Retrospective real-world data show a significantly longer RPFS for mHSPC patients treated with ADT + AAP compared to ADT only or ADT + docetaxel at short-term follow-up. This can aid in counselling of mHSPC patients in daily clinical practice.

Cancer and renal insufficiency results of the BIRMA study.

BACKGROUND: half of anticancer drugs are predominantly excreted in urine. Dosage adjustment in renal insufficiency (RI) is, therefore, a crucial issue. Moreover, patients with abnormal renal function are at high risk for drug-induced nephrotoxicity. The Belgian Renal Insufficiency and Anticancer Medications (BIRMA) study investigated the prevalence of RI in cancer patients, and the profile/dosing of anticancer drugs prescribed. METHODS: primary end point: to estimate the prevalence of abnormal glomerular filtration rate (GFR; estimated with the abbreviated Modification of Diet in Renal Disease formula) and RI in cancer patient. Secondary end point: to describe the profile of anticancer drugs prescribed (dose reduction/nephrotoxicity). Data were collected for patients presenting at one of the seven Belgian BIRMA centres in March 2006. RESULTS: a total of 1218 patients were included. The prevalence of elevated SCR (> or =1.2 mg per 100 ml) was 14.9%, but 64.0% had a GFR<90 ml min(-1) per 1.73 m(2). In all, 78.6% of treated patients (n=1087) were receiving at least one drug needing dosage adjustment and 78.1% received at least one nephrotoxic drug. In all, 56.5% of RI patients receiving chemotherapy requiring dose reduction in case of RI did not receive dose adjustment. CONCLUSIONS: the RI is highly frequent in cancer patients. In all, 80% of the patients receive potentially nephrotoxic drugs and/or for which dosage must be adjusted in RI. Oncologists should check the appropriate dose of chemotherapeutic drugs in relation to renal function before prescribing.

Isolation of flagellated bacteria implicated in Crohn's disease.

BACKGROUND: Serologic expression cloning has identified flagellins of the intestinal microbiota as immunodominant antigens in experimental colitis in mice and in individuals with Crohn's disease (CD). The present study was done to identify the microbial source of such flagellins. METHODS: Using a variety of isolation and culture approaches, a number of previously unknown flagellated bacteria were isolated. Based on 16S ribosomal DNA sequences, these bacteria fall into the family Lachnospiraceae of the phylum Firmicutes. RESULTS: Serum IgG from patients with CD and from mice with colitis reacted to the flagellins of these bacteria, and only their flagellins, whereas serum IgG from controls did not. The sequence of these flagellins demonstrate conserved amino- and carboxy-terminal domains that cluster phylogenetically and have a predicted 3D structure similar to Salmonella fliC, including an intact TLR5 binding site. The flagellin of 1 of these bacteria was likely O-glycosylated. CONCLUSIONS: The conserved immune response in both mouse and human to these previously unknown flagellins of the microbiota indicate that they play an important role in host-microbe interactions in the intestine.

Newly recognized GnRH receptors: function and relative role.

Hypothalamic gonadotropin releasing hormone (GnRH I) and its pituitary receptor are responsible for the CNS regulation of reproduction. However, a second GnRH (GnRH II) is also expressed in humans and a gene that resembles the GnRH II receptor in fish has been identified in humans and monkeys. The amino-acid sequence of this newly identified, seven-transmembrane, G-protein-coupled receptor in monkeys differs from the human GnRH I receptor by having a C-terminal, cytoplasmic tail. GnRH II is approximately 400-fold more potent at GnRH II receptors than GnRH I receptors. GnRH I directly inhibits proliferation of human tumor cells, and GnRH II and its receptor might have a similar role. Limited progress has been made, however, because of difficulty translating the mRNA that encodes the human GnRH II receptor. Nevertheless, such receptors are likely to exist in humans because GnRH II is more inhibitory to tumor cell replication than GnRH I, and GnRH I and GnRH II have reciprocal effects on human decidual stromal cells in culture. The focus of this review is the identity of a possible translatable, functional GnRH II receptor in humans. The two possibilities considered are either that GnRH II receptor mRNA is expressed that encodes either 5 or 7 transmembrane domains or that a GnRH II-responsive complex is formed by the GnRH I receptor and fragments derived from the GnRH II receptor.

