A novel transcutaneous plasmid–dimethylsulfoxide delivery technique for avian nucleic acid immunization

In this report, we show that dimethylsulfoxide (DMSO) enhances liposome-mediated transfection of nucleic acid in chicken macrophage cells and that this could be exploited for the transcutaneous delivery of naked DNA through the intact skin of chickens. We found that DMSO enhanced transfection efficiencies of lipofectamine and polyethyleneimine in HD-11 chicken macrophage cells. Based on this principle, we showed that transcutaneous delivery of a DNA plasmid–dimethylsulfoxide mixture (1:1) to untreated skin of chickens results in a wide distribution of the plasmid in the body. Distribution studies were done using plasmids encoding enhanced green fluorescent protein (EGFP) reporter gene and a bivalent DNA vaccine coding for infectious bursal disease virus (IBDV) and Newcastle disease virus (NDV) immunogenic protein genes. This bivalent vaccine induced mucosal and systemic immune responses, as evidenced by IgA and IgM production in the tears and serum of vaccinated chickens. Mucosal immune responses in the tears after topical vaccination were significantly higher (P<0.05) than after i.m. delivery of the same DNA vaccine and were characterized by the absence of an IgG response. The biodistribution of plasmid indicated that topical delivery with DMSO resulted in a wide distribution and persistence of the plasmid until 15 weeks post-primary vaccination. Both delivery methods resulted in insert-specific message being made in several body tissues, but after topical delivery the virus-specific mRNA could be detected in the bone marrow of one out of three chickens until 15 weeks post-primary vaccination. Furthermore, transcutaneous delivery of this DNA vaccine using DMSO conferred protection from challenge with virulent IBDV (86% survival) and NDV (86% survival). This novel transcutaneous method of delivery of a DNA vaccine shows promise as being an easy and effective way to deliver nucleic acids through intact skin for vaccination or therapeutic purposes.