Cerebrovascular Complications Associated With Iatrogenic Fungal Meningitis Following Surgical Procedures in Mexico

BACKGROUND

The current fungal meningitis outbreak caused by contaminated epidural anesthesia with Fusarium solani among patients who underwent surgical procedures in Matamoros, Mexico remains a cause of concern. Its association with an increased susceptibility for cerebrovascular complications (CVC) has not been reported. This single-center study describes 3 patients with a unique pattern of CVC attributed to fungal meningitis.

METHODS

A retrospective case series of patients diagnosed with fungal meningitis following surgical procedures under contaminated epidural anesthesia who developed a unique pattern of CVC during their hospitalization.

RESULTS

Three female patients (mean age, 35 years) with CVC due to iatrogenic fungal meningitis were included. Positive Fungitell β-D-glucan assay in cerebrospinal fluid was documented in all cases, and F. solani was confirmed by polymerase chain reaction in case 3. All cases were complicated by severe vertebrobasilar circulation vasculopathy and arterial dissections with resultant subarachnoid hemorrhage and intraventricular hemorrhage, ultimately leading to patients' death.

CONCLUSIONS

The death toll from the ongoing fungal meningitis outbreak keeps rising, underscoring the need for early recognition and aggressive treatment. We highlight the risk for vertebrobasilar circulation CVC among these patients. The angioinvasive nature of F. solani is yet to be clarified; however, a clear pattern has been observed. Public health awareness should be raised and a strong response should be pursued.

oHSV-P10 reduces glioma stem cell enrichment after oncolytic HSV therapy

Longstanding evidence implicate glioma stem-like cells as the main drivers contributing toward glioblastoma (GBM) therapy resistance and tumor recurrence. Although oncolytic herpes simplex virus (oHSV) viral therapy is a promising biological therapy recently approved for melanoma (in the United States and Europe) and GBM (in Japan); however, the impact of this therapy on GBM stem-like cells (GSCs) is understudied. Here we show that post-oHSV virotherapy activated AKT signaling results in an enrichment of GSC signatures in glioma, which mimics the enrichment in GSC observed after radiation treatment. We also uncovered that a second-generation oncolytic virus armed with PTEN-L (oHSV-P10) decreases this by moderating IL6/JAK/STAT3 signaling. This ability was retained in the presence of radiation treatment and oHSV-P10-sensitized intracranial GBM to radiotherapy. Collectively, our findings uncover potential mechanisms to overcome GSC-mediated radiation resistance via oHSV-P10.

PKR induces TGF-β and limits oncolytic immune therapy

BACKGROUND

Mammalian cells have developed multiple intracellular mechanisms to defend against viral infections. These include RNA-activated protein kinase (PKR), cyclic GMP-AMP synthase and stimulation of interferon genes (cGAS-STING) and toll-like receptor-myeloid differentiation primary response 88 (TLR-MyD88). Among these, we identified that PKR presents the most formidable barrier to oncolytic herpes simplex virus (oHSV) replication in vitro.

METHODS

To elucidate the impact of PKR on host responses to oncolytic therapy, we generated a novel oncolytic virus (oHSV-shPKR) which disables tumor intrinsic PKR signaling in infected tumor cells.

RESULTS

As anticipated, oHSV-shPKR resulted in suppression of innate antiviral immunity and improves virus spread and tumor cell lysis both in vitro and in vivo. Single cell RNA sequencing combined with cell-cell communication analysis uncovered a strong correlation between PKR activation and transforming growth factor beta (TGF-ß) immune suppressive signaling in both human and preclinical models. Using a murine PKR targeting oHSV, we found that in immune-competent mice this virus could rewire the tumor immune microenvironment to increase the activation of antigen presentation and enhance tumor antigen-specific CD8 T cell expansion and activity. Further, a single intratumoral injection of oHSV-shPKR significantly improved the survival of mice bearing orthotopic glioblastoma. To our knowledge, this is the first report to identify dual and opposing roles of PKR wherein PKR activates antivirus innate immunity and induces TGF-ß signaling to inhibit antitumor adaptive immune responses.

CONCLUSIONS

Thus, PKR represents the Achilles heel of oHSV therapy, restricting both viral replication and antitumor immunity, and an oncolytic virus that can target this pathway significantly improves response to virotherapy.

