Hitchhiking Across Kingdoms: Cotransport of Cargos in Fungal, Animal, and Plant Cells.

Eukaryotic cells across the tree of life organize their subcellular components via intracellular transport mechanisms. In canonical transport, myosin, kinesin, and dynein motor proteins interact with cargos via adaptor proteins and move along filamentous actin or microtubule tracks. In contrast to this canonical mode, hitchhiking is a newly discovered mode of intracellular transport in which a cargo attaches itself to an already-motile cargo rather than directly associating with a motor protein itself. Many cargos including messenger RNAs, protein complexes, and organelles hitchhike on membrane-bound cargos. Hitchhiking-like behaviors have been shown to impact cellular processes including local protein translation, long-distance signaling, and organelle network reorganization. Here, we review instances of cargo hitchhiking in fungal, animal, and plant cells and discuss the potential cellular and evolutionary importance of hitchhiking in these different contexts.

Optimizing microtubule arrangements for rapid cargo capture.

Cellular functions such as autophagy, cell signaling, and vesicular trafficking involve the retrograde transport of motor-driven cargo along microtubules. Typically, newly formed cargo engages in slow undirected movement from its point of origin before attaching to a microtubule. In some cell types, cargo destined for delivery to the perinuclear region relies on capture at dynein-enriched loading zones located near microtubule plus ends. Such systems include extended cell regions of neurites and fungal hyphae, where the efficiency of the initial diffusive loading process depends on the axial distribution of microtubule plus ends relative to the initial cargo position. We use analytic mean first-passage time calculations and numerical simulations to model diffusive capture processes in tubular cells, exploring how the spatial arrangement of microtubule plus ends affects the efficiency of retrograde cargo transport. Our model delineates the key features of optimal microtubule arrangements that minimize mean cargo capture times. Namely, we show that configurations with a single microtubule plus end abutting the distal tip and broadly distributed other plus ends allow for efficient capture in a variety of different scenarios for retrograde transport. Live-cell imaging of microtubule plus ends in Aspergillus nidulans hyphae indicates that their distributions exhibit these optimal qualitative features. Our results highlight important coupling effects between the distribution of microtubule tips and retrograde cargo transport, providing guiding principles for the spatial arrangement of microtubules within tubular cell regions.

PxdA interacts with the DipA phosphatase to regulate peroxisome hitchhiking on early endosomes.

In canonical microtubule-based transport, adaptor proteins link cargoes to dynein and kinesin motors. Recently, an alternative mode of transport known as "hitchhiking" was discovered, where cargoes achieve motility by hitching a ride on already-motile cargoes, rather than attaching to a motor protein. Hitchhiking has been best studied in two filamentous fungi, Aspergillus nidulans and Ustilago maydis. In U. maydis, ribonucleoprotein complexes, peroxisomes, lipid droplets (LDs), and endoplasmic reticulum hitchhike on early endosomes (EEs). In A. nidulans, peroxisomes hitchhike using a putative molecular linker, peroxisome distribution mutant A (PxdA), which associates with EEs. However, whether other organelles use PxdA to hitchhike on EEs is unclear, as are the molecular mechanisms that regulate hitchhiking. Here we find that the proper distribution of LDs, mitochondria, and preautophagosomes do not require PxdA, suggesting that PxdA is a peroxisome-specific molecular linker. We identify two new pxdA alleles, including a point mutation (R2044P) that disrupts PxdA's ability to associate with EEs and reduces peroxisome movement. We also identify a novel regulator of peroxisome hitchhiking, the phosphatase DipA. DipA colocalizes with EEs and its association with EEs relies on PxdA. Together, our data suggest that PxdA and the DipA phosphatase are specific regulators of peroxisome hitchhiking on EEs.

Topical Vitamin D May Modulate Human Sinonasal Mucosal Responses to House Dust Mite Antigen.

