Characterization of a new member of the TNF family expressed on antigen presenting cells

Molecular structure, expression, and function analysis of BAFF gene in Chinese sucker, Myxocyprinus asiaticus

B cell activating factor (BAFF), belonging to the tumor necrosis factor superfamily (TNFSF), is a critical cytokine for B cell survival and immunoglobulin secretion. Here, the BAFF gene of Chinese sucker (Myxocyprinus asiaticus) (MaBAFF) was cloned using RT-PCR and RACE (rapid amplification of cDNA end) techniques. The open reading frame (ORF) of MaBAFF encodes a 272-amino acid protein containing a transmembrane domain, a TNF family signature, and a putative furin protease cleavage site as seen in BAFFs from other species. Tissue expression profiles of MaBAFF determined by absolute and relative quantification of real-time quantitative PCR (qPCR) showed that MaBAFF is widely distributed in various tissues, with the highest expression in spleen. MaBAFF can be detected during fertilized egg period by RT-PCR. Upon induction by A. hydrophila, the expression of MaBAFF was up-regulated in spleen from 48 to 72 h, and the expression of BAFF and IgM all reached a peak at 48 h in head kidney. The soluble BAFF gene (MasBAFF) had been cloned into pET30a. SDS-PAGE and Western blotting analysis confirmed that the His-MasBAFF was efficiently expressed in Escherichia coli Rosset (DE3). CCK-8 assay indicated that the MasBAFF recombinant protein (200 ng/ml) could prolong the survival of peripheral blood leukocytes. Based on ELISA screening and Western blotting, monoclonal antibody 1-F2A3 against recombinant MasBAFF was selected and used for immunohistochemistry, which showed that BAFF-positive cells were detected in spleen and head kidney. Our results raise the possibility that MaBAFF may be useful to enhance immune efficacy in Chinese sucker disease defense.

Elevated expression of BAFF receptor, BR3, on monocytes correlates with B cell activation and clinical features of patients with primary Sjögren's syndrome

BACKGROUND

We reported that the production of BAFF (B cell-activating factor) and IL-6, both of which are involved in survival and differentiation of B cells, is dysregulated in monocytes of patients with primary Sjögren's syndrome (pSS). In this study, we investigate the relationship between possible aberrations of pSS monocytes and clinical features of pSS patients and the contribution of monocytes to B cell activation, a mechanism involved in the pathogenesis of pSS.

METHODS

Expression of BAFF-receptor (BR3) on peripheral monocytes from patients with pSS (n = 67) and healthy controls (HC: n = 37) was analyzed by FACS. Peripheral monocytes were stimulated with BAFF, and IL-6 production by the cells was measured by ELISA. Peripheral B cells were cultured with BAFF-stimulated monocytes in the presence or absence of anti-IL-6 receptor antibody, and IgG production by the cells was measured by ELISA. Patients' serological data were collected from their clinical records. Patients' disease activity was quantified based on their EULAR Sjögren's syndrome disease activity index (ESSDAI) scores.

RESULTS

The proportion of peripheral BR3-positive monocytes (BR3⁺/CD14⁺) was significantly increased in pSS patients compared to HC. Moreover, IL-6 production by BAFF-stimulated monocytes was remarkably higher than HC and was significantly correlated with BR3⁺/CD14⁺ ratios of patients. In addition, BR3 expression on pSS monocytes was elevated in anti-Ro/SSA and/or anti-La/SSB positive compared to negative patients. Remarkably, BR3 expression on peripheral monocytes was positively and significantly correlated with patients' serum IgG and IgM levels and ESSDAI scores. Moreover, the amount of IgG produced by B cells was markedly higher in pSS patients compared to HC when the cells were co-cultured with BAFF-stimulated autologous monocytes in vitro. Notably, addition of anti-IL-6 receptor antibody into the co-culture system led to inhibition of IgG production by B cells.

CONCLUSIONS

Our data suggest that elevated BR3 expression in monocytes is associated with clinical features in pSS patients and that enhanced production of IL-6 by BAFF-stimulated monocytes plays a part in the overproduction of IgG by B cells in pSS. These results suggest that BAFF signaling pathways through BR3 in monocytes are possible therapeutic targets for pSS.

Molecular structure, expression, and bioactivity of B-cell-activating factor of the TNF family (BAFF) and its receptor BAFF-R in cats (Felis catus)

B-cell survival depends on signals induced by binding of B-cell activating factor (BAFF) to its receptor (BAFF-R). In this study, the full-length cDNAs of cat BAFF (cBAFF) and BAFF-R (cBAFF-R) were amplified from the spleen by reverse transcription PCR. The open reading frame of cBAFF cDNA encodes a protein of 285 amino acids containing a predicted transmembrane domain and a furin protease cleavage site, similar to mammalian, avian, and reptile BAFFs. The cBAFF-R gene encodes a 189 amino acid protein. Real-time quantitative PCR analyses revealed that the two genes are predominantly expressed in the spleen. csBAFF, EGFP/csBAFF, and cBAFF-R were efficiently expressed in Escherichia coli BL21 (DE3), as confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting analyses. After purification, the EGFP/csBAFF fusion protein showed a fluorescence spectrum similar to that of EGFP. Confocal laser scanning microscopy showed that EGFP/csBAFF bound to its receptor. In vitro, csBAFF promoted the survival of cat and mouse splenic B cells with/without a priming agent (Staphylococcus aureus Cowan 1, SAC) or anti-mouse IgM. Furthermore, it stimulated the survival of mouse B cells, similar to msBAFF. Recombinant cBAFF-R blocked the function of sBAFF in vitro. These findings indicate that csBAFF plays an important role in the survival of cat B cells and has functional cross reactivity between cats and other mammals, and suggest a role for the BAFF-BAFF-R system in regulating B-cell survival. Therefore, BAFF and BAFF-R show promise for enhancing the immune systems of animals.

A therapeutic role for BLyS antagonists

B lymphocytestimulator (BLyS) is a vital B cell survivalfactor. Overexpressionof BLyS in mice may lead to systemic lupus erythematosus (SLE)-like disease, and treatment of bona fide SLE mice with BLyS antagonists ameliorates disease progression and enhances survival. BLyS overexpression is common in human SLE, and results from a phase I clinical trial with a BLyS antagonistin human SLE have shown the antagonist to be biologicallyactive and safe. These features collectivelypoint to BLyS as an attractive therapeutic target in human disease.

