Latent human herpesvirus 6 is reactivated in CAR T cells.

Cell therapies have yielded durable clinical benefits for patients with cancer, but the risks associated with the development of therapies from manipulated human cells are understudied. For example, we lack a comprehensive understanding of the mechanisms of toxicities observed in patients receiving T cell therapies, including recent reports of encephalitis caused by reactivation of human herpesvirus 6 (HHV-6)1. Here, through petabase-scale viral genomics mining, we examine the landscape of human latent viral reactivation and demonstrate that HHV-6B can become reactivated in cultures of human CD4+ T cells. Using single-cell sequencing, we identify a rare population of HHV-6 'super-expressors' (about 1 in 300-10,000 cells) that possess high viral transcriptional activity, among research-grade allogeneic chimeric antigen receptor (CAR) T cells. By analysing single-cell sequencing data from patients receiving cell therapy products that are approved by the US Food and Drug Administration2 or are in clinical studies3-5, we identify the presence of HHV-6-super-expressor CAR T cells in patients in vivo. Together, the findings of our study demonstrate the utility of comprehensive genomics analyses in implicating cell therapy products as a potential source contributing to the lytic HHV-6 infection that has been reported in clinical trials1,6-8 and may influence the design and production of autologous and allogeneic cell therapies.

Surgical priorities in abdominal Crohn's disease.

Crohn's disease is a chronic disorder associated with a high rate of recurrence and morbidity. New therapies have been developed over the last few decades that have improved both induction of remission and lowered recurrence rates which led to improved outcomes. An overarching set of principles connects these therapies with prevention of recurrence being the top priority. To achieve the best outcomes, patients must be carefully chosen, optimized, and the correct surgery performed by an experienced and multidisciplinary team at the appropriate time. We seek to outline the current evidence-based approach to the surgical management of Crohn's disease.

Clinical feasibility and treatment outcomes with nonselected autologous tumor-infiltrating lymphocyte therapy in patients with advanced cutaneous melanoma.

Nonselected autologous tumor-infiltrating lymphocytes (TILs) may provide advantages over other treatments for solid tumors, including checkpoint inhibitor-refractory melanoma. This retrospective analysis reports a single-center experience of nonselected autologous TILs derived from digested tumors for compassionate use treatment of advanced cutaneous melanoma, including after programmed cell death protein 1 (PD-1) inhibition. Patients with histologically confirmed metastatic cutaneous melanoma and no standard-of-care treatment options underwent tumor resection for TIL product manufacturing. Patients received lymphodepleting chemotherapy with cyclophosphamide for 2 days and fludarabine for 5 days, followed by a single TIL infusion and post-TIL high-dose interleukin (IL)-2. Safety assessments included clinically significant adverse events (AEs). Efficacy assessments included overall response rate (ORR), complete response (CR) rate, disease control rate (DCR), and overall survival. Between October 2011 and August 2019, 21 patients underwent treatment (median follow-up time, 52.2 months from TIL infusion). Among all treated patients, median age was 45 years, median number of disease sites was 4, 100% had M1c or M1d disease, and 90% received prior checkpoint inhibitor. Twelve patients received TILs after prior PD-1 inhibition. The safety profile among all treated patients and the prior PD-1 inhibitor subgroup was generally consistent with lymphodepletion and high-dose IL-2. No treatment-related deaths occurred. Among all patients, the ORR was 67%, CR rate was 19%, and the DCR was 86%, which was consistent with that observed in the prior PD-1 inhibitor subgroup (58%, 8%, and 75%, respectively). Median overall survival in all treated patients and the prior PD-1 inhibitor subgroup was 21.3 months. In total, 5 patients (24%) had durable ongoing responses (>30 months post-TIL infusion) at data cutoff, and all patients who achieved CR remained alive and disease free. To further illustrate how TIL therapy may integrate into established treatment paradigms, several case studies of patients treated in this series were included. Overall, these data demonstrate that manufacturing of nonselected autologous TILs from tumor digests is feasible and resulted in high rates of durable response in poor-risk patient populations, which may address significant unmet medical need.

Selective Continuous Positive Airway Pressure Withdrawal With Supplemental Oxygen During Slow-Wave Sleep as a Method of Dissociating Sleep Fragmentation and Intermittent Hypoxemia-Related Sleep Disruption in Obstructive Sleep Apnea.

