Central Nervous System Spread Research Articles

Screening Cerebrospinal Fluid for Aggressive B-Cell Lymphoma: Significance of Clonal Populations Found with 8-Color Flow Cytometry

Background: Secondary central nervous system (CNS) lymphoma confers a poor prognosis, and prompt identification is critical for guiding management. Over the last decade, we have employed cerebrospinal fluid (CSF) analysis with 8-color flow cytometry (FCM) in screening patients deemed at risk of CNS relapse. However, there is little data to guide interpretation and management of positive results, and concurrent clinical and radiographic features of FCM positive (FCM+) patients, remain areas of uncertainty. Methods: We analyzed newly diagnosed (ND) and relapsed/refractory (R/R) diffuse large B cell lymphoma (DLBCL) and high grade B cell lymphoma (HGBCL) patients who underwent a screening lumbar puncture (LP) from 2011-2020. Clinical, imaging, and CSF findings (differential, cytology, FCM) were collected. Patients with prior CNS involvement or FCM showing CLL/low-grade B-NHL were excluded. “FCM-only” patients were defined as FCM+ but without any other evidence of CNS spread (negative cell count/cytology, MRI, and no symptoms), whereas others were deemed to have overt CNS disease. Results: There were 415 LPs among 361 patients (243 ND, 172 R/R). 21 (5%) patients were FCM+, 10 ND and 11 R/R patients (Table 1). Four had FCM-only involvement (2 ND, 2 R/R). Among these, the clonal population was 1.63% of WBC (range, 0.3-2.7%), and 3 had concurrent bone marrow (BM) or peripheral blood (PB) involvement. All 4 received intrathecal (IT) therapy. At median follow up of 23 months, 3 (75%) have died (2 from CNS disease progression, 1 unknown due to loss in follow up), and 1 remains alive in remission 44 months later following IT methotrexate (MTX) and CAR T-cell therapy. 17 had overt CNS disease (8 ND, 9 R/R). The clonal population was 9% (range, 0.2-98%). Eight (47%) had concurrent BM or PB involvement. Twelve (70%) received IV high dose MTX, and the remainder received only IT therapy. At median follow up of 42 months, 9 (53%) have relapsed (2 CNS only, 1 systemic, 6 both), and 9 have died. Median time to CNS relapse was 5 months. Conclusions: CSF 8 color FCM screening of DLBCL/HGBCL patients yields a low proportion of positive results, mostly in the setting of overt CNS disease. However, even FCM-only patients had poor outcomes (2/4 with CNS progression), suggesting that blood contamination does not explain CSF findings, and that these patients should be approached as secondary CNS involvement. Better pt selection for CSF screening is needed to reduce unnecessary LPs. Intensified or novel approaches for all FCM+ patients are needed.

Predictors of disease severity in COVID-19 associated mucormycosis: impact of HbA1C levels, time lag to mucormycosis onset, and radiologic patterns of paranasal sinuses and spaces involvement

Background Identifying early predictors of severe Covid-19 associated mucormycosis (CAM) can help improve management and treatment outcomes. Objectives Primary: To identify clinical and radiological predictors of disease severity in CAM. Secondary: To describe patterns of central nervous system (CNS) involvement in CAM. Methods A total of 71 patients with CAM were included in the study. Based on the anatomical extent of involvement on MRI, patients were divided into three groups: Sinus (paranasal sinuses), Orbit (orbital spread), and CNS (CNS spread). Clinical parameters and radiological patterns of involvement of sinuses and extra sinus spaces were studied between the three groups. Patterns of CNS involvement were also described. Results A shorter time lag between COVID-19 infection and CAM, as well as high HbA1C levels, were found to be associated with severe disease. Involvement of the sphenoid, ethmoid and frontal sinuses, T1 hyperintense signal in the sphenoid, as well as bony involvement of the sphenoid sinus, were significantly associated with severe disease. Extra-sinus spread into pre/retroantral space, pterygopalatine fossa, and masticator spaces were also significantly associated with a severe disease course. The most common pattern of CNS spread was cavernous sinus involvement, followed by pachymeningeal spread and cranial nerve involvement. Conclusion Early identification of the above-described predictors in patients presenting with CAM can help detect those at risk for developing severe disease. A longer duration of amphotericin, combined with a more aggressive surgical approach in selected cases, may lead to better long-term outcomes.

