MHC polymorphism of common carp. Link with disease resistance.
Krzysztof Rakus is appointed as ‘sandwich’ PhD between the Cell Biology & Immunology group and the Institute of Ichthyobiology & Aquaculture of the Polish Academy of Sciences (IIA-PAS). He started his research in 2002. The IIA-PAS holds a carp live gene bank that contains 19 breeding lines with considerable genetic variation in survival under pond conditions (9-68% survival at one year of age).
Common carp in Central Eastern Europe are cultivated in natural ponds on a semi-intensive scale and are vulnerable to diseases caused by a wide range of pathogenic organisms. The recognition of farming ponds as valued ecosystems argues against pharmacological interventions and strongly in favour of sustainable approaches, such as genetic selection for increased resistance to disease. This could be achieved by improving the immune capacity of carp by genetic selection. Genes of prime interest for marker studies are the major histocompatibility complex (MHC) genes. MHC genes are polymorphic in carp. We hypothesize that selecting carp lines for particular MHC alleles allows for an increased survival rate.
The MHC class I and class II molecules present peptides to cells of the immune system. In general, class I molecules bind endogenous peptides, whereas class II molecules bind peptides derived from exogenous proteins. The presentation of non-self peptides triggers a cascade of responses leading to the ultimate removal of the pathogen from which these non-self peptides were derived. Several hypotheses exist to explain the vast polymorphism of the MHC genes, e.g. heterozygous advantage, overdominant selection and balancing selection. Pathogen driven selection probably favours polymorphism of MHC genes through both heterozygote advantage and balancing selection.
- Differences in survival rate of carp grown in ponds (as established during the past 10 years) can be caused by many factors, among those are genetic differences in disease resistance. The first aim is to investigate the use of Trypanoplasma borreli infections under laboratory circumstances as a model for genetic differences in survival rate under pond conditions. A selection of 4 carp lines with a record of high survival and 4 lines showing low survival will be used to this purpose.
- MHC class II genes of carp are polymorphic as suggested by preliminary studies using SSCP profiles. How do the MHC class II alpha and beta genes segregate? These studies will be extended to the establishment of MHC class I polymorphism.
- Can correlations be established between carp lines with a record of high or low survival (cq. high or low resistance to T. borreli) and particular MHC polymorphisms and can these differences between carp lines in high or low survival rate/disease resistance unequivocally be correlated with the above-studied MHC alleles as detected in backcrosses?