Weijin Huang

Detection and assessment of infectivity of hepatitis E virus in urine

BACKGROUND & AIMS Hepatitis E virus (HEV) is known to be excreted in the stool but there has been no report of its presence in urine. This study investigated the presence of HEV RNA and antigen (HEV-Ag) in urine and its possible transmission. METHODS Serum and urine samples from patients with chronic or acute HEV infection and HEV infected monkeys were tested for viral and biochemical markers. Liver and kidney biopsies from the infected monkeys were analyzed by histopathology and immunohistochemistry. The infectivity of HEV from urine was assessed by inoculation into monkeys. RESULTS HEV RNA and HEV-Ag were detected persistently in the urine of a patient with chronic HEV infection. Subsequently, HEV RNA was detected in the urine of three of the eight (37.5%) acute patients, all of whom had detectable HEV-Ag in their urine. HEV RNA and HEV-Ag were also detectable in the urine of HEV infected monkeys. The ratio of HEV-Ag to RNA in the urine of the infected monkeys was significantly higher than in their sera and feces. The parameters of routine urinalysis remained within the normal ranges in the hepatitis E patients and infected monkeys, however, pathological changes and HEV-Ag were observed in the kidneys of the infected monkeys. Furthermore, one of two monkeys became infected with HEV after inoculation with urine from another infected monkey. CONCLUSIONS HEV infection may result in kidney injury and the urine may pose a risk of transmission. HEV-Ag detection in urine may be valuable for diagnosis of ongoing HEV infection.

Hepatitis E Virus Produced from Cell Culture Has a Lipid Envelope

The absence of a productive cell culture system hampered detailed analysis of the structure and protein composition of the hepatitis E virion. In this study, hepatitis E virus from a robust HEV cell culture system and from the feces of infected monkeys at the peak of virus excretion was purified by ultra-centrifugation. The common feature of the two samples after ultracentrifugation was that the ORF2 protein mainly remained in the top fractions. The ORF2 protein from cell culture system was glycosylated, with an apparent molecular weight of 88 kDa, and was not infectious in PLC/PRF/5 cells. The ORF2 protein in this fraction can bind to and protect HEV RNA from digestion by RNase A. The RNA-ORF2 product has a similar sedimentation coefficient to the virus from feces. The viral RNA in the cell culture supernatant was mainly in the fraction of 1.15g/cm3 but that from the feces was mainly in the fraction of 1.21 g/cm3. Both were infectious in PLC/PRF/5 cells. And the fraction in the middle of the gradient (1.06g/cm3) from the cell culture supernatant,but not that from the feces, also has ORF2 protein and HEV RNA but was not infectious in PLC/PRF/5.The infectious RNA-rich fraction from the cell culture contained ORF3 protein and lipid but the corresponding fraction from feces had no lipid and little ORF3 protein. The lipid on the surface of the virus has no effect on its binding to cells but the ORF3 protein interferes with binding. The result suggests that most of the secreted ORF2 protein is not associated with HEV RNA and that hepatitis E virus produced in cell culture differs in structure from the virus found in feces in that it has a lipid envelope.

A novel high-throughput vaccinia virus neutralization assay and preexisting immunity in populations from different geographic regions in China.

Background Pre-existing immunity to Vaccinia Tian Tan virus (VTT) resulting from a large vaccination campaign against smallpox prior to the early 1980s in China, has been a major issue for application of VTT-vector based vaccines. It is essential to establish a sensitive and high-throughput neutralization assay to understand the epidemiology of Vaccinia-specific immunity in current populations in China. Methodology/Principal Findings A new anti-Vaccinia virus (VACV) neutralization assay that used the attenuated replication-competent VTT carrying the firefly luciferase gene of Photinus pyralis (rTV-Fluc) was established and standardized for critical parameters that included the choice of cell line, viral infection dose, and the infection time. The current study evaluated the maintenance of virus-specific immunity after smallpox vaccination by conducting a non-randomized, cross-sectional analysis of antiviral antibody-mediated immune responses in volunteers examined 30–55 years after vaccination. The rTV-Fluc neutralization assay was able to detect neutralizing antibodies (NAbs) against Vaccinia virus without the ability to differentiate strains of Vaccinia virus. We showed that the neutralizing titers measured by our assay were similar to those obtained by the traditional plaque reduction neutralization test (PRNT). Using this assay, we found a low prevalence of NAb to VTT (7.6%) in individuals born before 1980 from Beijing and Anhui provinces in China, and when present, anti-VTT NAb titers were low. No NAbs were detected in all 222 samples from individuals born after 1980. There was no significant difference observed for titer or prevalence by gender, age range and geographic origin. Conclusion A simplified, sensitive, standardized, reproducible, and high-throughput assay was developed for the quantitation of NAbs against different Vaccinia strains. The current study provides useful insights for the future development of VTT-based vaccination in Beijing and Anhui provinces of China.

