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Background: Sarcoid tumors are common in horses and may negatively impact the performance and value of the horse. No known treatment is reliably successful., Hypotheses/objectives: To determine tolerability, overall response rate, time to response, and progression-free survival of horses with biopsy-confirmed or suspected sarcoids treated with ALVAC-fIL2., Animals: Client-owned horses with measurable, presumed- or biopsy-confirmed sarcoid tumors., Methods: Prospective pilot study. One milliliter of ALVAC-fIL2 was injected into 4 to 5 areas of the sarcoid(s) in each horse (week 0); this treatment was repeated in weeks 1, 3, and 7. Sarcoids were measured at each visit, and response to treatment was determined according to the Response Evaluation Criteria in Solid Tumors for dogs (v1.0). After the final treatment, horses were reassessed and sarcoids remeasured every 3 months until tumor progression or for a minimum of 1 year if progression was not documented., Results: Fourteen horses were included. Tumor size decreased in 86% of the horses, and the median time to first response was 89 days (range, 34-406 days). Median time to best response was 211 days (range, 56-406 days), but 3 of the sarcoids still were decreasing in size at the time of final evaluation. The median progression-free interval was not reached. Adverse events were minimal and included transient focal inflammation in 2 horses., Conclusions and Clinical Importance: Intratumoral injection of ALVAC-fIL2 has promise as a well-tolerated and effective, tissue-sparing treatment for horses with sarcoid tumors., (© 2022 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC. on behalf of the American College of Veterinary Internal Medicine.)

Objective: To determine the tissue-restricted expression pattern of tyrosinase mRNA in canine and equine melanocytic tumors and relative tyrosinase and major histocompatibility complex (MHC) I mRNA expression in variants of melanocytic tumors., Sample: 39 canine and 8 equine tumor samples and 10 canine and 6 equine normal tissue samples., Procedures: RNA was isolated from formalin-fixed, paraffin-embedded tissues. Real-time PCR assays were designed to amplify canine and equine tyrosinase, S18 ribosomal RNA, and major histocompatibility complex I transcripts. Relative expression was determined by use of S18 as a reference and comparison with pigmented and nonpigmented normal tissues., Results: High tyrosinase expression was found in all melanocytic tumors, compared with normal tissues, and expression had no correlation with presence or absence of tumor pigmentation. No significant difference in tyrosinase expression was found among histologic variants of melanocytic tumors. No correlation was found between MHC I and tyrosinase expression or tissue histologic classification., Conclusions and Clinical Relevance: In the present study, the methods used were highly sensitive and specific for detection of tyrosinase expression in equine and canine tumors, and overexpression of this transcript in melanomas was detected. This suggested that a DNA vaccine developed for use in dogs with melanoma that targets tyrosinase may be considered for use in other affected species, such as horses.

Objective: To evaluate the safety and efficacy of a vaccine containing plasmid DNA with an insert encoding human tyrosinase (ie, huTyr vaccine) as adjunctive treatment for oral malignant melanoma (MM) in dogs., Animals: 111 dogs (58 prospectively enrolled in a multicenter clinical trial and 53 historical controls) with stage II or III oral MM (modified World Health Organization staging scale, I to IV) in which locoregional disease control was achieved., Procedures: 58 dogs received an initial series of 4 injections of huTyr vaccine (102 μg of DNA/injection) administered transdermally by use of a needle-free IM vaccination device. Dogs were monitored for adverse reactions. Surviving dogs received booster injections at 6-month intervals thereafter. Survival time for vaccinates was compared with that of historical control dogs via Kaplan-Meier survival analysis for the outcome of death., Results: Kaplan-Meier analysis of survival time until death attributable to MM was determined to be significantly improved for dogs that received the huTyr vaccine, compared with that of historical controls. However, median survival time could not be determined for vaccinates because < 50% died of MM before the end of the observation period. No systemic reactions requiring veterinary intervention were associated with vaccination. Local reactions were primarily limited to acute wheal or hematoma formation, mild signs of pain at the injection site, and postvaccination bruising., Conclusions and Clinical Relevance: Results support the safety and efficacy of the huTyr DNA vaccine in dogs as adjunctive treatment for oral MM., Impact for Human Medicine: Response to DNA vaccination in dogs with oral MM may be useful in development of plasmid DNA vaccination protocols for human patients with similar disease.

Objective: To evaluate injection-site reactions and serum antibody titers in cattle vaccinated with a clostridial vaccine administered SC or via needle-free transdermal injection., Animals: Sixteen 11-to 12-month-old Herefords., Procedures: Cattle in 2 groups were vaccinated on days 0 and 28 with a commercially available multivalent clostridial vaccine administered SC or transdermally Injection sites and serum antibody titers were evaluated at several time points after vaccination. Serum antibody titers against Clostridium perfringens beta toxin, Clostridium novyi alpha toxin, and Clostridium septicum alpha toxin were determined with an ELISA; Clostridium sordellii lethal toxin titers were determined with a toxin neutralization assay., Results: Firm injection site swellings developed in cattle vaccinated via either route; however, at several observation times, swellings were significantly smaller in cattle vaccinated transdermally. Serum titers against C perfringens beta toxin and C septicum alpha toxin did not differ significantly between groups after vaccination; serum titers against C novyi alpha toxin were not significantly different between groups, except on days 10 and 56, when they were significantly higher in cattle vaccinated SC. Titers against C sordellii lethal toxin were significantly higher in cattle vaccinated SC on several days after vaccination, but titers were not significantly different after day 49., Conclusions and Clinical Relevance: Transdermal vaccination of cattle resulted in serum antibody titers that were similar to those induced via SC vaccination and caused injection-site reactions that were significantly smaller. Transdermal vaccination may be an effective technique for vaccinating cattle against clostridial diseases while minimizing local reactions that often develop after clostridial vaccination.