Adjuvant-dependent effects on the safety and efficacy of inactivated SARS-CoV-2 vaccines during heterologous infection by a SARS-related coronavirus

Inactivated whole virus SARS-CoV-2 vaccines adjuvanted with aluminum hydroxide (Alum) are among the most widely used COVID-19 vaccines globally and have been critical to the COVID-19 pandemic response. Although these vaccines are protective against homologous virus infection in healthy recipients, the emergence of novel SARS-CoV-2 variants and the presence of large zoonotic reservoirs provide significant opportunities for vaccine breakthrough, which raises the risk of adverse outcomes including vaccine-associated enhanced respiratory disease (VAERD). To evaluate this possibility, we tested the performance of an inactivated SARS-CoV-2 vaccine (iCoV2) in combination with Alum against either homologous or heterologous coronavirus challenge in a mouse model of coronavirus-induced pulmonary disease. Consistent with human results, iCoV2 + Alum protected against homologous challenge. However, challenge with a heterologous SARS-related coronavirus, Rs-SHC014-CoV (SHC014), up to at least 10 months post-vaccination, resulted in VAERD in iCoV2 + Alum-vaccinated animals, characterized by pulmonary eosinophilic infiltrates, enhanced pulmonary pathology, delayed viral clearance, and decreased pulmonary function. In contrast, vaccination with iCoV2 in combination with an alternative adjuvant (RIBI) did not induce VAERD and promoted enhanced SHC014 clearance. Further characterization of iCoV2 + Alum-induced immunity suggested that CD4+ T cells were a major driver of VAERD, and these responses were partially reversed by re-boosting with recombinant Spike protein + RIBI adjuvant. These results highlight potential risks associated with vaccine breakthrough in recipients of Alum-adjuvanted inactivated vaccines and provide important insights into factors affecting both the safety and efficacy of coronavirus vaccines in the face of heterologous virus infections.

Host range, transmissibility and antigenicity of a pangolin coronavirus

The pathogenic and cross-species transmission potential of SARS-CoV-2-related coronaviruses (CoVs) remain poorly characterized. Here we recovered a wild-type pangolin (Pg) CoV GD strain including derivatives encoding reporter genes using reverse genetics. In primary human cells, PgCoV replicated efficiently but with reduced fitness and showed less efficient transmission via airborne route compared with SARS-CoV-2 in hamsters. PgCoV was potently inhibited by US Food and Drug Administration approved drugs, and neutralized by COVID-19 patient sera and SARS-CoV-2 therapeutic antibodies in vitro. A pan-Sarbecovirus antibody and SARS-CoV-2 S2P recombinant protein vaccine protected BALB/c mice from PgCoV infection. In K18-hACE2 mice, PgCoV infection caused severe clinical disease, but mice were protected by a SARS-CoV-2 human antibody. Efficient PgCoV replication in primary human cells and hACE2 mice, coupled with a capacity for airborne spread, highlights an emergence potential. However, low competitive fitness, pre-immune humans and the benefit of COVID-19 countermeasures should impede its ability to spread globally in human populations.

Anti-4-1BB immunotherapy enhances systemic immune effects of radiotherapy to induce B and T cell-dependent anti-tumor immune activation and improve tumor control at unirradiated sites

Radiation therapy (RT) can prime and boost systemic anti-tumor effects via STING activation, resulting in enhanced tumor antigen presentation and antigen recognition by T cells. It is increasingly recognized that optimal anti-tumor immune responses benefit from coordinated cellular (T cell) and humoral (B cell) responses. However, the nature and functional relevance of the RT-induced immune response are controversial, beyond STING signaling, and agonistic interventions are lacking. Here, we show that B and CD4+ T cell accumulation at tumor beds in response to RT precedes the arrival of CD8+ T cells, and both cell types are absolutely required for abrogated tumor growth in non-irradiated tumors. Further, RT induces increased expression of 4-1BB (CD137) in both T and B cells; both in preclinical models and in a cohort of patients with small cell lung cancer treated with thoracic RT. Accordingly, the combination of RT and anti-41BB therapy leads to increased immune cell infiltration in the tumor microenvironment and significant abscopal effects. Thus, 4-1BB therapy enhances radiation-induced tumor-specific immune responses via coordinated B and T cell responses, thereby preventing malignant progression at unirradiated tumor sites. These findings provide a rationale for combining RT and 4-1bb therapy in future clinical trials.

