The maintenance of a Buy rating indicates a positive outlook on Prothena Corp by HC Wainwright & Co., suggesting confidence in the company's fundamentals or future prospects. However, the reduction in the price target from $90 to $84, while still indicating an upside potential, suggests a recalibration of expectations possibly due to market conditions, recent company performance, or other factors not specified in the article. This mixed signal could lead to short-term uncertainty among investors, potentially stabilizing the stock price as the market absorbs the new target.