The Experts below are selected from a list of 5910 Experts worldwide ranked by ideXlab platform
Brian H. Bird - One of the best experts on this subject based on the ideXlab platform.
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rift valley fever virus vaccine lacking the nss and nsm genes is safe nonteratogenic and confers protection from viremia pyrexia and abortion following challenge in adult and pregnant sheep
Journal of Virology, 2011Co-Authors: Brian H. Bird, Louis H Maartens, Shelley Campbell, Baltus J Erasmus, Bobbie R Erickson, Kimberly A Dodd, Christina F Spiropoulou, Deborah Cannon, Clifton P DrewAbstract:ABSTRACT Rift Valley fever virus (RVFV) is a mosquito-borne human and Veterinary Pathogen causing large outbreaks of severe disease throughout Africa and the Arabian Peninsula. Safe and effective vaccines are critically needed, especially those that can be used in a targeted one-health approach to prevent both livestock and human disease. We report here on the safety, immunogenicity, and efficacy of the ΔNSs-ΔNSm recombinant RVFV (rRVFV) vaccine (which lacks the NSs and NSm virulence factors) in a total of 41 sheep, including 29 timed-pregnant ewes. This vaccine was proven safe and immunogenic for adult animals at doses ranging from 1.0 × 103 to 1.0 × 105 PFU administered subcutaneously (s.c.). Pregnant animals were vaccinated with 1.0 × 104 PFU s.c. at day 42 of gestation, when fetal sensitivity to RVFV vaccine-induced teratogenesis is highest. No febrile reactions, clinical illness, or pregnancy loss was observed following vaccination. Vaccination resulted in a rapid increase in anti-RVFV IgM (day 4) and IgG (day 7) titers. No seroconversion occurred in cohoused control animals. A subset of 20 ewes progressed to full-term delivery after vaccination. All lambs were born without musculoskeletal, neurological, or histological birth defects. Vaccine efficacy was assessed in 9 pregnant animals challenged at day 122 of gestation with virulent RVFV (1.0 × 106 PFU intravenously). Following challenge, 100% (9/9) of the animals were protected, progressed to full term, and delivered healthy lambs. As expected, all 3 sham-vaccinated controls experienced viremia, fetal death, and abortion postchallenge. These results demonstrate that the ΔNSs-ΔNSm rRVFV vaccine is safe and nonteratogenic and confers high-level protection in sheep.
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rift valley fever virus lacking the nss and nsm genes is highly attenuated confers protective immunity from virulent virus challenge and allows for differential identification of infected and vaccinated animals
Journal of Virology, 2008Co-Authors: Brian H. Bird, César G. Albariño, Bobbie R Erickson, Amy L Hartman, Thomas G Ksiazek, Stuart T. NicholAbstract:Rift Valley fever (RVF) virus is a mosquito-borne human and Veterinary Pathogen associated with large outbreaks of severe disease throughout Africa and more recently the Arabian peninsula. Infection of livestock can result in sweeping “abortion storms” and high mortality among young animals. Human infection results in self-limiting febrile disease that in ∼1 to 2% of patients progresses to more serious complications including hepatitis, encephalitis, and retinitis or a hemorrhagic syndrome with high fatality. The virus S segment-encoded NSs and the M segment-encoded NSm proteins are important virulence factors. The development of safe, effective vaccines and tools to screen and evaluate antiviral compounds is critical for future control strategies. Here, we report the successful reverse genetics generation of multiple recombinant enhanced green fluorescent protein-tagged RVF viruses containing either the full-length, complete virus genome or precise deletions of the NSs gene alone or the NSs/NSm genes in combination, thus creating attenuating deletions on multiple virus genome segments. These viruses were highly attenuated, with no detectable viremia or clinical illness observed with high challenge dosages (1.0 × 10 4 PFU) in the rat lethal disease model. A single-dose immunization regimen induced robust anti-RVF virus immunoglobulin G antibodies (titer, ∼1:6,400) by day 26 postvaccination. All vaccinated animals that were subsequently challenged with a high dose of virulent RVF virus survived infection and could be serologically differentiated from naive, experimentally infected animals by the lack of NSs antibodies. These rationally designed marker RVF vaccine viruses will be useful tools for in vitro screening of therapeutic compounds and will provide a basis for further development of RVF virus marker vaccines for use in endemic regions or following the natural or intentional introduction of the virus into previously unaffected areas.
