Asymptomatic norovirus infection during outbreaks in China: A systematic review and meta-analysis.

Acute gastroenteritis outbreaks may be caused by the excretion of norovirus (NoV) from asymptomatic individuals. Despite numerous studies involving asymptomatic NoV infection during outbreaks in China, a comprehensive assessment of its role has not been conducted, which is critical for emergency management. Our objective was to assess the prevalence of asymptomatic NoV infection during outbreaks in China. We conducted a comprehensive search of multiple databases, including PubMed, Web of Science, Cochrane Library, China National Knowledge Infrastructure, China Wanfang, and China Weipu, between January 1, 1997 and June 19, 2023. The retrieved articles and their references underwent screening, which utilized polymerase chain reaction-based assays for the detection of NoV in asymptomatic individuals during outbreaks that occurred in China. The primary summary data were the prevalence of asymptomatic NoV infection in outbreaks. We generated pooled estimates of asymptomatic prevalence in the population as a whole and in subgroups by using random-effect models. Of the 97 articles included, the pooled asymptomatic prevalence of NoV among 5117 individuals in outbreaks was 17.6% (95% confidence interval [CI]: 14.1-21.3). The asymptomatic prevalence of NoV GII (17.1%, 95% CI: 12.9-21.5) was similar to that of NoV GI (22.0%, 95% CI: 12.8-32.4). However, the proportion of asymptomatic individuals involved in NoV GII (57.44%) was significantly higher than that of NoV GI (5.12%), and NoV GII (75.26%) was reported much more frequently than NoV GI (14.43%) in the included articles. Meta-regression analysis of 11 possible influencing factors (geographic region, setting, season, sample type, genotype, transmission route, occupation, age, per capita income, study quality, and cases definition) showed that the source of heterogeneity might be related to the outbreak settings, per capita income, and study quality (p = 0.037, 0.058, and 0.026, respectively). Of particular note was the asymptomatic prevalence peaked in preschoolers (27.8%), afterward, it fell into trough in elementary and junior school children (10.5%), before the second peak located in adults (17.8%), and the elderly (25.2%). Prevalent genotypes reported include GII.4, followed by GII.17, GII.2, GII.3, GII.6, and so forth. The estimated asymptomatic prevalence of NoV during outbreaks in China was as high as 17.6%, with NoV GII dominating. In addition, genetic subtypes of NoV in outbreaks should be detected whenever possible. The role of asymptomatic individuals in NoV outbreaks cannot be ignored. This knowledge will help governments develop public health policies and emergency response strategies for outbreaks, assess the burden, and develop vaccines.

Molecular and epidemiological characterization of Staphylococcus aureus causing bovine mastitis in China.

BACKGROUND: Staphylococcus aureus is one of the most prevalent pathogens in bovine mastitis, which leads to substantial financial losses for the dairy industry. RESULTS: In this study, S. aureus (n = 72) was isolated from 18 dairy farms in 15 provinces across China in 2021. The identification of these isolates at the species level was achieved by employing 16S rRNA sequencing. An isothermal amplification method for auxiliary detection of S. aureus was established, which can be employed not only for laboratory detection but also for point-of-care testing (POCT). Molecular characteristics of S. aureus mastitis in Chinese dairy cows were determined through MLST and spa typing. Finally, methicillin-resistant Staphylococcus aureus (MRSA) and MRSA resistance genes were detected using MIC and PCR amplification techniques. 72 isolates were identified as 12 sequence types (STs) and 7 clonal complexes (CC). ST1/CC1 was the dominant prevalent accounting for 33.3 % of the total, and exhibiting a wide distribution range. In terms of spa types, t114 was the dominant type, accounting for 31.9 % of the total, followed by t529 as the second major type. Four S. aureus strains were classified as MRSA according to their levels of oxacillin resistance (MIC ≥4 µg/mL). Among these four MRSA strains, one of them was found to be mecA positive. However, the presence of drug-resistance genes mecA and mecC was not detected in the remaining three MRSA strains, indicating the possible existence of new resistance genes. CONCLUSIONS: Our study investigated the prevalence of S. aureus mastitis in dairy cows in China, while also examined the molecular characteristics and MRSA strains. This information will help with the clinical monitoring, prevention, and control of S. aureus mastitis in dairy cattle.

pH-responsive resveratrol-loaded ZIF-8 nanoparticles modified with tannic acid for promoting colon cancer cell apoptosis.

