Virological Assays Research Articles

Zika Virus Infectious Cell Culture System and the In Vitro Prophylactic Effect of Interferons.

Zika Virus (ZIKV) is an emerging pathogen that is linked to fetal developmental abnormalities such as microcephaly, eye defects, and impaired growth. ZIKV is an RNA virus of the Flaviviridae family. ZIKV is mainly transmitted by mosquitoes, but can also be spread by maternal to fetal vertical transmission as well as sexual contact. To date, there are no reliable treatment or vaccine options available to protect those infected by the virus. The development of a reproducible, effective Zika virus infectious cell culture system is critical for studying the molecular mechanisms of ZIKV replication as well as drug and vaccine development. In this regard, a protocol describing a mammalian cell-based in vitro Zika virus culture system for viral production and growth analysis is reported here. Details on the formation of plaques by Zika virus on a cell monolayer and plaque assay for measuring viral titer are presented. Viral genome replication kinetics and double-stranded RNA genome replicatory intermediates are determined. This culture platform was utilized to screen against a library of a small set of cytokines resulting in the identification of interferon-α (IFN-α), IFN-β and IFN-γ as potent inhibitors of Zika viral growth. In summary, an in vitro infectious Zika viral culture system and various virological assays are demonstrated in this study, which has the potential to greatly benefit the research community in elucidating further the mechanisms of viral pathogenesis and the evolution of viral virulence. Antiviral IFN-alpha can further be evaluated as a prophylactic, post-exposure prophylactic, and treatment option for Zika virus infections in high-risk populations, including infected pregnant women.

Use of Dried Blood Spots to Elucidate Full-Length Transmitted/Founder HIV-1 Genomes.

Background:Identification of HIV-1 genomes responsible for establishing clinical infection in newly infected individuals is fundamental to prevention and pathogenesis research. Processing, storage, and transportation of the clinical samples required to perform these virologic assays in resource-limited settings requires challenging venipuncture and cold chain logistics. Here, we validate the use of dried-blood spots (DBS) as a simple and convenient alternative to collecting and storing frozen plasma.Methods:We performed parallel nucleic acid extraction, single genome amplification (SGA), next generation sequencing (NGS), and phylogenetic analyses on plasma and DBS.Results:We demonstrated the capacity to extract viral RNA from DBS and perform SGA to infer the complete nucleotide sequence of the transmitted/founder (TF) HIV-1 envelope gene and full-length genome in two acutely infected individuals. Using both SGA and NGS methodologies, we showed that sequences generated from DBS and plasma display comparable phylogenetic patterns in both acute and chronic infection. SGA was successful on samples with a range of plasma viremia, including samples as low as 1,700 copies/ml and an estimated ~50 viral copies per blood spot. Further, we demonstrated reproducible efficiency in gp160 env sequencing in DBS stored at ambient temperature for up to three weeks or at -20°C for up to five months.Conclusions:These findings support the use of DBS as a practical and cost-effective alternative to frozen plasma for clinical trials and translational research conducted in resource-limited settings.

RETRACTED: Isolation and confirmation of viral nervous necrosis (VNN) disease in golden grey mullet (Liza aurata) and leaping mullet (Liza saliens) in the Iranian waters of the Caspian Sea

