Improved stability and specificity of baits for oral administration of substances to wild boar.

Oral vaccination is one of the most effective interventions for disease control in wildlife. As a result of the recent global reemergence of African swine fever and ongoing classical swine fever and animal tuberculosis, oral vaccination of Eurasian wild boar (Sus scrofa) receives increased interest. Several baits for wild boar and feral pigs have been described, but developing more stable and personalized formulations is important. This paper proposes a new bait formulation primarily composed of corn flour, piglet feed, sugar, and honey as a binder to obtain improved elasticity. The bait consists of a matrix with no protective coats, has a hemispherical shape (ø 3.4 ×1.6 cm), and displays an anise aroma and blue color. The color and aroma did not affect bait choice by wild boar, while bait coloring contributed to avoid consumption by non-target species (corvids). Baits with the new formulation were significantly more resistant to humidity and high temperatures than previous versions. Simulations suggest that baits with the new formulation are elastic enough to resist impacts from a maximum altitude of 750 m. Thus, the new bait prototype solves several problems of previous bait formulations while keeping a format that can be selectively consumed by piglets and adult wild boar.

Assessment of African swine fever vaccine candidate ASFV-G-∆MGF in a reversion to virulence study.

African swine fever (ASF) has gained panzootic dimensions and commercial vaccines are still unavailable. Recently, a series of live attenuated vaccines has raised hope for an efficacious and safe vaccine, among them "ASFV-G-∆MGF". We tested the latter in an in vivo reversion to virulence study in accordance with International Cooperation on Harmonisation of Technical Requirements for Registration of Veterinary Medicinal Products guidelines. Upon forced animal passaging, a virus variant emerged that was associated with transient fever and an increased replication and shedding. However, all animals were healthy upon completion of the study and reversion to significant virulence was not observed. The genomic changes did not affect the recombination site but involved deletions and reorganizations in the terminal regions of the genome. Thus, our study underscores that in-depth safety characterization is needed for live ASF vaccines. For this particular candidate, additional studies should target long-term effects and transmission characteristics before thorough benefit-risk analysis can be carried out.

Taking a Promising Vaccine Candidate Further: Efficacy of ASFV-G-ΔMGF after Intramuscular Vaccination of Domestic Pigs and Oral Vaccination of Wild Boar.

African swine fever (ASF) is a pandemic threat to the global pig industry and wild suids. A safe and efficacious vaccine could monumentally assist in disease eradication. In the past years, promising live attenuated vaccine candidates emerged in proof-of-concept experiments, among which was "ASFV-G-∆MGF". In our study, we tested the vaccine candidate in three animal experiments intramuscularly in domestic pigs and orally in wild boar. Further, a macrophage-grown vaccine virus and a virus grown on permanent cells could be employed. Irrespective of the production system of the vaccine virus, a two-dose intramuscular immunization could induce close-to-sterile immunity with full clinical protection against challenge infection. After oral immunization, 50% of the vaccinees seroconverted and all responders were completely protected against subsequent challenge. All nonresponders developed ASF upon challenge with two acute lethal infections and two mild and transient courses. The latter results show a lower efficiency after oral administration that would have to be taken into consideration when designing vaccination-based control measures. Overall, our findings confirm that "ASFV-G-∆MGF" is a most promising vaccine candidate that could find its way into well-organized and controlled immunization campaigns. Further research is needed to characterize safety aspects and define possible improvements of oral efficiency.

Compartmentalized Immune Response in Leishmaniasis: Changing Patterns throughout the Disease.

