Hansen, Michael J.

Abstract Description Therapeutic in situ chimeric antigen receptor (isCAR) T cells can be generated by targeting activated T cells within a lymph node (LN) with retroviruses encoding CARs. While isCAR T cells are successfully generated by intradermal LN priming using adenovirus encoding allogeneic MHC in all mouse lines tested, differences in emerging therapeutic peripheral isCAR T cells are found in a strain dependent manner. Potentially harmful off target retroviral transduction of B cells with CARs is observed within the targeted LN. Here we report the blockade of B cell transduction using anti-CD20 antibody B cell depletion with the introduction of anti-CD19 chimeric antigen receptors into the activated CD8+ T cells. Lymphocytes were analyzed in blood and LN following isCAR T cell generation. When B cells were depleted by systemic administration of anti-CD20 antibodies during isCAR T cell induction, >97.5% systemic depletion of B cells was achieved. Whereas very small numbers of CAR transduced B cells were found in the blood of mice not treated with anti-CD20, none were observed in animals systemically depleted of B cells. In contrast, CAR B cells persisted in the LN of local anti-CD20 treated animals. However, animals expressing dominant CD8+ isCAR T cell populations eliminated LN B cells expressing CARs by week two. Furthermore, systemic treatment of lymphoma in animals with anti-CD20 antibody complemented anti-CD19 isCAR T therapy while blocking off target B cell transduction. Funding Sources Mayo Clinic Ventures Mayo Clinic Graduate School of Biomedical Sciences Mayo Clinic Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)

Abstract Description Blood-brain barrier (BBB) disruption is a putative mechanism of neurodegeneration, neuropsychiatric disorders, and long covid. Our laboratory was the first to demonstrate antigen-specific CD8 T cells induce BBB disruption. We now introduce a novel neurologic disease model in which CD8 T resident memory (TRM) cells induce BBB disruption via administration of cognate antigen, long after neurotropic virus is cleared. C57BL/6 mice intracranially infected with Theiler’s murine encephalomyelitis virus (TMEV) clear virus within 21 days. At 2 months post infection, mice received intravenous injection of viral peptide VP2(121-130) for which the largest population of CD8 TRM have T cell receptor specificity for, resulting in BBB permeability detectable by gadolinium enhanced T1 weighted MRI. A second round of BBB disruption was then initiated with VP2 peptide at 4 months post infection. One month after this second induction of BBB disruption, mice underwent behavioral assessments and whole brain flow cytometric analysis. In these mice, we found a significant inverse correlation of BBB breakdown with a shift from active to passive anxiety-like behavior to contextual fear memory compared to mock peptide controls. This shift in anxiety correlated with virus antigen specific CD8 TRM, myeloid, and NK cells. These results demonstrate memory antiviral CD8 T cells can induce BBB disruption, long after virus is cleared, a process that contributes to a shift in anxiety-like behaviors Funding Sources RO1 NS103212, R01 NS122174 Topic Categories Neuroimmunology (NEUR)

Abstract A variety of genetic diseases of the kidney tubule are amenable to correction via gene therapy. However, gene delivery to renal tubule epithelial cells mediated by viral vectors via the blood is inefficient due to the permselectivity of the glomerular barrier. We hypothesized that effacement of podocyte foot processes would disrupt typical glomerular limitations on filtration and make renal tubule epithelial cells susceptible to transduction from viral vectors delivered intravenously. We determined that adeno-associated virus serotype 8 (AAV8) transduced significantly more epithelial cells in the kidney under the conditions of LPS-induced proteinuria. Use of AAV1 in tandem with LPS-induced proteinuria yielded an ideal two-pronged effect of both partially detargeting the liver and transducing the kidney with a higher bioluminescent signal than AAV8 did, and at half of the dose. Using adenovirus serotype 5 (Ad5) in conjunction with LPS-induced proteinuria showed that kidney transduction was enhanced, but only in glomerular cells. These studies mechanistically test the efficacy of different viral vectors and demonstrate their capacity to transduce kidney epithelial cells. This is a fundamental step in designing future treatments for kidney gene therapy. Significance Statement The slit diaphragms in the glomerulus of the kidney are too narrow to allow most solute from the blood to enter the nephron. As a result, large particles such as viral vectors generally cannot access tubule epithelial cells necessary to correct genetic disorders. In this study, mice are induced into a state of proteinuria and subsequently administered viral vectors intravenously. This group of mice had higher levels of transduced kidney epithelial cells than the control (non-proteinuria) group. The induction of transient proteinuria before intravenous viral vector administration is a novel approach that could make tubulopathies treatable via gene therapy in both animal models and humans.