HDAC11 regulates expression of C/EBPβ and immunosuppressive molecules in myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) constitute a heterogeneous population of immature myeloid cells derived from bone marrow and negatively regulate both innate and adaptive immunity in the tumor microenvironment. Previously we have demonstrated that MDSCs lacking histone deacetylase 11 (HDAC11) displayed an increased suppressive activity against CD8+ T-cells. However, the mechanisms of HDAC11 that contribute to the suppressive function of MDSCs remain unclear. Here, we show that arginase activity and NO production is significantly higher in HDAC11 knockout MDSCs when compared with wild-type (WT) controls. In the absence of HDAC11, elevated arginase level and enzymatic activity were observed preferentially in the tumor-infiltrated granulocytic MDSCs, whereas iNOS expression and NO production were increased in the tumor-infiltrated monocytic MDSCs. Of note and for the first time, we demonstrated an association between the elevated expression of immunosuppressive molecules with up-regulation of the transcription factor C/EBPβ in MDSCs lacking HDAC11. Interestingly, the highest expression of C/EBPβ was observed among CD11b+ Gr-1+ MDSCs isolated from tumor-bearing mice. The additional demonstration that HDAC11 is recruited to the promoter region of C/EBPβ in WT MDSCs suggests a novel molecular mechanism by which HDAC11 influence the expression of immunosuppressive molecules in MDSCs through regulation of C/EBPβ gene expression.

Sexual Risk Behaviors Associated with Sexually Transmitted Infections in a US Military Population Living with HIV After the Repeal of "Don't Ask, Don't Tell"

Risk behaviors associated with sexually transmitted infections (STIs) among people living with HIV (PLWH) have not been well characterized in the US military. We identified risk behaviors associated with a new STI in this population after the repeal of "Don't Ask, Don't Tell." US Military HIV Natural History Study participants who completed the risk behavior questionnaire (RBQ) between 2014 and 2017 and had at least 1 year of follow-up were included (n = 1589). Logistic regression identified behaviors associated with incident STI in the year following RBQ completion. Overall, 18.9% acquired an STI and 52.7% reported condom use at last sexual encounter. Compared with those with no new sex partners, participants with between one and four or five or more new partners were 1.71 [1.25-2.35] and 6.12 [3.47-10.79] times more likely to get an STI, respectively. Individuals reporting low or medium/high perceived risk of STI were 1.83 [1.23-2.72] and 2.65 [1.70-4.15] times more likely to acquire a new STI than those reporting no perceived risk, respectively. Participants who preferred not to answer about sexual preference, number of new partners, or perceived STI risk were also more likely to acquire a new STI. Our study illustrates that despite regular access to health care and accurate perceptions of risk, rates of STI among PLWH remain high in the US military setting, as in others. Given the potential individual and public health consequences of STI coinfection after HIV, more work is needed to assess interventions aimed at sexual behavior change for PLWH.

Vaccine-Induced Skewing of T Cell Responses Protects Against Chikungunya Virus Disease

Chikungunya virus (CHIKV) infections can cause severe and debilitating joint and muscular pain that can be long lasting. Current CHIKV vaccines under development rely on the generation of neutralizing antibodies for protection; however, the role of T cells in controlling CHIKV infection and disease is still unclear. Using an overlapping peptide library, we identified the CHIKV-specific T cell receptor epitopes recognized in C57BL/6 infected mice at 7 and 14 days post-infection. A fusion protein containing peptides 451, 416, a small region of nsP4, peptide 47, and an HA tag (CHKVf5) was expressed using adenovirus and cytomegalovirus-vectored vaccines. Mice vaccinated with CHKVf5 elicited robust T cell responses to higher levels than normally observed following CHIKV infection, but the vaccine vectors did not elicit neutralizing antibodies. CHKVf5-vaccinated mice had significantly reduced infectious viral load when challenged by intramuscular CHIKV injection. Depletion of both CD4+ and CD8+ T cells in vaccinated mice rendered them fully susceptible to intramuscular CHIKV challenge. Depletion of CD8+ T cells alone reduced vaccine efficacy, albeit to a lesser extent, but depletion of only CD4+ T cells did not reverse the protective phenotype. These data demonstrated a protective role for CD8+ T cells in CHIKV infection. However, CHKVf5-vaccinated mice that were challenged by footpad inoculation demonstrated equal viral loads and increased footpad swelling at 3 dpi, which we attributed to the presence of CD4 T cell receptor epitopes present in the vaccine. Indeed, vaccination of mice with vectors expressing only CHIKV-specific CD8+ T cell epitopes followed by CHIKV challenge in the footpad prevented footpad swelling and reduced proinflammatory cytokine and chemokines associated with disease, indicating that CHIKV-specific CD8+ T cells prevent CHIKV disease. These results also indicate that a T cell-biased prophylactic vaccination approach is effective against CHIKV challenge and reduces CHIKV-induced disease in mice.

Influence of Blood Contamination on Bond Strength of a Self-Etching System

Objectives: To detect the influence of blood contamination (BC) on the bond strength (BS) of a selfetching bonding system (SES) to enamel and dentine.

Methods: 25 human molars were longitudinally sectioned on the mesio-distal axis in order to obtain 50 specimens, which were embedded in acrylic resin. At first, the specimens were ground to expose a flat surface of enamel, and a bond strength test was performed. Afterwards, the samples were ground again in order to obtain a flat surface of dentine. Ten groups (total: n=100) were assigned according to substrate (enamel and dentine), step in the bonding sequence when contamination occurred (before the acidic primer and after the bonding resin), and contamination treatment (dry or rinse and dry procedure). Fresh human blood was introduced either before or after SES application (Clearfil SE Bond) and treated with air drying, or by rinsing and drying following application. Composite resin (Filtek Z-250,3M ESPE) was applied as inverted, truncated cured cones that were debonded in tension.

