Cytokine release assays: current practices and future directions.

As a result of the CD28 superagonist biotherapeutic monoclonal antibody (TGN 1412) "cytokine storm" incident, cytokine release assays (CRA) have become hazard identification and prospective risk assessment tools for screening novel biotherapeutics directed against targets having a potential risk for eliciting adverse pro-inflammatory clinical infusion reactions. Different laboratories may have different strategies, assay formats, and approaches to the reporting, interpretation, and use of data for either decision making or risk assessment. Additionally, many independent contract research organizations (CROs), academic and government laboratories are involved in some aspect of CRA work. As a result, while some pharmaceutical companies are providing CRA data as part of the regulatory submissions when necessary, technical and regulatory practices are still evolving to provide data predictive of cytokine release in humans and that are relevant to safety. This manuscript provides an overview of different approaches employed by the pharmaceutical industry and CROs, for the use and application of CRA based upon a survey and post survey follow up conducted by ILSI-Health and Environmental Sciences Institute (HESI) Immunotoxicology Committee CRA Working Group. Also discussed is ongoing research in the academic sector, the regulatory environment, current limitations of the assays, and future directions and recommendations for cytokine release assays.

Heterogeneity and biased T cell receptor alpha/beta repertoire of mucosal CD8+ cells from murine large intestine: implications for functional state.

Up to 90% of CD8+ intraepithelial lymphocytes (IEL) of the murine large intestine (LI) belong to the alpha/beta T cell lineage and consist of two subsets. One subset expresses both alpha and beta subunits of the CD8 coreceptor, and is uniformly Thy1+, CD5+, B220-, CD2+, CD28+. The CD8 alpha+beta+ LI-IEL exclude self-reacting V beta structures, and readily proliferate in vivo in response to T cell receptor-mediated stimuli. The CD8 alpha+beta- subset of TCR-alpha/beta+ LI-IEL is Thy1-/+, CD5-, B220+, CD2+/-, and CD28-. It contains cells with potentially self-reacting V beta s and is responsive in vivo to high doses of anti-TCR-alpha/beta monoclonal antibody (mAb), but not to bacterial superantigens. Both subsets are abundant in LI-IEL of old nude mice, and CD8 alpha+beta+ LI-IEL in nude mice undergo the same V beta deletions as in euthymic mice of the same background. Both subsets express the intestinal T cell-specific integrin alpha M290 beta 7, known to be a homing receptor for IEL. Unusually high proportions of CD69+ cells within both subsets indicate chronic activation. The proportions of CD69+ and alpha M290 beta 7+ cells within the CD8 alpha+beta+ subset increase with age, probably due to constant antigenic challenge. We propose that CD8 alpha+beta+ and CD8 alpha+beta- subsets of LI-IEL permanently reside in LI and represent a lineage different from spleen and lymph node CD8+ T cells. The CD8 alpha+beta+ undergoes negative selection, and is responsive to TCR-mediated stimuli. The CD8 alpha+beta- subset of LI-IEL is a subject of distinct selection mechanisms, and has low responsiveness to TCR-mediated stimuli.

The immune response against Helicobacter pylori--a direct linkage to the development of gastroduodenal disease.

Helicobacter pylori infects about half of the world's population. H. pylori elicits marked immune responses, but the infection is commonly life-long. Some infected individuals remain asymptomatic, while others develop significant gastroduodenal disease. We review the underlying host immune response to H. pylori which programs for persistence and evolution of gastroduodenal disease.

Expression of IgA and IgM Fc receptors on murine T lymphocytes.

Fc receptors are induced on T cells following activation via the TCR. T cells that express Fc receptors transiently have the ability to use two different cognate systems: the TCR and immunoglobulins bound to the Fc receptors. The studies discussed in this article are focused on the Fc alpha and Fc mu receptors that can be induced on certain subsets of murine T lymphocytes. The article emphasizes the role of the T cell receptor for antigen in the expression of Fc alpha and Fc mu receptors on murine T cells and reviews experimental observations that suggest significant molecular heterogeneity of these Fc receptors. The finding that regulation of expression of Fc alpha receptors and Fc mu receptors on T lymphocytes is linked to cellular activation via the CD3/TCR complex implies that these Fc receptors might mediate important functions in the biology and pathology of T cells.

