Development Of Cytopathic Effect Research Articles

Development of an immunofluorescence assay for detection of SARS-CoV-2.

SARS-CoV-2, the etiologic agent of the COVID-19 pandemic, emerged as the cause of a global crisis in 2019. Currently, the main method for identification of SARS-CoV-2 is a reverse transcription (RT)-PCR assay designed to detect viral RNA in oropharyngeal (OP) or nasopharyngeal (NP) samples. While the PCR assay is considered highly specific and sensitive, this method cannot determine the infectivity of the sample, which may assist in evaluation of virus transmissibility from patients and breaking transmission chains. Thus, cell-culture-based approaches such as cytopathic effect (CPE) assays are routinely employed for the identification of infectious viruses in NP/OP samples. Despite their high sensitivity, CPE assays take several days and require additional diagnostic tests in order to verify the identity of the pathogen. We have therefore developed a rapid immunofluorescence assay (IFA) for the specific detection of SARS-CoV-2 in NP/OP samples following cell culture infection. Initially, IFA was carried out on Vero E6 cultures infected with SARS-CoV-2 at defined concentrations, and infection was monitored at different time points. This test was able to yield positive signals in cultures infected with 10 pfu/ml at 12 hours postinfection (PI). Increasing the incubation time to 24 hours reduced the detectable infective dose to 1 pfu/ml. These IFA signals occur before the development of CPE. When compared to the CPE test, IFA has the advantages of specificity, rapid detection, and sensitivity, as demonstrated in this work.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00705-022-05392-z.

Isolation and characterization of severe acute respiratory syndrome coronavirus 2 in Turkey

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and associated with severe respiratory illness emerged in Wuhan, China, in late 2019. The virus has been able to spread promptly across all continents in the world. The current pandemic has posed a great threat to public health concern and safety. Currently, there are no specific treatments or licensed vaccines available for COVID-19. We isolated SARS-CoV-2 from the nasopharyngeal sample of a patient in Turkey with confirmed COVID-19. We determined that the Vero E6 and MA-104 cell lines are suitable for supporting SARS-CoV-2 that supports viral replication, development of cytopathic effect (CPE) and subsequent cell death. Phylogenetic analyses of the whole genome sequences showed that the hCoV-19/Turkey/ERAGEM-001/2020 strain clustered with the strains primarily from Australia, Canada, England, Iran and Kuwait and that the cases in the nearby clusters were reported to have travel history to Iran and to share the common unique nucleotide substitutions.

Fetal Calf Serum Exerts an Inhibitory Effect on Replication of Duck Hepatitis A Virus Genotype 1 in Duck Embryo Fibroblast Cells.

Among the causative agents of duck viral hepatitis, duck hepatitis A virus genotype 1 (DHAV-1) is the most common virus reported in most outbreaks worldwide. How to propagate DHAV-1 in cell cultures efficiently remains a problem to be explored. Here, we aimed to test the effect of serum type on DHAV-1 replication in duck embryo fibroblast (DEF) cells. Comparative studies involved virus culture and passage, observation of cytopathic effect (CPE), virus quantification, and plaque formation assay. From the results of these investigations, we conclude that use of chicken serum (CS) in maintenance medium allows DHAV-1 to establish productive, cytocidal infection in DEF cells, whereas FCS exerts inhibitory effects on DHAV-1 replication, CPE development, and plaque formation. By using a neutralization test, we found that the direct action of FCS on virions is likely to play a key role in inhibiting DHAV-1 replication in DEF cells. Mechanism analyses revealed that FCS inhibits DHAV-1 replication at virus adsorption and reduces extracellular virus yields. The present work may shed light on a new perspective for antiviral agent development, and have provided a virus–host cell system for further studies on molecular mechanism involved DHAV-1 replication and pathogenesis.

Novel Mutations in nsP2 Abolish Chikungunya Virus-Induced Transcriptional Shutoff and Make the Virus Less Cytopathic without Affecting Its Replication Rates.

