Development of Intratumoral Drug Delivery Based Strategies for Antitumor Therapy.

Research for tumor treatment with significant therapy effects and minimal side-effects has been widely carried over the past few decades. Different drug forms have received a lot of attention. However, systemic biodistribution induces efficacy and safety issues. Intratumoral delivery of agents might overcome these problems because of its abundant tumor accumulation and retention, thereby reducing side effects. Delivering hydrogels, nanoparticles, microneedles, and microspheres drug carriers directly to tumors can realize not only targeted tumor therapy but also low side-effects. Furthermore, intratumoral administration has been integrated with treatment strategies such as chemotherapy, enhancing radiotherapy, immunotherapy, phototherapy, magnetic fluid hyperthermia, and multimodal therapy. Some of these strategies are ongoing clinical trials or applied clinically. However, many barriers hinder it from being an ideal and widely used option, such as decreased drug penetration impeded by collagen fibers of a tumor, drug squeezed out by high density and high pressure, mature intratumoral injection technique. In this review, we systematically discuss intratumoral delivery of different drug carriers and current development of intratumoral therapy strategies.

A comparative evaluation of intranasal α2-adrenoceptor agonists and intranasal midazolam as premedication in pediatric sedation: A meta-analysis of randomized controlled trials.

BACKGROUND: Midazolam and α2-adrenoceptor agonists have been widely used off-label as intranasal sedatives for children. The present meta-analysis aimed to evaluate the effects of two interventions in pediatric sedation. METHODS: PubMed, Embase, and Cochrane Library were searched from inception to April 2022. All randomized controlled trials used intranasal α2-adrenoceptor agonists and midazolam as sedatives in children were enrolled. Parental separation, anesthesia induction or facemask acceptance, sedation level, different hemodynamic parameters and adverse events were considered as outcomes. RESULTS: Totally 21 studies with 1,495 patients were included. Only one study reported comparison between midazolam and clonidine met the inclusion criteria, and patients in clonidine group had significantly better mask acceptance compared to midazolam group. Compared with midazolam, using of dexmedetomidine was associated with higher rate of satisfactory parental separation (52.88% vs 75.18%, RR = 0.70, with 95%CI [0.55, 0.90]), anesthesia induction or facemask acceptance (60.92% vs 81.47%, RR = 0.76, 95% CI [0.68, 0.84]) and less incidence of postoperative pain and nasal irritation. CONCLUSION: Compared with midazolam, dexmedetomidine should be considered as the preferred intranasal sedative option for pediatric patients, since it provides more satisfactory sedative level with less incidence of several side effects. But insufficient evidences about effects of intranasal clonidine and overall low and moderate quality evidences evaluated by GRADE system indicate that superiority of intranasal α2-adrenoceptor agonists in pediatric sedation needs to be validated by more studies with high quality and large sample size in future.

A cross-sectional study on knowledge and behavior regarding medication usage among guardians of left-behind children: evidence from China.

PURPOSE: The primary objective of this study was to evaluate knowledge and behavior of medication use among guardians of left-behind children (LBC) and non-left-behind children (NLBC). METHODS: A cross-sectional study was conducted in Chengdu, the major city of southwestern China from May 2020 to August 2020. A logistic regression model was conducted to assess medication-related knowledge and behavior of guardians between the LBC group and NLBC group, adjusted for confounders. Stratified analysis was further performed. RESULTS: The overall mean scores for knowledge and for behavior were 20.22 (standard deviation = 4.472) and 15.77 (standard deviation = 3.604), respectively. No significant difference was found in medication-related knowledge and behavior scores between LBC and NLBC guardians (P > 0.05). A significant difference was only observed after adjusting for past medical history and history of present illness (HPI). CONCLUSION: There was no significant difference in the awareness and behavior of medication use between guardians of LBC and NLBC in this study, having more contact with the doctor was an effective method of health education that could possibly improve their health literacy.

Efficacy and safety of intranasal midazolam versus intranasal ketamine as sedative premedication in pediatric patients: a meta-analysis of randomized controlled trials.