Results: The mean tensile BS values (MPa) for enamel/dentine were 19.4/23.0 and 17.1/10.0 for rinse-and-dry treatment (contamination before and after SES, respectively); while the measurements for the dry treatment, 16.2/23.3 and 0.0/0.0 contamination before and after SES, respectively.

Conclusions: It was determined that blood contamination impaired adhesion to enamel and dentine when it occurred after bond light curing. Among the tested contamination treatments, the rinseand- dry treatment produced the highest bond strength with BC after SES application, but it was not sufficient to recover the BS in the contamination-free group. (Eur J Dent 2010;4:280-286)

Abstract LB-074: Priming the tumor microenvironment with epigenetic modifiers to overcome resistance to immune checkpoint inhibitors

Histone deacetylases (HDACs) are involved in diverse cellular regulatory mechanisms including functions outside the chromatin environment. Several publications have demonstrated that selective HDAC inhibitors (HDACi) can influence tumor immunogenicity and the functional activity of specific immune cells. In particular, the selective inhibition of HDAC6 has been reported to decrease tumor growth in several malignancies. However, there is still no clarity about the cellular components mediating this effect. In this study, we evaluated the immunological modulation of the HDAC6i Nexturastat A in combination with anti-PD-1 checkpoint blockade therapy and the use of this HDAC6i as a priming agent to facilitate the transition of the tumor microenvironment from “cold” to “hot” in order to more specifically augment immune check-point blockade therapies. This combination of Nexturastat A and anti-PD-1 therapy demonstrated a significant reduction of tumor growth in syngeneic melanoma tumor animal models. Additionally, we observed a complete neutralization of the up-regulation of PD-L1 and other immunosuppressive pathways induced by the treatment with anti-PD-1 blockade. This combination also showed that the pre-treatment with selective HDAC6i induced major changes in the tumor microenvironment such as enhanced infiltration of immune cells, increased central and effector T cell memory, and a significant reduction of pro-tumorigenic M2 macrophages. The evaluation of the effect of HDAC6i on individual immune components suggest that the in vivo anti-tumor activity of HDAC6i is mediated by its effect on tumor cells and tumor associated macrophages, and not directly over T cells. Overall, our results indicate that selective HDAC6i could be used as immunological priming agents to sensitize immunologically “cold” tumors and subsequently improve ongoing immune check-point blockade therapies.

Note: This abstract was not presented at the meeting.

Citation Format: Tessa J. Knox, Eva Sahakian, Debarati Banik, Melissa Hadley, Erica Palmer, Jennifer Kim, Satish Noonepalle, John Powers, Maria Gracia-Hernandez, Vasco Oliveira, Fengdong Cheng, Jie Chen, Cyril Barinka, Javier Pinilla-Ibarz, Norman Lee, Alan Kozikowski, Alejandro Villagra. Priming the tumor microenvironment with epigenetic modifiers to overcome resistance to immune checkpoint inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-074.

Abstract 4723: Combinatorial efficacy of anti-PD1 treatment and selective histone deacetylase 6 (HDAC6) inhibition in chronic lymphocytic leukemia (CLL)

A suppressive microenvironment allows CLL B cells to avoid immune surveillance. Coinhibitory antigens, anti-inflammatory cytokines and skewed immune populations support malignancy and contribute to poorer immune responses in CLL patients. Novel approaches to counter immunosuppression are therefore being explored. The HDAC family of proteins epigenetically regulate immune-related pathways in cancer and may be noteworthy immunomodulatory targets. In addition to the recognized role of HDACs in cell survival, HDACi may alter inflammatory status of immune and tumor cells. We have previously reported that HDAC6 regulates IL-10 transcription, and is responsible for T cell anergy in murine and human APCs. IL-10 is secreted by CLL B cells and is thought to influence immunosuppression. Therefore, we hypothesized that HDAC6i could reverse immunosuppression in CLL for antitumor benefit. The purpose of this study was to determine 1) the effects of selective HDAC6i on CLL immune biology and 2) whether combination with HDAC6i could improve efficacy of anti-PD1 for CLL therapy.

To accomplish these aims, the euTCL1 and euTCL1/HDAC6KO adoptive transfer models of murine CLL were utilized. ACY738 (selective HDAC6i) was administered orally in chow at 25mpk daily. Anti-PD1 was administered intraperitoneally 3x per week at 3mpk. CLL surface antigens were analyzed via flow cytometry. Functional mixed lymphocyte assays were performed ex vivo, measuring IFNg production, and Th1/Th2 factors were examined via qRT-PCR in CLL T cells.

