Octyl itaconate enhances VSVΔ51 oncolytic virotherapy by multitarget inhibition of antiviral and inflammatory pathways

The presence of heterogeneity in responses to oncolytic virotherapy poses a barrier to clinical effectiveness, as resistance to this treatment can occur through the inhibition of viral spread within the tumor, potentially leading to treatment failures. Here we show that 4-octyl itaconate (4-OI), a chemical derivative of the Krebs cycle-derived metabolite itaconate, enhances oncolytic virotherapy with VSVΔ51 in various models including human and murine resistant cancer cell lines, three-dimensional (3D) patient-derived colon tumoroids and organotypic brain tumor slices. Furthermore, 4-OI in combination with VSVΔ51 improves therapeutic outcomes in a resistant murine colon tumor model. Mechanistically, we find that 4-OI suppresses antiviral immunity in cancer cells through the modification of cysteine residues in MAVS and IKKβ independently of the NRF2/KEAP1 axis. We propose that the combination of a metabolite-derived drug with an oncolytic virus agent can greatly improve anticancer therapeutic outcomes by direct interference with the type I IFN and NF-κB-mediated antiviral responses.

An anti-TNF-glucocorticoid receptor modulator antibody-drug conjugate is efficacious against immune-mediated inflammatory diseases

Glucocorticoids (GCs) are efficacious drugs used for treating many inflammatory diseases, but the dose and duration of administration are limited because of severe side effects. We therefore sought to identify an approach to selectively target GCs to inflamed tissue. Previous work identified that anti-tumor necrosis factor (TNF) antibodies that bind to transmembrane TNF undergo internalization; therefore, an anti-TNF antibody-drug conjugate (ADC) would be mechanistically similar, where lysosomal catabolism could release a GC receptor modulator (GRM) payload to dampen immune cell activity. Consequently, we have generated an anti-TNF-GRM ADC with the aim of inhibiting pro-inflammatory cytokine production from stimulated human immune cells. In an acute mouse model of contact hypersensitivity, a murine surrogate anti-TNF-GRM ADC inhibited inflammatory responses with minimal effect on systemic GC biomarkers. In addition, in a mouse model of collagen-induced arthritis, single-dose administration of the ADC, delivered at disease onset, was able to completely inhibit arthritis for greater than 30 days, whereas an anti-TNF monoclonal antibody only partially inhibited disease. ADC treatment at the peak of disease was also able to attenuate the arthritic phenotype. Clinical data for a human anti-TNF-GRM ADC (ABBV-3373) from a single ascending dose phase 1 study in healthy volunteers demonstrated antibody-like pharmacokinetic profiles and a lack of impact on serum cortisol concentrations at predicted therapeutic doses. These data suggest that an anti-TNF-GRM ADC may provide improved efficacy beyond anti-TNF alone in immune mediated diseases while minimizing systemic side effects associated with standard GC treatment.

A first-in-human study of the novel immunology antibody-drug conjugate, ABBV-3373, in healthy participants

AIMS

ABBV-3373, an immunology antibody-drug conjugate composed of adalimumab conjugated to a proprietary glucocorticoid receptor modulator (the small-molecule payload), has the potential to treat immune-mediated inflammatory diseases. This first-in-human study investigated the pharmacokinetics (PK), immunogenicity, pharmacodynamics (PD) using a safety PD marker, and safety/tolerability of ABBV-3373 in healthy adults.

METHODS

Fifty-five participants were randomly assigned to single-dose subcutaneous (SC; 30, 100 or 300 mg) or intravenous (IV; 30, 300 or 900 mg) ABBV-3373 or placebo. Eight additional participants received a single dose of 10 mg oral prednisone for evaluation of systemic glucocorticoid effects. Blood samples were collected for up to 85 days postdose for PK, anti-drug antibody and serum cortisol (safety PD marker) assessments.

RESULTS

ABBV-3373 and total antibody displayed antibody-like SC/IV PK profiles and the unconjugated/free payload in circulation exhibited formation rate-limited kinetics with exposure several fold lower than ABBV-3373 or total antibody. Treatment-emergent anti-drug antibody incidence was 69%, with loss of exposure in 6% (SC) and 5% (IV) of participants, but without any impact on safety. ABBV-3373 up to 300 mg SC/IV had no apparent impact on serum cortisol, and only caused a transient decrease at 900 mg IV. Treatment-emergent adverse events were primarily mild in severity, and no pattern emerged with respect to dose or route of administration.