Central Nervous System Metastasis in Neuroblastoma: From Three Decades Clinical Experience to New Considerations in the Immunotherapy Era.

Central nervous system (CNS) metastatic spread in neuroblastoma (NB) is rare and occurs more often at relapse/progression. We report on CNS involvement in high risk (HR) NB over 25 years. For this retrospective study, we reviewed the CNS imaging of all the patients treated at Bambino Gesù Children Hospital from 1 July 1996 to 30 June 2022. A total of 128 patients with HR NB were diagnosed over 26 years. Out of 128 patients, CNS metastatic spread occurred in 6 patients: 3 patients presented a metastatic spread at diagnosis, while in 3 patients, CNS was involved at relapse. Overall, the rate of occurrence of CNS spread is 4.7% with the same distribution at diagnosis and at relapse, namely 2.3%. Interestingly, CNS spread at diagnosis was observed only before 2012, whereas CNS was observed at relapse only after 2012, in the immunotherapy era. CNS metastases presented similar imaging features at diagnosis and at relapse, with a peculiar hemorrhagic aspect and mainly hemispheric localization in patients with bone skull involvement at the time of diagnosis. The outcome is dismal, and 3 out of 6 patients died for progressive disease.

Perineural spread of melanoma to the central nervous system

Leptomeningeal carcinomatosis is an increasingly recognized phenomenon for metastatic spread of a wide variety of carcinomas to the Central Nervous System (CNS). We report a case of a 79 year-old man with perineural spread of locally invasive melanoma to the CNS along the brachial nerves and plexus. This rarely reported mechanism of CNS spread of malignancy portends a poor prognosis and may be under-recognized because of its insidious nature and the vast number of possible differential diagnoses for neurologic symptoms in cancer patients.

Managing Central Nervous System Spread of Lung Cancer: The State of the Art

Brain metastases (BrM) are common in both non–small-cell lung cancer and small-cell lung cancer. Substantial progress in BrM management has occurred in the past decade related to advances in both radiation and medical oncology. Recent and ongoing radiation trials have focused on increasing the candidacy for focal therapy of BrM with stereotactic radiosurgery; reducing the toxicity and improving patient selection for whole brain radiotherapy; and, in small-cell lung cancer, evaluating brain magnetic resonance imaging surveillance without prophylactic cranial irradiation, hippocampal avoidance in prophylactic cranial irradiation and whole brain radiotherapy, and the role of upfront stereotactic radiosurgery for BrM. In medical oncology, the development of multiple tyrosine kinase inhibitors with encouraging CNS activity and emerging data on the CNS activity of immune checkpoint inhibitors in some patients have opened the door to novel systemic and multidisciplinary treatment strategies for the management of BrM. Future research will focus on more robust characterizations of the CNS activity of targeted therapy and immunotherapies, as well as optimal integration and patient selection for multidisciplinary strategies involving CNS-active drugs, radiation therapy, and CNS surveillance.