The present study was conducted on 428 moribund mullet fish samples to isolate and identify the causative agent of a mysterious acute mortality which recently occurred in wild mullets in Iranian waters of Caspian Sea, suspected to be due to viral nervous necrosis (VNN) disease. Disease investigation was carried out employing various diagnostic procedures such as virology, bacteriology, parasitology, haematology, histopathology, IFAT, IHC and nested RT-PCR. Brain and eye samples of affected fishes were collected in sterile conditions and then kept at -80°C for cell culture isolation and nested RT-PCR detection of the causative agent. Other tissue samples were also collected and fixed for histopathology, IHC and EM examinations. CPE was observed in cell cultures at 6days after inoculation. Nine samples were found positive with virological assay. Nested RT-PCR, performed on suspected tissues and CPE positive samples, showed that about 21 tissue samples and all the CPE positive samples were positive for VNN virus (VNNV). IFAT was selected as a confirmatory method for detecting the presence of Betanodavirus antigen, cell culture isolation results and nested RT-PCR findings. Moreover, VNNV particles with 25-30nm in diameter were also visualized in the infected brain and retina. In pathogenicity studies, guppy fishes bathed in VNNV-infected tissue culture (10(-4) TCID50) showed clinical signs similar to naturally infected mullet after 15days post infection (dpi), with mortality rates reaching up to 100% at 30dpi. Affected organ samples as examined by cell culture isolation, IFAT, IHC and histopathology, revealed the presence of VNNV in the guppy fishes. In conclusion, it was confirmed that VNNV was the main causative agent for the disease outbreak in mullet fish in the Caspian Sea, and this is such first official report of VNN disease from Iran.

467. Assay Conditions Significantly Alter AAV Neutralizing Antibody Determination

A major limitation of vectors based on current AAVs is the wide prevalence of memory B and T cells reactive to the AAV capsid in human populations arisen following natural AAV infection. The Neutralizing Antibody (NAB) assay guides experimentation and determines inclusion or exclusion of subjects in clinical studies in order to predict in vivo neutralization. Furthermore, evidence of a memory B-cell response to AAV may correlate with anti-capsid memory T-cell populations implicated in the safety and efficacy outcome of clinical AAV liver studies. Based on previously reported findings, NAB assay protocols in current use are unable to robustly predict in vivo neutralization in monkeys (Zinn et al. Cell Reports, 2015 & Wang et al. Mol Ther, 2010) leading to false negatives. In a clinical setting, the enrollment of a seropositive individual exposes the subject to undue risk, and generates outcome variability of the often small clinical studies. Here, we sought to permutate several of the NAB assay conditions in order to evaluate their impact on the NAB titer readout. Specifically, we varied the following variables: cell line, transgene detection, use of adenovirus, and AAV amount. Prior to evaluating these assay permutation, we sought to increase the sensitivity of the readout for transgene expression in the assay in order to evaluate at all conditions both high and low transducing AAV serotypes. This optimization increased our sensitivity by ~200-fold. With this increased sensitivity of readout, we first sought to evaluate the compliance of standard AAVNAB assays with the percentage law, formulated by Andrewes and Elford in 1933, a standard for virological NAB assays, which seeks stoichiometric conditions of NAB and viral load that enables measurement of NAB titers independent of viral input in the assay. Our data shows that at the conditions in common use in the field the percentage law is not upheld, and NAB titers are highly dependent on input viral load of the assay, directly impacting sensitivity and specificity, and leading to the occurrence of false negatives. Indeed, quantitative assessment of seroprevalence in primate populations with assays that reduce the amount of AAV to within percentage law range affects assay outcome qualitatively and quantitatively. We also independently assessed other assay parameters to improve sensitivity, robustness and reproducibility, and to study whether they may also have qualitative effects on titer outcomes. Our studies highlight the importance of pre-existing immunity in AAV gene therapy and limitations of the current methodologies to measure it in a robust and predictive manner. Data indicates the potential for false positive and negative readout for commonly used assay protocols. An optimized protocol was developed for further validation and evaluation. These studies may impact translational and clinical AAV gene therapy studies.

The Large Marseillevirus Explores Different Entry Pathways by Forming Giant Infectious Vesicles.

