[Evaluation of synthetic peptide vaccines against foot-and-mouth disease type A]

We developed a synthetic vaccine against foot-and-mouth disease type A.

We studied two peptide-based vaccines containing residues 131 to 159 of VP1, 20 to 35 of VP4, 21 to 35 of 3A and 29 to 42 of 3B of the AF/72 strain of foot-and-mouth disease virus (FMDV) coupled with a CpG oligodeoxynucleotide (5'-TCGCGAACGTTCGCCCGATCGTCGGTA-3') in guinea pigs. We assayed the FMDV-specific IgG level, serum neutralizing antibody titer, splenic lymphocytes proliferative capacity and peripheral blood T lymphocyte CD4-CD8 subsets distribution.

The data show that high dose did not ensure a good immunity. In our study, 8% (4/5) of peptide 364-2.5-inoculated guinea pigs (2.5 microg of peptide 364 per animal) were protected against AF/72 strain challenge, while the protection ratio from other peptide-immunized groups was lower except the inactivated vaccine-inoculated group which showed a full protection. Our results also indicated that the stimulatory ability of CD4+ T lymphocyte response played a key role in evaluating effective FMDV vaccine. The highest percentage of CD4+ T lymphocyte was 36.6% appeared in inactivated vaccine-immunized guinea pigs, the second was 33.7% in peptide 364-2.5-vaccinated group, whereas the remaining ranged from 18.1% to 27.7%. There was no obvious relation between CD8+ T cells and anti-FMDV infection; our data showed that the CD4/CD8 ratio was not always appropriate for assessing the immune system status.

In general, we not only designed an effective vaccine against FMDV type A, but also discovered some useful information of humoral and cellular responses induced by foot-and-mouth disease vaccines.