Alphavirus infections are characterized by global inhibition of cellular transcription and rapid induction of a cytopathic effect (CPE) in cells of vertebrate origin. Transcriptional shutoff impedes the cellular response to alphavirus replication and prevents establishment of an antiviral state. Chikungunya virus (CHIKV) is a highly pathogenic alphavirus representative, and its nonstructural protein 2 (nsP2) plays critical roles in both inhibition of transcription and CPE development. Previously, we have identified a small peptide in Sindbis virus (SINV) nsP2 (VLoop) that determined the protein's transcriptional inhibition function. It is located in the surface-exposed loop of the carboxy-terminal domain of nsP2 and exhibits high variability between members of different alphavirus serocomplexes. In this study, we found that SINV-specific mutations could not be directly applied to CHIKV. However, by using a new selection approach, we identified a variety of new VLoop variants that made CHIKV and its replicons incapable of inhibiting cellular transcription and dramatically less cytopathic. Importantly, the mutations had no negative effect on RNA and viral replication rates. In contrast to parental CHIKV, the developed VLoop mutants were unable to block induction of type I interferon. Consequently, they were cleared from interferon (IFN)-competent cells without CPE development. Alternatively, in murine cells that have defects in type I IFN production or signaling, the VLoop mutants established persistent, noncytopathic replication. The mutations in nsP2 VLoop may be used for development of new vaccine candidates against alphavirus infections and vectors for expression of heterologous proteins.IMPORTANCE Chikungunya virus is an important human pathogen which now circulates in both the Old and New Worlds. As in the case of other Old World alphaviruses, CHIKV nsP2 not only has enzymatic functions in viral RNA replication but also is a critical inhibitor of the antiviral response and one of the determinants of CHIKV pathogenesis. In this study, we have applied a new strategy to select a variety of CHIKV nsP2 mutants that no longer exhibited transcription-inhibitory functions. The designed CHIKV variants became potent type I interferon inducers and acquired a less cytopathic phenotype. Importantly, they demonstrated the same replication rates as the parental CHIKV. Mutations in the same identified peptide of nsP2 proteins derived from other Old World alphaviruses also abolished their nuclear functions. Such mutations can be further exploited for development of new attenuated alphaviruses.

VER-155008 induced Hsp70 proteins expression in fish cell cultures while impeding replication of two RNA viruses

The heat-shock protein 70 (Hsp70) inhibitor, VER-155008 (VER), was explored as a potential antiviral agent for two RNA viruses important to fish aquaculture, viral hemorrhagic septicemia virus (VHSV) and infectious pancreatic necrosis virus (IPNV). Studies were done at a temperature of 14 °C, and with cell lines commonly used to propagate these viruses. These were respectively EPC from fathead minnow for VHSV and CHSE-214 from Chinook salmon embryo for IPNV. Additionally, both viruses were studied with the Atlantic salmon heart endothelial cell line ASHe. For both VHSV and IPNV, 25 μM VER impeded replication. This was evidenced by delays in the development of cytopathic effect (CPE) and the expression of viral proteins, N for VHSV and VP2 for IPNV, and by less production of viral RNA and of viral titre. As VER inhibits the activity of Hsp70 family members, these results suggest that VHSV and IPNV utilize one or more Hsp70s in their life cycles. Yet neither virus induced Hsp70. Surprisingly VER alone induced Hsp70, but whether this induction modulated VER's antiviral effects is unknown. Exploring this apparent paradox in the future should improve the usefulness of VER as an antiviral agent.

Serotyping and Adaptation of Foot and Mouth Disease Virus in BHK-21 Cell Line towards the Development of Vaccine Candidate