High efficiency method for gene transfer in normal pituitary gonadotropes: adenoviral-mediated expression of G protein-coupled receptor kinase 2 suppresses luteinizing hormone secretion.

The level of LH secretion is determined by both alterations in gonadotrope responsiveness and alterations in GnRH secretion. The molecular mechanisms underlying gonadotrope responsiveness are unknown, but may include G protein-coupled receptor kinases (GRKs). Typically, GRKs phosphorylate the intracellular regions of seven-transmembrane receptors permitting beta-arrestin to bind, which prevents receptor activation of its G protein. Previously, we reported that heterologous expression of GRK2, -3, and -6 in GnRH receptor-expressing COS cells by complementary DNA transfection suppressed GnRH-stimulated inositol trisphosphate production, and that coexpression of GRK2 and beta-arrestin-2 was more inhibitory than either expressed alone. Here, we have investigated the effect of GRK2 on GnRH-stimulated LH secretion using adenovirus-mediated gene transfer in normal pituitary gonadotropes. Pituitary cells were infected with adeno-GRK2 or adeno-beta-galactosidase constructs at a multiplicity of infection of 60 (number of viral particles per cell). Seventy-two hours later, GRK2 expression was measured by enzyme-linked immunosorbent assay, and GnRH-stimulated LH secretion (10(-7) M GnRH-A for 90 min) was assayed by RIA. Adeno-beta-galactosidase infected 96-99% of the cells based on X-Gal staining. Uninfected and adeno-beta-galactosidase-infected cells exhibited endogenous GRK immunoreactivity of about 0.5 (OD405), and LH secretion of 14.8-17.7 ng/ml. Adeno-GRK2-infected cells showed a GRK2 immunoreactivity of about 2.5 (OD405) and LH secretion of 2.5 ng/ml. Therefore, adeno-GRK2 infection resulted in a 5-fold increase in the GRK2 OD405 value, which was accompanied by an 80-85% decrease in GnRH-stimulated LH secretion. GnRH-stimulated inositol trisphosphate production by gonadotropes also was inhibited, suggesting a site of action for GRK2 at phospholipase Cbeta or earlier in the signal transduction pathway. The significance of these findings is 2-fold: 1) adenoviral-mediated gene transfer permits investigation of the regulatory role of gene products in the cell of interest, the gonadotrope, rather than in heterologous cell systems; and 2) additional, stronger evidence is provided that supports a role for GRKs in setting the responsiveness of GnRH receptor signaling.

Potential regulatory roles for G protein-coupled receptor kinases and beta-arrestins in gonadotropin-releasing hormone receptor signaling.

GnRH stimulates gonadotropin secretion, which desensitizes unless the releasing hormone is secreted or administered in a pulsatile fashion. The mechanism of desensitization is unknown, but as the GnRH receptor is G protein coupled, it might involve G protein-coupled receptor kinases (GRKs). Such kinases phosphorylate the intracellular regions of seven-transmembrane receptors, permitting beta-arrestin to bind, which prevents the receptor from activating G proteins. Here, we tested the effect of GRKs and beta-arrestins on GnRH-induced inositol trisphosphate (IP3) production in COS cells transfected with the GnRH receptor complementary DNA. GRK2, -3, and -6 overexpression inhibited IP3 production by 50-75% during the 30 sec of GnRH treatment. Coexpression of GRK2 and beta-arrestin-2 suppressed GnRH-induced IP3 production more than that of either alone. Immunocytochemical staining of rat anterior pituitary revealed that all cells expressed GRK2, -3, and -6; all cells also expressed the beta-arrestins. Western blots on cytosolic extracts of rat pituitaries revealed the presence of GRK2/3 and beta-arrestin-1 and -2. The expression of GRKs and beta-arrestins by gonadotropes and their inhibition of GnRH-stimulated IP3 production in COS-1 cells expressing the GnRH receptor suggest a potential regulatory role for the GRK/beta arrestin paradigm in GnRH receptor signaling.