Background Cancers persist despite expression of immunogenic neoantigens and ongoing antitumor immune responses. While some occult tumors likely are cleared by effective antitumor immune responses, the targeted antigens are not easily identifiable as those tumors spontaneously disappear. Methods We used mouse models with a defined antigenic protein mimicking tumor-specific neoantigens to address the nature of these spontaneous anti-tumor immune responses. Results BALB/c (H-2d ) mice challenged with BALB/c breast tumors expressing the rat-erbB2 oncoprotein succumb to their tumors despite ongoing immune responses targeting tumor-specific model antigens. Meanwhile, congenic BALB.B (H-2b ) and H-2d/H-2b F1 hybrid mice spontaneously eliminate genetically matched tumors in a major histocompatibility complex (MHC)-II dependent manner. Adoptive transfer and immune cell depletion strategies revealed CD4+ T cells and CD20+ B cells are crucial mediators of the protective response in H-2b mice. Furthermore, passive transfer of immune serum from mice rejecting their tumors confers resistance in tumor antigen-tolerant animals with an inversely proportional relationship between tumor outgrowth and the amount of rat-erbB2 specific antibody present in tumor-bearing mice. Introduction of the rat-erb2 ectodomain into other H-2b tumor models also promotes their spontaneous tumor rejection. Notably, the tumor microenvironments differ in rat-erbB2+ tumor-bearing BALB.B and BALB/c mice at the time of fate decision in the models reflecting the differences between effective and ineffective tumor immune responses. Conclusions We find that the effective antitumor immunity targeting neoantigens in these breast cancer models is determined by MHC-II-restricted presentation of optimal cancer-associated antigens. These responses are dependent on CD4+ T cells, B cells, and antigen-specific antibodies.

Abstract Although the functions of tyrosine phosphatases in T‐cell biology have been extensively studied, our knowledge on the contribution of serine/threonine phosphatases in T cells remains poor. Protein phosphatase 2A (PP2A) is one of the most abundantly expressed serine/threonine phosphatases. It is important in thymocyte development and CD4 + T‐cell differentiation. Utilizing a genetic model in which its catalytic subunit alpha isoform (PP2A Cα) is deleted in T cells, we investigated its contribution to CD8 + T‐cell homeostasis and effector functions. Our results demonstrate that T‐cell intrinsic PP2A Cα is critically required for CD8 + T‐cell homeostasis in secondary lymphoid organs and intestinal mucosal site. Importantly, PP2A Cα–deficient CD8 + T cells exhibit reduced proliferation and survival. CD8 + T‐cell antibacterial response is strictly dependent on PP2A Cα. Expression of Bcl2 transgene rescues CD8 + T‐cell homeostasis in spleens, but not in intestinal mucosal site, nor does it restore defective antibacterial responses. Finally, proteomics and phosphoproteomics analyses reveal potential targets dependent on PP2A Cα, including mTORC1 and AKT. Thus, PP2A Cα is a key modulator of CD8 + T‐cell homeostasis and effector functions.

Abstract Cerebral malaria is the deadliest complication that can arise from Plasmodium infection. CD8 T-cell engagement of brain vasculature is a putative mechanism of neuropathology in cerebral malaria. To define contributions of brain endothelial cell major histocompatibility complex (MHC) class I antigen-presentation to CD8 T cells in establishing cerebral malaria pathology, we developed novel H-2Kb LoxP and H-2Db LoxP mice crossed with Cdh5-Cre mice to achieve targeted deletion of discrete class I molecules, specifically from brain endothelium. This strategy allowed us to avoid off-target effects on iron homeostasis and class I-like molecules, which are known to perturb Plasmodium infection. This is the first endothelial-specific ablation of individual class-I molecules enabling us to interrogate these molecular interactions. In these studies, we interrogated human and mouse transcriptomics data to compare antigen presentation capacity during cerebral malaria. Using the Plasmodium berghei ANKA model of experimental cerebral malaria (ECM), we observed that H-2Kb and H-2Db class I molecules regulate distinct patterns of disease onset, CD8 T-cell infiltration, targeted cell death and regional blood–brain barrier disruption. Strikingly, ablation of either molecule from brain endothelial cells resulted in reduced CD8 T-cell activation, attenuated T-cell interaction with brain vasculature, lessened targeted cell death, preserved blood–brain barrier integrity and prevention of ECM and the death of the animal. We were able to show that these events were brain-specific through the use of parabiosis and created the novel technique of dual small animal MRI to simultaneously scan conjoined parabionts during infection. These data demonstrate that interactions of CD8 T cells with discrete MHC class I molecules on brain endothelium differentially regulate development of ECM neuropathology. Therefore, targeting MHC class I interactions therapeutically may hold potential for treatment of cases of severe malaria.

Abstract Bone marrow is a primary immune organ responsible for stem cell maintenance and hematopoiesis. While the bone marrow niche is mainly studied in the context of hematopoiesis, aging, and mechanisms underlying stem cell and plasma cell survival, changes of the niche during brain viral infections and primary T cell responses is unknown. Intracranial infection with the neurotropic Theiler’s Murine Encephalomyelitis Virus (TMEV) results in an acute infection in the C57BL/6 mouse which is cleared 30 days post infection due to generation of an antigen specific CD8 T cell response raised against the immunodominant epitope VP2121–130. We determined that 7–10% of CD8 T cells present in the sternal and femoral bone marrows and 15–20% in the cranial bone marrow were antigen specific 7 days post intracranial TMEV infection. Over 70% of these CD8 T cells were located outside of the vasculature as determined by IV labeling. Importantly, continuous treatment with FTY720, which sequesters T cells outside of the blood, did not eliminate antigen specific CD8 T cells in any bone marrow compartment. CD8 T cells in the bone marrow established durable memory following viral clearance and were reactivated upon cognate antigen reencounter. Both acute TMEV infection and antigen specific reactivation caused an increase in lineage−, Sca-1+, ckit+ (LSK) cells in the bone marrow. This LSK dysregulation was abrogated upon CD8 T cell depletion. We conclude that brain viral infections induce in situ effector and memory T cell responses within the bone marrow compartment. Both acute and memory recall CD8 T cell responses cause stem cell dysregulation. Our data hence paves the way for crucial studies of bone marrow resident antigen specific CD8 T cells in health and disease. Supported by grants from NIH (K99NS117799-01A1 (KA), R01NS103212 (AJJ), and RF1NS122174(AJJ)

