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In vitro and in vivo characterization of new swine-origin H1N1 influenza viruses.

Itoh Y, Shinya K, Kiso M, Watanabe T, Sakoda Y, Hatta M, Muramoto Y, Tamura D, Sakai-Tagawa Y, Noda T, Sakabe S, Imai M, Hatta Y, Watanabe S, Li C, Yamada S, Fujii K, Murakami S, Imai H, Kakugawa S, Ito M, Takano R, Iwatsuki-Horimoto K, Shimojima M, Horimoto T, Goto H, Takahashi K, Makino A, Ishigaki H, Nakayama M, Okamatsu M, Takahashi K, Warshauer D, Shult PA, Saito R, Suzuki H, Furuta Y, Yamashita M, Mitamura K, Nakano K, Nakamura M, Brockman-Schneider R, Mitamura H, Yamazaki M, Sugaya N, Suresh M, Ozawa M, Neumann G, Gern J, Kida H, Ogasawara K, Kawaoka Y - Nature (2009)

Bottom Line: On 11 June 2009 the World Health Organization declared that the infections caused by the new strain had reached pandemic proportion.In specific-pathogen-free miniature pigs, CA04 replicates without clinical symptoms.Finally, we show that CA04 is sensitive to approved and experimental antiviral drugs, suggesting that these compounds could function as a first line of defence against the recently declared S-OIV pandemic.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Shiga University of Medical Science, Ohtsu, Shiga 520-2192, Japan.

ABSTRACT
Influenza A viruses cause recurrent outbreaks at local or global scale with potentially severe consequences for human health and the global economy. Recently, a new strain of influenza A virus was detected that causes disease in and transmits among humans, probably owing to little or no pre-existing immunity to the new strain. On 11 June 2009 the World Health Organization declared that the infections caused by the new strain had reached pandemic proportion. Characterized as an influenza A virus of the H1N1 subtype, the genomic segments of the new strain were most closely related to swine viruses. Most human infections with swine-origin H1N1 influenza viruses (S-OIVs) seem to be mild; however, a substantial number of hospitalized individuals do not have underlying health issues, attesting to the pathogenic potential of S-OIVs. To achieve a better assessment of the risk posed by the new virus, we characterized one of the first US S-OIV isolates, A/California/04/09 (H1N1; hereafter referred to as CA04), as well as several other S-OIV isolates, in vitro and in vivo. In mice and ferrets, CA04 and other S-OIV isolates tested replicate more efficiently than a currently circulating human H1N1 virus. In addition, CA04 replicates efficiently in non-human primates, causes more severe pathological lesions in the lungs of infected mice, ferrets and non-human primates than a currently circulating human H1N1 virus, and transmits among ferrets. In specific-pathogen-free miniature pigs, CA04 replicates without clinical symptoms. The assessment of human sera from different age groups suggests that infection with human H1N1 viruses antigenically closely related to viruses circulating in 1918 confers neutralizing antibody activity to CA04. Finally, we show that CA04 is sensitive to approved and experimental antiviral drugs, suggesting that these compounds could function as a first line of defence against the recently declared S-OIV pandemic.

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Pathologic examination of the lungs of infected cynomolgus macaquesRepresentative pathologic images of CA04- (macaque #1, a-d), KUTK-4- (macaque #7, e-g), and mock- (h) infected lungs on day 3 pi. One or two sections per lung lobe were examined; representative findings are shown to depict the distribution of lesions in the sections (shown as cross sections placed next to illustrations of each lung lobe), with or without viral antigen, as follows: brown, severe lung lesion containing moderate to many viral antigen-positive cells; pink, mild lung lesions containing a few viral antigen-positive cells; blue, lung lesions with alveolar wall thickening, with remaining air spaces unaffected.
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Figure 1: Pathologic examination of the lungs of infected cynomolgus macaquesRepresentative pathologic images of CA04- (macaque #1, a-d), KUTK-4- (macaque #7, e-g), and mock- (h) infected lungs on day 3 pi. One or two sections per lung lobe were examined; representative findings are shown to depict the distribution of lesions in the sections (shown as cross sections placed next to illustrations of each lung lobe), with or without viral antigen, as follows: brown, severe lung lesion containing moderate to many viral antigen-positive cells; pink, mild lung lesions containing a few viral antigen-positive cells; blue, lung lesions with alveolar wall thickening, with remaining air spaces unaffected.