Craniospinal Irradiation in Patients Diagnosed with Glioblastoma with Primitive Neuronal Component Prevents Distant Intracranial and Leptomeningeal Recurrences

Glioblastoma (GBM) is the most common primary central nervous system (CNS) malignancy. In recent years, molecular and histological analyses have identified GBM with primitive neuronal component (GBM-PNC) as a distinct entity with poor regional control and worse overall prognosis. GBM-PNCs are more prone to CNS dissemination and leptomeningeal (LM) metastasis, occurring in up to 40% of patients. Given the concern for distal CNS spread, we hypothesized that craniospinal irradiation (CSI) may be an effective treatment option for GBM-PNC. We performed a retrospective chart review of patients diagnosed with GBM-PNC treated at a large academic center with institutional review board approval. Clinical, histologic and treatment characteristics, as well as disease outcomes were obtained from the electronic medical record. Ten patients diagnosed with GBM-PNC were identified in the period of 2005-2019. Median follow-up was 17 months. Overall, 80% of patients were men, median age was 49 years (range 20-64) and ECOG 0-1. Fifty percent of patients received CSI as opposed to involved field radiation therapy (IFRT). Four of five patients receiving CSI were treated with proton therapy. All patients, but one received concurrent Temozolomide. Both IFRT and CSI were tolerated well with minimal grade 3-4 toxicities. Patients treated with CSI were more likely to experience transient grade 3-4 lymphopenia (60% vs 0%). Eighty percent of patients experienced a recurrence after treatment with median progression free survival (PFS) of 13 months (range 8-26). PFS did not differ between patients receiving IFRT and CSI (14 vs 12.5 months, p = 0.9). Median overall survival (OS) was 30 months for patients who received IFRT, and median OS was not reached in the CSI group. Of the patients who received CSI as part of their treatment, all recurrences were within the high dose radiation area. On the contrary, 75% of patients who received IFRT experienced multiple recurrences at new intracranial sites and later in the leptomeninges or the spine, requiring multiple treatment courses. This hypothesis generating study demonstrates that CSI may prevent distant intracranial metastasis and LM disease progression. CSI delivered with proton therapy was well tolerated with minimal additional toxicity. A larger study is needed to guide the optimal treatment of patients diagnosed with glioblastoma with primitive neuronal component.

Clinical, Genomic, and Pharmacological Study of MYCN-Amplified RB1 Wild-Type Metastatic Retinoblastoma.

Simple SummaryWe present two cases of a subtype of retinoblastoma, a rare ocular tumor in children, presenting without the typical mutation in the RB1 gene but showing amplification of the transcription factor MYCN frequently reported in pediatric malignancies. Even though previous reports suggested that this tumor sybtype could present metastases, patients with metastatic disease were not reported. Our cases had metastasis to the orbit and lymph nodes and poor sensitivity to standard chemotherapy but no dissemination to the central nervous system, as described for patients with mutations in the RB1. We were able to grow the cells of one of our patients in vitro, perform comprehensive genomic analysis that showed previously not reported mutations and other chromosomal alterations. In an animal model, we could reproduce the clinical dissemination and we identified an innovative active drug combination that could help for the treatment of these children with poor prognosis.An uncommon subgroup of unilateral retinoblastomas with highly aggressive histological features, lacking aberrations in RB1 gene with high-level amplification of MYCN (MCYNRB1) has only been described as intra-ocular cases treated with initial enucleation. Here, we present a comprehensive clinical, genomic, and pharmacological analysis of two cases of MCYNRB1 with orbital and cervical lymph node involvement, but no central nervous system spread, rapidly progressing to fatal disease due to chemoresistance. Both patients showed in common MYCN high amplification and chromosome 16q and 17p loss. A somatic mutation in TP53, in homozygosis by LOH, and high chromosomal instability leading to aneuploidy was identified in the primary ocular tumor and sites of dissemination of one patient. High-throughput pharmacological screening was performed in a primary cell line derived from the lymph node dissemination of one case. This cell line showed resistance to broad spectrum chemotherapy consistent with the patient’s poor response but sensitivity to the synergistic effects of panobinostat–bortezomib and carboplatin–panobinostat associations. From these cells we established a cell line derived xenograft model that closely recapitulated the tumor dissemination pattern of the patient and served to evaluate whether triple chemotherapy significantly prolonged survival of the animals. We report novel genomic alterations in two cases of metastatic MCYNRB1 that may be associated with chemotherapy resistance and in vitro/in vivo models that serve as basis for tailoring therapy in these cases.

