Respiratory Syncytial Virus (RSV)
Respiratory Syncytial Virus (RSV) is a paramyxovirus, which unlike HIV or HRV has relatively little genetic variability and is present in only two major subtypes. Vaccine development has been a priority for over 50 years, but has met with little success so far. Especially an inactivated whole virus candidate has paradoxically increased mortality and disease severity, probably due to toxicity of immune complexes.
RSV has two major coat proteins (F and G). It has previously been demonstrated that virus entry is mediated by the F protein, which acts similar to influenza hemagglutinin. It has also been shown that neutralizing antibodies like the marketed mAb pavilizumab bind to and stabilize the pre-fusion form of the F protein and thereby prevent membrane fusion with the target cell. Vaccine development based on soluble full pre-fusion F protein has been difficult due to its inherent instability.
In developing its vaccine candidate VVX005, Viravaxx will also be applying the PCFiT technology. Peptide epitopes from the F protein, which are responsible for RSV infectivity, will be identified in studies with the multiplexed peptide array and included in appropriate fusion proteins.
Clinical efficacy both for infant and elderly protection and possibly therapeutic vaccination in elderly patients will be studied, including evaluation of maternal vaccination of pregnant females in order to achieve placental transfer of maternal blocking antibodies and protection of the infant in the first six months of life, when the immune system is still immature.