Identification by polymerase chain reaction of the G protein-coupled receptor kinases expressed in the mouse gonadotropic alpha T3-1 cell line.

G protein-coupled receptor kinases (GRK 1-6) stimulate short-term desensitization (< 5 min) by phosphorylating G-protein coupled receptors, and also participate in receptor sequestration, which may relate to intermediate-term desensitization (30-60 min). The existence of such kinases and hence a potential role for them in gonadotrope/GnRH receptor desensitization was investigated using the PCR to identify GRKs in messenger RNA (mRNA) from the mouse alpha T3-1 gonadotrope cell line. The 150-bp complementary DNAs amplified by PCR from the kinase catalytic domain were cloned and sequenced. Seventeen of 42 clones were receptor kinases based on high nucleotide identities of 85-100% and amino acid identities of 97-100% with rat GRK2 and 3, and with human GRK6. Among the eight GRK3 clones was one differing from rat GRK3 by a single nucleotide and seven differing by six; no amino acid difference resulted from the nucleotide differences. Of the five GRK2 clones, one sequence was identical with rat GRK2, but four sequences differed by three nucleotides and one amino acid. Among four GRK6 sequences, one showed 15 nucleotide differences from human GRK6 (with no amino acid differences), and three had 16 nucleotide and one amino acid differences. For each of the three GRKs found, the most closely related isoform is assumed to be the mouse homolog of rat GRK2 and GRK3, and human GRK6, whereas the others are assumed to be previously undescribed isoforms or subtypes of GRK2, 3, and 6. Immunocytochemical staining using antibodies to GRK2, 3, and 6 confirmed their presence in alpha T3-1 cells. The function of these GRKs in alpha T3-1 cells is unknown, but they may be involved in short-term desensitization of the gonadotrope/GnRH receptor or perhaps, more likely, the sequestration of this receptor during intermediate-term desensitization.

Potential role for a regulator of G protein signaling (RGS3) in gonadotropin-releasing hormone (GnRH) stimulated desensitization.

The cellular and molecular mechanisms of gonadotrope desensitization are unknown but transduction of the GnRH signal is known to involve sequentially the GnRH receptor, Gq alpha protein, phospholipase C beta-1, inositol-1,4,5-trisphosphate (IP3), and intracellular Ca+2 release. Here, we report the results of studies of a new family of proteins known as regulators of G protein signaling (RGS) that recently have been implicated in desensitization of several ligand induced processes. Using DNA-mediated transfection, we co-expressed the GnRH receptor and RGS1,2,3, or 4 in COS-1 cells. Control cells and those expressing RGS1,2, and 4 produced five fold increases in IP3 levels during the 30 sec after treatment with GnRH. In contrast, RGS3 expression suppressed by 75% the GnRH-induced IP3 responses. RGS3 was shown to bind Gq alpha protein in a model in vitro system: recombinant RGS3-glutathione-S-transferase (GST) fusion protein bound five-fold more 35S-met labeled Gq alpha protein than did with GST alone, suggesting that the mechanism of RGS3 action is attenuation of Gq alpha protein activation of phospholipase C. RGS3 mRNA and protein were observed to be expressed endogenously in the gonadotropic alpha T3-1 cell line. These results suggest a potential role for RGS3 in modulating the LH secretory responsiveness of the pituitary gonadotrope to GnRH.

A regulator of G protein signaling, RGS3, inhibits gonadotropin-releasing hormone (GnRH)-stimulated luteinizing hormone (LH) secretion.