BACKGROUND: Respiratory epithelium is a key defense against inhaled pathogens. Vitamin D3 (VD) has been suggested to modulate airway inflammation; however, its effect on innate airway defenses, the physical barrier, mucociliary apparatus, and cytokine release remains unclear. OBJECTIVE: To investigate the outcomes of VD application prior to challenge in an in vitro model of human sinonasal epithelium, through assessment of epithelial transepithelial resistance (TER), cilia beat frequency (CBF), and interleukin (IL)-6 release, and secondarily to determine whether topical VD is beneficial to patients with inflammatory sinonasal pathology. METHODS: Primary human sinonasal epithelial cells from patients with eosinophilic chronic rhinosinusitis (eCRS) and healthy controls were cultured in air-liquid interface (ALI). Well-differentiated cultures from each patient were pretreated for 24 hours with 4 different VD doses. Toxicity was quantified at 24 hours in unchallenged ALI by lactate dehydrogenase (LDH) assay. Innate responses were assessed by measuring TER and CBF before and up to 24 hours after house dust mite Dermatophagoides pteronyssinus challenge. IL-6 release was evaluated 24-hour postchallenge. RESULTS: Fifteen patients (53 ± 13.5 years, 60% females, 53% eCRS) representing 120 ALI wells were assessed. VD (0, 25, 50, 150 IU/mL) released less LDH than vehicle, indicating noncytotoxicity (0.15 ± 0.02; 0.15 ± 0.00; 0.14 ± 0.02; 0.11 ± 0.01 vs 0.17 ± 0.03, P = .004). VD increased TER for eCRS wells at 5 minutes (50 IU/mL: Δ6.76 ± 3.93 vs Δ3.87 ± 2.46, P = .04) and 24 hours (50 IU/mL: Δ0.88 ± 0.49 vs Δ0.40 ± 0.42, P = .02; 150 IU/mL: Δ1.06 ± 0.58 vs Δ0.47 ± 0.46, P = .01). CBF increased at 1 hour for eCRS wells (50 IU/mL: Δ0.62 ± 0.14 vs Δ0.41 ± 0.13, P = .001; 150 IU/ml: Δ0.60 ± 0.13 vs Δ0.38 ± 0.11, P < .001). IL-6 release was similar between normal and eCRS wells. CONCLUSION: Topical VD supplementation in eCRS patients may be beneficial for innate epithelial defenses. VD is noncytotoxic and does not adversely affect the physical barrier, mucociliary apparatus, or IL-6 release. Further studies should clarify its potential as a therapeutic agent.

Hitching a Ride: Mechanics of Transport Initiation through Linker-Mediated Hitchhiking.

In contrast to the canonical picture of transport by direct attachment to motor proteins, recent evidence shows that a number of intracellular "cargos" navigate the cytoplasm by hitchhiking on motor-driven "carrier" organelles. We describe a quantitative model of intracellular cargo transport via hitchhiking, examining the efficiency of hitchhiking initiation as a function of geometric and mechanical parameters. We focus specifically on the parameter regime relevant to the hitchhiking motion of peroxisome organelles in fungal hyphae. Our work predicts the dependence of transport initiation rates on the distribution of cytoskeletal tracks and carrier organelles, as well as the number, length, and flexibility of the linker proteins that mediate contact between the carrier and the hitchhiking cargo. Furthermore, we demonstrate that attaching organelles to microtubules can result in a substantial enhancement of the hitchhiking initiation rate in tubular geometries such as those found in fungal hyphae. This enhancement is expected to increase the overall transport rate of hitchhiking organelles and lead to greater efficiency in organelle dispersion. Our results leverage a quantitative physical model to highlight the importance of organelle encounter dynamics in noncanonical intracellular transport.

Association Between Mental Health Status and Patient Satisfaction With the Functional Outcomes of Rhinoplasty.

