BAFF/BAFF-R involved in antibodies production of rats with collagen-induced arthritis via PI3K-Akt-mTOR signaling and the regulation of paeoniflorin.

ETHNOPHARMACOLOGICAL RELEVANCE: Paeoniflorin (Pae) is extracted from the root of paeonia lactiflora which have attracted attention for anti-rheumatic and immune modulating properties. AIM OF THE STUDY: To investigate the role of PI3K/Akt/mTOR signaling mediated by BAFF/BAFF-R in antibodies production and the regulation of Pae on the signaling pathway in rats with collagen-induced arthritis (CIA). MATERIALS AND METHODS: CIA rats were randomly separated into different groups and treated with Pae (25, 100mg/kg) from day 18 to day 38 after immunization. The effects of Pae on B lymphocytes of CIA rats were evaluated by the levels of BAFF, anti-CII antibody, IgA, IgG and IgM, and the expressions of BAFF-R, PI3K, p-Akt and mTOR. RESULTS: In CIA rats, the levels of anti-CII antibody, IgA, IgG and IgM in serum enhanced, BAFF, BAFF-R, PI3K, p-Akt and mTOR were highly expressed. Pae (100mg/kg) obviously decreased arthritis score, relieved ankle and paw swelling, improved spleen histopathology in CIA rats, decreased the levels of IgA, IgM, IgG and anti-CII antibody, and significantly decreased the expressions of BAFF, BAFF-R, PI3K, p-Akt and mTOR. CONCLUSION: PI3K/Akt/mTOR signaling mediated by BAFF/BAFF-R participates in antibodies production by B lymphocytes of CIA rats. Pae had therapeutic effects on rats with CIA. These effects might be relative to regulating PI3K/Akt/mTOR signal mediated by BAFF/BAFF-R, and down regulate the antibodies production further.

Innate immune defects correlate with failure of antibody responses to H1N1/09 vaccine in HIV-infected patients.

BACKGROUND: Mechanisms underlying the failure of influenza vaccine-induced antibody responses in HIV-infected persons are poorly understood. OBJECTIVE: To investigate innate immune factors regulating B-cell function in HIV-infected persons and to correlate them with serologic responses to H1N1/09 vaccine. METHODS: We evaluated immunologic characteristics of 17 HIV-infected patients and 8 healthy controls (HCs) at 0, 7, and 28 days (designated T0, T1, and T2) following a single 15-µg dose of nonadjuvanted H1N1/09 influenza vaccine by using flow cytometry, ELISpot, and ELISA. All HCs and 9 patients (53%) seroconverted with >1:40 hemagglutination inhibition antibody titer at T2. RESULTS: In vaccine responders and HCs, serum levels of BAFF (B cell-activating factor) and APRIL (a proliferation-inducing ligand) increased from T0 to T2 in conjunction with increases in frequencies of memory B cells. Concurrently, receptors for these factors showed changes, with increases in expression of TACI (transmembrane activator and calcium modulator and cyclophilin ligand interactor) and decreases in BAFF receptor in memory B cells. IL-2 secreting cells and IgG antibody-secreting cells increased at T2 in vaccine responders and HCs in ex vivo H1N1 antigen-stimulated cultures. These immunologic responses were not evident at T1 and were deficient in vaccine nonresponder patients at T2. At T0, vaccine nonresponders had lower frequencies of BAFF receptor and TACI-expressing memory B cells than did responders. CONCLUSION: Impaired memory B-cell responses, deficiencies in serum BAFF and APRIL, and alterations in their receptors on B cells were associated with failure of H1N1/09 influenza vaccine responses among virologically controlled HIV-infected patients.

An increase in B cell apoptosis by interfering BAFF-BAFF-R interaction with small synthetic molecules.

