Biomedical subjects

I Schwartz-Cornil

Publications and source records attributed to I Schwartz-Cornil.

6 recordsLinked to original sources

PubMed2006

Efficacy of particle-based DNA delivery for vaccination of sheep against FMDV.

As an alternative strategy to classical inactivated viral vaccine against FMDV, naked DNA vaccine is attractive because of safety, flexibility and low cost. However DNA vaccination is usually poorly efficient in target species. Indeed we found that naked DNA plasmids encoding for P1-2A3C3D and GM-CSF proteins did not induce any detectable immunity against FMDV in sheep. Interestingly, we demonstrate herein that formulations of DNA on poly(D,L-lactide-co-glycolide) (PLG) or in lipofectin triggered divergent types of immune responses: PLG stimulated a T cell response and could elicit significant neutralising antibody titers, whereas lipofectin generated even higher antibody titers but no significant T cell response. The DNA/PLG regimen used in five sheep protected against clinical symptoms and viraemia and prevented the carrier state in four of them. Thus formulated DNA can be remarkably efficient against FMDV in a ruminant species that is usually refractory to DNA vaccination.

Animals↗

PubMed1998

B-1-like cells exist in sheep. Characterization of their phenotype and behaviour.

Two populations of B lymphocytes, B-1 (CD5+ and/or CD11b+) and B-2 (CD5- and CD11b-) cells have been described. In mice, which is the species of reference for B-1 and B-2 cell studies, these two subsets present different developmental schemes, phenotypes, antibody repertoires, localization and behaviours. Interestingly, in sheep, B cells rearrange their immunoglobulin (Ig) loci around the neonatal period, similarly to murine B-1 cells. However, the phenotype of the sheep B cells has not been characterized with regards to their developmental pathway. In this report, we show that two sheep B-cell subsets can be distinguished on the basis of CD11b expression. Relative to CD11b- B cells, the CD11b+ B cells frequently co-express CD5, CD11c, higher levels of surface IgM (sIgM), show larger cell size and higher cell-cycling activity, and thus present a B-1-like phenotype. However, unlike murine B-1 cells, sheep B-1 like cells mainly localize in blood, display a higher propensity to spontaneous apoptosis relative to B-2-like cells, and proliferate after sIgM stimulation. Our data show that despite neonatal immunoglobulin loci rearrangements, sheep B cells do not all express a B-1-like phenotype. However, B-1-and B-2-like cells co-exist and present phenotypic and behavioural specificities. Nevertheless, sheep B-1-and B-2-like cells differ from the murine B-1 and B-2 cells in their cell behaviour. These subsets can thus not be considered as true homologues among species.

Animals↗

PubMed1998

Bovine leukemia virus-induced lymphocytosis and increased cell survival mainly involve the CD11b+ B-lymphocyte subset in sheep.

In this study, we show that bovine leukemia virus (BLV)-induced persistent lymphocytosis (PL) results from the in vivo expansion of the CD11b+ B-lymphocyte population. This subset shares phenotypic characteristics with murine and human B-1 cells. BLV interactions with the sheep B-1-like subset were explored. We found that B-1- and B-2-like cells are initially infected to similar extents. However, in long-term-infected sheep, the viral load is higher in B-1-like cells and only B-1- and not B-2-like cells show increased ex vivo survival compared to that in uninfected sheep. Ex vivo viral expression was found in both B-1- and B-2-like cells, indicating that both cell types support viral replication. Finally, cycloheximide and a protein kinase C inhibitor (H7) that blocks the ex vivo activation of viral expression did not affect the increased survival in B-1-like cells, suggesting that resistance to apoptosis is acquired in vivo. Collectively, these results indicate a peculiar susceptibility of sheep B-1-like cells to BLV transforming effects and further support the involvement of increased survival in BLV pathogenesis.

Animals↗

PubMed1997

Two- and three-dimensional cell structures govern epidermal growth factor survival function in human bladder carcinoma cell lines.

Human bladder carcinomas often express high levels of the epidermal growth factor (EGF) receptor. In three human bladder carcinoma cell lines (OBR, T24, and 647V), we show that two EGF receptor ligands, namely EGF and transforming growth factor alpha, enhanced the apoptosis due to serum starvation on cells cultured as monolayers. Conversely, EGF and transforming growth factor alpha prevented apoptosis when the same serum-starved cells were cultured as three-dimensional spheroids. Both stimulation and inhibition of apoptosis by EGF were associated with p21 WAF1/CIP1 overexpression. In 647V spheroids, EGF protection against radiation-induced apoptosis was negated by genistein and tyrphostin AG1478, suggesting that blockade of the EGF signal transduction in patients with bladder cancer may improve the radiotherapy efficacy.

Apoptosis↗

PubMed1997

Bovine leukaemia virus-induced lymphocytosis in sheep is associated with reduction of spontaneous B cell apoptosis.

Experimental inoculation of sheep with bovine leukaemia virus (BLV), a retrovirus homologous to the human T-lymphotropic virus type 1 (HTLV-1), induces a chronic expansion of the B lymphocyte population (persistent lymphocytosis) and the development of a B cell leukaemia/lymphosarcoma syndrome. To gain insight into the mechanisms of BLV-induced lymphocytosis, we tested B cell survival capacity and cycling activity in peripheral blood mononuclear cells (PBMCs) from lymphocytotic, asymptomatic and control sheep. Interestingly, B cells from lymphocytotic sheep presented a lower level of spontaneous apoptosis (29%) in ex vivo cultures compared to that obtained with infected asymptomatic (42%) and control (57%/o) sheep PBMCs. Virus capsid (CA) synthesis was mainly found among surviving B cells and the percentage of CA-producing B cells correlated with the extent of B cell survival, indicating that BLV replication in B lymphocytes may promote protection from cell death. B cell survival was not linked with increases in expression of Bcl-2 mRNA or membrane leukosialin (CD43), although both are documented to be involved in some aspects of the B cell life-span. Finally, cell cycle analyses in freshly isolated PBMCs from lymphocytotic sheep revealed a slightly increased proportion of B cells in S phase compared to controls. Altogether, these data suggest that both BLV-induced B cell proliferation and extended survival are involved in the lymphocytotic stage encountered in BLV infection in sheep.

Animals↗

PubMed1996

Bovine immunodeficiency virus: facts and questions.

Bovine immunodeficiency virus (BIV) is a lentivirus whose serologic prevalence is worldwide. Little is known about its impact on animal health status, pathogenesis and mode of transmission. Understanding BIV biology implies isolation of new viral strains and long-term studies on experimentally-infected cows and surrogate hosts such as rabbits.

Animals↗