Immunogenicity Risk Assessment for PEGylated Therapeutics.

The objective of this manuscript is to provide the reader with two examples on how to present an immunogenicity risk assessment for a PEGylated therapeutic as part of Investigational New Drug (IND) application or during other stages of the drug development process. In order to provide context to the bioanalytical strategies used to support the PEGylated therapeutics presented here, a brief summary of information available for marketed PEGylated biologics is provided. Two case studies are presented, a PEGylated enzyme and a PEGylated growth factor. For the former, the risk assessment covers how to deal with a narrow therapeutic window and suggestions to utilize a PD marker as surrogate for neutralizing antibody assessments in Phase I. The latter has recommendations on additional analytes that should be monitored to mitigate risk of immunogenicity to endogenous counterparts.

Increased CD45RA+ FoxP3(low) regulatory T cells with impaired suppressive function in patients with systemic lupus erythematosus.

BACKGROUND: The role of naturally occurring regulatory T cells (Treg) in the control of the development of systemic lupus erythematosus (SLE) has not been well defined. Therefore, we dissect the phenotypically heterogeneous CD4(+)FoxP3(+) T cells into subpopulations during the dynamic SLE development. METHODLOGY/PRINCIPAL FINDINGS: To evaluate the proliferative and suppressive capacities of different CD4(+) T cell subgroups between active SLE patients and healthy donors, we employed CD45RA and CD25 as surface markers and carboxyfluorescein diacetatesuccinimidyl ester (CFSE) dilution assay. In addition, multiplex cytokines expression in active SLE patients was assessed using Luminex assay. Here, we showed a significant increase in the frequency of CD45RA(+)FoxP3(low) naive Treg cells (nTreg cells) and CD45RA(-)FoxP3(low) (non-Treg) cells in patients with active SLE. In active SLE patients, the increased proportions of CD45RA(+)FoxP3(low) nTreg cells were positively correlated with the disease based on SLE disease activity index (SLEDAI) and the status of serum anti-dsDNA antibodies. We found that the surface marker combination of CD25(+)CD45RA(+) can be used to defined CD45RA(+)FoxP3(low) nTreg cells for functional assays, wherein nTreg cells from active SLE patients demonstrated defective suppression function. A significant correlation was observed between inflammatory cytokines, such as IL-6, IL-12 and TNFα, and the frequency of nTreg cells. Furthermore, the CD45RA(+)FoxP3(low) nTreg cell subset increased when cultured with SLE serum compared to healthy donor serum, suggesting that the elevated inflammatory cytokines of SLE serum may promote nTreg cell proliferation/expansion. CONCLUSIONS/SIGNIFICANCE: Our results indicate that impaired numbers of functional CD45RA(+)FoxP3(low) naive Treg cell and CD45RA(-)FoxP3(low) non-suppressive T cell subsets in inflammatory conditions may contribute to SLE development. Therefore, analysis of subsets of FoxP3(+) T cells, using a combination of FoxP3, CD25 and CD45RA, rather than whole FoxP3(+) T cells, will help us to better understand the pathogenesis of SLE and may lead to the development of new therapeutic strategies.

An optimized CFSE-based T-cell suppression assay to evaluate the suppressive capacity of regulatory T-cells induced by human tolerogenic dendritic cells.

In autoimmune diseases or transplant graft rejection, a therapy that will prevent or reduce the present immune activation is highly desired. Ex vivo generated tolerogenic dendritic cells (DC) are considered to have a strong potential as cellular therapy for these diseases. One of the mechanisms of immune suppression mediated by tolerogenic DC is the induction of regulatory T-cells (Treg). Consequently, the efficacy of such DC to induce Treg will reflect their tolerogenic capacity. Because no specific markers have been described for human induced (i)Treg yet, the Treg can only be appreciated by functionality. Therefore, we have optimized an in vitro suppression assay to screen for human DC-induced-Treg activity. IL-10-generated tolerogenic DC were used to induce Treg that were previously shown to effectively suppress the proliferation of responder T-cells stimulated with allogeneic mature DC (mDC). Our results show that the suppressive capacity of IL-10 DC-induced Treg measured in the suppression assay increases with the iTreg dose and decreases with higher numbers of antigen-presenting cells (APC) as T-cell stimulation. Lowering the ratio between responder T-cells and stimulator mDC present in the coculture clearly improved the read-out of the suppression assay. Furthermore, mDC-primed T-cells in the suppression assay were shown to be an essential control condition. In conclusion, we recommend titrations of both APC and iTreg in the suppression assay and to include a negative control condition with T-cells primed by mDC, to distinguish specific and functional suppression by iTreg from possible generalized suppressive activity.