EXTH-42. DUAL ROLES OF PKR ORCHESTRATE ONCOLYTIC HSV SENSITIVITY AND ANTIGEN-SPECIFIC T CELL EXPANSION

The host immune system has developed many mechanisms to defend against and clear virus infections, including PKR, cGAS-STING and TLR-MyD88 signaling pathways. Compromised anti-viral mechanisms in tumor cells allows for infection, replication and lysis by oncolytic viruses. However, compromised antiviral mechanisms, together with immune cells and the tumor microenvironment (TME), limit the sensitivity of oncolytic virus in tumor cells. We generated a novel oncolytic Herpes simplex virus, oHSV-shPKR which disables tumor-intrinsic PKR signaling. oHSV-shPKR significantly increases oHSV infection and lysis in both oncolytic virus-resistant and sensitive glioblastomas (GBMs). Infection of oHSV-shPKR in GBMs induces G2/M cell cycle arrest and inhibits tumor cell growth. oHSV-shPKR increases activation of antigen presentation cells through type I interferon signaling activation and its immune-stimulatory function to increase tumor-antigen specific CD8 T-cell expansion, including cytotoxic T lymphocytes. Preclinical studies showed that oHSV-shPKR intra-tumoral injection significantly inhibits human GBM patient derived xenograft (PDX) tumor growth in immune-deficient NSG mice and murine orthotopic GBM tumor growth in immunocompetent mice. The results demonstrate that the novel oHSV-shPKR has the potential to be used in clinical applications for both oHSV-resistant and sensitive GBM treatment.

EXTH-77. TARGETING CD73 IN GBM SENSITIZES TUMORS TO ONCOLYTIC VIRUS THERAPY

Glioblastoma Multiforme (GBM) is the most aggressive malignant primary brain tumor and has abysmal 5-year overall survival. With the approval of oHSV Imlygic by FDA for metastatic melanoma and more recently, conditional approval of G47Δ, marketed by Daiichi Sankyo for GBM treatment in Japan, oncolytic viral therapy has emerged as a promising biological approach to treat solid tumors. Our laboratory has previously shown that oHSV expressing long isoform of PTEN (PTENα), HSV-P10, has faster kinetics of virus replication associated with enhanced killing of the glioma cells compared to control HSV. Additionally, HSVP-10 is known to increase mitochondrial membrane potential and cellular ATP production while stimulating anti-tumor immune responses in vivo. RNA sequencing of primary GBM cells infected with HSV-P10 shows altered metabolic pathways relative to control HSV infected cells. 13C metabolic flux analysis in uninfected and control or HSV-P10 infected primary GBM cells reveals that while HSV-P10 infection shuttles most of the glutamine towards citrate by reductive carboxylation of α-ketoglutarate resulting in faster replication of HSV-P10, simultaneously it increased glucose utilization and shuttling towards TCA cycle. This corroborates with enhanced mitochondrial activity leading to increased oxidative phosphorylation and increased cellular and extracellular ATP (eATP). eATP binds to purinergic receptors on tumor and immune cells and boosts anti-tumor immunity. However, the use of extracellular ATP in cancer therapy is limited owing to its short half-life and rapid hydrolysis by ectoenzymes CD39 and CD73 into immune-suppressing adenosine. CD73 carries out the conversion of AMP to adenosine, making it a key regulator of this pathway. Using mice with CD73 knocked out globally (CD73KO), we show that combination of CD73 inhibition with HSV-P10 imparts significant survival benefit compared to WT mice treated with HSV-P10. Our findings will further the understanding of oHSV therapy and the role of the ATP/adenosine in the tumor microenvironment.

TMIC-39. TARGETING EXTRACELLULAR MATRIX HYALURONIC ACID-CD44 SIGNALING REDUCES TUMOR STEMNESS AND SENSITIZES TUMOR TO VIROTHERAPY AND ENHANCES THERAPEUTIC POTENTIAL FOR CANCER TREATMENT