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rift valley fever virus lacking nsm proteins retains high virulence in vivo and may provide a model of human delayed onset neurologic disease
Virology, 2007Co-Authors: Brian H. Bird, César G. Albariño, Stuart T. NicholAbstract:Rift Valley fever virus is a significant human and Veterinary Pathogen responsible for explosive outbreaks throughout Africa and the Arabian Peninsula. Severe acute disease in humans includes rapid onset hepatic disease and hemorrhagic fever or delayed onset encephalitis. A highly efficient reverse genetics system was developed which allowed generation of recombinant RVF viruses to assess the role of NSm protein in virulence in a rat model in which wild-type RVF virus strain ZH501 (wt-ZH501) results in 100% lethal hepatic disease 2-3 days post infection. While extensive genomic analysis indicates conservation of the NSm coding capability of diverse RVF viruses, and viruses deficient in NSs proteins are completely attenuated in vivo, comparison of wt-ZH501, a reverse genetics generated wt-ZH501 virus (R-ZH501), and R-ZH501 virus lacking the NSm proteins (R-DeltaNSm-ZH501) demonstrated that the NSm proteins were nonessential for in vivo virulence and lethality. Surprisingly, while 44% of R-DeltaNSm-ZH501 infected animals quickly developed lethal hepatic disease similar to wt- and R-ZH501, 17% developed delayed onset neurologic disease (lethargy, head tremors, and ataxia) at 13 days post infection. Such infections may provide the basis for study of both RVF acute hepatic disease and delayed onset encephalitic disease in humans.
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a shared transcription termination signal on negative and ambisense rna genome segments of rift valley fever sandfly fever sicilian and toscana viruses
Journal of Virology, 2007Co-Authors: César G. Albariño, Brian H. Bird, Stuart T. NicholAbstract:We present here an analysis of RNA transcription termination in three members of the genus Phlebovirus of the family Bunyaviridae, namely, Rift Valley fever virus (RVF virus), Sandfly fever Sicilian virus (SFS virus), and Toscana virus (TOS virus). Although grouped serologically, these viruses are quite distinct at the nucleotide level, with approximately 26 to 27% divergence, and have significantly different virus ecologies. Transmitted primarily by mosquitoes, RVF virus is a significant human and Veterinary Pathogen capable of causing explosive outbreaks of disease, ranging from mild febrile illness to hemorrhagic fever, throughout Africa and, more recently, the Arabian peninsula (3). TOS and SFS viruses are principally vectored by Phlebotomine sand flies and can cause mild febrile illness or encephalitic syndromes in humans (9, 23). While TOS virus is limited in geographic distribution to southern Europe, SFS virus is more widely spread and is found throughout Europe, the Mediterranean region, the Middle East, and northern Africa (6, 10). These viruses all share similar genome organizations consisting of tripartite negative-sense single-stranded RNA molecules. The large (L) RNA segment encodes the virus RNA-dependent RNA polymerase, the medium (M) segment encodes the precursor glycoproteins, and the ambisense small (S) segment RNA encodes the nucleoprotein (N) in genomic sense and a nonstructural protein (NSs) in the antigenomic orientation. The mechanism of mRNA transcription from segmented negative-sense RNA virus genomes has been described widely in the literature and includes several features that are shared between viruses in the genus Phlebovirus (family Bunyaviridae) and viruses in the family Arenaviridae (5, 20, 21). Initiation of transcription in these viruses involves a similar pathway involving priming by capped host mRNAs (18, 22). However, mRNA transcription termination is less well characterized, and poly(A) tails are not generally found at the 3′ ends of mRNAs of viruses of either family. Both genome segments (S and L) are ambisense in the Arenaviridae, whereas only the S segment is ambisense in the phleboviruses. Transcription termination in arenaviruses clearly involves substantial high-energy hairpin RNA secondary structures at the intervening junction between the ambisense open reading frames (ORFs) (17, 19). The situation is less clear for phlebovirus S segments. Earlier studies utilizing Punta Toro virus and an oligonucleotide hybrid mapping approach indicated that the Punta Toro virus N and NSs mRNA 3′ ends were located about 40 nucleotides (nt) from one another (11). Secondary structure prediction analysis suggested that this intervening intergenic region may be capable of forming hairpin structures, although less convincingly than for those found in arenaviruses. Hybridization studies of Uukuniemi virus mRNAs demonstrated that although the intergenic region is approximately 70 nt long, the 3′ ends of the virus N and