Table 2. The stimulating index of T lymphocyte proliferation in SPF chickens immunized with either pFDNA-PLGA-NPs, pVAX1-F (o), or Blank NP.

Groups	Days post the immunization
	14	28
pFDNA-PLGA-NPs i.n./i.m	1.996±0.262a	3.183±0.137Aa
pFDNA-PLGA-NPs i.n.	1.878±0.237a	3.077±0.177Aa
pFDNA-PLGA-NPs i.m	1.730±0.230a	2.856±0.145Bb
pVAX1-F (o) i.m	1.844±0.234a	2.335±0.199Cc
Blank PLGA-NPs i.n.	1.049±0.307b	1.032±0.137Dd
Blank PLGA-NPs i.m	0.985±0.244b	1.085±0.127Dd

Values are presented as mean ± S.D. of five experiments in each group. Values within the same column with the different lower case letter in the superscript are significantly different (p<0.05; Student's t-test), and with the different upper case letter in the superscript are extremely significant different (p<0.01; Student's t-test). The stimulation indices of chickens immunized with the pFDNA-PLGA-NPs by either i.m, i.n. or i.n./i.m. were extremely significantly higher than those of chickens immunized with the plasmid DNA pVAX1-F (o), or with blank PLGA-NPs (p<0.01), and the chickens immunized with the pFDNA-PLGA-NPs either i.n. or i.n./i.m. had significantly higher stimulation indices than the chickens immunized with the pFDNA-PLGA-NPs i.m at the fourth week post immunization (p<0.05).