Triggering the amoebal phagocytosis process is a sine qua non condition for most giant viruses to initiate their replication cycle and consequently to promote their progeny formation. It is well known that the amoebal phagocytosis process requires the recognition of particles of >500 nm, and most amoebal giant viruses meet this requirement, such as mimivirus, pandoravirus, pithovirus, and mollivirus. However, in the context of the discovery of amoebal giant viruses in the last decade, Marseillevirus marseillevirus (MsV) has drawn our attention, because despite its ability to successfully replicate in Acanthamoeba, remarkably it does not fulfill the >500-nm condition, since it presents an ∼250-nm icosahedrally shaped capsid. We deeply investigated the MsV cycle by using a set of methods, including virological, molecular, and microscopic (immunofluorescence, scanning electron microscopy, and transmission electron microscopy) assays. Our results revealed that MsV is able to form giant vesicles containing dozens to thousands of viral particles wrapped by membranes derived from amoebal endoplasmic reticulum. Remarkably, our results strongly suggested that these giant vesicles are able to stimulate amoebal phagocytosis and to trigger the MsV replication cycle by an acidification-independent process. Also, we observed that MsV entry may occur by the phagocytosis of grouped particles (without surrounding membranes) and by an endosome-stimulated pathway triggered by single particles. Taken together, not only do our data deeply describe the main features of MsV replication cycle, but this is the first time, to our knowledge, that the formation of giant infective vesicles related to a DNA virus has been described. Triggering the amoebal phagocytosis process is a sine qua non condition required by most giant viruses to initiate their replication cycle. This process requires the recognition of particles of >500 nm, and many giant viruses meet this requirement. However, MsV is unusual, as despite having particles of ∼250 nm it is able to replicate in Acanthamoeba Our results revealed that MsV is able to form giant vesicles, containing dozens to thousands of viral particles, wrapped in membranes derived from amoebal endoplasmic reticulum. Remarkably, our results strongly suggest that these giant vesicles are able to stimulate phagocytosis using an acidification-independent process. Our work not only describes the main features of the MsV replication cycle but also describes, for the first time to our knowledge, the formation of huge infective vesicles in a large DNA viruses.

Structural Basis for Recognition of Human Enterovirus 71 by a Bivalent Broadly Neutralizing Monoclonal Antibody.

Enterovirus 71 (EV71) is the main pathogen responsible for hand, foot and mouth disease with severe neurological complications and even death in young children. We have recently identified a highly potent anti-EV71 neutralizing monoclonal antibody, termed D5. Here we investigated the structural basis for recognition of EV71 by the antibody D5. Four three-dimensional structures of EV71 particles in complex with IgG or Fab of D5 were reconstructed by cryo-electron microscopy (cryo-EM) single particle analysis all at subnanometer resolutions. The most critical EV71 mature virion-Fab structure was resolved to a resolution of 4.8 Å, which is rare in cryo-EM studies of virus-antibody complex so far. The structures reveal a bivalent binding pattern of D5 antibody across the icosahedral 2-fold axis on mature virion, suggesting that D5 binding may rigidify virions to prevent their conformational changes required for subsequent RNA release. Moreover, we also identified that the complementary determining region 3 (CDR3) of D5 heavy chain directly interacts with the extremely conserved VP1 GH-loop of EV71, which was validated by biochemical and virological assays. We further showed that D5 is indeed able to neutralize a variety of EV71 genotypes and strains. Moreover, D5 could potently confer protection in a mouse model of EV71 infection. Since the conserved VP1 GH-loop is involved in EV71 binding with its uncoating receptor, the scavenger receptor class B, member 2 (SCARB2), the broadly neutralizing ability of D5 might attribute to its inhibition of EV71 from binding SCARB2. Altogether, our results elucidate the structural basis for the binding and neutralization of EV71 by the broadly neutralizing antibody D5, thereby enhancing our understanding of antibody-based protection against EV71 infection.

Synergic effects between ocellatin-F1 and bufotenine on the inhibition of BHK-21 cellular infection by the rabies virus.