IMPORTANCE: Mental health can have an impact on patient satisfaction with rhinoplasty. However, the association between mental health and patient satisfaction with functional outcomes of rhinoplasty is poorly understood. OBJECTIVE: To determine whether preoperative mental health is associated with satisfaction with functional outcomes of rhinoplasty. DESIGN, SETTING, AND PARTICIPANTS: This case-control study assessed baseline nasal function and postsurgical functional outcomes for 88 consecutive patients undergoing rhinoplasty with both cosmetic and functional goals at 2 tertiary rhinologic centers in Sydney, Australia. EXPOSURES: Poor mental well-being was defined preoperatively by the Optum SF-36v2 Health Survey mental component summary. MAIN OUTCOMES AND MEASURES: Nasal function was assessed with patient-reported outcome measures, including visual analog scales, the Nasal Obstruction Symptom Evaluation Scale (NOSE), the 22-item Sinonasal Outcome Test (SNOT-22), and Likert scales. Objective outcomes included nasal peak inspiratory flow, nasal airway resistance, and minimum cross-sectional area. All outcomes were assessed preoperatively and 6 months postoperatively. The 36-item Optum SF-36v2 Health Survey mental component summary was used to assess mental well-being, with a score of less than 40 indicating poor mental well-being and a score 40 or higher indicating normal well-being. RESULTS: Mean (SD) patient age was 37.6 (12.9) years and 53 of 88 (60.2%) were women. The mental component summary defined impaired well-being in n = 24 (cases) and normal well-being in n = 64 (controls). There were improvements in the total study population across most nasal function outcomes and in both groups. After rhinoplasty, benefit was seen for both groups in visual analog scale (left side mean [SD] change, 18 [30]; P < .001 and right side mean [SD] change, 24 [30]; P < .001); NOSE (mean [SD] change, 1.35 [1.21]; P < .001); and SNOT-22 (mean [SD] change, 0.81 [0.88]; P < .001) scores. Nasal peak inspiratory flow improved for both groups (mean [SD] change, 32 [45] L/min; P < .001), while nasal airway resistance and minimum cross-sectional area remained similar (change in nasal airway resistance, 0.086 Pa/cm3/s; 95% CI, -0.007 Pa/cm3/s to 0.179 Pa/cm3/s and change in minimum cross-sectional area, -0.04 cm2; 95% CI, -0.21 cm2 to 0.13 cm2). Patients with poor mental health had similar improvements in nasal function compared with controls. CONCLUSIONS AND RELEVANCE: Rhinoplasty imparts similar benefits to nasal function assessed by patient-reported outcome measures and objective airflow measures regardless of preoperative mental health status. LEVEL OF EVIDENCE: 3.

Association of Mental Health Status With Perception of Nasal Function.

IMPORTANCE: Mental health issues are thought to be overrepresented among patients undergoing rhinoplasty and may be associated with patient presentation prior to surgery. OBJECTIVE: To assess the association of poor mental health with perception of nasal function. DESIGN, SETTING, AND PARTICIPANTS: A cross-sectional study of patients presenting for airway assessment was performed from December 1, 2011, to October 31, 2015, at 2 tertiary rhinoplasty centers in Sydney, Australia. Mental health was independently defined preoperatively by the Mental Component Summary of the 36-item Short Form Health Survey version 2 (a score of <40 indicated poor mental well-being), the Rosenberg Self-Esteem Scale (a score of <15 indicated low self-esteem), and the Dysmorphic Concerns Questionnaire (a score of >11 indicated above-average dysmorphic concerns). MAIN OUTCOMES AND MEASURES: Nasal function was assessed with patient-reported outcome measures, including the Nasal Obstruction Symptom Evaluation Scale, the 22-item Sinonasal Outcome Test, a visual analog scale to rate ease of breathing on the left and right sides, and Likert scales to assess overall function and nasal obstruction. Nasal airflow was assessed by nasal peak inspiratory flow, nasal airway resistance, and minimum cross-sectional area. RESULTS: Among 495 patients in the study (302 women and 193 men; mean [SD] age, 36.5 [13.6] years), compared with patients with good mental health, those with poor mental health had poorer scores in all patient-reported outcome measures, including the visual analog scale for the left side (mean [SD], 51 [25] vs 42 [25]; P = .001), visual analog scale for the right side (mean [SD], 54 [24] vs 45 [26]; P < .001), Nasal Obstruction Symptom Evaluation Scale (mean [SD], 2.64 [0.95] vs 1.96 [1.04]; P < .001), 22-item Sinonasal Outcome Test (mean [SD], 2.14 [0.84] vs 1.33 [0.83]; P < .001), nasal obstruction (58 of 145 [40.2%] vs 83 of 350 [23.7%] with severe or worse obstruction; P < .001), and nasal function (72 of 145 [49.7%] vs 111 of 350 [31.8%] with poor or worse function; P < .001). Subclinical differences in nasal peak inspiratory flow could be demonstrated, but all other nasal airflow measures were similar. Low self-esteem produced a similar pattern, but dysmorphia did not. CONCLUSIONS AND RELEVANCE: Poor mental health status is associated with a poorer self-perception of nasal function compared with those who are mentally healthy with clinically similar nasal airflow. Clinicians should be aware that patients with poor mental health reporting obstructed airflow may in part be representing an extension of their negative emotions rather than true obstruction and may require further assessment prior to surgery. LEVEL OF EVIDENCE: NA.