Interaction of heavy and light chains of myeloma immunoglobulin with pooled normal chains: quantitative analysis of association and restoration of idiotype.

We have analyzed in vitro recombinants between the isolated heavy (H) or light (L) chains of mouse myeloma protein MOPC-21 and L or H chains of normal mouse serum immunoglobulin (Ig). In the first series of experiments using fixed H chain and solubilized L chain, we have found out that only about 30% of normal L chain pool interact efficiently with individual H chain. Moreover, fractions with different affinity to H-MOPC-21 appeared to exist among normal L chains. In the second set of experiments recombination of H and L chains in solution was used. Examination of recombinants between myeloma H chain and normal L chains revealed a set representing 6% of L chain repertoire capable of forming MOPC-21-like idiotypic structure.

Allelic exclusion frequency analysis and molecular characteristics of immunoglobulins secreted by the hybridomas expressing both allelic genes.

The investigation of 750 B-lymphocyte hybridoma clones obtained by fusion of mouse myeloma and newborn heterozygous Igk-1a/Igk-1b rat splenocytes has revealed that 9.8% of Ig kappa-chain loci are rearranged productively. Seventeen hybridomas secrete kappa-chains of both allelic variants. The analysis of IgM molecules of 9 such clones demonstrated that in 6 cases only one L-chain allotype, either 1a or 1b, is present in IgM. Thus for the first time the high frequency of selective association of H and L chains in Ig-producing cells was shown. Evidently this selectivity may function as one of allelic exclusion mechanisms at the Ig assembly stage.

Appearance of neoantigen in mouse IgG1 upon reduction of interchain disulfide bridges: assessment of local and general conformational rearrangements using monoclonal antibody and small-angle X-ray scattering.

Mouse hybridoma antibody E5D2 reacting with murine mono- and polyclonal IgG1 has been produced. MonAb E5D2 recognizes the antigenic determinant (epitope) buried in intact IgG1 and expressed upon mild reduction of interchain S-S bridges. Neither H nor L chains alone maintain epitope E5D2. Reassociation of gamma 1 chains (H chains of IgG1) with L chains results in complete restoration of this antigenic determinant. The data strongly suggest that epitope E5D2 depends on the quaternary structure of IgG1. The epitope is also expressed by reduced F(ab)2 fragment of IgG1 but is not connected with its antigen binding site. The likely localization of the epitope E5D2 is the interface between CH and CL domains. The second produced monAb F6C2 reacts with CH1-CL region of reduced mouse IgG2. Small-angle X-ray scattering experiments have demonstrated pronounced decrease of the radius of gyration of reduced IgG1 as compared to the intact one. This indicates general conformational changes of IgG1 molecule following mild reduction of Fab region S-S groups. Epitope E5D2 is the first quaternary antigenic subclass specific determinant described for C the region of mouse IgG. Thus, serologic expression of epitope E5D2 reveals precise conformational perturbations of small area near reduced S-S bridges while small-angle scattering demonstrates accompanying general transformation of IgG structure.

T cell specialization at environmental interfaces: T cells from the lung and the female genital tract of lpr and gld mice differ from their splenic and lymph node counterparts.