CONCLUSIONS

ABBV-3373 had favourable PK profiles, manageable immunogenicity, and was generally well-tolerated. Except for a transient effect at 900 mg IV, there was no apparent impact on serum cortisol. Study results supported further clinical development of ABBV-3373.

4-Octyl itaconate reduces influenza A replication by targeting the nuclear export protein CRM1

IMPORTANCE

Itaconate derivates, as well as the naturally produced metabolite, have been proposed as antivirals against influenza virus. Here, the mechanism behind the antiviral effects of exogenous 4-octyl itaconate (4-OI), a derivative of itaconate, against the influenza A virus replication is demonstrated. The data indicate that 4-OI targets the cysteine at position 528 of the CRM1 protein, resulting in inhibition of the nuclear export of viral ribonucleoprotein complexes in a similar manner as previously described for other selective inhibitors of nuclear export. These results postulate a mechanism not observed before for this immuno-metabolite derivative. This knowledge is helpful for the development of derivatives of 4-OI as potential antiviral and anti-inflammatory therapeutics.

OP0024 DIFFERENTIATION BETWEEN IL-6 AND IL-17 PATHWAY INHIBITION IN RELATIONSHIP WITH CLINICAL OUTCOMES IN NON-BIOLOGICAL DMARD-IR AND BIOLOGICAL DMARD-IR PSORIATIC ARTHRITIS PATIENTS TREATED WITH UPADACITINIB IN SELECT-PsA 1 AND SELECT-PsA 2 STUDIES

Background

The differential contribution of IL-6 and IL-17 pathways to the pathogenesis of psoriatic arthritis (PsA) is not fully understood. Upadacitinib (UPA), an oral JAK inhibitor, was more effective than placebo (PBO) in improving key clinical manifestations of PsA in two global phase 3 trials, SELECT-PsA 1 (non-biological DMARD-IR, nbDMARD-IR) and SELECT-PsA 2 (biological DMARD-IR, bDMARD-IR).1,2 Targeted proteomic analysis suggested that UPA modulates multiple biological pathways in innate and adaptive immune systems via direct and indirect inhibition of key regulators, including IL-6 and IL-17 pathways, with a possible shift from Th1 predominance in nbDMARD-IR PsA to a more Th17 bias in bDMARD-IR PsA.3

Objectives

We assessed the relationship between IL-6 and IL-17 pathway modulation and different clinical outcomes after UPA treatment in nbDMARD-IR and bDMARD-IR PsA patients.

Methods

A subset of patients was randomly selected from SELECT-PsA 1 (n=74 of UPA 15 mg QD, n=74 of PBO) and PsA 2 studies (n=90 of UPA 15 mg QD, n=81 of PBO). Serum levels of IL-6, IL-17A, IL-17F, and beta-defensin 2 (BD2) proteins were measured at baseline, week 2, and week 12 by validated immunoassays. The quantitative cytokine measurements were transformed as log10, and PASI score was transformed as log10 (x+1) prior to analysis. A Repeated Measure Mixed Linear Model was used to compare UPA versus PBO treatment effects in overall selected patients and between responders and non-responders defined by PASDAS score ≤ 3.6 (Minimal Disease Activity, MDA)4 and PASI75 at week 12, respectively. The relationships between cytokines and clinical outcomes (PASI and DAS28-CRP) were assessed by Pearson’s correlation at baseline and after treatment.

Results

In nbDMARD-IR PsA patients, baseline IL-17A, IL-17F, and BD2 levels correlated with each other and with PASI, while IL-6 appeared independent from the IL-17 pathway and correlated with DAS28-CRP. At week 12, UPA treatment significantly decreased IL-6 and BD2. The decrease of IL-6 was more pronounced in PASDAS MDA responders and correlated with DAS28-CRP improvement, but the decrease of BD2 was significant in PASI75 responders and correlated with PASI improvement. In contrast, IL-17A and IL-17F were not significantly changed after UPA treatment, neither correlated with clinical outcomes at week 12.

