Effects of polar glycopeptidolipids of Mycobacterium chelonae (pGPL-Mc) on haematopoietic regeneration and resistance to infection of sublethally irradiated mice

Immunostimulatory effects of polar glycopeptidolipids of Mycobacterium chelonae for inactivated rabies vaccine

Humoral and cellular immune responses were analyzed with Fuenzalida-Palacios rabies vaccine associated with pGPL-Mc, polar glycopeptidolipids extracted from Mycobacterium chelonae, aiming at its use as adjuvant. These results were compared to those obtained with BCG, a well-known immunostimulator, under the same conditions. Rabies vaccine plus pGPL-Mc (2.5 mg/kg) induced a significant increase in serum neutralizing activity, in vitro lymphocyte proliferation (spontaneous, specific and mitogen stimulation) and delayed type hypersensibility. In addition, pGPL-Mc, as well as BCG, enhanced the vaccine potency. Our results support further studies to encourage the use of pGPL-Mc as an immunostimulator of veterinary vaccines, before consideration for human vaccines.

Stimulatory effects of polar glycopeptidolipids of Mycobacterium chelonae on murine haematopoietic stem cells and megakaryocyte progenitors

The effects of polar glycopeptidolipids of Mycobacterium chelonae (pGPL-Mc) on haematopoietic stem cells and on megakaryocyte progenitors in bone marrow (BM) and spleen were investigated in mice. We studied the in vivo spleen colony-forming ability and marrow repopulating ability of pGPL-Mc by assays of colony-forming units-spleen (CFU-S). The number of CFU-S was increased in BM when both donors and recipients were treated with pGPL-Mc. In contrast, a single treatment of donors induced enhancement of spleen CFU-S. The number of pre-CFU-S was not significantly increased by pGPL-Mc injection. Megakaryocyte (Meg) progenitors were determined in vitro with a quantitative cultural analysis of bone marrow and spleen cells in agar in the presence of spleen-conditioned medium. A statistically significant increase in BM and spleen CFU-Meg was observed two days after the last administration of pGPL-Mc. This experiment points out the ability of pGPL-Mc to induce substantial stimulation of megakaryocytopoiesis and slight proliferation of stem cells in BM, but which is more pronounced in spleen. This molecule therefore appears to be a potential adjuvant of chemo- and radiotherapy in order to palliate the cytotoxic side effects of these cancer therapeutic modalities.

Adjuvanticity of pGPL-Mc and LRS in the immune responses of monkeys to oral immunization with diphtheria and tetanus toxoids

Experiments were carried out to examine the adjuvanticity of polar glycopeptidolipids of Mycobacterium chelonae (pGPL-Mc) or the London rocket seed (LRS) when combined with diphtheria and tetanus toxoids in an oral immunization of the African green monkey. The results showed that none of the monkeys receiving diphtheria and tetanus toxoids combined with 25 mg/kg of pGPL-Mc showed an increase in the the level of diphtheria antitoxin (DA) on the third and sixth weeks following the first and the second immunizations. One monkey from this group responded with increased seroneutralizing antibodies 3 weeks after the third feeding. On the other hand, one monkey, 3 weeks after the first immunization, and three monkeys, 3 weeks after the second and third oral vaccinations, showed an increase in specific anti-diphtheria antibody responses when the toxoids were combined with 25 mg/kg of LRS. The anti-diphtheria antitoxin responses of monkeys receiving diphtheria and tetanus toxoids combined with 50 mg/kg of pGPL-Mc or 50 mg/kg of LRS were significantly enhanced compared to the groups administered 25 mg/kg of the two adjuvants. The increase was observed in four out of five pGPL-Mc administered and in three out of five LRS-receiving monkeys. The results show that pGPL-Mc induced the highest titres of anti-diphtheria antitoxin compared to LRS, whereas the level of anti-diphtheria antitoxin titre of the two monkeys receiving the toxoids alone was less than 0.1 i.u./ml of serum throughout the experiment. According to the statistical analyses, no significant differences were recorded between the diphtheria antitoxin responses of monkeys following the first, second or third administration of LRS-adjuvated diphtheria and tetanus toxoids. However, a significant difference (P < or = 0.05) was observed in the diphtheria antitoxin response between the first and the second immunization of monkeys administered with toxoids adjuvated with 50 mg/kg of pGPL-Mc. The tetanus antitoxin responses of all monkeys were less than 0.1 i.u. of antitoxin per millilitre of serum throughout the study, which is considered not to be protective. However, we have recorded an anti-tetanus antitoxin titre of more than 0.2 i.u./ml of serum in one monkey that received diphtheria and tetanus toxoids combined with 50 mg/kg of pGPL-Mc.