Does SARS-Cov-2 invade the brain? Translational lessons from animal models.

The current coronavirus disease (COVID‐19) outbreak, caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), has raised the possibility of potential neurotropic properties of this virus. Indeed, neurological sequelae of SARS‐CoV‐2 infection have already been reported and highlight the relevance of considering the neurological impact of coronavirus (CoV) from a translational perspective. Animal models of SARS and Middle East respiratory syndrome, caused by structurally similar CoVs during the 2002 and 2012 epidemics, have provided valuable data on nervous system involvement by CoVs and the potential for central nervous system spread of SARS‐CoV‐2. One key finding that may unify these pathogens is that all require angiotensin‐converting enzyme 2 as a cell entry receptor. The CoV spike glycoprotein, by which SARS‐CoV‐2 binds to cell membranes, binds angiotensin‐converting enzyme 2 with a higher affinity compared with SARS‐CoV. The expression of this receptor in neurons and endothelial cells hints that SARS‐CoV‐2 may have higher neuroinvasive potential compared with previous CoVs. However, it remains to be determined how such invasiveness might contribute to respiratory failure or cause direct neurological damage. Both direct and indirect mechanisms may be of relevance. Clinical heterogeneity potentially driven by differential host immune‐mediated responses will require extensive investigation. Development of disease models to anticipate emerging neurological complications and to explore mechanisms of direct or immune‐mediated pathogenicity in the short and medium term is therefore of great importance. In this brief review, we describe the current knowledge from models of previous CoV infections and discuss their potential relevance to COVID‐19.

Craniospinal irradiation in patients diagnosed with glioblastoma with primitive neuronal component prevents distant intracranial and leptomeningeal recurrences.

e14540 Background: Glioblastoma (GBM) is the most common primary central nervous system (CNS) malignancy. In recent years, molecular and histological analyses have identified GBM with primitive neuronal component (GBM-PNC) as a distinct entity with poor regional control and worse overall prognosis. GBM-PNCs are more prone to CNS dissemination and leptomeningeal (LM) metastasis, occurring in up to 40% of patients. Given the concern for distal CNS spread, we hypothesized that craniospinal irradiation (CSI) may be an effective treatment option for GBM-PNC. Methods: We performed a retrospective chart review of patients diagnosed with GBM-PNC treated at a large academic center with institutional review board approval. Clinical, histologic and treatment characteristics, as well as disease outcomes were obtained from the electronic medical record. Results: Ten patients diagnosed with GBM-PNC were identified in the period of 2005-2019. Median follow-up was 17 months. Overall, 80% of patients were men, median age was 49 years (range 20-64) and ECOG 0-1. Fifty percent of patients received CSI as opposed to involved field radiation therapy (IFRT). Four of five patients receiving CSI were treated with proton therapy. All patients, but one received concurrent Temozolomide. Both IFRT and CSI were tolerated well with minimal grade 3-4 toxicities. Patients treated with CSI were more likely to experience transient grade 3-4 lymphopenia (60% vs 0%). Eighty percent of patients experienced a recurrence after treatment with median progression free survival (PFS) of 13 months (range 8-26). PFS did not differ between patients receiving IFRT and CSI (14 vs 12.5 months, p = 0.9). Median overall survival (OS) was 30 months for patients who received IFRT, and median OS was not reached in the CSI group. Of the patients who received CSI as part of their treatment, all recurrences were within the high dose radiation area. On the contrary, 75% of patients who received IFRT experienced multiple recurrences at new intracranial sites and later in the leptomeninges or the spine, requiring multiple treatment courses. Conclusions: This hypothesis generating study demonstrates that CSI may prevent distant intracranial metastasis and LM disease progression. CSI delivered with proton therapy was well tolerated with minimal additional toxicity. A larger study is needed to guide the optimal treatment of patients diagnosed with glioblastoma with primitive neuronal component.

