Immunogenicity of purified venezuelan equine encephalitis virus inactivated by ionizing radiation.

The research article is centered on the study of immunogenicity of a purified and concentrated version of the Venezuelan equine encephalitis (VEE) virus which was inactivated utilizing ionizing radiation. This de-activated virus was found to retain a high level of immunity-provoking capabilities in spite of having its infectious properties removed.

Study Method

• The researchers began with a purified and concentrated form of the VEE virus, sourced from tissue cultures. They then employed ionizing radiation to deactivate the virus, ensuring it didn’t lose its serological activity — the ability to react with certain antibodies in serum, in the process.
• The noninfectious VEE virus was then tested on mice via fluid vaccines. The test aimed at observing the level of protection conferred against a lethal challenge with the Trinidad strain of the VEE virus, which is homologous, i.e. similar in sequence, with the deactivated virus.
• Mice were given either one injection of undiluted vaccine or three injections of 1:100 diluted vaccine. Observations about survival rate were noted and linked directly to vaccine concentration or number of injections.
• In addition to just the virus, the study also assessed the effectiveness of adjuvant 65, a nontoxic metabolizable vehicle, combined with the deactivated VEE virus. This combination was given to the mice either intraperitoneally (injected into the abdominal cavity) or subcutaneously (injected under the skin).
• The research also covered experimentation on guinea pigs, which were immunized subcutaneously with the vaccine combined with adjuvant 65, followed by a lethal challenge involving 1,000,000 guinea pig intraperitoneal LD(50).

Study Findings

• The findings revealed that the radiation-inactivated VEE virus still maintained a high level of immunogenicity, i.e., it could effectively trigger an immune response.
• Results on mice showed a direct correlation between the survival rate and the concentration or frequency of vaccine doses. Essentially, all mice administered with a single shot of the concentrated vaccine survived a lethal dose of virus (100,000 mouse intraperitoneal LD50) administered 21 days later. Similarly, complete protection was observed in mice given three injections of the diluted vaccine.
• Furthemore, the combination of the inactivated VEE virus with adjuvant 65 showed appreciable efficacy, protecting mice against lethal virus challenge regardless of whether the combined vaccine was administered intraperitoneally or subcutaneously.
• Using the adjuvant-combined vaccine, guinea pigs were also successfully immunized against a significantly lethal challenge (1,000,000 guinea pig intraperitoneal LD50).
• Overall, the research underlines the potential of a radiation-inactivated VEE virus vaccine technique in conferring immunity against VEE, with considerable prospects for practical use in both mice and guinea pigs.