BackgroundRabies is an incurable neglected zoonosis with worldwide distribution characterized as a lethal progressive acute encephalitis caused by a lyssavirus. Animal venoms and secretions have long been studied as new bioactive molecular sources, presenting a wide spectrum of biological effects, including new antiviral agents. Bufotenine, for instance, is an alkaloid isolated from the skin secretion of the anuran Rhinella jimi that inhibits cellular penetration by the rabies virus. Antimicrobial peptides, such as ocellatin-P1 and ocellatin-F1, are present in the skin secretion of anurans from the genus Leptodactylus and provide chemical defense against predators and microorganisms.MethodsSkin secretion from captive Leptodactylus labyrinthicus was collected by mechanical stimulation, analyzed by liquid chromatography and mass spectrometry, and assayed for antiviral and cytotoxic activities. Synthetic peptides were obtained using solid phase peptide synthesis, purified by liquid chromatography and structurally characterized by mass spectrometry, and assayed in the same models. Cytotoxicity assays based on changes in cellular morphology were performed using baby hamster kidney (BHK-21) cells. Fixed Rabies virus (Pasteur Virus – PV) strain was used for virological assays based on rapid fluorescent focus inhibition test.ResultsHerein, we describe a synergic effect between ocellatin-F1 and bufotenine. This synergism was observed when screening the L. labyrinthicus skin secretion for antiviral activities. The active fraction major component was the antimicrobial peptide ocellatin-F1. Nevertheless, when the pure synthetic peptide was assayed, little antiviral activity was detectable. In-depth analyses of the active fraction revealed the presence of residual alkaloids together with ocellatin-F1. By adding sub-effective doses (e.g. < IC50) of pure bufotenine to synthetic ocellatin-F1, the antiviral effect was regained. Moreover, a tetrapetide derived from ocellatin-F1, based on alignment with the virus’s glycoprotein region inferred as a possible cell ligand, was able to maintain the synergic antiviral activity displayed by the full peptide.ConclusionsThis novel antiviral synergic effect between a peptide and an alkaloid may present an innovative lead for the study of new antiviral drugs.Electronic supplementary materialThe online version of this article (doi:10.1186/s40409-015-0048-1) contains supplementary material, which is available to authorized users.

Further Assessment of Monkeypox Virus Infection in Gambian Pouched Rats (Cricetomys gambianus) Using In Vivo Bioluminescent Imaging.

Monkeypox is a zoonosis clinically similar to smallpox in humans. Recent evidence has shown a potential risk of increased incidence in central Africa. Despite attempts to isolate the virus from wild rodents and other small mammals, no reservoir host has been identified. In 2003, Monkeypox virus (MPXV) was accidentally introduced into the U.S. via the pet trade and was associated with the Gambian pouched rat (Cricetomys gambianus). Therefore, we investigated the potential reservoir competence of the Gambian pouched rat for MPXV by utilizing a combination of in vivo and in vitro methods. We inoculated three animals by the intradermal route and three animals by the intranasal route, with one mock-infected control for each route. Bioluminescent imaging (BLI) was used to track replicating virus in infected animals and virological assays (e.g. real time PCR, cell culture) were used to determine viral load in blood, urine, ocular, nasal, oral, and rectal swabs. Intradermal inoculation resulted in clinical signs of monkeypox infection in two of three animals. One severely ill animal was euthanized and the other affected animal recovered. In contrast, intranasal inoculation resulted in subclinical infection in all three animals. All animals, regardless of apparent or inapparent infection, shed virus in oral and nasal secretions. Additionally, BLI identified viral replication in the skin without grossly visible lesions. These results suggest that Gambian pouched rats may play an important role in transmission of the virus to humans, as they are hunted for consumption and it is possible for MPXV-infected pouched rats to shed infectious virus without displaying overt clinical signs.

Comparison of Two Concentration Methods for the Molecular Detection of Enteroviruses in Raw and Treated Sewage.

