Abstract
Influenza virus typically alters protein glycosylation in order to escape immune pressure from hosts and hence to facilitate survival in different host environments. In this study, the patterns and conservation of glycosylation sites on HA and NA of influenza A/H1N1 viruses isolated from various hosts at different time periods were systematically analyzed, by employing a new strategy combining genome-based glycosylation site prediction and 3D modeling of glycoprotein structures, for elucidation of the modes and laws of glycosylation site alteration in the evolution of influenza A/H1N1 viruses. The results showed that influenza H1N1 viruses underwent different alterations of protein glycosylation in different hosts. Two alternative modes of glycosylation site alteration were involved in the evolution of human influenza virus: One was an increase in glycosylation site numbers, which mainly occurred with high frequency in the early stages of evolution. The other was a change in the positional conversion of the glycosylation sites, which was the dominating mode with relatively low frequency in the later evolutionary stages. The mechanisms and possibly biological functions of glycosylation site alteration for the evolution of influenza A/H1N1 viruses were also discussed. Importantly, the significant role of positional alteration of glycosylation sites in the host adaptation of influenza virus was elucidated. Although the results still need to be supported by experimental data, the information here may provide some constructive suggestions for research into the glycosylation of influenza viruses as well as even the design of surveillance and the production of viral vaccines.
Highlights
Influenza virus can cause occasional pandemics and seasonal epidemics in humans [1]
The great threat and high frequency of variation of influenza viruses make the study of their evolutionary mechanisms for host adaptation an urgent necessity in order to predict and prevent the outbreak of potential new influenza pandemics in the near future [2]
For the glycosylation site alteration on HA and NA of influenza A/H1N1 virus, though this analysis is hindered by the limited number of sequences available until 1995, the overall tendency was that a new mutant strain with positional conversion of glycosylation sites on HA and NA could more rapidly overtakes the original strain than a new mutant strain with simple acquisition of new glycosylation sites on HA and HA (Table 1 and 2)
Summary
Influenza virus can cause occasional pandemics and seasonal epidemics in humans [1]. The great threat and high frequency of variation of influenza viruses make the study of their evolutionary mechanisms for host adaptation an urgent necessity in order to predict and prevent the outbreak of potential new influenza pandemics in the near future [2]. Alteration of glycosylation site numbers on HA and NA in the evolution of human seasonal influenza viruses
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