Expression of BAFF and BR3 in patients with systemic lupus erythematosus

The objective of this study was to examine the relationship between the expression of B cell activating factor (BAFF) and BAFF receptor in patients with disease activity of systemic lupus erythematosus (SLE). Real-time RT-PCR was used to examine BAFF mRNA expression in peripheral blood monocytes of active and stable SLE patients and healthy controls. The percentage of BAFF receptor 3 (BR3) on B lymphocytes was measured by flow cytometry. Soluble BAFF levels in serum were assayed by ELISA. Microalbumin levels were assayed by an automatic immune analysis machine. BAFF mRNA and soluble BAFF levels were highest in the active SLE group, followed by the stable SLE group, and controls (P<0.01). The percentage of BR3 on B lymphocytes was downregulated in the active SLE group compared with the stable SLE group and controls (P<0.01). BAFF mRNA levels and soluble BAFF levels were higher in patients who were positive for proteinuria than in those who were negative (P<0.01). The percentage of BR3 on B lymphocytes was lower in patients who were positive for proteinuria than in those who were negative (P<0.01). The BAFF/BR3 axis may be over-activated in SLE patients. BAFF and BR3 levels may be useful parameters for evaluating treatment.

Molecular characterization and expression analysis of B cell activating factor from rock bream (Oplegnathus fasciatus)

B cell activating factor (BAFF) is a member of the tumor necrosis factor (TNF) ligand family. BAFF has been shown to induce survival and proliferation of lymphocytes. We characterized the gene encoding BAFF (RbBAFF) in rock bream (Oplegnathus fasciatus), and attempted to determine its biological functions upon immune responses. In silico analysis of RbBAFF demonstrated the presence of common TNF ligand family features, including a TNF domain, a D-E loop, and three cysteine residues that are crucial for trimer formation. Amino acid sequence alignment confirmed that RbBAFF and its homologs were conserved at secondary and tertiary levels. Transcriptional analysis indicated that RbBAFF mRNAs were ubiquitously expressed in wide array of tissues. The higher levels of constitutive expression were observed in the kidney, head kidney and spleen, suggesting an important physiological relationship with lymphocytes. Under pathological conditions, RbBAFF mRNA levels were significantly elevated. The role of RbBAFF in lymphocyte survival and proliferation was confirmed by MTT assays and flow cytometry. Recombinant RbBAFF protein (10 μg/mL) was able to prolong the survival and/or enhance the proliferation of rock bream lymphocytes by approximately 30%. Transcription of IL-10 and NFκB-1 was significantly stimulated by RbBAFF. Our findings provide further information regarding fish BAFF gene and its role in adaptive immunity.

CsBAFF, a Teleost B Cell Activating Factor, Promotes Pathogen-Induced Innate Immunity and Vaccine-Induced Adaptive Immunity

B cell activating factor (BAFF) is a member of the tumor necrosis factor family that is known to play an important role in B cell activation, proliferation, and differentiation in mammals. However, studies of BAFF in teleosts are very limited and its function, in particular that under in vivo conditions, is essentially unknown. In this study, we conducted in vivo as well as in vitro functional analyses of a BAFF homologue (CsBAFF) from the teleost fish tongue sole (Cynoglossus semilaevis). CsBAFF is composed of 261 residues and shares moderate sequence identities with known BAFFs of other teleosts. CsBAFF expression was most abundant in immune organs and was upregulated during bacterial infection. Purified recombinant CsBAFF (rCsBAFF) bound to tongue sole lymphocytes and promoted cellular proliferation and survival. The results of an in vivo study showed that CsBAFF overexpression in tongue sole significantly enhanced macrophage activation and reduced bacterial infection in fish tissues, whereas knockdown of CsBAFF expression resulted in increased bacterial dissemination and colonization in fish tissues. Furthermore, vaccination studies showed that CsBAFF enhanced the immunoprotection of a DNA vaccine and augmented the production of specific serum antibodies. Taken together, these results provide the first in vivo evidence to indicate that teleost BAFF is an immunostimulator that significantly contributes to the innate antibacterial immune response and vaccine-induced adaptive immune response.

Comparative genomic of the BAFF and BAFF-like genes and immune response to bacteria of miiuy croaker (Miichthys miiuy)

As a member of the tumor necrosis factor (TNF) family, B cell activating factor (BAFF), also known as TNF ligand superfamily member 13B (TNF13B), playing a critical role in enhancing immune responses. BAFF is a central cytokine for B-cell survival, proliferation, maturation and immunoglobulin secretion. In the present study, we describe the identification of the miiuy croaker BAFF (designed MmBAFF) and BAFF-like (designed MmBAFF-like) genes. The cDNA of MmBAFF contains an open reading frame (ORF) of 795 nucleotides that are translated into a predicted 264 amino acids. The ORF of MmBAFF-like consists of 705 bases encoding 234 amino acids. Amino acid sequence comparison indicated that MmBAFF and MmBAFF-like possessed the TNF signatures, a predicted transmembrane domain, three conserved cysteine residues and a putative furin protease cleavage site, which were the typical characteristics of TNF gene in mammals and birds. The predicted three-dimensional (3D) structure of the MmBAFF and MmBAFF-like monomer analyzed by comparative protein modeling revealed that they were very similar to human counterpart. Comparative genomic analysis revealed that the locations of MmBAFF and MmBAFF-like genes are conserved among the bony fish. Phylogenetic analysis shows the MmBAFF is most closely related to other teleost BAFFs with the highest similarity to Epinephelus awoara. And BAFF-like cluster get together first to BAFF cluster than three closely related TNF superfamily (TNFSF) members. Real-time quantitative PCR analysis shows the MmBAFF and MmBAFF-like transcripts are expressed in a wide range of tissues with the highest expression in skin and lymphoid tissue spleen. Upon induction by Vibrio anguillarum, their expressions are significantly upregulated in liver, spleen and kidney as compared to phosphate-buffered saline injected control fish. The association of increased BAFF expression after bacterial infection suggests that it plays a potentially important role in immune system of fish.