Identification of ALDH1A3 as a Viable Therapeutic Target in Breast Cancer Metastasis-Initiating Cells.

The development of efficacious therapies targeting metastatic spread of breast cancer to the brain represents an unmet clinical need. Accordingly, an improved understanding of the molecular underpinnings of central nervous system spread and progression of breast cancer brain metastases (BCBM) is required. In this study, the clinical burden of disease in BCBM was investigated, as well as the role of aldehyde dehydrogenase 1A3 (ALDH1A3) in the metastatic cascade leading to BCBM development. Initial analysis of clinical survival trends for breast cancer and BCBM determined improvement of breast cancer survival rates; however, this has failed to positively affect the prognostic milestones of triple-negative breast cancer (TNBC) brain metastases (BM). ALDH1A3 and a representative epithelial-mesenchymal transition (EMT) gene signature (mesenchymal markers, CD44 or Vimentin) were compared in tumors derived from BM, lung metastases (LM), or bone metastases (BoM) of patients as well as mice after injection of TNBC cells. Selective elevation of the EMT signature and ALDH1A3 were observed in BM, unlike LM and BoM, especially in the tumor edge. Furthermore, ALDH1A3 was determined to play a role in BCBM establishment via regulation of circulating tumor cell adhesion and migration phases in the BCBM cascade. Validation through genetic and pharmacologic inhibition of ALDH1A3 via lentiviral shRNA knockdown and a novel small-molecule inhibitor demonstrated selective inhibition of BCBM formation with prolonged survival of tumor-bearing mice. Given the survival benefits via targeting ALDH1A3, it may prove an effective therapeutic strategy for BCBM prevention and/or treatment.

Delayed Cerebral Metastasis of Breast Cancer: Case Report and Molecular Review

AbstractBreast cancer (BC) is a prevalent disease, and its incidence of brain metastasis (BM) varies from 5 to 30% according to the literature. We present the case of a delayed isolated cerebral metastasis in a female patient following a period of 16 years after the diagnosis and first treatment. During this time, there was no other recurrence. We also review the literature concerning central nervous system spread and the molecular subtypes of such late tumors.

Checking in on Lenalidomide in Diffuse Large B Cell Lymphoma

Lenalidomide has modest single-agent activity comparable with other newer drugs in recurrent diffuse large B cell lymphoma with response rates between 19% and 28%. Retrospective series and 1 prospective study suggest that clinically significant responses were predominantly limited to patients with activated B cell (ABC) lymphoma, a finding in agreement with lenalidomide's potent inhibition of nuclear factor κB, the key driver of ABC lymphomas. Recently completed trials will determine whether the additional use of lenalidomide with R/CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) enhances survival compared with R/CHOP alone and whether this activity is limited to ABC lymphomas. Lenalidomide also appears to have activity in the maintenance setting regardless of cell of origin and might play an important role in patients with recurrent disease who are not transplantation candidates. Similarly, because of the ability of lenalidomide to cross the blood–brain barrier, it needs to be further explored in patients with high risk for central nervous system spread. The results of lenalidomide combination studies with chemotherapy and with checkpoint inhibitors are eagerly awaited.

Multimodality therapy improves survival in intramedullary spinal cord metastasis of lung primary

BackgroundMost metastatic spinal cord lesions are located either in the intradural, extramedullary, or in the epidural compartments. Intramedullary spinal cord metastasis (ISCM) is a rare central nervous system spread of cancer. The aim of this report was to evaluate ISCM in the published literature. MethodsA literature review of PubMed from 1960 to 2016 was undertaken for the publications having demographic, clinical, histological, and outcome data. ResultsA total of 59 relevant papers were identified, showing 128 cases of intramedullary metastasis from lung cancer. The incidence of lung cancer as the primary malignancy with intramedullary metastasis was 56%. The median time from diagnosis of primary to intramedullary metastasis was 6months. Survival improved with multimodality therapy compared to monotherapy (4monthsvs. 6.3months) (hazard ratio=0.501; 95% confidence interval, 0.293–0.857). ConclusionLung cancer is the predominant cause of intramedullary involvement of the spinal cord. Overall prognosis is poor, although a multimodality approach was associated with improved survival.

