INTERACTION BETWEEN HUMAN T-LYMPHOTROPIC VIRUS TYPE I AND OTHER ONCOGENIC INFECTIONS IN THE MIYAZAKI COHORT STUDY

Abstract

P100 We have examined the effect of co-infection of human T-lymphotropic virus type I (HTLV-I) with other oncogenic pathogens, namely hepatitis C virus (HCV) and Helicobacter pylori, in the Miyazaki Cohort Study. With regard to the natural history of HCV-associated liver disease, the impact of HTLV-I infection may depend on the stage of progression of liver damage. A negative interaction has been observed between the two viruses in relation to elevated alanine aminotransferase level (synergy index (SI)=0.5); conversely, a strong positive interaction has been seen with respect to co-infection and liver cancer death (SI=2.3). HTLV-I infection could lead to an ineffective resolution of concomitant HCV infection, with apparent promotion of hepatocarcinogenesis. Of note, the presence of antibody to HCV has been found to be associated with increased immune suppression among HTLV-I carriers in the study cohort, as indexed by diminished response to the purified protein derivative. HTLV-I status does not appear to affect antibody positivity to H. pylori, which is high in this population (70%). However, a strong inverse association between reported ulcer and HTLV-I positivity is observed (odds ratio=0.53), independent of H. pylori status. In summary, these observations suggest that HTLV-I may modify the natural history of other persistent infections and point to the need to clarify the role of host cellular immune response.