NSs mRNAs overlap by approximately 100 nt (i.e., each mRNA terminates within the end of the other ORF) (22). It was predicted that a short AU-rich hairpin may form within this region, although this potential structure was of relatively low energy. A similar overlap in the 3′ ends of N and NSs mRNAs was also approximately mapped for TOS virus (14, 15). Such data, together with the prediction of potential hairpin structures at the ambisense junctions of the S and M RNA segments of the plant viruses of the genus Tospovirus (family Bunyaviridae), led to the prevailing view that mRNA transcription termination of ambisense genome RNA segments of bunyaviruses likely involves secondary structure mechanisms similar to those described for arenaviruses (5, 8, 21, 24). Transcription termination of the negative-strand L and M genome segments of phleboviruses and members of other genera within the family Bunyaviridae is generally considered to involve mechanisms other than RNA secondary structure terminators. Homopolymeric sequence elements have been found at or near the approximate locations of mRNA 3′ ends of several Bunyaviridae members, including members of the Phlebovirus genus (21). In particular, M segment mRNAs were found to terminate after a C-rich region in the virus templates of RVF virus (7) and TOS virus (15). Since RVF, SFS, and TOS viruses were also found to contain similar G-rich regions in the S segment (in the virus cRNA [vcRNA] sense), some investigators proposed that termination of N and NSs mRNAs might also be related to such sequence motifs (13). Clear evidence of specific linear sequence motifs on negative-sense genome RNA segments serving as distinct termination signals was found for Bunyamwera virus (genus Orthobunyavirus) (1). Termination of mRNA transcription in this case was highly sensitive to the exact primary nucleotide sequence located in these motifs. Minor perturbations of these Bunyamwera virus sequence motifs greatly inhibited the functionality of the termination signal. Using the 3′ rapid amplification of cDNA ends (3′RACE) technique, we were able to precisely determine the exact 3′ termini of the mRNAs of three diverse and medically important phleboviruses, namely, RVF, SFS, and TOS viruses. Surprisingly, a common core sequence motif was shown to represent a linear transcription termination signal both on the negative-sense M segments and on the ambisense S segments of these viruses. The absolute requirement of this transcription termination motif was demonstrated by successfully using a highly efficient RVF virus reverse genetics system (2, 12) to generate live recombinant RVF viruses with S segments lacking the termination signal motif for the NP or NSs mRNA and by showing that these recombinant viruses generated mRNAs which failed to terminate correctly. Interestingly, the mutant viruses were also found to have attenuated growth characteristics in cell culture. These findings provide a more complete understanding of the fundamental transcription mechanism of these viruses and suggest a mechanism for engineering additional S and M segment attenuation elements into live recombinant vaccines for these important diseases.
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rift valley fever virus lacking nsm proteins retains high virulence in vivo and may provide a model of human delayed onset neurologic disease
Virology, 2007Co-Authors: Brian H. Bird, César G. Albariño, Stuart T. NicholAbstract:Abstract Rift Valley fever virus is a significant human and Veterinary Pathogen responsible for explosive outbreaks throughout Africa and the Arabian Peninsula. Severe acute disease in humans includes rapid onset hepatic disease and hemorrhagic fever or delayed onset encephalitis. A highly efficient reverse genetics system was developed which allowed generation of recombinant RVF viruses to assess the role of NSm protein in virulence in a rat model in which wild-type RVF virus strain ZH501 (wt-ZH501) results in 100% lethal hepatic disease 2–3 days post infection. While extensive genomic analysis indicates conservation of the NSm coding capability of diverse RVF viruses, and viruses deficient in NSs proteins are completely attenuated in vivo , comparison of wt-ZH501, a reverse genetics generated wt-ZH501 virus (R-ZH501), and R-ZH501 virus lacking the NSm proteins (R-ΔNSm-ZH501) demonstrated that the NSm proteins were nonessential for in vivo virulence and lethality. Surprisingly, while 44% of R-ΔNSm-ZH501 infected animals quickly developed lethal hepatic disease similar to wt- and R-ZH501, 17% developed delayed onset neurologic disease (lethargy, head tremors, and ataxia) at 13 days post infection. Such infections may provide the basis for study of both RVF acute hepatic disease and delayed onset encephalitic disease in humans.
Stuart T. Nichol - One of the best experts on this subject based on the ideXlab platform.