Development of a Triple-Color Pseudovirion-Based Assay to Detect Neutralizing Antibodies against Human Papillomavirus

Pseudovirion-based neutralization assay is considered the gold standard method for evaluating the immune response to human papillomavirus (HPV) vaccines. In this study, we developed a multicolor neutralization assay to simultaneously detect the neutralizing antibodies against different HPV types. FluoroSpot was used to interpret the fluorescent protein expression instead of flow cytometry. The results of FluoroSpot and flow cytometry showed good consistency, with R2 > 0.98 for the log-transformed IC50 values. Regardless of the reporter color, the single-, dual-, and triple-color neutralization assays reported identical results for the same samples. In low-titer samples from naturally HPV-infected individuals, there was strong agreement between the single- and triple-color assays, with kappa scores of 0.92, 0.89, and 0.96 for HPV16, HPV18, and HPV58, respectively. Good reproducibility was observed for the triple-color assay, with coefficients of variation of 2.0%–41.5% within the assays and 8.3%–36.2% between the assays. Three triple-color systems, HPV16-18-58, HPV6-33-45, and HPV11-31-52, were developed that could evaluate the immunogenicity of a nonavalent vaccine in three rounds of the assay. With the advantages of an easy-to-use procedure and less sample consumption, the multiple-color assay is more suitable than classical assays for large sero-epidemiological studies and clinical trials and is more amenable to automation.

Hepatitis E genotype 4 virus from feces of monkeys infected experimentally can be cultured in PLC/PRF/5 cells and upregulate host interferon‐inducible genes

The understanding of the interaction between hepatitis E virus (HEV) and its host cells has been impeded greatly by the absence of a cell culture system. In this study, an efficient cultivation method was developed in PLC/PRF/5 cells for HEV genotype 4 from the feces of monkeys infected experimentally. Compared to minimal essential medium (MEM), mixed Dulbeccos Modified Eagles Medium (DMEM)/M199 improved the infection efficiency of HEV in PLC/PRF/5 cells. The incubation time and temperature were set at 6 hr and 40°C, respectively. Compared to a 100% ELISA positive ratio (EPR) of 1 × 106 copies/ml HEV inoculated flasks, the ELISA positive ratio was 100%, 75%, 37.5%, and 100% for flasks inoculated with HEV incubated for 30 min under the conditions of pH 3.0, pH 11.0, 56°C and delipidation treatment, respectively. Gene expression profiles of HEV inoculated and control PLC/PRF/5 cells were assayed using a microarray. Four interferon‐inducible genes, IFI27, IFI6, Mx1, and CMPK2, were up‐regulated during HEV‐infection. Furthermore, the replication of HEV was inhibited at 3–14 days after treatment with 500 IU/ml IFN‐α2b. J. Med. Virol. 86: 1736–1744, 2014.

Comparison of the replication characteristics of vaccinia virus strains Guang 9 and Tian Tan in vivo and in vitro

Abstract Vaccinia virus is widely used as a vector in the development of recombinant vaccines. Vaccinia virus strain Guang 9 (VG9), which was derived from vaccinia virus strain Tian Tan (VTT) by successive plaque-cloning purification, was more attenuated than VTT. In this study, the host cell range and the growth and replication of VG9 were compared with those of VTT. The results showed that both VG9 and VTT could infect permissive cells (Vero, TK-143 and CEF) and semipermissive cells PK (15) and induced a visible cytopathic effect (CPE). Both strains could infect nonpermissive CHO-K1 cells but neither was able to reproduce. The replicative ability of VG9 was a little lower than that of VTT. Additionally, recombinant vaccinia viruses containing a firefly luciferase gene (VG9-L and VTT-L) were constructed, and their expression in vitro and replication and spread in vivo were compared. The expression ability of VG9-L was lower than that of VTT-L. Whole-animal imaging data indicated that VG9-L could reproduce quickly and express the exogenous protein at the site of inoculation, regardless of whether the intramuscular, intracutaneous, subcutaneous or celiac inoculation route was used. VG9-L was better in its ability to express a foreign protein than VTT-L, but the time during which expression occurred was shorter. There was no dissemination of virus in mice inoculated with either strain. In summary, this study demonstrates the possibility of using VG9 for the production of smallpox vaccines or the construction of recombinant vaccinia virus vaccines.

Identification of a novel DRB1 allele through intergenic recombination between HLA-DRB1 and HLA-DRB3∗02 in a Chinese family

In this study, a novel DRB1 allele was revealed by routine HLA-SBT typing noted for its extensive mismatches to any known DRB1 alleles within the exon 2. Sequences containing the exons 2, 3 of HLA-DRB1, their surrounding introns, and the full-length cDNA of DRB1 were analyzed to determine a possible recombination event. Interestingly, the sequences of entire exon 2 were characterized as DRB3(∗)02:02:01:01/02; while exon 3 were characterized as DRB1(∗)14 like alleles. Further analysis of the sequences using Simplot software suggested that an intergenic recombinant event (i.e. exchange of sequence between non-allelic genes) may have occurred between DRB3(∗)02 allele and DRB1(∗)14 like allele, and the recombination sites are located at intron 1 and the boundary of exon 2 and intron 2 of DRB1. There are 5 CGGGG sequences flanking each side of exon 2 could serve as potential recombination site. Moreover, the full-length cDNA of the novel allele has been identified. The exon 1 and exon 3 to exon 6 share the same sequence as DRB1(∗)14 like alleles. At the mRNA level, the new allele has no significant difference when compared with the other DRB1 allele. This novel recombinant allele is also found to be paternally inherited. In conclusion, this is the first report of a DRB1 and DRB3 intergenic recombination event involving whole exon 2, which generate a new DRB1(∗)14:141.