Early PD-L1 expression on B cells correlated to CLL burden in euTCL1 mice. Post ACY738 treatment, euTCL1 B cells downregulated expression of PD-L1 and plasma IL-10. In addition, PD-1 and CTLA4 was decreased on CD4+, CD8+, Tregs and effector memory T cells. Splenic T cells from ACY738 mice upregulated TBET and downregulated GATA3, indicative of a less exhausted phenotype. Subsequently, euTCL1 B cells were treated ex vivo with ACY738 and cocultured with T cells. T cell activation (IFNg production) was increased after coculture with treated B cells compared to control B cells. We then hypothesized that ACY738 could be rationally be combined with anti-PD1 mAb for CLL treatment. Mice treated with anti-PD1 accumulated fewer CD5+ B cells, confirming that PD-1/PD-L1 blockade demonstrated anti-CLL benefit. Strikingly, combination of ACY738 and anti-PD1 further delayed the growth of CLL cells compared to either single agent. Consistently, anti-PD1 treatment in euTCL1/HDAC6KO mice further delayed CLL development. In conclusion, we report here that HDAC6i can reinvigorate CLL T cells, and combination of HDAC6i with anti-PD1 increased anti-CLL efficacy in vivo. This work provides evidence that this combination could be clinically investigated to simultaneously reduce tumor burden and improve immune function in CLL patients.

Citation Format: Kamira Maharaj, John Powers, Alex Achille, Eva Sahakian, Javier Pinilla-Ibarz. Combinatorial efficacy of anti-PD1 treatment and selective histone deacetylase 6 (HDAC6) inhibition in chronic lymphocytic leukemia (CLL) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4723.

A phase I clinical trial of ruxolitinib in combination with nilotinib in chronic myeloid leukemia patients with molecular evidence of disease

PURPOSE

Preclinical evidence indicates that the bone marrow microenvironment provides a protective niche for leukemic stem cells, allowing them to evade the effects of BCR-ABL tyrosine kinase inhibitors (TKIs), but that targeting of the JAK-STAT pathway with the JAK2 inhibitor ruxolitinib increases TKI-induced apoptosis. A phase I clinical trial (NCT01702064) investigated the tolerability and safety of treating chronic-phase chronic myeloid leukemia patients with ruxolitinib in combination with the BCR-ABL TKI nilotinib and explored initial efficacy evidence.

EXPERIMENTAL DESIGN

Eleven patients already treated with single-agent nilotinib (300-400 mg twice daily) commenced combination therapy, and molecular responses were evaluated after 6 months. Three ruxolitinib dose cohorts were studied: 5 mg, 10 mg, and 15 mg twice daily.

RESULTS

One patient experienced a grade 3/4 adverse event (hypophosphatemia) and 36% of patients experienced grade 1/2 anemia. Of 10 patients who were evaluable for responses, 40% had undetectable BCR-ABL transcripts, as measured by quantitative RT-PCR after 6 months. Plasma inhibitory assay results revealed a decrease in phospho-STAT3 levels after treatment with ruxolitinib. The recommended phase 2 dose of ruxolitinib was 15 mg BID.

CONCLUSIONS

Overall, this combination was safe and well-tolerated, and the molecular responses were encouraging, thereby warranting further investigation in a phase 2 trial.

Abstract 1703: The HDAC6 inhibitor Nexturastat A improves in vivo PD-1 immune blockade

The role of HDACs in cell biology, initially limited to their effects upon histones, now encompasses more complex regulatory functions that vary with their tissue expression, cellular compartmentalization and stage of cellular differentiation. Several recent studies have shown that selective HDAC inhibitors (HDACi) are able to impair in vivo tumor growth. Therefore, there is an emerging interest in the understanding of the molecular mechanisms mediating these anti-tumor properties. In this context, a number of recent publications have demonstrated that the selective inhibition of specific HDACs enhances tumor immunogenicity in a wide variety of tumors, thereby preventing tumor escape and improving immune surveillance. Our group has focused on HDAC6, and shown that both the genetic abrogation and pharmacological inhibition of this HDAC modulates the expression of a variety of immune-regulatory proteins in the tumor microenvironment, including PD-L1, PD-L2, MHC class I, B7-H4 and TRAIL-R1. In particular, we have previously demonstrated that both pharmacological inhibition and/or genetic abrogation of HDAC6 plays a critical role in the immune check point blockade by down-regulating the expression of PD-L1. Moreover, we have also shown that in vivo inhibition of HDAC6 reduces tumor growth in B16 and SM1 murine melanoma models within syngeneic immunocompetent hosts. Additionally, we have found that the combination of the HDAC6i Nexturastat A (NextA) and checkpoint PD-1 immune blockade therapy results in an important improvement in anti-tumor immune responses as evidenced by the reduction of tumor growth when compared to treatment with individual stand-alone agents. Moreover, our data has shown an increase in CD8+, NK+ cell infiltration of tumors treated with the combination therapy versus either standalone treatment. Further analysis of in vivo immune tumor infiltration evidenced that the treatment with NextA importantly diminished the macrophage M2 phenotype in the tumor microenvironment. An outcome that was also observed in combination with PD-1 immune blockade. Lastly, we have found that the anti-PD-1/NextA in vivo combination therapy reduces the expression of PD-L1, PD-L2 and other negative check-point pathways. However, the HDAC6 inhibition has a minimal effect over the expression of their respective counterparts in T cells (i.e. PD-1). Overall, we have found that HDAC6i could be used as a potential adjuvant in ongoing therapeutic options involving immune check-point blockade.