B cell-activating factor (BAFF) transmitted signals through binding to specific BAFF receptors (BAFF-R) to regulate B cell survival and development. We used MTT assay to examine the cytotoxicity of chemicals, flow cytometry analysis to measure BAFF-BAFF-R interactions, and western blotting to detect BAFF protein. Here, we established screening method to find specific compounds to interfere with BAFF-BAFF-R interactions in WIL2-NS B lymphoblast cells. According to screening (imidazol-4-ylcarbonyl)guanidine or (oxazol-4-ylcarbonyl)guanidine derivatives, we selected KR32592, KR32673, KR33232, KR33341 and KR33426 as candidates to interfere with BAFF-BAFF-R interaction. No cytotoxicity was detected by KR32592, KR33232, and KR33426 at the concentration of 5 µM, and by KR32673, and KR33341 at the concentration of 0.5 µM. Cell population with BAFF-BAFF-R interactions was reduced by the pre-incubation of chemicals with human BAFF-murine CD8 (BAFF-muCD8). Cell population with BAFF-BAFF-R interactions was also decreased by pre-exposure of WIL2-NS cells to chemicals prior to the incubation with BAFF-muCD8. Chemicals also inhibited LPS-stimulated BAFF production from splenocytes. All these effects of chemicals may contribute to the inhibition of BAFF-mediated anti-apoptosis. These data demonstrate that chemicals interfering with BAFF-BAFF-R interaction may be screened with our experimental condition. It suggests that BAFF-BAFF-R interaction could be a chemical target to develop therapeutics for BAFF-mediated autoimmune diseases.

Enhanced immunogenicity of pneumococcal surface adhesin A (PsaA) in mice via fusion to recombinant human B lymphocyte stimulator (BLyS).

BACKGROUND: B lymphocyte stimulator (BLyS) is a member of the tumor necrosis factor superfamily of ligands that mediates its action through three known receptors. BLyS has been shown to enhance the production of antibodies against heterologous antigens when present at elevated concentrations, supporting an immunostimulatory role for BLyS in vivo. METHODS: We constructed a fusion protein consisting of human BLyS and Pneumococcal Surface Adhesin A (PsaA) and used this molecule to immunize mice. The immunostimulatory attributes mediated by BLyS in vivo were evaluated by characterizing immune responses directed against PsaA. RESULTS: The PsaA-BLyS fusion protein was able to act as a co-stimulant for murine spleen cell proliferation induced with F(ab')2 fragments of anti-IgM in vitro in a fashion similar to recombinant BLyS, and immunization of mice with the PsaA-BLyS fusion protein resulted in dramatically elevated serum antibodies specific for PsaA. Mice immunized with PsaA admixed with recombinant BLyS exhibited only modest elevations in PsaA-specific responses following two immunizations, while mice immunized twice with PsaA alone exhibited undetectable PsaA-specific serum antibody responses. Sera obtained from PsaA-BLyS immunized mice exhibited high titers of IgG1, IgG2a, IgG2b, and IgG3, but no IgA, while mice immunized with PsaA admixed with BLyS exhibited only elevated titers of IgG1 following two immunizations. Splenocytes from PsaA-BLyS immunized mice exhibited elevated levels of secretion of IL-2, IL-4 and IL-5, and a very modest but consistent elevation of IFN-γ following in vitro stimulation with PsaA. In contrast, mice immunized with either PsaA admixed with BLyS or PsaA alone exhibited modestly elevated to absent PsaA-specific recall responses for the same cytokines. Mice deficient for one of the three receptors for BLyS designated Transmembrane activator, calcium modulator, and cyclophilin ligand [CAML] interactor (TACI) exhibited attenuated PsaA-specific serum antibody responses following immunization with PsaA-BLyS relative to wild-type littermates. TACI-deficient mice also exhibited decreased responsiveness to a standard pneumococcal conjugate vaccine. CONCLUSION: This study identifies covalent attachment of BLyS as a highly effective adjuvant strategy that may yield improved vaccines. In addition, this is the first report demonstrating an unexpected role for TACI in the elicitation of antibodies by the PsaA-BLyS fusion protein. REVIEWERS: This article was reviewed by Jonathan Yewdell, Rachel Gerstein, and Michael Cancro (nominated by Andy Caton).

Therapeutic effects of TACI-Ig on rat with adjuvant arthritis.

Transmembrane activator and calcium modulator and cyclophilin ligand interactor-immunoglobulin (TACI-Ig) is a human fusion protein that binds and neutralizes both B lymphocyte stimulator (BLyS), a cytokine shown to be a key regulator of B cell maturation, proliferation and survival, and a proliferation-inducing ligand (APRIL). Rat adjuvant arthritis (AA) is an experimental animal model of rheumatoid arthritis (RA), which is mainly dependent on T cells and neutrophil-mediated cytokine production. The purpose of the present study was to investigate the effects of TACI-Ig on rat AA. Rat AA was induced by intradermal injection of 0·1 ml complete Freund's adjuvant (CFA). TACI-Ig (0·7, 2·1 and 6·3 mg/kg), recombinant human tumour necrosis factor-α receptor (rhTNFR) : Fc (2·8 mg/kg) and IgG-Fc (6·3 mg/kg) were administered subcutaneously every other day from days 16 to 34 after immunization. Arthritis was evaluated by arthritis global assessment and swollen joint count (SJC). The ankle joint and spleen were harvested for histopathological examination. Spleen index and thymus index were calculated. The levels of BLyS, interleukin (IL)-17, interferon (IFN)-γ, IgG1, IgG2a and IgM in AA rat spleen were measured by enzyme-linked immunosorbent assay. Administration of TACI-Ig significantly reduced the arthritis global assessment and SJC, decreased spleen index and ameliorated histopathological manifestations of rat AA. Suppressing the levels of BLyS, IL-17, IFN-γ and Ig in AA rat spleen were observed after administration of TACI-Ig. These results showed that TACI-Ig significantly inhibited the degree of rat AA, and the inhibitory effects might be associated with its ability to reduce BLyS, proinflammatory cytokines and Ig levels in spleen.