Allergic sensitization does not predispose to sinus inflammation in externalized paranasal sinuses.

BACKGROUND: Chronic rhinosinusitis (CRS) has a multifactorial etiology, with a debate about the role of inhalant allergy in the pathogenesis of CRS. OBJECTIVE: This study assessed the impact of allergy status on externalized paranasal sinuses after tumor resection to determine if a predisposition to inhalant allergy brought about additional inflammation after sinus surgery. METHODOLOGY: A case-control study was performed on patients who had no history of CRS who underwent paranasal sinus tumor resection. Allergic sensitization was defined by a positive serum ImmunoCAP test result. Outcomes were measured at least 6 months after surgery by using the modified Lund-MacKay endoscopic score and the 22-item Sino-Nasal Outcome test, with rhinitis, sleep, psychological, ear and/or facial, and sinus subscores to assess the impact of allergy status on mucosal inflammation. RESULTS: A total of 103 patients (53.44 ± 17.46 years; 46% women) were assessed. Of these, 61.17% were allergically sensitized at the time of surgery. Postsurgery endoscopic assessment was similar [the modified Lund-Mackay endoscopic score allergic sensitized 0.5 (1.7) versus nonallergic sensitized 0.0 (0.9); p = 0.15]. Sinonasal symptoms were also similar between the groups' 22-item Sino-Nasal Outcome test scores, allergic sensitized versus allergic nonsensitized, (allergic 28.9 ± 20.8 versus nonallergic 33.5 ± 19.7; p = 0.31), rhinitis score (5.9 ± 5.5 versus 6.4 ± 4.7; p = 0.66), sleep score (6.9 ± 5.9 versus 7.7 ± 4.8; p = 0.50), ear and/or facial symptom score (3.4 ± 3.6 versus 4.3 ± 3.3; p = 0.22), psychological score (6.9 ± 6.0 versus 8.3 ± 6.7; p = 0.29), and of nasal symptom score (6.4 ± 5.2 versus 7.0 ± 5.3; p = 0.61). CONCLUSIONS: Externalization of the sinuses in patients with inhalant allergy did not bring about significant additional inflammation in patients after tumor surgery.

Middle turbinate edema as a diagnostic marker of inhalant allergy.