Human enteric viruses are a major causative agent of emerging waterborne diseases and constitute a serious public health concern. Environmental contamination occurs through discharge of waste materials from infected persons. Methods for viral detection should be developed to detect low infective dose of enteric viruses in environment. In this study, we aimed at comparing two concentration methods for the detection of naturally occurring enteroviruses in raw and treated sewage. In the first method, polyethylene glycol is used to concentrate viral particles from the collected samples. The second method is based on ultracentrifugation of viral particles at high speed (110,000×g). Genomes of enteroviruses were quantified by the quantitative real-time PCR method in raw and treated sewage samples. PEG-based method yielded higher genomic copies of enteric viruses (with an average of 5.9 log10 genomic copies/100 mL) when applied to raw sewage samples. While the ultracentrifugation assay in the second method decreases genomic copies number (with an average of 5.4 log10 genomic copies/100 mL). The recovery differences between the two methods were not significant when applied to clean samples (treated sewage). This could be explained by the presence of inhibitors, which interfere with qRT-PCR, in less quantity comparatively to raw sewage. PEG-based method would be more accurate for samples with high-organic matter load. This report emphasizes the importance of matrices nature on the recovery of enteroviruses from sewage samples. This should be taken into consideration for establishing standardized virological assays to ensure the virological quality control of discharged water in environment.

Role of the DNA Sensor STING in Protection from Lethal Infection following Corneal and Intracerebral Challenge with Herpes Simplex Virus 1.

STING is a protein in the cytosolic DNA and cyclic dinucleotide sensor pathway that is critical for the initiation of innate responses to infection by various pathogens. Consistent with this, herpes simplex virus 1 (HSV-1) causes invariable and rapid lethality in STING-deficient (STING(-/-)) mice following intravenous (i.v.) infection. In this study, using real-time bioluminescence imaging and virological assays, as expected, we demonstrated that STING(-/-) mice support greater replication and spread in ocular tissues and the nervous system. In contrast, they did not succumb to challenge via the corneal route even with high titers of a virus that was routinely lethal to STING(-/-) mice by the i.v. route. Corneally infected STING(-/-) mice also showed increased periocular disease and increased corneal and trigeminal ganglia titers, although there was no difference in brain titers. They also showed elevated expression of tumor necrosis factor alpha (TNF-α) and CXCL9 relative to control mice but surprisingly modest changes in type I interferon expression. Finally, we also showed that HSV strains lacking the ability to counter autophagy and the PKR-driven antiviral state had near-wild-type virulence following intracerebral infection of STING(-/-) mice. Together, these data show that while STING is an important component of host resistance to HSV in the cornea, its previously shown immutable role in mediating host survival by the i.v. route was not recapitulated following a mucosal infection route. Furthermore, our data are consistent with the idea that HSV counters STING-mediated induction of the antiviral state and autophagy response, both of which are critical factors for survival following direct infection of the nervous system. HSV infections represent an incurable source of morbidity and mortality in humans and are especially severe in neonatal and immunocompromised populations. A key step in the development of an immune response is the recognition of microbial components within infected cells. The host protein STING is important in this regard for the recognition of HSV DNA and the subsequent triggering of innate responses. STING was previously shown to be essential for protection against lethal challenge from intravenous HSV-1 infection. In this study, we show that the requirement for STING depends on the infection route. In addition, STING is important for appropriate regulation of the inflammatory response in the cornea, and our data are consistent with the idea that HSV modulates STING activity through inhibition of autophagy. Our results elucidate the importance of STING in host protection from HSV-1 and demonstrate the redundancy of host protective mechanisms, especially following mucosal infection.

Host cell mTORC1 is required for HCV RNA replication

ObjectiveChronically HCV-infected orthotopic liver transplantation (OLT) recipients appear to have improved outcomes when their immunosuppressive regimen includes a mammalian target of rapamycin (mTOR) inhibitor. The mechanism underlying this observation is...