Mice homozygous for lpr and gld accumulate CD4- CD8- (double-negative, DN) B220+ CD5loThy-1lo alpha beta T cells in the spleen and lymph nodes (LN), while mucosal gut T cells are normal. To study other mucosa-associated T cell populations, we examined T cell subsets separated according to expression of alpha beta T cell receptor, CD4, CD5, CD8, Thy-1 and B220 in the lung and the female genital tract (FGT) of adult MRL lpr, C3H lpr and C3H gld mice. alpha beta T cell accumulation was detected in both the FGT and the lungs of lpr and gld mice but, in contrast to the spleen and LN, equal proportions of DN B220+ and CD4+ of CD8+ (single-positive, SP) B220- T cells were observed in these sites, and the T cells had an increased expression of Thy-1 and CD5. Staining for CD44, L-selectin, and CD45RB revealed a higher percentage of effector/memory T cells in lpr and gld lungs and FGT compared to spleens and LN. CD69 expression suggested chronic activation of DN and SP T cells in lpr and gld lungs and FGT. Thus, we show that FGT and lung resident T cells are affected by lpr and gld mutations, but that their phenotypes are distinct from those of systemic T cells. These data suggest that T cells associated with FGT and lung mucosal tissues represent a separate lineage from systemic T cells, and/or that the abnormal T cells in lpr and gld mice are selected against in mucosal surfaces exposed to environmental antigen.

The roles of costimulation and Fas in T cell apoptosis and peripheral tolerance.

Using cells from TCR transgenic mice that do or do not express Fas, we show that there are two mechanistically distinct forms of apoptosis in CD4+ T cells. Naive T cells undergo apoptosis if cultured in the absence of antigen or costimulation. This form of programmed cell death (PCD) is not dependent on Fas, and is prevented by CD28-mediated signals, which lead to the secretion of growth factors and the expression of survival genes, such as bcl-xL. Recently activated T cells undergo apoptotic death upon repeated stimulation. This activation-induced cell death (AICD) is mediated by Fas, but is independent of costimulation and is not prevented by IL-2 or bcl-xL. Finally, we show that peripheral tolerance may be induced in vivo independent of Fas-mediated cell death.

Resident CD4+ alpha beta T cells of the murine female genital tract: a phenotypically distinct T cell lineage that rapidly proliferates in response to systemic T cell activation stimuli.

A population of CD4+ cells has been identified in the murine female genital tract (FGT). Phenotypic studies of FGT CD4+ cells demonstrate that they express CD3 and that the majority of these cells are alpha beta TCR+Thy-1+. Most of the Thy-1+CD4+alpha beta TCR+ cells resemble memory T cells based on their expression of CD44, L-selectin and CD45RB antigens. The vast majority of Thy-1+CD4+alpha beta TCR+ FGT cells are CD5+ and all of them are B220-. Systemic stimuli including infection with Trypanosoma brucei brucei, injection with anti-CD3 epsilon, or bacterial superantigens staphylococcal enterotoxin A or B cause a rapid accumulation of CD4+ cells in the FGT exceeding that observed for CD4+ cells in spleen and lymph nodes (LN). Expansion of the FGT CD4+ cells, which are phenotypically distinct from the splenic and LN CD4+ T cells, is due to local proliferation rather than an influx of cells from the circulation. The CD4+ population in the FGT of adult nu/nu mice is dramatically reduced, indicating its thymic dependency. In lpr/lpr mice, FGT CD4 cells do not display changes characteristic of splenic or LN CD4 cells in the same animals. These findings demonstrate that the CD4+ cells of the murine FGT are thymic dependent, but that they constitute a T cell lineage that phenotypically and, probably functionally, is distinct from other peripheral CD4+ T cell populations.

Helicobacter pylori infection in immunized mice lacking major histocompatibility complex class I and class II functions.

The role of major histocompatibility complex (MHC) class I- and class II-restricted functions in Helicobacter pylori infection and immunity upon oral immunization was examined in vivo. Experimental challenge with H. pylori SS1 resulted in significantly greater (P

Antigenic markers of V domain of mouse MOPC 21 IgG1 L chain. The conformational basis of VL domain markers and content of MOPC 21 VL-like immunoglobulins in sera of inbred mouse strains.