Pulse-continuous dose erlotinib as initial targeted therapy for patients with EGFR-mutant lung cancers with untreated brain metastases.

9039 Background: Clarke (Neurooncol 2010) reported responses with intermittent high pulse doses of erlotinib (leading to higher concentrations in CSF) given to patients with EGFR-mutant central nervous system metastases developing on standard erlotinib doses. In a phase 1 study of pulse-continuous dose erlotinib, no patient developed progression in existing or new brain or leptomeningeal metastases (Yu Ann Oncol 2016). This phase 2 trial tested pulse-continuous dose erlotinib in patients with lung cancers with EGFRmutations with brain metastases. Methods: Patients had no prior EGFR TKI or radiation to the brain and at least 1 target brain metastasis. All received initial daily "pulse" doses of erlotinib 1200 mg days 1&2 and "continuous" 50 mg doses days 3-7 (doses and schedule from the Yu Phase 1 study), weekly until progression. The co-primary endpoints were overall and brain metastasis response by RECIST 1.1. Results: We enrolled 19 patients with EGFR-mutant lung cancers: median age 61yrs (range 45-80), 74% women, 95% Karnofsky PS ≥80%, 1 leptomeningeal disease, 33% prior pemetrexed-based chemotherapy. The median size of target brain metastases was 13 mm (range 10-19 mm). 32% were on dexamethasone for cerebral edema. The partial response rate overall was 74% (95% CI 51-89%) and also 74% in brain metastases. Of 10 patients with progression, 9/10 occurred in non-brain sites (4 EGFRT790M, 1 with progression in brain as well), 1 with leptomeningeal. The median progression free survival was 10 mo (range 7-NR mo). Pulse doses were reduced in 68% (median delivered pulse dose 1050 mg days 1&2, range 600-1200 mg). Incidences of any gradeof rash and diarrhea were 84% and 63% respectively. There were no grade 4 or 5 toxicities. Conclusions: Pulse-continuous dose erlotinib alone controlled brain and leptomeningeal metastases in 89% (95% CI 67-98%) of patients with EGFR-mutant lung cancers with central nervous system spread pretreatment, with an overall response rate of 74% and progression free survival and rates of rash and diarrhea comparable to series with erlotinib 150 mg daily. Supported by Astellas, CA 129243, CA 008748. NCT01967095 Clinical trial information: NCT01967095.

55. Aquaporins and CSF Flux Are Critical Determinants of AAV Mediated CNS Gene Transfer

The central nervous system (CNS) lacks conventional lymphatics for solute clearance. Convective currents of interstitial fluid (ISF) shunt macromolecules across the brain parenchyma into cerebrospinal fluid (CSF) compartments. Here the cargo is either reabsorbed into CNS via subarachnoid ducts or disseminated into the blood or peripheral lymph vessels. Recent studies have identified that flow of water via aquaporin (AQP) channels at the astroglial endfeet enables exchange of biomaterials between ISF and CSF. Conversely, loss of AQP expression due to aging or disease is correlated with ineffective clearance of neurodegenerative accumulations such as Amyloid β and tau. AAV mediated gene therapy of CNS disorders requires a deeper understanding of such factors and their effects on transduction efficiency and biodistribution/clearance. Here, we demonstrate that AQP mediated water transport dictates various aspects of AAV gene transfer in the CNS. We compared the CNS spread, transduction profile and systemic leakage of clinically relevant AAV vectors in wildtype (WT) or AQP knockout (AQP-/-) mice. Within minutes following intracerebroventricular (ICV) administration, AQP-/- mice exhibited highly restricted spread of fluorophore labeled AAVs when compared to wild type mice. Transgene expression was markedly increased from AAV administrations in AQP-/- mice. Further, systemic leakage and off-target transgene expression in peripheral tissues were markedly reduced for some AAV serotypes in AQP-/- mice when compared to WT mice. These results suggest that AQP-mediated water transport plays a critical role in determining the spread, transduction efficiency and systemic leakage of AAV vectors following CNS administration. We hypothesize that altered CSF flux under conditions pertinent to aging and CNS disease, can impact the residence time of AAV vectors and consequently gene transfer efficiency. Further results evaluating the CNS transport properties of AAV in mouse models of aging and disease will be presented.

