Immunogenicity of Outer Membrane Proteins VirB9-1 and VirB9-2, a Novel Nanovaccine against Anaplasma marginale

Anaplasma marginale is the most prevalent tick-borne livestock pathogen and poses a significant threat to cattle industry. In contrast to currently available live blood-derived vaccines against A. marginale, alternative safer and better-defined subunit vaccines will be of great significance. Two proteins (VirB9-1 and VirB9-2) from the Type IV secretion system of A. marginale have been shown to induce humoral and cellular immunity. In this study, Escherichia coli were used to express VirB9-1 and VirB9-2 proteins. Silica vesicles having a thin wall of 6 nm and pore size of 5.8 nm were used as the carrier and adjuvant to deliver these two antigens both as individual or mixed nano-formulations. High loading capacity was achieved for both proteins, and the mouse immunisation trial with individual as well as mixed nano-formulations showed high levels of antibody titres over 107 and strong T-cell responses. The mixed nano-formulation also stimulated high-level recall responses in bovine T-cell proliferation assays. These results open a promising path towards the development of efficient A. marginale vaccines and provide better understanding on the role of silica vesicles to deliver multivalent vaccines as mixed nano-formulations able to activate both B-cell and T-cell immunity, for improved animal health.

Analyse Multiniveau des Facteurs Associés au Retard dans la Vaccination des Enfants au Burkina Faso et au Mali

Plusieurs études effectuées dans les pays développés et les pays anglophones d’Afrique montrent que le contexte influence le statut vaccinal des enfants ainsi que l’administration de certains vaccins spécifiques. Cependant, peu d’études ont porté spécifiquement sur les pays d’Afrique francophone, particulièrement ceux du Sahel comme le Burkina Faso et le Mali. En analysant les données provenant des enquêtes démographiques et de santé du Burkina Faso (2010) et du Mali (2006) à travers une approche de régression logistique multiniveau, cet article évalue dans quelle mesure le contexte influence le respect du calendrier vaccinal des enfants de 12 à 59 mois. Les résultats montrent que les variances contextuelles demeurent significatives dans le modèle final même si le respect du calendrier vaccinal reste surtout tributaire des caractéristiques individuelles de l’enfant. Notamment, au Mali, plus le niveau de vie moyen du district de recensement augmente, plus le risque pour un enfant de recevoir un vaccin en retard diminue. Ces résultats invitent les acteurs de la santé publique à mettre en œuvre des approches communautaires ciblant les barrières locales qui empêchent une vaccination correcte des enfants dans ces deux pays.

DNA prime-protein boost based vaccination with a conserved region of leptospiral immunoglobulin-like A and B proteins enhances protection against leptospirosis

Leptospirosis is a zoonotic disease caused by pathogenic spirochetes of the Leptospira genus. Vaccination with bacterins has severe limitations. Here, we evaluated the N-terminal region of the leptospiral immunoglobulin-like B protein (LigBrep) as a vaccine candidate against leptospirosis using immunisation strategies based on DNA primeprotein boost, DNA vaccine, and subunit vaccine. Upon challenge with a virulent strain of Leptospira interrogans , the prime-boost and DNA vaccine approaches induced significant protection in hamsters, as well as a specific IgG antibody response and sterilising immunity. Although vaccination with recombinant fragment of LigBrep also produced a strong antibody response, it was not immunoprotective. These results highlight the potential of LigBrep as a candidate antigen for an effective vaccine against leptospirosis and emphasise the use of the DNA prime-protein boost as an important strategy for vaccine development.

Co-administration of plasmid-encoded granulocyte-macrophage colony-stimulating factor increases human immunodeficiency virus-1 DNA vaccine-induced polyfunctional CD4+ T-cell responses

T-cell based vaccines against human immunodeficiency virus (HIV) generate specific responses that may limit both transmission and disease progression by controlling viral load. Broad, polyfunctional, and cytotoxic CD4+ T-cell responses have been associated with control of simian immunodeficiency virus/HIV-1 replication, supporting the inclusion of CD4+ T-cell epitopes in vaccine formulations. Plasmid-encoded granulocyte-macrophage colony-stimulating factor (pGM-CSF) co-administration has been shown to induce potent CD4+ T-cell responses and to promote accelerated priming and increased migration of antigen-specific CD4+ T-cells. However, no study has shown whether co-immunisation with pGM-CSF enhances the number of vaccine-induced polyfunctional CD4+ T-cells. Our group has previously developed a DNA vaccine encoding conserved, multiple human leukocyte antigen (HLA)-DR binding HIV-1 subtype B peptides, which elicited broad, polyfunctional and long-lived CD4+ T-cell responses. Here, we show that pGM-CSF co-immunisation improved both magnitude and quality of vaccine-induced T-cell responses, particularly by increasing proliferating CD4+ T-cells that produce simultaneously interferon-γ, tumour necrosis factor-α and interleukin-2. Thus, we believe that the use of pGM-CSF may be helpful for vaccine strategies focused on the activation of anti-HIV CD4+ T-cell immunity.

