Local and systemic effect of transfection-reagent formulated DNA vectors on equine melanoma.

The study explores the use of DNA vaccination as a solution to equine melanoma in grey horses. Vaccination was conducted using DNA vectors with different combinations, and the researchers observed how they affected tumor volume and the general response of the horse.

Research Design

• The study entailed a clinical examination of 27 grey, melanoma-bearing horses. The horses were divided into three groups of nine.
• These horses were vaccinated on three different days (1, 22, and 78) with DNA vectors. The vectors were encoded for equine IL-12 and IL-18 alone or combined with either human glycoprotein 100 or human tyrosinase.
• The vaccines were administered intramuscularly, and a selected melanoma was locally treated via an intradermal peritumoral injection.
• Prior to each injection and on day 120, the researchers measured the sizes of up to nine melanoma lesions per horse through the use of a caliper and ultrasound.
• Serum antibodies against human glycoprotein 100 and human tyrosinase were measured using cell based flow-cytometric assays.

Statistical Analysis

• An Analysis of Variance (ANOVA) for repeated measurements helped to identify significant influences on the relative tumor volume. Other variables like affiliation to treatment group, local treatment and examination modality were also considered in the ANOVA analysis.
• Tukey-Kramer Multiple-Comparison Test was used for post-hoc testing, to compare the relative volumes on the different examination days.
• Body temperature over time was also analyzed using ANOVA for repeated measurements. A one-way ANOVA was used to evaluate differences in body temperature between the groups. All p-values less than 0.05 were considered statistically significant across all tests.

Results and Conclusion

• The findings showed that the relative tumor volume dropped significantly to 79.1 ± 26.91% by day 120. Notably, analysis showed that factors like the treatment group, local treatment, and examination modality had no significant influence on the results.
• There was no cellular or humoral immune response directed against human tyrosinase or human glycoprotein 100 detected.
• Post-vaccination, horses exhibited increased body temperature on the day after vaccination.
• The study concludes that this represents the first clinical report on a systemic effect counteracting equine melanoma following treatment with DNA vectors encoded with equine IL12 and IL18 and formulated using a transfection reagent.
• Addition of DNA vectors encoding human glycoprotein 100 or human tyrosinase failed to intensify this effect. They observed that the relative tumor volume decreased, regardless of the additional vectors or local treatment.