We have used two bacterial proteins from Escherichia coli to express heterologous peptides. Both proteins are situated in the E. coli cell envelope but have different properties: LamB is an integral outer membrane protein, and MalE a soluble periplasmic protein. The peptides were expressed as genetic inserts within "permissive sites" of these recipient proteins, i.e. sites which allow the insertion of foreign peptides without affecting the biological properties of the host protein. In this paper, we summarize preliminary rules governing the immunogenicity of resulting LamB and MalE hybrid proteins when expressed in E. coli. We focus on two model epitopes: either peptide 132-145 from the preS(2) region of hepatitis B virus or peptide 93-103 from poliovirus VP1 capsid protein. We also present first results obtained when the same hybrid proteins were expressed in attenuated Salmonella typhimurium. Plasmids encoding the hybrid proteins were transferred to aroA S.typhimurium by electroporation. In vitro, the hybrid proteins could be expressed at high levels by S. typhimurium. Mice were immunized by parenteral and oral routes. The effect of the carrier protein and the level of its expression on the in vivo behaviour of the immunizing bacteria and on the immune response induced will be discussed.

Animals↗

PubMedDate not supplied

Immunological activities of RU-41740, a glycoproteic extract from Klebsiella pneumoniae. II.--Activation of macrophage cytotoxicity against tumour cells and production of a cytotoxic factor.

RU-41740, a glycoprotein extract from Klebsiella pneumoniae, is an immunomodulating agent with a broad spectrum of activities. It enhances several macrophage functions, including interleukin-1 (IL-1) secretion. Present data show that RU-41740 was able to promote murine macrophage cytotoxicity against tumour cells. A soluble cytotoxic factor (CF) was found in supernatants from macrophage cultures stimulated with RU-41740. These supernatants were shown to contain IL-1. CF was detected on L-929 cells sensitized by actinomycin D. CF was analysed on the basis of MW and pHi: after gel filtration on "Ultrogel Aca54", a single peak of CF was found in the range of 50-60 Kd and was then distinct from IL-1, which was eluted at 15 Kd. After chromatofocusing, CF was found in a narrow peak of pH 4.8. CF was detected in supernatants 2 h after macrophage stimulation by RU-41740, and its release was abolished by pretreatment of macrophages with cycloheximide (2 micrograms/ml). CF described here shares several properties with tumour necrosis factor (TNF).

Animals↗

PubMedDate not supplied

Immunity to chemically induced rat sarcomas: study of the specificity of cytotoxic cells.

Spleen cells from WAG rats bearing methylcholanthrene-induced sarcomas were cytotoxic for homologous tumour cells and for some cell lines derived from other syngeneic tumours. Each tumour induced its own pattern of cross-reactive cytotoxicity. This cross-reactivity was not apparent by in vivo rejection tests. In tumour-bearing rats, specific cytotoxic cells could not be separated from cross-reactive cytotoxic cells. The effector cells did not adhere to plastic surface, they were retained neither on nylon wool nor on anti-Ig columns and were devoid of Fc receptors. After tumour excision the cells displaying specific cytotoxicity had the same properties and thus were probably T cells. In contrast, the cells exhibiting cross-reactive cytotoxicity were lost after passage through a nylon wool column or after the removal of Fc-receptor-bearing lymphocytes. These findings suggest that cross-reactivity could result from antibody-dependent cell-mediate cytotoxicity directed against shared antigens.

Animals↗

PubMedDate not supplied

Guinea pig lymphotoxin. II. Study of its mechanism of action. Its differentiation from migration inhibitory factor and interferon.

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Animals↗

PubMedDate not supplied

[The dental focal infection seen by the internist].

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Adolescent↗

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Study of adjuvant and mitogenic activities of bacterial peptidoglycans with different structures.

The adjuvant and mitogenic properties of bacterial peptidoglycans (PG) of different structures have been compared. The PG from Bacillus megaterium and Staphylococcus aureus were adjuvant-active in the guinea-pig, and mitogenic for guinea-pig and mouse lymphocytes. On the other hand the PG from Micrococcus lysodeikticus and Corynebacterium poinsettiae exerted neither adjuvant nor mitogenic activities. Mitogenic PG were selective B mitogens. They were mitogenic for splenocytes from Nude mice and inactive towards T-cell-enriched populations. They were mitogenic in both germ-free mice and in the C3H/HeJ strain which is unresponsive to lipopolysaccharide.

Adjuvants, Immunologic↗