This research work was conducted for isolation, identification and serotyping of Foot and Mouth Disease (FMD) virus from the field isolates of Gouripur Upazila of Mymensingh district, Bangladesh. Samples were collected from infected cattle in virus transportation medium and transported at the Department of Microbiology and Hygiene, Bangladesh Agricultural University, Mymensingh with maintain proper cool chain duringOctober to April 2012. Inocula were prepared from the collected samples and treated with antibiotics-antimycotics, preserved at -20°C for isolation and serotyping of the virus by antigen detecting ELISA method. After serotyping, the prepared inoculum was inoculated into 24hours confluent BHK-21 cell culture separately and incubated at 37°C for 48hours for development of CPE. Within 48hours of post infection, complete development of cytopathic effects (CPE) in BHK-21 cell culture were observed under inverted microscope which included the rounding and flattening of the cells, breaking down of the intracellular bridges and finally cell death which indicated the presence of FMD virus. Clear BHK-21 cell culture fluid was collected and preserved at -80°C as seed. Of the 20 samples, 15(75%) samples were found positive for FMDV in cell culture of which 13 samples of tongue epithelia (86.67%) and 2 samples of foot tissues (40%) were positive on the basis of cytopathic effects (CPE). Again the prepared inoculum was taken for serotyping the virus by ELISA method. On the basis of the result of ELISA, it was concluded that the serotype of the FMD virus of the collected field isolate was serotype “O”.

Isolation and Metagenomic Identification of Avian Leukosis Virus Associated with Mortality in Broiler Chicken.

Avian leukosis virus (ALV) belongs to the family Retroviridae and causes considerable economic losses to the poultry industry. Following an outbreak associated with high mortality in a broiler flock in northern part of Malaysia, kidney tissues from affected chickens were submitted for virus isolation and identification in chicken embryonated egg and MDCK cells. Evidence of virus growth was indicated by haemorrhage and embryo mortality in egg culture. While viral growth in cell culture was evidenced by the development of cytopathic effects. The isolated virus was purified by sucrose gradient and identified using negative staining transmission electron microscopy. Further confirmation was achieved through next-generation sequencing and nucleotide sequence homology search. Analysis of the viral sequences using the NCBI BLAST tool revealed 99-100% sequence homology with exogenous ALV viral envelope protein. Phylogenetic analysis based on partial envelope sequences showed the Malaysian isolate clustered with Taiwanese and Japanese ALV strains, which were closer to ALV subgroup J, ALV subgroup E, and recombinant A/E isolates. Based on these findings, ALV was concluded to be associated with the present outbreak. It was recommended that further studies should be conducted on the molecular epidemiology and pathogenicity of the identified virus isolate.

In vitro characteristics of cyprinid herpesvirus 2: effect of kidney extract supplementation on growth.

Herpesviral hematopoietic necrosis caused by goldfish hematopoietic necrosis virus (now identified as cyprinid herpesvirus 2, CyHV-2) has contributed to economic losses in goldfish Carassius auratus culture and is becoming a major obstacle in Prussian carp C. gibelio aquaculture in China. Several reports have described difficulties in culturing the virus, with the total loss of infectivity within several passages in cell culture. We succeeded in propagating CyHV-2 with a high infectious titer in a RyuF-2 cell line newly derived from the fin of the Ryukin goldfish variety using culture medium supplemented with 0.2% healthy goldfish kidney extract. The addition of kidney extract to the medium enabled rapid virus growth, resulting in the completion of cytopathic effect (CPE) within 4 to 6 d at 25°C. The extract also enabled reproducible virus culture with a titer of 105-6 TCID50 ml-1. The virus cultured using this protocol showed pathogenicity in goldfish after intraperitoneal injection. The virus grew in RyuF-2 cells at 15, 20, 25, 30, and 32°C but not at 34°C or higher. Higher incubation temperatures allowed earlier development of CPE, but culture at 30 and 32°C yielded a lower virus titer than that obtained at other temperatures because of heat inactivation of the propagated virus during cultivation. Cell lines derived from goldfish and ginbuna C. langsdorfii showed high susceptibility to the virus; cell lines from carp were susceptible to the virus using a medium containing goldfish kidney extract, but EPC, FHM, and BF-2 cell lines did not produce any CPE, even in the presence of the extract.

In vitro adaptation of SAV3 in cell culture correlates with reduced in vivo replication capacity and virulence to Atlantic salmon (Salmo salar L.) parr.