Mentions: Cynomolgus macaques (Macaca fascicularis) have been used to study highly pathogenic avian H5N1 viruses6,7 and the 1918 pandemic virus8. Infection of cynomolgus macaques with CA04 (see `Methods' section for detailed procedures) resulted in a more prominent increase in body temperature than infection with KUTK-4 (Supplementary Fig. S6). This difference might originate from the observed differences in virus titres (Table 1 and Supplementary Table 2). No remarkable difference in body weight loss was found between the two groups (data not shown). CA04 replicated efficiently in the lungs and other respiratory organs of infected animals, similar to highly pathogenic influenza viruses6,8 (Table 1). By contrast, conventional human influenza viruses are typically limited in their replicative ability in the lungs of infected primates6,8 (Table 1), although a seasonal H1N1 virus was isolated from one animal on day 7 pi. Pathologic examination revealed that CA04 caused more severe lung lesions than did KUTK-4 (Fig. 1 and Supplementary Fig. S7). On day 3 pi with CA04, alveolar spaces were occupied by edematous exudate and inflammatory infiltrates (Fig. 1a); severe thickening of alveolar walls was also observed (Fig. 1b). Viral antigen-positive cells were distributed in the inflammatory lesions, and many of these cells were elongated with thin cytoplasm and hemming around the alveolar wall, indicating type I pneumocytes (Fig. 1c). In addition to type I pneumocytes, CA04 viral antigens were also detected in considerable numbers of cuboidal, cytokeratin-positive cells, hence identified as type II pneumocytes (Fig. 1d, and Supplementary Fig. S8), as has been reported for highly pathogenic avian H5N1 influenza viruses6. Upon infection with KUTK-4, large sections of infected lungs showed thickening of the alveolar wall on day 3 pi (Fig. 1e). Although the infiltration of inflammatory cells was prominent at the alveolar wall (Fig. 1f), viral antigens were sparse and detected in type I (but not type II) pneumocytes (Fig. 1g). By contrast, the lungs of noninfected animals show clear alveolar spaces (Fig. 1h).


In vitro and in vivo characterization of new swine-origin H1N1 influenza viruses.

Itoh Y, Shinya K, Kiso M, Watanabe T, Sakoda Y, Hatta M, Muramoto Y, Tamura D, Sakai-Tagawa Y, Noda T, Sakabe S, Imai M, Hatta Y, Watanabe S, Li C, Yamada S, Fujii K, Murakami S, Imai H, Kakugawa S, Ito M, Takano R, Iwatsuki-Horimoto K, Shimojima M, Horimoto T, Goto H, Takahashi K, Makino A, Ishigaki H, Nakayama M, Okamatsu M, Takahashi K, Warshauer D, Shult PA, Saito R, Suzuki H, Furuta Y, Yamashita M, Mitamura K, Nakano K, Nakamura M, Brockman-Schneider R, Mitamura H, Yamazaki M, Sugaya N, Suresh M, Ozawa M, Neumann G, Gern J, Kida H, Ogasawara K, Kawaoka Y - Nature (2009)

Pathologic examination of the lungs of infected cynomolgus macaquesRepresentative pathologic images of CA04- (macaque #1, a-d), KUTK-4- (macaque #7, e-g), and mock- (h) infected lungs on day 3 pi. One or two sections per lung lobe were examined; representative findings are shown to depict the distribution of lesions in the sections (shown as cross sections placed next to illustrations of each lung lobe), with or without viral antigen, as follows: brown, severe lung lesion containing moderate to many viral antigen-positive cells; pink, mild lung lesions containing a few viral antigen-positive cells; blue, lung lesions with alveolar wall thickening, with remaining air spaces unaffected.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2748827&req=5