Obstructive sleep apnea (OSA) is considered to impair memory processing and increase the expression of amyloid-ß (Aß) and risk for Alzheimer's disease (AD). Given the evidence that slow-wave sleep (SWS) is important in both memory and Aß metabolism, a better understanding of the mechanisms by which OSA impacts memory and risk for AD can stem from evaluating the role of disruption of SWS specifically and, when such disruption occurs through OSA, from evaluating the individual contributions of sleep fragmentation (SF) and intermittent hypoxemia (IH). In this study, we used continuous positive airway pressure (CPAP) withdrawal to recapitulate SWS-specific OSA during polysomnography (PSG), creating conditions of both SF and IH in SWS only. During separate PSGs, we created the conditions of SWS fragmentation but used oxygen to attenuate IH. We studied 24 patients (average age of 55 years, 29% female) with moderate-to-severe OSA [Apnea-Hypopnea Index (AHI); AHI4% > 20/h], who were treated and adherent to CPAP. Participants spent three separate nights in the laboratory under three conditions as follows: (1) consolidated sleep with CPAP held at therapeutic pressure (CPAP); (2) CPAP withdrawn exclusively in SWS (OSA SWS ) breathing room air; and (3) CPAP withdrawn exclusively in SWS with the addition of oxygen during pressure withdrawal (OSA SWS + O 2). Multiple measures of SF (e.g., arousal index) and IH (e.g., hypoxic burden), during SWS, were compared according to condition. Arousal index in SWS during CPAP withdrawal was significantly greater compared to CPAP but not significantly different with and without oxygen (CPAP = 1.1/h, OSA SWS + O2 = 10.7/h, OSA SWS = 10.6/h). However, hypoxic burden during SWS was significantly reduced with oxygen compared to without oxygen [OSA SWS + O 2 = 23 (%min)/h, OSA SWS = 37 (%min)/h]. No significant OSA was observed in non-rapid eye movement (REM) stage 1 (NREM 1), non-REM stage 2 (NREM 2), or REM sleep (e.g., non-SWS) in any condition. The SWS-specific CPAP withdrawal induces OSA with SF and IH. The addition of oxygen during CPAP withdrawal results in SF with significantly less severe hypoxemia during the induced respiratory events in SWS. This model of SWS-specific CPAP withdrawal disrupts SWS with a physiologically relevant stimulus and facilitates the differentiation of SF and IH in OSA.

Effects of obstructive sleep apnea on human spatial navigational memory processing in cognitively normal older individuals.

STUDY OBJECTIVES: Obstructive sleep apnea (OSA) prevalence increases with age, but whether OSA-related sleep disruption could interrupt the processing of previously encoded wake information thought to normally occur during sleep in cognitively normal older adults remains unknown. METHODS: Fifty-two older (age = 66.9 ± 7.7 years, 56% female), community-dwelling, cognitively normal adults explored a 3-D maze environment and then performed 3 timed trials before (evening) and after (morning) sleep recorded with polysomnography with a 20-minute morning psychomotor vigilance test. RESULTS: Twenty-two (22) participants had untreated OSA [apnea-hypopnea index (AHI4%) ≥ 5 events/h] where severity was mild on average [median (interquartile range); AHI4% = 11.0 (20.7) events/h] and 30 participants had an AHI4% < 5 events/h. No significant differences were observed in overnight percent change in completion time or in the pattern of evening presleep maze performance. However, during the morning postsleep trials, there was a significant interaction between OSA group and morning trial number such that participants with OSA performed worse on average with each subsequent morning trial, whereas those without OSA showed improvements. There were no significant differences in morning psychomotor vigilance test performance, suggesting that vigilance is unlikely to account for this difference in morning maze performance. Increasing relative frontal slow wave activity was associated with better overnight maze performance improvement in participants with OSA (r = .51, P = .02) but not in those without OSA, and no differences in slow wave activity were observed between groups. CONCLUSIONS: OSA alters morning performance in spatial navigation independent of a deleterious effect on morning vigilance or evening navigation performance. Relative frontal slow wave activity is associated with overnight performance change in older participants with OSA, but not those without.

Activation of CAR and non-CAR T cells within the tumor microenvironment following CAR T cell therapy.

