**2.3 Factors influencing the recurrence of HCV and graft survival**

The course of post-transplant hepatitis C is determined by the interaction of various factors. Certain pre-transplant factors in the recipient are associated with worse evolution, including female sex, older age, and the presence of diabetes or the metabolic syndrome (Firpi et al 2004, Gallegos-Orozco et al, 2009, Pagada et al 2009, Pérez et al 2011). Other pre-transplant factors depend on the virus, for example the genotype HCV 1b, a high pre-transplant viral load, the absence of response to antiviral therapy and coinfection with HIV have also been associated with a worse prognosis (Berenguer et al, 2005).

Other factors, related with the donor and the peri-operative period, can also affect the severity and the time to relapse of post-transplant HCV infection, such as an older donor age (>50 years), a high degree of steatosis in the donor liver, a prolonged ischaemia time, a non-heart beating donor, a living donor, preservation injury, a partial split graft, or anti-HCV positive donors, all of which have been associated with a worse evolution (Pérez-Daga et al, 2006, Machicao et al 2004;. Pine et al 2009; Humar et al 2005)

Notable among the post-transplant factors is the metabolic syndrome, present within the first 12 months in around 50% of all patients who receive a transplant due to HCV infection and which is associated with greater progression of the fibrosis. Thus, the importance of control of factors like dyslipidaemia, hypertension and, more importantly, diabetes associated with insulin resistance, all of which play a crucial role in the evolution of the recurrence of post-transplant HCV infection (Hanouneh et al., 2008, Gallegos-Orozco et al, 2009).

Recent studies appear to show that polymorphisms in the interleukin 28 B gene (*IL-28B*), in both the donor and the recipient, may influence not only the response to antiviral therapy but also the evolution of hepatitis C due to post-transplant HCV reinfection, with a worse evolution in those with the genotypes CT and TT (of the polymorphism rs12979860) as compared with the genotype CC (Charlton et al, 2011, Brocato et al, 2010).
