Giuseppe
Emeritus
Replication of avian, human and swine influenza viruses in porcine respiratory explants and association with sialic acid distribution (BMC, abstract, edited)
Replication of avian, human and swine influenza viruses in porcine respiratory explants and association with sialic acid distribution
Sjouke GM Van Poucke, John M Nicholls, Hans J Nauwynck and Kristien Van Reeth
Virology Journal 2010, 7:38
doi:10.1186/1743-422X-7-38
Published: 16 February 2010
Abstract (provisional)
Background
Throughout the history of human influenza pandemics, pigs have been considered the most likely "mixing vessel" for reassortment between human and avian influenza viruses (AIVs). However, the replication efficiencies of influenza viruses from various hosts, as well as the expression of sialic acid (Sia) receptor variants in the entire porcine respiratory tract have never been studied in detail. Therefore, we established porcine nasal, tracheal, bronchial and lung explants, which cover the entire porcine respiratory tract with maximal similarity to the in vivo situation. Subsequently, we assessed virus yields of three porcine, two human and six AIVs in these explants. Since our results on virus replication were in disagreement with the previously reported presence of putative avian virus receptors in the trachea, we additionally studied the distribution of sialic acid receptors by means of lectin histochemistry. Human (Sia alfa2-6Gal) and avian virus receptors (Sia alfa2-3Gal) were identified with Sambucus Nigra and Maackia amurensis lectins respectively.
Results
Compared to swine and human influenza viruses, replication of the AIVs was limited in all cultures but most strikingly in nasal and tracheal organ cultures. Results from virus titrations were confirmed by quantification of infected cells using immunohistochemistry. By lectin histochemistry we found moderate to abundant expression of the human-like virus receptors in all explant systems but minimal binding of the lectins that identify avian-like receptors, especially in the nasal, tracheal and bronchial epithelium.
Conclusions
The species barrier that restricts the transmission of influenza viruses from one host to another remains preserved in our porcine respiratory explants. Therefore this system offers a valuable alternative to study virus and/or host properties required for adaptation or reassortment of influenza viruses. Our results indicate that, based on the expression of sialic acid receptors alone, the pig is unlikely to be a more appropriate mixing vessel for influenza viruses than humans. We conclude that too little is known on the exact mechanism and on predisposing factors for reassortment to assess the true role of the pig in the emergence of novel influenza viruses.
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<cite cite="http://www.virologyj.com/content/7/1/38">Abstract | Replication of avian, human and swine influenza viruses in porcine respiratory explants and association with sialic acid distribution</cite>Sjouke GM Van Poucke, John M Nicholls, Hans J Nauwynck and Kristien Van Reeth
Virology Journal 2010, 7:38
doi:10.1186/1743-422X-7-38
Published: 16 February 2010
Abstract (provisional)
Background
Throughout the history of human influenza pandemics, pigs have been considered the most likely "mixing vessel" for reassortment between human and avian influenza viruses (AIVs). However, the replication efficiencies of influenza viruses from various hosts, as well as the expression of sialic acid (Sia) receptor variants in the entire porcine respiratory tract have never been studied in detail. Therefore, we established porcine nasal, tracheal, bronchial and lung explants, which cover the entire porcine respiratory tract with maximal similarity to the in vivo situation. Subsequently, we assessed virus yields of three porcine, two human and six AIVs in these explants. Since our results on virus replication were in disagreement with the previously reported presence of putative avian virus receptors in the trachea, we additionally studied the distribution of sialic acid receptors by means of lectin histochemistry. Human (Sia alfa2-6Gal) and avian virus receptors (Sia alfa2-3Gal) were identified with Sambucus Nigra and Maackia amurensis lectins respectively.
Results
Compared to swine and human influenza viruses, replication of the AIVs was limited in all cultures but most strikingly in nasal and tracheal organ cultures. Results from virus titrations were confirmed by quantification of infected cells using immunohistochemistry. By lectin histochemistry we found moderate to abundant expression of the human-like virus receptors in all explant systems but minimal binding of the lectins that identify avian-like receptors, especially in the nasal, tracheal and bronchial epithelium.
Conclusions
The species barrier that restricts the transmission of influenza viruses from one host to another remains preserved in our porcine respiratory explants. Therefore this system offers a valuable alternative to study virus and/or host properties required for adaptation or reassortment of influenza viruses. Our results indicate that, based on the expression of sialic acid receptors alone, the pig is unlikely to be a more appropriate mixing vessel for influenza viruses than humans. We conclude that too little is known on the exact mechanism and on predisposing factors for reassortment to assess the true role of the pig in the emergence of novel influenza viruses.
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