Mechanisms of chimeric antigen receptor (CAR) T cell-mediated antitumor immunity and toxicity remain poorly characterized because few studies examine the intact tumor microenvironment (TME) following CAR T cell infusion. Axicabtagene ciloleucel is an autologous anti-CD19 CAR T cell therapy approved for patients with large B cell lymphoma. We devised multiplex immunostaining and ISH assays to interrogate CAR T cells and other immune cell infiltrates in biopsies of diffuse large B cell lymphoma following axicabtagene ciloleucel infusion. We found that a majority of intratumoral CAR T cells expressed markers of T cell activation but, unexpectedly, constituted ≤5% of all T cells within the TME 5 days or more after therapy. Large numbers of T cells without CAR were also activated within the TME after axicabtagene ciloleucel infusion; these cells were positive for Ki-67, IFN-γ, granzyme B (GzmB), and/or PD-1 and were found at the highest levels in biopsies with CAR T cells. Additionally, non-CAR immune cells were the exclusive source of IL-6, a cytokine associated with cytokine release syndrome, and were found at their highest numbers in biopsies with CAR T cells. These data suggest that intratumoral CAR T cells are associated with non-CAR immune cell activation within the TME with both beneficial and pathological effects.

Assessment of denosumab treatment effects and imaging response in patients with giant cell tumor of bone.

BACKGROUND: Denosumab has been shown to reduce tumor size and progression, reform mineralized bone, and increase intralesional bone density in patients with giant cell tumor of bone (GCTB); however, radiologic assessment of tumors in bone is challenging. The study objective was to assess tumor response to denosumab using three different imaging parameters in a prespecified analysis in patients with GCTB from two phase 2 studies. METHODS: The studies enrolled adults and adolescents (skeletally mature and at least 12 years of age) with radiographically measurable GCTB that were given denosumab 120 mg every 4 weeks, with additional doses on days 8 and 15 of cycle 1. The proportion of patients with an objective tumor response was assessed using either Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST), European Organisation for Research and Treatment of Cancer response criteria (positron emission tomography [PET] scan criteria), or inverse Choi density/size (ICDS) criteria. Target lesions were measured by computed tomography or magnetic resonance imaging (both studies), PET (study 2 only), or plain film radiograph (study 2 only). RESULTS: Most patients (71.6%) had an objective tumor response by at least one response criteria. Per RECIST, 25.1% of patients had a response; per PET scan criteria, 96.2% had a response; per ICDS, 76.1% had a response. 68.5% had an objective tumor response ≥ 24 weeks. Using any criteria, crude incidence of response ranged from 56% (vertebrae/skull) to 91% (lung/soft tissue), and 98.2% had tumor control ≥ 24 weeks. Reduced PET avidity appeared to be an early sign of response to denosumab treatment. CONCLUSION: Modified PET scan criteria and ICDS criteria indicate that most patients show responses and higher benefit rates than modified RECIST, and therefore may be useful for early assessment of response to denosumab. TRIAL REGISTRATION: ClinicalTrials.gov Clinical Trials Registry NCT00396279 (retrospectively registered November 6, 2006) and NCT00680992 (retrospectively registered May 20, 2008).

Axicabtagene ciloleucel, a first-in-class CAR T cell therapy for aggressive NHL.

The development of clinically functional chimeric antigen receptor (CAR) T cell therapy is the culmination of multiple advances over the last three decades. Axicabtagene ciloleucel (formerly KTE-C19) is an anti-CD19 CAR T cell therapy in development for patients with refractory diffuse large B cell lymphoma (DLBCL), including transformed follicular lymphoma (TFL) and primary mediastinal B cell lymphoma (PMBCL). Axicabtagene ciloleucel is manufactured from patients' own peripheral blood mononuclear cells (PBMC) during which T cells are engineered to express a CAR that redirects them to recognize CD19-expressing cells. Clinical trials have demonstrated the feasibility of manufacturing axicabtagene ciloleucel in a centralized facility for use in multicenter clinical trials and have demonstrated potent antitumor activity in patients with refractory DLBCL. Main acute toxicities are cytokine release syndrome and neurologic events. Axicabtagene ciloleucel holds promise for the treatment of patients with CD19-positive malignancies, including refractory DLBCL.

Surgical downstaging in an open-label phase II trial of denosumab in patients with giant cell tumor of bone.