Visceral leishmaniasis (VL) is characterized by loss of T-cell responsiveness and absence of Leishmania-specific IFN-γ production by peripheral blood mononuclear cells. However, the expressions of IFN-γ and TNF-α are up-regulated in the tissues and plasma of VL patients. There is a paucity of information regarding the cytokine profile expressed by different target tissues in the same individual and the changes it undergoes throughout the course of infection. In this work we evaluated IFN-γ, TNF-α, IL-10, and TGF-ß mRNA expression using real-time RT-PCR in 5 target tissues at 6 months and 16 months post-infection (PI) in a canine experimental model which mimics many aspects of human VL. The spleen and liver of Leishmania infantum experimentally-infected dogs elicited a pro- and anti- inflammatory response and high parasite density at 6 and 16 months PI. The popliteal lymph node, however, showed an up-regulation of IFN-γ cytokin at commencement of the study and was at the chronic phase when the IL-10 and TGF-ß expression appeared. In spite of skin parasite invasion, local cytokine response was absent at 6 months PI. Parasite growth and onset of clinical disease both correlated with dermal up-regulation of all the studied cytokines. Our VL model suggests that central target organs, such as the spleen and liver, present a mixed cytokine immune response early on infection. In contrast, an anti-inflammatory/regulatory immune response in peripheral tissues is activated in the later chronic-patent stages of the disease.

Vaccination of horses with a recombinant modified vaccinia Ankara virus (MVA) expressing African horse sickness (AHS) virus major capsid protein VP2 provides complete clinical protection against challenge.

African horse sickness virus (AHSV) is an arthropod-borne pathogen that infects all species of equidae and causes high mortality in horses. Previously, a recombinant modified vaccinia Ankara (MVA) virus expressing the protein VP2 of AHSV serotype 4 was shown to induce virus neutralising antibodies in horses and protected interferon alpha receptor gene knock-out mice (IFNAR -/-) against virulent AHSV challenge. This study builds on the previous work, examining the protective efficacy of MVA-VP2 vaccination in the natural host of AHSV infection. A study group of 4 horses was vaccinated twice with a recombinant MVA virus expressing the major capsid protein (VP2) of AHSV serotype 9. Vaccinated animals and a control group of unvaccinated horses were then challenged with a virulent strain of AHSV-9. The vaccinated animals were completely protected against clinical disease and also against viraemia as measured by standard end-point dilution assays. In contrast, all control horses presented viraemia after challenge and succumbed to the infection. These results demonstrate the potential of recombinant MVA viruses expressing the outer capsid VP2 of AHSV as a protective vaccine against AHSV infection in the field.

Towards licensing of CP7_E2alf as marker vaccine against classical swine fever-Duration of immunity.

Classical swine fever (CSF) marker vaccine candidate CP7_E2alf was tested in a "duration of immunity" trial according to the World Organisation for Animal Heath (OIE) guidelines. To this means, 15 weaner pigs were either orally or intramuscularly vaccinated with a single dose of CP7_E2alf vaccine produced under Good Laboratory Practice (GLP) conditions. Ten additional pigs were included as controls. Six months later, all animals were oronasally challenged with highly virulent CSF virus (CSFV) strain "Koslov". Upon vaccination, all but one orally and all intramuscularly vaccinated pigs developed rising and later on stable CSFV glycoprotein E2-specific antibodies. In contrast, no CSFV E(rns)-specific "marker" antibodies were detectable prior to challenge infection. None of the co-housed control animals seroconverted. Upon challenge infection, all seropositive animals were protected from lethal challenge, whereas all control animals and the non-responder developed severe signs of CSF. One control animal recovered, the others had to be euthanised due to animal welfare reasons between days 4 and 7 post challenge infection. All protected animals showed quickly rising neutralizing antibodies reaching high titres by the end of the trial. At the end of the trial, the marker ELISA was positive for most challenged animals that survived the CSFV infection (27 out of 30). Using reverse transcription polymerase chain reaction, low level genome detection was seen in all vaccinated animals between days 4 and 10 post challenge infection, but no virus could be isolated from any samples of these animals. The OIE guidelines require seroconversion in at least 8 out of 10 vaccinated animals. This requirement was fulfilled. Moreover, only control animals should die. With this requirement, only the intramuscular vaccination fully complied as one orally vaccinated pig did not respond. Concluding, CP7_E2alf induced stable antibodies that led to protection from lethal challenge with highly virulent CSFV strain "Koslov" six months after vaccination, with the exception of one non-responder after oral vaccination.