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rift valley fever virus lacking the nss and nsm genes is highly attenuated confers protective immunity from virulent virus challenge and allows for differential identification of infected and vaccinated animals
Journal of Virology, 2008Co-Authors: Brian H. Bird, César G. Albariño, Bobbie R Erickson, Amy L Hartman, Thomas G Ksiazek, Stuart T. NicholAbstract:Rift Valley fever (RVF) virus is a mosquito-borne human and Veterinary Pathogen associated with large outbreaks of severe disease throughout Africa and more recently the Arabian peninsula. Infection of livestock can result in sweeping “abortion storms” and high mortality among young animals. Human infection results in self-limiting febrile disease that in ∼1 to 2% of patients progresses to more serious complications including hepatitis, encephalitis, and retinitis or a hemorrhagic syndrome with high fatality. The virus S segment-encoded NSs and the M segment-encoded NSm proteins are important virulence factors. The development of safe, effective vaccines and tools to screen and evaluate antiviral compounds is critical for future control strategies. Here, we report the successful reverse genetics generation of multiple recombinant enhanced green fluorescent protein-tagged RVF viruses containing either the full-length, complete virus genome or precise deletions of the NSs gene alone or the NSs/NSm genes in combination, thus creating attenuating deletions on multiple virus genome segments. These viruses were highly attenuated, with no detectable viremia or clinical illness observed with high challenge dosages (1.0 × 10 4 PFU) in the rat lethal disease model. A single-dose immunization regimen induced robust anti-RVF virus immunoglobulin G antibodies (titer, ∼1:6,400) by day 26 postvaccination. All vaccinated animals that were subsequently challenged with a high dose of virulent RVF virus survived infection and could be serologically differentiated from naive, experimentally infected animals by the lack of NSs antibodies. These rationally designed marker RVF vaccine viruses will be useful tools for in vitro screening of therapeutic compounds and will provide a basis for further development of RVF virus marker vaccines for use in endemic regions or following the natural or intentional introduction of the virus into previously unaffected areas.
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rift valley fever virus lacking nsm proteins retains high virulence in vivo and may provide a model of human delayed onset neurologic disease
Virology, 2007Co-Authors: Brian H. Bird, César G. Albariño, Stuart T. NicholAbstract:Rift Valley fever virus is a significant human and Veterinary Pathogen responsible for explosive outbreaks throughout Africa and the Arabian Peninsula. Severe acute disease in humans includes rapid onset hepatic disease and hemorrhagic fever or delayed onset encephalitis. A highly efficient reverse genetics system was developed which allowed generation of recombinant RVF viruses to assess the role of NSm protein in virulence in a rat model in which wild-type RVF virus strain ZH501 (wt-ZH501) results in 100% lethal hepatic disease 2-3 days post infection. While extensive genomic analysis indicates conservation of the NSm coding capability of diverse RVF viruses, and viruses deficient in NSs proteins are completely attenuated in vivo, comparison of wt-ZH501, a reverse genetics generated wt-ZH501 virus (R-ZH501), and R-ZH501 virus lacking the NSm proteins (R-DeltaNSm-ZH501) demonstrated that the NSm proteins were nonessential for in vivo virulence and lethality. Surprisingly, while 44% of R-DeltaNSm-ZH501 infected animals quickly developed lethal hepatic disease similar to wt- and R-ZH501, 17% developed delayed onset neurologic disease (lethargy, head tremors, and ataxia) at 13 days post infection. Such infections may provide the basis for study of both RVF acute hepatic disease and delayed onset encephalitic disease in humans.
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a shared transcription termination signal on negative and ambisense rna genome segments of rift valley fever sandfly fever sicilian and toscana viruses
Journal of Virology, 2007Co-Authors: César G. Albariño, Brian H. Bird, Stuart T. NicholAbstract:We present here an analysis of RNA transcription termination in three members of the genus Phlebovirus of the family Bunyaviridae, namely, Rift Valley fever virus (RVF virus), Sandfly fever Sicilian virus (SFS virus), and Toscana virus (TOS virus). Although grouped serologically, these viruses are quite distinct at the nucleotide level, with approximately 26 to 27% divergence, and have significantly different virus ecologies. Transmitted primarily by mosquitoes, RVF virus is a significant human and Veterinary Pathogen capable of causing explosive outbreaks of disease, ranging from mild febrile illness to hemorrhagic fever, throughout Africa and, more recently, the Arabian peninsula (3). TOS and SFS viruses are principally vectored by Phlebotomine sand flies and can cause mild febrile illness or encephalitic syndromes in humans (9, 23). While TOS virus is limited in geographic distribution to southern Europe, SFS virus is more widely spread and is found throughout Europe, the Mediterranean region, the Middle East, and northern Africa (6, 10). These viruses all share similar genome organizations consisting of tripartite negative-sense single-stranded RNA molecules. The large (L) RNA segment encodes the virus RNA-dependent RNA polymerase, the medium (M) segment encodes the precursor glycoproteins, and the ambisense small (S) segment RNA encodes the nucleoprotein (N) in genomic sense and a nonstructural protein (NSs) in the antigenomic orientation. The mechanism of mRNA transcription from segmented negative-sense RNA virus genomes has been described widely in the literature and includes several features that are shared between viruses in the genus Phlebovirus (family Bunyaviridae) and viruses in the family Arenaviridae (5, 20, 