Hinokitiol inhibits cell growth through induction of S-phase arrest and apoptosis in human colon cancer cells and suppresses tumor growth in a mouse xenograft experiment

Hinokitiol (1), a tropolone-related natural compound, induces apoptosis and has anti-inflammatory, antioxidant, and antitumor activities. In this study, the inhibitory effects of 1 were investigated on human colon cancer cell growth and tumor formation of xenograft mice. HCT-116 and SW-620 cells derived from human colon cancers were found to be similarly susceptible to 1, with IC50 values of 4.5 and 4.4 μM, respectively. Compound 1 induced S-phase arrest in the cell cycle progression and decreased the expression levels of cyclin A, cyclin E, and Cdk2. Conversely, 1 increased the expression of p21, a Cdk inhibitor. Compound 1 decreased Bcl-2 expression and increased the expression of Bax, and cleaved caspase-9 and -3. The effect of 1 on tumor formation when administered orally was evaluated in male BALB/c-nude mice implanted intradermally separately with HCT-116 and SW-620 cells. Tumor volumes and tumor weights in the mice treated with 1 (100 mg/kg) were decreased in both cases. These results suggest that the suppression of tumor formation by compound 1 in human colon cancer may occur through cell cycle arrest and apoptosis.

Characterization of the molecular structure, expression and bioactivity of the TNFSF13B (BAFF) gene of the South African clawed frog, Xenopus laevis

B cell activating factor (BAFF), a member of the tumor necrosis factor family, is critical to B cell survival, proliferation, maturation, and immunoglobulin secretion and to T cell activation. In the present study, the full-length cDNA of BAFF from the South African clawed frog (Xenopus laevis, designated xlBAFF) was cloned using rapid amplification of cDNA ends (RACE) techniques and RT-PCR. The full-length cDNA of xlBAFF consists of 1204 bases including an open reading frame (ORF) of 801 nucleotides that are translated into a predicted 266 amino acid protein. Sequence comparison indicated that the amino acids of xlBAFF possessed the TNF signature, including a transmembrane domain, a putative furin protease cleavage site and three cysteine residues. The predicted three-dimensional (3D) structure of the xlBAFF monomer revealed that it was very similar to its counterparts. Real-time quantitative PCR analysis revealed that xlBAFF could be detected in various tissues and predominantly expressed in the spleen and other lymphoid tissue. The soluble xlBAFF had been cloned into a pET28a vector to express the recombinant protein. The His6-xlBAFF was efficiently expressed in Escherichia coli. BL21 (DE3) and its expressions were confirmed by SDS-PAGE and Western blotting analysis. After purification, laser scanning confocal microscopy analysis showed that xlBAFF could bind to its receptors on B cells. CCK-8 assays revealed that xlBAFF is not only able to promote survival/proliferation of South African clawed frog lymphocytes but also able to stimulate survival/proliferation of mouse B cells. These results will allow for further investigation the use of X. laevis as an in vivo model for related studies.

Pharmacokinetics and pharmacodynamics of anti-BR3 monoclonal antibody in mice

PURPOSE

To characterize the pharmacokinetic (PK) and pharmacodynamic (PD) properties of a monoclonal antibody directed against the B-cell activating factor (BAFF) receptor 3 (BR3), following intravenous (IV) and subcutaneous (SC) administration in mice.

METHODS

Single IV doses of 0.2, 2.0 and 20 mg/kg and a single SC injection of 20 mg/kg of anti-BR3 antibody was administered to mice. Serum drug and BAFF concentrations and splenic B-cell concentrations were measured at various time points. Pooled PK profiles were described by a two-compartmental model with time-dependent nonlinear elimination, and BAFF profiles were defined by an indirect response model. Fractional receptor occupancy served as the driving function for a competitive reversible antagonism model to characterize B-cell dynamics.

RESULTS

Noncompartmental analysis revealed a decrease in drug clearance (31.3 to 7.93 mL/day/kg) with increasing IV doses. The SC dose exhibited slow absorption (T(max) = 2 days) and complete bioavailability. All doses resulted in a dose-dependent increase in BAFF concentrations and decrease in B-cell counts. The proposed model reasonably captured complex PK/PD profiles of anti-BR3 antibody after IV and SC administration.

CONCLUSIONS

A mechanistic model was developed that describes the reversible competition between anti-BR3 antibody and BAFF for BR3 receptors and its influence on B-cell pharmacodynamics.

Characterisation and expression analysis of B-cell activating factor (BAFF) in spiny dogfish (Squalus acanthias): cartilaginous fish BAFF has a unique extra exon that may impact receptor binding

B-cell activating factor (BAFF), also known as tumour necrosis factor (TNF) ligand superfamily member 13B, is an important immune regulator with critical roles in B-cell survival, proliferation, differentiation and immunoglobulin secretion. A BAFF gene has been cloned from spiny dogfish (Squalus acanthias) and its expression studied. The dogfish BAFF encodes for an anchored type-II transmembrane protein of 288 aa with a putative furin protease cleavage site and TNF family signature as seen in BAFFs from other species. The identity of dogfish BAFF has also been confirmed by conserved cysteine residues, and phylogenetic tree analysis. The dogfish BAFF gene has an extra exon not seen in teleost fish, birds and mammals that encodes for 29 aa and may impact on receptor binding. The dogfish BAFF is highly expressed in immune tissues, such as spleen, and is up-regulated by PWM in peripheral blood leucocytes, suggesting a potentially important role in the immune system.

The discovery and development of belimumab: the anti-BLyS-lupus connection

For the first time in more than 50 years, the US Food and Drug Administration has approved a drug specifically for the treatment of systemic lupus erythematosus (SLE). This drug, belimumab (Benlysta), is a human monoclonal antibody that neutralizes the B-cell survival factor, B-lymphocyte stimulator (BLyS). The approval of belimumab combined a pioneering approach to genomics-based gene discovery, an astute appreciation of translational medicine, a disciplined clinical strategy, a willingness to take calculated risks, a devoted cadre of patients and physicians and a healthy dose of serendipity. Collectively, these efforts have provided a model for the development of a new generation of drugs to treat the broad manifestations of SLE. However, as a substantial percentage of SLE patients do not respond to belimumab, further research is needed to better characterize the pathogenetic mechanisms of SLE, identify additional therapeutic targets, and develop effective and nontoxic novel agents against these targets.