BACKGROUND: Surgical resection with curative intent for giant cell tumor of bone (GCTB) may be associated with severe morbidity. This interim analysis evaluated reduction in surgical invasiveness after denosumab treatment in patients with resectable GCTB. METHODS: Patients with primary or recurrent GCTB, for whom the initially planned surgery was associated with functional compromise or morbidity, received denosumab 120 mg subcutaneously every 4 weeks (additional doses on days 8 and 15 of the first cycle). Planned and actual GCTB-related surgical procedures before and after denosumab treatment were reported. Patients were followed for surgical outcome, adverse events, and recurrence following resection. RESULTS: Overall, 222 patients were evaluable for surgical downstaging (54 % were women; median age 34 years). Lesions (67 % primary and 33 % recurrent) were located in the axial (15 %) and appendicular skeleton (85 %). At the data cutoff date, most patients had not yet undergone surgery (n = 106; 48 %) or had a less morbid procedure (n = 84; 38 %) than originally planned. Median (interquartile range) time on denosumab was 19.5 (12.4-28.6) months for the 106 patients who had not undergone surgery and were continuing on monthly denosumab. Native joint preservation was 96 % (n = 24/25) for patients with planned joint/prosthesis replacement and 86 % (n = 30/35) for patients with planned joint resection/fusion. Of the 116 patients who had surgery (median postsurgical follow-up 13.0 [8.5-17.9] months), local recurrence occurred in 17 (15 %) patients. CONCLUSION: For patients with resectable GCTB, neoadjuvant denosumab therapy resulted in beneficial surgical downstaging, including either no surgery or a less morbid surgical procedure.

The UNC-6/Netrin receptors UNC-40/DCC and UNC-5 inhibit growth cone filopodial protrusion via UNC-73/Trio, Rac-like GTPases and UNC-33/CRMP.

UNC-6/Netrin is a conserved axon guidance cue that can mediate both attraction and repulsion. We previously discovered that attractive UNC-40/DCC receptor signaling stimulates growth cone filopodial protrusion and that repulsive UNC-40-UNC-5 heterodimers inhibit filopodial protrusion in C. elegans. Here, we identify cytoplasmic signaling molecules required for UNC-6-mediated inhibition of filopodial protrusion involved in axon repulsion. We show that the Rac-like GTPases CED-10 and MIG-2, the Rac GTP exchange factor UNC-73/Trio, UNC-44/Ankyrin and UNC-33/CRMP act in inhibitory UNC-6 signaling. These molecules were required for the normal limitation of filopodial protrusion in developing growth cones and for inhibition of growth cone filopodial protrusion caused by activated MYR::UNC-40 and MYR::UNC-5 receptor signaling. Epistasis studies using activated CED-10 and MIG-2 indicated that UNC-44 and UNC-33 act downstream of the Rac-like GTPases in filopodial inhibition. UNC-73, UNC-33 and UNC-44 did not affect the accumulation of full-length UNC-5::GFP and UNC-40::GFP in growth cones, consistent with a model in which UNC-73, UNC-33 and UNC-44 influence cytoskeletal function during growth cone filopodial inhibition.

Transcriptional regulation of murine IL-33 by TLR and non-TLR agonists.

IL-33, a member of the IL-1 family of cytokines, is produced by many cell types, including macrophages, yet its regulation is largely unknown. Treatment of primary murine macrophages with a panel of TLR (e.g., TLR2, TLR3, TLR4, and TLR9) agonists and non-TLR (e.g., MDA5, RIG-I) agonists revealed a pattern of gene and protein expression consistent with a role for IFN regulatory factor-3 (IRF-3) in the expression of IL-33. Accordingly, induction of IL-33 mRNA was attenuated in IRF-3(-/-) macrophages and TBK-1(-/-) mouse embryonic fibroblasts. Despite the fact that all IL-33 agonists were IRF-3 dependent, LPS-induced IL-33 mRNA was fully inducible in IFN-ß(-/-) macrophages, indicating that IL-33 is not dependent on IFN-ß as an intermediate. Epinephrine and Bordetella pertussis adenylate cyclase toxin (ACT), cAMP-activating agents, activate CREB and greatly synergize with LPS to induce IL-33 mRNA in macrophages. Both LPS-induced and ACT/LPS-enhanced expression of IL-33 mRNA was partially, but significantly, inhibited by the protein kinase A inhibitor H-89 but not by tyrosine kinase or protein kinase C inhibitors. Two IL-33 mRNA species derived from two alternative promoters encode full-length IL-33; however, the shorter "A" species is preferentially induced by all IL-33-inducing agonists except Newcastle disease virus, a RIG-I agonist that induced expression of both "A" and "B" transcripts. Together, these studies greatly extend what is currently known about the regulation of IL-33 induction in macrophages stimulated by bacterial and viral agonists that engage distinct innate immune signaling pathways.

The anti-tumor agent, 5,6-dimethylxanthenone-4-acetic acid (DMXAA), induces IFN-beta-mediated antiviral activity in vitro and in vivo.

