Selection pressures mainly depend on the interaction strength with the receptor vital for the entry into the target cell.
Viral infectivity depends on an expression level of the receptors that mediate the viral entry into target cells.
Surprisingly, in spite of the relative abundant expression of NA at the surface of influenza virions [13], a direct contribution of NA in the process of viral entry into target cells has never been clearly established.
Studies of individuals who were highly exposed but seronegative (HESN) for HIV infection led to the discovery that homozygosity for the Δ32 deletion mutation in the CCR5 gene prevents viral entry into target cells, and is associated with resistance to infection.
The precise mechanism of VacA entry into target cells is still divisive, reflected by the fact that several putative receptors have been described.
Reflecting the need for specific host cell molecules that facilitate viral entry into target cells, the tropism of HIV-1 is primarily governed by the expression of the entry receptor complex consisting of CD4 and CXCR4 or CCR5 on the surface of target cells.
Citing the fact that HD DVD players are also found in Best Buy, Circuit City and Wal-Mart (the only one that matters), a co-president of the HD DVD Promotional Group said that Sony's entry into Target isn't a cause for alarm.
Previous studies had shown that low endosomal pH is required for infection and cell-cell fusion mediated by Ebola virus GP [32], [33] and that low pH is required for optimal functioning of cathepsin B and L, which are important to the initial step of Ebola virus entry into target cells [34].
Thus, 2DLT induces a premature and irreversible collapse of the viral mousetrap, thereby preventing viral entry into target cells.
Uncoating of the viral core, which occurs following entry into target cell and concomitant with early steps of reverse transcription, is another key step in the viral life cycle.
