The study of human rhinovirus 14 (HRV14) capsid dynamics
Human rhinovirus 14 is a member of picornavirus family and belongs to the rhinovirus genus that includes several serotypes causing common cold. Capsid stability plays an important role in the viral infection process. Hypothetical ‘pocket factors’ have been suggested to play an important role by providing transient stability to the members of picornavirus family. Interestingly, anti-viral WIN compounds that bind in the same hydrophobic pocket region as the ‘pocket factors’ inhibit capsid uncoating. Further, capsid-breathing experiments clearly demonstrated the importance of the empty pocket to facilitate capsid dynamics that lead to uncoating. To better understand the relevance of the hypothetical ‘pocket factors’ and to study the effect of filling the hydrophobic pocket on capsid breathing, HRV14 mutants, with mutations in (HRV14/V1188M/C1199W, HRV14/V1188M, and HRV14/C1199W) and around (HRV14/S1223G) the hydrophobic pocket region have been studied. Mutations that fill the hydrophobic pocket, block binding of the WIN compounds and hence block the binding of pocket factors, are viable and behave as wild type virus. They provide evidence suggesting that pocket factors are not essential in the viral life cycle. These results are supported by the studies on HRV14/S1223G to which WIN compounds bind without affecting infectivity. Transient and reversible exposure of the N-termini of VP1 and VP4 has been shown from the capsid breathing studies. However, the site of protrusion of these termini from the capsid is not known. Towards this end, antibodies against the peptides representing these termini have been raised and their ability to bind and neutralize HRV14 infectivity studied. VP4 antiserum shows the ability to form complexes with the virions and also demonstrates a dose and time dependent neutralization of HRV14 infectivity. Furthermore, anti-VP4 serum cross-reacts with other rhinovirus serotypes, HRV16, HRV3 and HRV29. Sequence analysis shows a high degree of sequence conservation in VP4 peptide among all the >100 serotypes, suggesting the possibility of using VP4 to develop a peptide based vaccine against rhinoviruses. Using an alternate approach, complexes of monomaleimido nanogold bound to N-termini of VP1 and VP4, locking the virus particle in an intermediate state of ‘breathing’ have been obtained. Preliminary reconstruction of this complex suggests two possible sites on the capsid from where these termini exit.
Smith, Purdue University.
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