Lymphocyte recruitment into the tumor site is altered in patients with MSI-H colon cancer.

The ability of the host to mount an appropriate immune response to aberrant cells is one factor that determines prognosis in cancer patients. Naturally occurring regulatory T cells (T regs; CD4+ CD25+ cells) are key regulators of peripheral tolerance. It has been suggested that high levels of T regs are detrimental to the patient in some forms of cancer, but the role of these antigen-specific cells in individuals with colorectal cancers with high levels of microsatellite instability is unknown. Herein, we examined the ability of individuals with MSI-H or microsatellite stable colon cancer to recruit lymphocytes to the tumor site. Immunohistochemical staining was performed on archived paraffin-embedded specimens from a total of 38 individuals with MSI-H (n = 25) or MSS (n = 13) colon cancers to determine the proportion of CD3+, CD8+ and CD25+ cells infiltrating the tumor site. Patients with MSI-H colon cancers had increased percentages of CD8+ TILs (cytotoxic T cells) as compared to individuals with MSS colon cancer (47.3 vs. 24.04% of the infiltrate CD8+, respectively). No differences in the levels of CD25+ T cells were observed between individuals with MSI-H colon cancers and MSS colon cancers (0.53 vs. 0.54% CD25+, respectively). Together, these data suggest that the survival advantage enjoyed by patients with MSI-H colorectal cancer may, in part, be attributed to the increased cytolytic response, but not to an antigen-specific immunosuppressive response in MSS patients.

Measurement of interleukin-21.

This unit describes three procedures for measurement of interleukin-21 (IL-21). The first employs the use of an antibody sandwich ELISA. An alternative procedure measures proliferative responses of T cells to a combination of IL-21 and IL-15 using CFSE. Finally, a method to assess IL-21-induced tyrosine phosphorylation of Stat3 in splenic CD8(+) T cells using a flow cytometry-based analysis is described.

Enhanced delivery of exogenous peptides into the class I antigen processing and presentation pathway.

Current immunization strategies, using peptide or protein antigens, generally fail to elicit cytotoxic-T-lymphocyte responses, since these antigens are unable to access intracellular compartments where loading of major histocompatibility complex class I (MHC-I) molecules occurs. In an attempt to circumvent this, we investigated whether the GM1 receptor-binding B subunit of Escherichia coli heat-labile toxin (EtxB) could be used to deliver class I epitopes. When a class I epitope was conjugated to EtxB, it was delivered into the MHC-I presentation pathway in a GM1-binding-dependent fashion and resulted in the appearance of MHC-I-epitope complexes at the cell surface. Importantly, we show that the efficiency of EtxB-mediated epitope delivery could be strikingly enhanced by incorporating, adjacent to the class I epitope, a 10-amino-acid segment from the C terminus of the DNA polymerase (Pol) of herpes simplex virus. The replacement of this 10-amino-acid segment by a heterologous sequence or the introduction of specific amino acid substitutions within this segment either abolished or markedly reduced the efficiency of class I epitope delivery. If the epitope was extended at its C terminus, EtxB-mediated delivery into the class I presentation pathway was found to be completely dependent on proteasome activity. Thus, by combining the GM1-targeting function of EtxB with the 10-amino-acid Pol segment, highly efficient delivery of exogenous epitopes into the endogenous pathway of class I antigen processing and presentation can be achieved.

"Stealth" adenoviruses blunt cell-mediated and humoral immune responses against the virus and allow for significant gene expression upon readministration in the lung.

