Propagation of avian influenza virus in embryonated ostrich eggs.

Influenza A viruses (IAVs) are typically isolated and cultured by successive passages using 9- to 11-day-old embryonated chicken eggs (ECEs) and in 14-day old ECEs for virus mutational studies. Real-time reverse transcription-polymerase chain reaction tests (RT-PCRs) are commonly used for IAV diagnosis, but virus isolation remains invaluable in terms of its high sensitivity, providing viable isolates for further studies and the ability to distinguish between viable and nonviable virus. Efforts at isolating ostrich-origin IAVs from RT-PCR positive specimens using ECEs have often been unsuccessful, raising the possibility of a species bottleneck, whereby ostrich-adapted IAVs may not readily infect and replicate in ECEs, yet the capacity of an ostrich embryo to support the replication of influenza viruses has not been previously demonstrated. This study describes an optimised method for H5 and H7 subtype IAV isolation and propagation in 28-day old embryonated ostrich eggs (EOEs), the biological equivalent of 14-day old ECEs. The viability of EOEs transported from breeding sites could be maximised by pre-incubating the eggs for 12 to 14 days prior to long-distance transportation. This method applied to studies for ostrich-adapted virus isolation and in ovo studies will enable better understanding of the virus-host interaction in ostriches and the emergence of potentially zoonotic diseases.

In Vitro and In Vivo Characterization of a Pigeon Paramyxovirus Type 1 Isolated from Domestic Pigeons in Victoria, Australia 2011.

Significant mortalities of racing pigeons occurred in Australia in late 2011 associated with a pigeon paramyxovirus serotype 1 (PPMV-1) infection. The causative agent, designated APMV-1/pigeon/Australia/3/2011 (P/Aus/3/11), was isolated from diagnostic specimens in specific pathogen free (SPF) embryonated eggs and was identified by a Newcastle Disease virus (NDV)-specific RT-PCR and haemagglutination inhibition (HI) test using reference polyclonal antiserum specific for NDV. The P/Aus/3/11 strain was further classified as PPMV-1 using the HI test and monoclonal antibody 617/161 by HI and phylogenetic analysis of the fusion gene sequence. The isolate P/Aus/3/11 had a slow haemagglutin-elution rate and was inactivated within 45 min at 56 °C. Cross HI tests generated an R value of 0.25, indicating a significant antigenic difference between P/Aus/3/11 and NDV V4 isolates. The mean death time (MDT) of SPF eggs infected with the P/Aus/3/11 isolate was 89.2 hr, characteristic of a mesogenic pathotype, consistent with other PPMV-1 strains. The plaque size of the P/Aus/3/11 isolate on chicken embryo fibroblast (CEF) cells was smaller than those of mesogenic and velogenic NDV reference strains, indicating a lower virulence phenotype in vitro and challenge of six-week-old SPF chickens did not induce clinical signs. However, sequence analysis of the fusion protein cleavage site demonstrated an 112RRQKRF117 motif, which is typical of a velogenic NDV pathotype. Phylogenetic analysis indicated that the P/Aus/3/11 isolate belongs to a distinct subgenotype within class II genotype VI of avian paramyxovirus type 1. This is the first time this genotype has been detected in Australia causing disease in domestic pigeons and is the first time since 2002 that an NDV with potential for virulence has been detected in Australia.

Functional neuraminidase inhibitor resistance motifs in avian influenza A(H5Nx) viruses.

