Metabolic plasticity of Salmonella enterica as adaptation strategy in river water.

The survival of Salmonella in subtropical river water depends on genetic and metabolic reorganization for the expression of alternative metabolic pathways in response to starvation, which allows Salmonella to use environmental carbon sources (C-sources). However, knowledge regarding the metabolic plasticity of Salmonella serotypes for C-source utilization when exposed to these conditions remains unclear. The aim of this study was to evaluate the metabolic response and level of environmental C-source consumption by environmental Salmonella (Oranienburg and Saintpaul) and clinical Salmonella (Typhi) serotypes by comparing laboratory growth against exposure to river water conditions. Metabolic characterization was performed using a Biolog® EcoPlateTM containing 31 C-sources. The results obtained under laboratory growth conditions showed that environmental serotypes used 74.1% of the C-sources, whereas the clinical serotype used 45.1%. In contrast, in river water, all strains used up to 96.7% of the C-sources. Salmonella exposure to river water increases its capacity to use environmental C-sources.

Activation of the autophagy pathway by Torovirus infection is irrelevant for virus replication.

Autophagy is a conserved eukaryotic process that mediates lysosomal degradation of cytoplasmic macromolecules and damaged organelles, also exerting an important role in the elimination of intracellular pathogens. Despite the antiviral role of autophagy, many studies suggest that some positive-stranded RNA viruses exploit this pathway to facilitate their own replication. In this study, we demonstrate that the equine torovirus Berne virus (BEV), the prototype member of the Torovirus genus (Coronaviridae Family, Nidovirales Order), induces autophagy at late times post-infection. Conversion of microtubule associated protein 1B light chain 3 (LC3) from cytosolic (LC3 I) to the membrane associated form (LC3 II), a canonical marker of autophagosome formation, is enhanced in BEV infected cells. However, neither autophagy induction, via starvation, nor pharmacological blockade significantly affect BEV replication. Similarly, BEV infection is not altered in autophagy deficient cells lacking either Beclin 1 or LC3B protein expression. Unexpectedly, the cargo receptor p62, a selective autophagy receptor, aggregates within the region where the BEV main protease (Mpro) localizes. This finding, coupled with observation that BEV replication also induces ER stress at the time when selective autophagy is taking place, suggests that the autophagy pathway is activated in response to the hefty accumulation of virus-encoded polypeptides during the late phase of BEV infection.

Improving recombinant MVA immune responses: potentiation of the immune responses to HIV-1 with MVA and DNA vectors expressing Env and the cytokines IL-12 and IFN-gamma.

Recombinants based on vaccinia virus vectors, especially on the highly attenuated modified vaccinia virus Ankara (MVA) strain, are now being tested in clinical trials for safety and immunogenicity, using prime/boost heterologous regimes of vaccination. Due to the limited replication capacity of MVA, it is necessary to develop procedures that can enhance the specific cellular immune responses to the recombinant antigen delivered by the MVA vector. In this investigation, we have characterized the systemic immune responses in BALB/c mice using interferon-gamma (IFN-gamma) or interleukin-12 (IL-12) in an adjuvant-like manner elicited by MVA recombinants or naked DNA vectors expressing one of those cytokines in combination with the human immunodeficiency virus type 1 (HIV-1) envelope (Env) as antigen. In infected mice, virus gene expression in splenocytes and levels of cytokines IFN-gamma and IL-12 in serum were maximal by 6h post-infection (hpi) with MVA recombinants expressing IFN-gamma (MVAIFN-gamma) or IL-12 (MVAIL-12). In the infected animals, co-expression of HIV-1 env (MVAENV) and either IFN-gamma or IL-12 from MVA recombinants produced a two and three-fold increase of anti-env CD8+ T cell response, respectively. When priming was carried out with DNA vectors expressing HIV-1 env and either IFN-gamma or IL-12, the magnitude of the specific anti-env CD8+ T cell stimulation after MVAENV booster was further enhanced. Our findings revealed that IFN-gamma or IL-12 can be used to potentiate the cellular immune response to HIV-1 env, when delivered either from a single MVA recombinant or from a DNA vector. The increment of the CD8+ T cell response was higher in a DNA/MVA prime/boost protocol. Thus, the immune response of MVA vectors can be improved with the co-delivery of the cytokines IFN-gamma or IL-12.

Mucosal immunization of sheep with a Maedi-Visna virus (MVV) env DNA vaccine protects against early MVV productive infection.

Gene gun mucosal DNA immunization of sheep with a plasmid expressing the env gene of Maedi-Visna virus (MVV) was used to examine the protection against MVV infection in sheep from a naturally infected flock. For immunization, sheep were primed with a pcDNA plasmid (pcDNA-env) encoding the Env glycoproteins of MVV and boosted with combined pcDNA-env and pCR3.1-IFN-gamma plasmid inoculations. The pcDNA plasmid used in the control group contained the lacZ coding sequences instead of the env gene. Within a month post-challenge, the viral load in the vaccinated group was lower (p < or = 0.05) and virus was only detected transiently compared with the control group. Furthermore, 2 months later, neutralizing antibodies (NtAb) were detected in all the control animals and none of the vaccinated animals (p < or = 0.01). These results demonstrated a significant early protective effect of this immunization strategy against MVV infection that restricts the virus replication following challenge in the absence of NtAb production. This vaccine protective effect against MVV infection disappeared after two years post-challenge, when active replication of MVV challenge strain was observed. Protection conferred by the vaccine could not be explained by OLA DRB1 allele or genotype differences. Most of the individuals were DRB1 heterozygous and none was totally resistant to infection.

Induction of protective immunity against malaria by priming-boosting immunization with recombinant cold-adapted influenza and modified vaccinia Ankara viruses expressing a CD8+-T-cell epitope derived from the circumsporozoite protein of Plasmodium yoelii.

We immunized mice with an attenuated (cold-adapted) influenza virus followed by an attenuated vaccinia virus (modified vaccinia virus Ankara), both expressing a CD8(+)-T-cell epitope derived from malaria sporozoites. This vaccination regimen elicited high levels of protection against malaria. This is the first time that the vaccine efficacy of a recombinant cold-adapted influenza virus vector expressing a foreign antigen has been evaluated.