In bDMARD-IR PsA patients, baseline IL-17A level was significantly elevated compared to nbDMARD-IR patients but weakly correlated with other cytokines and show no correlation with PASI. At week 12, the reduction of IL-6 after UPA treatment was not different between responders and non-responders (PASDAS MDA or PASI75) and did not correlate with DAS28-CRP improvement, while the reduction of BD2 remained significant in PASI75 responders and correlated with PASI improvement. Further, UPA treatment significantly reduced IL-17A in PASDAS MDA responders and IL-17F in PASI75 responders compared to non-responders, respectively. The reduction of IL-17F correlated with PASI improvement at week 12.

Conclusion

IL-6 and IL-17 pathway inhibition after UPA treatment showed different profiles in relationship with clinical outcomes in nbDMARD-IR versus bDMARD-IR PsA patients. IL-6 decrease was more pronounced in nbDMARD-IR PsA patients and associated with joint manifestation improvement, while IL-17A and IL-17F decreases were only observed in bDMARD-IR PsA patients and associated with psoriasis improvement. BD2, a biomarker of Th17-associated skin pathology, significantly decreased after UPA treatment in both nbDMARD-IR and bDMARD-IR PsA studies, which likely contributed to UPA effects on psoriasis improvement in a broad range of PsA patients.

References

[1]McInnes IB, et al. N Engl J Med 2021;384:1227-39.

[2]Mease PJ, et al. Ann Rheum Dis 2020;80:312-20.

[3]Sornasse T, et al. Ann Rheum Dis 2021;80:433.

[4]Salaffi F, et al. Biomed Res Int 2014;2014:528105.

Acknowledgements

AbbVie, Inc., in collaboration with the authors, contributed to the study design, data collection and analysis, interpretation of the results, and preparation, review and approval of the final version. No honoraria or payments were made for authorship.

Disclosure of Interests

Fang Cai Shareholder of: AbbVie, Employee of: AbbVie, Thierry Sornasse Shareholder of: AbbVie, Employee of: AbbVie, Melanie Ruzek Shareholder of: AbbVie, Employee of: AbbVie, Yuni Fang Shareholder of: AbbVie, Employee of: AbbVie, Koji Kato Shareholder of: AbbVie, Employee of: AbbVie, Peter Wung Shareholder of: AbbVie, Employee of: AbbVie, Iain McInnes Consultant of: AbbVie, AstraZeneca, BMS, Lilly, Amgen, Causeway, Oxford Biodynamics, Novartis, Janssen, Pfizer, Boehringer, and UCB, Grant/research support from: AbbVie, AstraZeneca, BMS, Lilly, Amgen, Causeway, Oxford Biodynamics, Novartis, Janssen, Pfizer, Boehringer, and UCB.

POS0365 ANTI-TNF GLUCOCORTICOID RECEPTOR MODULATOR ANTIBODY DRUG CONJUGATE FOR THE TREATMENT OF AUTOIMMUNE DISEASES

Background:

Glucocorticoids (GC) are potent drugs used for treating many inflammatory diseases. While GCs are effective in many immune diseases, dose and duration of administration is limited due to significant side effects. Resting immune cells have very little TNF expression on the cell surface and it is only in an activated state that TNF expression is upregulated. Upon immune cell stimulation, TNF is upregulated and although a significant amount of TNF is cleaved from an activated cell, a portion remains on the cell surface. We have observed that anti-TNF antibodies bind to transmembrane TNF (tmTNF) and undergo endocytosis to the lysosome (1). We have developed a stable antibody drug conjugate (ADC), ABBV-3373, that has a proprietary, highly potent, glucocorticoid receptor modulator (GRM) payload linked to an anti-TNF monoclonal antibody (mAb) that is able to deliver the GC payload to activated immune cells.

Objectives:

We hypothesized that a TNF ADC with a GRM payload would be able to deliver increased efficacy through both TNF inhibition and targeted GRM payload delivery to activated immune cells while sparing systemic glucocorticoid side effects.

Methods:

A mouse surrogate TNF GRM ADC was characterized in an acute in vivo contact hypersensitivity model of inflammation (CHS) and in a mouse model of collagen induced arthritis (mCIA). Additionally, the human anti-TNF GRM ADC, ABBV-3373 has been characterized in healthy volunteers.