Neuraminidase inhibitors (NAIs) are antiviral agents recommended worldwide to treat or prevent influenza virus infections in humans. Past influenza virus pandemics seeded by zoonotic infection by avian influenza viruses (AIV) as well as the increasing number of human infections with AIV have shown the importance of having information about resistance to NAIs by avian NAs that could cross the species barrier. In this study we introduced four NAI resistance-associated mutations (N2 numbering) previously found in human infections into the NA of three current AIV subtypes of the H5Nx genotype that threaten the poultry industry and human health: highly pathogenic H5N8, H5N6 and H5N2. Using the established MUNANA assay we showed that a R292K substitution in H5N6 and H5N2 viruses significantly reduced susceptibility to three licenced NAIs: oseltamivir, zanamivir and peramivir. In contrast the mutations E119V, H274Y and N294S had more variable effects with NAI susceptibility being drug- and strain-specific. We measured the replicative fitness of NAI resistant H5N6 viruses and found that they replicated to comparable or significantly higher titres in primary chicken cells and in embryonated hens' eggs as compared to wild type - despite the NA activity of the viral neuraminidase proteins being reduced. The R292K and N294S drug resistant H5N6 viruses had single amino acid substitutions in their haemagglutinin (HA): Y98F and A189T, respectively (H3 numbering) which reduced receptor binding properties possibly balancing the reduced NA activity seen. Our results demonstrate that the H5Nx viruses can support drug resistance mutations that confer reduced susceptibility to licenced NAIs and that these H5N6 viruses did not show diminished replicative fitness in avian cell cultures. Our results support the requirement for on-going surveillance of these strains in bird populations to include motifs associated with human drug resistance.

Staphylococcus aureus Lipase 1 Enhances Influenza A Virus Replication.

Influenza A virus (IAV) causes annual epidemics of respiratory disease in humans, often complicated by secondary coinfection with bacterial pathogens such as Staphylococcus aureus Here, we report that the S. aureus secreted protein lipase 1 enhances IAV replication in vitro in primary cells, including human lung fibroblasts. The proviral activity of lipase 1 is dependent on its enzymatic function, acts late in the viral life cycle, and results in increased infectivity through positive modulation of virus budding. Furthermore, the proviral effect of lipase 1 on IAV is exhibited during in vivo infection of embryonated hen's eggs and, importantly, increases the yield of a vaccine strain of IAV by approximately 5-fold. Thus, we have identified the first S. aureus protein to enhance IAV replication, suggesting a potential role in coinfection. Importantly, this activity may be harnessed to address global shortages of influenza vaccines.IMPORTANCE Influenza A virus (IAV) causes annual epidemics and sporadic pandemics of respiratory disease. Secondary bacterial coinfection by organisms such as Staphylococcus aureus is the most common complication of primary IAV infection and is associated with high levels of morbidity and mortality. Here, we report the first identified S. aureus factor (lipase 1) that enhances IAV replication during infection via positive modulation of virus budding. The effect is observed in vivo in embryonated hen's eggs and greatly enhances the yield of a vaccine strain, a finding that could be applied to address global shortages of influenza vaccines.

Shell-Less Egg Syndrome (SES) Widespread in Western Canadian Layer Operations Is Linked to a Massachusetts (Mass) Type Infectious Bronchitis Virus (IBV) Isolate.

A disease with a sudden drop in egg production and shell-less eggs called, shell-less egg syndrome (SES) has been observed in Western Canada egg layer flocks since 2010. The etiology of this disease is not known. We hypothesize that SES is caused by an infectious bronchitis virus (IBV) strain since it is known that IBV replicates in the shell gland causing various eggshell abnormalities. In this study, we screened egg layer flocks, in the provinces of Alberta (AB) and Saskatchewan (SK), with and without a history of SES for the presence of IBV infection. During 2015⁻2016, a total of 27 egg layer flocks were screened in AB (n = 7) and SK (n = 20). Eighty-one percent of the screened flocks (n = 22) were positive for IBV infection. Thirty of these isolates were successfully characterized using molecular tools targeting the most variable spike (S) 1 gene. IBV isolates from this study clustered into three genotypes based on partial S1 gene variability. The majority of the IBV isolates (70%) were Massachusetts (Mass) type, and the rest were either Connecticut (Conn) type or an uncharacterized genotype with genetic characteristics of Mass and Conn types. Since the majority of the IBV isolates included within the Mass type, we used a Mass type IBV isolate to reproduce SES in specific pathogen free (SPF) white leghorn chickens in lay. Further studies are warranted to investigate whether other IBV isolates can cause SES, to clarify the pathogenesis of SES and to develop a vaccine in order to prevent SES as observed in Western Canadian layer flocks.

Sera from Individuals with Narrowly Focused Influenza Virus Antibodies Rapidly Select Viral Escape Mutations In Ovo.

