AttenuatedSalmonella typhimuriumSV4089 as a Potential Carrier of Oral DNA Vaccine in Chickens

Abstract

AttenuatedSalmonellahas been used as a carrier for DNA vaccine. However,in vitroandin vivostudies on the bacteria following transfection of plasmid DNA were poorly studied. In this paper, eukaryotic expression plasmids encoding avian influenza virus (AIV) subtype H5N1 genes, pcDNA3.1/HA, NA, and NP, were transfected into an attenuatedSalmonella enteric typhimuriumSV4089.In vitrostability of the transfected plasmids intoSalmonellawere over 90% after 100 generations. The attenuatedSalmonellawere able to invade MCF-7 (1.2%) and MCF-10A (0.5%) human breast cancer cells. Newly hatched specific-pathogen-free (SPF) chicks were inoculated once by oral gavage with 109colony-forming unit (CFU) of the attenuatedSalmonella. No abnormal clinical signs or deaths were recorded after inoculation. Viable bacteria were detected 3 days after inoculation by plating from spleen, liver, and cecum. Fluorescentin situhybridization (FISH) and polymerase chain reaction (PCR) were carried out for confirmation.Salmonellawas not detected in blood cultures although serum antibody immune responses toSalmonellaO antiserum group D1 factor 1, 9, and 12 antigens were observed in all the inoculated chickens after 7 days up to 35 days. Our results showed that live attenuatedS. typhimuriumSV4089 harboring pcDNA3.1/HA, NA, and NP may provide a unique alternative as a carrier for DNA oral vaccine in chickens.