Most of the early gene therapy trials for cystic fibrosis have been with adenovirus vectors. First-generation viruses with E1a and E1b deleted are limited by transient expression of the transgene and substantial inflammatory responses. Gene transfer is also significantly curtailed following a second dose of virus. In an effort to reduce adenovirus-associated inflammation, capsids of first-generation vectors were modified with various activated monomethoxypolyethylene glycols. Cytotoxic T-lymphocyte production was significantly reduced in C57BL/6 mice after a single intratracheal administration of modified vectors, and length of gene expression was extended from 4 to 42 days. T-cell subsets from mice exposed to the conjugated vectors demonstrated a marked decrease in Th1 responses and slight enhancement of Th2 responses compared to animals dosed with native virus. Neutralizing antibodies (NAB) against adenovirus capsid proteins were reduced in serum and bronchoalveolar lavage fluid of animals after a single dose of modified virus, allowing significant levels of gene expression upon rechallenge with native adenovirus. Modification with polyethylene glycol (PEG) also allowed substantial gene expression from the new vectors in animals previously immunized with unmodified virus. However, gene expression was significantly reduced after two doses of the same PEG-conjugated vector. Alternating the activation group of PEG between doses did produce significant gene expression upon readministration. This technology in combination with second-generation or helper-dependent adenovirus could produce dosing strategies which promote successful readministration of vector in clinical trials and marked expression in patients with significant anti-adenovirus NAB levels and reduce the possibility of immune reactions against viral vectors for gene therapy.

Preparation of monoclonal antibodies against N-(gamma-maleimidobutyryloxy)succinimide (GMBS)-conjugated acetylspermine, and development of an enzyme-linked immunosorbent assay (ELISA) for N1,N12-diacetylspermine.

We have developed three mouse monoclonal antibodies (mAb) of types IgG1 and IgG2b, i.e. anti-acetylspermine (Ac-Spm)-1 and 2 (ACSPM-1 and 2), and anti-acetylspermine (Ac-Spm)-3 (ACSPM-3), respectively, against Ac-Spm conjugated to bovine serum albumin via a heterobifunctional cross-linker, N-(gamma-maleimidobutyryloxy)succinimide (GMBS). Among these mAbs, ACSPM-2 was the most useful for the development of an enzyme-linked immunosorbent assay (ELISA) for acetylpolyamines (Ac-PAs) with glutaraldehyde (GA)-conjugated N1,N12-diacetylspermine (2Ac-Spm) or acetylspermine (Ac-Spm) as the solid phase antigen. However, GMBS-conjugated Ac-Spm did not behave as a solid phase antigen in the competitive ELISA. The ELISA is based on the principle of competition between an analyte and the conjugated antigen for the mAb, followed by immunoreaction with biotinylated anti-mouse immunoglobulin and horseradish peroxidase-streptavidin. The ACSPM-2 mAb reacted with 2Ac-Spm to the highest degree, followed by Ac-Spm, N1-acetylspermidine (N1-Ac-Spd), N8,N8-diacetylspermidine (2Ac-Spd), and spermine (Spm), the EC50 values being 0.06, 0.25, 7.0, 10, and 60 microM, respectively, but exhibited almost no cross-reaction with other polyamine-related compounds or amino acids. The method was used to determine the urinary Ac-PA levels in healthy subjects, the average value of 0.36 microg of 2Ac-Spm/g creatinine (n = 16) being obtained. The ACSPM-2 ELISA for 2Ac-Spm, which was the PA most relevant to the analysis of human urine among the five PA analogs mentioned above, might have potential for elucidation of the correlation of urinary 2Ac-Spm levels in cancers.

CTL recognition of an altered peptide associated with asparagine bond rearrangement. Implications for immunity and vaccine design.

The extent to which peptides containing chemically and post-translationally modified amino acid side chains are recognized by primed CTL has not been clearly defined. We report on the CTL recognition of a MHC class I-restricted peptide containing a cyclized asparagine (succinimide) residue. This modification of the asparagine side chain is a common intermediate structure during deamidation, isomerization, and bond rearrangements of amide-containing amino acids and also occurs as a side reaction in peptide synthesis. The CTL specifically recognized the succinimide-containing peptide showing only weak cross-reactivity at high concentrations of the parent peptide containing unmodified asparagine. Similarly, CTL raised against the parent peptide did not recognize the succinimide derivative of this peptide. Naturally processed forms of these structures are likely to occur given the importance and frequency of deamidation both in vitro and in vivo. Moreover, since succinimide intermediates of deamidated peptides can occasionally be very stable, these peptides have the potential to act as altered self-Ags with significant implications for autoimmunity. In addition, unwanted and potentially hazardous specificities may be elicited when using synthetic peptides in subunit vaccines in which succinimide residues may form spontaneously during storage or chemical synthesis.

Early identification of interleukin-16 (lymphocyte chemoattractant factor) and macrophage inflammatory protein 1 alpha (MIP1 alpha) in bronchoalveolar lavage fluid of antigen-challenged asthmatics.