Citation Format: Tessa Knox, Eva Sahakian, Debarati Banik, Melissa Hadley, Erica Palmer, Jennifer Kim, John Powers, Sarthak Shah, Alexa Lowe, Javier Pinilla, Eduardo Sotomayor, Norman Lee, Alan Kozikowski, Alejandro V. Villagra. The HDAC6 inhibitor Nexturastat A improves in vivo PD-1 immune blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1703.

Abstract 4967: HDAC11 function as a transcriptional regulator in immature myeloid cells to myeloid-derived suppressor cells transition

In normal myelopoiesis, immature myeloid cells (IMCs) differentiate into macrophages, neutrophils or dendritic cells, a process that is tightly controlled by transcription factors and epigenetic regulators. However, under tumor burden, IMCs differentiate into myeloid derived suppressor cells (MDSCs) and with subsequent up-regulation of immune suppressive factors and a pro-tumor effect. In prior studies, we found that MDSCs from HDAC11 KO mice displayed an increased T-cell suppressive activity that was associated with a more aggressive tumor growth as compared to MDSCs from wild type control mice. Unlike MDSC's in which absence of HDAC11 is associated with a suppressive phenotype, T-cell lacking HDAC11 are hyper-reactive and endowed with strong antitumor activity. To assess which phenotype will be the dominant one in vivo, we performed adoptive immune cell transfer experiments of MDSC and/or T-cells from HDAC11 KO mice into C57BL/6 tumor-bearing mice. The transfer of HDAC11KO MDSCs was able to eliminate, at least partially, the anti-tumor effect elicited by the adoptive transfer of HDAC11KO T cells.

Mechanistically we have found that MDSCs lacking HDAC11 displayed up-regulation of expression and enzymatic activity of arginase 1 and Nos2, two enzymes that are crucial in regulating MDSCs suppressive function. The aberrant enzymatic activities of Arg1 and Nos2 in HDAC11KO MDSCs correlate with over-expression of the lineage-specific transcription factor C/EBPβ, which has been shown to be essential for the differentiation of functional MDSCs. Furthermore, ChIP analysis confirmed that HDAC11 is recruited to the C/EBPβ gene promoter where exerts a negative regulatory effect upon gene transcription.

Taken together, we have uncovered a previously unknown role for HDAC11 as a transcriptional regulator of MDSCs function. A better understanding of this novel role of HDAC11 in myeloid biology will lead to targeted epigenetic therapies to manipulate the suppressive effect of these immunoregulatory cells.

Citation Format: Jie Chen, Fengdong Cheng, Eva Sahakian, John Powers, Zi Wang, Alejandro Villagra, Javier Pinilla-Ibarz, Eduardo M. Sotomayor. HDAC11 function as a transcriptional regulator in immature myeloid cells to myeloid-derived suppressor cells transition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4967.

Abstract 4055: Enhancing anti-PD-1 immune blockade in melanoma through selective inhibition of histone deacetylase 6

Histone deacetylases (HDACs), were originally described in a limited context as histone modifiers. New evidence has demonstrated that HDACs are also involved in a diverse range of cellular processes that are not restricted to the chromatin environment, such as the regulation of the cell cycle/apoptosis and, more recently, a modulator of immune response. However, much remains unknown about the mechanism of action of HDACs and their roles in the immune-biology of cancer. The non-specific nature of pan-HDAC inhibitors results in a narrow therapeutic window of use, limiting the dose and duration due to toxicity. Our group has focused in one specific HDAC, HDAC6, and shown that both the genetic abrogation and pharmacological inhibition of this HDAC modulates the expression of a variety of immune-regulatory proteins in the tumor microenvironment, including PD-L1, PD-L2, MHC class I, B7-H4 and TRAIL-R1. In particular, we have previously demonstrated that both pharmacological inhibition and/or genetic abrogation of HDAC6 plays a critical role in the immune check point blockade by down-regulating the expression of PD-L1 and other check-point modulators such as PD-L2, B7-H4, etc. Moreover, we have also observed that in vivo inhibition of HDAC6 reduces tumor growth in B16 and SM1 murine melanoma models within syngeneic immunocompetent hosts. Additionally, we have found that the combination of low doses of the HDAC6i Nexturastat A and checkpoint immune blockade, including anti-PD-1 and anti-CTLA4, results in an important improvement in anti-tumor immune responses as evidenced by the reduction of tumor growth when compared to treatment with individual stand-alone agents. In these studies we also evidenced an increased production of IFNγ and IL-2 in the stand-alone check-point inhibitor treatments, which leads to an upregulation of PD-L1 and PD-L2. Similar levels of IFNγ and IL-2 were found in the combination groups. However, the expression level of PD-L1 and PD-L2 were comparable to the non-treated group. Taking all together, we have found that HDAC6i could be used as a potential adjuvant in ongoing therapeutic options involving immune check-point blockade.

