Protection of Piglets by a Haemophilus parasuis Ghost Vaccine against Homologous Challenge

Abstract

bCommercial bacterins for Glässer's disease are widely used for the prevention of this disease caused by Haemophilus parasuis; however, the protective efficacy varies depending on the strain and serovar. Bacterial ghosts (BGs) are empty bacterial envelopes that, unlike classic bacterins, suffer no denaturing steps during their production. These properties may lead to superior protection. In this study, a BG vaccine generated from the Haemophilus parasuis serovar 5 reference strain Nagasaki was prepared and used to inoculate piglets. The efficacy of the BG vaccine was evaluated by clinical, bacteriological, serological, and postmortem examinations. Inactivated bacterin (IB) and a placebo control (PC) were compared with the BG vaccine in this study. The results showed that the piglets inoculated with the BG vaccine developed higher antibody activity and higher gamma interferon and interleukin 4 levels than those vaccinated with IB or those in the PC group after primary and secondary exposure to the antigens and challenge. CD4؉ T lymphocyte levels were observed to increase following secondary immunization more in the BG-vaccinated group than in the IB (P < 0.05) and PC (P < 0.05) groups. CD8؉ T lymphocyte levels increased dramatically in all three groups after challenge, and the differences between groups were all significant (P < 0.05). There were fewer tissue lesions and lower bacterial loads in the tissue homogenates in the BG group after challenge. The results suggest that higher CD4 ؉ T lymphocyte levels and both CD4؉ major histocompatibility complex class II-restricted Th1-type and Th2-type immune responses in the BG group are relevant for protection. Haemophilus parasuis is a Gram-negative, nonhemolytic, NAD-dependent bacterium belonging to the Pasteurellaceae family. H. parasuis is a commensal organism of the upper respiratory tract of conventional pigs that causes Glässer's disease, which is characterized by fibrinous polyserositis, polyarthritis, and meningitis (1-3). This disease causes significant losses in the swine industry worldwide, due to its high mortality and morbidity rates (1, 3). Vaccination generally is considered to be the most effective means to control Glässer's disease; however, attempts to develop effective vaccines against H. parasuis have been hampered by a lack of overall knowledge regarding the virulence factors and protective antigens of this bacterium (1). Inactivated bacterin for H. parasuis is a traditional vaccine used around the world that can elicit efficient protection against homologous challenges; however, due to the serovar diversity of H. parasuis, inactivated bacterin is limited in cross-protection (2-4). In a previous study, subunit vaccines comprising recombinant transferrin-binding protein B (TbpB) or outer membrane protein (OMP) formulations enriched with TbpB conferred only partial protection (5). The OMPs PalA, Omp2, D15, and HPS-06257 induced protective responses against H. parasuis (SH0165) in pigs (3), and the OMPs SmpA, YgiW, and FOG have been shown to be prote...

Characterization of aSalmonellaTyphimurium ghost carrying an adjuvant protein as a vaccine candidate for the protection of chickens against virulent challenge

“…Vaccination trials in the laboratory or food-producing animals have demonstrated the ability of bacterial ghost vaccines to stimulate strong induction of immune responses accompanied by significant protection against virulent challenge (Wang & Lu, 2009;Chaudhari et al, 2012;Jawale et al, 2012;Hu et al, 2013). In our experiments, we employed only a fixed time window for challenge and reisolation of the bacteria, and a high dose of virulent challenge strain was used.…”

“…As bacterial ghosts retain all of the surface immunogenic determinants of their living counterparts, they are capable of stimulating strong immune responses, and their vaccine potential has been demonstrated experimentally for the prevention of pathogenic Gram-negative bacterial infections of veterinary importance Marchart et al, 2003;Chaudhari et al, 2012;Jawale et al, 2012;Hu et al, 2013). Here, we used Salmonella Typhimurium ghosts carrying LTB for vaccination experiments in the chicken model.…”

“…Bacterial ghosts are generated by the controlled expression of the plasmid-encoded PhiX174 lysis gene E encoding the 91-amino-acid residue hydrophobic protein E. The induction of protein E-mediated lysis leads to the formation of transmembrane tunnel structures by fusing the inner and outer membranes of Gram-negative bacteria, which consequently leads to a loss of cytoplasmic contents (Witte et al, 1992). To date, several studies have demonstrated that bacterial ghosts generated from pathogenic bacteria are capable of protecting against fatal Gram-negative infections Jalava et al, 2002;Marchart et al, 2003;Chaudhari et al, 2012;Jawale et al, 2012;Hu et al, 2013). Since the natural conformation of outer membrane proteins present in bacteria, including fimbriae, lipopolysaccharide, and peptidoglycan structures, is not altered during the production of bacterial ghosts, these empty bacterial envelopes possess high immunogenicity (Jalava et al, 2002).…”

Characterization of Chemically-Induced Bacterial Ghosts (BGs) Using Sodium Hydroxide-Induced <em>Vibrio parahaemolyticus </em>Ghosts (VPGs)

“…In the lysis E gene-mediated method, it took almost 8 h to produce non-living BGs with complete lysis [8] and the lysis efficiency was commonly 99.9% [3,25,26]. Thus, production of BGs by the chemical mediated lysis is more simple and rapid process than that by the genetically engineered E gene-mediated lysis method.…”

Generation of a Novel Staphylococcus aureus Ghost Vaccine and Examination of Its Immunogenicity against Virulent Challenge in Rats

“…Exceptionally, S. iniae ghosts produced by E gene-mediated lysis were being suggested as a potential vaccine candidate (13). However, a number of studies have demonstrated that the lysis efficiency of genetically inactivated BGs was 99.9% (10,14), suggesting a potential risk of their use as a vaccine. Alternatively, the new approach used to generate E. coli ghosts by using the MICs and minimum growth concentrations of sodium hydroxide (NaOH), sodium dodecyl sulfate, and calcium carbonate (CaCO 3 ) has been described in detail (15)(16)(17).…”