Accumulation of CD4+ interleukin (IL)-2R+ lymphocytes in the airways of asthmatics is generally attributed to the presence of chemoattractant cytokines. The precise mechanism for the initiation of the earliest CD4+ lymphocyte infiltration and activation is unknown. In this study, we describe for the first time the presence of lymphocyte chemoattractant activity in the bronchoalveolar lavage (BAL) fluid obtained from asthmatics 6 h after antigen challenge. The majority of the chemoattractant activity at this early time point is represented by IL-16 (lymphocyte chemoattractant factor), a CD4+ cell-specific chemoattractant and growth factor. In addition to IL-16, macrophage inflammatory protein 1 alpha (MIP1 alpha) chemotactic bioactivity was detected in significant levels. While IL-16, MIP1 alpha, and IL-8 were all identified by enzyme-linked immunosorbent assay, the great majority of the lymphocyte chemoattractant activity in the BAL fluid after antigen challenge is attributable to IL-16 and MIP1 alpha. There were no detectable levels of IL-16 nor MIP1 alpha in BAL fluid of antigen-challenged normal subjects nor atopic nonasthmatics nor in saline-challenged lobes from the asthmatics. The identification of multiple lymphocyte chemoattractants early after antigen challenge suggests a complex cellular, as well as chemoattractant cytokine, profile in initiating the CD4+ T cell-mediated inflammatory process that is specific for the atopic asthmatic phenotype.

Simultaneous multiple synthesis of peptide-carrier conjugates.

Recently, the multipin approach for simultaneous multiple peptide synthesis was applied to the analysis of T cell determinants by using a novel cleavage method (Maeji et al., 1990). A diketopiperazine forming linker allowed cleavage of peptides into aqueous buffer which, without further purification, could be used immediately in cell culture assays. Another potential application of the technique is the simultaneous cleavage and coupling of peptides to immunogenic carriers. Without further purification the resulting conjugates can be used for the production of antipeptide antisera. The choice of carrier and conjugation chemistry is not restricted as peptide/pin cleavage occurs in aqueous solution over a range of pH and ionic strength. The method was assessed using the 2,4-dinitrophenyl group as a model hapten, diphtheria toxoid as the carrier, and N-(epsilon-maleimidocaproyloxy)succinimide as the cross-linking reagent. The resulting DNP-DT conjugate was used to prepare high titered specific anti-DNP antisera in mice.

The use of maleimidocaproyloxysuccinimide to prepare malarial peptide carrier immunogens. Immunogenicity of the linking region.

Malarial peptides synthesized with an added N terminal cysteine were conjugated to purified diphtheria toxoid (DT) protein using the bifunctional reagent maleimidocaproyloxysuccinimide (MCS). The molar ratio of peptide to carrier was determined by subtractive sulphydryl titration and confirmed by sodium dodecyl sulphate (SDS) electrophoresis. For enzyme-linked immunoabsorbent (ELISA) analysis of sera from animals immunized with the DT conjugates, peptides were conjugated to bovine serum albumin (BSA) using MCS as well as a glutaraldehyde based coupling procedure. Western blotting analysis shows that both DT and BSA adducts were recognized by monoclonal antibodies (Mabs) directed against the peptide epitopes in the native sequences. Animals immunized with the DT-peptide conjugates produced antibodies to the coupling reagent (MCS) as well as diphtheria toxoid and peptide specific antibodies. This MCS specificity could be largely abolished by pre-incubation of sera with a soluble MCS homologue, a thiosuccinimidocaproylamide (TSC).

Cross-reaction of antibodies to coupling groups used in the production of anti-peptide antibodies.

A polyclonal antibody raised against a peptide conjugated using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride to maleic anhydride-derivatised lysozyme showed substantial cross-reactivity with m-maleimidobenzoyl-N-hydroxysuccinimide ester-derivatised haemocyanin. This was due to antibodies produced against maleic anhydride-derivatised groups on lysozyme that reacted with m-maleimidobenzoyl-N-hydroxysuccinimide ester-derivatised groups on haemocyanin. This observation is important because it is common practice, in the production of anti-peptide antibodies, to use two conjugates. The same peptide is coupled to two different protein carriers by two different coupling methods. One conjugate is used for immunisation and the other for testing the serum. This method assumes that the only antigen common to the two conjugates is the peptide and this was not the case here. A method is described for screening sera which involves affinity purification of the anti-peptide antibody and comparison of binding to the immunogen with that to an appropriate control conjugate. This method avoids the problem of any cross-reaction to coupling groups or proteins.