Citation Format: Tessa Knox, Eva Sahakian, Jayakumar Nair, Jennifer Kim, Debarati Banik, Melissa Hadley, John Powers, Fengdong Cheng, Sida Shen, Javier Pinilla, Jeffrey Weber, Alan Kozikowski, Eduardo Sotomayor, Alejandro Villagra. Enhancing anti-PD-1 immune blockade in melanoma through selective inhibition of histone deacetylase 6 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4055. doi:10.1158/1538-7445.AM2017-4055

Evaluation of a "walk-through" ladder top design during ladder-roof transitioning tasks

This study evaluated the effect of an extension ladder "walk-through" top design on kinetic and kinematic behaviors and the outward destabilizing forces induced on the ladder during transitioning at elevation. Thirty-two male participants performed stepping tasks between a ladder top and a roof at simulated elevation in a surround-screen virtual-reality system. The experimental conditions included a "walk-through" and a standard ladder top section supported on flat and sloped roof surfaces. Three force platforms were placed under the ladder section and in the roof to measure propulsion forces during transitions. A motion measurement system was used to record trunk kinematics. The frictional demand at the virtual ladder base was also calculated. The results indicate that under optimal ladder setup (angle 75.5 °), the frictional demand at the ladder base remains relatively small for all experimental conditions. Also, the "walk through" ladder top eased the ladder-to-roof transitions but not the roof-to-ladder transitions.

Evaluating Anti-Infective Drugs in the Resistant Pathogen Setting: Can we Use External Controls?

Decreased efficacy of antibiotics due to resistant pathogens has created a need for the development of more effective medical interventions. Despite the increasing prevalence of pathogens resistant to one or more drugs, identifying and enrolling participants into clinical trials that evaluate new interventions for the treatment of some diseases can be challenging given the low prevalence of disease in which there are no effective treatments. Thus researchers might be tempted to consider externally-controlled trials that may allow for a reduction of the necessary number of prospectively-identified trial participants, thus easing recruitment burden and resulting in more timely trial completion relative to randomized controlled trials. We discuss advantages and disadvantages in externally controlled trials and review requirements for a valid externally-controlled trial. As ECTs are subject to the bias of observational studies, the criteria for a valid ECT should be carefully evaluated before these designs are implemented. Given considerable variation in study results in the resistant pathogen setting, the lack of information on important patient characteristics that may confound estimates of treatment effects, as well as the improvements in medical practice and evolving antibiotic resistance, the use of ECTs in the resistant pathogen setting, is not recommended. ECTs should be should be limited to specific situations where superiority of the effect of the new intervention is dramatic, the usual course of the disease highly predictable, the endpoints are objective (e.g., all-cause mortality) and the impact of baseline and treatment variables on outcomes is well characterized. Given that the resistant pathogen setting does not satisfy these criteria, we conclude that that randomized clinical trials are needed to evaluate new treatments for resistant pathogens. Innovative approaches to trial design that may ease recruitment burden while evaluating the benefits and harms of new treatments are being developed and utilized.

Abstract 2331: HDAC6, new role as master regulator of PD-L1 and immune-related pathways

Histone deacetylases (HDACs), originally described as histone modifiers, have more recently been demonstrated to modify a variety of other proteins involved in diverse cellular processes unrelated to the chromatin environment, including the modulation of proteins related to cell cycle/apoptosis and immune regulation. In contrast to the well-documented effects of HDAC inhibitors (HDACi) in the control of cell cycle and apoptosis, their role in immunobiology is still not completely understood, and the reported immunological outcomes when using HDACi are heterogeneous. Our group recently reported that the pharmacological or genetic abrogation of a single HDAC, HDAC6, modulates the expression of immuno-regulatory proteins, including PD-L1, PD-L2, MHC class I, B7-H4 and TRAIL-R1. We primarily focused in PD-L1, which is an important negative regulator of T-cell function and often over-expressed in cancer cells. In a mechanistic point of view, we have found that the pharmacological inhibition and genetic abrogation of HDAC6 inactivates the STAT3 pathway, impairs the nuclear translocation and the recruitment of STAT3 to the PD-L1 promoter and subsequently down-regulates the expression of PD-L1. Moreover, the in vivo abrogation of HDAC6 reduces tumor growth in melanoma models, effect that is enhanced in the presence of the immune check-point blocking antibodies anti-PD-1 and anti-CTLA4. These results provide a key pre-clinical rationale and justification to further study isotype selective HDAC6 inhibitors as potential immunomodulatory agents in cancer.