21). Initiation of transcription in these viruses involves a similar pathway involving priming by capped host mRNAs (18, 22). However, mRNA transcription termination is less well characterized, and poly(A) tails are not generally found at the 3′ ends of mRNAs of viruses of either family. Both genome segments (S and L) are ambisense in the Arenaviridae, whereas only the S segment is ambisense in the phleboviruses. Transcription termination in arenaviruses clearly involves substantial high-energy hairpin RNA secondary structures at the intervening junction between the ambisense open reading frames (ORFs) (17, 19). The situation is less clear for phlebovirus S segments. Earlier studies utilizing Punta Toro virus and an oligonucleotide hybrid mapping approach indicated that the Punta Toro virus N and NSs mRNA 3′ ends were located about 40 nucleotides (nt) from one another (11). Secondary structure prediction analysis suggested that this intervening intergenic region may be capable of forming hairpin structures, although less convincingly than for those found in arenaviruses. Hybridization studies of Uukuniemi virus mRNAs demonstrated that although the intergenic region is approximately 70 nt long, the 3′ ends of the virus N and NSs mRNAs overlap by approximately 100 nt (i.e., each mRNA terminates within the end of the other ORF) (22). It was predicted that a short AU-rich hairpin may form within this region, although this potential structure was of relatively low energy. A similar overlap in the 3′ ends of N and NSs mRNAs was also approximately mapped for TOS virus (14, 15). Such data, together with the prediction of potential hairpin structures at the ambisense junctions of the S and M RNA segments of the plant viruses of the genus Tospovirus (family Bunyaviridae), led to the prevailing view that mRNA transcription termination of ambisense genome RNA segments of bunyaviruses likely involves secondary structure mechanisms similar to those described for arenaviruses (5, 8, 21, 24). Transcription termination of the negative-strand L and M genome segments of phleboviruses and members of other genera within the family Bunyaviridae is generally considered to involve mechanisms other than RNA secondary structure terminators. Homopolymeric sequence elements have been found at or near the approximate locations of mRNA 3′ ends of several Bunyaviridae members, including members of the Phlebovirus genus (21). In particular, M segment mRNAs were found to terminate after a C-rich region in the virus templates of RVF virus (7) and TOS virus (15). Since RVF, SFS, and TOS viruses were also found to contain similar G-rich regions in the S segment (in the virus cRNA [vcRNA] sense), some investigators proposed that termination of N and NSs mRNAs might also be related to such sequence motifs (13). Clear evidence of specific linear sequence motifs on negative-sense genome RNA segments serving as distinct termination signals was found for Bunyamwera virus (genus Orthobunyavirus) (1). Termination of mRNA transcription in this case was highly sensitive to the exact primary nucleotide sequence located in these motifs. Minor perturbations of these Bunyamwera virus sequence motifs greatly inhibited the functionality of the termination signal. Using the 3′ rapid amplification of cDNA ends (3′RACE) technique, we were able to precisely determine the exact 3′ termini of the mRNAs of three diverse and medically important phleboviruses, namely, RVF, SFS, and TOS viruses. Surprisingly, a common core sequence motif was shown to represent a linear transcription termination signal both on the negative-sense M segments and on the ambisense S segments of these viruses. The absolute requirement of this transcription termination motif was demonstrated by successfully using a highly efficient RVF virus reverse genetics system (2, 12) to generate live recombinant RVF viruses with S segments lacking the termination signal motif for the NP or NSs mRNA and by showing that these recombinant viruses generated mRNAs which failed to terminate correctly. Interestingly, the mutant viruses were also found to have attenuated growth characteristics in cell culture. These findings provide a more complete understanding of the fundamental transcription mechanism of these viruses and suggest a mechanism for engineering additional S and M segment attenuation elements into live recombinant vaccines for these important diseases.
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rift valley fever virus lacking nsm proteins retains high virulence in vivo and may provide a model of human delayed onset neurologic disease
Virology, 2007Co-Authors: Brian H. Bird, César G. Albariño, Stuart T. NicholAbstract:Abstract Rift Valley fever virus is a significant human and Veterinary Pathogen responsible for explosive outbreaks throughout Africa and the Arabian Peninsula. Severe acute disease in humans includes rapid onset hepatic disease and hemorrhagic fever or delayed onset encephalitis. A highly efficient reverse genetics system was developed which allowed generation of recombinant RVF viruses to assess the role of NSm protein in virulence in a rat model in which wild-type RVF virus strain ZH501 (wt-ZH501) results in 100% lethal hepatic disease 2–3 days post infection. While extensive genomic analysis indicates conservation of the NSm coding capability of diverse RVF viruses, and viruses deficient in NSs proteins are completely attenuated in vivo , comparison of wt-ZH501, a reverse genetics generated wt-ZH501 virus (R-ZH501), and R-ZH501 virus lacking the NSm proteins (R-ΔNSm-ZH501) demonstrated that the NSm proteins were nonessential for in vivo virulence and lethality. Surprisingly, while 44% of R-ΔNSm-ZH501 infected animals quickly developed lethal hepatic disease similar to wt- and R-ZH501, 17% developed delayed onset neurologic disease (lethargy, head tremors, and ataxia) at 13 days post infection. Such infections may provide the basis for study of both RVF acute hepatic disease and delayed onset encephalitic disease in humans.