The Role of VP1 Amino Acid Residue 145 of Enterovirus 71 in Viral Fitness and Pathogenesis in a Cynomolgus Monkey Model.

Enterovirus 71 (EV71), a major causative agent of hand, foot, and mouth disease, occasionally causes severe neurological symptoms. We identified P-selectin glycoprotein ligand-1 (PSGL-1) as an EV71 receptor and found that an amino acid residue 145 in the capsid protein VP1 (VP1-145) defined PSGL-1-binding (PB) and PSGL-1-nonbinding (non-PB) phenotypes of EV71. However, the role of PSGL-1-dependent EV71 replication in neuropathogenesis remains poorly understood. In this study, we investigated viral replication, genetic stability, and the pathogenicity of PB and non-PB strains of EV71 in a cynomolgus monkey model. Monkeys were intravenously inoculated with cDNA-derived PB and non-PB strains of EV71, EV71-02363-EG and EV71-02363-KE strains, respectively, with two amino acid differences at VP1-98 and VP1-145. Mild neurological symptoms, transient lymphocytopenia, and inflammatory cytokine responses, were found predominantly in the 02363-KE-inoculated monkeys. During the early stage of infection, viruses were frequently detected in clinical samples from 02363-KE-inoculated monkeys but rarely in samples from 02363-EG-inoculated monkeys. Histopathological analysis of central nervous system (CNS) tissues at 10 days postinfection revealed that 02363-KE induced neuropathogenesis more efficiently than that induced by 02363-EG. After inoculation with 02363-EG, almost all EV71 variants detected in clinical samples, CNS, and non-CNS tissues, possessed a G to E amino acid substitution at VP1-145, suggesting a strong in vivo selection of VP1-145E variants and CNS spread presumably in a PSGL-1-independent manner. EV71 variants with VP1-145G were identified only in peripheral blood mononuclear cells in two out of four 02363-EG-inoculated monkeys. Thus, VP1-145E variants are mainly responsible for the development of viremia and neuropathogenesis in a non-human primate model, further suggesting the in vivo involvement of amino acid polymorphism at VP1-145 in cell-specific viral replication, in vivo fitness, and pathogenesis in EV71-infected individuals.

265. Polysialic Acid as a Novel Regulator of AAV Tropism in the Developing Brain

Recombinant AAV vectors are currently being exploited in a number of clinical trials that aim to correct neurological diseases. In many cases, it is important that therapeutic intervention occurs in the infantile stage of life. Thus, it is important to understand how AAV vectors interact with the constantly changing environment in the brain during neurodevelopment. Recombinant AAV is thought to spread through the central nervous system (CNS) by exploiting cerebrospinal fluid (CSF) flux and hijacking axonal transport pathways. The role of host receptors that mediate these processes in the developing brain are not well understood. In the current study, we utilized AAV serotype 4 as a model to evaluate whether ubiquitously expressed 2,3-linked sialic acid and the developmentally regulated marker, 2,8-linked polysialic acid (PSA) regulate viral transport and tropism in the neonatal brain. Modulation of the levels of SA and PSA in cell culture studies using specific neuraminidases revealed possibly opposing roles of the two glycans on AAV4 transduction. Interestingly, upon intracranial injection into lateral ventricles of the neonatal mouse brain, a low affinity AAV4 mutant displayed a striking shift in cellular tropism from 2,3-linked SA+ ependymal lining to 2,8-linked PSA+ migrating progenitors in the rostral migratory stream and olfactory bulb. In addition, this gain-of-function phenotype correlated with robust CNS spread of the mutant through paravascular transport pathways. Consistent with these observations, altering glycan dynamics within the brain by co-administering SA and PSA specific neuraminidases resulted in striking changes to the cellular tropisms and transduction efficiencies of both parental and mutant vectors. We postulate that glycan signatures associated with host development can be exploited to redirect novel AAV vectors to specific cell types in the brain.