Glycerol Monolaurate Microbicide Protection against Repeat High-Dose SIV Vaginal Challenge

Measures to prevent sexual mucosal transmission are critically needed, particularly to prevent transmission to young women at high risk in the microepidemics in South Africa that disproportionally contribute to the continued pandemic. To that end, microbicides containing anti-retroviral (ARV) agents have been shown to prevent transmission, but with efficacy limited both by adherence and pre-existing innate immune and inflammatory conditions in the female reproductive tract (FRT). Glycerol monolaurate (GML) has been proposed as a microbicide component to enhance efficacy by blocking these transmission-facilitating innate immune response to vaginal exposure. We show here in an especially rigorous test of protection in the SIV-rhesus macaque model of HIV-1 transmission to women, that GML used daily and before vaginal challenge protects against repeat high doses of SIV by criteria that include virological and immunological assays to detect occult infection. We also provide evidence for indirect mechanisms of action in GML-mediated protection. Developing a sustained formulation for GML delivery could contribute an independent, complementary protective component to an ARV-containing microbicide.

227. Cancer Cell Susceptibility To Treatment With a Retroviral Replicating Vector Encoding Cytosine Deaminase and 5-FC Is Likely To Be Common

We are currently investigating the clinical utility of a Retroviral Replicating Vector (RRV), Toca 511 (vocimagene amiretrorepvec) which encodes an optimized yeast cytosine deaminase (yCD2) transgene, in recurrent high grade glioma (NCT01470794, NCT01156584 & NCT01985256). Toca 511, which is based on amphotropic murine gamma retroviruses, selectively infects tumors without immediate cell killing. Expression of virally-delivered yCD2 converts orally administered 5-fluorocytosine (5-FC) to 5-fluorouracil (5-FU) in infected tumor cells. There are several variables that could affect how well this combination therapy works in different tumors. By integrating a combination of RNA-seq, Liquid Chromatography/Mass Spectrophotometry (LC/MS), and PCR analysis with biochemical and virological assays, key criteria have been identified that help predict how Tocagen's Toca 511 RRV gene therapy will perform in several different tumor types. Efficient production and secretion of 5-FU by Toca511 infected tumor cells are expected to kill other uninfected cells in the immediate tumor microenvironment (the so-called “bystander” effect) and may, thereby, also influence the extent of induction of anti-tumor immune responses in animal models and patients. A panel of 9 established human tumors derived from 3 different tissue types (brain, colon and breast), each with unique histology, growth characteristics and morphology, was used to evaluate parameters central to effective antitumor activity in different indications. Parameters measured included: the rate of cell division; the rate of infection; the levels of CD gene integration and expression; intracellular and extracellular concentrations of 5-FC, 5-FU and downstream metabolites; gene expression levels of viral susceptibility genes and genes for pyrimidine metabolism. The data showed that: 1) all the tumor lines tested infected quite readily; 2) the rate of infection (varied 7-fold) was not dependent on the rate of cell division; 3) the expression of CD mRNA and protein were highly correlative with conversion of 5-FC to 5-FU; 4) all tumors were readily able to import 5-FC; 5) while LC/MS analysis established all tumors were readily able to import 5-FC, RNA-seq analysis correlated intracellular 5-FC levels with expression of SLC29A1, which codes for the main 5-FC transporter. Further, in vitro data from infected cell extracts, showed that the production of 5-FU could be augmented by increasing the 5-FC concentrations up to 5mg/mL. This suggests that infected tumor cells in vivo can kill uninfected nearby tumor cells better with higher doses of 5-FC. In summary, these studies identified multiple factors that influence Toca 511 gene therapy in the 9 tumor cell lines in culture. Data from this initial integrative approach further supports the conclusion that Toca 511 therapy is likely to be effective in killing multipletumortypes.

Visualizing real-time influenza virus infection, transmission and protection in ferrets.

