2016

The development of an enlonged bacterial vaccine against Erysipelothrix rhusiopathiae infection

Teshima, K.¹⁾,Kamada, T.¹⁾, To, H.¹⁾,Oshima, A.¹⁾, Sasakawa, C.¹⁾, Tsutsumi, N.^1)
1) Nippon Institute for Biological Science
International Pig Veterinary Society Congress 2016, Dublin, Ireland
【Introduction】 Phagocytosis of microbes by monocytes is a crticial factor to enhance vaccine effects. It was previously reported that the bigger size of bacteria resulted in higher probability of phagocytosis compared with the normal ones. For instance, S.pneumoniae with longer chains were easily uptaken in vitro due to the deposition of complements. However, it is not well proved whether the uptake of the bigger size of bacteria induces acquired immunity in vivo and enhances vaccine effects. Here, we proposed the system to elongate the bacteria, E.rhusiopathiae (ER), and applied this system to examine the vaccine effects of elongated bacteria by in vivo administration. Our results indicate that elongation of bacteria is required for enhancing the vaccine effect but not sufficient. 【Materials and Methods】 ER was grown with cephalexin, inactivated by formalin, and supplemented with micro emulsion as adjuvant. Mice were immunized subcutaneously with the vaccines. For the detection of anti-SpaA (a photogenic factor of ER) antibodies by ELISA, blood samples were collected. After the immunization, the mice were challenged with ER. 【Results】 In 3 h incubation with cephalexin, the length and number of elongated bacteria was 3 and 0.1 times larger than those of the non-treated bacteria, respectively. When they were administrated to mice, the survival rate in a group of mice vaccinated with elongated bacteria (A), non-treated bacteria (B) and sole cephalexin mixed with non-treated bacteria (C) are 80%, 20% and 10%, respectively. Titer of anti-SpaA antibody in group A showed more than twice larger than that of group B and C. These results indicated that vaccination with elongated bacteria potentiate to induce stronger protective immunity against ER infection than that with control bacteria. To examine the vaccine effects of components within elongated bacteria, bacteria after incubation with or without cephalexin were collected. When bacteria vaccine without supernatants were administrated to mice, there was no difference in both the survival rate and titer of anti-SpaA antibody between group A and B. These results suggest that not only intra-cellular components within elongated bacteria but also the secretion suspended in the supernatants contributes to the enhancement of vaccine effects. 【Conclusion】 Vaccination with elongated bacteria including the supernatants induces higher immunological response than one with non-treated bacteria, resulting in protection of ER infection. This effect does not arise from the cell components located inside the cells, rather indicating that elongation of bacteria by cephalexin induces the secretion of some yetuncharacterized bacterial components to enhance vaccine effects.

Adaptation of porcine epidemic diarrhea virus (PEDV) to Vero cells