The tumor microenvironment (TME), including the non-tumor cells and the extracellular matrix (ECM) plays a crucial role in tumor progression and metastasis. Hyaluronic acid (HA), the major glycosaminoglycan present in brain ECM, has long been associated with the progression and invasiveness of brain tumors. HA signals primarily thorough CD44, an adhesion/homing receptor leading to the induction of cellular AKT, MEK and HIF signaling, thereby promoting tumor cell proliferation, aggressiveness and therapy resistance. While HA in the ECM has been shown to interfere with infection and spread of oncolytic viruses, the impact of tumor-ECM interaction induced signaling on oncolytic virotherapy is heavily understudied. RNA sequencing and gene set enrichment analysis of glioma cells infected with an oncolytic Herpes Simplex Virus-1 (oHSV) demonstrate an enrichment of pathways related to tumor-ECM interaction. Immunostaining of brain sections from intracranial tumor bearing mice also reveals increased HA after oHSV treatment. Our results further demonstrate that HA/CD44-mediated signaling inhibits virus replication in vitro. Herein, to evaluate the impact of blocking tumor-ECM interactions without altering the secreted ECM, we created oHSV-sCD44, an oHSV that encodes for extracellular soluble CD44 (sCD44) that can function as a dominant negative receptor for membrane bound CD44. oHSV-sCD44 significantly reduces the stemness of glioblastoma stem cells (GSCs), induces DNA damage and sensitizes the GSCs to radiation therapy. Intra-tumoral injection of oHSV-sCD44 into patient-derived primary GBM xenograft model significantly inhibits tumor growth accompanied by reduced stemness and decreased HA expression, and increased oHSV replication and tumor cell lysis in TME. Moreover, blocking HA-CD44 signaling with a single dose of oHSV-sCD44 in murine glioma syngeneic model induces the development of a significant anti-tumor immune response with enhanced T cell infiltration. Collectively, our findings implicate oHSV-sCD44 as a potential oncolytic and immune-stimulating anticancer therapeutic.

EXTH-51. HSV-PTENΑ TREATMENT TARGETS GLIOMA STEM CELLS TO REDUCE STEMNESS AND SENSITIZES GLIOBLASTOMA TO IRRADIATION

Glioblastoma is one of the most lethal and treatment-resistant tumors of the central nervous system. Despite maximal surgical and medical therapy, survival remains dismal with a median of 21 months. Despite advances in treatment, this has only led to modest survival benefit. A significant challenge in treatment of glioblastoma is targeting glioma stem cells (GSCs) which are a source of therapy resistance. Oncolytic viral (OV) therapy is a promising therapy for solid tumors that preferentially targets tumor cells for lysis and an anti-tumor immune response while sparing normal cells. Among all OVs, oncolytic Herpes Simplex Virus (oHSV) is substantially ahead in the clinic, with an oHSV T-VEC approved by the FDA for metastatic melanoma treatment and G47∆ which received conditional approval for the treatment of GBM in Japan. In prior work, our group has demonstrated that PTENα expression by an oHSV (HSV-P10) results in improved long-term survivors in intracranial tumor-bearing mice compared to HSVQ treatment. We aim to elucidate the mechanism of improved therapeutic efficacy of HSV-P10 against GBM and evaluate if HSV-P10 may overcome radio-resistance. RNA sequencing and GSEA analysis of primary human GBM cells infected with control HSVQ or HSV-P10 reveals that while HSVQ virus infection leads to an increase in genes regulating IL6-STAT3 pathway, pivotal in maintaining stemness properties, HSV-P10 infection leads to a reduction. HSV-P10 reduces CD133+/CD44+ stem cells, induces DNA damage and sensitizes the GBM cells to irradiation. Our findings reveal a novel mechanism induced by HSV-P10 in combination with irradiation where HSV-P10 modulates IL6-STAT3 signaling downregulating genes associated with stemness (Nestin, Sox2). HSV-P10 infection in combination with irradiation reduces GSC tumor sphere formation in vitro and sensitizes GBMs to radiotherapy in an intracranial mouse xenograft model. Our findings uncover a possible mechanism to overcome GSC-mediated therapy resistance to improve the therapeutic efficacy for GBM.

Abstract LB128: Oncolytic HSV-P10 and effects on metabolism as potential therapy for treatment of glioblastoma

Glioblastoma is an aggressive tumor of the central nervous system associated with a very poor prognosis even with surgery and chemoradiation. We have previously developed an oHSV that encodes for PTENα (HSV-P10) and stimulates anti-tumor immunity. This virus is currently licensed by and is being developed by Mesoblast to evaluate safety and efficacy in patients. To understand the effect of PTENα on tumor cell responses to oHSV therapy we performed RNA sequencing of primary GBM cells infected with control or oHSV-P10. We identified a dysregulation of glycolysis in cells infected with oHSV-P10 relative to control oHSV. Since cancer cells rely heavily on glycolysis for energy production (Warburg effect) the impact of PTENα on metabolic switch was significant. RNA sequencing PCR and western blot analysis showed a significant reduction in cellular Hexokinase II expression and downregulation of HIF-1α in HSV-P10 infected cells. Consistent with the function of HIF1 and hexokinase in driving glycolysis we also observed a significant reduction in glucose uptake and lactate release: implying a reduction in glycolysis in cells after being treated with oHSV-P10. Thus, cellular energetics of HSV-P10 infected cells was directed away from glycolysis relative to HSVQ infected cells. Consistent with this we observed increased, oxidative phosphorylation, production of reactive oxidative species and ATP production. Many cancers, including Glioblastoma are known to utilize the glutamine as a substrate for energy production through its entry into the TCA cycle. Blocking this shows a significant decrease in cell viability and ATP production when combined with HSV-P10. These results indicate that combination of HSV-P10 with radiation has a significant therapeutic potential and should be tested in patients for safety and efficacy.

