Lambda display phage as a mucosal vaccine delivery vehicle for peptide antigens.

Bacteriophage are structurally stable in the gastro-intestinal tract and have favorable traits of safety, stability, ease of production, and immunogenicity. These attributes make them potential candidates as oral vaccine delivery vehicles but little is known about their capacity to induce mucosal immune responses in the small intestine. Whole body imaging of mice confirmed lambda bacteriophage (LP) were distributed throughout the gastro-intestinal tract 24 h after oral delivery. In newborn calves, targeted delivery of LP within the small intestine confirmed LP were immunogenic in a dose-dependent manner and were taken up by Peyer's patches. LP-specific IgA responses were induced within both Peyer's patches and draining mesenteric lymph nodes. A lambda display phage (LDP) was constructed to present three immunogenic disease specific epitopes (DSE) from cervid prion protein (amino acids 130-140 [YML]; 163-170 [YRR]; and 171-178[YRR]) fused to phage capsid head protein D (LDP-DSE). Targeted delivery of purified LDP-DSE to intestinal segments induced IgA responses to all three peptide epitopes. Further, delivery of bacteria expressing soluble D-DSE also induced epitope-specific IgA responses in the targeted Peyer's patches. These are the first studies to report use of LDP to induce epitope-specific IgA responses in the small intestine andconfirm Peyer's patchesfunction as a site for LP uptake. Furthermore, IgA responses to peptide epitopes on LDP were observed in the absence of a mucosal adjuvant. These observations confirm LDP have the capacity to function as a mucosal delivery vehicle with protein D as an effective carrier for peptide epitopes.

Efficacy of parenteral vaccination against porcine circovirus type 2 (PCV2) in seropositive piglets.

This study investigated if parenteral administration of a prototype adjuvanted vaccine against porcine circovirus type 2 (PCV2) could override maternally derived antibodies and induce acquired immunity in young piglets. Piglets with high levels of maternal PCV2 antibodies at 1 wk of age were randomly grouped into vaccinates and controls on the basis of body weight and inoculated with the vaccine or a control preparation twice, with an interval of 3 wk. Both groups were challenged 3 wk after the booster vaccination and euthanized 3 wk after challenge. The pigs were evaluated for clinical disease, histologic lesions in sections of gastric and left inguinal lymph nodes stained with hematoxylin and eosin, and the amount of PCV2 antigen in the lymph nodes by immunohistochemical study. The PCV2 antibody titers were monitored by competitive enzyme-linked immunosorbent assay throughout the experiment. The vaccinates showed significantly less decline (P < 0.05) in PCV2 antibody titers after the booster vaccination. Clinical disease did not develop in any of the piglets. The vaccinates and controls did not differ in either histologic lesions or amount of PCV2 antigen in the lymph nodes. This study demonstrated some evidence of priming of young piglets in the presence of maternal antibodies. Further studies are recommended to determine the optimum concentration of PCV2 antigen and a suitable adjuvant for the vaccine to achieve the full potential of the strategy of inducing acquired immunity in young piglets that have maternally derived antibodies.

Cette étude visait à déterminer si l'administration parentérale d'un prototype de vaccin avec adjuvant dirigé contre le circovirus porcin de type 2 (PCV2) pouvait outrepasser les anticorps maternels et induire une immunité acquise chez les jeunes porcelets. Les porcelets avec des niveaux élevés d'anticorps maternels anti-PCV2 à 1 sem d'âge étaient regroupés de manière aléatoire en vaccinés et témoins basés sur le poids corporel et inoculés avec le vaccin ou une préparation témoin deux fois à un intervalle de trois semaines. Les deux groupes ont été soumis à une infection défi 3 sem après la vaccination de rappel et euthanasiés 3 sem après l'infection. Les porcs ont été évalués pour la présence de maladie clinique, de lésions histologiques dans des sections de noeuds lymphatiques gastriques et inguinal gauche colorés avec de l'hématoxyline et éosine, et la quantité d'antigène PCV2 dans les noeuds lymphatiques par étude immunohistochimique. Les titres d'anticorps anti-PCV2 ont été suivis par épreuve immuno-enzymatique compétitive tout au long de l'expérience. Les animaux vaccinés ont présenté une diminution significativement moindre (P < 0,05) des titres d'anticorps anti-PCV2 après le rappel de vaccin. La maladie clinique ne s'est développée chez aucun des porcelets. Les animaux vaccinés et les témoins n'ont pas différé quant aux lésions histologiques et à la quantité d'antigènes de PCV2 dans les noeuds lymphatiques. Cette étude a démontré quelques évidences d'amorçage de l'immunité chez les jeunes porcelets en présence d'anticorps maternels. Des études supplémentaires sont recommandées afin de déterminer la concentration optimale d'antigène de PCV2 et un adjuvant adéquat pour le vaccin dans le but d'atteindre le plein potentiel de la stratégie d'induire une immunité acquise chez les jeunes porcelets possédant des anticorps maternels.(Traduit par Docteur Serge Messier).

Dual expression system for assembling phage lambda display particle (LDP) vaccine to porcine Circovirus 2 (PCV2).

The bacteriophage lambda small capsid protein D forms trimers on the phage head. D-fusion polypeptides can be expressed from plasmids in E. coli and remain soluble without aggregation. We report a dual expression system for the display of four immunodominant regions of porcine Circovirus 2 (PCV2) capsid protein (CAP) as D-CAP fusions on lambda display particles (LDP). The LDP-D-CAP preparation proved an effective vaccine in pigs, eliciting both cellular and humoral immune responses and PCV2 neutralizing antibodies. In our dual system wild type D expression was encoded by a heteroimmune infecting phage. The D-fusion protein expression in the infected cells was from an inducible plasmid, enabling the deferral of D-fusion expression until needed. The effective vaccine preparation depended upon the gradient purification of very high concentration, essentially tail-less display particles, not previously described.

Immunogenicity of bacteriophage lambda particles displaying porcine Circovirus 2 (PCV2) capsid protein epitopes.

Phage lambda particles displaying four immunodominant regions of porcine Circovirus 2 (PCV2) capsid protein (LDP-D-CAP) was shown to be immunogenic in pigs. The immunodominant regions were fused to the carboxyl-terminal of lambda head protein D. Expression of D-CAP on lambda display particles was demonstrated by ELISA and Western blots. Pigs receiving LDP-D-CAP, without incorporating adjuvant, showed significant anti-PCV2 immune response following the primary vaccination. The LDP-D-CAP preparation induced PCV2 neutralizing antibodies. Delayed type hypersensitivity (DTH) reaction scores revealed that the immunized pigs were hypersensitive to both lambda phage and PCV2 antigens. The LDP-D-CAP elicited both cellular and humoral immune responses. Neither LDP-D-CAP nor the lambda control elicited any untoward local or systemic reactions following immunization. These studies produced the first potential phage vaccine to porcine Circovirus 2.