Figure 1: Pathologic examination of the lungs of infected cynomolgus macaquesRepresentative pathologic images of CA04- (macaque #1, a-d), KUTK-4- (macaque #7, e-g), and mock- (h) infected lungs on day 3 pi. One or two sections per lung lobe were examined; representative findings are shown to depict the distribution of lesions in the sections (shown as cross sections placed next to illustrations of each lung lobe), with or without viral antigen, as follows: brown, severe lung lesion containing moderate to many viral antigen-positive cells; pink, mild lung lesions containing a few viral antigen-positive cells; blue, lung lesions with alveolar wall thickening, with remaining air spaces unaffected.
Mentions: Cynomolgus macaques (Macaca fascicularis) have been used to study highly pathogenic avian H5N1 viruses6,7 and the 1918 pandemic virus8. Infection of cynomolgus macaques with CA04 (see `Methods' section for detailed procedures) resulted in a more prominent increase in body temperature than infection with KUTK-4 (Supplementary Fig. S6). This difference might originate from the observed differences in virus titres (Table 1 and Supplementary Table 2). No remarkable difference in body weight loss was found between the two groups (data not shown). CA04 replicated efficiently in the lungs and other respiratory organs of infected animals, similar to highly pathogenic influenza viruses6,8 (Table 1). By contrast, conventional human influenza viruses are typically limited in their replicative ability in the lungs of infected primates6,8 (Table 1), although a seasonal H1N1 virus was isolated from one animal on day 7 pi. Pathologic examination revealed that CA04 caused more severe lung lesions than did KUTK-4 (Fig. 1 and Supplementary Fig. S7). On day 3 pi with CA04, alveolar spaces were occupied by edematous exudate and inflammatory infiltrates (Fig. 1a); severe thickening of alveolar walls was also observed (Fig. 1b). Viral antigen-positive cells were distributed in the inflammatory lesions, and many of these cells were elongated with thin cytoplasm and hemming around the alveolar wall, indicating type I pneumocytes (Fig. 1c). In addition to type I pneumocytes, CA04 viral antigens were also detected in considerable numbers of cuboidal, cytokeratin-positive cells, hence identified as type II pneumocytes (Fig. 1d, and Supplementary Fig. S8), as has been reported for highly pathogenic avian H5N1 influenza viruses6. Upon infection with KUTK-4, large sections of infected lungs showed thickening of the alveolar wall on day 3 pi (Fig. 1e). Although the infiltration of inflammatory cells was prominent at the alveolar wall (Fig. 1f), viral antigens were sparse and detected in type I (but not type II) pneumocytes (Fig. 1g). By contrast, the lungs of noninfected animals show clear alveolar spaces (Fig. 1h).

Bottom Line: On 11 June 2009 the World Health Organization declared that the infections caused by the new strain had reached pandemic proportion.In specific-pathogen-free miniature pigs, CA04 replicates without clinical symptoms.Finally, we show that CA04 is sensitive to approved and experimental antiviral drugs, suggesting that these compounds could function as a first line of defence against the recently declared S-OIV pandemic.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Shiga University of Medical Science, Ohtsu, Shiga 520-2192, Japan.

ABSTRACT
Influenza A viruses cause recurrent outbreaks at local or global scale with potentially severe consequences for human health and the global economy. Recently, a new strain of influenza A virus was detected that causes disease in and transmits among humans, probably owing to little or no pre-existing immunity to the new strain. On 11 June 2009 the World Health Organization declared that the infections caused by the new strain had reached pandemic proportion. Characterized as an influenza A virus of the H1N1 subtype, the genomic segments of the new strain were most closely related to swine viruses. Most human infections with swine-origin H1N1 influenza viruses (S-OIVs) seem to be mild; however, a substantial number of hospitalized individuals do not have underlying health issues, attesting to the pathogenic potential of S-OIVs. To achieve a better assessment of the risk posed by the new virus, we characterized one of the first US S-OIV isolates, A/California/04/09 (H1N1; hereafter referred to as CA04), as well as several other S-OIV isolates, in vitro and in vivo. In mice and ferrets, CA04 and other S-OIV isolates tested replicate more efficiently than a currently circulating human H1N1 virus. In addition, CA04 replicates efficiently in non-human primates, causes more severe pathological lesions in the lungs of infected mice, ferrets and non-human primates than a currently circulating human H1N1 virus, and transmits among ferrets. In specific-pathogen-free miniature pigs, CA04 replicates without clinical symptoms. The assessment of human sera from different age groups suggests that infection with human H1N1 viruses antigenically closely related to viruses circulating in 1918 confers neutralizing antibody activity to CA04. Finally, we show that CA04 is sensitive to approved and experimental antiviral drugs, suggesting that these compounds could function as a first line of defence against the recently declared S-OIV pandemic.

Show MeSH
Related in: MedlinePlus