Novel PE and APC tandems: Additional near-infrared fluorochromes for use in spectral flow cytometry

Recent advances in flow cytometry instrumentation and fluorochrome chemistries have greatly increased fluorescent conjugated antibody combinations that can be used reliably and easily in routine experiments. The Cytek Aurora flow cytometer was first released with three excitation lasers (405, 488, and 640 nm) and incorporated the latest Avalanche Photodiode (APD) technology, demonstrating significant improvement in sensitivity for fluorescent emission signals longer than 800 nm. However, there are limited commercially available fluorochromes capable of excitation with peak emission signals beyond 800 nm. To address this gap, we engineered six new fluorochromes: PE-750, PE-800, PE-830 for the 488 nm laser and APC-750, APC-800, APC-830 for the 640 nm laser. Utilizing the principal of fluorescence resonance energy transfer (FRET), these novel structures were created by covalently linking a protein donor dye with an organic small molecule acceptor dye. Additionally, each of these fluorochrome conjugates were shown to be compatible with fixation/permeabilization buffer reagents, and demonstrated acceptable brightness and stability when conjugated to antigen-specific monoclonal antibodies. These six novel fluorochrome reagents can increase the numbers of fluorochromes that can be used on a spectral flow cytometer.

Perspectives on psychedelic treatment and research in eating disorders: a web-based questionnaire study of people with eating disorders

Approximately 1.25 million people in the UK suffer from an eating disorder, yet the treatment options show limited efficacy, warranting the need for novel approaches. This study aimed to investigate the perspectives of people with eating disorders on the use of complementary therapies and psychedelic research and treatment. Two hundred participants with eating disorders took part in this web survey study. The majority of participants (70%) had used a complementary treatment to manage their eating disorder. Participants believed that psychedelic research was worthwhile in the context of a moderate level of concern. The most popular solutions to meet these concerns included providing education around psychedelics and their effects and use in psychiatry and experiencing endorsement from professionals in the area. Moreover, participant responses emphasized the need for a safe, monitored environment and the patient-therapist rapport in the context of psychedelic treatment. The findings are explored concerning future trials of psychedelics as a treatment for eating disorders.

Abstract 1615: Evaluation of efficacy metrics for in vivo experiments with immuno-oncology therapeutic agents

INTRODUCTION In vivo efficacy studies play an important role in the discovery of novel immuno-oncology (IO) therapeutics. Using syngeneic mice or humanized mice as mouse models, in vivo efficacy studies demonstrate the first handed evidence for anti-cancer activities of a drug. A variety of efficacy metrics, including tumor growth inhibition (TGI), growth rate, tumor response rate, time to tumor progression (TTP) and area under the curve (AUC), have been used to determine in vivo efficacy in literature. We set out to evaluate the efficacy metrics for assessing the in vivo activities of the IO therapeutic agents.

METHODS A linear mixed effects model based on normalized tumor volumes is used to estimate the growth rate of each treatment arm and test if the growth rates between two treatment arms are significantly different. Tests of TGI at the last time point and the time point where TGI reached the maximum are compared with the growth rate tests. Tumor response, including a complete regression (CR), partial regression (PR), or stable response (SR) are defined based on the tumor volume changes compared to the baseline. Overall response (OR) is the summation of CR, PR and SR. Fisher's exact tests are used to obtain a p-value comparing the tumor responses between two treatment arms. The TTP with a reasonable tumor size limit is calculated and tested. Time to complete regression (TTCR) is calculated to reflect the time it takes for the tumor to achieve complete regression. The AUC based on the normalized tumor volume data is applied without an assumption of log linear distribution of the tumor volume data. With multiple in vivo experiment data sets focusing on different targets, the results from all metrics are compared against each other. Power and sample size are estimated for the key metrics as well.

RESULTS To differentiate between two treatment arms, TGI at the last time points is mostly consistent with growth rate results. Growth rate tests appear to be more powerful than tumor response, TTP, and TTCR, while AUC tests are consistent with growth rate tests for the data we evaluated. AUC, as a nonparametric metric, appears to be more robust when the variability among individual tumor growth curves is relatively large and the log linear growth curve assumption for the growth rate model is severely violated. Based on growth rate or AUC tests together with last time point TGI, most of the in vivo experiments we evaluated are well powered with 8~10 mice per treatment group.