Influenza viruses use distinct antibody escape mechanisms depending on the overall complexity of the antibody response that is encountered. When grown in the presence of a hemagglutinin (HA) monoclonal antibody, influenza viruses typically acquire a single HA mutation that reduces the binding of that specific monoclonal antibody. In contrast, when confronted with mixtures of HA monoclonal antibodies or polyclonal sera that have antibodies that bind several HA epitopes, influenza viruses acquire mutations that increase HA binding to host cells. Recent data from our laboratory and others suggest that some humans possess antibodies that are narrowly focused on HA epitopes that were present in influenza virus strains that they were likely exposed to in childhood. Here, we completed a series of experiments to determine if humans with narrowly focused HA antibody responses are able to select for influenza virus antigenic escape variants in ovo We identified three human donors that possessed HA antibody responses that were heavily focused on a single HA antigenic site. Sera from all three of these donors selected single HA escape mutations during in ovo passage experiments, similar to what has been previously reported for single monoclonal antibodies. These single HA mutations directly reduced binding of serum antibodies used for selection. We propose that new antigenic variants of influenza viruses might originate in individuals who produce antibodies that are narrowly focused on HA epitopes that were present in viral strains that they encountered in childhood.IMPORTANCE Influenza vaccine strains must be updated frequently since circulating viral strains continuously change in antigenically important epitopes. Our previous studies have demonstrated that some individuals possess antibody responses that are narrowly focused on epitopes that were present in viral strains that they encountered during childhood. Here, we show that influenza viruses rapidly escape this type of polyclonal antibody response when grown in ovo by acquiring single mutations that directly prevent antibody binding. These studies improve our understanding of how influenza viruses evolve when confronted with narrowly focused polyclonal human antibodies.

Determination of influenza B identity and potency in quadrivalent inactivated influenza vaccines using lineage-specific monoclonal antibodies.

Co-circulation of two antigenically and genetically distinct lineages of influenza B virus, represented by prototype viruses B/Victoria/2/1987 and B/Yamagata/16/1988, has led to the development of quadrivalent influenza vaccines that contain two influenza B antigens. The inclusion of two influenza B antigens presents challenges for the production and regulation of inactivated quadrivalent vaccines, including the potential for cross-reactivity of the reagents used in identity and potency assays because of the relative close relatedness of the hemagglutinin (HA) from the two virus lineages. Monoclonal antibodies (mAbs) specific for the two lineages of influenza B HA were generated and characterized and used to set-up simple identity tests that distinguish the influenza B antigens in inactivated trivalent and quadrivalent vaccines. The lineage-specific mAbs bound well to the HA of influenza B strains included in influenza vaccines over a period of more than 10 years, suggesting that identity tests using such lineage-specific mAbs would not necessarily have to be updated with every influenza B vaccine strain change. These lineage-specific mAbs were also used in an antibody capture ELISA format to quantify HA in vaccine samples, including monovalent, trivalent, and quadrivalent vaccine samples from various manufacturers. The results demonstrated correlation with HA values determined by the traditional single radial immunodiffusion (SRID) assay. Further, the antibody-capture ELISA was able to distinguish heat-stressed vaccine from unstressed vaccine, and was similar to the SRID in quantifying the resultant loss of potency. These mAb reagents should be useful for further development of antibody-based alternative influenza B identity and potency assays.

Experimental vertical transmission of covert mortality nodavirus in Exopalaemon carinicauda.

Viral covert mortality disease (VCMD) has caused serious losses to shrimp aquaculture in China in recent years and the ridgetail white prawn Exopalaemon carinicauda has been suspected to be one important factor in perpetuating the high prevalence of covert mortality nodavirus (CMNV) infections due to its perennial presence in shrimp farming ponds and water from natural habitats. Experiments were carried out to determine the possibility of vertical transmission of CMNV in E. carinicauda in this study. CMNV infection in gonads, fertilized eggs and larvae was investigated by using the methods of reverse transcription nested PCR (nRT-PCR), in situ hybrization (ISH) and transmission electron microscopy (TEM). The ovarian tissue and testis tissue of artificially infected parental E. carinicauda were proved to be CMNV-positive by nRT-PCR. Fertilized eggs were also found to be CMNV-positive by nRT-PCR whether the fertilized eggs originated from the CMNV-positive female broodstock mated with the CMNV-negative male broodstock, or they originated from the CMNV-negative female broodstock mated with the CMNV-positive males. The results of ISH indicated that the positive signals were evident in the oocytes within ovarian tissue and nauplii. By TEM analysis, CMNV virions were observed in oogonia, oocytes, spermatocytes, fertilized eggs and nauplii. The presence of CMNV in fertilized eggs and larvae indicates that CMNV can transmit vertically via sperm and oocytes in E. carinicauda, which highlights the high probability of vertical transmission of CMNV in the main species of cultured shrimp and prawns.

