Loa22 is an outer membrane protein encoded buy MK-1775 within all Leptospira genomes sequenced to date. It has been observed to be upregulated in vivo and it is one of very few leptospiral proteins so far that has been shown to be necessary for virulence . Additional studies are needed to define the precise context of NulO expression on L. interrogans and understand its potential significance in virulence. Conclusions Based on a combination of experimentation and in silico genomic analysis, we have demonstrated the function of NulO biosynthetic gene clusters in pathogenic and intermediately pathogenic species of Leptospira, several of which are capable of synthesizing di-N-acetylated
NulO species, as well as the true sialic acid, N-acetyneuraminic acid, a finding of considerable consequence for the leptospirosis field. This finding expands the number of important human pathogens that utilize endogenous biosynthetic pathways to elaborate surface structures containing sialic acids and related NulO
molecules . Sialic acids have proven roles in complement LY2874455 chemical structure evasion, intracellular survival, and biofilm formation , and evidence is emerging that some human pathogens with Neu5Ac on their surfaces can engage sialic acid-binding receptors (Siglecs) on leukocyte cell surfaces, resulting in phagocytosis or dampening of bactericidal activities [30–32]. The roles of other NulO molecules such as legionaminic and pseudaminic acids are less well defined, but these molecules have been shown to play roles in behaviors such as autoagglutination, motility, and host colonization [33–37]. Curiously, disease caused by L. interrogans includes bacteremia and meningitis as components of the clinical disease spectrum, similar to the well-characterized Neu5Ac-expressing human bacterial pathogens Group B Streptococcus Neisseria meningitidis E. coli K1, and Haemophilus influenzae. As genetic tools and small animal infection systems for study of Leptospira are further refined, analysis Transferase inhibitor of the
contribution of NulO biosynthesis to the virulence of this neglected disease can be further elucidated. Methods Strains and STA-9090 culture conditions Intermediately pathogenic strains L. licerasiae serovar Varillal strains MMD3731, MMD4847 and CEH008 (isolated from rodents in Peru), L. fainei serovar Hurstbridge strain BUT 6T and the saprophyte L. biflexa serovar Patoc were used for these experiments. Pathogenic Leptospira used in this study included L. interrogans serovar Copenhageni strain L1-130, L. interrogans serovar Lai strain 55601, and L. interrogans serovar Icterohaemorrhagiae wild rodent isolate MMD 3731 that were passaged fewer than 5 times in vitro after re-isolation from hamster liver to maintain virulence. L. santarosai and L. alexanderi serovar Manhao were originally isolated from clinical cases of leptospirosis and now serve as reference laboratory strains.