Salmonid alphavirus (SAV) is the causative agent of pancreas disease affecting Atlantic salmon and rainbow trout and causes a major burden to the aquaculture industry. This study describes a Norwegian subtype SAV3 virus isolate (SAV3-H10) subjected to serial passages in Chinook salmon embryo cells (CHSE-214) followed by Asian Grouper skin cells (AGK). Two passages from CHSE and one after transfer to AGK cells were chosen for further investigation, based on variation in degree and development of cytopathic effect (CPE). After plaque purification, several in vitro studies were performed. Cell viability after infection, viral replication and ability to cause morphological changes in CHSE and AGK cells was studied for the three isolates. The AGK-transferred isolate was identified with the strongest abilities to reduce cell viability, replicate more and cause more CPE in cell culture when compared with the early and late CHSE-grown isolates. Subsequently, the isolates were tested in an experimental fish challenge, showing higher viral load and higher pathological score for the least cell-cultured isolate. Full-length sequencing of the viral genome of the three isolates revealed divergence in four amino acid positions and the AGK-grown isolate also had a 3 nt deletion in the 3'UTR. In conclusion, we show that cell culture of SAV3-H10 selects for strains inducing earlier CPE in vitro with increased viral replication. In vivo, the effect is reversed, with lower replication levels and lower pathology scores in target organs. This study outlines a path to identify potential virulence motifs of SAV3.

Development of an Ussuri catfish Pseudobagrus ussuriensis skin cell line displaying differential cytopathic effects to three aquatic animal viruses

An Ussuri catfish Pseudobagrus ussuriensis skin (UCS) cell line was developed and subcultured for more than 60 passages. UCS cells consisted of mostly epithelial-like cells and multiplied well in TC199 medium supplemented with 10% fetal bovine serum at 25°C. Chromosome analysis revealed that most UCS cells had a normal diploid karyotype with 2n=52. UCS cells showed differential cytopathic effects (CPEs) after inoculation of spring viremia of carp virus (SVCV, a negative-strand RNA virus), grass carp reovirus (GCRV, a multi-segmented double-stranded RNA virus) and Rana grylio virus (RGV, a large double-stranded DNA virus), and were indicative of high sensitivities to these three aquatic animal viruses by a virus titration study. The CPE caused by SVCV appeared as rounded and granular cells, grape-like clusters and small lytic plaques. Characteristic CPE containing plaque-like syncytia was induced by GCRV. RGV-infected cells produced typical CPE characterized by cells shrinkage and aggregation, formation of clear plaques and cell sheet detachment. Furthermore, significant fluorescent signals were observed after UCS cells were transfected with green fluorescent protein reporter plasmids, and the development of CPE induced by a recombinant RGV, ΔTK-RGV, in UCS cells was illustrated using a combination of light and fluorescence microscopy. The data from this study suggested that UCS cell line can potentially serve as a useful tool for the comparison study of different aquatic animal viruses and the isolation of some newly emerging viruses in Ussuri catfish farming.

BIOLOGICAL, MOLECULAR AND IMMUNOCYTOCHEMICAL CHARACTERIZATION OF CELL CULTURE ADAPTED HUMAN ROTAVIRUS STRAINS DETECTED IN THE CITY OF PONTA GROSSA, PARANA, BRAZIL

Rotaviruses (RV) are the single most important cause of severe diarrheal illness in infants and young children in both developed and developing countries worldwide. They affect mainly children less than 24 months of age. Presently, we adapted human rotavirus strains from field materials in cell culture, as well as, studied their properties by the analyses of the cytopathic effect, immunofluorescence features, plaque properties and virus genome stability. The study was carried out with 53 rotavirus-positive fecal specimens, collected in the city of Ponta Grossa, Parana, before the introduction of vaccination program in Brazil. The samples were submitted to at least 3 blind passages in MA-104 cell culture before discarded as non-cultivable. The adaptation process was monitored by the development of the cytopathic effect, immunofluorescence assay , plaque assay and genome stability by reverse transcriptase-polymerase chain reactions amplification. Fourteen human rotavirus strains were adapted to grow in cell culture. The isolation was demonstrated by the development of typical cytopathic effect. Immunofluorescence assay revealed granular inclusions with specific fluorescence mainly at the perinuclear area of the infected cells. Plaque assay allowed the demonstration of plaques with varying diameter depending upon the strains. Reverse transcriptase-polymerase chain reactions resulted in amplification and genotyping, demonstrating the stability of the genome through cell culture adaptation. DOI: http://dx.doi.org/10.17525/vrr.v19i1.97