BACKGROUND: Intranasal midazolam and ketamine have been widely used as sedative premedication in children. It is difficult to determine which one yields better sedative effects for clinical practice. We conducted the present meta-analysis by summarizing the evidences to evaluate the efficacy and safety of intranasal midazolam versus intranasal ketamine as sedative premedication in pediatric patients. METHODS: We searched PubMed, Embase, and Cochrane Library from inception to April 2022. All randomized controlled trials (RCTs) used intranasal midazolam and ketamine as sedatives in children were enrolled. The risk of bias in RCTs was assessed by Cochrane risk of bias tool. Condition of parental separation, anesthesia induction or facemask acceptance, sedation level, different hemodynamic parameters and adverse events were considered as the outcomes in our study. RESULTS: A total of 16 studies with 1066 patients were enrolled. Compared with midazolam, administration of intranasal ketamine might be associated with severer changes in hemodynamics parameters including mean blood pressure (SMD = -0.53, with 95% CI [-0.93, -0.13]) and heart rate (HR) (SMD = -1.39, with 95% CI [-2.84, 0.06]). Meanwhile, administration of intranasal midazolam was associated with more satisfactory sedation level (61.76% vs 40.74%, RR = 1.53, with 95%CI [1.28, 1.83]), more rapid onset of sedation (SMD = -0.59, with 95%CI [-0.90, -0.28]) and more rapid recovery (SMD = -1.06, with 95%CI [-1.83, -0.28]). Current evidences also indicated that the differences of various adverse effects between two groups were not significant. CONCLUSIONS: Given that administration of midazolam via intranasal route provides more satisfactory sedative level with less fluctuation of hemodynamics parameters and more rapid onset and recovery, it might be considered as the preferred sedative premedication for pediatric patients compared to ketamine. However, the widespread evidences with low or moderate quality indicated that superiority of intranasal midazolam in pediatric sedation needs to be confirmed by more studies with high quality and large sample size in future. TRIAL REGISTRATION: The protocol of present study was registered with PROSPERO (CRD42022321348).

Compatibility and Stability of Ten Commonly Used Clinical Drugs in Pediatric Electrolyte Supplements Injection.

Objective: Pediatric electrolyte supplements injection is mainly used to supplement heat and body fluid, and commonly used in pediatrics. Its compatibility and stability with common clinical drugs such as antibiotics was rarely reported to ensure the children's safety and the rational use of drugs. The aim of the present study was to investigate physical and chemical stability of pediatric electrolyte supplements injection mixed with ten commonly used clinical drugs. Methods: According to clinical drug concentration, we mix the pediatric electrolyte supplements injection mixed with ten drugs. The compatible solutions were withdrawn at certain time intervals (0, 0.5, 1, 2, 4, 6 hours) after mixing and tested by description, insoluble particles detection, pH determination and high performance liquid chromatography (HPLC) assay of active ingredient as measures of physicochemical compatibility. Results: No obvious appearance changes were observed when mixing. Furthermore, over the 6 hours post-preparation period the pH values were within the requirements of each drug quality standard and the number of insoluble particles (≥10 and ≥25µm) met requirements of Chinese Pharmacopeia (Edition 2020) except for mezlocillin sodium for injection. The percentages of the initial concentrations maintained at a minimum of 97% in the mixtures within 6 hours. Conclusions: Nine commonly used clinical drugs remained stable in the pediatric electrolyte supplements injection for 6 hours at 25°C and avoiding from light. Mezlocillin sodium for injection was not recommended to be combined with electrolyte supplement injection for children because its insoluble particles exceed the standard.

Herpes simplex virus protein UL56 inhibits cGAS-Mediated DNA sensing to evade antiviral immunity.

After herpes simplex virus type 1 (HSV-1) infection, the cytosolic sensor cyclic GMP-AMP synthase (cGAS) recognizes DNA and catalyzes synthesis of the second messenger 2'3'-cGAMP. cGAMP binds to the ER-localized adaptor protein MITA (also known as STING) to activate downstream antiviral responses. Conversely, HSV-1-encoded proteins evade antiviral immune responses via a wide variety of delicate mechanisms, promoting viral replication and pathogenesis. Here, we identified HSV-1 envelop protein UL56 as a negative regulator of cGAS-mediated innate immune responses. Overexpression of UL56 inhibited double-stranded DNA-triggered antiviral responses, whereas UL56-deficiency increased HSV-1-triggered induction of downstream antiviral genes. UL56-deficiency inhibited HSV-1 replication in wild-type but not MITA-deficient cells. UL56-deficient HSV-1 showed reduced replication in the brain of infected mice and was less lethal to infected mice. Mechanistically, UL56 interacted with cGAS and inhibited its DNA binding and enzymatic activity. Furthermore, we found that UL56 homologous proteins from different herpesviruses had similar roles in antagonizing cGAS-mediated innate immune responses. Our findings suggest that UL56 is a component of HSV-1 evasion of host innate immune responses by antagonizing the DNA sensor cGAS, which contributes to our understanding of the comprehensive mechanisms of immune evasion by herpesviruses.