Citation Format: Matthew P. Mullarkey, Upasana Sahu, Bangxing Hong, Balveen Kaur. Oncolytic HSV-P10 and effects on metabolism as potential therapy for treatment of glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB128.

Abstract LB020: PTEN-L expressing HSV induces glioma stem cell differentiation and sensitizes glioblastoma to radiation in mice

GBM, a WHO classified Grade IV glioma, is one of the most lethal and heterogeous primary brain tumors with inevitable recurrence, limiting the median survival time less than 21 months. Current standard-of-care treatment including surgical resection followed by chemo- and radio-therapy remains palliative because of therapy resistance, majorly conferred by GBM stem cells (GSCs), leading to tumor recurrence. With no current effective treatments, novel approaches to overcome GSCs-mediated resistance to chemotherapy and irradiation are urgently required in order to achieve long-term success in GBM therapy. Oncolytic viral (OV) therapy represents a novel and promising biological therapy for solid tumor that preferentially targets tumor cells for lytic destruction, sparing the healthy cells and in the process activating host anti-tumor immune response. Among all OVs, oncolytic Herpes Simplex Virus (oHSV) is substantially ahead in the clinic, with an oHSV T-VEC approved by the FDA for metastatic melanoma treatment. Recently, G47∆, another HSV1 virus, has been granted conditional approval for the treatment of GBM in Japan. Further, several other oHSVs including G207 and HSV1716 are currently being tested for safety and efficacy against GBM. This has fueled great expectations towards OVs as a promising alternative to conventional therapies. Our group has previously shown that PTENα expression by an oHSV (HSV-P10) resulted in further improved long-term survivors in intracranial tumor-bearing mice compared to HSVQ treatment. Here we aim to dissect the molecular mechanisms associated with improved therapeutic efficacy of HSV-P10 against GBM, and if HSV-P10 can overcome GBM cell radioresistance. The RNA sequencing and GSEA analyses of primary human GBM cells infected with control HSVQ or HSV-P10 reveals that while HSVQ virus infection leads to an increase in genes regulating IL6-STAT3 pathway, pivotal in maintaining stemness properties, HSV-P10 infection causes a reduction in the genes regulating this pathway. As a consequence, HSV-P10 reduces CD133+/CD44+ stem cell fraction, induces DNA damage and sensitizes the GBM cells to irradiation. Our findings reveal a novel mechanism induced by HSV-P10 in combination with irradiation whereby HSV-P10 modulates IL6-STAT3 signaling downregulating Sox2, a core transcription factor in the maintenance of GSCs, with a simultaneous decrease in Nestin expression and enhanced GFAP expression promoting GSC differentiation. HSV-P10 infection in combination with irradiation reduces GSC tumor sphere formation in vitro and sensitizes GBMs to radiotherapy in an intracranial mouse xenograft model. Collectively, our findings provide a potential avenue to overcome GSC-mediated therapy resistance to improve the therapeutic efficacy for GBM patients.

Citation Format: Upasana Sahu, Matthew P. Mullarkey, Bangxing Hong, Balveen Kaur. PTEN-L expressing HSV induces glioma stem cell differentiation and sensitizes glioblastoma to radiation in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB020.

Replication and Spread of Oncolytic Herpes Simplex Virus in Solid Tumors

Oncolytic herpes simplex virus (oHSV) is a highly promising treatment for solid tumors. Intense research and development efforts have led to first-in-class approval for an oHSV for melanoma, but barriers to this promising therapy still exist that limit efficacy. The process of infection, replication and transmission of oHSV in solid tumors is key to obtaining a good lytic destruction of infected cancer cells to kill tumor cells and release tumor antigens that can prime anti-tumor efficacy. Intracellular tumor cell signaling and tumor stromal cells present multiple barriers that resist oHSV activity. Here, we provide a review focused on oncolytic HSV and the essential viral genes that allow for virus replication and spread in order to gain insight into how manipulation of these pathways can be exploited to potentiate oHSV infection and replication among tumor cells.

