<![CDATA[Vaccination is one of the most effective control measure in preventing Streptococcus agalactiae infection. In this study, vaccine coatings were prepared with certain biomaterials such as chitosan, skim milk, and maltodextrin at concentration 1 % or 10 %, and further freeze-dried. Vaccine selected (in vitro) by tests: viability cell, solubility, protein concentration and protein molecular weight. The result of in vitro test showed that chitosan coating at doses 1 % and 10 % were the best in solubility and protein concentration test. Vaccine coated with chitosan was administrated again by injection (in vivo) in nile tilapia (Oreochromis niloticus) before challenged by S. agalactiae. This test consists of six treatments and three replications, i.e. the fish were injected with liquid vaccine (A), Phospat Buffered Saline (PBS) (B), vaccine with chitosan coating 1 % (C), vaccine with chitosan coating 10 % (D), chitosan 1 % (E), and chitosan 10 % (F). Parameters were observed including survival rate, relative percent survival (RPS), antibody titre, and total leucocyte. The results showed that treatment C showed a significant difference (P < 0,05) in survival rate 92.22 ± 3.85 %, RPS 85.21 ± 7.20 %, and antibody titre highest result, but not significant (P > 0,05) to increase total leukocyte in experimental fish against S. agalactiae infection. In conclusion, vaccine freeze dry with chitosan coated 1 % is effective to improve immunity system of nile tilapia. Abstrak Vaksinasi merupakan salah satu tindakan paling efektif dalam pencegahan infeksi Streptococcus agalactiae. Pada penelitian ini, vaksin disalut dengan bahan biomaterial (kitosan, susu skim, dan maltodekstrin) dengan dosis 1% atau 10%, dan dikeringbekukan. Seleksi vaksin dilakukan secara in vitro dengan melihat uji viabilitas sel, kelarutan, kon-sentrasi protein, dan berat molekul protein. Hasil seleksi menunjukkan bahwa vaksin dengan penyalut kitosan 1% dan 10% berada pada urutan kedua terbaik pada uji kelarutan dan konsentrasi protein. Vaksin yang disalut kitosan diuji-kan kembali secara in vivo melalui injeksi pada ikan nila (Oreochromis niloticus) sebelum diuji tantang dengan bakte-ri S. agalactiae. Uji (in vivo) terdiri atas enam perlakuan dan tiga ulangan yakni perlakuan ikan diinjeksi dengan vaksin cair (A), Phosphat Buffered Saline (PBS) (B), vaksin yang disalut kitosan 1% (C), vaksin yang disalut kitosan 10% (D), kitosan 1% (E), dan kitosan 10% (F). Parameter yang diamati meliputi nilai sintasan, relative percent survival (RPS), titer antibodi, dan total leukosit. Hasil penelitian perlakuan C menunjukkan hasil berbeda nyata (P < 0,05) dengan nilai sintasan 92,22 ± 3,85%, RPS 85,21 ± 7,20%, dan titer antibodi C juga menunjukkan hasil paling tinggi, tetapi tidak berbeda nyata (P > 0,05) untuk meningkatkan jumlah leukosit dalam percobaan melawan infeksi bakteri S. agalactiae. Dengan demikian, vaksin kering beku yang disalut kitosan 1% efektif untuk meningkatkan kinerja imunitas ikan nila.]]>
