Synergistic effect of polyriboinosinic acid:polyribocytidylic acid and either bacterial peptidoglycans or synthetic N-acetylmuramyl peptides on production of adjuvant-induced arthritis in rats

Abstract

Lewis rats developed polyarthritis after a single injection of a water-in-oil emulsion containing various peptidoglycans (PGs) derived from Lactobacillus plantarum. A copolymer of polyriboinosinic acid and polyribocytidylic acid markedly potentiated the arthritogenicity of these PGs. The synthetic adjuvants N-acetylmuramyl-L-alanyl-D-isoglutamine (MurNAc-L-Ala-D-isoGln) and MurNAc-L-Ala-D-Gln were non-arthritogenic, but they did produce severe arthritis when mixed in a water-in-oil emulsion with a copolymer of polyriboinosinic acid and polyribocytidylic acid. Substitution of either L-isoGln or D-isoAsn for the D-isoGln in the MurNAc-L-Ala-D-isoGln markedly reduced its capacity to induce the disease. Taken together with the results of skin testing against various PGs and MurNAc-L-Ala-D-isoGln in the diseased rats, the present results suggest that (i) a minimal essential structure required for development of polyarthritis is related to a larger molecule than either MurNAc-L-Ala-D-isoGln or a monomer of PG, probably to a dimer of PG, and (ii) an antigenic determinants) for the delayed-type skin hypersensitivity to PGs exists on a common structure shared among these PGs, possibly somewhere on a monomer of PG not on N-acetylmuramyl peptides.

Arthritis-inducing ability of a synthetic adjuvant, N-acetylmuramyl peptides, and bacterial disaccharide peptides related to different oil vehicles and their composition

“…Histological studies ofjoints and adjacent tissues were carried out in the fully developed arthritic rats 14 to 21 days after inoculation of 100 .ug of MDP in a water-in-oil emulsion of Difco incomplete adjuvant. The histological changes (data not shown) were indistinguishable from those induced by BCG or Freund complete adjuvant (12). The regional lymph nodes, such as left popliteal and inguinal lymph nodes, developed epitheloid granuloma in the rats injected with MDP in either Difco oil or heavy mineral oil as described previously (7).…”

“…Various bacterial cell walls or their peptidoglycans were able to substitute for Mycobacterium in Freund complete adjuvant to produce AA (11,14). Our previous findings (12,17,18) indicated that (i) adjuvant-active bacterial cell walls produced AA, whereas adjuvant-inactive cell walls did not, (ii) peptidoglycans extracted from both adjuvant active and inactive bacterial cell walls produced AA only when the peptidoglycans consisted of two or more glycan chains, and (iii) neither peptidoglycan monomer (N-acetylglucosaminyl-N-acetylmuramyl-L-alanyl-D-isoglutaminylmeso-diaminopimelyl-D-alanine or N-acetylglucosaminyl -N-acetylmuramyl -Lalanyl -Disoglutaminyl-L-lysyl-D-alanine) nor synthetic adjuvants such as N-acetyl-muramyl-L-alanyl-D-isoglutamine (MDP) and its various analogs produced AA until they were injected together with a copolymer of polyriboinosinic acid and polyribocytidylic acid (12).…”

“…In this regard, we (18) and others (10, 22) suggested that two or more glycan units of peptidoglycans may play a very important role in the production of polyarthritis. If this is the case, MDP may give rise to a micell in Difco oil not in the other oils, resulting in formation of a very similar structure to two or more glycan units of peptidoglycans, as previously discussed elsewhere (12). This might explain the lesser arthritogenicity of disaccharide peptides in Difco oil than that of MDP in Difco oil; i.e., disaccharide peptides might not give rise to an effective micell even in Difco oil.…”

“…These questions in turn led us to consider whether non-arthritogenic adjuvants such as MDP, its analogs, and peptidoglycan monomers genuinely lack arthritogenicity or not. In fact, our recent findings indicated that non-arthritogenic adjuvants described above were able to produce AA when they were mixed with polyriboinosinic acid:polyribocytidylic acid (12). Furthermore, our preliminary findings indicated that these non-arthritogenic adjuvants produced AA in a water-in-oil emulsion which was made up of Difco incomplete adjuvant (Bayol F as an oil and Arlacel A as an emulsifier) instead of mineral oils such as liquid paraffin, Drakeol, and heavy mineral oil (Squibb & Sons).…”

“…Adjuvancy has been considered necessary to produce AA, but arthritis-inducing ability (arthritogenicity) must require two or more glycan chains of peptidoglycans (12,17,18). Why some bacterial cell walls did not exert adjuvant activity despite their adjuvant-active moiety remained uncertain.…”