Jeong J., Yuk S., Kim J., Gwon G., Kim K., Song C.
Konkuk University, South Korea

In Korea, low pathogenic avian influenza(LPAI) H9N2 was first documented in 1996 and it caused serious economic loss in the Korean poultry industry. To control the H9N2 outbreaks, since 2007, the Korean veterinary authority has permitted the use of the inactivated oil-emulsion vaccine derived from a Korean H9N2 isolate(A/chicken/Korea/01310/2001) in commercial layer and broiler breeder chickens. Despite the vaccination program, one sub-lineage group(KU114/07-like) has survived and currently circulates in Korea. Therefore, selection of more suitable vaccine strains and development of highly protective H9N2 vaccine are needed to prevent an LPAI H9N2 endemic in Korea. At present, there are few articles which have assessed the adjuvanticity of the LAB on mucosal vaccines. However, there are no investigations concerning the adjuvant effect of the LAB on the oil-emulsion vaccine. In the present study, we demonstrated that inactivated oil-emulsion H9N2 vaccine supplemented with LAB provides increased protective efficacy than the non-supplemented oil-emulsion vaccine.

LAB were isolated from kimchi and toenjang(Korean traditional lactic fermented foods) samples obtained from Korean restaurants. Lactobacillus plantarum and Pediococcus lolli from kimchi and toenjang, respectively, were selected based on the in vitro screening assay.
Vaccine escaping H9N2 isolate(A/chicken/Korea/K040110/10) was propagated by inoculating into embryonated chicken eggs and titrated. The virus was inactivated with 0.01M BEI. Low, medium and high doses(105.7, 106.7 and 107.7EID50/0.5ml, respectively) of inactivated antigens or each doses of antigens supplemented with each LAB(108.3CFU/0.5ml) were used to formulate a water-in-oil emulsion vaccine by mixing with oil phase(Montanide ISA 71 VG) at a ratio of 30:70(v/v).
6-week-old SPF chickens were devided into 9 groups(6 birds/group), viz., low dose of vaccine only(G1), low dose+L.plantarum(G2), low dose+P.lolli(G3), medium dose only(G4), medium+L.plantarum(G5), medium+P.lolli(G6), high dose only(G7), high dose+L.plantarum(G8) and high dose+P.lolli(G9). All chickens were injected 0.5ml/birds intramuscularly in the left pectoral muscle.
The adjuvant potential of LAB was assessed by hemaglutination inhibition(HI) test at weekly intervals.

On the first week post vaccination(w.p.v), G5 showed fastest induction of humoral immune response compared to other median dose groups. From 2 w.p.v, LAB supplemented groups had significantly higher HI titer than that of vaccine only groups. Among LAB supplemented groups, groups with L.plantarum showed better protective efficacy than groups with P.lolli. In addition, the L.plantarum group had a dose-sparing effect on antibody titer.

To the best of our knowledge, this is the first study reporting the efficacy of inactivated oil-emulsion vaccine supplemented with LAB. In this study, the oil-emulsion vaccine combined with the LAB elicited a higher humoral immune response. It is well-known that LAB can enhance the systemic immune response by activating various immune cells. Although this study did not include responses of a variety of immune cells, our results imply that supplementation of LAB to inactivated oil-emulsion vaccine could be an attractive strategy to better control of LPAI.

Keywords: Adjuvant, Avian influenza, oil-emulsion vaccine, Lactic acid bacteria, Probiotics, Chicken

Jeong J., et al. (2016). Adjuvant potential of lactic acid bacteria with inactivated oil-emulsion H9N2 vaccine  in chicken. Conference Proceedings of IPC2016. Paper presented at the International Scientific Conference on Probiotics and Prebiotics, Budapest (p. 34.). IPC2016

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