César G. Albariño - One of the best experts on this subject based on the ideXlab platform.
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rift valley fever virus lacking the nss and nsm genes is highly attenuated confers protective immunity from virulent virus challenge and allows for differential identification of infected and vaccinated animals
Journal of Virology, 2008Co-Authors: Brian H. Bird, César G. Albariño, Bobbie R Erickson, Amy L Hartman, Thomas G Ksiazek, Stuart T. NicholAbstract:Rift Valley fever (RVF) virus is a mosquito-borne human and Veterinary Pathogen associated with large outbreaks of severe disease throughout Africa and more recently the Arabian peninsula. Infection of livestock can result in sweeping “abortion storms” and high mortality among young animals. Human infection results in self-limiting febrile disease that in ∼1 to 2% of patients progresses to more serious complications including hepatitis, encephalitis, and retinitis or a hemorrhagic syndrome with high fatality. The virus S segment-encoded NSs and the M segment-encoded NSm proteins are important virulence factors. The development of safe, effective vaccines and tools to screen and evaluate antiviral compounds is critical for future control strategies. Here, we report the successful reverse genetics generation of multiple recombinant enhanced green fluorescent protein-tagged RVF viruses containing either the full-length, complete virus genome or precise deletions of the NSs gene alone or the NSs/NSm genes in combination, thus creating attenuating deletions on multiple virus genome segments. These viruses were highly attenuated, with no detectable viremia or clinical illness observed with high challenge dosages (1.0 × 10 4 PFU) in the rat lethal disease model. A single-dose immunization regimen induced robust anti-RVF virus immunoglobulin G antibodies (titer, ∼1:6,400) by day 26 postvaccination. All vaccinated animals that were subsequently challenged with a high dose of virulent RVF virus survived infection and could be serologically differentiated from naive, experimentally infected animals by the lack of NSs antibodies. These rationally designed marker RVF vaccine viruses will be useful tools for in vitro screening of therapeutic compounds and will provide a basis for further development of RVF virus marker vaccines for use in endemic regions or following the natural or intentional introduction of the virus into previously unaffected areas.
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rift valley fever virus lacking nsm proteins retains high virulence in vivo and may provide a model of human delayed onset neurologic disease
Virology, 2007Co-Authors: Brian H. Bird, César G. Albariño, Stuart T. NicholAbstract:Rift Valley fever virus is a significant human and Veterinary Pathogen responsible for explosive outbreaks throughout Africa and the Arabian Peninsula. Severe acute disease in humans includes rapid onset hepatic disease and hemorrhagic fever or delayed onset encephalitis. A highly efficient reverse genetics system was developed which allowed generation of recombinant RVF viruses to assess the role of NSm protein in virulence in a rat model in which wild-type RVF virus strain ZH501 (wt-ZH501) results in 100% lethal hepatic disease 2-3 days post infection. While extensive genomic analysis indicates conservation of the NSm coding capability of diverse RVF viruses, and viruses deficient in NSs proteins are completely attenuated in vivo, comparison of wt-ZH501, a reverse genetics generated wt-ZH501 virus (R-ZH501), and R-ZH501 virus lacking the NSm proteins (R-DeltaNSm-ZH501) demonstrated that the NSm proteins were nonessential for in vivo virulence and lethality. Surprisingly, while 44% of R-DeltaNSm-ZH501 infected animals quickly developed lethal hepatic disease similar to wt- and R-ZH501, 17% developed delayed onset neurologic disease (lethargy, head tremors, and ataxia) at 13 days post infection. Such infections may provide the basis for study of both RVF acute hepatic disease and delayed onset encephalitic disease in humans.