Resveratrol (Res) is known for its potential in treating various types of cancers, with a particular advantage of causing minimal toxic side effects. However, its clinical application is constrained by challenges such as poor bioavailability, low water solubility, and chemical instability in neutral and alkaline environments. In light of these limitations, we have developed a pH-responsive drug delivery nanoplatform, Res@ZIF-8/TA NPs, which exhibits good biocompatibility and shows promise for in vitro cancer therapy. Benefiting from the mild reaction conditions provided by zeolitic imidazolate frameworks (ZIFs), a "one-pot method" was used for drug synthesis and loading, resulting in a satisfactory loading capacity. Notably, Res@ZIF-8/TA NPs respond to acidic environments, leading to an improved drug release profile with a controlled release effect. Our cell-based experiments indicated that tannic acid (TA) modification enhances the biocompatibility of ZIFs. 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di- phenytetrazoliumromide (MTT assay), Hoechst 33342/PI staining, cell scratch assay, Transwell and Reverse Transcription quantitative PCR (RT-qPCR) assays further demonstrated that Res@ZIF-8/TA NPs inhibited colon cancer cell migration and invasion, and promoted apoptosis of colon cancer cells, suggesting a therapeutic potential and demonstrating anti-cancer properties. In conclusion, the Res@ZIF-8/TA NPs pH-responsive drug delivery systems we developed may offer a promising avenue for cancer therapy. By addressing some of the challenges associated with Res-based treatments, this system could contribute to advancements in cancer therapeutics.

Circular replication-associated protein-encoding single-stranded DNA virus with risk of spillover is widely prevalent in domestic animals in China.

Circular replication-associated protein (Rep)-encoding single-stranded (CRESS) DNA viruses are highly diverse and have a broad range of hosts. In this study, we report the detection of Bo-Circo-like virus AH20-1 in the feces of diarrheal cattle. The virus has a circular genome of 3,912 nucleotides, three major putative open reading frames, and encodes a Rep gene of 310 amino acids. We found that the virus is closely related to the Bo-Circo-like virus CH strain, which belongs to the novel Kirkoviridae family. Furthermore, we conducted a nationwide surveillance program and found that the virus is prevalent in China (23.6%, 205/868), with the BCLa subtype being the predominant strain. Our findings suggest that the virus can infect sheep, highlighting the potential for cross-species transmission. Our pressure analysis indicates that the CRESS-DNA Kirkoviridae family has broad host adaptation, and that selection pressure played an important role in the evolution of its Rep genes. Our study underscores the need for continued epidemiological surveillance of this virus due to its widespread prevalence in our ruminant population and potential for cross-species transmission.

Integrating filter paper extraction, isothermal amplification, and lateral flow dipstick methods to detect Streptococcus agalactiae in milk within 15 min.

Introduction: Mastitis is one of the most serious diseases affecting dairy farming, causing huge economic losses worldwide. Streptococcus agalactiae is the main pathogenic bacterium of contagious mastitis and can deliver a devastating blow to a farm's economy. Rapid detection is the key to disease control. Methods: In this study, a rapid detection method for S. agalactiae was established. This method combines filter paper extraction, multienzyme isothermal rapid amplification (MIRA), and lateral flow dipsticks (LFD). To simplify the extraction procedure, we designed a disposable extraction device (DED). First, DED performance was evaluated by polymerase chain reaction (PCR) and then the lysis formula and extraction time were optimized. Second, this study compared the extraction performance of a filter paper and an automatic nucleic acid extraction instrument. After screening primers, MIRA for S. agalactiae was established and combined with LFD. Specificity and sensitivity were evaluated after optimizing the reaction conditions. Results: The results showed that the lowest extraction line for DED was 0.01-0.001 ng/µl. In the specificity study, 12 different bacteria were tested, and only S. agalactiae was found to be positive. In the sensitivity study, seven dilution gradients were established, and the lowest detection line was 3.52 × 102 CFU/ml. Discussion: In summary, the method established in this study does not require laboratory equipment and is suitable for on-site detection. The entire method takes only 15 min, is low in cost, has high precision and low technical requirements for operators, which is in contrast with the high cost and cumbersome operation of traditional methods, and is suitable for on-site testing in areas with limited facilities.

Development of rapid serotype-specific PCR assays for eight serotypes of Streptococcus suis.