Radix isatidis Polysaccharides Inhibit Influenza a Virus and Influenza A Virus-Induced Inflammation via Suppression of Host TLR3 Signaling In Vitro.

Influenza remains one of the major epidemic diseases worldwide, and rapid virus replication and collateral lung tissue damage caused by excessive pro-inflammatory host immune cell responses lead to high mortality rates. Thus, novel therapeutic agents that control influenza A virus (IAV) propagation and attenuate excessive pro-inflammatory responses are needed. Polysaccharide extract from Radix isatidis, a traditional Chinese herbal medicine, exerted potent anti-IAV activity against human seasonal influenza viruses (H1N1 and H3N2) and avian influenza viruses (H6N2 and H9N2) in vitro. The polysaccharides also significantly reduced the expression of pro-inflammatory cytokines (IL-6) and chemokines (IP-10, MIG, and CCL-5) stimulated by A/PR/8/34 (H1N1) at a range of doses (7.5 mg/mL, 15 mg/mL, and 30 mg/mL); however, they were only effective against progeny virus at a high dose. Similar activity was detected against inflammation induced by avian influenza virus H9N2. The polysaccharides strongly inhibited the protein expression of TLR-3 induced by PR8, suggesting that they impair the upregulation of pro-inflammatory factors induced by IAV by inhibiting activation of the TLR-3 signaling pathway. The polysaccharide extract from Radix isatidis root therefore has the potential to be used as an adjunct to antiviral therapy for the treatment of IAV infection.

Deep Sequencing of Influenza A Virus from a Human Challenge Study Reveals a Selective Bottleneck and Only Limited Intrahost Genetic Diversification.

Knowledge of influenza virus evolution at the point of transmission and at the intrahost level remains limited, particularly for human hosts. Here, we analyze a unique viral data set of next-generation sequencing (NGS) samples generated from a human influenza challenge study wherein 17 healthy subjects were inoculated with cell- and egg-passaged virus. Nasal wash samples collected from 7 of these subjects were successfully deep sequenced. From these, we characterized changes in the subjects' viral populations during infection and identified differences between the virus in these samples and the viral stock used to inoculate the subjects. We first calculated pairwise genetic distances between the subjects' nasal wash samples, the viral stock, and the influenza virus A/Wisconsin/67/2005 (H3N2) reference strain used to generate the stock virus. These distances revealed that considerable viral evolution occurred at various points in the human challenge study. Further quantitative analyses indicated that (i) the viral stock contained genetic variants that originated and likely were selected for during the passaging process, (ii) direct intranasal inoculation with the viral stock resulted in a selective bottleneck that reduced nonsynonymous genetic diversity in the viral hemagglutinin and nucleoprotein, and (iii) intrahost viral evolution continued over the course of infection. These intrahost evolutionary dynamics were dominated by purifying selection. Our findings indicate that rapid viral evolution can occur during acute influenza infection in otherwise healthy human hosts when the founding population size of the virus is large, as is the case with direct intranasal inoculation. IMPORTANCE: Influenza viruses circulating among humans are known to rapidly evolve over time. However, little is known about how influenza virus evolves across single transmission events and over the course of a single infection. To address these issues, we analyze influenza virus sequences from a human challenge experiment that initiated infection with a cell- and egg-passaged viral stock, which appeared to have adapted during its preparation. We find that the subjects' viral populations differ genetically from the viral stock, with subjects' viral populations having lower representation of the amino-acid-changing variants that arose during viral preparation. We also find that most of the viral evolution occurring over single infections is characterized by further decreases in the frequencies of these amino-acid-changing variants and that only limited intrahost genetic diversification through new mutations is apparent. Our findings indicate that influenza virus populations can undergo rapid genetic changes during acute human infections.

