This is a clinical study evaluating the safety, tolerability, pharmacokinetic (PK) characteristics and immunogenicity of HH-120 nasal spray in healthy subjects. This study is divided into two parts: Part A is of open-label design and mainly aims to assess the local distribution and PK in nasal cavity of HH-120 nasal spray, subjects from 10 cohorts are sequentially enrolled to perform either nasal endoscopic examination or nasal/ nasopharyngeal samples collection at different time points post administration. Part B mainly aims to assess the safety, systematic pharmacokinetic and immunogenicity after multiple dosing of HH-120 nasal spray, subjects are randomly assigned (3:1) to HH-120 and placebo groups.