One Cell Systems (United States)

Adeno-associated virus (AAV) vectors are promising platforms used in a growing number of approved gene therapy (GT) products across diverse therapeutic areas. Due to the potential safety and efficacy concerns associated with AAV-based immune responses, patients with pre-existing anti-AAV antibodies (Abs) are routinely excluded from GT trials to prevent treatment of patients who are hypothesized to have potentially higher risk and/or little or no benefit. However, the exclusion of seropositive patients without prior GT exposure is not based on data-driven Ab titer cut-offs, and diagnostics to identify levels of pre-existing immunity have not been standardized, precluding data generation that would substantiate or reject this hypothesis. There are also significant gaps in clinical data comparing the impact of pre-existing immunity with treatment-induced immune responses for a variety of disease states. This review aims to address these gaps by examining the impact of pre-existing anti-AAV Abs on the safety and efficacy of approved and failed GT products and ongoing clinical trials. Together, these data suggest that pre-existing immunity may not be the principal determinant of GT success. Therefore, to expand the number of patients eligible for treatment, novel AAV GTs should be optimized to mitigate against the effects of anti-AAV Abs and avoid the need for exclusionary screening; in turn, including both seronegative and seropositive patients in clinical trials will enable characterization of the clinical relevance of anti-AAV Abs. Strategies to prevent an undesirable immune response to GT, including immunosuppressive regimens and modifications to GT manufacturing, design and delivery, are presented for consideration in future GT trials.

Cryptosporidium causes debilitating diarrheal disease in patients with primary and acquired defects in T cell function. However, it has been a challenge to understand how this infection generates T cell responses and how they mediate parasite control. Here, Cryptosporidium was engineered to express a parasite effector protein (MEDLE-2) that contains the MHC-I restricted SIINFEKL epitope which is recognized by TCR transgenic OT-I CD8 + T cells. These modified parasites induced expansion of endogenous SIINFEKL-specific and OT-I CD8 + T cells that were a source of IFN-γ that could restrict growth of Cryptosporidium . This T cell response was dependent on the translocation of the effector and similar results were observed with another secreted parasite effector (ROP1). Although infection and these translocated effector proteins are restricted to intestinal epithelial cells (IEC), type I dendritic cells (cDC1) were required to generate CD8 + T cell responses to these model antigens. These data sets highlight Cryptosporidium effectors as targets of the immune system and suggest that crosstalk between enterocytes and cDC1s is crucial for CD8 + T cell responses to Cryptosporidium .

To evaluate a new US Food and Drug Administration (FDA)-cleared immunohistochemistry (IHC) control (IHControls [Boston Cell Standards]) comprising peptide epitopes for HER2, estrogen receptor (ER), and progesterone receptor (PR) attached to cell-sized microspheres and to compare its performance against conventional tissue controls. IHControls and tissue/cell line controls for HER2, ER, and PR were compared side by side daily at 5 clinical IHC laboratories for 1 to 2 months. Separately, the sensitivity of the 2 types of controls was evaluated in simulated IHC assay failure experiments by diluting the primary antibody. Additional evaluations included lot-to-lot manufacturing reproducibility of 3 independent lots and specificity against 26 antigenically irrelevant IHC stains. Side-by-side testing revealed a 99.6% concordance between IHControls and tissue controls across 5 IHC laboratories and 766 individual evaluations. Three discordant quality control events were the result of operator error. Simulated assay failure data showed that both IHControls and tissue controls are similarly capable of detecting IHC staining errors. Manufacturing reproducibility of IHControls showed less than 10% variability (coefficient of variation). No cross-reactions were detected from 26 antigenically irrelevant IHC stains. IHControls, the first FDA-cleared IHC controls, can sensitively and accurately detect IHC assay problems, similar to tissue controls.