Biodistribution, pharmacokinetics, and nuclear imaging studies of 111In-labeled rGel/BLyS fusion toxin in SCID mice bearing B cell lymphoma

PURPOSE

We examined the biodistribution and pharmacokinetics of (111)In-labeled rGel/BLyS, a gelonin toxin (rGel)-B lymphocyte stimulator (BLyS) fusion protein.

MATERIALS AND METHODS

rGel/BLyS was labeled with In-111 through DTPA with a labeling efficiency >95%. Biodistribution/imaging studies were obtained in severe-combined immunodeficiency mice bearing diffuse large B cell lymphoma OCI-Ly10. Pharmacokinetic studies were performed in BALB/c mice.

RESULTS

In vitro, DTPA-conjugated rGel/BLyS displayed selective cytotoxicity against OCI-Ly10 cells and mantle cell lymphoma JeKo cells. In vivo, rGel/BLyS exhibited a tri-exponential disposition with a rapid initial mean distribution followed by an extensive mean distribution and a long terminal elimination phase. At 48 h after injection, uptake of the radiotracer in tumors was 1.25 %ID/g, with a tumor-to-blood ratio of 13. Tumors were clearly visualized at 24-72 h post-injection. Micro-SPECT-CT images and ex vivo analyses confirmed the accumulation of rGel/BLyS in OCI-Ly10 tumors.

CONCLUSIONS

(111)In-DTPA-rGel/BLyS are distributed to B cell tumors and induce apoptosis in tumors. Preclinical antitumor studies using rGel/BLyS should use a twice-per-week treatment schedule.

Regulatory mechanisms for the production of BAFF and IL-6 are impaired in monocytes of patients of primary Sjögren's syndrome

INTRODUCTION

In this study, we investigated possible aberrations of monocytes from patients with primary Sjögren's syndrome (pSS). We focused on B-cell-activating factor of the TNF family (BAFF) and IL-6 because they are both produced by monocytes and are known to be involved in the pathogenesis of pSS.

METHODS

Peripheral monocytes were prepared from both pSS patients and normal individuals. The cells were stimulated in vitro with IFN-γ, and the amounts of IL-6 and soluble BAFF (sBAFF) produced by the cells were quantitated. The effect of sBAFF itself on the production of IL-6 was also studied. To investigate the response of pSS monocytes to these stimuli, the expression levels of the genes encoding BAFF receptors and IL-6-regulating transcription factors were quantitated.

RESULTS

Peripheral pSS monocytes produced significantly higher amounts of sBAFF and IL-6 than normal monocytes did, even in the absence of stimulation. The production of these cytokines was significantly increased upon stimulation with IFN-γ. The elevated production of IL-6 was significantly suppressed by an anti-BAFF antibody. In addition, stimulation of pSS monocytes with sBAFF induced a significant increase in IL-6 production. Moreover, the expression levels of a BAFF receptor and transcription factors regulating IL-6 were significantly elevated in pSS monocytes compared to normal monocytes.

CONCLUSIONS

The results of the present study suggest that the mechanisms underlying the production of sBAFF and IL-6 are impaired in pSS monocytes. Our research implies that this impairment is due to abnormally overexpressed IL-6-regulating transcription factors and a BAFF receptor. These abnormalities may cause the development of pSS.

BAFF promotes Th17 cells and aggravates experimental autoimmune encephalomyelitis

Background

BAFF, in addition to promoting B cell survival and differentiation, may affect T cells. The objective of this study was to determine the effect of BAFF on Th17 cell generation and its ramifications for the Th17 cell-driven disease, EAE.

Methodology/Principal Findings

Th17 cells were increased in BAFF-Tg B6 (B6.BTg) mice and decreased in B6.Baff^−/− mice. Th17 cells in B6.Baff^−/− mice bearing a BAFF Tg (B6.Baff^−/−.BTg mice) were identical to those in B6.BTg mice, indicating that membrane BAFF is dispensable for Th17 cell generation as long as soluble BAFF is plentiful. In T + non-T cell criss-cross co-cultures, Th17 cell generation was greatest in cultures containing B6.BTg T cells and lowest in cultures containing B6.Baff^−/− T cells, regardless of the source of non-T cells. In cultures containing only T cells, Th17 cell generation followed an identical pattern. CD4⁺ cell expression of CD126 (IL-6R α chain) was increased in B6.BTg mice and decreased in B6.Baff^−/− mice, and activation of STAT3 following stimulation with IL-6 + TGF-β was also greatest in B6.BTg cells and lowest in B6.Baff^−/− cells. EAE was clinically and pathologically most severe in B6.BTg mice and least severe in B6.Baff^−/− mice and correlated with MOG_35–55 peptide-induced Th17 cell responses.

Conclusions/Significance

Collectively, these findings document a contribution of BAFF to pathogenic Th17 cell responses and suggest that BAFF antagonism may be efficacious in Th17 cell-driven 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).

Expressions of BAFF/BAFF receptors and their correlation with disease activity in Chinese SLE patients

B-cell activating factor belonging to tumour necrosis factor family (BAFF) is essential for B-cell survival and function through interaction with its receptors BAFF receptor 3 (BR3), B-cell maturation antigen (BCMA) and/or transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI), though BCMA and/or TACI can also bind to a proliferation-inducing ligand (APRIL). We evaluate the correlation of the expressions of these ligands/receptors with different clinical manifestations of systemic lupus erythematosus (SLE). Levels of BAFF and APRIL in plasma from 73 SLE patients were determined by enzyme-linked immunosorbent assay. Expressions of BR3, TACI and BCMA on CD19+ B cells were detected by flow cytometry. Clinical data were collected and disease activity was evaluated using SLEDAI-2000. SLE patients had elevated BAFF and APRIL levels in their plasma. BAFF levels correlated positively with SLEDAI while negatively with the BR3 protein expression on CD19+ B cells (p < .05). The detected BR3 protein expression in SLE patients was reduced on CD19+IgD+CD27-, CD19+IgD+CD27+ as well as CD19+IgD-CD27+ B cells compared to the counterparts of healthy controls (p < .001), whereas SLE patients did not differ from healthy controls in BR3 mRNA levels. In untreated new-onset patients, the expression rate of BR3 on CD19+ B cells correlated negatively with SLEDAI (p < .05). Elevation of BAFF and reduction of BR3 on CD19+ B cells were more obvious in those with lupus nephritis (LN, p < .05). TACI expression on CD19+ B cells was up-regulated only in those subjects with LN (p < .05). Elevated plasma BAFF and reduced BR3 protein expression on peripheral B cells could act as biomarkers for active disease in SLE patients. High expression of TACI may indicate the occurrence of LN.