Streptococcus suis is an emerging zoonotic pathogen causing severe infections in pigs and humans. Thirty-three serotypes of S. suis have been identified using serum agglutination. The capsular polysaccharides synthesis (cps) locus is usually conserved among different strains of the same serotype. The cps loci of 15 serotypes have been sequenced, while the loci of the other serotypes remain unknown. In the present study, two to six serotype-specific genes of each of eight serotypes, i.e., serotypes 3, 4, 5, 8, 10, 19, 23, and 25, were identified using cross-hybridization with 93 nucleic acid probes specific to genes in the cps locus, and serotype-specific PCR assays for rapid and sensitive detection of the eight serotypes were then developed. The PCR typing results of the 148 serologically typeable isolates were completely consistent with agglutination results. Furthermore, some autoagglutinating, acapsular, and multiagglutinating strains which could not be differentiated by traditional serum agglutination assays were positive in the PCR assays. Use of the PCR assays with clinical tonsillar specimens showed that the assays are sensitive and able to identify samples with autoagglutinating isolates. To our knowledge, this is the first study to identify the serotype-specific genes of the eight Streptococcus suis serotypes and develop rapid and sensitive PCR assays for the eight serotypes which can be identified only by serum agglutination.

Study of Nursing Models by Machine Learning in Children with Congenital Esophageal Atresia.

This research paper elucidates the clinical effect of an integrated nursing model of medical care and patient in the diagnosis and treatment of congenital esophageal atresia (CEA). For this purpose, a total of 120 children with CEA were selected as study subjects who were admitted to our hospital (January 2017 to April 2020). They were randomly divided into the control group and observation group. Each group had 60 cases. The control group was given routine nursing, while the observation group adopted the integrated nursing model of medical care. The integrated nursing model had the characteristics of recognizing and managing the CEA quickly and efficiently. Thus, it can help increase the survival rate of infants. This model works along with the parents to provide specialized services to the child. They were tasked to carefully observe the infants as well as calm the parents. They were also given the additional task of keeping track of patients who were currently admitted in the hospital and those who were already discharged. The tracking and communication were done with the help of a communication platform which is WeChat. The rehospitalization rate, 1-hour visit rate, accuracy rate of children with suspected postoperative complications, psychological status of children's parents, medical compliance, and satisfaction were compared between the two groups. The rehospitalization rate in the observation group was lower than that in the control group (P < 0.05). The 1-hour visit rate and accuracy of children with suspected postoperative complications in the observation group were higher than those in the control group (P < 0.05). The anxiety and depression scores of the parents in the observation group were lower than those in the control group (P < 0.05). The compliance and satisfaction of parents in the observation group were higher than those in the control group (P < 0.05). The clinical effect of the integrated nursing model of medical care and patient in CEA was highly satisfactory. It reduces the rehospitalization rate and enables timely diagnosis and treatment of suspicious complications effectively. It also improved parents' negative psychological emotions, compliance, and satisfaction.

Microbial hydrogen economy alleviates colitis by reprogramming colonocyte metabolism and reinforcing intestinal barrier.

With the rapid development and high therapeutic efficiency and biosafety of gas-involving theranostics, hydrogen medicine has been particularly outstanding because hydrogen gas (H2), a microbial-derived gas, has potent anti-oxidative, anti-apoptotic, and anti-inflammatory activities in many disease models. Studies have suggested that H2-enriched saline/water alleviates colitis in murine models; however, the underlying mechanism remains poorly understood. Despite evidence demonstrating the importance of the microbial hydrogen economy, which reflects the balance between H2-producing (hydrogenogenic) and H2-utilizing (hydrogenotrophic) microbes in maintaining colonic mucosal ecosystems, minimal efforts have been exerted to manipulate relevant H2-microbe interactions for colonic health. Consistent with previous studies, we found that administration of hydrogen-rich saline (HS) ameliorated dextran sulfate sodium-induced acute colitis in a mouse model. Furthermore, we demonstrated that HS administration can increase the abundance of intestinal-specific short-chain fatty acid (SCFA)-producing bacteria and SCFA production, thereby activating the intracellular butyrate sensor peroxisome proliferator-activated receptor γ signaling and decreasing the epithelial expression of Nos2, consequently promoting the recovery of the colonic anaerobic environment. Our results also indicated that HS administration ameliorated disrupted intestinal barrier functions by modulating specific mucosa-associated mucolytic bacteria, leading to substantial inhibition of opportunistic pathogenic Escherichia coli expansion as well as a significant increase in the expression of interepithelial tight junction proteins and a decrease in intestinal barrier permeability in mice with colitis. Exogenous H2 reprograms colonocyte metabolism by regulating the H2-gut microbiota-SCFAs axis and strengthens the intestinal barrier by modulating specific mucosa-associated mucolytic bacteria, wherein improved microbial hydrogen economy alleviates colitis.

