Purpose: This study aimed to (1) determine the effect of blueberry juice (BJ) and blueberry proanthocyanidins (BB-PAC) on the infectivity of HAV at 37ºC over 24h; (2) understand the mode of action of BB-PAC on viral adsorption and viral replication; and (3) determine viral structural changes after BB-PAC treatment using transmission electron microscopy (TEM).
Methods: HAV at ~ 5 log PFU/ml was mixed with equal volumes of BJ (pH=2.8), neutralized BJ (pH=7), BB-PAC at 1, 2, or 5 mg/ml, phosphate buffered saline (PBS, pH 7.2), or malic acid (pH=3) for up to 24h at 37ºC. Treated viruses were serially diluted and plaque assayed in duplicate using three replications, and recovered titers were statistically analyzed. Pre-infection and post-infection BB-PAC treatments of host cells were carried out to determine effects on viral adsorption or replication, respectively. TEM analysis was used to determine treatment effects on virus structure.
Results: HAV titers were reduced to undetectable levels after 30 min with 2 and 5 mg/ml BB-PAC, to undetectable levels after 3h with 1 mg/ml BB-PAC, and by 2.01 ± 0.08 log PFU/ml after 24h with BJ. BB-PAC at 0.5 mg/ml did not show any effect on HAV replication and adsorption. Malic acid (pH control) did not cause any significant titer reduction after 24h. TEM revealed structural damage of HAV particles.
Significance: BB-PAC is effective in decreasing HAV infectivity. BB-PAC can damage the viral capsid and thus prevent host-cell entry. Further studies that incorporate BB-PAC in food systems are needed for its application to prevent HAV transmission/outbreaks.