The present invention relates to a novel chemokine, referred to herein as chemokine-2 or CK-2, including particular embodiments which are derived from fish such as rainbow trout (Oncorhynchus mykiss). The invention provides novel polypeptides corresponding to CK-2 chemokines, as well as nucleic acids that encode a CK-2 chemokine and antibodies that specifically bind to a CK-2 chemokine. Therapeutic methods for using the novel CK-2 chemokines are also provided. In particular, the invention provides pharmaceutical compositions, such as vaccines, comprising a CK-2 chemokine and an immunogen. The pharmaceutical compositions may be administered to an organism to enhance or activate an immune response to the immunogen. In another embodiment, the invention also relates to a novel screening method for identifying and/or isolating genes whose mRNA is rapidly degraded in a cell by identifying and/or isolating nucleic acids (for example, from a cDNA library) having one or more sequence motifs that are recognized by an endonuclease. The screening methods are particularly useful for identifying and/or isolating genes that encode novel chemokines, cytokines or oncogenes.Linvention concerne une nouvelle chimiokine, dorénavant chimiokine-2 ou CK-2, et notamment des modes de réalisation particuliers dérivés de poissons tels que la truite arc-en-ciel (Oncorhynchus mykiss). Linvention concerne de nouveaux polypeptides correspondant aux chimiokines CK-2, ainsi que des acides nucléiques codant pour une chimiokine CK-2 et des anticorps qui se lient spécifiquement à une chimiokine CK-2. Linvention concerne également des méthodes thérapeutiques pour utiliser les nouvelles chimiokines CK-2. Plus spécifiquement, linvention concerne des compositions pharmaceutiques, telles que des vaccins, qui contiennent une chimiokine CK-2 et un immunogène. Ces compositions pharmaceutiques peuvent être administrées à un organisme pour augmenter ou activer une réponse immunitaire à cet immunogène. Dans un au