Vaccination of dogs with Trypanosoma rangeli induces antibodies against Trypanosoma cruzi in a rural area of Córdoba, Argentina

Dogs play a major role in the domestic cycle of Trypanosoma cruzi, acting as reservoirs. In a previous work we have developed a model of vaccination of dogs in captivity with nonpathogenic Trypanosoma rangeli epimastigotes, resulting in the production of protective antibodies against T. cruzi, with dramatic decrease of parasitaemia upon challenge with 100,000 virulent forms of this parasite. The aim of this work was to evaluate the immunogenicity of this vaccine in dogs living in a rural area. Domestic dogs, free from T. cruzi infection, received three immunisations with fixed T. rangeli epimastigotes. Dogs were not challenged with T. cruzi, but they were left in their environment. This immunisation induced antibodies against T. cruzi for more than three years in dogs in their natural habitat, while control dogs remained serologically negative.

Estudio de la capacidad inmunoprofiláctica de proteínas recombinantes de Leishmania infantum en el modelo murino

En esta Tesis Doctoral, cuatro proteínas que están sobre-expresadas en las fases infectivas del ciclo celular de L. infantum (STPKA, STPK, PP2B and PABP3) fueron purificadas para inmunizar ratones BALB/c, con el interés de estudiar su posible capacidad protectora contra la VL. Tres de ellas indujeron una fuerte respuesta humoral en los ratones, rLiSTPKA, rLiSTPK y rLiPABP3, a diferencia de la proteína rLiPP2B. Además, la rLiPABP3 fue la única que indujo una disminución significativa de la carga parasitara tanto en bazo como en hígado 2 meses después de la infección experimental con el parásito. Con el objetivo de determinar los efectos que la inmunización con rLiPABP3 tenía sobre el sistema inmune murino, se determinó la expresión génica de 106 genes relacionados con el sistema inmune en ratones control, inmunizados e infectados. Los niveles de expresión génica fueron comparados con los obtenidos para los grupos control. Los resultados mostraron que durante todo el experimento la proteína rLiPABP3 promueve la inhibición de la respuesta inmune inflamatoria en el bazo de los ratones infectados. Además, no se observa una respuesta adaptiva claramente polarizada hacia un tipo concreto. Un mes después de la infeccion, en los animales previamente inmunizados se observa la sobre-expresion de Il2rb lo que nos hace pensar que rLiPABP3 podría estimular la presencia de linfocitos T memoria. En fases más avanzadas de la infección, a pesar de que no observamos una clara diferenciación de una población concreta de linfocitos T efectores, sí observamos la infra-expresión del gen codificante del TNF-alfa, lo que unido a la sobre-expresión del gen Cxcr4 y la ausencia de cambios de la expresión del gen Ccr7 nos hace pensar que la inmunización no sólo mantiene la micro-arquitectura del bazo, sino que también promueve la correcta migración de las DCs desde la MZ hasta el PALS.

VITALITY trial: protocol for a randomised controlled trial to establish the role of postnatal vitamin D supplementation in infant immune health

Introduction Postnatal vitamin D supplementation may be associated with a reduction in IgE-mediated food allergy, lower respiratory tract infections and improved bone health. Countries in the Northern hemisphere recommend universal infant vitamin D supplementation to optimise early vitamin D levels, despite the absence of large trials proving safety or efficacy for any disease outcome. With the aim of determining the clinical and cost-effectiveness of daily vitamin D supplementation in breastfed infants from age 6–8 weeks to 12 months of age, we have started a double-blind, randomised, placebo-controlled trial of daily 400 IU vitamin D supplementation during the first year of life, VITALITY. Methods nd analysis Infants (n=3012) who are fully breastfed and not receiving vitamin D supplementation will be recruited at the time of their first immunisation, from council-led immunisation clinics throughout metropolitan Melbourne, Australia. The primary outcome is challenge-proven food allergy at 12 months of age. Secondary outcomes are food sensitisation (positive skin prick test), number of lower respiratory infections (through hospital linkage), moderately-severe and persistent eczema (by history and examination) and vitamin D deficiency (serum vitamin D <50 nmol/L) at age 12 months. The trial is underway and the first 130 participants have been recruited.