BACKGROUND: Middle turbinate edema could be a characteristic feature of aeroallergen sensitization. In this study we sought to determine the diagnostic characteristics of middle turbinate edema as a marker of inhalant allergy. METHODS: A cross-sectional diagnostic study was performed on patients who had undergone nasal endoscopy and allergy testing. Allergy status was determined by positive serology or epicutaneous testing. Endoscopy was reviewed by blinded assessors for middle turbinate head edema. Appearance was graded as either normal, focal, multifocal, diffuse, or polypoid edema. Receiver-operator (ROC) analysis, likelihood ratio (LR), sensitivity, specificity, and positive predictive value (PPV) were determined. RESULTS: One hundred eighty-seven patients representing 304 nasal cavities were assessed (42% female, age 39.74 ± 14.7 years, 57% allergic). Diffuse edema (PPV 91.7%/LR = 8) and polypoid edema (PPV 88.9%/LR = 6.2) demonstrated the strongest association with inhalant allergy. Multifocal edema was used as a cut-off to represent inhalant allergy from ROC analysis, which demonstrated 94.7% specificity and 23.4% sensitivity. The PPV for multifocal was 85.1% and LR = 4.4. CONCLUSION: Middle turbinate edema is a useful nasal endoscopic feature to predict presence of inhalant allergy and, although not sensitive, has excellent PPV.

Vitamin D pathway regulatory genes encoding 1α-hydroxylase and 24-hydroxylase are dysregulated in sinonasal tissue during chronic rhinosinusitis.

BACKGROUND: Vitamin D deficiency is associated with many inflammatory respiratory disease states. However, serum vitamin D concentrations may not reflect tissue-specific availability. In this study we sought to assess the local expression of genes essential in vitamin D regulation in chronic rhinosinusitis (CRS). METHODS: A cross-sectional study of adult patients undergoing endoscopic sinus surgery was performed. Patients were defined as having CRS with polyps (CRSwNP) or without polyps (CRSsNP), or normal sinus mucosa. Sinus mucosal biopsies were assessed using quantitative polymerase chain reaction to determine expression of genes encoding the vitamin D receptor (VDR), 25-hydroxylase (CYP2R1), 1α-hydroxylase (CYP27B1), and 24-hydroxylase (CYP24A1). Expression levels correlated with serum 25(OH)D [sum 25(OH)D2  and 25(OH)D3 ], the 22-item Sinonasal Outcome Test (SNOT-22), and Nasal Symptom Score (NSS). Separate analyses were performed for patients grouped by tissue eosinophilia. RESULTS: Thirty-one patients were assessed (age 49.47 ± 18.14 years, 48.4% female), including 8 CRSsNP, 10 CRSwNP, and 13 controls. CRSsNP and CRSwNP mucosa exhibited decreased CYP27B1 compared with controls (0.0437 [Interquartile range (IQR) 0.0999] vs 0.3260 [IQR 2.9384] vs 0.6557 [IQR 1.1005], p = 0.039), whereas CYP24A1 was upregulated (0.8522 [IQR 1.3170] vs 1.2239 [IQR 4.4197] vs 0.1076 [IQR 0.1791], p = 0.025). CYP24A1 was upregulated in both non-eosinophilic CRS and eosinophilic CRS (1.1337 [IQR 2.3790] vs 0.9555 [IQR 3.2811] vs 0.1076 [IQR 0.1791], p = 0.033). Significant correlations were observed between NSS and CYP2R1 (r = -0.432, p = 0.022), CYP24A1 (r = 0.420, P = 0.026), and VDR (r = 0.425, p = 0.024), although no correlations with serum 25(OH)D were observed. CONCLUSIONS: The local regulation of vitamin D in sinonasal tissue during CRS may be independent of serum 25(OH)D levels. Vitamin D may be dysregulated at multiple levels, with decreased transcription of the metabolic gene CYP27B1 and increased transcription of the catabolic gene CYP24A1 observed.

Clinical implications of mucosal remodeling from chronic rhinosinusitis.