SARS-CoV-2 nucleocapsid protein impairs stress granule formation to promote viral replication.

The newly emerging coronavirus SARS-CoV-2 causes severe lung disease and substantial mortality. How the virus evades host defense for efficient replication is not fully understood. In this report, we found that the SARS-CoV-2 nucleocapsid protein (NP) impaired stress granule (SG) formation induced by viral RNA. SARS-CoV-2 NP associated with the protein kinase PKR after dsRNA stimulation. SARS-CoV-2 NP did not affect dsRNA-induced PKR oligomerization, but impaired dsRNA-induced PKR phosphorylation (a hallmark of its activation) as well as SG formation. SARS-CoV-2 NP also targeted the SG-nucleating protein G3BP1 and impaired G3BP1-mediated SG formation. Deficiency of PKR or G3BP1 impaired dsRNA-triggered SG formation and increased SARS-CoV-2 replication. The NP of SARS-CoV also targeted both PKR and G3BP1 to impair dsRNA-induced SG formation, whereas the NP of MERS-CoV targeted PKR, but not G3BP1 for the impairment. Our findings suggest that SARS-CoV-2 NP promotes viral replication by impairing formation of antiviral SGs, and reveal a conserved mechanism on evasion of host antiviral responses by highly pathogenic human betacoronaviruses.

SARS-CoV-2 membrane glycoprotein M antagonizes the MAVS-mediated innate antiviral response.

A novel SARS-related coronavirus (SARS-CoV-2) has recently emerged as a serious pathogen that causes high morbidity and substantial mortality. However, the mechanisms by which SARS-CoV-2 evades host immunity remain poorly understood. Here, we identified SARS-CoV-2 membrane glycoprotein M as a negative regulator of the innate immune response. We found that the M protein interacted with the central adaptor protein MAVS in the innate immune response pathways. This interaction impaired MAVS aggregation and its recruitment of downstream TRAF3, TBK1, and IRF3, leading to attenuation of the innate antiviral response. Our findings reveal a mechanism by which SARS-CoV-2 evades the innate immune response and suggest that the M protein of SARS-CoV-2 is a potential target for the development of SARS-CoV-2 interventions.

A comparative evaluation of dexmedetomidine and midazolam in pediatric sedation: A meta-analysis of randomized controlled trials with trial sequential analysis.

BACKGROUND: The present study with trial sequential analysis (TSA) was conducted to evaluate comprehensively the efficacy and safety of dexmedetomidine and midazolam in pediatric sedation, and to investigate whether the outcomes achieved the required information size to draw the conclusions. METHODS: PubMed, Embase, and Cochrane Library were searched from inception to October 2019. All randomized controlled trials used dexmedetomidine and midazolam in pediatric sedation were enrolled. Sedative efficacy, postoperative analgesic effect, and incidence of emergence agitation were considered as the co-primary outcomes. Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system was applied to rate the quality of evidences. RESULTS: We acquired data from 34 studies involving 2281 pediatric patients. The results indicated that administration of dexmedetomidine was associated with less incidence of emergence agitation (RR = 0.78, with 95% CI [0.65, 0.92]) and more satisfactory sedation at parental separation (RR = 0.31, with 95% CI [0.24, 0.41]) compared to midazolam, and the current sample sizes were sufficient with unnecessary further trials. Two groups did not differ significantly in sedation level at mask induction (RR = 0.86, with 95% CI [0.74, 1.00]). And using of dexmedetomidine was associated with less incidence of postoperative analgesic rescue (RR = 0.57, with 95% CI [0.35, 0.93]), but the number of patients was too few to achieve the required information size and to draw reliable conclusions. Premedication of dexmedetomidine was associated with significant less value of SBP, heart rate, increased incidence of bradycardia, and a lower rate of shivering. And there were no differences about onset of sedation and recovery time between two groups. CONCLUSIONS: Given that more satisfactory sedation at separation from parents and less incidence of emergence agitation, dexmedetomidine is preferred for pediatric sedation. However, compared with midazolam, the superiority of dexmedetomidine in providing adequate sedation at mask induction and postoperative analgesic effects has not yet been defined.

Human Cytomegalovirus Protein UL94 Targets MITA to Evade the Antiviral Immune Response.