Research on the Vertical Transmission of Hepatitis C Gene from Father-to-child via Human Sperm.

BACKGROUND: The aim was to develop a better experimental model which could facilitate further studies assessing the vertical HCV gene transmission via human spermatozoa, and verify the possibility of father-to-child transmission of the HCV gene. METHODS: The recombinant plasmid pIRES2-EGFP-HCV C was constructed. Fluorescence in situ hybridization was performed to detect the integration of the HCV C gene in human sperm genome and in zygote's pronucleus. RESULTS: Successful construction of recombinant plasmid pIRES2-EGFP-HCV C was confirmed by restriction mapping, PCR, and sequencing. Positive HCV C DNA signals were observed in sperm heads, human sperm chromosomes and two-cell embryos in transfected samples. No positive signal was found in normal control and HCV infected groups. CONCLUSIONS: The recombinant plasmid pIRES2-EGFP-HCV C was successfully constructed. The HCV C gene was able to pass through the sperm membrane and integrate into the sperm genome. Human sperm carrying the HCV C gene was able to achieve normal fertilization. The replication of the sperm-mediated HCV C gene was synchronized with that of the host genome. Our results provide direct evidence for vertical transmission of the HCV C gene from father-to-child via human sperm.

Vector competence of two Indian populations of Culex quinquefasciatus (Diptera: Culicidae) mosquitoes to three West Nile virus strains.

BACKGROUND & OBJECTIVES: Culex quinquefasciatus is one of the principal vectors of West Nile virus (WNV). The mosquito also acts as a bridge vector as it feeds on both birds and humans. In the background of the recent reports of WNV activity in Kerala and Assam with fatalities, a study was initiated to determine the growth kinetics and transmission mechanisms of three strains of WNV in two populations of Cx. quinquefasciatus. METHODS: Mosquitoes were infected by oral feeding and growth on different post-infection days was determined with the three strains. Horizontal transmission was determined by confirming sickness and mortality in infant mice after infected mosquito bite. F1 generation eggs, larvae, pupae and adults of experimentally infected mosquitoes were screened for WNV to determine vertical (transovarial) transmission. Trans-stadial transmission was determined by detecting WNV in adult mosquitoes emerged from infected larvae. RESULTS: Both the mosquito populations replicated and maintained WNV for a prolonged period with high titers (≥ 5log10 PFU/ml). WNV could be detected in saliva from Days 2 to 32 post-infection. Horizontal transmission by both the populations could be established but no vertical transmission was observed. However, parenterally infected larvae transmitted WNV to adults. INTERPRETATION & CONCLUSION: WNV has been isolated from >10 mosquito species from India, however, vector competence of none of the species has been studied. The present study demonstrates efficient transmission of WNV by Cx. quinquefasciatus mosquitoes. With its country wide prevalence and high vector competence, the mosquitoes could create grave consequences especially when virulent strains with potential to cause acute flaccid paralysis and death are circulating.

A novel virus transmitted through pollination causes ring-spot disease on gentian (Gentiana triflora) ovaries.

In this study, we identified a novel virus from gentian (Gentiana triflora) that causes ring-spots on ovaries. Furthermore, the virus causes unusual symptoms, ring-spots that appear specifically on the outer surface of the ovarian wall after pollination. Pollen grains carrying the virus were used to infect host plants by hand-pollination. RNA extracted from purified virions indicated that the virus had two segments, RNA1 and RNA2. The full-length cDNA sequence indicated that RNA1 had two ORFs: ORF1 had methyltransferase and helicase motifs, and ORF2 had an RNA-dependent RNA polymerase motif. RNA2 had five ORFs encoding a coat protein, triple gene block proteins 1-3 and a cysteine-rich protein. The length of RNA1 was 5519 bases and that of RNA2 was 3810 bases not including a polyU/polyA region between the first and second ORFs. Viral RNA does not have a polyA tail at the 3' end. Sequence similarity and phylogenetic analysis suggested that the virus is closely related to members of the genera Pecluvirus and Hordeivirus but distinct from them. These combined results suggest that the causal agent inducing ring-spot symptoms on gentian ovaries is a new virus belonging to the family Virgaviridae but not to any presently known genus. We tentatively name the virus gentian ovary ring-spot virus.