Results:

In the CHS model the anti-TNF GRM ADC significantly inhibited the inflammatory response with minimal effect on systemic GC biomarkers. In mCIA a single dose of an anti-TNF GRM ADC, administered at disease onset, was able to completely inhibit arthritis for greater than 30 days while an anti-TNF mAb only partially inhibited disease. ABBV-3373, a human anti-TNF GRM ADC with a GC payload, was evaluated in a Phase 1 study in healthy volunteers. ABBV-3373 demonstrated antibody-like PK profile and ABBV-3373 did not impact cortisol levels at predicted efficacious doses while control subjects that received a single oral dose of 10 mg prednisone demonstrated expected decreases in cortisol levels.

Conclusion:

These data suggest that an anti-TNF ADC delivering a GRM payload into activated immune cells may provide improved efficacy in immune mediated diseases, while minimizing systemic side effects associated with standard GC treatment.

References:

[1]Deora, A. et al. MABs. 2017;9(4):680-695.

Disclosure of Interests:

Bob Stoffel Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie, Michael McPherson Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie, Axel Hernandez Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie, Christian Goess Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie, Suzanne Mathieu Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie, Wendy Waegell Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie, Shaughn Bryant Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie, Adrian Hobson Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie, Melanie Ruzek Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie, Yinuo Pang Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie, Hartmut Kupper Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie, Ronilda D’Cunha Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie, Julie Parmentier Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie, Timothy Radstake Shareholder of: AbbVie, Grant/research support from: AbbVie, Employee of: AbbVie

Adalimumab Induces a Wound Healing Profile in Patients with Hidradenitis Suppurativa by Regulating Macrophage Differentiation and Matrix Metalloproteinase Expression

Adalimumab (ADA) is the only Food and Drug Administration‒approved treatment for moderate-to-severe hidradenitis suppurativa, whereas etanercept and certolizumab-pegol have been shown to be ineffective, suggesting that the mechanism of action of ADA is distinct in hidradenitis suppurativa and may contribute to improved wound healing. Given that macrophages (Mϕs) play pivotal roles throughout the wound healing process, an in vitro Mϕ differentiation assay was carried out to assess the impact of TNF‒anti-TNF complexes on these cells. TNF‒ADA complexes exhibited stronger inhibitory effects on inflammatory Mϕ differentiation. Moreover, RNA sequencing revealed several unique wound healing profiles for TNF‒ADA‒treated inflammatory Mϕs, which were not observed for those treated with either TNF‒etanercept or TNF‒certolizumab-pegol complexes, including the inhibition of the matrix metalloproteinase (MMP) pathway. In addition, ADA administration was found to significantly reduce the levels of inflammatory MMP-1 and MMP-9 while promoting wound-healing MMP-13 and tissue inhibitor of metalloproteinases 2 levels in the circulation of the patients with hidradenitis suppurativa who responded to treatment. Our in vitro findings show that TNF‒ADA‒treated inflammatory Mϕs exhibit a distinct profile resembling wound healing. Moreover, ADA not only differentially regulates MMP expression in patients with hidradenitis suppurativa responding to the therapy but also potentially induces a transition to a profile suggestive of wound healing.

Modeling the clinical phenotype of BTK inhibition in the mature murine immune system

Inhibitors of Bruton's tyrosine kinase (BTK) possess much promise for the treatment of oncologic and autoimmune indications. However, our current knowledge of the role of BTK in immune competence has been gathered in the context of genetic inactivation of btk in both mice and man. Using the novel BTK inhibitor PF-303, we model the clinical phenotype of BTK inhibition by systematically examining the impact of PF-303 on the mature immune system in mice. We implicate BTK in tonic BCR signaling, demonstrate dependence of the T3 B cell subset and IgM surface expression on BTK activity, and find that B1 cells survive and function independently of BTK. Although BTK inhibition does not impact humoral memory survival, Ag-driven clonal expansion of memory B cells and Ab-secreting cell generation are inhibited. These data define the role of BTK in the mature immune system and mechanistically predict the clinical phenotype of chronic BTK inhibition.