Cyclic GMP-AMP synthase (cGAS) senses double-stranded DNA and synthesizes the second messenger cyclic GMP-AMP (cGAMP), which binds to mediator of IRF3 activation (MITA) and initiates MITA-mediated signaling, leading to induction of type I interferons (IFNs) and other antiviral effectors. Human cytomegalovirus (HCMV), a widespread and opportunistic pathogen, antagonizes the host antiviral immune response to establish latent infection. Here, we identified HCMV tegument protein UL94 as an inhibitor of the cGAS-MITA-mediated antiviral response. Ectopic expression of UL94 impaired cytosolic double-stranded DNA (dsDNA)- and DNA virus-triggered induction of type I IFNs and enhanced viral replication. Conversely, UL94 deficiency potentiated HCMV-induced transcription of type I IFNs and downstream antiviral effectors and impaired viral replication. UL94 interacted with MITA, disrupted the dimerization and translocation of MITA, and impaired the recruitment of TBK1 to the MITA signalsome. These results suggest that UL94 plays an important role in the immune evasion of HCMV.IMPORTANCE Human cytomegalovirus (HCMV), a large double-stranded DNA (dsDNA) virus, encodes more than 200 viral proteins. HCMV infection causes irreversible abnormalities of the central nervous system in newborns and severe syndromes in organ transplantation patients or AIDS patients. It has been demonstrated that HCMV has evolved multiple immune evasion strategies to establish latent infection. Previous studies pay more attention to the mechanism by which HCMV evades immune response in the early phase of infection. In this study, we identified UL94 as a negative regulator of the innate immune response, which functions in the late phase of HCMV infection.

Human cytomegalovirus protein UL42 antagonizes cGAS/MITA-mediated innate antiviral response.

Cyclic GMP-AMP synthase (cGAS) senses viral DNA in the cytosol and then catalyzes synthesis of the second messenger cGAMP, which activates the ER-localized adaptor protein Mediator of IRF3 Activator (MITA) to initiate innate antiviral response. Human cytomegalovirus (HCMV) proteins can antagonize host immune responses to promote latent infection. Here, we identified HCMV UL42 as a negative regulator of cGAS/MITA-dependent antiviral response. UL42-deficiency enhances HCMV-induced production of type I interferons (IFNs) and downstream antiviral genes. Consistently, wild-type HCMV replicates more efficiently than UL42-deficient HCMV. UL42 interacts with both cGAS and MITA. UL42 inhibits DNA binding, oligomerization and enzymatic activity of cGAS. UL42 also impairs translocation of MITA from the ER to perinuclear punctate structures, which is required for MITA activation, by facilitating p62/LC3B-mediated degradation of translocon-associated protein ß (TRAPß). These results suggest that UL42 can antagonize innate immune response to HCMV by targeting the core components of viral DNA-triggered signaling pathways.

Human Cytomegalovirus DNA Polymerase Subunit UL44 Antagonizes Antiviral Immune Responses by Suppressing IRF3- and NF-κB-Mediated Transcription.

Innate immunity is the first line of host defense against viral invasion. The induction of type I interferons (IFNs) and inflammatory cytokines is essential to host antiviral immune responses, which are also key targets of viral immune evasion. Human cytomegalovirus (HCMV) can establish long-term latent infections, in which immune evasion is a pivotal step. In this study, we identified HCMV protein UL44, a DNA polymerase processivity factor, as an inhibitor of the interferon regulatory factor 3 (IRF3)- and NF-κB-dependent antiviral response. Ectopic expression of UL44 inhibited HCMV-triggered induction of downstream effector genes and enhanced viral replication. Conversely, knockdown of UL44 potentiated HCMV-triggered induction of downstream antiviral genes. UL44 interacted with IRF3 and p65, and it inhibited the binding of IRF3 and NF-κB to the promoters of their downstream antiviral genes. These findings reveal an important mechanism of immune evasion by HCMV at the transcriptional level.IMPORTANCE Induction of type I IFNs and inflammatory cytokines plays pivotal roles in host antiviral innate immune responses. Viruses have evolved various mechanisms to interfere with these processes. HCMV causes severe ailments in immunodeficient populations and is a major cause of birth defects. It has been shown that HCMV antagonizes host innate immune defenses, which is important for establishing immune evasion and latent infection. In this study, we identified the HCMV DNA polymerase subunit UL44 as a suppressor of antiviral innate immune responses. Overexpression of UL44 impaired HCMV-triggered induction of type I IFNs and other antiviral genes and thus potentiated viral replication, whereas UL44 deficiency showed opposite effects. Mechanistic studies indicated that UL44 acts by inhibiting the binding of IRF3 and NF-κB to the promoters of downstream antiviral genes. These findings defined an important mechanism of HCMV immune evasion at the transcriptional level, which may provide a therapeutic target for the treatment of HCMV infection.