Unique Glycan Signatures Regulate Adeno-Associated Virus Tropism in the Developing Brain

Adeno-associated viruses (AAV) are thought to spread through the central nervous system (CNS) by exploiting cerebrospinal fluid (CSF) flux and hijacking axonal transport pathways. The role of host receptors that mediate these processes is not well understood. In the current study, we utilized AAV serotype 4 (AAV4) as a model to evaluate whether ubiquitously expressed 2,3-linked sialic acid and the developmentally regulated marker 2,8-linked polysialic acid (PSA) regulate viral transport and tropism in the neonatal brain. Modulation of the levels of SA and PSA in cell culture studies using specific neuraminidases revealed possibly opposing roles of the two glycans in AAV4 transduction. Interestingly, upon intracranial injection into lateral ventricles of the neonatal mouse brain, a low-affinity AAV4 mutant (AAV4.18) displayed a striking shift in cellular tropism from 2,3-linked SA(+) ependymal lining to 2,8-linked PSA(+) migrating progenitors in the rostral migratory stream and olfactory bulb. In addition, this gain-of-function phenotype correlated with robust CNS spread of AAV4.18 through paravascular transport pathways. Consistent with these observations, altering glycan dynamics within the brain by coadministering SA- and PSA-specific neuraminidases resulted in striking changes to the cellular tropisms and transduction efficiencies of both parental and mutant vectors. We postulate that glycan signatures associated with host development can be exploited to redirect novel AAV vectors to specific cell types in the brain. Viruses invade the CNS through various mechanisms. In the current study, we utilized AAV as a model to study the dynamics of virus-carbohydrate interactions in the developing brain and their impact on viral tropism. Our findings suggest that carbohydrate content can be exploited to regulate viral transport and tropism in the brain.

Pars Plana Vitrectomy for Vitreous Floaters

Pars Plana Vitrectomy for Vitreous Floaters

Early Detection of Simian Immunodeficiency Virus in the Central Nervous System Following Oral Administration to Rhesus Macaques

The timing of HIV dissemination to the central nervous system (CNS) has the potential to have important implications regarding HIV disease progression and treatment. The earlier HIV enters the CNS the more difficult it might be to remove with antiretroviral therapy. Alternatively, HIV may only enter the CNS later in the course of disease as a result of disruption of the blood-brain-barrier. We utilized the simian immunodeficiency virus (SIV) infection of rhesus macaques to evaluate the oral route of infection and the subsequent spread of SIV to the CNS during the acute infection phase. A high dose oral SIV challenge was utilized to ensure a successful infection and permit the evaluation of CNS spread during the first 1–14 days post-infection. Ultrasensitive nested PCR was used to detect SIV gag DNA in the brains of macaques at 1–2 days post-infection and identified SIV gag DNA in the brain tissues from three of four macaques. This SIV DNA was also present following perfusion of the macaque brains, providing evidence that it was not residing in the circulating blood but in the brain tissue itself. The diversity of the viral envelope V1–V2 region at early times post-infection indicated that the brain viral variants were similar to variants obtained from lymph nodes. This genetic similarity between SIV obtained from lymphoid and brain tissues suggests that the founder population of viral species entered and subsequently spread without any evidence of brain-specific SIV selection. The relatively rapid appearance of SIV within the CNS tissue following oral transmission may also occur during HIV transmission where it may impact disease course as well as representing a challenge for long-term therapies and future viral eradication modalities.