The 2009 outbreak of pandemic H1N1 influenza, increased drug resistance, and the significant delay in obtaining adequate numbers of vaccine doses have heightened awareness of the need to develop new antiviral drugs that can be used prophylactically or therapeutically. Previously, we showed that the experimental anti-tumor drug DMXAA potently induced IFN-ß but relatively low TNF-α expression in vitro. This study confirms these findings in vivo and demonstrates further that DMXAA induces potent antiviral activity in vitro and in vivo. In vitro, DMXAA protected RAW 264.7 macrophage-like cells from VSV-induced cytotoxicity and moreover, inhibited replication of influenza, including the Tamiflu®-resistant H1N1 influenza A/Br strain, in MDCK cells. In vivo, DMXAA protected WT C57BL/6J but not IFN-ß(-/-) mice from lethality induced by the mouse-adapted H1N1 PR8 influenza strain when administered before or after infection. Protection was accompanied by mitigation of weight loss, increased IFN-ß mRNA and protein levels in the lung, and significant inhibition of viral replication in vivo early after DMXAA treatment. Collectively, this study provides data to support the use of DMXAA as a novel antiviral agent.

Macrophage proinflammatory response to Francisella tularensis live vaccine strain requires coordination of multiple signaling pathways.

The macrophage proinflammatory response to Francisella tularensis (Ft) live vaccine strain (LVS) was shown previously to be TLR2 dependent. The observation that intracellular Ft LVS colocalizes with TLR2 and MyD88 inside macrophages suggested that Ft LVS might signal from within the phagosome. Macrophages infected with LVSDeltaiglC, a Ft LVS mutant that fails to escape from the phagosome, displayed greatly increased expression of a subset of TLR2-dependent, proinflammatory genes (e.g., Tnf) but decreased expression of others (e.g., Ifnb1). This latter subset was similarly mitigated in IFN-beta(-/-) macrophages indicating that while Ft LVS-induced TLR2 signaling is necessary, cytosolic sensing of Ft to induce IFN-beta is required for full induction of the macrophage proinflammatory response. Although LVSDeltaiglC greatly increased IL-1beta mRNA in wild-type macrophages, protein secretion was not observed. IL-1beta secretion was also diminished in Ft LVS-infected IFN-beta(-/-) macrophages. rIFN-beta failed to restore IL-1beta secretion in LVSDeltaiglC-infected macrophages, suggesting that signals in addition to IFN-beta are required for assembly of the inflammasome and activation of caspase-1. IFN-beta plays a central role in controlling the macrophage bacterial burden: bacterial recovery was greater in IFN-beta(-/-) than in wild-type macrophages and treatment of Ft LVS-infected macrophages with rIFN-beta or 5,6-dimethylxanthenone-4-acetic acid, a potent IFN-beta inducer, greatly decreased the intracellular Ft LVS burden. In toto, these observations support the hypothesis that the host inflammatory response to Ft LVS is complex and requires engagement of multiple signaling pathways downstream of TLR2 including production of IFN-beta via an unknown cytosolic sensor and activation of the inflammasome.

IFN-beta-dependent inhibition of tumor growth by the vascular disrupting agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA).

By attacking established tumor vasculature, vascular disrupting agents (VDAs) represent an alternative approach to the treatment of cancer. One such VDA, 5,6-dimethylxanthenone-4-acetic acid (DMXAA), is scheduled for phase III trials for prostate and lung cancer in combination with conventional chemotherapies. In this work, we identify interferon-beta (IFN-beta) as a central mediator in the host's response to DMXAA. In mice bearing Lewis lung adenocarcinomas, a single intraperitoneal dose of DMXAA was shown to effect a highly significant reduction in tumor growth rate in wild-type mice that was not seen in IFN-beta-null mice. Moreover, intratumoral cytokine expression was shown to be dependent on host-derived IFN-beta, as DMXAA-treated IFN-beta-null mice demonstrated a lack of induction of not only IFN-beta but also the antiangiogenic cytokine, IP-10, in excised tumor tissue. These results support the conclusion that DMXAA derives its potent anticancer properties in part through elicitation of IFN-beta expression by host-derived elements.

The chemotherapeutic agent DMXAA potently and specifically activates the TBK1-IRF-3 signaling axis.