BACKGROUND: Luteinizing hormone secreted by the anterior pituitary gland regulates gonadal function. Luteinizing hormone secretion is regulated both by alterations in gonadotrope responsiveness to hypothalamic gonadotropin releasing hormone and by alterations in gonadotropin releasing hormone secretion. The mechanisms that determine gonadotrope responsiveness are unknown but may involve regulators of G protein signaling (RGSs). These proteins act by antagonizing or abbreviating interaction of Galpha proteins with effectors such as phospholipase Cbeta. Previously, we reported that gonadotropin releasing hormone-stimulated second messenger inositol trisphosphate production was inhibited when RGS3 and gonadotropin releasing hormone receptor cDNAs were co-transfected into the COS cell line. Here, we present evidence for RGS3 inhibition of gonadotropin releasing hormone-induced luteinizing hormone secretion from cultured rat pituitary cells. RESULTS: A truncated version of RGS3 (RGS3T = RGS3 314-519) inhibited gonadotropin releasing hormone-stimulated inositol trisphosphate production more potently than did RSG3 in gonadotropin releasing hormone receptor-bearing COS cells. An RSG3/glutathione-S-transferase fusion protein bound more 35S-Gqalpha than any other member of the G protein family tested. Adenoviral-mediated RGS3 gene transfer in pituitary gonadotropes inhibited gonadotropin releasing hormone-stimulated luteinizing hormone secretion in a dose-related fashion. Adeno-RGS3 also inhibited gonadotropin releasing hormone stimulated 3H-inositol phosphate accumulation, consistent with a molecular site of action at the Gqalpha protein. CONCLUSIONS: RGS3 inhibits gonadotropin releasing hormone-stimulated second messenger production (inositol trisphosphate) as well as luteinizing hormone secretion from rat pituitary gonadotropes apparently by binding and suppressing the transduction properties of Gqalpha protein function. A version of RGS3 that is amino-terminally truncated is even more potent than intact RGS3 at inhibiting gonadotropin releasing hormone-stimulated inositol trisphosphate production.

LH-RH agonists offer very good protection against the adverse gynaecological effects induced by tamoxifen.

This study was initiated to evaluate the efficacy of luteinizing hormone-releasing hormone (LH-RH) agonists in protecting premenopausal patients against the adverse gynaecological effects induced by tamoxifen. Between January 1998 and January 2000, 85 premenopausal breast cancer patients were included in this prospective study. All were to receive LH-RH agonists and tamoxifen for a minimum of two years. All patients underwent a pretreatment gynaecological evaluation and annual follow-up. Bone density was also measured at the start of treatment and then after 2, 3 and 4 years. Pretreatment evaluation revealed 2 polyps. At one and two years of follow-up, no abnormal symptoms were noted and echographic findings were normal. At three years of follow-up, a polyp associated with adnexal masses was discovered. Histology revealed ovarian and endometrial metastases of infiltrating lobular breast carcinoma. Bone density evaluation after 2, 3 and 4 years of treatment showed no significant bone loss. LH-RH agonists offer safe protection against the gynaecological side-effects of tamoxifen in premenopausal breast cancer patients.

Epitope-tagged gonadotropin-releasing hormone receptors heterologously-expressed in mammalian (COS-1) and insect (Sf9) cells.

The molecular cloning and nucleotide sequencing of the gonadotropin-releasing hormone (GnRH) receptor represented an enhanced step in the experimental effort to understand this key molecule in the reproductive process at a cell and molecular level. A subsequent step in this broad effort is heterologous expression of the receptor in model cell systems for studies of signal transduction and desensitization, processes that may require immunologic detection of the receptor. Therefore, the GnRH receptor was tagged at its N-terminus using recombinant DNA procedures with the HA-1 epitope that is bound by a monoclonal antibody (12CA5). COS-1 cells expressing this receptor bound [(125)I]D-Ala6-desGly10-GnRH ethylamide (GnRH-A) with the expected high affinity (IC(50) = 0.47 nM), and were immunocytochemically stained by the 12CA5 antibody. Signal transduction was demonstrated by GnRH-induced [(3)H]inositol phosphate accumulation in receptor-expressing COS-1 cells. Western blotting of COS-1 cell membranes expressing the receptor revealed protein bands at 67, 57, and 32 kDa. Immunoprecipitation occurred when the solubilized receptor from COS-1 cell membranes was reacted with 12CA5 antibody and anti-mouse IgG Sepharose, and the presence of the receptor demonstrated either by its binding of [(125)I]GnRH-A or by its detection on Western blots. Desensitization of inositol 1,4,5-trisphosphate (IP(3)) production by N-epitope-tagged GnRH receptor expressing COS-1 cells was evoked by a five min GnRH pretreatment; [(32)P]i labeling of such cells during desensitization followed by immunoprecipitation of the N-epitope-tagged receptor was not associated with receptor phosphorylation. Finally, the epitope tagged receptor was expressed in the high-yield baculovirus/insect Sf9 cell system: the membrane receptor bound [(125)I]GnRH-A with slightly lowered affinity (IC(50) = 1.4 nM), and in Western blots yielded protein bands of 32, 56/57, 69, and 120/140 kDa. The development and validation of these heterologous systems will permit the study of several GnRH receptor-mediated processes that are poorly understood.