Abstract Cerebral malaria (CM) is a severe complication of P. falciparum infection and a leading cause of death, globally. Plasmodium berghei ANKA (PbA) infection of C57BL/6 mice serves as a murine model of CM called experimental cerebral malaria (ECM) due to the neurological and neuropathological features that simulate the infection of human CM. A putative mechanism of disease in human CM requires CD8 T cell to infiltration into the brain and blood-brain barrier disruption. The specific antigen-presenting cell type(s) that prime this CNS infiltrating CD8 T cell response capable of inducing lethal blood-brain barrier disruption has not been defined. To answer this, single class I expressing Kb loxP transgenic mice were generated. Crossing these mice to class I deficient CD11c-cre or LysM-cre mice created the LysM-cre Kb cKO and CD11c-cre Kb cKO mice, respectively. PbA infected Kb loxP and LysM-cre Kb cKO were susceptible to ECM. In contrast, CD11c-cre Kb cKO mice survived acute PbA infection and avoided neurological manifestations. We therefore employed spectral flow cytometry to analyze splenocytes and brain infiltrating immune cells during acute PbA infection in these genotypes. We observed a reduction in activated CD8 T cells in the spleens of PbA infected CD11c-cre Kb cKO mice versus the Kb loxP mice and the LysM-cre Kb cKO. This reduced peripheral CD8 T cell activation in PbA infected CD11c-cre Kb cKO mice also corresponded with reduced brain infiltration of CD8 T cells. We conclude a CD11c+ APC is therefore required for priming and potentially recruitment of CD8 T cells to the brain during lethal ECM pathology. 5R01NS103212-06

Abstract Brain atrophy is a common feature of many neurological diseases as diverse as Alzheimer’s disease, cerebral palsy, Huntington’s disease, multiple sclerosis, epilepsy, encephalitis, neurosyphilis, neuroAIDS, and Covid-19 infection. We have developed a murine model of brain atrophy using the Theiler’s murine encephalomyelitis virus (TMEV) infection mouse model of multiple sclerosis. In this study, we investigated the contribution of the MHC class I molecule, H-2Db, in generating an immune response associated with the onset of brain atrophy using mice with a C57BL/6 background. The H-2DbClass I molecule not only contributed to significantly more ventricular enlargement in a T2-weighted MRI at 45 d.p.i., but this ventricular enlargement correlated to CD8 T cell infiltration. To further define the cellular and molecular mechanisms of MHC class I molecules in TMEV induced brain atrophy we investigated the cell specific contribution of brain resident antigen presenting cells (APCs) in ventricular atrophy. We developed novel bi-transgenic mouse lines with tamoxifen induced conditional ablation of the H-2Db class I molecule in Cx3CR1+ brain resident myeloid cells. Cx3CR1cre+/Db Lox P mice presented with significantly less ventricular atrophy at 45 d.p.i., compared to cre- littermates along with a decrease in CD8 T cell infiltration. These results strongly imply that antigen presentation by H-2Db on myeloid cells, at least in part is responsible for the development of brain atrophy and provided insight into the molecular mechanism of this poorly understood neuropathology. NS103212, NS122174

Abstract The receptor tyrosine kinase AXL is a member of the TYRO3, AXL, and proto-oncogene tyrosine-protein kinase MER family and plays pleiotropic roles in cancer progression. AXL is expressed in immunosuppressive cells, which contributes to decreased efficacy of immunotherapy. Therefore, we hypothesized that AXL inhibition could serve as a strategy to overcome resistance to chimeric antigen receptor T (CAR T)–cell therapy. To test this, we determined the impact of AXL inhibition on CD19-targeted CAR T (CART19)–cell functions. Our results demonstrate that T cells and CAR T cells express high levels of AXL. Specifically, higher levels of AXL on activated Th2 CAR T cells and M2-polarized macrophages were observed. AXL inhibition with small molecules or via genetic disruption in T cells demonstrated selective inhibition of Th2 CAR T cells, reduction of Th2 cytokines, reversal of CAR T-cell inhibition, and promotion of CAR T-cell effector functions. AXL inhibition is a novel strategy to enhance CAR T-cell functions through two independent, but complementary, mechanisms: targeting Th2 cells and reversing myeloid-induced CAR T-cell inhibition through selective targeting of M2-polarized macrophages.