Developmental and peri-postnatal study in cynomolgus monkeys with belimumab, a monoclonal antibody directed against B-lymphocyte stimulator.

Belimumab is a fully human monoclonal antibody antagonist for soluble B-lymphocyte stimulator, and is a potential therapeutic for various autoimmune disorders. To support clinical use, belimumab was administered intravenously to pregnant cynomolgus monkeys every 2 weeks throughout gestation at dosages of 5 and 150 mg/kg. Fetuses were delivered by C-section on Gestation Day 150 from one-half of the mothers, and evaluated for teratologic effects (external, visceral, skeletal, and heart), pharmacodynamics (PD) and toxicokinetics (TK). Remaining mothers delivered their infants naturally, enabling extensive assessment of PD and TK during a 1-year postnatal period. Effects attributed to belimumab were limited to the expected pharmacology, primarily decreased numbers of B-lymphocytes in peripheral blood of mothers and infants, and in fetal lymphoid tissues. Infants demonstrated full recovery upon cessation of exposure. In conclusion, belimumab was well tolerated at pharmacologically active dose levels in pregnant cynomolgus monkeys and their infants after exposure throughout pregnancy.

Deficient TACI expression on B lymphocytes of newborn mice leads to defective Ig secretion in response to BAFF or APRIL.

Capsular polysaccharides of encapsulated bacteria do not induce immune response in newborns and the mechanism for this unresponsiveness is not clear. In adults, transmembrane activator and calcium-modulator and cyclophilin [corrected] ligand interactor (TACI) is a TNFR family member molecule with a pivotal role in Ab responses against polysaccharide vaccines. We investigated the expression and the functions of the TNF family cytokines, B cell-activating factor of the TNF family (BAFF) and a proliferation-inducing ligand (APRIL), and their receptors in newborn mice and found that TACI expression on B lymphocytes was dramatically reduced (p < 0.0001) in newborns as compared with adults. More importantly, TACI ligands BAFF or APRIL were unable to induce IgA/IgG/IgM secretion from newborn B lymphocytes. Additionally, TACI expression seems to be important in plasma cell development. Indeed, in contrast to adults, stimulation of newborn B lymphocytes with BAFF or APRIL did not result in up-regulation of CD138 expression. In vitro or in vivo exposure of newborn B lymphocytes to oligodeoxynucleotides (CpG ODN) led to up-regulation of TACI expression on newly formed, follicular, and marginal zone as well as B1 B lymphocyte populations, and rendered them responsive to BAFF- or APRIL-mediated CD138 expression and IgA/IgG secretion. Finally, immunization of newborn BALB/c mice but not TACI knockout mice with CpG ODN containing (4-hydroxy-3-nitrophenyl)acetyl-Ficoll led to development of IgG Abs against (4-hydroxy-3-nitrophenyl)acetyl. These findings demonstrate that low TACI expression may be a critical factor that determines the susceptibility of newborns to infections with encapsulated bacteria and the impaired immunogenicity of polysaccharide vaccines. Finally, CpG ODNs may correct deficient newborn response to polysaccharide vaccines by up-regulating TACI.

Emerging biological therapies in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a prototypic inflammatory autoimmune disorder characterized by multisystem involvement and fluctuating disease activity. Symptoms range from rather mild manifestations such as rash or arthritis to life-threatening end-organ manifestations such as glomerulonephritis or thrombosis. Virtually every organ system is subject to potential damage. Symptoms typically wax and wane over the course of the disease; yet unfortunately, many patients will experience a slow decline in their health because of the ongoing systemic inflammation. Effective treatment must be individualized and is often based on the specific manifestations that are seen in each patient. In a similar manner, prognosis is also dependent on the severity and the specific organ systems involved.