A closed-form method for calculating the angular distribution of multiply scattered photons through isotropic turbid slabs.

This paper develops a method for calculating the angular distribution (AD) of multiply scattered photons through isotropic turbid slabs. Extension to anisotropic scattering is also discussed. Previous studies have recognized that the AD of multiply scattered photons is critical for many applications, such as the design of imaging optics and estimation of image quality. This paper therefore develops a closed-from method that can accurately calculate the AD over a wide range of conditions. Other virtues of the method include its simplicity in implementation and its prospective for extension to anisotropic scattering.

Study on the anti-tumor mechanism related to immune microenvironment of Bombyx Batryticatus on viral and non-viral infections of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a malignant primary liver cancer with poor prognosis. Most previous studies on anti-HCC effects of traditional Chinese medicines (TCM) have focused on the mechanism of direct action and few researchers considered that TCM can inhibit tumor progression and improve prognosis of HCC patients through regulating tumor microenvironment (TME). In this study, network pharmacology combined bioinformatics methods were employed to analysis mechanism of Bombyx batryticatus (B. batryticatus, one of the most frequently used traditional Chinese animal medicines, has been used in some Asian countries for centuries as an anticancer agent, anti-inflammatory agent, and antioxidant.) in regulating TME of HCC. The results showed that 24 core targets and 2 compounds were identified from overlapping between differential expression genes related to HCC in the cancer genome atlas (TCGA) database and targets of B. batryticatus in TCMSP database. For further analyzing the role of TME heterogeneity of HCC on anti-HCC mechanism of B. batryticatus, the correlation of core targets related with overall survival of HCC with TME cells in hepatitis C or hepatitis B virus-associated hepatocellular carcinoma (VIR) and non-hepatitis C or hepatitis B virus-associated hepatocellular carcinoma (NVIR) were calculated, respectively. The results showed that AKR1C3, SPP1 were significantly related with macrophages in VIR and other targets including NR1I2, CYP1A2 and CYP3A4 were significantly associated with macrophages in NVIR; the target protein AKR1C3 was significantly negative correlated with macrophages M1 in VIR (cor=-0.35, P-value<0.001) and the correlation between AKR1C3 and macrophages M1 was poor in NVIR group (cor = 0.064, P-value = 0.36). Additionally, survival curve of AKR1C3 showed that poor prognosis in VIR group can be related to high level of AKR1C3 (HR = 2.32, 95 % CI: 1.18-4.56, P-value = 0.012), and no signified gene can be found in NVIR group (P-value>0.05). In conclusion, the molecular mechanism of anti-HCC of B. batryticatus can be related to the tumor microenvironment to some extent. B. batryticatus may exert its anti-cancer effects and improve prognosis of patients by regulating macrophages M1 in VIR and NVIR through acting on different targets.

An ELISA based on soluble egg antigens for the serodiagnosis of animal schistosomiasis turkestanica.

