Multiple amino acid changes at the first glycosylation motif in NS1 protein of West Nile virus are necessary for complete attenuation for mouse neuroinvasiveness

► NS1N130A commonly reverted for the NS1130A/175A/207A virus in mice. ► Asparagine to serine/glutamine further attenuated the virus at the NS1130 site. ► Only NS1130-132QQA/175A/207A was highly attenuated in weanling and adult mice. ► Attenuated mutant viruses induced a protective immune response following lethal challenge.