Objective: In countries where parasitic infections are endemic, autoimmune disease is relatively rare, leading to the hypothesis that parasite-derived immunomodulators may protect against its development. Consistent with this, we have previously demonstrated that ES-62, a 62 kDa phosphorylcholine (PC)-containing glycoprotein that is secreted by filarial nematodes, can exert anti-inflammatory action in the murine collagen-induced arthritis (CIA) model and human rheumatoid arthritis-derived synovial tissue cultures. As a first step to developing ES-62-based drugs, the aim of this study was to determine whether the PC-moiety of ES-62 was responsible for its anti-inflammatory actions. Methods: We compared the anti-inflammatory activity of a PC-free form of recombinant ES-62 (rES-62) and a synthetic PC-ovalbumin conjugate (OVA-PC) with that of native ES-62 in the CIA model and synovial tissues from patients with rheumatoid arthritis. Results: The anti-inflammatory actions of ES-62 in CIA appear to be dependent on the PC moiety as indicated by the reduction in severity of disease and also suppression of collagen-specific T helper 1 cytokine production observed when testing OVA-PC, but not rES-62. Interestingly, the anti-inflammatory activity of PC did not correlate with a reduction in anti-collagen IgG2a levels. Also, the ES-62-mediated suppression of interferon-γ from human patient tissues could be mimicked by OVA-PC but not rES-62 or ovalbumin. Conclusions: In countries where filariasis is endemic the reduced detection of inflammatory diseases, such as rheumatoid arthritis may be because of the anti-inflammatory action of the PC moieties of ES-62. PC may thus provide the starting point for the development of novel, safe immunomodulatory therapies.

We have previously shown glycosphingolipids of Ascaris suum to have phosphorylcholine (PC) and non-PC immunomodulatory moieties. In the present study we further investigated the nature of the immunomodulatory moieties by employing three synthetic glycosphingolipids each possessing features of the original molecule to examine effects on macrophage and dendritic cell (DC) cytokine production and surface co-stimulatory molecule expression. Compound 2, which lacked PC but contained ceramide, had no effect on either macrophages or DCs. Surprisingly however, Compound 1, which contained PC and hence arguably most resembled the native material, had, with the exception of a small increase in surface antigen expression, no immunomodulatory properties. Conversely, Compound 3, which contained PC but was otherwise least like the native molecule, demonstrated a number of effects on both macrophages and DCs, including induction of Th-1/pro-inflammatory cytokines, inhibition of such cytokines induced by IFN-gamma/LPS and increased expression of co-stimulatory molecules. Taken together these results indicate: (i) that although PC is an immunomodulatory component of the native molecule other structural feature are necessary to allow it to act; (ii) that carbohydrate rather than ceramide is likely to represent a non-PC immunomodulatory moiety; and (iii) that synthetic PC-containing molecules have the potential to act as immunomodulatory drugs.