Antigenic properties of ovalbumin following heat denaturation at different temperatures: Comparison with enzymatic Denaturation

Eighteen monoclonal antibodies (MAbs) raised from mice which were immunized with either native ovalbumin (NOA) or ovalbumin which had been heat denatured at 100°C, (HDOA) were used to study antigenic modifications induced by either heat or subtilisin treatment. Using enzyme immunoassays (EIA) we have defined three major groups of antigenic sites: Group I thermolabile native epitopes; Group II relatively thermostable native epitopes; Group III epitopes specific to heat‐denatured ovalbumin. Heatdenatured ovalbumin can be separated into monomers and polymers which constitute 1% and 99% of the molecules respectively. Whereas MAbs belonging to Groups I and II bound to the monomeric form (mHDOA), MAbs belonging to Group III only bound to the polymeric form (pHDOA). Plakalbumin (PK) behaved similarly to pHDOA since it was recognized by many MAbs from Group III and a few from Group II. Nevertheless, PK remained as a monomeric molecule, whereas heat‐denatured ovalbumin existed mainly as polymeric aggregates. The epitopes present on ovalbumin after different heating procedures (time/temperature) were found to be stable after cooling, thus allowing specific recognition by different MAbs. The critical modification of the protein structure was found to take place at 75°C. Two main conclusions can be drawn from these results: (i) heat and enzymatic denaturation of ovalbumin led to similar antigenic modifications—these may be explained by the exposure of hydrophobic residues in both HDOA and PK as evidenced from 8‐anilino‐1‐sulphonic acid fluorescence spectra; (ii) the panel of ovalbumin‐specific MAbs was able to differentiate between the various heat treatments which had been applied to ovalbumin within the range 65–85°C, even after subsequent cooling. The aggregation of ovalbumin molecules during the heating process constitutes the main type of antigenic modification.     

Genes in the pX region of human T cell leukemia virus I influence Vav phosphorylation in T cells

Human T cell leukemia virus I (HTLV-I) causes acute leukemic disease in a low percentage of infected individuals through obscure mechanisms. Our studies compare two rabbit HTLV-I-infected T cell lines: one, RH/K34, causes lethal experimental leukemia and the other, RH/K30, mediates asymptomatic infection. We show herein that the product of the protooncogene vav is constitutively Tyr-phosphorylated in RH/K34 but not in RH/K30. A role for the retrovirus in phosphorylation of Vav was assigned by transfection experiments with molecular clones of HTLV-I derived from the two lines. The HTLV-I molecular clone from RH/K30, but not that from RH/K34, down-regulates Vav phosphorylation in a Herpesvirus ateles-transformed T cell line. Use of recombinant virus clones revealed that a pX region sequence differing by two nucleotides between the two clones mediates this down-regulation. Because Vav is involved in T cell signaling and Vav phosphorylation occurs upon activation of T cells, control of the activation state of Vav by viral proteins may relate to the leukemogenic potential of certain HTLV-I-infected cells.     

Antibody to Heat Shock Protein 70 (HSP70) Inhibits Human T-Cell Lymphoptropic Virus Type I (HTLV-I) Production by Transformed Rabbit T-Cell Lines

Adult T cell leukemia is a fatal malignant transformation caused by the human T-cell lymphoptropic virus type I (HTLV-I). HTLV-I is only associated with the development of this disease in a small percentage of infected individuals. Using two rabbit transformed T-cell lines; RH/K30 (asymptomatic) and RH/K34 (leukemogenic), we have investigated the expression of heat shock proteins (HSP) 90 and 70 and the role of anti-HSPs antibodies on virus production. HSPs surface expression was higher on RH/K34 than RH/K30 cells. Heat treatment of cells increased the expression of HSPs proteins and virus production; HSPs augmentation was stabilized after 12 h and virus production reached a maximum between 8 h–12 h then returned to normal level after 24 h of culture. Incubation of cells only with rabbit anti-HSP 70 antibodies prevented virus production specifically in the leukemogenic cell line. The results indicate a relationship between HSP 70 and virus production.     