Dual intracellular pathways in gonadotropin releasing hormone (GNRH) induced desensitization of luteinizing hormone (LH) secretion.

The mechanisms of GnRH-induced desensitization of LH secretion are poorly understood. Protein kinase C (PKC) and protein kinase A (PKA) desensitize some receptors of the 7-membrane type, and the GnRH receptor has consensus phosphorylation sites for PKC in the first and third intracellular loops, and a site for PKA in the first intracellular loop. In the first set of experiments we determined whether synthetic peptides representing the three intracellular loops of the receptor could be phosphorylated in vitro by purified PKC and PKA. As compared with a model substrate peptide for PKC, the third intracellular loop was phosphorylated 74% and the first intracellular loop 21%; PKA-phosphorylated the first intracellular loop peptide 17% as well as a model peptide substrate. In the second set of experiments, we used phorbol 12-myristate 13 acetate (PMA), an established PKC stimulator, and cholera toxin (CTX), established to activate the Gs protein and presumed to activate PKA, to treat cultured rat pituitary cells followed by LH measurements. Treatment with both drugs severely impaired GnRH-stimulated LH secretion whereas neither drug alone reduced LH secretion. Dibutyryl cAMP did not duplicate the effects of cholera toxin suggesting that the CTX action could not be explained by an increase in cAMP. These results suggest that more than one intracellular signaling pathway requires activation in order to induce desensitization; one pathway involves PKC and the other involves a pathway stimulated by cholera toxin, presumably Gs protein, which does not involve PKA.

Sequence comparisons of the variable VP2 region of eight infectious bursal disease virus isolates.

The VP2 gene is part of the genomic segment A of infectious bursal disease virus (IBDV). It has been identified as the major host-protective antigen of IBDV and is known to contain conformationally dependent protective epitopes. A 643-base pair segment covering the hypervariable region of this gene from three recent serologic variant IBDV isolates from the southeastern United States, two variants from the Delmarva Peninsula, and three serologic standard viruses were amplified and sequenced using the reverse transcription polymerase chain reaction and cycle sequencing techniques. This was done to determine the molecular similarity among isolates that differ antigenically and pathologically. Sequence analysis suggested that the Arkansas (Ark) and Mississippi (Miss) isolates evolved closely and separately from the Delmarva variants (GLS and DELE), in contrast to the other southeastern variant Georgia (Ga), which is more closely related (98.32%) to Delaware E (DELE). All variants, except for Miss, underwent a shift in amino acid number 222 from proline to threonine. The sequence of Univax BD virus, a commercially available intermediate vaccine, was markedly different, evolving from a separate lineage than the others. Restriction enzyme sites could differentiate most isolates. Except for Miss, variants do not have EcoRII site at the larger hydrophilic domain. All variants lost their HaeIII, StuI, and StyI cutting sites with a change in base number 856. The TaqI site is in DELE, whereas the SpeI site is absent in the standard vaccine viruses. The SWASASGS heptapeptide is conserved in all virulent viruses, including APHIS, but not in the attenuated (Univax BD and Bursa Vac 3) and published (D78 and PBG98) vaccines.