CONCLUSIONS Growth rate tests or AUC tests and last time point TGI are the recommended efficacy metrics to determine and report the efficacy of a novel IO agent in an in vivo experiment. Other metrics, such as tumor response, TTP and TTCR, can provide additional details of the response spectrum to the IO agent, and therefore would be useful to be included as well.

Citation Format: Chun Zhang, Yan Sun, Hamsell M. Alvarez, Yoshiko Akamatsu, Fiona Harding, Siu Sze Tan, Melvin Fox, Margo Werner, Nicole Belmar, Shiming Ye. Evaluation of efficacy metrics for in vivo experiments with immuno-oncology therapeutic agents [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1615.

The challenges and molecular approaches surrounding interleukin-2-based therapeutics in cancer

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IL2-based cancer therapies are limited by their toxicity and pleiotropy.

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Current engineering approaches target IL2 half-life and cell/receptor specificity.

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IL2 may enhance the efficacy of checkpoint inhibitors and CAR-T-based therapies.

Interleukin-2 has had a long history as a promising cancer therapeutic, being capable of eliciting complete and durable remissions in patients with metastatic renal cell carcinoma and metastatic melanoma. Despite high toxicity and efficacy limited to only certain patient subpopulations and cancer types, the prospective use of novel, engineered IL2 formats in combination with the presently expanding repertoire of immuno-oncological targets remains very encouraging. This is possible due to the significant research efforts in the IL2 field that have yielded critical structural and biological insights that have made IL2 more effective and more broadly applicable in the clinic. In this review, we discuss some of the molecular approaches that have been used to further improve IL2 therapy for cancer.

Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study

BACKGROUND

Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery.

METHODS

This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy.

RESULTS

Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51-19.97) than planned admissions (OR: 2.32, 95% CI: 1.43-3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8-51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI.

CONCLUSIONS

After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies.

Abstract 5761: Identification of Fc mutations that optimize agonistic activity of human anti-CD40 monoclonal antibodies by enhancing appropriate Fcg receptor interactions

Several agonistic antibodies against human CD40 are currently being explored as immune therapy for cancer patients. Previously, anti-CD40 antibody therapy showed some clinical efficacy, but significant toxicity at the efficacious dose limited further development. To develop an anti-CD40 agonistic antibody with an improved clinical therapeutic index, we focused on modifications to the heavy chain isotype that would impact interactions with specific Fc receptors.

In mouse models, anti-CD40 murine IgG1 demonstrated stronger immune stimulatory activities than murine IgG2a. The CD40 murine IgG2a antibody induced acute cytokine release within hours of dosing and led to mortality weeks later. To generate human antibodies with an Fc structure that functions similarly to murine IgG1, human IgG1 Fc mutations with reduced binding on human CD16, enhanced binding on CD32A/B, and maintained binding on CD64 were identified through a proprietary mammalian cell surface display technology. A panel of anti-human CD40 antibodies carrying different Fc regions were created. In a CD40 transfected HEK293 NFκB reporter cell assay, where agonistic activity was not related to Fcγ receptor interactions, anti-CD40 human IgG2 demonstrated stronger agonistic activity than human IgG1 antibodies with either wild type or mutated Fc. This result confirmed the reported role of human IgG2 hinge in impacting the agonistic activity of anti-CD40. In assays using primary B cells or monocyte-derived dendritic cells, which constitutively express Fcγ receptors, a subset of anti-CD40 human IgG1 antibodies showed stronger potency than the corresponding human IgG2, due to the better Fcγ receptor crosslinking for IgG1 antibodies. Swapping the human IgG2 hinge into IgG1 Fc did not further enhance the agonistic activity of anti-CD40 antibodies in the primary cell assays, suggesting that the Fc-crosslinking plays a dominant role in mediating the agonistic activity of these anti-CD40 antibodies in biological systems with cells expressing Fcγ receptor. Engineering the proprietary human IgG1 Fc mutations to these anti-CD40 antibodies further enhanced agonistic activity compared to wild type IgG1 in primary cell assays. In addition to the potent agonistic activity, anti-CD40 with the IgG1 Fc mutations demonstrated lower ADCC and reduced cytokine production driven by Fc receptor activation in a co-culture system. Finally, an Fc modified anti-CD40 agonistic antibody demonstrated an acceptable safety profile in cynomolgous monkey toxicity studies. These data suggest anti-CD40 with the proprietary IgG1 Fc mutations represents a newer generation of CD40 agonists for oncology immune therapy.

