• Type: Live, attenuated vaccine
• Status: Research
• Host Species for Licensed Use: None
• Antigen: Genetic backbone and nonstructural protein genes from Sindbis virus (SINV), Structural protein genes from a North American (SIN/NAEEEV) strain of EEEV. (Roy et al., 2013)
• Immunization Route: subcutaneous injection
• Description: A chimeric Sindbis-based vaccine protects cynomolgus macaques against a lethal aerosol challenge of eastern equine encephalitis virus. (Roy et al., 2013)

Macaque Response

• Vaccination Protocol: In the first study, animals were vaccinated with SIN/NAEEEV (n=6), SIN/SAEEEV (n=6), or PBS diluent (n=4). In the second study, cohorts were vaccinated with either SIN/NAEEEV (n=5) or PBS (n=2). All animals were vaccinated subcutaneously (SC) in the upper deltoid with a single inoculation of either saline or 5.0 log10 PFU of vaccine a volume of 100 μl. (Roy et al., 2013)
• Immune Response: Five of 6 macaques (83%) vaccinated with SIN/NAEEEV in the first study developed of neutralizing antibodies (Abs), first detected on day 12 post vaccination. Neutralizing Abs remained at initial levels or decreased slightly in the majority of the animals by day 24 or 45 post vaccination. Antibody responses in vaccinated animals from the second experiment, assayed on day 66 after vaccination, were slightly lower on average. (Roy et al., 2013)
• Challenge Protocol: On either day 45 (study 1) or 66 (study 2) after vaccination, anesthetized macaques were challenged with virulent EEEV strain FL93-939 aerosols using a 16 liter head-only dynamic inhalation exposure system. (Roy et al., 2013)
• Efficacy: The SIN/NAEEEV vaccine provided highly significant (p=0.0023) protection from fatal disease (figure 1), with 9 of the 11 animals (82%) surviving for 21 days until the study was terminated. Animals receiving the SIN/SAEEEV were not significantly protected, with only one of the six (17%) surviving challenge. All (6/6) animals in the sham-vaccinated cohort died from encephalitis. Protected animals exhibited minimal changes in temperature and cardiovascular rhythm, whereas unprotected animals showed profound hyperthermia and changes in heart rate post-exposure. Acute inflammation and neuronal necrosis were consistent with EEEV-induced encephalitis in unprotected animals, whereas no encephalitis-related histopathologic changes were observed in the SIN/NAEEEV-vaccinated animals. (Roy et al., 2013)