ZCCHC3 is a co-sensor of cGAS for dsDNA recognition in innate immune response.

Cyclic GMP-AMP synthase (cGAS) senses double-strand (ds) DNA in the cytosol and then catalyzes synthesis of the second messenger cGAMP, which activates the adaptor MITA/STING to initiate innate antiviral response. How cGAS activity is regulated remains enigmatic. Here, we identify ZCCHC3, a CCHC-type zinc-finger protein, as a positive regulator of cytosolic dsDNA- and DNA virus-triggered signaling. We show that ZCCHC3-deficiency inhibits dsDNA- and DNA virus-triggered induction of downstream effector genes, and that ZCCHC3-deficient mice are more susceptible to lethal herpes simplex virus type 1 or vaccinia virus infection. ZCCHC3 directly binds to dsDNA, enhances the binding of cGAS to dsDNA, and is important for cGAS activation following viral infection. Our results suggest that ZCCHC3 is a co-sensor for recognition of dsDNA by cGAS, which is important for efficient innate immune response to cytosolic dsDNA and DNA virus.

Human Cytomegalovirus Protein UL31 Inhibits DNA Sensing of cGAS to Mediate Immune Evasion.

The cytosolic DNA sensor cGAS recognizes viral DNA and synthesizes the second messenger cGAMP upon viral infection. cGAMP binds to the adaptor protein MITA/STING to activate downstream signaling events, leading to induction of type I interferons (IFNs) and antiviral effector genes. Here we identify the human cytomegalovirus (HCMV) protein UL31 as an inhibitor of cGAS. UL31 interacts directly with cGAS and disassociates DNA from cGAS, thus inhibiting cGAS enzymatic functions and reducing cGAMP production. UL31 overexpression markedly reduces antiviral responses stimulated by cytosolic DNA, while knockdown or knockout of UL31 heightens HCMV-triggered induction of type I IFNs and downstream antiviral genes. Moreover, wild-type HCMV replicates more efficiently than UL31-deficient HCMV, a phenotype that is reversed in cGAS null cells. These results highlight the importance of cGAS in the host response to HCMV as well as an important viral strategy to evade this innate immune sensor.

Efficacy of lidocaine on preventing incidence and severity of pain associated with propofol using in pediatric patients: A PRISMA-compliant meta-analysis of randomized controlled trials.

BACKGROUND: Propofol injection pain was considered as one conundrum during clinical anesthesia. The systematic review about the effect of lidocaine in reducing injection pain among children has not been established. The aim of the study was to systematically evaluate the efficacy and safety of such intervention. METHODS: The literature search was performed from the inception to the May 31, 2016 in PubMed, Ovid EMBASE, and Cochrane database. All randomized controlled trials that using lidocaine for propofol injection pain in children were enrolled. The primary outcome included the incidence of injection pain and the incidence of propofol injection pain in different degrees. The data were combined to calculate the relative ratio and relevant 95% confidence interval. A meta-analysis was performed following the guidelines of the Cochrane Reviewer's Handbook and the PRISMA statement. RESULTS: Data from the included 11 studies indicated that the incidence of injection pain was lower in lidocaine group than the incidence in saline control group and in propofol lipuro (medium- and long-chain triglycerides) group (pain occurrence: 22.1% in lidocaine vs 66.8% in saline, RR with 95% 0.34 [0.26, 0.43], I = 38%; 30.5% in lidocaine vs 46.9% in propofol lipuro, RR with 95% 0.68 [0.46, 1.00], I = 9%). There was no difference between lidocaine and ketamine/alfentanil both in reducing pain occurrence and in reducing pain severity (pain occurrence: 29.7% in lidocaine vs 25.8% in ketamine, RR with 95% 1.47 [0.16, 13.43], I = 94%; 31.0% in lidocaine vs 30.7% in alfentanil, RR with 95% 1.01 [0.69, 1.46], I = 11%). And the reported side effects revealed that the safety of lidocaine in pediatric patients was acceptable. CONCLUSION: Compared with ketamine and alfentanil, lidocaine would be served as one more effective treatment in consideration of its well-matched efficacy, acceptable accessibility, and reasonable safety. However, more high-quality evidences in pediatric patients are necessary.