Citation Format: Shiming Ye, Diane Cohen, Donghee Choi, Siu sze Tan, Joanna Xiong, Yoshiko Akamatsu, Debra Chao, Diane Hollenbaugh, Fiona Harding. Identification of Fc mutations that optimize agonistic activity of human anti-CD40 monoclonal antibodies by enhancing appropriate Fcg receptor interactions [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 5761.

A human dendritic cell-based method to identify CD4+ T-cell epitopes in potential protein allergens

We developed an assay to determine the location of immunodominant CD4(+) T-cell epitopes in any protein. The method uses CD4(+) T cells from community donors in conjunction with dendritic cells derived in vitro. Synthetic peptides constructed to describe the sequence of the protein of interest are cocultured with dendritic cells and CD4(+) T cells, and T-cell proliferation is measured. Data are compiled over a large replicate of human donors to pinpoint immunodominant, usually promiscuous epitope regions. We have applied this technique to a known food allergen, the Brazil nut 2S storage globulin protein, and to two potential food allergens, the Cry1Ab and Cry3Aa proteins. We show epitope data for these three proteins. This assay can be used as a tool to guide the selection and qualification of future potential food transgenes.

Characterization of HLA DR3/DQ2 transgenic mice: a potential humanized animal model for autoimmune disease studies

Linkage studies indicate close associations of certain HLA alleles with autoimmune diseases. To better understand how specific HLA alleles are related to disease pathogenesis, we have generated an HLA DR3/DQ2 transgenic mouse utilizing a 550-kb yeast artificial chromosome (YAC) construct containing the complete DRalpha, DRbeta1, DRbeta3, DQalpha, and DQbeta regions. The transgenic mouse (4D1/C2D) in an I-Abeta(o) background appears healthy with no signs of autoimmune diseases. Lymphoid tissues as well as CD4(+) T cells develop normally. Characterization of the transgene expression demonstrates that approximately 90% of B cells express high levels of DR3 and 50-70% of B cells express DQ2. CD11c(+) dendritic cells express high levels of DR and DQ. Approximately 12-18% of resting T cells are positive for DR expression, and further up-regulation to 40-50% expression is seen upon activation with anti-CD3/anti-CD28 mAb. These results suggest that the transgenic construct confers a high fidelity to the normal human temporal and spatial expression profile. Analysis of T cell receptor repertoire in transgenic mice confirms that DR3/DQ2 are able to mediate thymic selection. Furthermore, transgenic mice respond to a DR3-restricted antigen, demonstrating antigen processing and presentation by antigen-presenting cells (APC). Purified T cells from ovalbumin (OVA)-immunized 4D1 mice respond to human APC co-cultured with OVA, suggesting appropriate antigen/DR3 or DQ2 recognition by murine T cells. Immunoglobulin isotype switching is also observed, indicating functional T-B cognate interactions. Thus, the DR3/DQ2 transgenic mouse has normal lymphoid development and functionality that are mediated by HLA transgenes and can be used to investigate HLA-associated immunological questions.

The role of arginine vasopressin in human labour: functional studies, fetal production and localisation of V1a receptor mRNA

OBJECTIVE

To investigate labour-associated changes in: 1. the myometrial contractile response to arginine vasopressin compared with oxytocin in vitro 2. fetal production of arginine vasopressin and 3. myometrial vasopressin V1a receptor mRNA.