Posttreatment Maturation of Medulloblastoma into Gangliocytoma: Report of 2 Cases

INTRODUCTION

We report 2 cases of medulloblastoma maturing into gangliocytoma after receiving multimodal therapy. Here we present 2 cases of diagnosed medulloblastoma which on re-resection were noted to be gangliocytoma without heterogeneity, which is an extremely rare occurrence.

CASE PRESENTATION

The first patient, an 11-year-old boy diagnosed with high-risk (non-WNT, non-SHH) medulloblastoma, was treated with near-total surgical resection followed by craniospinal radiation therapy with weekly vincristine. He then received maintenance chemotherapy with vincristine, cyclophosphamide, and cisplatin. On surveillance MR imaging studies residual tumor in the lateral aspect of the tumor bed was noted to be slowly growing, eliciting gross-total resection of the residual tumor. Histopathology showed benign gangliocytoma without residual medulloblastoma. The second patient, a 3-year-old girl, was diagnosed with medulloblastoma, desmoplastic nodular variant. She was initially treated with gross total resection and chemotherapy with etoposide, carboplatin, and high-dose methotrexate. At 4 months off therapy, she was noted to have local recurrence along the resection cavity. Second-line therapy was started with irinotecan and temozolomide, but MRI assessment during treatment showed further disease progression. She then received craniospinal radiation. Eleven months off therapy, further radiographic progression was noted, and the patient underwent second-look surgery, with pathology showing gangliocytoma and treatment-related gliosis.

DISCUSSION/CONCLUSION

The maturation of medulloblastoma into a ganglion cell-rich lesion is very rare, with few well-characterized previous reports. Given the rare nature of this entity, it would be of great value to understand the process of posttreatment maturation and the genetic and treatment factors which contribute to this phenomenon.

Intrinsic Connections of the Core Auditory Cortical Regions and Rostral Supratemporal Plane in the Macaque Monkey

In the ventral stream of the primate auditory cortex, cortico-cortical projections emanate from the primary auditory cortex (AI) along 2 principal axes: one mediolateral, the other caudorostral. Connections in the mediolateral direction from core, to belt, to parabelt, have been well described, but less is known about the flow of information along the supratemporal plane (STP) in the caudorostral dimension. Neuroanatomical tracers were injected throughout the caudorostral extent of the auditory core and rostral STP by direct visualization of the cortical surface. Auditory cortical areas were distinguished by SMI-32 immunostaining for neurofilament, in addition to established cytoarchitectonic criteria. The results describe a pathway comprising step-wise projections from AI through the rostral and rostrotemporal fields of the core (R and RT), continuing to the recently identified rostrotemporal polar field (RTp) and the dorsal temporal pole. Each area was strongly and reciprocally connected with the areas immediately caudal and rostral to it, though deviations from strictly serial connectivity were observed. In RTp, inputs converged from core, belt, parabelt, and the auditory thalamus, as well as higher order cortical regions. The results support a rostrally directed flow of auditory information with complex and recurrent connections, similar to the ventral stream of macaque visual cortex.

Distributed acoustic cues for caller identity in macaque vocalization

Individual primates can be identified by the sound of their voice. Macaques have demonstrated an ability to discern conspecific identity from a harmonically structured 'coo' call. Voice recognition presumably requires the integrated perception of multiple acoustic features. However, it is unclear how this is achieved, given considerable variability across utterances. Specifically, the extent to which information about caller identity is distributed across multiple features remains elusive. We examined these issues by recording and analysing a large sample of calls from eight macaques. Single acoustic features, including fundamental frequency, duration and Weiner entropy, were informative but unreliable for the statistical classification of caller identity. A combination of multiple features, however, allowed for highly accurate caller identification. A regularized classifier that learned to identify callers from the modulation power spectrum of calls found that specific regions of spectral-temporal modulation were informative for caller identification. These ranges are related to acoustic features such as the call's fundamental frequency and FM sweep direction. We further found that the low-frequency spectrotemporal modulation component contained an indexical cue of the caller body size. Thus, cues for caller identity are distributed across identifiable spectrotemporal components corresponding to laryngeal and supralaryngeal components of vocalizations, and the integration of those cues can enable highly reliable caller identification. Our results demonstrate a clear acoustic basis by which individual macaque vocalizations can be recognized.