Citation Format: Tessa Knox, Maritza Lienlaf, Patricio Perez, Mibel Pabon, Calvin Lee, Fengdong Cheng, Eva Sahakian, John Powers, Susan Deng, Smalley Keiran, Alan Kozikowski, Javier Pinilla, Amod Sarnaik, Ed Seto, Jeffrey Weber, Eduardo Sotomayor, Alejandro Villagra. HDAC6, new role as master regulator of PD-L1 and immune-related pathways. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2331.

Abstract 4485: Regulation of chronic lymphocytic leukemia (CLL) immunobiology by histone deacetylase 6 (HDAC6)

In CLL, an immunosuppressive phenotype enables the malignant B cell to evade immune detection leading to immune suppression. In recent years, epigenetic changes prompted by proteins known as histone deacetylases (HDACs) have gained special attention predominantly because of their active role in the regulation of pathogenesis and immune-related pathways in CLL; though the precise mechanism by which these regulatory events take place has yet to be elucidated. In addition to the well-recognized role of histone deacetylase inhibitors (HDACi) in the control of cell cycle and apoptosis, HDACi have a potential role in modulating the immunobiology of CLL. Remarkably, HDACi alter the inflammatory status of immune cells and tumor cells themselves. Among the family of HDACs, we have recently demonstrated that HDAC6 has a regulatory role in transcriptional regulation of IL-10, and is responsible for T cell anergy in murine and human antigen presenting cells.

Activation of T-cells is predominantly dependent on both co-stimulatory and co-inhibitory molecules, including PD-1/PD-L1 as well as CTLA4-B7, OX40-OX40L, CD40-CD154, GAL9-TIM3, and 41BBL/41BB. Furthermore, most of these molecules have been identified to have epigenetically induced changes in expression.

Previously we had reported that expression of HDAC6 is increased in CLL patient samples. Recent studies from our lab show that selective HDAC6 inhibitors modify the expression of immunomodulatory molecules, which may ultimately lead to increases in the immunogenicity of CLL. Thus far, findings from our lab reveal that CLL cells treated with HDAC6i show 1) a dose dependent cell kill, 2) a reduction of IL-10—an important cytokine in the regulation of cell proliferation in CLL, and 3) synergistic reduction of viability when combined with the BTK inhibitor ibrutinib. Subsequently, we have also demonstrated that MEC2-HDAC6KD cells exhibit an increase in MHCII and a decrease in PD-L1 expression. Interestingly, we also observed a decrease in the expression of PD-L1 and other immune checkpoint markers in CLL cell lines treated with low-doses of HDAC6i. Additionally, malignant B cells isolated from euTCL1 mice and treated ex vivo with HDAC6i become more immunogenic and elicit greater type I allogeneic T cell immune response. Lastly, utilizing our in vivo CLL murine models (euTCL1, and euTCL1-HDAC6KO), we have been able to demonstrate a reduction in circulating lymphocytes in euTCL1-HDAC6KO, as well as euTCL1 mice receiving systemic administration of HDAC6i.

In conclusion, selective inhibition of HDAC6 in CLL results in the reduction of co-inhibitory molecules, dose dependent increases in cell killing as single treatment as well as strong synergy when combined with ibrutinib. These findings could provide a successful combination immunotherapeutic strategy for the treatment of CLL.

Citation Format: Eva Sahakian, Kamira Maharaj, John Powers, Renee M. Fonesca, Susan Deng, Javier Pinilla-Ibraz, Steven N. Quayle, Simon S. Jones. Regulation of chronic lymphocytic leukemia (CLL) immunobiology by histone deacetylase 6 (HDAC6). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4485.

Results of a phase II study of lenalidomide and rituximab for refractory/relapsed chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is an incurable disease in need of new therapeutic strategies. The immunomodulatory agent, lenalidomide, has shown activity as salvage therapy for CLL. In this phase II trial, we combined lenalidomide with rituximab in 25 patients (range, 41-79) with refractory/relapsed CLL. Lenalidomide was administered orally on escalating doses, with cycle 1 doses of 2.5mg daily on days 1-7, 5mg on days 8-14, and 10mg on days 15-21 followed by 7days off. On cycle 2 and beyond, lenalidomide was administered at 20mg daily on days 1-21. Rituximab was administered at 375mg/m(2) intravenously on a weekly basis for the first cycle starting on day 15 for 4 doses, with each cycle being 28days. Treatment was continued until disease progression or toxicity. Overall response rate was 45.8% on intent-to-treat and 61.1% in evaluable patients (all partial responses). Median time to treatment failure was 14.3 months for evaluable patients, and median overall survival was not reached. The most common grade 3/4 toxicity was neutropenia (72% of patients). The most common nonhematologic toxicity was infection (29% of patients). Lenalidomide combined with rituximab showed activity in heavily treated refractory CLL with an acceptable toxicity profile.