Influenza transmission efficiency in ferrets is vital for risk-assessment studies. However, the inability to monitor viral infection and transmission dynamics in real time only provides a glimpse into transmissibility. Here we exploit a replication-competent influenza reporter virus to investigate dynamics of infection/transmission in ferrets. Bioluminescent imaging of ferrets infected with A/California/04/2009 H1N1 virus (CA/09) encoding NanoLuc (NLuc) luciferase provides the first real-time snapshot of influenza infection/transmission. Luminescence in the respiratory tract and in less well-characterized extra-pulmonary sites is observed, and imaging identifies infections in animals that would have otherwise been missed by traditional methods. Finally, the reporter virus significantly increases the speed and sensitivity of virological and serological assays. Thus, bioluminescent imaging of influenza infections rapidly determines intra-host dissemination, inter-host transmission and viral load, revealing infection dynamics and pandemic potential of the virus. These results have important implications for antiviral drug susceptibility, vaccine efficacy, transmissibility and pathogenicity studies.

The Catalytic Mechanism of Human Parainfluenza Virus Type 3 Haemagglutinin‐Neuraminidase Revealed

AbstractHuman parainfluenza virus type 3 (hPIV‐3) is one of the leading causes for lower respiratory tract disease in children, with neither an approved antiviral drug nor vaccine available to date. Understanding the catalytic mechanism of human parainfluenza virus haemagglutinin‐neuraminidase (HN) protein is key to the design of specific inhibitors against this virus. Herein, we used 1H NMR spectroscopy, X‐ray crystallography, and virological assays to study the catalytic mechanism of the HN enzyme activity and have identified the conserved Tyr530 as a key amino acid involved in catalysis. A novel 2,3‐difluorosialic acid derivative showed prolonged enzyme inhibition and was found to react and form a covalent bond with Tyr530. Furthermore, the novel derivative exhibited enhanced potency in virus blockade assays relative to its Neu2en analogue. These outcomes open the door for a new generation of potent inhibitors against hPIV‐3 HN.

The catalytic mechanism of human parainfluenza virus type 3 haemagglutinin-neuraminidase revealed.

Human parainfluenza virus type 3 (hPIV-3) is one of the leading causes for lower respiratory tract disease in children, with neither an approved antiviral drug nor vaccine available to date. Understanding the catalytic mechanism of human parainfluenza virus haemagglutinin-neuraminidase (HN) protein is key to the design of specific inhibitors against this virus. Herein, we used (1) H NMR spectroscopy, X-ray crystallography, and virological assays to study the catalytic mechanism of the HN enzyme activity and have identified the conserved Tyr530 as a key amino acid involved in catalysis. A novel 2,3-difluorosialic acid derivative showed prolonged enzyme inhibition and was found to react and form a covalent bond with Tyr530. Furthermore, the novel derivative exhibited enhanced potency in virus blockade assays relative to its Neu2en analogue. These outcomes open the door for a new generation of potent inhibitors against hPIV-3 HN.

Diagnostics and importance of hepatitis E virus infections

Abstract The diagnosis of hepatitis E virus (HEV) infections has been recently substantially facilitated by the introduction of a whole range of new different virological assays. The increasing appearance of sporadic cases of acute hepatitis E in Germany directed the focus toward the zoonotic transmission route of the virus. The recognition of HEV genotypes differing in virulence and in pathogenic potential is not only relevant for epidemiology and the course of the disease, but also for the development and choice of diagnostic tools. A broad variety of enzymatic and protein-based assay formats detecting anti-HEV IgG or IgM antibodies directed against the different genotype variants of HEV is available (ELISA, LIA, Western blot); however, sensitivity and specificity of these assays differ notably. Today’s state-of-the art technology that permits fast and reliable assay-based confirmation of HEV infections is PCR. The newly developed commercially available PCR kits will detect all four human pathogenic HEV genotypes. Further subdivision and discrimination can be achieved by sequencing, although this approach is only reasonable in the setting of specific epidemiological demands. Detection of viral antigens, cell culture, and T-cell assays are of no practical importance in a routine diagnostic setting. New insight into the pathogenesis and its clinical relevance for defined groups of patients (immunosuppressed) as well as the implementation of specific antiviral and prophylactic therapies (vaccination) will further challenge the performance of existing assay formats and increase the technical demands for the diagnostic laboratory.