Mapping of staphylococcal enterotoxin A functional binding sites and presentation by monoclonal antibodies and fusion proteins

Staphylococal enterotoxins (SE) bind with high affinity to major histocompatibility complex (MHC) class II proteins and stimulate large number of T cells via the Vbeta region of the T-cell receptor (TCR). To map the epitopes of SE type A (SEA) involved in MHC binding and cell proliferation, 20 specific anti-SEA monoclonal antibodies (MAbs) and two large glutathione S-transferase fusion proteins corresponding to the amino and carboxy termini, respectively, of SEA were used. The functionality of these antibodies was tested, by MHC binding inhibition, interleukin-2 production, and T-cell proliferation assays. Moreover, I studied the ability of the MAbs to present SEA in vitro to human and murine cells and their reactivity with the two fusion proteins. This study showed that all of the MAbs have a defined effect on one or both immunological properties of SEA and were able to present SEA to human and murine cells. However, one MAb (4H8) recognized SEA but without any interference with its biological activities. When the MAbs were tested to react with the two fusion proteins representing the SEA molecule, all of the MAbs were negative except for two. These results confirmed the presence of two functionally different binding sites of SEA with MHC class II molecules and the importance of the disulfide loop for the mitogenic activity of SEA. I further demonstrated that MAbs can present SEA to immune cells independent of the site recognized by the antibody and that the integrity of the SEA molecule is very important for its functions.     

Role of cannabinoid CB1 receptors and Gi/o protein activation in the modulation of synaptosomal Na+,K+-ATPase activity by WIN55,212-2 and delta(9)-THC

In the present study, we evaluated the effects of the synthetic cannabinoid receptor agonist (R)-(+)-[2,3-Dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone mesylate (WIN55,212-2) and the active component of Cannabis delta-9-tetrahydrocannabinol (triangle up(9)-THC) on Na(+),K(+)-ATPase activity in synaptosomal mice brain preparation. Additionally, the potential exogenous cannabinoids and endogenous opioid peptides interaction as well as the role of G(i/o) proteins in mediating Na(+),K(+)-ATPase activation were also explored. The ouabain-sensitive Na(+),K(+)-ATPase activity was measured in whole-brain pure intact synaptosomes (obtained by Percoll gradient method) of female CF-1 mice and was calculated as the difference between the total and the ouabain (1 mM)-insensitive Na(+),K(+)-ATPase activities. Incubation in vitro of the synaptosomes with WIN55,212-2 (0.1 pM-10 microM) or triangle up(9)-THC (0.1 pM-0.1 microM), in a concentration-dependent manner, stimulated ouabain-sensitive Na(+),K(+)-ATPase activity. WIN55,212-2 was less potent but more efficacious than triangle up(9)-THC. N-(Piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM-251) (10 nM), a CB(1) cannabinoid receptor selective antagonist, had not effect per se but antagonized the enhancement of Na(+),K(+)-ATPase activity induced by both, WIN55,212-2 and triangle up(9)-THC. AM-251 produced a significant reduction in the E(max) of cannabinoid-induced increase in Na(+),K(+)-ATPase activity, but did not significantly modify their EC(50). On the other hand, co-incubation with naloxone (1 microM), an opioid receptor antagonist, did not significantly modify the effect of WIN55,212-2 and completely failed to modify the effect of triangle up(9)-THC on synaptosomal Na(+),K(+)-ATPase. Finally, pre-incubation with 0.5 microg of pertussis toxin (G(i/o) protein blocker) completely abolished the enhancement of ouabain-sensitive Na(+),K(+)-ATPase activity induced by WIN55,212-2. A lower dose, 0.25 microg, decreased the E(max) of WIN55,212-2 by 70% but did not significantly affect its EC(50). These results suggest that WIN55212-2 and triangle up(9)-THC indirectly enhance Na(+),K(+)-ATPase activity in the brain by activating cannabinoid CB(1) receptors in a naloxone-insensitive manner. In addition, the effect of WIN55,212-2 on neuronal Na(+),K(+)-ATPase is apparently due to activation of G(i/o) proteins.     