Antisera were raised in rabbits against L chains, isolated from mouse myeloma protein MOPC21 (gamma 1, chi V chi 15 group). Specific antibodies for the V and C domain of MOPC21 L chain were obtained by cross-immunoadsorption of the antisera. The pure anti-V and anti-C antibodies were fixed on diazocellulose and used as immunosorbents. The inhibitory capacity of L chin-monomers and dimers isolated from the L chain preparation was compared to that of intact IgG1 using binding inhibition of 125I-labeled IgG1 on the antibody-containing immunosorbents. It was established that changes of IgG1 quaternary structure influences the conformational state of the L chain V domain only. The inhibitory capacity of the V domain is 1000-fold lower in L monomers, if compared with native IgG1, and only 10-fold lower than in L dimers. The inhibiting capacity of the C domain, however, does not differ in L monomers and intact IgG1. Thus the conformational rigidity of the C domain co-exists with conformational flexibility of the V domain on the same polypeptide chain. We tried to estimate the content of MOPC21 V1-like normal IgG in mouse serum of 6 inbred strains using antibodies against the V1 domain. Data obtained by inhibition of radioimmunoadsorption, indicate that in C57BL/6 mice 0.08% of normal serum Ig carries a V1 region which is idiotypically related to the V1 of MOPC21. In serum Ig of BALB/c mice the percentage is 0.16.

CpG containing oligodeoxynucleotides are potent adjuvants for parenteral vaccination with the fusion (F) protein of respiratory syncytial virus (RSV).

The feasibility of using oligodeoxynucleotides (ODN) containing unmethylated CpG motifs as parenteral adjuvants for subunit vaccines against RSV was tested in BALB/c mice. Compared with immunization with natural F protein adsorbed to aluminum hydroxide (F/AlOH) adjuvant alone, coadministration of F/AlOH with CpG ODN resulted in statistically significant increases in serum neutralization titers, an enhanced generation of splenic antigen-dependent killer cell precursors, and accelerated clearance of infectious virus from lungs 4 days after challenge. The statistically significant increases in serum IFNgamma and anti-F protein IgG2a titers, and significantly diminished pulmonary IL-5 and eosinophilia after challenge indicated that CpG ODN enhanced the ability of F/AlOH to elicit type 1 immune responses. F protein-specific serum IgE titers were also reduced. Further analysis of pulmonary inflammatory cells demonstrated an expansion of CD8(+) T cells, relative to the CD4(+) T cell compartment. The potency of CpG ODN was not adversely affected in gene knockout mice devoid of the p35 chain of the IL-12 heterodimer. Taken together, the results suggest a novel formulation for naïve recipients of F protein-based subunit vaccines that does not result in a type 2 phenotype.

Effective mucosal immunization against respiratory syncytial virus using purified F protein and a genetically detoxified cholera holotoxin, CT-E29H.

We exploited the powerful adjuvant properties of cholera holotoxin (CT) to create a mucosally administered subunit vaccine against respiratory syncytial virus (RSV). A genetically detoxified mutant CT with an E to H substitution at amino acid 29 of the CT-A1 subunit (CT-E29H) was compared to wild type CT for toxicity and potential use as an intranasal (IN) adjuvant for the natural fusion (F) protein of RSV. When compared to CT the results demonstrated that: (1) CT-E29H binding to GM1 ganglioside was equivalent, (2) ADP-ribosylation of agmatine was 11.7%, and (3) toxicity was attenuated in both Y-1 adrenal (1.2%) and patent mouse gut weight assays. IN vaccination with F protein formulated with CT-E29H induced serum anti-CT and anti-F protein antibodies that were comparable to those obtained after vaccination with equivalent doses of CT. Vaccinations containing CT-E29H at doses of 0.1 microg were statistically equivalent to 1.0 microg in enhancing responses to F protein. Antigen-specific mucosal IgA and anti-RSV neutralizing antibodies were detected in nasal washes and sera, respectively, of mice that had received F protein and 0.1 or 1.0 microg of CT-E29H. Anti-F protein IgA was not detected in the nasal washes from mice IN vaccinated with 0.01 microg CT-E29H or IM with F protein adsorbed to AlOH adjuvant. In addition, the formulation of purified F protein and CT-E29H (0.1 and 1.0 microg) facilitated protection of both mouse lung and nose from live RSV challenge. Collectively, the data have important implications for vaccine strategies that use genetically detoxified mutant cholera holotoxins for the mucosal delivery of highly purified RSV antigens.