DESIGN

The contractile response to vasopressin (compared with oxytocin) was investigated in paired myometrial strips in vitro. Blood was taken from the umbilical artery and vein at delivery and arginine vasopressin measured by radio-immunoassay. V1a receptor mRNA was determined by in situ hybridisation.

RESULTS

Myometrium was more sensitive to arginine vasopressin than oxytocin (P<0.05 for frequency, amplitude and activity integral in paired strips) after, but not before labour. There was a marked umbilical arteriovenous difference in arginine vasopressin concentration at delivery suggesting fetal production which was not influenced by labour. Myometrial vasopressin V1a receptor mRNA was not increased after the onset of labour.

CONCLUSIONS

The human uterus is extremely sensitive to arginine vasopressin in vitro. Arginine vasopressin is produced by the fetus but fetal formation is not increased during labour.

Peritoneal B-cell development depends on strain, radiation, and time

OBJECTIVE

B-1a, B-1b, and B-2 cells represent the three B-cell subsets in mice. Previous studies have demonstrated that peritoneal B-1a cell development is absent, or nearly so, from adult bone marrow transfers into irradiated adult hosts. The majority of these studies have been performed under a limited set of conditions with irradiated host mice. Here we examined that under a variety of conditions, peritoneal B-1a cells can develop in significant numbers from adult bone marrow transfers into severe combined immunodeficient (SCID) and recombination activation gene 2(-) (RAG-2(-)) mice.

MATERIALS AND METHODS

Adult bone marrow was transferred into various strains of irradiated and nonirradiated adult immunodeficient RAG-2(-) and SCID mice. Peritoneal B-cell engraftment was examined by fluorescein-activated cell sorting analysis and unpaired t-tests were used to determine significant differences of B-cell engraftment among the various conditions of cell transfer.

RESULTS

The level of B-1a cell engraftment was variously affected by the type of host immunodeficiency, the combination of donor and host strains, and the time allowed for engraftment. Irradiation of SCID, but not RAG-2(-), host mice inhibited B-1a-cell engraftment. Additionally, decreasing the number of bone marrow progenitor cells transferred was not found to preferentially affect B-1a cell development in irradiated RAG-2(-) hosts.

CONCLUSION

In the context of these strains, we conclude that adult murine bone marrow contains progenitors that have the capacity to reconstitute peritoneal B-1a cell populations to donor levels.

High-avidity human IgG kappa monoclonal antibodies from a novel strain of minilocus transgenic mice

Human immunoglobulin transgenic mice provide a method of obtaining human monoclonal antibodies (Mabs) using conventional hybridoma technology. We describe a novel strain of human immunoglobulin transgenic mice and the use of this strain to generate multiple high-avidity human sequence IgG kappa Mabs directed against a human antigen. The light chain transgene is derived in part from a yeast artificial chromosome clone that includes nearly half of the germline human V kappa region. In addition, the heavy-chain transgene encodes both human mu and human gamma 1 constant regions, the latter of which is expressed via intratransgene class switching. We have used these animals to isolate human IgG kappa Mabs that are specific for the human T-cell marker CD4, have high binding avidities, and are immunosuppressive in vitro. The human Mab-secreting hybridomas display properties similar to those of wild-type mice including stability, growth, and secretion levels. Mabs with four distinct specificities were derived from a single transgenic mouse, consistent with an extensive diversity in the primary repertoire encoded by the transgenes.

Testing for antibiotic residues in milk

Milk from dairy farms in England and Wales has been tested regularly for antibiotic residues since 1965. The sensitivity of the test organism was 0.02 iu/ml penicillin or equivalent until the change to 0.01 iu/ml in January 1986. In 1984-85, 99.6 per cent of the 2,000,000 milk samples tested passed the test and there was an average of 695 failures per month. From 7500 on-farm investigations over the two years 1983-85 the most frequent reasons suggested by farmers for their test failures were not withholding milk for the full withdrawal period (19.3 to 16.5 per cent) and accidental transfer of milk (16.3 to 16.7 per cent). Lactating and dry cow intramammary antibiotic preparations were held responsible for rather over 50 per cent and 25 per cent respectively of the failures in both years.