Multiple/bilateral renal tumors in patients with Birt–Hogg–Dubé syndrome

Objective To describe our findings in four patients with multiple/bilateral renal cell carcinoma (RCC) and Birt–Hogg–Dubé (BHD) syndrome. Patients and methods A series of four patients with BHD syndrome and RCC is analyzed. Patient charts were reviewed for age, sex, presentation, various clinical manifestations, imaging, management and outcome. Results Patients included 2 males and 2 females. Age ranged from 40 to 65 years (mean 56 years). The interval between the diagnosis of skin lesions characteristic of the disease and the development of renal tumors ranged between 1 and 35 years. Three of the patients had bilateral renal tumors (2 synchronous and one metachronous), one patient had multiple renal tumors in one kidney. In one patient the renal mass was diagnosed with a screening CT scan of the abdomen after the diagnosis of BHD syndrome. One patient had associated spontaneous pneumothorax and thyroid tumor. Only one of the 4 patients had prior family history of BHD syndrome. Renal tumors were clear cell type in 3 patients, and chromophobe tumor in one. Tumor size ranged from 2 to 9 cm. Conclusion BHD syndrome is associated with multiple diseases and tumors. We describe four patients with BHD syndrome with multiple or bilateral RCC. Two of the patients were asymptomatic. A high index of suspicion should be present in patients who present with the characteristic skin lesions of BHD syndrome and screening for the presence of renal tumors should be done in those patients. Long term follow up is necessary after treating renal tumors in these patients.     

Degradable and biocompatible nanoparticles decorated with cyclic RGD peptide for efficient drug delivery to hepatoma cells in vitro

Amphiphilic derivatives of poly(benzyl malate) were synthesized and characterized with the aim of being used as degradable and biocompatible building blocks for the design of functional nanoparticles (NPs). An anti-cancer model drug, doxorubicin, has been successfully encapsulated into the prepared NPs and its release profile has been evaluated in water and in culture medium. NPs bearing biotin molecules were prepared either for site-specific drug delivery via the targeting of biotin receptors overexpressed on the surface of several cancer cells, or for grafting biotinylated cyclic RGD peptide onto their surface using the strong and highly specific interactions between biotin and the streptavidin protein. We have shown that this binding did not affect dramatically the physico-chemical properties of the corresponding NPs. Cyclic RGD grafted fluorescent NPs were more efficiently uptaken by the HepaRG hepatoma cells than biotinylated fluorescent NPs. Furthermore, the targeting of HepaRG hepatoma cells with NPs bearing cyclic RGD was very efficient and much weaker for HeLa and HT29 cell lines confirming that cyclic RGD is a suitable targeting agent for liver cells. Our results also provide a new mean for rapid screening of short hepatotropic peptides in order to design NPs showing specific liver targeting properties.     

Flagellin as a good carrier and potent adjuvant for Th1 response: study of mice immune response to the p27 (Rv2108) Mycobacterium tuberculosis antigen

We have recently expressed and characterized the product of the gene Rv2108 of Mycobacterium tuberculosis (MT), the p27 protein. Here, we investigated the immune responses against the p27 protein in the context of different pathogen associated molecular patterns (PAMPs). Different immunization protocols were used. BALB/c mice were immunized either with the p27 recombinant protein in Freund's adjuvant or in phosphate saline buffer (PBS), with a pcDNA3 plasmid containing the gene encoding the p27 protein, or with the Escherichia coli bacteria expressing the p27 protein genetically fused into the flagellin. We found that p27 expressed into the flagellin led to the strongest cellular responses, where we obtained the highest production of IFN-gamma and cell proliferation, an indication of specific Th1-like orientation of the immune response. We confirmed the role of flagellin in this response by using different immunization combinations.