New insights into neutrophil and Leishmania infantum in vitro immune interactions.

The interaction between polymorphonuclear leukocytes (PMN) or neutrophils and Leishmania became an interesting focus of research, since PMN turn out to be essential cells in transiently hosting the parasites. This study aims to evaluate whether L. infantum, the etiological agent of zoonotic visceral leishmaniasis, influences the in vitro functional activity of murine neutrophils. Phagocytosis, chemotaxis, oxidative burst, degranulation and apoptosis assays were performed. Cytokines, chemokines and toll-like receptors gene expression were evaluated by Real-time PCR. Results indicate that some of the innate features of PMN immunity were activated when in contact with L. infantum. However, parasites might negatively interfere with PMN defense mechanisms compromising the link between innate and acquired immunity. This work provides additional insights on the inflammatory immune interactions between neutrophils and L. infantum highlighting the role of PMN in Leishmania infection.

Beta-D-glucoside utilization by Mycoplasma mycoides subsp. mycoides SC: possible involvement in the control of cytotoxicity towards bovine lung cells.

BACKGROUND: Contagious bovine pleuropneumonia (CBPP) caused by Mycoplasma mycoides subsp. mycoides small-colony type (SC) is among the most serious threats for livestock producers in Africa. Glycerol metabolism-associated H2O2 production seems to play a crucial role in virulence of this mycoplasma. A wide number of attenuated strains of M. mycoides subsp. mycoides SC are currently used in Africa as live vaccines. Glycerol metabolism is not affected in these vaccine strains and therefore it does not seem to be the determinant of their attenuation. A non-synonymous single nucleotide polymorphism (SNP) in the bgl gene coding for the 6-phospho-beta-glucosidase (Bgl) has been described recently. The SNP differentiates virulent African strains isolated from outbreaks with severe CBPP, which express the Bgl isoform Val204, from strains to be considered less virulent isolated from CBPP outbreaks with low mortality and vaccine strains, which express the Bgl isoform Ala204. RESULTS: Strains of M. mycoides subsp. mycoides SC considered virulent and possessing the Bgl isoform Val204, but not strains with the Bgl isoform Ala204, do trigger elevated levels of damage to embryonic bovine lung (EBL) cells upon incubation with the disaccharides (i.e., beta-D-glucosides) sucrose and lactose. However, strains expressing the Bgl isoform Val204 show a lower hydrolysing activity on the chromogenic substrate p-nitrophenyl-beta-D-glucopyranoside (pNPbG) when compared to strains that possess the Bgl isoform Ala204. Defective activity of Bgl in M. mycoides subsp. mycoides SC does not lead to H2O2 production. Rather, the viability during addition of beta-D-glucosides in medium-free buffers is higher for strains harbouring the Bgl isoform Val204 than for those with the isoform Ala204. CONCLUSION: Our results indicate that the studied SNP in the bgl gene is one possible cause of the difference in bacterial virulence among strains of M. mycoides subsp. mycoides SC. Bgl does not act as a direct virulence factor, but strains possessing the Bgl isoform Val204 with low hydrolysing activity are more prone to survive in environments that contain high levels of beta-D-glucosides, thus contributing in some extent to mycoplasmaemia.