Molecular basis of Influenza A virulence is not fully understood. This study focuses on the Hemagglutinin (HA) protein since it is known to be a critical determinant of virulence. The experimental approach used was mouse adaptation. The prototype clinical isolate A/HK/1/68 (H3N2) was subjected to serial mouse to mouse passages. Following longitudinal and parallel studies 11 mouse adapted populations were generated. Sequence analysis of all 11 populations identified a total of 24 mutations within the HA gene. These mutations clustered in two areas within the 3 dimensional structure. One adaptive region resides within the HA1 while the other is located in the HA2 domain. Four of the mouse adapted HA mutations exhibited evidence of convergent evolution. Three of these mutations (P162L/S, Q210R and G218W/E) reside in HA1 while one mutation (N154S/K) is located in HA2. Recombinant viruses possessing convergent HA mutations exhibited altered receptor binding and pH of fusion. These mutations increased infection and replication within the mouse lung (in vivo) and/or mTECs (in vitro). However, different infection patterns were observed indicating that distinct alpha2,3 SA receptors might be present in the tracheal, bronchial and alveolar cells. In addition, adaptive mutations in HA1 as well as HA2 were associated with enhanced virulence. Certain mouse adapted mutations parallel changes observed in other virulent variants. This identifies them as putative virulence determinants. Hence, these mutations can serve as predictors of virulence.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/29979 |
| Date | January 2010 |
| Creators | Keleta, Liya |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 235 p. |
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