RESUMO
Two novel influenza A virus-like genomes were detected in fruit bats in Central and South America. However, the biological properties of these bat-derived influenza viruses (BatIVs) are still largely unknown since infectious viral particles have never been isolated from the infected host species. In this study, a reverse genetics approach was used to generate infectious BatIV particles entirely from plasmids encoding full-length sequences in eight gene segments. We inoculated BatIV particles into various cell cultures including bat-derived cell lines and found that BatIVs infected particular bat-derived cells efficiently but not the other cell lines tested. Reassortant viruses between the two BatIVs were also successfully generated and their replication in the susceptible bat cell lines was confirmed. These findings suggest a limited host range and reassortment potential of BatIVs in nature, providing fundamental information for understanding of the ecology of BatIVs.
Assuntos
Quirópteros/virologia , Vírus da Influenza A , Infecções por Orthomyxoviridae/virologia , Vírus Reordenados , Animais , Linhagem Celular , Chlorocebus aethiops , Cães , Especificidade de Hospedeiro , Humanos , Vírus da Influenza A/isolamento & purificação , Vírus da Influenza A/patogenicidade , Vírus da Influenza A/fisiologia , Codorniz , Vírus Reordenados/isolamento & purificação , Vírus Reordenados/patogenicidade , Vírus Reordenados/fisiologia , América do Sul , Replicação ViralRESUMO
Novel H1N2 and H3N2 swine influenza A viruses (IAVs) were identified in commercial farms in Chile. These viruses contained H1, H3 and N2 sequences, genetically divergent from IAVs described worldwide, associated with pandemic internal genes. Guinea pigs were used as human surrogate to evaluate the infection dynamics of these reassortant viruses, compared with a pandemic H1N1 virus. All viruses replicated and were shed in the upper respiratory tract without prior adaptation although H1N2 viruses showed the highest shedding titers. This could have public health importance, emphasizing the need to carry out further studies to evaluate the zoonotic potential of these viruses.
Assuntos
Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Vírus da Influenza A Subtipo H1N2/fisiologia , Vírus da Influenza A Subtipo H3N2/fisiologia , Infecções por Orthomyxoviridae/veterinária , Animais , Cobaias , Vírus da Influenza A Subtipo H1N2/genética , Vírus da Influenza A Subtipo H3N2/genética , Infecções por Orthomyxoviridae/virologia , Filogenia , Vírus Reordenados/genética , Vírus Reordenados/fisiologia , Análise de Sequência de RNA/veterináriaAssuntos
Vírus da Influenza A Subtipo H1N1/fisiologia , Influenza Humana/mortalidade , Pandemias , Vírus Reordenados/fisiologia , Animais , Causalidade , Temperatura Baixa , Reservatórios de Doenças , História do Século XVIII , História do Século XIX , História do Século XX , História do Século XXI , História Medieval , Humanos , Influenza Humana/etiologia , Influenza Humana/história , Influenza Humana/virologia , Pandemias/história , Aves Domésticas/virologia , Estações do Ano , Suínos/virologiaRESUMO
UNLABELLED: The 2009 H1N1 lineage represented the first detection of a novel, highly transmissible influenza A virus genotype: six gene segments originated from the North American triple-reassortant swine lineage, and two segments, NA and M, derived from the Eurasian avian-like swine lineage. As neither parental lineage transmits efficiently between humans, the adaptations and mechanisms underlying the pandemic spread of the swine-origin 2009 strain are not clear. To help identify determinants of transmission, we used reverse genetics to introduce gene segments of an early pandemic isolate, A/Netherlands/602/2009 [H1N1] (NL602), into the background of A/Puerto Rico/8/1934 [H1N1] (PR8) and evaluated the resultant viruses in a guinea pig transmission model. Whereas the NL602 virus spread efficiently, the PR8 virus did not transmit. Swapping of the HA, NA, and M segments of NL602 into the PR8 background yielded a virus with indistinguishable contact transmissibility to the wild-type pandemic strain. Consistent with earlier reports, the pandemic M segment alone accounted for much of the improvement in transmission. To aid in understanding how the M segment might affect transmission, we evaluated neuraminidase activity and virion morphology of reassortant viruses. Transmission was found to correlate with higher neuraminidase activity and a more filamentous morphology. Importantly, we found that introduction of the pandemic M segment alone resulted in an increase in the neuraminidase activity of two pairs of otherwise isogenic PR8-based viruses. Thus, our data demonstrate the surprising result that functions encoded by the influenza A virus M segment impact neuraminidase activity and, perhaps through this mechanism, have a potent effect on transmissibility. IMPORTANCE: Our work uncovers a previously unappreciated mechanism through which the influenza A virus M segment can alter the receptor-destroying activity of an influenza virus. Concomitant with changes to neuraminidase activity, the M segment impacts the morphology of the influenza A virion and transmissibility of the virus in the guinea pig model. We suggest that changes in NA activity underlie the ability of the influenza M segment to influence virus transmissibility. Furthermore, we show that coadapted M, NA, and HA segments are required to provide optimal transmissibility to an influenza virus. The M-NA functional interaction we describe appears to underlie the prominent role of the 2009 pandemic M segment in supporting efficient transmission and may be a highly important means by which influenza A viruses restore HA/NA balance following reassortment or transfer to new host environments.