B-Lymphocyte stimulator: a new biomarker for multiple myeloma

Multiple myeloma (MM) is a common malignant tumor, characterized by unlimited proliferation of abnormal plasmocytes in bone marrow. Considering the biological function of B-Lymphocyte stimulator (BLyS) and its receptors in B cell, we examined BLyS and its receptors expression in MM cells. Our studies confirmed that BLyS and its receptors are expressed in MM cells, including KM3, CZ-1, and primary MM cells, playing an important role in the survival and proliferation of MM cells. Additionally, we provide evidence that BLyS protein is located in the MM cell plasma membrane. We also found that IFN-gamma and IL-6 can induce BLyS expression on MM cells, while after the treatment of BAY11-7082, an IkB-alpha phosphorylation inhibitor, IFN-gamma induced up regulation of BLyS was completely inhibited, suggesting that nuclear factor kappaB (NF-kappaB) might be involved in the mechanism of the regulation of BLyS levels in response to cytokines. Finally, linear correlation analysis of the Lactate Dehydrogenase concentration and beta 2-microglobulin level with BLyS, and expressions of BLyS mRNA in MM patients revealed a significant correlation between them (P < 0.01 in all case), showing that BLyS could be a biomarker for the diagnosis and treatment of MM.

Global T cell dysregulation in non-autoimmune-prone mice promotes rapid development of BAFF-independent, systemic lupus erythematosus-like autoimmunity

In otherwise non-autoimmune-prone C57BL/6 (B6) mice rendered genetically deficient in CD152 (CTLA-4), polyclonal hypergammaglobulinemia with increased levels of systemic lupus erythematosus (SLE)-associated IgG autoantibodies, glomerular IgG and C3 deposition, and interstitial nephritis all developed by 3-5 wk of age. Remarkably, superimposing genetic deficiency of BAFF (B cell-activating factor belonging to the TNF family) onto CD152 deficiency did not substantially attenuate humoral autoimmunity and immunopathology in these mice, despite the resulting marked reduction in B-lineage cells. Although superimposing a BAFF transgene (resulting in constitutive BAFF overexpression) onto CD152-deficient mice did lead to increases in B-lineage cells and serum levels of certain SLE-associated IgG autoantibodies, renal immunopathology remained largely unaffected. Taken together, these results demonstrate that global T cell dysregulation, even in an otherwise non-autoimmune-prone host, can promote systemic humoral autoimmunity and immunopathology in a BAFF-independent manner. Moreover, supraphysiologic expression of BAFF in the setting of ongoing autoimmunity does not necessarily lead to greater immunopathology. These findings may help explain the limited clinical efficacy appreciated to date of BAFF antagonists in human SLE.

Neutralizing human anti-B-cell-activating factor of the TNF family (BAFF) scFv selected from phage antibody library

Elevated levels of B-cell-activating factor of the TNF family (BAFF) have been implicated in the pathogenesis of autoimmune diseases in human. We now report the isolation by phage display of human single-chain antibody fragment (scFv) anti-BAFF. After four rounds of panning against BAFF, thirty-two out of 92 phage clones displayed BAFF binding activity. One of the positive clones, designated F8, bound to BAFF with relatively high affinity and neutralized BAFF bioactivity in vitro. F8 clone was expressed in soluble form in Escherichia coli HB2151 and purified by immobilized metal affinity chromatography (IMAC). The purified scFv recognized BAFF with the affinity constant (K(aff)) of 2.5 x 10(7)M(-1) without cross-reaction to APRIL. In addition to binding, the purified scFv could does-dependently inhibit BAFF-induced mouse spleen B lymphocyte proliferation. Together with its fully human mature, F8 scFv may have therapeutic implications in therapy of autoimmune disorders mediated by BAFF.

Expression, purification, and characterization of recombinant human soluble BAFF secreted from the yeast Pichia pastoris

The B lymphocyte stimulator (BAFF) is a novel member of the tumor necrosis factor (TNF) ligand family which is important in B lymphocyte maturation and survival. Herein, the cDNA coding for the extracellular domain of the BAFF (hsBAFF) has been cloned into the secreting expression organism Pichia pastoris. SDS-PAGE and Western blotting assays of culture broth from a methanol-induced expression strain demonstrated that recombinant hsBAFF, a 20.2 kDa glycosylated protein, was secreted into the culture medium. The recombinant protein was purified to greater than 95% using DEAE-Sepharose ion exchange and Superdex 75 size-exclusion chromatography steps. Finally, 102 mg of the protein was obtained in high purity from 1 L of the supernatant and its identity to hsBAFF was confirmed by NH(2)-terminal amino acid sequence analysis Bioactivity of the recombinant hsBAFF was confirmed by the ability of the protein to stimulate human B lymphocyte proliferation in vitro. Our results suggest that the P. pastoris expression system can be used to produce large quantities of fully functional hsBAFF for both research and industrial purpose.

