Efficacy and Safety of an Oral Somatostatin DNA Vaccine without Antibiotic Resistance Gene in Promoting Growth of Piglets

Abstract

This study aimed to evaluate the efficacy and safety of an oral DNA vaccine against somatostatin (SS) (pGS/2SS‐asd, encoding two copies of somatostatin genes) mediated by attenuated Salmonella choleraesuis C500 without antibiotic resistance gene on piglets growth. A total of 50 piglets were uniformly divided into five groups. The animals in the first three groups were orally given vaccine in dose of either 5 × 1010, 5 × 109 or 5 × 108 colony‐forming units (CFU). The remaining two groups were orally administered with either bacteria C500 (containing pVAX‐asd plasmid without somatostatin gene) or phosphate‐buffered saline (PBS) as controls. The results indicated that the vaccine induced SS‐specific antibodies in a dose‐dependent pattern. Compared with the PBS control, animals in the high‐dose group showed lower SS levels and higher growth hormone (GH) levels in sera. Average daily gain of animals in the high‐dose group was increased by 32.88% and 26.46% during 4 and 8 weeks, respectively. Anti‐SS antibodies were positively correlated with either GH levels or average daily gain at week 8 after primary immunization (P < 0.05). Faecal, soil and water samples originating from immunized piglets and surrounding environment were collected. The target gene (the fusion gene GS/2SS) of C500 (pGS/2SS‐asd) was not detected by PCR amplification in these samples, indicating that the surrounding environment was not contaminated by residual recombinant bacteria. In conclusion, the vaccine without antibiotic resistance gene is attributable to improve growth performance of piglets through an influence on GH secretion. Moreover, the immunization did not contaminate the surrounding environment of animals.

Evaluation of a Novel DNA Vaccine Double Encoding Somatostatin and Cortistatin for Promoting the Growth of Mice

“…Although the previous studies have reported various somatostatin genetic vaccines including naked pCS/2SS plasmid and pVGS/2SS plasmid delivered by attenuated Salmonella , the growth-promoting effect of DNA immunization is still unsatisfied [ 7 , 11 ]. Cortistatin (CST) is a neuropeptide that shares high structural and functional homology with somatostatin and has a compensatory effect with somatostatin as found in single SS knockout mice.…”

“…Somatostatin (SS) consists of 14 peptides and is a pleiotropic neuropeptide widely distributed throughout the organism, which is generally viewed as a crucial regulator of several hormones, including growth hormone (GH) [ 1 , 2 ], prolactin (PRL) [ 3 ], follicular stimulating hormone (FSH) [ 4 ], and luteinizing hormone (LH) [ 5 ]. Cumulative studies have demonstrated that both active and passive immunization against somatostatin (SS) could induce a rise in growth hormone, thereby improving the growth or lactation performance of animals such as mice [ 6 , 7 ], chickens [ 8 ], Hu lambs [ 9 ], goats [ 10 ], and piglets [ 11 ]. However, the growth-promoting effect of animals is still not satisfying, especially for large animals.…”

Efficacy and Safety of Nasal Immunisation with Somatostatin DNA Vaccine for Growth Promotion in Fattening Pigs

“…On the other hand, the dose of vaccine may also be a significant contributor to this phenomenon. Han et al reported that oral administration of a 5 × 10 10 CFU/mL concentration of SS DNA vaccine induced 100% antibody positivity in piglets, while 5 × 10 9 CFU/mL and 5 × 10 8 CFU/mL concentrations induced 30% and 20% antibody positivity, respectively [ 20 ]. Furthermore, we examined the levels of cytokines in the serum, and the results showed that the concentrations of IL-4 and IFN-γ in the P group were not significantly different from those in the N group.…”

“…Immunisation against SS has been reported to enhance growth in various species, including mice [ 31 ], lambs [ 9 ], rats [ 22 ], and cattle [ 8 ]. Previous studies in the laboratory have reported that the SS DNA vaccine is attributable to improving the growth performance of piglets through an influence on GH secretion [ 20 ]. In this study, we evaluated the effect of the SS DNA vaccine on growth promotion in fattening pigs.…”

“…Indirect ELISA was used to detect SS antibody titres in pig plasma. For detailed steps refer to the previous study [ 20 ]; those that differ from them include (1) each well of the 96-well micro titre plate was coated 100 ng/100 μL of SS antigen (Sangon Biotech (Shanghai) Co., Ltd.; Shanghai, China); (2) serum samples (100 μL) diluted with PBS (1:25, 1:50, 1:100, 1:200, 1:400, 1:800, 1:1600, 1:3200, 1:6400). Finally, under the same dilution factor, if the OD 450 value of the experimental group was greater than the mean of OD 450 value in the control group + 2SD (standard deviation), then it was judged as positive [ 21 , 22 ].…”