Améliorer la compréhension et la gestion des conflits d’intérêts des experts conseillant la prise de décisions en santé publique

Étude de cas / Case study

Améliorer la compréhension et la gestion des conflits d’intérêts des experts conseillant la prise de décisions en santé publique

Étude de cas / Case study

The impact and control of malignant catarrhal fever in Tanzania

Malignant Catarrhal Fever (MCF), an often-lethal infectious disease, presents as a variable complex of lesions in susceptible ungulate species. The disease is caused by a -herpesvirus following transmission from an inapparent carrier host. Two major epidemiological forms exist: wildebeest-associated MCF (WA-MCF), in which the virus is transmitted to susceptible species by wildebeest calves less than approximately four months of age, and sheepassociated MCF (SA-MCF) in which the virus is spread by sheep (primarily adolescents). Due to the lack of an in-vitro propagation system for the causative agent of the more economically significant SA-MCF, and with the expectation that cross-protective immunity may be provided, vaccine development has focused on the more easily propagated alcelaphine herpesvirus-1 (AlHV-1) that causes WA-MCF. In 2008 a direct viral challenge trial showed that a novel vaccine, employing an attenuated AlHV-1 (atAlHV-1) `C5000 virus strain, protected British Friesian-Holstein (FH) cattle against an intranasal challenge with virulent AlHV-1 `C5000 virus. For cattle keeping people living near wildebeest calving areas in sub-Saharan Africa an effective vaccine would have value as it would release them from the costly annual disease avoidance strategy of having to move their herds away from the oncoming wildebeest. On the other hand, an effective vaccine will release herd owners from the need to avoid MCF, allowing them to graze their cattle alongside wildebeest on the highly nutritious pastures of the calving areas. As such conservationists have raised concerns that the development of a vaccine might lead to detrimental grazing competition. The principle objective of this study was to test the novel vaccine on Tanzanian shorthorn zebu cross cattle (SZC).We did this firstly using a natural challenge field trial (Chapter Two) which demonstrated that immunisation with the atAlHV-1 vaccine was well tolerated and induced an oro-nasopharyngeal AlHV-1-specific and -neutralising antibody response. This resulted in an immunity in SZC cattle that was partially protective and reduced naturally transmitted infection by 56%. We also demonstrated that non-fatal infections occurred with a much higher frequency than previously thought. Because the calculated efficacy of the vaccine was less than that seen in British FH cattle we wanted to determine whether host factors, particular to SZC cattle, had impacted the outcomes of the field trial. To do this we repeated the 2008 direct viral challenge trial using SZC cattle (Chapter Four). During this trial we also investigated whether the recombinant bacterial flagellin monomer (FliC), when used as an adjuvant, might improve the vaccine’s efficacy. The findings from this trial indicated that direct challenge with pathogenic AlHV-1 is effective at inducing MCF in SZC cattle and that FliC is not an appropriate adjuvant for this vaccine. Furthermore, with less control group cattle dying of MCF than expected we speculate that SZC cattle may have a degree of resistance to MCF that affords them protection from infection and developing fatal disease. In Chapter Three we investigated aspects of the epidemiology of MCF, specifically whether wildebeest placenta, long implicated by Maasai cattle owners as a source of MCF, might play a role in viral transmission. Additionally, through comparative sequence analysis, at two specific genes (A9.5 and ORF50) of wild-type and atAlHV-1, we investigated whether the `C5000 strain, the source of which was taken from Africa more than 40 years ago, was appropriate for vaccine development. The detection of AlHV-1 virus in approximately 50% of placentae indicated that infection can occur in-utero and that this tissue might play a role in disease transmission. And, despite describing three new alleles of the A9.5 gene (supporting previous evidence that this gene is polymorphic and encodes a secretory protein with interleukin-4 as the major homologue), the observation that the most frequently detected haplotypes, in both wild-type and attenuated AlHV-1, were identical suggests that AlHV-1 has a slow molecular clock and that the attenuated strain was appropriate for vaccine development. In Chapter Five we present the first quantitative assessment of the annual MCF avoidance costs that Maasai pastoralists incur. In particular we estimated that as a result of MCF avoidance 64% of the total daily milk yield during the MCF season was not available to be used by the 81% of the family unit remaining at the permanent boma. This represents an upper-bound loss of approximately 8% of a household0s annual income. Despite these considerable losses we concluded that, given an incidence of fatal MCF in cattle living in wildebeest calving areas of 5% to 10%, if herd owners were to stop trying to avoid MCF by allowing their cattle to graze alongside wildebeest, any gains made through increased availability of milk, improved body condition and reduced energy demands would be offset by an increase in MCF-incidence. With the development of an effective vaccine, however, this alternative strategy might become optimal. The overall conclusion we draw therefore is that, despite the substantial costs incurred each year avoiding MCF, the partial protection afforded by the novel vaccine strategy is not sufficient to warrant a wholesale change in disease avoidance strategy. Nonetheless, even the partial protection provided by this vaccine could be of value to protect animals that cannot be moved, for example where some of the herd remain at the boma to provide milk or where land-use changes make traditional disease avoidance difficult. Furthermore, the vaccine may offer a feasible solution to some of the current land-use challenges and conflicts, providing a degree of protection to valuable livestock where avoidance strategies are not possible, but with less risk of precipitating the potentially damaging environmental consequences, such as overgrazing of highly nutritious seasonal pastures, that might result if herd owners decide they no longer need to avoid wildebeest.