The expression of BAFF-binding receptors is not altered in multiple sclerosis or myasthenia gravis

Multiple sclerosis (MS) is a chronic, progressive disease of the central nervous system (CNS) characterized by consistent myelin injury. Antibody-mediated death of oligodendrocytes is a pathological feature in a subset of MS patients and may be of relevance to disease pathogenesis. In myasthenia gravis (MG), acetylcholine receptors (AChR) situated at the neuromuscular endplate are destroyed by autoreactive antibodies. B-cell activating factor of the tumour necrosis factor (TNF) superfamily (BAFF) is essential for B-cell survival. Using flow cytometry, we evaluated the expression of three BAFF-binding receptors, namely, BAFF-receptor (BAFF-R), B-cell maturation antigen (BCMA), and transmembrane activator and calcium modulating and cyclophilin ligand interactor (TACI) in peripheral-blood lymphocytes. Nearly all CD19(+) B cells and CD19(+)CD27(+) memory B cells expressed BAFF-R. The intensity of BAFF-R expression was not statistically different in MS or MG compared with healthy controls. Very few T cells expressed BAFF-R. BCMA expression was strictly limited to B cells. Although both B and T cells expressed TACI, levels were much higher on B cells compared with levels on T cells. The percentages of B and T cells expressing BCMA and TACI did not differ significantly in MS or MG versus controls. We conclude that the expression of BAFF-binding receptors is not appreciably altered in MS or MG.

Cloning, expression and bioactivity of duck BAFF

B cell activating factor (BAFF) belonging to the TNF family is critical for B cell survival and maturation. In the present study, we identified a duck BAFF cDNA, named dBAFF, by RT-PCR and RACE strategies. The open reading frame (ORF) of this cDNA encodes a 288-amino acid protein containing a predicted transmembrane domain and a putative furin protease cleavage site like chicken BAFF (cBAFF), human BAFF (hBAFF) and mouse BAFF (mBAFF). The amino acid identity between biologically soluble dBAFF and cBAFF, hBAFF or mBAFF is 97, 78 and 71%, respectively. RT-PCR analysis showed the dBAFF gene is strongly expressed in the bursa of fabricius. Recombinant soluble dBAFF (dsBAFF) fused with NusA.tag was efficiently produced in Origami B (DE3) pLysS expression host strain. In vitro, purified dsBAFF was not only able to promote survival of bursa B cells, but also able to co-stimulate proliferation of mammalian B cells with anti-IgM. Furthermore, recombinant hsBAFF has a positive effect on duck bursa B cells survival. These findings indicate dBAFF plays an important role in survival and proliferation of duck B cells and because of its high conservation in the evolution, functional cross-reactivity exists between mammalian and duck BAFF.

sBAFF mutants induce neutralizing antibodies against BAFF

B cell activating factor belonging to the TNF family (BAFF) is a novel member of the tumor necrosis factor (TNF) ligand family and plays an important role in B lymphocyte maturation and survival. Overexpression of BAFF is closely involved in the pathogenesis and progression of many kinds of autoimmune disorders; therefore, BAFF has been considered as an ideal therapeutic target for these conditions. In this study, we generated several candidate immune inhibitors of human BAFF by conjugating foreign immunodominant T-helper cell (Th) epitopes to the N- or C-terminus of five BAFF mutants. The recombined proteins were successfully expressed in Escherichia coli (E. coli) and purified by Ni-NTA chromatography. BALB/c mice immunized with the recombinant proteins produced high levels of anti-BAFF antibodies, and their sera inhibited the lymphocyte proliferation-inducing activity of recombinant soluble BAFF and natural soluble BAFF. Moreover, antibodies cross-reactive with BAFF were detected in sera from hu-SCID mice immunized with the recombinant proteins. These results indicated that the recombinant BAFF mutants modified with Th epitopes could induce neutralizing antibodies against BAFF in vivo. This study may provide a valuable strategy for treating BAFF-associated autoimmune diseases.

Targeting BAFF: Immunomodulation for autoimmune diseases and lymphomas

In an effort to develop more effective treatments for inflammatory diseases, immunologists have targeted numerous molecular pathways, but with limited success. Notable exceptions are anti-TNF agents, which have proved efficacious in a proportion of rheumatoid arthritis (RA) patients. Another TNF family member, termed BAFF ("B cell-activating factor belonging to the TNF family"), plays a central role in autoimmune diseases, as well as in B cell maturation, survival, and T cell activation. Agents that block BAFF have proven to be highly effective in the treatment of certain autoimmune conditions in mice. In addition, phase II data in human clinical trials for RA appear very promising. BAFF is also a survival factor for certain B cell lymphomas. Despite the relatively recent identification of BAFF, this molecule has provided considerable new insight into B cell homeostasis and immune function, and represents an important new molecular target for treatment of autoimmune diseases and lymphomas.

Correlation of the expression levels of BLyS and its receptors mRNA in patients with systemic lupus erythematosus

OBJECTIVES

To measure the levels of B-lymphocyte stimulator (BLyS) and its receptors mRNA expression in peripheral blood mononuclear cells (PBMCs) using quantitative real-time polymerase chain reaction (PCR) method and to investigate the relationship between BLyS and its receptors mRNA expression and systemic lupus erythematosus (SLE).

DESIGN AND METHODS

Specific primers and TaqMan probe were designed, and real-time PCR was performed. According to the standard curve of plasmids DNA, the levels of BLyS and its receptors mRNA expression in 37 patients with SLE and 30 healthy subjects were determined. The ratio of the expression levels of BLyS mRNA to that of beta2-microglobulin (beta2M) mRNA and the ratio of the expression levels of BLyS receptors mRNA to that of beta2M mRNA were regarded as indicator for the levels of BLyS and its receptors mRNA expression.

RESULTS

The expression of BLyS, TACI and BAFF-R mRNA in PBMCs from patients with SLE was significantly elevated compared to healthy controls (P<0.001 for each), and active patients with SLE group had higher mRNA expression than patients with SLE inactive group (P<0.001 for each). The patients with elevated anti-double-stranded DNA (anti-dsDNA) antibody titers had enhanced BLyS, TACI and BAFF-R mRNA expression (P<0.05 for BLyS; and P<0.01 for TACI and BAFF-R).

CONCLUSION

The BLyS, TACI and BAFF-R mRNA expression levels were significantly elevated in patients with SLE, which suggests that BLyS, TACI and BAFF-R might be involved in the pathogenesis, and that mRNA expression levels might serve as a biomarker of disease activity.

