Inhibiting Human Parainfluenza Virus Infection by Preactivating the Cell Entry Mechanism

Area of Science:

• Virology
• Structural Biology
• Drug Discovery

Background:

• Paramyxoviruses, like human parainfluenza virus type 3 (HPIV3), infect cells via membrane fusion mediated by the hemagglutinin-neuraminidase (HN) and fusion (F) proteins.
• HN binds to host cell receptors, triggering conformational changes in F to enable viral entry.
• Premature activation of the F protein is a promising antiviral strategy, rendering the virus non-infectious by inducing a postfusion state before receptor engagement.

Purpose of the Study:

• To synthesize and characterize a more potent derivative of the antiviral compound CSC11, named CM9, targeting HPIV3.
• To develop novel conformation-specific antibodies against the HPIV3 F protein to validate antiviral compound efficacy.
• To explore CM9 and the new antibodies as tools for developing novel antiviral therapies against paramyxoviruses.

Main Methods:

• Systematic chemical modifications of CSC11 to create the derivative CM9.
• Assessing CM9's antiviral potency using plaque reduction, fusion inhibition, and binding avidity assays.
• Producing novel anti-HPIV3 F conformation-specific antibodies and utilizing them to confirm F protein transition to the postfusion state in the presence of CM9.

Main Results:

• The novel compound CM9 demonstrated enhanced potency in inhibiting HPIV3 infection compared to CSC11.
• CM9 effectively caused premature activation of the HPIV3 F protein via interaction with HN, preventing viral fusion.
• Newly developed conformation-specific antibodies confirmed the induction of the F protein's postfusion state by CM9.

Conclusions:

• CM9 represents a potent antiviral agent that functions by prematurely triggering the HPIV3 F protein, offering a new therapeutic avenue.
• The novel postfusion-specific antibodies are valuable tools for assessing the efficacy of antiviral compounds targeting viral fusion.
• The combined development of CM9 and these antibodies advances the understanding of HN-F interactions and supports the creation of effective paramyxovirus antivirals.