ORIGINAL ARTICLE Survey of Omp19 immunogenicity against Brucella abortus and Brucella melitensis: influence of nanoparticulation versus traditional immunization Morteza Abkar 1 & Abbas Sahebghadam Lotfi 2 & Jafar Amani 3 & Khadijeh Eskandari 4 & Mehdi Fasihi Ramandi 5 & Jafar Salimian 3,6 & Gholamreza Nikbakht Brujeni 7 & Saeed Alamian 8 & Mehdi Kamali 4 & Hamid Koushki 4 Received: 26 February 2015 /Accepted: 8 September 2015 # Springer Science+Business Media Dordrecht 2015 Abstract Brucellosis is the most common zoonotic bacterial disease. Prevention of human brucellosis is achieved through pasteurization of dairy products, appropriate sanitation and vac- cination of domestic animals against the Brucella species. B. abortus unlipidated 19 kDa outer membrane protein (U- Omp19) is a promising candidate for a subunit vaccine against brucellosis. This study investigates immunogenicity of Omp19 alone and with Freund’s adjuvant (Omp19-IFA) and N- trimethyl chitosan (TMC/Omp19) nanoparticles, as well as the effect of Omp19 administration route on immunological responses and protection. The omp19 gene was expressed in E. coli BL21 (DE3). After purification, the recombinant Omp19 was loaded onto TMC nanoparticles by ionic gelation with tripolyphosphate. Particle size and loading efficiency of the nanoparticles were determined. Omp19-IFA was adminis- tered intraperitoneally while TMC/Omp19 nanoparticles were administered orally and intraperitoneally. The results indicated that intraperitoneal (i.p.) immunization by Omp19-IFA and TMC/Omp19 nanoparticles induced Th1 and Th2 immune re- sponses, respectively, whereas oral immunization of TMC/ Omp19 nanoparticles induced a mixed Th1/Th17 immune re- sponse. Moreover, oral immunization increased IgA levels in feces. Immunized mice were challenged with virulent B. melitensis 16 M and B. abortus 544. Oral immunization with TMC/Omp19 nanoparticles induced a remarkably high protec- tion level against B. melitensis and B. abortus. The results showed that immunization route has a pivotal role in immune response polarization and protective efficiency of Omp19 anti- gen. Also, it was deduced that the higher protection level achieved through oral administration of TMC/Omp19 nanopar- ticles may be due to the elicited Th17 response. Keywords Brucellosis . Omp19 . Trimethyl chitosan . Oral vaccine . Nanoparticles Introduction Brucellosis is the most common zoonotic bacterial disease that is transmitted from animals to humans. This disease is caused by a facultative intracellular pathogen belonging to the genus Brucella (B), the natural reservoir of which is domestic and wild animals (Cloeckaert et al. 2001). B. suis, B. melitensis and B. abortus mostly cause human brucellosis whereas B. canis and some Brucella species found in marine mammals * Abbas Sahebghadam Lotfi lotfi_ab@modares.ac.ir * Jafar Amani Jafar.amani@gmail.com 1 Department of Molecular Genetics, Faculty of Basic Sciences, Tarbiat Modarres University, Tehran, Iran 2 Department of Clinical Biochemistry, Faculty of Medicine, Tarbiat Modares University, P.O. Box: 14155-6343, Tehran, Iran 3 Applied Microbiology Research Center, Baqiyatallah University of Medical Sciences, Vanak Sq. Molasadra St., P.O. Box 19395-5487, Tehran, Iran 4 Nanobiotechnology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran 5 Molecular Biology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran 6 Chemical Injuries Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran 7 Department of Microbiology & Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran 8 Brucellosis Department, Razi Vaccine and Serum Research Institute, Karaj, Iran Vet Res Commun DOI 10.1007/s11259-015-9645-2