Paucity of clinical disease despite serological autoimmunity and kidney pathology in lupus-prone New Zealand mixed 2328 mice deficient in BAFF

Constitutive overexpression of B cell-activating factor belonging to the TNF family (BAFF) promotes development of systemic lupus erythematosus (SLE), and treatment of SLE mice with BAFF antagonists ameliorates disease. To determine whether SLE can develop de novo in BAFF-deficient hosts, BAFF-deficient New Zealand Mixed (NZM) 2328 (NZM.Baff(-/-)) mice were generated. In NZM.Baff(-/-) mice, spleen B cells (including CD5(+) B1a and CD5(-) B1b B cells), germinal centers, Ig-secreting cells, and T cells were reduced in comparison to NZM.Baff(+/+) mice. Serum total Ig and autoantibody levels were reduced at 4-6 mo but approached wild-type levels with increasing age, indicating that autoreactive B cells can survive and secrete autoantibodies despite the complete absence of BAFF. At least some of these autoantibodies are nephrophilic in that glomerular deposition of total IgG and IgG1 (but not of IgG2a, IgG2b, or C3) was substantial in NZM.Baff(-/-) mice by 12-13 mo of age. Despite proliferative glomerulonephritis, highlighted by widespread glomerular hyaline thrombi, being common among NZM.Baff(-/-) mice by 6-7 mo of age, severe proteinuria and mortality were greatly attenuated. These results demonstrate that the lifelong absence of BAFF does not protect NZM 2328 mice from serological autoimmunity and renal pathology. Nevertheless, the character of the renal pathology is altered, and the mice are largely spared from clinically overt disease (severe proteinuria and premature death). These observations may have profound ramifications for the use of BAFF antagonists in human SLE and related diseases.

Expression and purification of a soluble B lymphocyte stimulator mutant modified with the T-helper cell epitope

The DNA encoding soluble B lymphocyte stimulator (134-285 amino acids, sBLyS) mutant with residues 217-224 replaced by two glycines (named msBLyS) was constructed. The sequence encoding a foreign immunodominant T-helper epitope from ovalbumin (OVA) was then coupled to the 5'-end of msBLyS cDNA. After being sequenced, the recombinant DNA was ligated into the prokaryotic expression vector pQE-80L. The recombinant protein was produced in E. coli DH5alpha after induction with IPTG with the yield of more than 40% of total bacterial protein. The recombinant protein was purified with Ni-NTA chromatography and Sepharcryl S200 chromatography to a purity of more than 98%. The BALB/c mice, immunized with the recombinant protein, produced anti-BLyS antibodies at a high level, which indicated that the recombinant BLyS mutant modified with T-helper epitope elicited polyclonal antibodies with cross-reactivity with BLyS in vivo. This recombinant protein may therefore be used as immune inhibitor of BLyS for treating BLyS -associated autoimmune diseases.

Construction and characterization of a bi-functional EGFP/sBAFF fusion protein

A fusion between gene encoding fluoresce-enhanced green fluorescent protein variant (EGFP) and soluble domain of human B-cell-activating factor of the TNF family (sBAFF) was constructed and expressed in Escherichia coli. The EGFP/sBAFF had an apparent molecular weight of 45 kDa and was detected with anti-hsBAFF and anti-His(6) monoclonal antibodies. After being purified by immobilized metal affinity chromatography (IMAC), the fusion protein retained similar fluorescence spectra to those of EGFP. Biological activity assays showed the EGFP/sBAFF as well as sBAFF could co-stimulated human B lymphocyte proliferation in vitro. In addition, EGFP/sBAFF has shown specific binding to BAFF receptors positive-cells and the stained cells could be analyzed with flow cytometry. Thus, the fusion protein represents a readily obtainable source of biologically active sBAFF that may prove useful in further studies on BAFF and its receptors.

Aberrant expression of BAFF in T cells of systemic lupus erythematosus, which is recapitulated by a human T cell line, Loucy

B cell-activating factor of the tumor necrosis factor (TNF) family, or BAFF, is mainly produced in monocytes and dendritic cells, and indispensable for proliferation, differentiation and survival of B cells. BAFF is a type II membrane-bound protein and the extracellular C-terminal fragment is released from the cells as soluble BAFF (sBAFF), which binds to specific receptors on B cells. Accumulating evidence suggests that BAFF plays an important role in the pathogenesis of autoimmune diseases, such as systemic lupus erythematosus (SLE). In this study, we developed a sensitive sandwich ELISA system to quantify the amount of sBAFF using our own mAb. Treatment of peripheral T cells of SLE patients with an anti-CD3 antibody triggered robust expression of BAFF and subsequent release of sBAFF from the cells. On the other hand, the stimulus induced only marginal elevation of sBAFF from normal T cells. These data indicate that BAFF is expressed in T cells upon stimulation at least under pathological conditions. Expression of BAFF was also largely induced in a human T cell line, Loucy (American Type Tissue Collection CRL-2629), in response to several stimuli, while other T cell lines so far examined produced the cytokine almost constitutively. These data suggest that Loucy recapitulates some of the characteristics of SLE T cells. Investigation of molecular and cellular mechanisms of production of BAFF in Loucy demonstrated that expression of BAFF was regulated through a signal transduction pathway which involves c-jun NH2-terminal kinase and p38, and that shedding of BAFF was catalyzed by a membrane-bound protease, furin.

Mutational analysis of human BLyS in patients with common variable immunodeficiency

BLyS, a TNF family member, is crucial for B cell proliferation and differentiation by acting through its three receptors, TACI, BCMA and BAFF-R. The knock out model for BLyS is characterized by an immunological phenotype reminiscent of the human phenotype of common variable immunodeficiency (CVID). CVID is characterized by a defective B cell compartment, evidencing the putative importance of BLyS in its pathogenesis. On the contrary, the transgenic model for BLys is characterized by autoimmune manifestations, underlying its role in B cell regulation. In fact, mutations in TACI, one of the three BLyS receptors, are associated with CVID. Based on these facts, we hypothesized that BLyS could be a candidate gene for CVID. We screened 78 patients with CVID using DHPLC and direct sequencing: No disease causing mutations were identified. A novel heterozygous single nucleotide polymorphism (SNP) was found in exon 1 of one individual, however this SNP (G189A) does not lead to an amino acid substitution.

