Delivery of the p67 sporozoite antigen of Theileria parva by using recombinant Salmonella dublin: secretion of the product enhances specific antibody responses in cattle

The p67 sporozoite antigen of Theileria parva has been fused to the C-terminal secretion signal of Escherichia coli hemolysin and expressed in secreted form by attenuated Salmonella dublin aroA strain SL5631. The recombinant p67 antigen was detected in the supernatant of transformed bacterial cultures. Immunization trials in cattle revealed that SL5631 secreting the antigen provoked a 10-fold-higher antibody response to p67 than recombinant SL5631 expressing but not secreting p67. Immunized calves were challenged with a 80% lethal dose of T. parva sporozoites and monitored for the development of infection. Two of three calves immunized intramuscularly with the p67-secreting SL5631 strain were found to be protected, whereas only one of three animals immunized with the nonsecreting p67-expressing SL5631 strain was protected. This is the first demonstration that complete eukaryotic antigens fused to the C-terminal portion of E. coli hemolysin can be exported from attenuated Salmonella strains and that such exported antigens can protect cattle against subsequent parasite challenge.

Protection from experimental autoimmune encephalomyelitis by polyclonal IgG requires adjuvant-induced inflammation

BACKGROUND Intravenous immunoglobulin (IVIG) proved to be an efficient anti-inflammatory treatment for a growing number of neuroinflammatory diseases and protects against the development of experimental autoimmune encephalomyelitis (EAE), a widely used animal model for multiple sclerosis (MS). METHODS The clinical efficacy of IVIG and IVIG-derived F(ab')2 fragments, generated using the streptococcal cysteine proteinase Ide-S, was evaluated in EAE induced by active immunization and by adoptive transfer of myelin-specific T cells. Frequency, phenotype, and functional characteristics of T cell subsets and myeloid cells were determined by flow cytometry. Antibody binding to microbial antigen and cytokine production by innate immune cells was assessed by ELISA. RESULTS We report that the protective effect of IVIG is lost in the adoptive transfer model of EAE and requires prophylactic administration during disease induction. IVIG-derived Fc fragments are not required for protection against EAE, since administration of F(ab')2 fragments fully recapitulated the clinical efficacy of IVIG. F(ab')2-treated mice showed a substantial decrease in splenic effector T cell expansion and cytokine production (GM-CSF, IFN-γ, IL-17A) 9 days after immunization. Inhibition of effector T cell responses was not associated with an increase in total numbers of Tregs but with decreased activation of innate myeloid cells such as neutrophils, monocytes, and dendritic cells. Therapeutically effective IVIG-derived F(ab')2 fragments inhibited adjuvant-induced innate immune cell activation as determined by IL-12/23 p40 production and recognized mycobacterial antigens contained in Freund's complete adjuvant which is required for induction of active EAE. CONCLUSIONS Our data indicate that F(ab')2-mediated neutralization of adjuvant contributes to the therapeutic efficacy of anti-inflammatory IgG. These findings might partly explain the discrepancy of IVIG efficacy in EAE and MS.

Impfungen bei Immunsupprimierten. Mit Fokus auf HIV-positive Personen, Personen mit einer hämatologischen Stammzelltransplantation oder Organtransplantation und Personen mit funktionaler oder anatomischer Splenektomie

Personen mit einer HIV-Infektion, nach einer Organ- oder einer hämatologischen Stammzelltransplantation oder mit einer funktionalen oder anatomischen Asplenie sind gegenüber Infektionen anfälliger. Sie haben eine grössere Komplikationsrate und ein höheres Risiko für einen chronifizierten Verlauf. Impfungen wären eine ideale primäre Präventionsmassnahme, sind aber – durch dieselben Mechanismen des Immundefektes der zu schwereren Krankheitsverläufen führt – in ihrer Wirksamkeit vermindert. Die Impfungen sollen daher, wenn immer möglich, vor Beginn der Immunsuppression oder später zum Zeitpunkt der minimalsten Immunsuppression, durchgeführt werden. Trotzdem bleibt der Benefit von Impfungen bei immunsupprimierten Personen unbestritten, sofern die Indikationsstellung bezüglich Zeitpunkt und Dosierung (Dosismenge und -anzahl), die zu einem maximalen Ansprechen führt, beachtet wird. Lebendimpfungen sind wegen der Gefahr der unkontrollierten Vermehrung der Impfviren bei schwerer Immunsuppression kontraindiziert. Die Serologie soll unspezifischer gemessen werden, da schwer immunsupprimierte Personen im Falle einer relevanten Exposition durch passive Immunisierung mittels spezifischer oder unspezifischer intravenöser Immunglobuline geschützt werden können.

Genetically attenuated, P36p-deficient malarial sporozoites induce protective immunity and apoptosis of infected liver cells.

Immunization with Plasmodium sporozoites that have been attenuated by gamma-irradiation or specific genetic modification can induce protective immunity against subsequent malaria infection. The mechanism of protection is only known for radiation-attenuated sporozoites, involving cell-mediated and humoral immune responses invoked by infected hepatocytes cells that contain long-lived, partially developed parasites. Here we analyzed sporozoites of Plasmodium berghei that are deficient in P36p (p36p(-)), a member of the P48/45 family of surface proteins. P36p plays no role in the ability of sporozoites to infect and traverse hepatocytes, but p36p(-) sporozoites abort during development within the hepatocyte. Immunization with p36p(-) sporozoites results in a protective immunity against subsequent challenge with infectious wild-type sporozoites, another example of a specifically genetically attenuated sporozoite (GAS) conferring protective immunity. Comparison of biological characteristics of p36p(-) sporozoites with radiation-attenuated sporozoites demonstrates that liver cells infected with p36p(-) sporozoites disappear rapidly as a result of apoptosis of host cells that may potentiate the immune response. Such knowledge of the biological characteristics of GAS and their evoked immune responses are essential for further investigation of the utility of an optimized GAS-based malaria vaccine.