Formalin-inactivated Venezuelan Equine Encephalomyelitis (Trinidad Strain) Vaccine Produced in Rolling-Bottle Cultures of Chicken Embryo Cells

Abstract

Formalin-inactivated Venezuelan equine encephalomyelitis vaccine was prepared from virus grown in rolling-bottle cultures of chicken embryo cells. Trinidad strain virus was propagated in these cultures with a maintenance medium consisting of serum-free medium 199 containing 0.25% human serum albumin (USP) and antibiotics. Manipulation of multiplicity of inoculum (0.06 to 0.00006) and maintenance medium volume (100 to 300 ml) resulted in high-titered virus yields and only moderate cell destruction when fluids from infected cultures were harvested at 18 to 24 hr. The virus was inactivated at 37 C by 0.05% Formalin within 8 to 10 hr and with 0.1% Formalin within 6 to 8 hr. Single dose, antigen extinction tests in mice performed with 30 small-scale vaccine lots showed excellent potency at either Formalin concentration with inactivation periods ranging from 24 to 96 hr.

Inactivated Venezuelan Equine Encephalomyelitis Vaccine Prepared from Attenuated (TC-83 Strain) Virus

“…Use of a killed product would present none of the problems associated with live vaccine. Moreover, because the danger resulting from residual live virus is greatly minimized through the use of the attenuated, TC-83 strain virus, the vaccine described in this paper represents an improvement in safety as compared with the killed Trinidad strain product (3). Use of such attenuated strains for killed products has been advocated for several years by Darwish and Hammon (4,5).…”

“…Potency test. Vaccine potency was determined as previously described by using a single dose, antigen extinction test in 3-week-old CD-1 white mice (3).…”

“…In an earlier paper, we outlined the usefulness of an inactivated Venezuelan equine encephalomyelitis (VEE) vaccine and described the preparation of such a vaccine from the Trinidad strain of VEE virus (3). However, in view of the reluctance to use a product prepared from a highly virulent, "exotic" strain of VEE virus, studies were initiated to determine if an equally potent vaccine could be prepared from the now widely used attenuated TC-83 strain of VEE virus (8,12).…”

Current Understanding of the Molecular Basis of Venezuelan Equine Encephalitis Virus Pathogenesis and Vaccine Development

“…Formalin inactivated TrD strain of VEEV was one of the first inactivated VEEV vaccines to be developed [ 134 ]. It was widely used to immunize equines in endemic areas, but residual virulence due to escaped live virus particles presented a significant risk.…”

A Multiagent Alphavirus DNA Vaccine Delivered by Intramuscular Electroporation Elicits Robust and Durable Virus-Specific Immune Responses in Mice and Rabbits and Completely Protects Mice against Lethal Venezuelan, Western, and Eastern Equine Encephalitis Virus Aerosol Challenges

“…The live-attenuated VEEV IND vaccine, TC-83, provides long-lasting immunity and protection from both subcutaneous and aerosol VEEV challenges; however, it causes significant adverse reactions in approximately 25% of recipients, and approximately 20% of recipients fail to develop a detectable neutralizing antibody response [ 11 , 12 ]. The formalin-inactivated VEEV IND vaccine derived from TC-83, C-84, and the formalin-inactivated WEEV and EEEV IND vaccines are well tolerated, but they require frequent boosting to elicit and maintain detectable neutralizing antibody responses in humans and have exhibited suboptimal protection against aerosol viral challenge in animal studies [ 13 – 15 ]. In addition, immune interference has been documented when the VEEV, WEEV, and EEEV IND vaccines are administered simultaneously or sequentially in humans [ 16 – 18 ].…”