Influenza viruses received and tested by the Melbourne WHO Collaborating Centre for Reference and Research on Influenza annual report, 2014.

The WHO Collaborating Centre for Reference and Research on Influenza in Melbourne is part of the World Health Organization's (WHO) Global Influenza Surveillance and Response System. In 2014 the Centre received a total of 5,374 influenza samples from laboratories primarily in the Asia-Pacific region. Viruses were characterised by their antigenic, genetic and antiviral drug resistance properties. Of the viruses successfully analysed 52% were A(H1N1)pdm09 viruses. The majority of these were antigenically and genetically similar to the WHO recommended reference strain for the 2014 Southern Hemisphere influenza vaccine. Results for A(H3N2) and B/Yamagata viruses suggested that circulating viruses of this subtype and lineage, respectively, had undergone antigenic and/or genetic changes, consistent with the decision by WHO to change recommended strains for the 2015 Southern Hemisphere vaccine. A small number of A(H1N1)pdm09 and B/Victoria viruses had highly reduced inhibition to the neuraminidase inhibitors oseltamivir and zanamivir. The Centre also undertook primary isolation of vaccine candidate viruses directly into eggs. A total of 38 viruses were successfully isolated in eggs, of which 1 (B/Phuket/3073/2013) was included in the 2015 Southern Hemisphere influenza vaccine.

Proteolytic enzymes in embryonated chicken eggs sustain the replication of egg-grown low-pathogenicity avian influenza viruses in cells in the absence of exogenous proteases.

Low pathogenic influenza viruses grow readily in embryonated chicken eggs but require the addition of exogenous proteases to grow in MDCK cell culture. In this study, we found that the influenza viruses propagated previously in eggs, can grow for up to two passages in cell culture without the addition of exogenous proteolytic enzymes. These results indicate that the reason for virus propagation in cells during the first two passages may be due to proteases from egg allantoic fluid carried over from egg culture. The ability of influenza viruses to grow in cells in the absence of trypsin is currently considered as a hallmark of highly pathogenic influenza viruses. Our data indicate that differentiating between high and low pathogenicity using cell culture only is not appropriate and other indicators such as sequence analysis and in vitro pathogenicity index should be performed.

Cloning of the genome of a goose parvovirus vaccine strain SYG61v and rescue of infectious virions from recombinant plasmid in embryonated goose eggs.

The SYG61v is an attenuated goose parvovirus (GPV) that has been used as a vaccine strain in China. The genome of SYG61v was sequenced to attempt to identify the genetic basis for the attenuation of this strain. The entire genome consists of 5102 nucleotides (nts), with four nt deletions compared to that of virulent strain B. The inverted terminal repeats (ITR) are 442 nts in length, of which 360 nts form a stem region, and 43 nts constitute the bubble region. Although mutations were observed throughout the ITR, no mismatch was found in the stem. Alignment with other pathogenic GPV strains (B, 82-0321, 06-0329, and YZ99-5) indicated that there are 10 and 11 amino acid mutations in the Rep1 and VP1 proteins of SYG61v, respectively. The complete genome of SYG61v was cloned into the pBluescript II vector and an infectious plasmid pSYG61v was generated. Infectious progeny virus was successfully rescued through transfection of the plasmid pSYG61v in embryonated goose eggs and yielded viral titers similar to its parental virus, as evaluated by ELD50.

Detection and differentiation of Newcastle disease virus and influenza virus by using duplex real-time PCR.

