Monophosphoryl lipid activity

Immunostimulatory adjuvants exert their effects predominantly at the cytokine level or through the activation of costimulatory signals. The type of response required for optimal protection depends on the pathogen. One class of immunostimulatory adjuvants is derived from the lipopolysaccharide of gram-negative bacteria. The most extensively evaluated member of this family, monophosphoryl lipid A (MPL), is obtained from Salmonella minnesota. MPL has been shown to induce the synthesis and release of cytokines, which promote the generation of specific immune responses. 

Extraction of lipid A from LPS takes advantage of the acido-labile ketosidic bond between the lipid A and the ketodeoxyoctanoate (Kdo) in the LPS. Acid and heat are sufficient to disrupt the linkage. The lipid A is insoluble in water and therefore can be readily collected by centrifugation. Harsh hydrolysis such as 0.1 M hydrochloric acid at 100°C, and milder hydrolysis treatment with 1 % acetic acid have been used to liberate lipid A moiety from LPS molecules (Fensom and Meadow, 1970 Morrison and Leive, 1975 Oertelt et al., 2001 Osborn, 1963). The harsh hydrolytic conditions could result in partially dephosphorylation and O-deacylation of lipid A (Karibian et al., 1995). This could affect the biological activities of the lipid A, but is useful for the extraction of monophosphoryl lipid A (Qureshi et al., 1982). Milder hydrolysis conditions, such as sodium acetate at pH 4.5, have been proved to be efficient to cleave the lipid A-polysaccharide bond (Rosner et al., 1979). When the hydrolysis is ineffective, 1% SDS can be added to the system (Caroff et al., 1988). The lipid A can be extracted from the hydrolytic reaction mixture using the solvent of chloroform and methanol (2 1, v/v). 

Caglar, C., Casella, R.C., Eaves, C.A., Matsuzawa, A., Ichijo, H., Mitchell, T.C. Selective activation of the p38 MAPK pathway by synthetic monophosphoryl lipid A. J Biol Chem 284 (2009) 31982-31991. 

Childers, N.K., Miller, K.L., Tong, G., Llarena, J.C., Greenway, T., Ulrich, J.T., Michalek, S.M. Adjuvant activity of monophosphoryl lipid A for nasal and oral immunization with soluble or liposome-associated antigen. Infect Immun 68 (2000) 5509-5516. 

Jiang, Z.H., Budzynski, W.A., Qiu, D., Yalamati, D., Koganty, R.R. Monophosphoryl lipid A analogues with varying 3-O-substitution Synthesis and potent adjuvant activity. Carbohydr Res 342 (2007) 784-796. 

LPS), monophosphoryl lipid A, and CpG DNA. These substances contain pathogen-associated molecular patterns (PAMPs) that are recognized by and stimulate cells of the immune system. Many of these substances, for example, LPS, have been discovered to act as ligands for Toll-like receptors (TLR). These receptors are expressed on APC, recognize highly conserved motifs on bacteria and viruses, and mediate APC activation. Vaccine developers are now focusing... 

Parr et al. [61] showed that lipid A has the same antitumoral effect as whole endotoxin preparations on murine L5178Y lymphoma. The effects of LPS and synthetic lipid A treatments were compared by Shimizu et al. [158-161] on Meth A fibrosarcoma in BALB/c mouse. The antitumoral activity of different lipids A has also been investigated. Ribi et al. [162] used an extract from S. typhimurium containing lipid A, which when injected directly into hepatocarcinoma line 10 tumors in guinea pigs shows an antitumoral effect. This activity is attributed to a monophosphoryl diglucosamine derivative of lipid A [163], Synthetic lipid A analogs also proved to be active in this system [164], as well as... 

Hie first preparation of an LPS derivative which retained immunostimulatory activity yet had significantly reduced toxicity was made in 1979 by Ribi et al. (1979) who found that mild acid hydrolysis of LPS reduced the pyrogenicity without affecting tumor inhibition activity. Uiis reduced-toxicity product was shown to be the 4/-monophosphoryl derivative of lipid-A (MPL ) (Qureshi et al., 1982). Ribi s group later demonstrated that further alkaline hydrolysis of MPL resulted in de-acylation at the 3 position, producing a molecule with even lower toxicity... 

Like the spinach enzyme, the pea ATPase is activated equally by Mg2+ and Mn2+ and hydrolyzes a broad range of nucleoside triphosphates, but not ADP, AMP, or monophosphorylated substrates. Although pea chloroplast envelope membranes have ADPase and pyrophosphatase activity, we conclude that the activities are distinct from the ATPase activity. The envelope ATPase differs from putative transport ATPases characterized in other plant membranes in that it is not inhibited by vanadate or DCCD, nor is it stimulated by potassium. However, a role for this activity in proton efflux and ion transport cannot be ruled out, because the envelope vesicles may be sufficiently leaky that protons and ions can diffuse freely across the membrane. This might limit any stimulatory effect of K+ and uncouplers. Evidence supporting a role for the ATPase in proton transport will depend on further characterization of the envelope vesicles, and/or purification and reconstitution of the ATPase into artificial lipid vesicles. 

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