The Western Equine Encephalitis Lyophilized, Inactivated Vaccine: An Update on Safety and Immunogenicity.

Background: Western Equine Encephalitis (WEE) is a naturally acquired infection and potentially devastating bioweapon, with no specific human countermeasures. An experimental inactivated Western Equine Encephalitis Vaccine (WEEV; WEE TSI-GSD 210) has been used under an IND (investigational New Drug) protocol at the United States Army Medical Research Institute of Infectious Diseases (USAMRIID) since 1976. Methods: Over 24 years from 1987 to 2011, 876 subjects received 3 primary vaccine doses under 3 studies with 1,537 booster doses administered (FY87-8, phase 2, laboratory workers, vaccine lots 1-81-1, 1-81-2, and 2-1-91; FY99-12, phase 2 laboratory workers, lot 2-1-91; and FY09-02, phase 1 healthy volunteer, lot 3-1-92). Post-vaccination safety and immunogenicity [plaque reduction neutralization test 80% (PRNT80) > 1:40] were analyzed. Results: Overall PRNT80 response to the primary series in FY87-8 was 42% (326/770) but dropped to 16% (14/87) in FY99-12, prompting study FY09-02, which achieved 89% (17/19). The first booster response rate was 68% (814/1194) in FY87-8, 53% (171/324) in FY99-12, and 100% (10/10) in FY09-02. The majority of definitely related adverse reactions (AEs) were mild and local with no definitely related serious AEs. No laboratory acquired WEE infection was documented during this period despite 4 reported exposures in vaccinated subjects. Conclusion: The TSI-GSD 210 WEE vaccine was immunogenic, safe and well tolerated. Use of this vaccine could be considered in an emergency setting. Despite decades of safe and effective use under IND, full licensure is not planned due to manufacturing constraints, and a strategic decision to develop alternatives. Clinical Trial Registration: https://clinicaltrials.gov/, identifier NCT01159561.

Protocolo del Sistema Nacional de Vigilancia Epidemiológica: enfermedades zoonóticas. No. 08 / Protocol of the National Epidemiological Surveillance System: zoonotic diseases. No. 08

Estos protocolos están dirigido a personal médico, paramédico y otros profesionales que realizan acciones gerenciales y operativas de vigilancia epidemiológica en los servicios de salud del país, y están divididos en varios tomos para dar a conocer y actualizar la identificación y medidas de control para diversos padecimientos a fin de continuar con el mejoramiento de las capacidades técnicas de los trabajadores de salud, que permita planificar la prestación de servicios con decisiones partiendo de un enfoque epidemiológico comprobado, para responder a los cambios de tendencias epidemiológicas y con ello contribuir al fortalecimiento de prácticas asertivas de la salud pública de nuestro país.

Immune interference in the setting of same-day administration of two similar inactivated alphavirus vaccines: eastern equine and western equine encephalitis.

We compared the effect on primary vaccination plaque-reduction neutralization 80% titers (PRNT80) responses of same-day administration (at different injection sites) of two similar investigational inactivated alphavirus vaccines, eastern equine encephalitis (EEE) vaccine (TSI-GSD 104) and western equine encephalitis (WEE) vaccine (TSI-GSD 210) to separate administration. Overall, primary response rate for EEE vaccine was 524/796 (66%) and overall primary response rate for WEE vaccine was 291/695 (42%). EEE vaccine same-day administration yielded a 59% response rate and a responder geometric mean titer (GMT)=89 while separate administration yielded a response rate of 69% and a responder GMT=119. WEE vaccine same-day administration yielded a 30% response rate and a responder GMT=53 while separate administration yielded a response rate of 54% and a responder GMT=79. EEE response rates for same-day administration (group A) vs. non-same-day administration (group B) were significantly affected by gender. A logistic regression model predicting response to EEE comparing group B to group A for females yielded an OR=4.10 (95% CL 1.97-8.55; p=.0002) and for males yielded an OR=1.25 (95% CL 0.76-2.07; p=.3768). WEE response rates for same-day administration vs. non-same-day administration were independent of gender. A logistic regression model predicting response to WEE comparing group B to group A yielded an OR=2.14 (95% CL 1.22-3.73; p=.0077). We report immune interference occurring with same-day administration of two completely separate formalin inactivated viral vaccines in humans. These findings combined with the findings of others regarding immune interference would argue for a renewed emphasis on studying the immunological mechanisms of induction of inactivated viral vaccine protection.

Immunological evaluation of Escherichia coli expressed E2 protein of Western equine encephalitis virus.