Vascular disrupting agents (VDAs) represent a novel approach to the treatment of cancer, resulting in the collapse of tumor vasculature and tumor death. 5,6-dimethylxanthenone-4-acetic acid (DMXAA) is a VDA currently in advanced phase II clinical trials, yet its precise mechanism of action is unknown despite extensive preclinical and clinical investigations. Our data demonstrate that DMXAA is a novel and specific activator of the TANK-binding kinase 1 (TBK1)-interferon (IFN) regulatory factor 3 (IRF-3) signaling pathway. DMXAA treatment of primary mouse macrophages resulted in robust IRF-3 activation and approximately 750-fold increase in IFN-beta mRNA, and in contrast to the potent Toll-like receptor 4 (TLR4) agonist lipopolysaccharide (LPS), signaling was independent of mitogen-activated protein kinase (MAPK) activation and elicited minimal nuclear factor kappaB-dependent gene expression. DMXAA-induced signaling was critically dependent on the IRF-3 kinase, TBK1, and IRF-3 but was myeloid differentiation factor 88-, Toll-interleukin 1 receptor domain-containing adaptor inducing IFN-beta-, IFN promoter-stimulator 1-, and inhibitor of kappaB kinase-independent, thus excluding all known TLRs and cytosolic helicase receptors. DMXAA pretreatment of mouse macrophages induced a state of tolerance to LPS and vice versa. In contrast to LPS stimulation, DMXAA-induced IRF-3 dimerization and IFN-beta expression were inhibited by salicylic acid. These findings detail a novel pathway for TBK1-mediated IRF-3 activation and provide new insights into the mechanism of this new class of chemotherapeutic drugs.

Murine antibody response to intranasally administered enterotoxigenic Escherichia coli colonization factor CS6.

Enterotoxigenic Escherichia coli (ETEC) is the most common cause of bacterial diarrhea worldwide and is an important cause of infant morbidity and mortality in developing nations. ETEC colonization factors (CF) are virulence determinants that appear to be protective antigens in humans and are the major target of vaccine efforts. One of the most prevalent CF, CS6, is expressed by about 30% of ETEC worldwide. This study was designed to compare the immunogenicity between encapsulated CS6 (CS6-PLG) and unencapsulated CS6. Recombinant CS6 was purified and encapsulated in biodegradable poly(DL-lactide-co-glycolide) (PLG) microspheres using current Good Manufacturing Practices (cGMP). CS6-PLG and CS6 were administered intranasally (IN) to BALB/c mice in three vaccinations 4 weeks apart. Enzyme linked immunosorbent assay (ELISA) was used to measure the anti-CS6 response in serum and mucosal secretions following each of the three inoculations. Mice vaccinated with two or three doses of CS6-PLG demonstrated a significantly greater rise in serum anti-CS6 IgG and mucosal IgA titer values than those immunized with two or three doses of CS6 alone. Three doses of CS6-PLG led to anti-CS6 serum IgG and mucosal IgA titer values 14-fold and 4.4-fold greater, respectively, than three doses of CS6 (P<0.02). IN administered CS6 to mice is safe and highly immunogenic either alone or when encapsulated in microspheres. PLG microsphere encapsulation of CS6 significantly augments the antibody response to that antigen when administered to a mucosal surface.

Safety and immunogenicity of a prototype enterotoxigenic Escherichia coli vaccine administered transcutaneously.

Transcutaneous immunization (TCI) is a new method for vaccine delivery that has been shown to induce immunity relevant to enteric disease vaccines. We evaluated the clinical safety and immunogenicity of a recombinant subunit vaccine against enterotoxigenic Escherichia coli (ETEC) delivered by TCI. Adult volunteers received patches containing the recombinant ETEC colonization factor CS6, either with heat-labile enterotoxin (LT) or patches containing CS6 alone. The vaccine was administered at 0, 1, and 3 months, and serum antibodies and antibody-secreting cells (ASCs) were assessed. Among the 26 volunteers that completed the trial, there were no responses to CS6 in the absence of LT. In the groups receiving both CS6 and LT, 68 and 53% were found to have serum anti-CS6 immunoglobulin G (IgG) and IgA, respectively; 37 and 42% had IgG and IgA anti-CS6 ASCs. All of the volunteers receiving LT had anti-LT IgG, and 90% had serum anti-LT IgA; 79 and 37% had anti-LT IgG and IgA ASCs. Delayed-type hypersensitivity (DTH), suggesting T-cell responses, was seen in 14 of 19 volunteers receiving LT and CS6; no DTH was seen in subjects receiving CS6 alone. This study demonstrated that protein antigens delivered by a simple patch could induce significant systemic immune responses but only in the presence of an adjuvant such as LT. The data suggest that an ETEC vaccine for travelers delivered by a patch may be a viable approach worthy of further evaluation.