Immune responses in a horse inoculated with the VP2 gene of African horsesickness virus.

This study investigates the immune response of a horse injected with a DNA vaccine containing the VP2 gene of the African horsesickness virus, showing some response in terms of antibody development and notable lymphoproliferation and cytotoxic cellular reaction.

Research Methodology

• The research involved the use of a DNA vaccine on a horse. The DNA vaccine was created using the outer capsid protein VP2 gene from the African horsesickness virus.
• This gene is acknowledged to induce protective immunity in horses against this specific virus.
• The DNA of the VP2 gene was reverse transcribed and placed under the control of the cytomegalovirus immediate-early enhancer/promoter. This control mechanism regulates when and how much of the gene is expressed in the horse.
• The constructed DNA vaccine was then injected repeatedly into a horse via the intramuscular route.

Findings

• After the inoculation, low levels of antibodies against the African horsesickness virus were detected in the horse’s body using the Enzyme-Linked Immunosorbent Assay (ELISA).
• These antibodies, specifically directed against VP2 protein were confirmed using Western blot, a technique used for detection and analysis of proteins.
• There were also detectable levels of neutralizing antibodies identified using a 50% plaque reduction assay which estimates the virus-neutralizing antibodies by measuring their ability to reduce the number of plaques formed by the virus.
• Beyond this relatively weak humoral (antibody-mediated) immune response, there was a significant lymphoproliferative reaction, evidencing that the horse’s immune system was responding to the DNA vaccine.
• Moreover, a cytotoxic cellular reaction was observed against virus-infected cells. This suggests that the horse’s immune system was actively trying to eliminate cells infected by the virus.

Conclusion

• While the humoral response in terms of antibody production was low, the study’s findings demonstrate the potential of a DNA vaccine to stimulate a substantial immune response in the horse, through lymphoproliferation and a cytotoxic reaction against virus-infected cells.
• These findings indicate that even with the low-level generation of antibodies, DNA vaccines can, in some way contribute to the immune response through other mechanisms.
• The research suggests a basis for further investigation into the potential effectiveness of DNA vaccines against the African horsesickness disease and possibly other viral diseases in horses.