Abstract
La Crosse encephalitis virus (LACV) is the second most frequently diagnosed arboviral cause of meningoencephalitis and the most common cause of pediatric viral encephalitis in the US. Multiple factors, including climate changes and invasive mosquito species adaptation contribute to the emerging spread of LACV in new areas. There is an expanding need for broader investigation on seroprevalence, development of novel antiviral drugs and vaccines for prevention of LACV infection. We pseudotyped replication-competent vesicular stomatitis virus (VSV) vectors with LACV surface glycoproteins using wild type (VSV-LACV) and attenuated (VSV-M51-LACV) backbones. Recombinant strains were tested as diagnostic tools in LACV serology and as potential live anti-LACV vaccine in vivo. The attenuated VSV-M51R-LACV vector was safe after direct intracranial inoculation in mice. Intraperitoneal immunization induced strong humoral response reaching average complete neutralization titer (VN(100%)) of 4640 in Balb/c and 2800 in interferon type I receptor knockout transgenic (Ifnarko-CD46Ge) mice respectively. Serum antibodies from vaccinated mice efficiently neutralized LACV with average titers between 229 and 2926 for the different LACV strains. We demonstrated that virus neutralization (VN) based on LACV-pseudotyped VSV is a valuable diagnostic assay for serodiagnostics of anti-LACV response in humans. VN titers in the range of 8-4096 were detected in sera from all individuals (n = 20) with confirmed infection. The assay also detected LACV-specific antibody response in cerebrospinal fluid of patients with CNS infection. VN was adapted for detection of neutralizing antibodies extracted from dried blood spots (DBS) samples with potential application in large scale LACV serologic surveillance. These data demonstrate that recombinant VSV-M51R-LACV is a valuable diagnostic tool as well as a promising live vaccine platform for immunoprophylaxis against LACV infection.