Infectious salmon anemia virus (ISAV) replication is transiently inhibited by Atlantic salmon type I interferon in cell culture

Infectious salmon anemia virus (ISAV) is a piscine orthomyxovirus, which causes multisystemic disease in farmed Atlantic salmon that may result in large losses. Previous work has suggested that ISAV is able to resist the antiviral state induced in cells by type I interferon (IFN). These studies were, however, mainly based on cytopathic effect (CPE) reduction assays. Here we have investigated the antiviral activity of Atlantic salmon IFNa1, IFNb and IFNc against ISAV using quantitative PCR (qPCR) of segment 6, Western blot analysis of ISAV proteins and viral yield reduction assays, in addition to CPE reduction assays. Antiviral effects of IFNs were tested against the high virulent strain ISAV4 and the low virulent strain ISAV7 both at the optimum growth temperature 15°C and at 20°C. As expected, IFNa1 showed little protection against CPE development in cells after infection with both strains at 15°C. However, the qPCR and Western blot analysis clearly showed strong inhibition of replication of the virus strains by IFNa1 between 24 and 72h after infection. The inhibitory effect declined four to five days post-infection, which explains the low protection against CPE development 7–10 days later. At 20°C, IFNa1 showed strong protection against CPE development, probably due to slower virus growth. IFNc showed similar antiviral activity as IFNa1 against ISAV4 while IFNb showed lower activity. There were observed differences between ISAV4 and ISAV7 both with respect inhibition by IFNa1 and ability to induce the two IFN-inducible antiviral effector proteins, Mx and ISG15, which may be related to differences in virulence properties and/or adaption to growth in cell culture.

A novel Ebola virus expressing luciferase allows for rapid and quantitative testing of antivirals

Ebola virus (EBOV) causes a severe hemorrhagic fever with case fatality rates of up to 90%, for which no antiviral therapies are available. Antiviral screening is hampered by the fact that development of cytopathic effect, the easiest means to detect infection with wild-type EBOV, is relatively slow. To overcome this problem we generated a recombinant EBOV carrying a luciferase reporter. Using this virus we show that EBOV entry is rapid, with viral protein expression detectable within 2h after infection. Further, luminescence-based assays were developed to allow highly sensitive titer determination within 48h. As a proof-of-concept for its utility in antiviral screening we used this virus to assess neutralizing antibodies and siRNAs, with significantly faster screening times than currently available wild-type or recombinant viruses. The availability of this recombinant virus will allow for more rapid and quantitative evaluation of antivirals against EBOV, as well as the study of details of the EBOV life cycle.

A method to measure an indicator of viraemia in Atlantic salmon using a reporter cell line

RTG-P1 is a transgenic fish cell line producing luciferase under the control of the IFN-induced Mx rainbow trout gene promoter. This cell line was used to measure viraemia of Salmonid alphavirus (SAV), the cause of Salmon Pancreas Disease (SPD), a serious disease in farmed Atlantic salmon. Two SAV genotype 1 (SAV1) isolates were used in this study, F93-125 (tissue-culture adapted, from Ireland) and 4640 (from a field case in Scotland). The kinetics and magnitude of luciferase activity were monitored versus the time of infection. During a direct infection experiment, the induction of luciferase significantly increased 16- and 4-fold after incubation for 6 days with F93-125 at 15 and 20°C, respectively. Filtration and heat treatment experiments demonstrated that the luciferase induction in RTG-P1 was dependent on viral replication. Unlike many cell lines used in fish viral diagnostic, RTG-P1 is not sensitive to salmonid serum, therefore, viraemia could be successfully monitored on serum collected from fish during a cohabitation challenge with 4640 isolate. A peak of viraemia could be detected 16 days post IP inoculation of the shedders. This novel cost-effective method to measure viraemia does not rely on development of cytopathic effect (CPE) in culture, is compatible with non-lethal blood collections in fish and can be used to assign emerging diseases to a viral aetiology.

