A Novel Lipoarabinomannan from the Equine PathogenRhodococcus equi

Abstract

Rhodococcus equi is a major cause of foal morbidity and mortality. We have investigated the presence of lipoglycan in this organism as closely related bacteria, notably Mycobacterium tuberculosis, produce lipoarabinomannans (LAM) that may play multiple roles as virulence determinants. The lipoglycan was structurally characterized by gas chromatography-mass spectrometry following permethylation, capillary electrophoresis after chemical degradation, and 1 H and 31 P and twodimensional heteronuclear nuclear magnetic resonance studies. Key structural features of the lipoglycan are a linear ␣-1,6-mannan with side chains containing one 2-linked ␣-D-Manp residue. This polysaccharidic backbone is linked to a phosphatidylinositol mannosyl anchor. In contrast to mycobacterial LAM, there are no extensive arabinan domains but single terminal ␣-D-Araf residue capping the 2-linked ␣-D-Manp. The lipoglycan binds concanavalin A and mannose-binding protein consistent with the presence of t-␣-D-Manp residues. We studied the ability of the lipoglycans to induce cytokines from equine macrophages, in comparison to whole cells of R. equi. These data revealed patterns of cytokine mRNA induction that suggest that the lipoglycan is involved in much of the early macrophage cytokine response to R. equi infection. These studies identify a novel LAM variant that may contribute to the pathogenesis of disease caused by R. equi.

A Lipomannan Variant with Strong TLR-2-dependent Pro-inflammatory Activity in Saccharothrix aerocolonigenes

“…Indeed, lipoglycans are not restricted to members of the mycobacteria, and a number of non-mycobacterial lipoglycans have been isolated and characterized in several actinomycete genera, including Rhodococcus (25,26), Gordonia (27), Amycolatopsis (28), Corynebacterium (29), and most recently Turicella (30) and Tsukamurella (22). In the latter study, we demonstrated that LAM from Tsukamurella paurometabola (TpaLAM) possesses a similar structural prototype when compared with mycobacterial LAM, with distinct mannan and arabinan domains, yet had weak biological activity (22); however, upon chemical degradation of the arabinan domain, the resulting lipomannan moiety elicited a powerful pro-inflammatory response as previously demonstrated with ManLAM (16).…”

Disruption of Cg-Ppm1, a Polyprenyl Monophosphomannose Synthase, and the Generation of Lipoglycan-less Mutants in Corynebacterium glutamicum

“…A number of non-mycobacterial actinomycetes possess lipoglycans, including Rhodococcus ruber (27), Rhodococcus equi (28), Amycolatopsis sulfurea (29), and Tsukamurella paurometabola. 3 Structurally, these lipoglycans are related to mycobacterial LAM, but are typically smaller in size.…”

Phospholipid composition of several clinically relevant Corynebacterium species as determined by mass spectrometry: an unusual fatty acyl moiety is present in inositol-containing phospholipids of Corynebacterium urealyticum

“…The fine structure of Ac 3 PIM 2 remains to be elucidated in Corynebacterium, but the molecular masses found for the species investigated are close to those detected in M. tuberculosis (Khoo et al, 1995) and in Mycobacterium bovis (Gilleron et al, , 2001Nigou et al, 1999). The partial analysis carried out in the present work appears to indicate that, like mycobacteria, the species investigated esterify a mannosyl residue with a saturated fatty acyl moiety (C16 : 0 or C18 : 0), a pattern also observed in Rhodococcus equi (Garton et al, 2002). However, MS-MS experiments also indicated that in C. jeikeium and C. urealyticum unsaturated fatty acyl moieties are similarly present.…”