TY - JOUR T1 - Vibriosis induced by experimental cohabitation in Crassostrea gigas: Evidence of early infection and down-expression of immune-related genes A1 - de Decker,Sophie A1 - Saulnier,Denis AD - IFREMER, Lab Genet & Pathol (LGP), F-17390 La Tremblade, France. UR - https://doi.org/10.1016/j.fsi.2010.12.017 DO - 10.1016/j.fsi.2010.12.017 KW - Oyster-Vibrio interactions KW - Pathogenesis KW - Immune response KW - Non-invasive experimental challenge KW - Real-time PCR N2 - The understanding of reciprocal interactions between Crassostrea gigas and Vibrio sp., whether these be virulent or avirulent, is vital for the development of methods to improve the health status of cultured oysters. We describe an original non-invasive experimental infection technique using cohabitation, designed to explore these interactions. Using real-time PCR techniques we examined the dynamics of virulent and avirulent Vibrio sp. in oyster hemolymph and tank seawater, and made a parallel study of the expression of four genes involved in oyster immune defense: Cg-BPI, Cg-EcSOD, Cg-IκB, Cg-TIMP. No mortality occurred in control animals, but oysters put in cohabitation for 2–48 h with animals previously infected by two Vibrio pathogens suffered mortalities from 2 to 16 days post-cohabitation. Our results show that virulent Vibrio infect healthy individuals after only 2 h of cohabitation, with values ranging from 4.5×102 to 2×104 cells ml−1 hemolymph. Simultaneously, an approximate ten-fold increase of the total Vibrio population was observed in control animals, with a 6.6–78.5-fold up-expression of targeted genes. In contrast, oysters exposed to harmful bacteria had mean expression levels strongly down-regulated by a factor of 9.2–29 (depending on the gene) compared with control animals. Although oysters were still found to be infected by virulent Vibrio after 6–48 h of cohabitation, no significant differences were noted when comparing levels of each transcript in control and infected oysters at the same sampling times during this period: the important differences were noted before 6 h cohabitation. Taken together, our data support (1) the hypothesis that virulent Vibrio disturbs the immune response of this invertebrate host both rapidly and significantly, although this occurs specifically during an early and transient period during the first 6 h of cohabitation challenge, and that (2) expression of targeted genes is not correlated with vibriosis resistance. Y1 - 2011/02 PB - Academic Press Ltd- Elsevier Science Ltd JF - Fish & Shellfish Immunology SN - 1050-4648 VL - 30 IS - 2 SP - 691 EP - 699 ID - 13604 ER -