New PARP Gene with an Anti-Alphavirus Function

Alphaviruses represent a highly important group of human and animal pathogens, which are transmitted by mosquito vectors between vertebrate hosts. The hallmark of alphavirus infection in vertebrates is the induction of a high-titer viremia, which is strongly dependent on the ability of the virus to interfere with host antiviral responses on both cellular and organismal levels. The identification of cellular factors, which are critical in orchestrating virus clearance without the development of cytopathic effect, may prove crucial in the design of new and highly effective antiviral treatments. To address this issue, we have developed a noncytopathic Venezuelan equine encephalitis virus (VEEV) mutant that can persistently replicate in cells defective in type I interferon (IFN) production or signaling but is cleared from IFN signaling-competent cells. Using this mutant, we analyzed (i) the spectrum of cellular genes activated by virus replication in the persistently infected cells and (ii) the spectrum of genes activated during noncytopathic virus clearance. By applying microarray-based technology and bioinformatic analysis, we identified a number of IFN-stimulated genes (ISGs) specifically activated during VEEV clearance. One of these gene products, the long isoform of PARP12 (PARP12L), demonstrated an inhibitory effect on the replication of VEEV, as well as other alphaviruses and several different types of other RNA viruses. Additionally, overexpression of two other members of the PARP gene superfamily was also shown to be capable of inhibiting VEEV replication.

A differentiated porcine bronchial epithelial cell culture model for studying human adenovirus tropism and virulence

The species specificity of human adenoviruses (HAdV) almost precludes studying virulence and tropism in animal models, e.g. rodent models, or derived tissue and cell culture models. However, replication of HAdV type 5 (HAdV-C5) has been shown after intravenous injection in swine. In order to study adenovirus replication in airway tissue propagation of bronchial epithelial cells from porcine lungs was established. These primary cells proved to be fully permissive for HAdV-C5 infection in submerged culture, demonstrating efficient HAdV genome replication, infectious viral particle release (1.07×108 TCID50/ml±6.63×107) and development of cytopathic effect (CPE). Differentiation of porcine bronchial epithelial cells was achieved at the air–liquid interface on collagen I coated 0.4μm polyester membranes. Morphology, expression of tubulin and occludin, the development of tight-junctions and cilia were similar to human bronchial epithelial cells. Infection with HAdV-C5 from the basolateral side resulted in release of infectious virus progeny (2.05×107 TCID50/ml±2.39×107) to the apical surface as described recently in human bronchial epithelial cells, although complete CPE was not observed. Differentiated porcine bronchial epithelial cells hold promise as a novel method for studying the virulence and pathophysiology of pneumonia associated HAdV types.

Theiler’s murine encephalomyelitis virus infection induces a redistribution of heat shock proteins 70 and 90 in BHK-21 cells, and is inhibited by novobiocin and geldanamycin

Theiler's murine encephalomyelitis virus (TMEV) is a positive-sense RNA virus belonging to the Cardiovirus genus in the family Picornaviridae. In addition to other host cellular factors and pathways, picornaviruses utilise heat shock proteins (Hsps) to facilitate their propagation in cells. This study investigated the localisation of Hsps 70 and 90 in TMEV-infected BHK-21 cells by indirect immunofluorescence and confocal microscopy. The effect of Hsp90 inhibitors novobiocin (Nov) and geldanamycin (GA) on the development of cytopathic effect (CPE) induced by infection was also examined. Hsp90 staining was uniformly distributed in the cytoplasm of uninfected cells but was found concentrated in the perinuclear region during late infection where it overlapped with the signal for non-structural protein 2C within the viral replication complex. Hsp70 redistributed into the vicinity of the viral replication complex during late infection, but its distribution did not overlap with that of 2C. Inhibition of Hsp90 by GA and Nov had a negative effect on virus growth over a 48-h period as indicated by no observable CPE in treated compared to untreated cells. 2C was detected by Western analysis of GA-treated infected cell lysates at doses between 0.01 and 0.125μM, suggesting that processing of viral precursors was not affected in the presence of this drug. In contrast, 2C was absent in cell lysates of Nov-treated cells at doses above 10μM, although CPE was evident 48hpi. This is the first study describing the dynamic behaviour of Hsps 70 and 90 in TMEV-infected cells and to identify Hsp90 as an important host factor in the life cycle of this virus.