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a shared transcription termination signal on negative and ambisense rna genome segments of rift valley fever sandfly fever sicilian and toscana viruses
Journal of Virology, 2007Co-Authors: César G. Albariño, Brian H. Bird, Stuart T. NicholAbstract:We present here an analysis of RNA transcription termination in three members of the genus Phlebovirus of the family Bunyaviridae, namely, Rift Valley fever virus (RVF virus), Sandfly fever Sicilian virus (SFS virus), and Toscana virus (TOS virus). Although grouped serologically, these viruses are quite distinct at the nucleotide level, with approximately 26 to 27% divergence, and have significantly different virus ecologies. Transmitted primarily by mosquitoes, RVF virus is a significant human and Veterinary Pathogen capable of causing explosive outbreaks of disease, ranging from mild febrile illness to hemorrhagic fever, throughout Africa and, more recently, the Arabian peninsula (3). TOS and SFS viruses are principally vectored by Phlebotomine sand flies and can cause mild febrile illness or encephalitic syndromes in humans (9, 23). While TOS virus is limited in geographic distribution to southern Europe, SFS virus is more widely spread and is found throughout Europe, the Mediterranean region, the Middle East, and northern Africa (6, 10). These viruses all share similar genome organizations consisting of tripartite negative-sense single-stranded RNA molecules. The large (L) RNA segment encodes the virus RNA-dependent RNA polymerase, the medium (M) segment encodes the precursor glycoproteins, and the ambisense small (S) segment RNA encodes the nucleoprotein (N) in genomic sense and a nonstructural protein (NSs) in the antigenomic orientation. The mechanism of mRNA transcription from segmented negative-sense RNA virus genomes has been described widely in the literature and includes several features that are shared between viruses in the genus Phlebovirus (family Bunyaviridae) and viruses in the family Arenaviridae (5, 20, 21). Initiation of transcription in these viruses involves a similar pathway involving priming by capped host mRNAs (18, 22). However, mRNA transcription termination is less well characterized, and poly(A) tails are not generally found at the 3′ ends of mRNAs of viruses of either family. Both genome segments (S and L) are ambisense in the Arenaviridae, whereas only the S segment is ambisense in the phleboviruses. Transcription termination in arenaviruses clearly involves substantial high-energy hairpin RNA secondary structures at the intervening junction between the ambisense open reading frames (ORFs) (17, 19). The situation is less clear for phlebovirus S segments. Earlier studies utilizing Punta Toro virus and an oligonucleotide hybrid mapping approach indicated that the Punta Toro virus N and NSs mRNA 3′ ends were located about 40 nucleotides (nt) from one another (11). Secondary structure prediction analysis suggested that this intervening intergenic region may be capable of forming hairpin structures, although less convincingly than for those found in arenaviruses. Hybridization studies of Uukuniemi virus mRNAs demonstrated that although the intergenic region is approximately 70 nt long, the 3′ ends of the virus N and NSs mRNAs overlap by approximately 100 nt (i.e., each mRNA terminates within the end of the other ORF) (22). It was predicted that a short AU-rich hairpin may form within this region, although this potential structure was of relatively low energy. A similar overlap in the 3′ ends of N and NSs mRNAs was also approximately mapped for TOS virus (14, 15). Such data, together with the prediction of potential hairpin structures at the ambisense junctions of the S and M RNA segments of the plant viruses of the genus Tospovirus (family Bunyaviridae), led to the prevailing view that mRNA transcription termination of ambisense genome RNA segments of bunyaviruses likely involves secondary structure mechanisms similar to those described for arenaviruses (5, 8, 21, 24). Transcription termination of the negative-strand L and M genome segments of phleboviruses and members of other genera within the family Bunyaviridae is generally considered to involve mechanisms other than RNA secondary structure terminators. Homopolymeric sequence elements have been found at or near the approximate locations of mRNA 3′ ends of several Bunyaviridae members, including members of the Phlebovirus genus (21). In particular, M segment mRNAs were found to terminate after a C-rich region in the virus templates of RVF virus (7) and TOS virus (15). Since RVF, SFS, and TOS viruses were also found to contain similar G-rich regions in the S segment (in the virus cRNA [vcRNA] sense), some investigators proposed that termination of N and NSs mRNAs might also be related to such sequence motifs (13). Clear evidence of specific linear sequence motifs on negative-sense genome RNA segments serving as distinct termination signals was found for Bunyamwera virus (genus Orthobunyavirus) (1). Termination of mRNA transcription in this case was highly sensitive to the exact primary nucleotide sequence located in these motifs. Minor perturbations of these Bunyamwera virus sequence motifs greatly inhibited the functionality of the termination signal. Using the 3′ rapid amplification of cDNA ends (3′RACE) technique, we were able to precisely determine the exact 3′ termini of the mRNAs of three diverse and medically important phleboviruses, namely, RVF, SFS, and TOS viruses. Surprisingly, a common core sequence motif was shown to represent a linear transcription termination signal both on the negative-sense M segments and on the ambisense S segments of these viruses. The absolute requirement of this transcription termination motif was demonstrated by successfully using a highly efficient RVF virus reverse genetics system (2, 12) to generate live recombinant RVF viruses with S segments lacking the termination signal motif for the NP or NSs mRNA and by showing that these recombinant viruses generated mRNAs which failed to terminate correctly. Interestingly, the mutant viruses were also found to have attenuated growth characteristics in cell culture. These findings provide a more complete understanding of the fundamental transcription mechanism of these viruses and suggest a mechanism for engineering additional S and M segment attenuation elements into live recombinant vaccines for these important diseases.