BACKGROUND: Prognostic implications of mucosal remodeling in chronic rhinosinusitis (CRS) remain unclear. Remodeling of respiratory mucosa in asthma is associated with greater medication use and decreased function. This study investigates the implications of mucosal remodeling on long-term clinical outcomes in patients with CRS. METHODS: A case-control study of adult patients with CRS undergoing endoscopic sinus surgery (ESS) was performed. Mucosal remodeling was defined by squamous metaplasia, subepithelial fibrosis, and/or basement membrane thickening. The presence of remodeling changes were assessed relative to clinical and treatment outcomes at a minimum of 12 months postoperatively. Clinical outcomes were assessed at baseline and 12 months using a Nasal Symptom Score (NSS) and 22-item Sino-Nasal Outcome Test (SNOT-22). Treatment outcomes were assessed by oral corticosteroid usage (burst/continuous), topical corticosteroid irrigation frequency, and further surgical intervention. RESULTS: A total of 110 patients (48.73 ± 14.75 years, 48.2% female) were assessed. Significant improvements where seen for the entire population, in both NSS (2.64 ± 1.06 to 1.34 ± 1.08, p < 0.001) and SNOT-22 (2.05 ± 0.96 to 1.06 ± 0.79, p < 0.001). Patients with remodeling (n = 88) were younger (47.2 ± 14.8 vs 54.7 ± 13.5 years, p = 0.03), but had similar symptom scores. Remodeling was seen in CRS with nasal polyposis (CRSwNP) (54.5%) and eosinophilic chronic rhinosinusitis (eCRS) (59.8%). Symptom improvement at 12 months was similar between remodeled and non-remodeled groups (NSS: Δ1.34 ± 1.20 vs Δ1.12 ± 1.31, p = 0.395; SNOT-22: Δ1.05 ± 0.91 vs Δ0.73 ± 0.95, p = 0.124); however, patients with remodeling had greater corticosteroid irrigation frequency (64.0% vs 31.6% daily use, Kendall's tau-b p = 0.004). CONCLUSION: Established mucosal remodeling predicts a greater reliance on topical therapies to reach similar clinical endpoints as those without remodeling.

Topical concentrated epinephrine (1:1000) does not cause acute cardiovascular changes during endoscopic sinus surgery.

BACKGROUND: Topical epinephrine is used in endoscopic sinonasal surgery for local vasoconstriction. Potential for cardiovascular complications remains a concern for some due to the possibility of systemic absorption. Topical vs injected epinephrine was examined in a prospective analysis of perioperative cardiovascular effects, and in an audit of cardiovascular complications during endoscopic sinonasal surgery. METHODS: A prospective cohort study of patients undergoing endoscopic sinonasal surgery was performed. Topical (1:1000) and injected (1:100,000) epinephrine were assessed. Cardiovascular outcomes of heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and electrocardiogram (ECG) changes were examined at baseline and minutely post-topical application (to 10 minutes) and postinjection (to 5 minutes). A retrospective assessment of cardiovascular events associated with a standardized regimen of topical (1:2000) and injected (1:100,000) epinephrine was performed. RESULTS: Nineteen patents were assessed (43.42 ± 15.90 years, 47.4% female) in the prospective analysis. Post-topical epinephrine, no significant changes occurred in any cardiovascular parameter. However, following injected epinephrine, changes in HR (59.53 vs 64.11 bpm, p < 0.001), SBP (96.16 vs 102.95 mmHg, p = 0.015), DBP (56.53 vs 60.74 mmHg, p = 0.019), and MAP (69.74 vs 74.81 mmHg, p = 0.002) occurred. On repeated-measures analysis of variance (ANOVA) all parameters were significantly affected by injection. No ECG abnormalities were seen in either topical or injection phases. The retrospective analysis of 1260 cases identified 2 cases of cardiovascular complications (0.16%), both relating to injected epinephrine. CONCLUSION: Combination topical (1:1000 to 1:2000) and injectable (1:100,000) epinephrine is safe for use in endoscopic sinonasal surgery. Injection resulted in the cardiovascular changes and accounted for the cardiovascular events reported.

Costal Cartilage Lateral Crural Strut Graft vs Cephalic Crural Turn-in for Correction of External Valve Dysfunction.