Perihepatic nodes detected by point-of-care ultrasound in acute hepatitis and acute-on-chronic liver disease.

To study the manifestations of perihepatic lymph nodes during the episode of acute hepatitis flare by point-of-care ultrasonography. One hundred and seventy-six patients with an episode of acute hepatitis flare (ALT value > 5 × upper normal limit) were enrolled retrospectively. Diagnosis of etiology of the acute hepatitis flare was based on chart records and serological and virological assays. The patients were categorized into two groups (viral origin and non-viral origin) and further defined into ten subgroups according to the etiologies. An ultrasonograpy was performed within 2 h to 72 h (median, 8 h). The maximum size of each noticeable lymph node was measured. Correlation between clinical parameters and nodal manifestations was analyzed Enlarged lymph nodes (width ≥ 5mm) were noticeable in 110 (62.5%) patients, mostly in acute on chronic hepatitis B (54.5%). The viral group had a higher prevalence rate (89/110 = 80.9%) and larger nodal size (median, 7 mm) than those of the non-viral group (21/66 = 31.8%; median, 0 mm) (P < 0.001 for both). Meanwhile, there were significant differences in the nodal size between acute and chronic viral groups (P < 0.01), and between acute hepatitis A and non-hepatitis A viral groups (P < 0.001). In logistical regression analysis, the nodal width still showed strong significance in multivariate analysis (P < 0.0001) to stratify the two groups. The area under the curve of ROC was 0.805, with a sensitivity of 80.9%, a specificity of 68.2%, positive predictive value of 80.92%, negative predictive value of 68.18%, and an accuracy of 76.14%. Point-of-care ultrasonography to detect perihepatic nodal change is valuable for clarifying the etiologies in an episode of acute hepatitis flare.

Implementación del ensayo de carga viral COBAS Taqman HIV-1 Test, v1.0, para el diagnóstico de la infección congénita por HIV-1

Vertical transmission is the main route of HIV infection in childhood. Because of the persistence of maternal HIV antibodies, virologic assays that directly detect HIV are required to diagnose HIV infection in infants younger than 18months of age. The sensitivity of HIV RNA/DNA assays increases as the child becomes older. These tests have specificity values greater than 95%. The aim of this study was to evaluate the performance of the COBAS Taqman HIV-1 Test, v1.0 assay (Roche) and its concordance with a Multiplex Nested-PCR. Of 341 samples processed, 15 were positive and 326 negative by both methods. Sensitivity and specificity overall values for the viral load assay were 88.2% and 100%, respectively. Our results indicate that the COBAS Taqman assay evaluated could be used as an alternative method to diagnose HIV congenital infection.

A Vero-cell-adapted vaccine donor strain of influenza A virus generated by serial passages

A cell culture-based vaccine production system is preferred for the large-scale production of influenza vaccines and has advantages for generating vaccines against highly pathogenic influenza A viruses. Vero cells have been widely used in human vaccine manufacturing, and the safety of these cells has been well demonstrated. However, the most commonly used influenza-vaccine donor virus, A/Puerto Rico/8/1934 (PR8) virus, does not grow efficiently in Vero cells. Therefore, we adapted the PR8 virus to Vero cells by continuous passaging, and a high-growth strain was obtained after 20 passages. Sequence analysis and virological assays of the adapted strain revealed that mutations in four viral internal genes (NP, PB1, PA and NS1) were sufficient for adaptation. The recombinant virus harboring these mutations (PR8-4mut) displayed accelerated viral transport into the nucleus and increased RNP activity. Importantly, the PR8-4mut could serve as a backbone donor virus to support the growth of the H7N1, H9N2 and H5N1 avian viruses and the H1N1 and H3N2 human viruses in Vero cells without changing its pathogenicity in either chicken embryos or mice. Thus, our work describes the generation of a Vero-adapted, high-yield PR8-4mut virus that may serve as a promising candidate for an influenza-vaccine donor virus.