Human parainfluenza virus 3 (HPIV-3)

Human parainfluenza virus 3 (HPIV-3) is an enveloped, single-stranded, negative-sense RNA virus in the Paramyxoviridae family that primarily infects respiratory epithelial cells, causing acute upper and lower respiratory tract illnesses ranging from common colds to severe pneumonia, bronchiolitis, and croup, particularly in infants, young children, the elderly, and immunocompromised individuals. Its genome encodes six main structural proteins: nucleoprotein (N or NP), phosphoprotein (P), matrix protein (M), fusion glycoprotein (F), hemagglutinin-neuraminidase (HN), and large polymerase protein (L), which facilitate viral attachment via HN to sialic acid receptors, membrane fusion via F (often activated by host proteases like TMPRSS2), genome replication, transcription, and virion assembly. HPIV-3 replicates in the cytoplasm, leading to host cell damage, immune activation including interferon production, and symptoms like fever, cough, and dyspnea through mucosal inflammation and edema. No approved vaccines exist, but live attenuated candidates are in trials, and treatments rely on supportive care with off-label antivirals targeting entry or replication. The virus's L protein forms dimers essential for replication, offering potential drug design targets, while surface glycoproteins F and HN are key for inhibitors like DAS181 and BCX2798 under development. HPIV-3 circulates globally year-round, with high contagiousness via droplets, distinguishing it from influenza despite similar symptoms.

Other names

Parainfluenza-3 virushPIV3HPIV3Human parainfluenza virus type 3

Inhibition of viral replication (ribavirin); Cleavage of sialic acid receptors to prevent viral attachment (DAS181); Inhibition of hemagglutinin-neuraminidase (BCX2798); Interference with fusion protein function (VIQKI); Immune enhancement (alpha-interferon, thymosin)