The downgrade from Buy to Underperform represents a significant shift in sentiment from B of A Securities, likely due to concerns about AlloVir's future performance or market conditions. The substantial decrease in the price target from $17 to $1 is a strong indicator that the analyst expects the stock to perform poorly in the short term. This news is likely to negatively impact investor confidence and could lead to a decrease in AlloVir's stock price in the short term.