Human Cytomegalovirus Tegument Protein UL82 Inhibits STING-Mediated Signaling to Evade Antiviral Immunity.

Recognition of human cytomegalovirus (HCMV) DNA by the cytosolic sensor cGAS initiates STING-dependent innate antiviral responses. HCMV can antagonize host immune responses to promote latency infection. However, it is unknown whether and how HCMV targets the cGAS-STING axis for immune evasion. Here we identified the HCMV tegument protein UL82 as a negative regulator of STING-dependent antiviral responses. UL82 interacted with STING and impaired STING-mediated signaling via two mechanisms. UL82 inhibited the translocation of STING from the ER to perinuclear microsomes by disrupting the STING-iRhom2-TRAPß translocation complex. UL82 also impaired the recruitment of TBK1 and IRF3 to the STING complex. The levels of downstream antiviral genes induced by UL82-deficient HCMV were higher than those induced by wild-type HCMV. Conversely, wild-type HCMV replicated more efficiently than the UL82-deficient mutant. These findings reveal an important mechanism of immune evasion by HCMV.

Knocking down SMC1A inhibits growth and leads to G2/M arrest in human glioma cells.

Cohesin, a multiunit complex of SMC1A, SMC3 and Rad21, associates with chromatin after mitosis and holds sister chromatids together following DNA replication. It has been reported that SMC1A is mutated in some cancer types, leading to genomic instability and abnormal cell growth. In this study, we investigated the role of SMC1A in human glioma. We found that SMC1A was expressed at abnormally high levels in human glioma tissue and in cultured U251 glioma cells. Knocking down SMC1A expression in U251 cells with SMC1A-targeted interfering RNAs inhibited cell growth and induced G2/M cell cycle arrest. Furthermore, expression of the cell cycle associated gene CCNB1IP1 was dramatically increased, whereas expression of Cyclin B1 was decreased in SMC1A-deficienct U251 cells. These results suggest that SMC1A upregulation is involved in the pathogenesis of glioma.

Protective immune responses in ducklings induced by a suicidal DNA vaccine of the VP1 gene of duck hepatitis virus type 1.

A suicidal DNA vaccine based on a Semliki Forest virus (SFV) replicon was evaluated for the development of a vaccine against duck hepatitis virus type 1 (DHV-1). The VP1 gene of DHV-1 was cloned and inserted into pSCA1, an SFV DNA-based replicon vector. The resultant plasmid, pSCA/VP1, was transfected into BHK-21 cells and the antigenicity of the expressed protein was confirmed using an indirect immunofluorescence and western blot assay. Immunogenicity was studied in ducklings. Ducklings were injected intramuscularly two times with pSCA/VP1 at 14 days intervals. Anti-DHV-1 antibodies were detected by ELISA, the lymphocyte proliferation response was also tested by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide method and neutralizing antibodies were measured by microneutralization tests. Our results showed that DHV-1-specific antibodies, neutralizing antibodies and lymphocyte proliferation were well induced in ducklings. Furthermore, all the ducklings were protected against challenge with wild DHV-1. In conclusion, we demonstrate that the suicidal DNA vaccine is a promising vaccine candidate facilitating the prevention of duck hepatitis caused by DHV-1.

Establishment of a duck cell line susceptible to duck hepatitis virus type 1.

Until recently, there was no cell line that could produce continuously high-titer duck hepatitis virus type 1 (DHV-1). In this study, a duck embryo fibroblast (DEF) cell line was established, and the susceptibility of this cell line to DHV-1 was determined. The primary culture of DEF cells was from a duck embryo that was partially digested with trypsin. Digested tissue pieces were cultured at 37°C in Dulbecco's Modified Eagle Medium supplemented with 10% fetal bovine serum. The cultured DEF cells, which had the morphology of fibroblast, proliferated to 100% confluence four days later. An immortalized DEF cell line, named DEF-TA, was established and subcultured to passage 33, and the susceptibility of that cell line to DHV-1 was determined. In the DHV-1 susceptibility tests, cytopathic effects and the propagation of virus were observed in DEF-TA cells after DHV-1 infection. This continuous DHV-1-susceptible DEF cell line may serve as a valuable cell line for studies of cell-virus interactions and the pathogenesis of DHV-1 and may be useful for the development of an inactivated vaccine.