A Bruton’s Tyrosine Kinase inhibitor prevents antigen-driven B cell activation, germinal center persistence and memory B cell re-activation in vivo (109.10)

The Tec family kinase, Bruton’s Tyrosine Kinase (BTK), is one of the key intracellular signaling components proximal to the B cell receptor (BCR). In this study, we utilized an orally-accessible BTK inhibitor (BTKi) to study the functional effects blocking this signaling pathway has on antigen-driven B cell activation in vivo. We report that BTK is required for anti-IgD driven B cell activation in vivo as evidenced by suppression of the surface activation markers CD86 and mRNA transcripts (e.g. c-Myc, Bcl-xL, CCL3, CD98, EBI2, EGR1, EGR2 and IRF4) otherwise rapidly induced upon engagement of the BCR with antigen. Using the T-dependent protein PE and SRBCs as model antigens, we tested for a requirement of BTK in generating antigen-specific IgM and IgG antibody titers and germinal centers, and find that BTK is required for germinal center maintenance. Lastly, we tested for a role of BTK in long-lived PE-specific memory B cell re-activation and report that BTKi significantly suppressed the induction of PE-specific IgM and IgG titers upon antigen re-challenge. The use of BTKi allowed us to bypass the impact a genetically inactivated BTK gene has on B cell development and to assess BTK inactivation in both a wild-type setting and in a temporal manner. These results provide insight into the role of BTK in BCR-driven B cell activation in various antigen naïve and experienced B cell populations.

Reducing glycosphingolipid biosynthesis in airway cells partially ameliorates disease manifestations in a mouse model of asthma

Lipid rafts reportedly play an important role in modulating the activation of mast cells and granulocytes, the primary effector cells of airway hyperresponsiveness and asthma. Activation is mediated through resident signaling molecules whose activity, in part, may be modulated by the composition of glycosphingolipids (GSLs) in membrane rafts. In this study, we evaluated the impact of inhibiting GSL biosynthesis in mast cells and in the ovalbumin (OVA)-induced mouse model of asthma using either a small molecule inhibitor or anti-sense oligonucleotides (ASOs) directed against specific enzymes in the GSL pathway. Lowering GSL levels in mast cells through inhibition of glucosylceramide synthase (GCS) reduced phosphorylation of Syk tyrosine kinase and phospholipase C gamma 2 (PLC-gamma2) as well as cytoplasmic Ca(2+) levels. Modulating these intracellular signaling events also resulted in a significant decrease in mast cell degranulation. Primary mast cells isolated from a GM3 synthase (GM3S) knockout mouse exhibited suppressed activation-induced degranulation activity further supporting a role of GSLs in this process. In previously OVA-sensitized mice, intra-nasal administration of ASOs to GCS, GM3S or lactosylceramide synthase (LCS) significantly suppressed metacholine-induced airway hyperresponsiveness and pulmonary inflammation to a subsequent local challenge with OVA. However, administration of the ASOs into mice that had been sensitized and locally challenged with the allergen did not abate the consequent pulmonary inflammatory sequelae. These results suggest that GSLs contribute to the initiation phase of the pathogenesis of airway hyperreactivity and asthma and lowering GSL levels may offer a novel strategy to modulate these manifestations.

Allogeneic mesenchymal stem cells do not protect NZBxNZW F1 mice from developing lupus disease

Mesenchymal stem cell (MSC) therapy has shown promise clinically in graft-versus-host disease and in preclinical animal models of T helper type 1 (Th1)-driven autoimmune diseases, but whether MSCs can be used to treat autoimmune disease in general is unclear. Here, the therapeutic potential of MSCs was tested in the New Zealand black (NZB)xNew Zealand white (NZW) F1 (NZB/W) lupus mouse model. The pathogenesis of systemic lupus erythematosus involves abnormal B and T cell activation leading to autoantibody formation. To test whether the immunomodulatory activity of MSCs would inhibit the development of autoimmune responses and provide a therapeutic benefit, NZB/W mice were treated with Balb/c-derived allogeneic MSCs starting before or after disease onset. Systemic MSC administration worsened disease and enhanced anti-double-stranded DNA (dsDNA) autoantibody production. The increase in autoantibody titres was accompanied by an increase in plasma cells in the bone marrow, an increase in glomerular immune complex deposition, more severe kidney pathology, and greater proteinuria. Co-culturing MSCs with plasma cells purified from NZB/W mice led to an increase in immunoglobulin G antibody production, suggesting that MSCs might be augmenting plasma cell survival and function in MSC-treated animals. Our results suggest that MSC therapy may not be beneficial in Th2-type T cell- and B cell-driven diseases such as lupus and highlight the need to understand further the appropriate application of MSC therapy.