BACKGROUND: The existing diagnostic techniques for detecting schistosomiasis turkestanica, such as aetiological assays, identify infection by parasitic worms via the incubation of miracidia from faeces or observing eggs under microscopy. However, they are limited in the diagnosis of low-grade and prepatent infections, which lead to a high misdetection rates. Therefore, a new method for parasite diagnosis with increased sensitivity is urgently needed. METHODS: Goats in Nimu County (Tibet, China) infected with Schistosoma turkestanicum in an epidemic area were selected according positivity for the infection by faecal examination. Adult worms were collected, eggs were extracted by the sodium hydroxide (NaOH) erosion method, and soluble worm antigen preparation (SWAP) and soluble egg antigen (SEA) were isolated. The best coating concentration of the antigens and the best degree of dilution for serum were determined by square array experiments, and the optimal blocking solution and serum diluents were selected. The specificity, sensitivity and crossover of the ELISA method were determined using 48 samples of goat sera positive for S. turkestanicum, 100 samples of goat sera negative for S. turkestanicum, and 54 samples of buffalo sera positive for S. japonicum. Serological assays were established with samples from goats naturally grazed in a rural area of Nimu County, Tibet Province, by using the indirect ELISA method for the diagnosis of schistosomiasis, and faeces were collected for miracidia hatching. The sensitivity of the two detection methods was compared. RESULTS: Eggs of S. turkestanicum were distributed in the host duodenum and small intestine. Eggs in the host intestinal wall were extracted by the NaOH erosion method, which provided intact eggs with reduced impurities. The testing results obtained by isolating SEA were more stable than those obtained by using SWAP and less affected by the coating concentration and serum dilution. Additionally, the value of positive serum/negative (P/N) serum for SEA was much higher than that for SWAP. The optimal coating concentration of SEA was 0.5 µg/ml, and the optimal serum dilution was 1:100. The specificity and sensitivity of the indirect ELISA based on SEA (S. turkestanicum) were both 100%, and no cross-reactivity was found with schistosomiasis japonica. An epidemiological survey of goats in naturally infected areas showed that the prevalence rate of schistosomiasis turkestanica was 93%, and the infection rate increased with the ages of the goats. CONCLUSION: We aimed to develop a sensitive method to utilize in the mass field screening of livestock. As a diagnostic antigen, SEA (S. turkestanicum) was more suitable for serological testing than SWAP (S. turkestanicum). The indirect ELISA using SEA (S. turkestanicum) exhibited good sensitivity, specificity and no cross-reactivity with schistosomiasis japonica. The degree of infectivity and prevalence of S. turkestanicum infection in endemic areas are serious and should be a focus of concern among local departments.

Integrative data mining and meta-analysis to investigate the prognostic role of microRNA-200 family in various human malignant neoplasms: A consideration on heterogeneity.

BACKGROUND: Existing meta-analysis have shown that the miR-200 family can be taken as a prognostic biomarker for many tumors. However, great heterogeneity was shown in predicting overall survival (OS) and progression-free survival (PFS). Emerging studies indicate that the expression levels of members of the miR-200 family are tissue-specific among various tumor tissues, which may be the main reason of the heterogeneity in predicting survival prognosis of tumor patients with the miR-200 family as biomarkers. By further analysis of heterogeneity of the miR-200 family as a biomarker for predicting survival prognosis of patients with different tumors, we expected to provide an accurate basis for the clinical application of the miR-200 family to predict the prognosis of patients with different tumors. METHODS: Eligible published studies were identified by searching the databases of PubMed, Embase and Web of Science. The clinical data of patients in the studies were pooled, and pooled hazard ratios (HR) with 95% confidence intervals (95% CI) were used to calculate the strength of this association. The expressions of miRNAs were extracted from The Cancer Genome Atlas (TCGA). We presented the expressions of each member in miR-200 family in 15 types of cancer by boxplot, and analyzed the correlation among the members of miR-200 family by Spearman method. Different subgroup analyses were then performed based on the correlation among the members of miR-200 family, and the publication bias was assessed using the funnel plot of the Egger bias indicator test. RESULTS: Of 36 articles, including 15 tumor types and 4644 patients were included to perform meta-analysis. It was found that miR-200 family members can be used as independent protective factors in patients with various tumors but the miR-200 family has a higher heterogeneity in predicting prognosis: OS (HR = 0.82, 95% CI: 0.66-1.03, I2 = 85%, P < 0.01) and PFS (HR = 0.81, 95% CI: 0.57-1.16, I2 = 97%, P < 0.01). The data from TCGA database were used to analyze the expression levels of the miR-200 family and the results showed that the expression of miR-429 in different cancers is very different, and there are significant differences in expression levels compared with other miR-200 family members; the expression levels of miR-200a and miR-200b in various tumor tissues were similar to each other, respectively; miR-200c and miR-141 showed similar expression levels in each of most types of cancer tissues except ovarian cancer (OC). The expression levels of members of the miR-200 family in breast cancer (BRCA), cervical cancer (CESC), colon cancer (COAD), esophageal cancer (ESCA), head and neck cancer (HNSC), lung adenocarcinoma (LUAD) and squamous cell carcinoma (LUSC) are relatively stable, but great variations can be found in the expression levels of miR-200 family members in ovarian cancer (OC), liver cancer (LIHC), renal clear cell carcinoma (KIRC) and renal papillary cell carcinoma (KIRP). Cluster analysis of expression of target genes of miR-200 family in different cancers yielded similar results to the expression level of the miR-200 family. Subgroup analysis of OC, LIHC, GC and LUAD based on expression levels and clustering results reduced or even eliminated the heterogeneity of miR-200 family members in predicting patient outcomes. CONCLUSIONS: Our results convincingly demonstrated that the miR-200 family could serve as a prognostic biomarker for cancers mentioned above and has potential value in clinical practice. MiR-200 family as prognostic biomarkers needs to be performed according to different tumor tissues and correlation between members in miR-200 family.

