Dityrosine Locked Prefusion F Protein A Path To A Protective RSV Vaccine

The Respiratory Syncytial Virus RSV poses a serious threat to newborn children the elderly and immuno compromised patients an effective vaccine has the potential to protect all vulnerable populations but such a protective vaccine has not yet been developed The RSV fusion F protein induces potent neutralizing antibodies NAbs that protect from infection the most potent of these NAbs bind only to its pre fusion conformation preF preF as a soluble immunogen elicits the most potently protective responses but use of recombinant soluble preF as an immunogen has been hindered by its instability Several groups have identified variants that stabilize F in its prefusion conformation but none have achieved a satisfactory degree of stability Avatar is developing a preF immunogen that is considerably more stable and that will provide potent long lasting and cost effective protection against RSV infection Avatar has developed a technology that introduces targeted zero length dityrosine DT crosslinks into fully folded native proteins preserving their structural integrity DT locking involves steps i expressing and purifying soluble F proteins with targeted conservative to Tyr substitutions and ii enzymatically crosslinking the complex in its pre fusion conformation DT bonds are used to lock together interactions between secondary and tertiary protein structures within the preF trimer that are beyond the reach of traditional protein engineering and can hence solve otherwise intractable protein engineering problems Avatarandapos s stabilized DT preF immunogen will thus provide the required stability for storage and distribution and thereby exceed the stability needed for successful product development furthermore DT preF will focus immune responses on potently neutralizing epitopes that are only displayed in the preF conformation As a result vaccination with DT preF will elicit potent and lasting protection against RSV Our goal is to develop an immunogen with very high stability half life andgt yr that elicits potent and protective Ab responses To accomplish this goal we will carry out the following Phase II Specific Aims I Make and test additional DT preF designs Introduce an additional crosslink at the base of the preF trimer Milestone novel DT preF molecules antigenically intact and have improved stability II Proteolytically remove the trimerization motif via engineered cleavage sites Milestone DT preF molecules are antigenically intact and stable lead and back up molecules are selected III Confirm prefusion conformation of the DTpreF immunogen MS and crystallographic analysis Milestones Mass spec of the lead and back up DT preF protein fragments shows DT bonds are formed at targeted positions and crystallographic analysis confirms DT preF proteins retain the preF conformation IV Demonstrate potency in animal models Immunogencity histopathology study in mice and cotton rats Milestones lead and back up DT preF generate high neutralizing titers and protection from challenge In Phase III we will manufacture DT preF under cGMP and perform pre clinical testing safety with a view toward filing an IND with the FDA There is currently no effective vaccine for RSV and each year RSV infects million children in the US and is the leading cause of infant hospitalizations Globally it accounts for of deaths in infants second only to malaria and in addition it poses a serious threat to the elderly and immuno compromised We propose to apply our proprietary protein engineering approach to the design of an RSV vaccine immunogen based on recombinant F fusion protein stabilized in its prefusion conformation that will trigger the production of antibodies in vaccinated individuals that will bind to and neutralize the virus when it enters the body