Newcastle disease virus (NDV), member of the Paramyxoviridae family and avian influenza virus (AIV), member of the Orthomyxoviridae family, are two main avian pathogens causing serious economic problems in poultry health. Both are enveloped, single-stranded, negative-sense RNA viruses and cause similar symptoms, ranging from sub-clinical infections to severe diseases, including decrease in egg production, acute respiratory syndrome, and high mortality. Similar symptoms hinder the differentiation of infection with the two viruses by standard veterinary procedures like clinical examination or necropsy. To overcome this problem, we have developed a new duplex real-time PCR assay for the detection and differentiation of these two viruses. Eighteen NDV strains, fourteen AIV strains, and twelve other (negative control) strains viruses were isolated from allantoic fluids of specific pathogen-free (SPF), embryonated eggs. Four-weeks-old SPF chickens were co-infected with both viruses (NDV - LaSota and AIV - H7N1). Swabs from cloaca and trachea were collected and examined. The results obtained in this study show that by using duplex real-time PCR, it was possible to detect and distinguish both viruses within less than three hours and with high sensitivity, even in case a bird was co-infected. Additionally, the results show the applicability of the real-time PCR assay in laboratory practice for the identification and differentiation of Newcastle disease and influenza A viruses in birds.

Comparative glycomics analysis of influenza Hemagglutinin (H5N1) produced in vaccine relevant cell platforms.

Hemagglutinin (HA) is the major antigen in influenza vaccines, and glycosylation is known to influence its antigenicity. Embryonated hen eggs are traditionally used for influenza vaccine production, but vaccines produced in mammalian and insect cells were recently licensed. This raises the concern that vaccines produced with different cell systems might not be equivalent due to differences in their glycosylation patterns. Thus, we developed an analytical method to monitor vaccine glycosylation through a combination of nanoLC/MS(E) and quantitative MALDI-TOF MS permethylation profiling. We then used this method to examine glycosylation of HAs from two different influenza H5N1 strains produced in five different platforms, including hen eggs, three different insect cell lines (High Five, expresSF+ and glycoengineered expresSF+), and a human cell line (HEK293). Our results demonstrated that (1) sequon utilization is not necessarily equivalent in different cell types, (2) there are quantitative and qualitative differences in the overall N-glycosylation patterns and structures produced by different cell types, (3) ∼20% of the N-glycans on the HAs produced by High Five cells are core α1,3-fucosylated structures, which may be allergenic in humans, and (4) our method can be used to monitor differences in glycosylation during the cellular glycoengineering stages of vaccine development.

The impact of maturation delay of mosquitoes on the transmission of West Nile virus.

We formulate and analyze a delay differential equation model for the transmission of West Nile virus between vector mosquitoes and avian hosts that incorporates maturation delay for mosquitoes. The maturation time from eggs to adult mosquitoes is sensitive to weather conditions, in particular the temperature, and the model allows us to investigate the impact of this maturation time on transmission dynamics of the virus among mosquitoes and birds. Numerical results of the model show that a combination of the maturation time and the vertical transmission of the virus in mosquitoes has substantial influence on the abundance and number of infection peaks of the infectious mosquitoes.

Enhanced transgenesis by intracytoplasmic injection of envelope-free lentivirus.

We demonstrate enhanced transgenesis in mice by intracytoplasmic injection of envelope-free lentivirus. Envelope-free lentivirus carrying the green fluorescent protein (GFP) gene under the control of the ubiquitin promoter (LVU-GFP) was microinjected into the cytoplasm of mouse zygotes prior to embryo transfer. Ninety-seven percent (31/32) of the adult mice were confirmed transgenic by PCR and Southern blot analysis; all founder mice express GFP when tail snips were examined by fluorescent microscopy prior to genomic DNA extraction. Transgene insertion numbers ranging from 1 to 32 were revealed by Southern blot analysis. Germline transmission was confirmed by the presence of transgene in F1 offspring. As expected, a lower transgenic rate (2.2%; 1/46) resulted when envelope-free LVU-GFP was microinjected into the perivitelline space (PVS) because cell recognition followed by membrane fusion between the viral envelope and the target cell is prerequisite for successful infection by envelope viruses. Here we demonstrate the competence of envelope-free lentivirus in establishing stable gene integration by germline transgenesis in mice at high efficiency, by intracytoplasmic viral injection (INVI) of envelope-free lentivirus into mouse zygotes.