Heme oxygnease-1 induction by methylene blue protects RAW264.7 cells from hydrogen peroxide-induced injury.

Although methylene blue (MB) has showed strong antioxidant effect, its effect related with heme oxygenase-1 (HO-1) is still unclear. Thus, we investigated the effects of MB on HO-1 protein content and enzyme activity, and its protective effect against hydrogen peroxide (H2O2)-induced oxidative damage in RAW264.7 macrophage. The cell viability and the release of lactate dehydrogenase of RAW264.7 were determined. The mitochondrial functions were valuated through these indexes: content of adenosine triphosphate, superoxide dismutase, concentration of reactive oxygen species and mitochondrial membrane potential. Meanwhile, high content screening tested generation of ROS, MMP and intracellular concentration of calcium ion. qRT-PCR valuated macrophage phenotype markers expression. Lastly, flow cytometry and caspase-3 detection analyzed RAW264.7 apoptosis. Our data showed that (1) Both pretreatment and posttreatment of MB increased HO-1 protein content and enzyme activity; (2) MB rescued cells from H2O2-induced mitochondrial dysfunction; (3) High content screening revealed that MB alleviated the changes including generation of reactive oxygen species, mitochondrial membrane potential and intracellular concentration of calcium ion in H2O2 exposed RAW264.7; (4) MB attenuated H2O2-induced apoptosis; (5) MB pretreatment decreased the expression of M1 macrophage markers (Tnf and Nos2) while increasing the expression of M2 macrophage markers (Mrc1 and Il10); (6) The beneficial effect of MB was abolished by zinc protoporphyrin IX (HO-1 activity inhibitor) or HO-1 siRNA. In summary, MB protects RAW264.7 cells from H2O2-induced injury through up-regulation HO-1.

Cloning of equine herpesvirus type 1 438/77 strain genome as a bacterial artificial chromosome.

Equine herpesvirus type 1 (EHV-1) is a major cause of respiratory and reproductive diseases in horses worldwide. The genome of EHV-1 strain 438/77 (isolated from an aborted equine fetus) was cloned as a bacterial artificial chromosome (BAC) in E. coli without any gene deletions. The mini-F plasmid sequence was inserted in the middle of ORF19 and 20 via homologous recombination following co-transfection of viral DNA and plasmid pE19_20/HA into RK13 cells. Circular viral DNA was extracted from RK13 cells infected with purified recombinant virus expressing green fluorescent protein (GFP) and electrophorated into E. coli DH10B cells. The clone harboring the BAC was screened and analyzed by PCR and RFLP. Reconstitution of the recombinant virus was achieved successfully by transfection of the BAC DNA into RK13 cells. The mini-F sequence in the reconstituted virus was subsequently removed by homologous recombination between virus DNA and plasmid pE1920XM, inducing a point mutation in the Xbal site in ORF19. Comparison of RFLP profiles of the rescued, recovered and the wild-type viral genome demonstrated that no unexpected changes occurred during mutagenesis. In vitro replication assays showed that BAC-reconstituted virus mutant growth kinetics and plaque formation morphology/size were indistinguishable to those measured for wild-type virus.

[Construction of an infectious clone of pseudorabies virus strain ZJ genome maintained as a bacterial artificial chromosome].

pHA2 plasmid sequence,with Bacterial Artificial Chromosome(BAC) vector and the GFP expression cassette, was introduced into the UL23(TK) gene of Pseudorabies virus(PRV)strain ZJ by homologous recombination,and the recombinant PRV (rPRV-HA2) was confirmed and isolated by plaque purification. The circular genome of rPRV-HA2 was electroporated into Escherichia coli strain DH10B and then the PRV BAC (pPRV) was recovered. The transfection of pPRV into VeroE6 cells resulted in productive infection. The rescued virus isolated following transfection was indistinguishable from rPRV-HA2 in cytopathic effects (CPE) and replication curve in vitro. The growth kinetics of the viruses indicated that partial deletion of TK gene and BAC vector insertion had no effect on the viral titre and plaque size in vitro. The PRV BAC system will enable quick and reliable manipulation of the viral genome for the functional investigation on the PRV genes and the development of PRV vector in vaccine.