Assuntos
Vírus da Influenza A Subtipo H1N1/genética , Vírus da Influenza A Subtipo H1N1/fisiologia , Neuraminidase/metabolismo , Infecções por Orthomyxoviridae/transmissão , Vírus Reordenados/genética , Vírus Reordenados/fisiologia , Proteínas da Matriz Viral/metabolismo , Proteínas Virais/metabolismo , Animais , Modelos Animais de Doenças , Feminino , Cobaias , Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Glicoproteínas de Hemaglutininação de Vírus da Influenza/metabolismo , Vírus da Influenza A Subtipo H1N1/isolamento & purificação , Vírus da Influenza A Subtipo H1N1/ultraestrutura , Países Baixos , Neuraminidase/genética , Infecções por Orthomyxoviridae/virologia , Porto Rico , Genética Reversa , Proteínas da Matriz Viral/genética , Proteínas Virais/genética , Vírion/ultraestruturaRESUMO
In this report, we describe the occurrence of two novel swine influenza viruses (SIVs) in pigs in Argentina. These viruses are the result of two independent reassortment events between the H1N1 pandemic influenza virus (H1N1pdm) and human-like SIVs, showing the constant evolution of influenza viruses at the human-swine interface and the potential health risk of H1N1pdm as it appears to be maintained in the swine population. It must be noted that because of the lack of information regarding the circulation of SIVs in South America, we cannot discard the possibility that ancestors of the H1N1pdm or other SIVs have been present in this part of the world. More importantly, these findings suggest an ever-expanding geographic range of potential epicenters of influenza emergence with public health risks.
Assuntos
Vírus da Influenza A Subtipo H1N1/isolamento & purificação , Infecções por Orthomyxoviridae/veterinária , Vírus Reordenados/isolamento & purificação , Doenças dos Suínos/virologia , Animais , Argentina , Vírus da Influenza A Subtipo H1N1/classificação , Vírus da Influenza A Subtipo H1N1/genética , Vírus da Influenza A Subtipo H1N1/fisiologia , Infecções por Orthomyxoviridae/virologia , Pandemias , Vírus Reordenados/classificação , Vírus Reordenados/genética , Vírus Reordenados/fisiologia , SuínosRESUMO
BACKGROUND: Cotton blue disease (CBD), an important global cotton crop pathology responsible for major economic losses, is prevalent in the major cotton-producing states of Brazil. Typical CBD symptoms include stunting due to internodal shortening, leaf rolling, intense green foliage, and yellowing veins. Atypical CBD symptoms, including reddish and withered leaves, were also observed in Brazilian cotton fields in 2007. Recently, a Polerovirus named Cotton leafroll dwarf virus (CLRDV) was shown to be associated with CBD. RESULTS: To understand the distribution and genetic diversity of CLRDV in Brazil, we analyzed 23 CBD-symptomatic plants from susceptible cotton varieties originating from five of the six most important cotton-growing states, from 2004-2007. Here, we report on CLRDV diversity in plants with typical or atypical CBD symptoms by comparing viral coat protein, RNA polymerase (RdRp), and intergenic region genomic sequences. CONCLUSION: The virus had a widespread distribution with a low genetic diversity; however, three divergent isolates were associated with atypical CBD symptoms. These divergent isolates had a CLRDV-related coat protein but a distinct RdRp sequence, and probably arose from recombination events. Based on the taxonomic rules for the family Luteoviridae, we propose that these three isolates represent isolates of a new species in the genus Polerovirus.
Assuntos
Gossypium/virologia , Luteoviridae/fisiologia , Doenças das Plantas/virologia , Vírus de Plantas/fisiologia , Vírus Reordenados/fisiologia , Sequência de Bases , Brasil , Luteoviridae/genética , Luteoviridae/isolamento & purificação , Dados de Sequência Molecular , Filogenia , Vírus de Plantas/genética , Vírus de Plantas/isolamento & purificação , Vírus Reordenados/genética , Vírus Reordenados/isolamento & purificação , Alinhamento de SequênciaRESUMO
The infection of epithelial cells by some animal rotavirus strains requires the presence of sialic acid (SA) on the cell surface. Recently, we isolated rhesus rotavirus variants, named nar, whose infectivity, like that of human rotaviruses, is not dependent on SA. In this work, we have determined the binding properties of these SA-dependent and -independent rotavirus strains to MA104 cells. The half-time of attachment of the SA-dependent porcine rotavirus YM and reassortant virus DS1xRRV was found to be about 10 times longer in neuraminidase-treated cells than in untreated cells. On the other hand, human rotaviruses Wa and DS1, and the variant nar3, bound to cells two to three times more rapidly in the absence of SA. To investigate whether the SA-independent cellular structure recognized by the variant and human rotaviruses was the same, we used an infection assay designed to detect competition for cell surface molecules at both attachment and post-attachment steps. In this assay, human rotavirus Wa efficiently competed the infectivity of YM in untreated cells and that of the variant nar3 in untreated, as well as neuraminidase-treated, cells. This competition was nonreciprocal, since YM and nar3 did not compete, but rather increased three- to fivefold the infectivity of Wa. In contrast, a two-direction competition between the variant nar3 and DS1xRRV was found. Similar results were obtained when psoralen-inactivated viruses were used as competitors, indicating that the competition observed was during the early stages of infection. Altogether, these results suggest the existence of multiple interactions between rotaviruses and the cell surface and revealed the existence of common steps during the entry of human and animal rotavirus strains.