The Western equine encephalitis virus (WEEV) is a potential Biological Warfare (BW) agent. The WEEV is endemic in western Canada and has caused epidemics of "sleeping sickness" with a mortality rate of 7-9%. The E2 glycoprotein is a structural component of the WEEV and elicits production of neutralizing antibodies against the virus following an infection event. The envelope glycoprotein E2 is considered as the major target protein for the development of vaccines because it includes epitopes that elicit neutralizing antibodies. This report describes the successful cloning of the E2 gene of WEEV and expression in Escherichia coli as inclusion bodies. The inclusion bodies were successfully solubilized, refolded and the immunogenicity of this non-glycosylated protein was assessed in BALB/c mice. Recombinant E2 (rE2) protein was specifically and strongly recognized by inactivated WEEV-immunized mice serum sample on ELISA, suggesting that E. coli derived rE2 protein retained at least some functional characteristics of its native conformation. The immunogenicity of the refolded rE2 protein was demonstrated by strong humoral and cell mediated immune (CMI) responses in rE2-immunized BALB/c mice. The current study also demonstrated that rE2-immunized mice could be partially protected from lethal challenge of WEEV.

Complete protection of mice against a lethal dose challenge of western equine encephalitis virus after immunization with an adenovirus-vectored vaccine.

Western equine encephalitis virus (WEEV) is an important pathogen for both humans and equines. The virus is also listed as a bioterrorism agent due to its ability for aerosol transmission with high mortality. No commercial vaccines or antiviral drugs are available for the prevention and treatment of WEEV infection in humans. In this paper, we constructed a recombinant WEEV vaccine, designated as Ad5-WEEV, using a replication defective, human adenovirus serotype 5 (HAd5) as a delivery vector. Ad5-WEEV contains the E3-E2-6K-E1 structural protein gene of the 71V-1658 strain of WEEV and the E1 and E2 proteins were synthesized in cells inoculated with Ad5-WEEV. After intramuscular immunization of mice with two doses of Ad5-WEEV, neutralizing antibodies against WEEV were generated and the mice were completely protected from a lethal dose challenge of 71V-1658. In addition, we showed that passive transfer of serum from the Ad5-WEEV-immunized mice could partially control WEEV infection. These results demonstrate that HAd5 vectors are promising for WEEV vaccine development.

Evaluation of a Western Equine Encephalitis recombinant E1 protein for protective immunity and diagnostics.

The E1 and E2 glycoproteins of Western Equine Encephalitis (WEE) are candidate antigens for WEE subunit vaccine development. We have cloned the E1 gene of WEE virus and expressed it in Escherichia coli as inclusion bodies. The inclusion bodies were successfully solubilised, refolded and the immunogenicity of this unglycosylated protein was assessed in mice. Immunization of mice with recombinant E1 protein generated both humoral and cell-mediated immune responses, indicating the recombinant E1 protein is immunogenic. Challenge of E1-immunized mice with live WEE virus demonstrated little or no protection from this E. coli-derived non-glycosylated subunit.

California state Mosquito-Borne Virus Surveillance and Response Plan: a retrospective evaluation using conditional simulations.

The California Mosquito-Borne Virus Surveillance and Response Plan recently was developed to provide a semi-quantitative means for assessing risk for western equine encephalomyelitis (WEE) or St. Louis encephalitis (SLE) viruses and to provide intervention guidelines for mosquito control and public health agencies during periods of heightened risk for human infection. West Nile virus recently has arrived in California, and the response plan also will provide a baseline for assessing the risk for human and equine infection with this virus. In the response plan, overall risk is calculated by averaging risk due to 1) environmental conditions, 2) adult mosquito vector abundance, 3) vector infection rates, 4) sentinel chicken seroconversion rates, 5) equine cases (for WEE), 6) human cases, and 7) the proximity of virus activity to populated areas. Overall risk is categorized into three levels: normal season, emergency planning, or epidemic conditions. We evaluated this response plan using historical data from years with no, enzootic, and epidemic activity of WEE and SLE in several areas of California to determine whether calculated risk levels approximated actual conditions. Multiple methods of risk calculation were considered for both viruses. Assessed risk based on cumulative temperature, rainfall, and runoff levels over the entire season provided more or equally accurate assessments than biweekly assessments based solely on the previous half-month. For WEE, during years with enzootic activity or early-season periods of years with WEE epidemic activity, combining horse and human cases as a single risk factor improved the model's ability to forecast pending WEE activity, but separating the two factors allowed a better indication of WEE activity during epidemics and periods with no activity. For SLE, assignment of higher risk to drier conditions as measured by rainfall and runoff yielded the most accurate representation of actual virus activity during all recent study periods.