B cell depletion therapy in systemic rheumatic diseases: different strokes for different folks?

Autoantibodies have, until recently, been the overriding focus of investigators of autoantibody-associated diseases. Increasing attention is now being paid to B cells, which not only are the producers of autoantibodies but also contribute to autoimmune disease via autoantibody-independent mechanisms. Therapeutic measures that target B cells for depletion are gaining in popularity. In this review, we will focus on two distinct approaches of depleting B cells; one employing a direct-kill approach by engagement of B cell surface CD20 with an anti-CD20 monoclonal antibody (rituximab), and the other employing an indirect starvation approach by neutralization of B lymphocyte stimulator (BLyS), a potent B cell survival factor. Among the systemic immune-based rheumatic disorders, we will focus on rheumatoid arthritis and systemic lupus erythematosus, two disorders for which therapeutic B cell targeting is being intensely investigated.

Apoptosis in autoimmune diabetes: the fate of beta-cells in the cleft between life and death

Cytokine-induced beta-cell death is the end-stage event in the pathogenesis of autoimmune diabetes. Beside cytokines, several pro-apoptotic pathways mediated through nitric oxide, reactive oxygen species, glucose and Fas ligation can be involved, suggesting that programmed cell death (PCD) is a critical aspect in this process. The apoptotic program is activated by the utilization of the Fas/Fas-ligand (FasL) axis in the interrelation of T and beta-cells. Evidence for this mechanism arose from the finding that beta-cells in NOD mice could be protected from apoptosis by blocking the Fas-FasL pathway. Glucose is a regulator of Fas expression on human beta-cells and elevated glucose levels may contribute to accelerated beta-cell destruction by constitutively expressed FasL independently of the autoimmune reaction. It can thus be concluded that immunological, as well as metabolic, pathways may act in concert to cause beta-cell destruction. Much experimental work has been carried out to manipulate beta-cells in transgenic mice expressing apoptosis modulators in islets. For example, the transcription factor, nuclear factor-kappaB (NF-kappaB), promotes the expression of several beta-cell genes, including pro- and anti-apoptotic genes. The prevention of cytokine-induced gene expression of several NF-kappaB targets, such as inducible nitric oxide synthase, Fas, and manganese superoxide dismutase can prevent beta-cell death. Thus, modulating the expression of apoptotic mediators may significantly affect the end-stage outcome of autoimmune diabetes and could thus be a potential avenue for clinical therapy, even though currently existing findings remain exploratory due to the restrictions of transgenic mouse models.

Development of a compact anti-BAFF antibody in Escherichia coli

Recombinant antibodies, especially single-chain antibody fragment (scFv), can be applied as detection reagents and even substitute for some reagents used in immunoassays. For scFv fragments, there is no such universal system available up to now. We have constructed vectors for the convenient, rapid expression of a novel compact antibody composed of anti-B-cell-activating factor of the TNF family (BAFF) scFv and the Fc portion (the hinge region, CH2, and CH3 domains) of the human IgG1 in Escherichia coli. After expression in bacteria as inclusion bodies, the recombinant antibody was purified and refolded in vitro. The scFv-Fc antibody was demonstrated to retain high binding affinity to antigen, including membrane-bound BAFF and soluble BAFF, and to possess some human IgG crystallizable fragment domain functions, such as human complement C1q and protein A binding. Both size-exclusion high-performance liquid chromatography column analysis and Western blotting of proteins subjected to nonreducing sodium dodecyl sulfate polyacrylamide gel electrophoresis suggested that scFv-Fc antibody is homodimeric with relative molecular mass of 110 kDa. These findings suggest that the compact antibody may be useful in diagnostic application for the prediction of BAFF relevant to autoimmune diseases in human.

Production and characterization of a bacterial single-chain antibody fragment specific to B-cell-activating factor of the TNF family

An active form of a single-chain antibody fragment (scFv) from the murine monoclonal antibody ABL-1, which is specific for B-cell-activating factor of the TNF family, was produced in Escherichia coli. The complementary DNAs encoding the variable regions of the heavy chain (VH) and light chain (VL) were connected by a (Gly4Ser)3 linker, using an assembly polymerase chain reaction. The construct VH-linker-VL was placed under the control of highly efficient T7 promoter system. The cloned scFv was expressed in E. coli BL21(DE3) as inclusion bodies. After extraction from the E. coli cells, the inclusion bodies were solubilized and denatured in the presence of 8M urea. The expressed scFv fusion proteins were purified by Ni(2+)-IDA His-bind resin and finally renatured by dialysis. The purity and activity of the purified scFv were confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blotting, and enzyme-linked immunosorbent assay. The result revealed that the ABL-1 scFv retains the specific binding activity to BAFF with an affinity constant of 0.9x10(-8)molL(-1).

Expression, refolding, and characterization of human soluble BAFF synthesized in Escherichia coli

The B lymphocyte stimulator (BAFF) is a novel member of the tumor necrosis factor (TNF) ligand family which is important in B lymphocyte maturation and survival. Here, a recombinant form of the extracellular domain of the BAFF (hsBAFF) was expressed in Escherichia coli BL21(DE3) under the control of a T7 promoter. The resulting insoluble bodies were separated from cellular debris by centrifugation and solubilized with 8 M urea. A rapid and simple on-column refolding procedure was developed. It was applied and then the refolded hsBAFF was purified by anion-exchange. The purified final product was >98% pure by SDS-PAGE stained with Coomassie brilliant blue R-250. Mass spectroscopic analysis indicated the protein to be 17.5 kDa, which equalled the theoretically expected mass. The N-terminal sequencing of refolding hsBAFF showed the sequence corresponded to the designed protein. The correct refolding of the recombinant protein was verified in the recovery of its secondary and tertiary structures as assessed by circular dichroism and fluorescence emission spectra. The renatured protein displayed its immunoreactivity with the antibodies to BAFF protein by Western blotting. The final purified material was biologically active in a validated induced human B lymphocyte proliferation bioassay. The expression and in vitro refolding of hsBAFF resulted in production of an active molecule in a yield of 15 mg/L flask cultivation.