Abstract P2-09-01: Patient reported outcomes of multiplex breast cancer susceptibility testing utilizing a tiered-binned counseling and informed consent model in BRCA1/2 negative patients

Background:The risks, benefits and utilities of multiplex panels for breast cancer susceptibility are unknown and new counseling and informed consent models are needed. We sought to obtain patient reported outcomes of multiplex testing in BRCA1/2 negative patients utilizing a novel, previously piloted tiered-binned counseling model for multiplex testing. Methods:BRCA1/2 negative participants completed pre(V1) and post-test counseling(V2) and surveys evaluating cognitive, affective and behavioral responses to a 25-gene multiplex testing panel. We used linear regressions with estimation by GEE where appropriate. Results:376 patients have been approached. To date, 124 participants(33%) have consented to the study, 21(6%) declined and 231(61%) are considering. Of 95 who have completed pre-test counseling(V1), 88(93%) elected to proceed with 25-gene panel testing and (81%) were classified as making an informed choice after tiered-binned counseling. 6/53(11%) participants received a positive result, including 1 mutation in MSH2 and 5 in moderate penetrance genes (2 ATM, 1 BARD1, 1 CHEK2, 1 PALB2). 22/53(42%) participants received a variant of unknown significance(VUS). General anxiety and perceived utility decreased significantly with pre-test counseling and after results (Table 1). Knowledge increased with pre-test counseling; cancer worry increased after receipt of multiplex results. Higher cancer worry was associated only with lower income (2.6 points/income category, p<0.01). Those with a VUS had greater decreases in perceived utility compared to negative (p=0.01) or positive (p=0.003) results. To date, there are no other significant differences in knowledge, distress or uncertainty by test result. Medical management recommendations for the proband changed in 3/6 with a positive result. Cascade testing in the family was discussed as an option in 3/6 with a positive result. Conclusions:Many BRCA1/2-negative patients proceed with 25-gene cancer susceptibility testing if offered and most make informed choices utilizing a tiered-binned genetic counseling model. The tiered-binned counseling model is associated with increased knowledge, decreases in general anxiety and uncertainty after pre-test counseling and disclosure of results, but an increase in cancer worry after result disclosure. The clinical utility, long-term outcomes and differences in patient reported outcomes by test result remain unknown.

Table 1 Baseline, Mean(SD)After V1, Mean(SD)After V2, Mean(SD) N=75ˆ;N=49ˆˆN=75ˆ;N=49ˆˆN=49ˆˆGeneral Anxiety (range 0-21)6.4(3.9)*;6.9(3.9)**6.0(4.3)*;6.6(4.2)**5.8(4.5)**General Depression (range 0-212.8(2.9);3.1(3.2)3.0(3.5);3.1(3.6)3.0(3.7)State Anxiety (range 20-80)35.5(11.2);36.6(11.9)35.5(11.8);36.8(11.9)36.1(12.2)Cancer Worry (range 0-75)18.2(13.5);20.1(13.8)**16.7(12.5);17.2(11.9)**21.0(13.9)**Knowledge (range 17-82)65.7(5.0)**;66.5(5.0)**68.0(5.7)**;68.4(5.6)**67.3(4.9)**Uncertainty (range 0-15)5.8(3.9);6.2(4.3)5.6(3.7);5.4(3.2)5.6(3.5)Perceived Utility (range 24-120)75.2(14.0)*;75.9(14.0)**73.0(14.1)*;74.1(13.4)**68.4(16.9)***p≤0.05 **p≤0.01. ˆcompleted V1. ˆˆcompleted V1 & V2. To date, 53 have received results and 49 have completed post-disclosure surveys.

Citation Format: Bradbury AR, Patrick-Miller L, Egleston BE, Maxwell KN, Brandt A, Brower J, DiGiovanni L, Long JM, Powers J, Stopfer J, Nathanson KL, Domchek SM. Patient reported outcomes of multiplex breast cancer susceptibility testing utilizing a tiered-binned counseling and informed consent model in BRCA1/2 negative patients. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-09-01.

Functional Analysis of Histone Deacetylase 11 (HDAC11)

The physiological role of histone deacetylase 11 (HDAC11), the newest member of the HDAC family, remained largely unknown until the discovery of its regulatory function in immune cells. Among them, the regulation of cytokine production by antigen-presenting cells and the modulation of the suppressive ability of myeloid-derived suppressor cells (MDSCs) (Sahakian et al. Mol Immunol 63: 579-585, 2015; Wang et al. J Immunol 186: 3986-3996, 2011; Villagra et al. Nat Immunol 10: 92-100, 2009). Our earlier data has demonstrated that HDAC11, by interacting at the chromatin level with the IL-10 promoter, downregulates il-10 transcription in both murine and human APCs in vitro and ex vivo models (Villagra et al. Nat Immunol 10: 92-100, 2009). However the role of HDAC11 in other cell types still remains unknown. Here we present several methods that can potentially be used to identify the functional role of HDAC11, assigning special attention to the evaluation of immunological parameters.