An alternative procedure for the preparation of immunogenic liposomal model membranes.

This investigation describes a new procedure for the preparation of immunogenic liposomes which circumvents the need to synthesize the N-(hapten)-substituted derivatives of phosphatidylethanolamine that were previously employed for this purpose. The method is based on the generation of liposomes containing the N-hydroxysuccinimide (NHS) esters of either palmitic acid, cholesteryl-hemisuccinate, or N-succinyl-phosphatidylethanolamine. Reaction of these preformed liposomes with a hapten that possesses a substitutable amino group (e.g., DNP-lysine) results in covalent attachment of the hapten to the lipid bilayers. As a consequence of this binding, the liposomes can elicit formation of hapten-specific plaque-forming cells in mice. The reliability of this procedure is indicated by the fact that these liposomes share the essential immunological properties of liposomes sensitized by incorporation of N-substituted phosphatidylethanolamine derivatives (e.g., DNP-Cap-PE). Thus, the magnitude of the response was found to be dependent on: (a) the presence of lipid A in the liposomes; (b) the phospholipid composition of the liposomes; (c) the distance separating the DNP determinant from the liposomal surface. Additional applications of liposomes, which contain the NHS esters, are indicated.

[Synthesis of phenol-antigen conjugates by reacting N-hydroxysuccinimidic esters of hydroxybenzoic acids with human serum albumin and bovine gamma globulin]. / Synthese von Phenol-Antigen-Konjugaten durch Umsetzung von N-Hyroxysuccinimidestern von Hydroxybenzoesäuren mit Humanserumalbumin und Rindergammaglobulin.

Salicylic acid, beta-resorcylic acid and gentisic acid were acetylated and then reacted with N-hydroxysuccinimide according to the DDC procedure to give the corresponding activated esters. The reaction of these N-hydroxysuccinimidic esters with human serum albumin and bovine gamma globulin yielded modified proteins containing hydroxybenzoyl residues linked to amino groups, the mode of linkage being of the acid amide type.

Hapten-specific T cell responses to 4-hydroxy-3-nitrophenyl acetyl.

The primary anti-(4-hydroxy-3-nitrophenyl)acetyl (NP) antibody response is known to have a heteroclitic fine specificity, i.e., anti-NP antibodies bind (4-hydroxy-5-iodo-3-nitrophenyl)acetyl (NIP) with greater affinity than NP itself. Past studies of NP-specific DTH responses and NP-specific T cell-mediated suppression have demonstrated sharing of fine specificity patterns and idiotypic structure between receptors on NP-specific T cells and anti-NP antibodies. We now analyze the fine specificity of NP-specific cutaneous sensitivity (CS) reactions to NP-O-succinimide (NP-O-Su) and NIP-O-succinimide (NIP-O-Su). The specificity of these responses is shown to be controlled by genes in the Igh gene complex. Cross-reactive CS responses induced by NP-O-Su elicited by NIP-O-Su were observed in strains of mice possessing the Igh-1b allotype but not in strains bearing the Igh-1c or Igh-1j allotypes. The CS reactivity could be adoptively transferred to naive recipients, and the ability of transfer CS reactivity was T cell dependent. In contrast to the genetic requirement for I-A region homology to adoptively transfer DTH reactions, compatibility at either the H-2K, H-21, or H-2D regions was sufficient to transfer NP-specific CS reactivity to naive recipients. Furthermore, in contrast to DTH responses, cyclophosphamide pretreatment was not required to induce CS responsiveness. Thus, the specificity of NP-O-Su-induced CS responses is controlled by both H-2- and Igh-linked genes.

Renin activity solid phase radioimmunoassay.

A solid-phase radioimmunoassay for measurement of generation angiotensin I (renin activity) in plasma is reported. The angiontensin I antisera were attached to diazotized arylamine and N-hydroxy succinimide controlled pore glass, and reacted with labelled and unlabelled angiotentin I for saturation analysis before and after one hour incubation. Chelating agents were used to inhibit the conversion of angiotensin I to angiotensin II in vitro. The assay is accurate, rapid and reproducible.