Multiplication of Taura syndrome virus in primary hemocyte culture of shrimp ( Penaeus vannamei)

The propagation of Taura syndrome virus (TSV) in primary hemocyte culture of Pacific white shrimp ( Penaeus vannamei) was investigated. Purified TSV was inoculated into a 24 h old primary hemocyte culture and the development of cytopathic effects was monitored. The cell morphology started changing within 6 h post-inoculation; TSV-infected hemocytes started shrinking and granular structures began to form on the cell surface. There was a gradual loss of cell viability and, by 48 h post-inoculation, most cells detached from the bottom of the 96 well microplate. The propagation of TSV during the 48 h time course studied was measured by real-time RT-PCR. TSV copy number reached the highest level by 12 h post-inoculation and then started to decrease. Using an anti-TSV polyclonal antibody, the 55 kDa VP1 capsid protein was detected by Western blot analysis. The data suggest that shrimp primary hemocyte culture supports TSV replication and could be used as a tool for the study of host–virus interactions in TSV pathogenesis.

Evaluation of a recombinant measles virus expressing hepatitis C virus envelope proteins by infection of human PBL-NOD/Scid/Jak3null mouse

In this study, we infected NOD/Scid/Jak3null mice engrafted human peripheral blood leukocytes (hu-PBL-NOJ) with measles virus Edmonston B strain (MV-Edm) expressing hepatitis C virus (HCV) envelope proteins (rMV-E1E2) to evaluate the immunogenicity as a vaccine candidate. Although human leukocytes could be isolated from the spleen of mock-infected mice during the 2-weeks experiment, the proportion of engrafted human leukocytes in mice infected with MV (103–105 pfu) or rMV-E1E2 (104 pfu) was decreased. Viral infection of the splenocytes was confirmed by the development of cytopathic effects (CPEs) in co-cultures of splenocytes and B95a cells and verified using RT-PCR. Finally, human antibodies against MV were more frequently observed than E2-specific antibodies in serum from mice infected with a low dose of virus (MV, 100–101 pfu, and rMV-E1E2, 101–102 pfu). These results showed the possibility of hu-PBL-NOJ mice for the evaluation of the immunogenicity of viral proteins.

Human P-selectin glycoprotein ligand-1 is a functional receptor for enterovirus 71

Enterovirus 71 (EV71) is a major causative agent of hand, foot and mouth disease (HFMD), a common febrile disease occurring mainly in young children. Although clinical manifestations of HFMD are usually mild and self limiting, a severe EV71 outbreak can lead to a diverse array of neurological diseases. Identification of the specific cellular receptors is crucial for elucidating the mechanism of early virus-host interactions and the pathogenesis of enteroviruses. Here we identify human P-selectin glycoprotein ligand-1 (PSGL-1; CD162), a sialomucin membrane protein expressed on leukocytes that has a major role in early stages of inflammation, as a functional receptor for EV71 using an expression cloning method by panning. The N-terminal region of PSGL-1 binds specifically to EV71. Stable PSGL-1 expression allowed EV71 entry and replication, and development of cytopathic effects in nonsusceptible mouse L929 cells. Five out of eight EV71 strains bound soluble PSGL-1 and used intact PSGL-1 as the primary receptor for infection of Jurkat T cells. Three other EV71 strains did not use PSGL-1, suggesting the presence of strain-specific replication of EV71 in leukocytes. EV71 replicated in nonleukocyte cell lines in a PSGL-1-independent manner, indicating the presence of alternative receptor(s) for EV71. The identification of PSGL-1 as a receptor for EV71 sheds new light on a role for PSGL-1-positive leukocytes in cell tropism and pathogenesis during the course of HFMD and other EV71-mediated diseases.