IMPORTANCE: External nasal valve dysfunction (EVD) is a common cause of nasal obstruction. OBJECTIVE: To evaluate costal cartilage lateral crural strut grafts vs cephalic crural turn-in to support the weak lateral crus in patients with EVD. DESIGN, SETTING, AND PARTICIPANTS: In this prospective cohort study, patients with clinically diagnosed EVD were assessed at the Tertiary Rhinologic Center and underwent a costal cartilage underlay graft to the lateral crus or a cephalic turn-in cruralplasty. MAIN OUTCOMES AND MEASURES: Assessment of patient benefit was based on 22-Item Sinonasal Outcome Test (SNOT-22) and Nasal Obstruction Symptom Evaluation Scale (NOSE) scores. A Likert scale was also used to assess overall function and cosmesis. Objective assessment included postdecongestion nasal peak inspiratory flow, nasal airway resistance, and minimum cross-sectional area. RESULTS: Forty-one patients (mean [SD] 35.38 [12.73] years of age; 25 [61%] female) were assessed. Cephalic turn-in maneuver was used for 25 (61%) patients; costal cartilage lateral crural strut grafts, 16 (39%) patients. Costal cartilage grafts were used in patients undergoing revision but other baseline data were similar. Follow-up was mean 10.58 (7.52) months. All patients had significantly improved visual analog scale, SNOT-22, NOSE, patient-reported function, and cosmesis scores. The only objective test that improved was nasal peak inspiratory flow (114.76 [60.48] L/min vs 126.46 [61.17] L/min; P = .02). CONCLUSIONS AND RELEVANCE: Both techniques were effective in improving patient-reported outcomes and nasal peak inspiratory flow. Both are functionally and cosmetically viable options for correction of EVD. LEVEL OF EVIDENCE: 2.

Varicella-zoster virus glycoprotein I is essential for spread in dorsal root ganglia and facilitates axonal localization of structural virion components in neuronal cultures.

Neurons of the sensory ganglia are the major site of varicella-zoster virus (VZV) latency and may undergo productive infection during reactivation. Although the VZV glycoprotein E/glycoprotein I (gE/gI) complex is known to be critical for neurovirulence, few studies have assessed the roles of these proteins during infection of dorsal root ganglia (DRG) due to the high human specificity of the virus. Here, we show that the VZV glycoprotein I gene is an important neurotropic gene responsible for mediating the spread of virus in neuronal cultures and explanted DRG. Inoculation of differentiated SH-SY5Y neuronal cell cultures with a VZV gI gene deletion strain (VZV rOkaΔgI) showed a large reduction in the percentage of cells infected and significantly smaller plaque sizes in a comparison with cultures infected with the parental strain (VZV rOka). In contrast, VZV rOkaΔgI was not significantly attenuated in fibroblast cultures, demonstrating a cell type-specific role for VZV gI. Analysis of rOkaΔgI protein localization by immunofluorescent staining revealed aberrant localization of viral glycoprotein and capsid proteins, with little or no staining present in the axons of differentiated SH-SY5Y cells infected with rOkaΔgI, yet axonal vesicle trafficking was not impaired. Further studies utilizing explanted human DRG indicated that VZV gI is required for the spread of virus within DRG. These data demonstrate a role for VZV gI in the cell-to-cell spread of virus during productive replication in neuronal cells and a role in facilitating the access of virion components to axons.

Differentiated neuroblastoma cells provide a highly efficient model for studies of productive varicella-zoster virus infection of neuronal cells.

Varicella-zoster virus (VZV) is a highly species-specific herpesvirus that targets sensory ganglionic neurons. This species specificity has limited the study of many aspects of VZV pathogenesis, including neuronal infection. We report development of a highly efficient neuroblastoma cell model to study productive VZV infection of neuronal cells. We show that differentiation of SH-SY5Y neuroblastoma cells yields a homogenous population of neuron-like cells that are permissive to the full VZV replicative cycle. These cells supported productive infection by both laboratory and clinical VZV isolates, including the live varicella vaccine. This model may enable rapid identification of genetic determinants facilitating VZV neurotropism.