Human endothelial precursor cells express tumor endothelial marker 1/endosialin/CD248

Angiogenesis occurs during normal physiologic processes as well as under pathologic conditions such as tumor growth. Serial analysis of gene expression profiling revealed genes [tumor endothelial markers (TEM)] that are overexpressed in tumor endothelial cells compared with normal adult endothelial cells. Because blood vessel development of malignant tumors under certain conditions may include endothelial precursor cells (EPC) recruited from bone marrow, we investigated TEM expression in EPC. The expression of TEM1 or endosialin (CD248) and other TEM has been discovered in a population of vascular endothelial growth factor receptor 2+/CD31+/CD45-/VE-cadherin+ EPC derived from human CD133+/CD34+ cells. EPC share some properties with fully differentiated endothelial cells from normal tissue, yet reverse transcription-PCR and flow cytometry reveal that EPC express higher levels of endosialin at the molecular and protein levels. The elevated expression of endosialin in EPC versus mature endothelial cells suggests that endosialin is involved in the earlier stages of tumor angiogenesis. Anti-endosialin antibodies inhibited EPC migration and tube formation in vitro. In vivo, immunohistochemistry indicated that human EPC continued to express endosialin protein in a Matrigel plug angiogenesis assay established in nude mice. Anti-endosialin antibodies delivered systemically at 25 mg/kg were also able to inhibit circulating murine EPC in nude mice bearing s.c. SKNAS tumors. EPC and bone marrow-derived cells have been shown previously to incorporate into malignant blood vessels in some instances, yet they remain controversial in the field. The data presented here on endothelial genes that are up-regulated in tumor vasculature and in EPC support the hypothesis that the angiogenesis process in cancer can involve EPC.

Anti-thymocyte globulin (ATG) prevents autoimmune encephalomyelitis by expanding myelin antigen-specific Foxp3+ regulatory T cells

The T cell-depleting polyclonal antibody, anti-thymocyte globulin (ATG) has long been used in organ transplantation to treat acute rejection episodes. More recently, it is also being used as part of an induction regimen to protect allografts. It has been proposed that ATG might deplete effector T cells (T-effs) while sparing regulatory T cells (T-regs). In order to test whether ATG is effective in autoimmune disease, we used Foxp3gfp 'knock-in' mice in combination with a myelin oligodendrocyte glycoprotein (MOG)(35-55)/IA(b) tetramer to study more closely the effect of ATG treatment on antigen-specific T cell responses in vivo during MOG-induced experimental autoimmune encephalomyelitis (EAE), an animal model for Multiple Sclerosis. ATG treatment enhanced the expansion of MOG-specific T-regs (CD4(+)Foxp3(+)) in MOG-immunized mice. T-effs were depleted, but on a single-cell basis, the effector function of residual T-effs was not compromised by ATG. Thus, ATG tipped the balance of T-effs and T-regs and skewed an auto-antigen-specific immune reaction from a pathogenic T cell response to a potentially protective T-reg response. In both acute and relapsing remitting disease models, ATG treatment resulted in the attenuation from EAE, both in a preventive and early therapeutic setting. We conclude that ATG treatment enforces the development of a dominant immunoregulatory environment which may be advantageous for the treatment of T cell-driven autoimmune diseases.

Degradation of C3 by Streptococcus pneumoniae

After growth to exponential phase in Todd-Hewitt broth, clinical and laboratory isolates of Streptococcus pneumoniae serotypes 3, 4, and 14 readily degraded first the beta and then the alpha chains of purified human C3 in the absence of serum or other complement proteins, as assessed by SDS-PAGE. With exponentially growing pneumococci, degradation of native C3 was detectable within 30 min; methylamine-treated C3 and preformed C3b were degraded with equal avidity. Pneumococcal C3-degrading activity was cell associated, abolished by heat killing, and independent of the presence of the polysaccharide capsule. After degradation, 44% of C3 molecules contained a disrupted thiolester bond. Pneumococci treated with 100 micrograms of mutanolysin released 94% of C3-degrading activity from the pneumococcal surface into the supernatant. These studies demonstrate that clinical and laboratory isolates of virulent pneumococci degrade and inactivate soluble C3.