Animals : an open access journal from MDPIJul 28, 2026

A New ORFV F1L mRNA Vaccine: Development, Immune Response, and Comparison with a Commercial Live Vaccine

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Updated Aug 3, 2026

Abstract

The 10 µg F1L-mRNA-LNP vaccine protected BALB/c mice from Orf virus infection with efficacy comparable to a commercial live vaccine.

Both F1L-mRNA-LNP and the commercial live vaccine induced specific antibodies compared to the PBS control group (p < 0.01).
The 10 µg mRNA vaccine group elicited Th1 cytokine and CD8+ T cell responses similar to those of the commercial vaccine (p > 0.05).
The commercial vaccine group showed significantly higher levels of IL-4, indicating a stronger Th2 response (p < 0.05).
Neutralizing antibody titers did not differ between the mRNA and commercial vaccine groups, suggesting similar Th1 cellular immunity but weaker Th2 humoral immunity from the mRNA vaccine.
Upon challenge with the Orf virus, mice vaccinated with the 10 µg F1L-mRNA-LNP showed stable body weight, no clinical symptoms, and reduced viral load.

Simplified

Orf virus (ORFV) is a major pathogen in goats and sheep, and control currently depends mainly on commercial live vaccines. Although mRNA vaccines have revolutionized human medicine, their use in veterinary settings is largely unexplored. In this study, an mRNA vaccine candidate encoding the ORFV F1L protein (F1L-mRNA-LNP) was developed via in vitro transcription and encapsulated in lipid nanoparticles. BALB/c mice were divided into five groups (n = 14 each): three receiving different doses of F1L-mRNA-LNP (5, 10, or 15 μg), one receiving a commercial live vaccine (CV), and a PBS control group. Mice were immunized intramuscularly and boosted after 14 days; immune responses were assessed 14 days later following ARRIVE 2.0 guidelines. Both the F1L-mRNA-LNP and CV vaccines induced specific antibodies versus PBS (p < 0.01). The 10 μg mRNA group showed Th1 cytokine and CD8⁺ T cell responses comparable to CV (p > 0.05), whereas IL-4 (Th2) was significantly higher in the CV group (p < 0.05). Neutralizing antibody titers did not differ between groups, indicating that the mRNA vaccine induces comparable Th1 cellular immunity but weaker Th2 humoral immunity. Upon ORFV challenge, the 10 μg F1L-mRNA-LNP vaccine protected BALB/c mice, as evidenced by stable body weight, no clinical symptoms, and reduced viral load, with efficacy comparable to CV (p > 0.05). This study provides strong evidence supporting the optimization of ORFV mRNA vaccines and highlights the translational potential of the F1L-mRNA-LNP candidate vaccine for veterinary applications.

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A New ORFV F1L mRNA Vaccine: Development, Immune Response, and Comparison with a Commercial Live Vaccine

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