Optimization and validation of a high throughput method for detecting neutralizing antibodies against human papillomavirus (HPV) based on pseudovirons

The pseudoviron‐based neutralization assay is accepted as the gold standard to evaluate the functional humoral immune response against HPV. The goal of this study was to develop and optimize a human papillomavirus (HPV) neutralization assay using HPV pseudovirons with Gaussia luciferase (Gluc) as the reporter gene. For this purpose, high‐titers Gluc pseudovirons were generated by cotransfecting 293TT cells with HPV structural genes and Gluc expressing plasmids. Six types of neutralizing monoclonal antibodies, vaccines immunized serum samples and WHO international antibody standard were used to validate the new developed assay. The ideal circumstances of the assay were identified for cell counts (30,000/well for 96‐well plate), pseudoviron inoculating size (100 times RLU above background) and incubation time (72 hr). The sensitivity of the Gluc assay was comparable to secreted alkaline phosphatase (SEAP) assay and higher than the green florescent protein (GFP) assay. The non‐specific background for different types of sample was significantly different (rabbit sera > human sera > mouse sera, P < 0.01). The non‐specific neutralization effects were not attributed to IgG antibody. The cutoff value for this assay was determined as 50% inhibition at a dilution of 1:40. Without requirements of sample dilution and different incubation times at different temperature before processing, the detection time was shortened from more than 90 min to less than 5 min for a 96‐well plate compared with the SEAP‐based assay. With the advantages of short detection time and easy‐to‐use procedure, the newly developed assay is more suitable for large sero‐epidemiological studies or clinical trials and more amenable to automation. J. Med. Virol. 86:1542–1555, 2014.

Comparison on virulence and immunogenicity of two recombinant vaccinia vaccines, Tian Tan and Guang9 strains, expressing the HIV-1 envelope gene.

Background The vaccinia virus Guang9 strain (VG9), derived from the vaccinia virus Tian Tan strain (VTT) has been found to be less virulent than VTT. Methodology/Principal Findings To investigate whether VG9 could be a potential replicating virus vector, the TK genes in VG9 and VTT were replaced with the HIV-1 envelope gene via homologous recombination, resulting in the recombinant viruses, VG9-E and VTT-E. The biology, virulence, humoral and cellular immunological responses of VG9-E and VTT-E were evaluated. Our results indicated no obvious difference in range of host cells and diffusion between two recombinant viruses. Neurovirulence for VG9-E in weanling and suckling mice, and skin virulence in rabbits, were lower than that of VTT-E. The humoral immune responses, including binding antibody and neutralizing antibody responses, induced by VG9-E were not significantly different from those for VTT-E whilst IFN-γ response which represented cellular immune response induced by VG9-E was significantly higher than that did by VTT-E. Conclusions/Significance Our results indicated that VG9-E was less virulent, yet induced higher cellular immune response than VTT-E. Therefore, it could be an ideal replicating vaccinia vector for HIV vaccine research and development.

Asialoglycoprotein receptor facilitates infection of PLC/PRF/5 cells by HEV through interaction with ORF2

Although the biological and epidemiological features of hepatitis E virus (HEV) have been studied extensively in recent years, the mechanism by which HEV infects cells is still poorly understood. In this study, coimmunoprecipitation, pull‐down, and ELISA were used to show that the HEV ORF2 protein interacts directly with the ectodomain of both ASGR1 and ASGR2. Susceptibility to HEV correlated positively with the expression level of surface asialoglycoprotein receptor (ASGPR) in cell lines. ASGPR‐directed small interfering RNA (siRNA) in HEV‐infected PLC/PRF/5 cells had no significant effect on HEV release, suggesting that ASGPR mainly regulates the viral binding and entry steps. Both the purified ASGPR ectodomain and anti‐ASGPR antibodies disturbed the binding of HEV to PLC/PRF/5 cells. The classic ASGPR ligands asialofetuin, asialoganglioside, and fibronectin competitively inhibited the binding of HEV to hepatocytes in the presence of calcium. HeLa cell lines stably expressing ASGPR displayed increased HEV‐binding capacity, whereas ASGPR‐knockout PLC/PRF/5 cell lines had lower HEV‐binding capacity. Thus, our study demonstrates that ASGPR is involved in and facilitates HEV infection by binding to ORF2. J. Med. Virol. 88:2186–2195, 2016.