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rift valley fever virus lacking nsm proteins retains high virulence in vivo and may provide a model of human delayed onset neurologic disease
Virology, 2007Co-Authors: Brian H. Bird, César G. Albariño, Stuart T. NicholAbstract:Abstract Rift Valley fever virus is a significant human and Veterinary Pathogen responsible for explosive outbreaks throughout Africa and the Arabian Peninsula. Severe acute disease in humans includes rapid onset hepatic disease and hemorrhagic fever or delayed onset encephalitis. A highly efficient reverse genetics system was developed which allowed generation of recombinant RVF viruses to assess the role of NSm protein in virulence in a rat model in which wild-type RVF virus strain ZH501 (wt-ZH501) results in 100% lethal hepatic disease 2–3 days post infection. While extensive genomic analysis indicates conservation of the NSm coding capability of diverse RVF viruses, and viruses deficient in NSs proteins are completely attenuated in vivo , comparison of wt-ZH501, a reverse genetics generated wt-ZH501 virus (R-ZH501), and R-ZH501 virus lacking the NSm proteins (R-ΔNSm-ZH501) demonstrated that the NSm proteins were nonessential for in vivo virulence and lethality. Surprisingly, while 44% of R-ΔNSm-ZH501 infected animals quickly developed lethal hepatic disease similar to wt- and R-ZH501, 17% developed delayed onset neurologic disease (lethargy, head tremors, and ataxia) at 13 days post infection. Such infections may provide the basis for study of both RVF acute hepatic disease and delayed onset encephalitic disease in humans.
Kwokyung Yuen - One of the best experts on this subject based on the ideXlab platform.
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complete genome sequence of the Veterinary Pathogen staphylococcus pseudintermedius strain hku10 03 isolated in a case of canine pyoderma
Journal of Bacteriology, 2011Co-Authors: Herman Tse, Hoi Wah Tsoi, Sze Pui Leung, Ian James Urquhart, Susanna K P Lau, Patrick C Y Woo, Kwokyung YuenAbstract:Staphylococcus pseudintermedius is a member of the coagulase-positive staphylococci and is the commonest cause of canine pyoderma. We report the first genome sequence of S. pseudintermedius, which shows the presence of numerous virulence factors akin to those of the related human Pathogen Staphylococcus aureus.
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genome announcements complete genome sequence of the Veterinary Pathogen staphylococcus pseudintermedius strain hku10 03 isolated in a case of canine pyoderma
2011Co-Authors: Herman Tse, Hoi Wah Tsoi, Sze Pui Leung, Ian James Urquhart, Susanna K P Lau, Patrick C Y Woo, Kwokyung YuenAbstract:strain HKU10-03 wassequenced on a GS FLX system (Roche Diagnostics, Basel,Switzerland), which produced approximately 260,000 readswith an approximate 37-fold coverage. This strain was firstisolated from the skin swab of a skin lesion swab of a dogsuffering from canine pyoderma. Genome assembly was per-formed using the Newbler assembler and produced 51 largecontigs (greater than 500 bp in size). Contig ordering wasperformed with the assistance of the OSlay software program(10), followed by gap closing and genome finishing by genomicPCR and DNA sequencing of the amplification products on anABI 3730xl sequencer (Applied Biosystems, California), simi-lar to the strategy employed for our previously sequenced
Paolo Fazii - One of the best experts on this subject based on the ideXlab platform.
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Methicillin-Resistant Staphylococcus pseudintermedius Infection in a Bone Marrow Transplant Recipient
Journal of Clinical Microbiology, 2013Co-Authors: Vincenzo Savini, Klaudia Polakowska, Giovanni Gherardi, Roberta Marrollo, Ennio Polilli, Daniela Barbarini, Białecka A, Andrzej Kasprowicz, Giovanni Di Bonaventura, Paolo FaziiAbstract:Staphylococcus pseudintermedius is a Veterinary Pathogen that has seldom been described as an agent of human disease. Features of this probably underreported coagulase-positive Staphylococcus species are depicted here through the description of a graft-versus-host disease-related wound infection caused by a multidrug-resistant strain.
