We and others have considered a cutoff point of more than 2 simultaneously expressed markers to demonstrate poly-functional characteristic of responding T-cells [16, 17] . Figure 5c shows a comparison between average frequency of intra-hepatic viralspecific responses within the pool of CD8 + T-cell populations expressing 2 markers or less, and those within the pool of populations expressing more than 2 markers simultaneously. For both HCV and HIV-specific CD8 + T-cells the majority of responses had two or less functions. However, intra-hepatic HIV-specific responses demonstrated more poly-functionality, compared to HCV-specific responses either within co-infected or mono-infected individuals [0.0560.01 vs 0.00760.00, p,0.05; HIV-specific responses vs HCV-specific responses in HCV/HIV co-infected group]; [0.0560.01 vs 0.0160.00, p,0.05; HIVspecific responses in HCV/HIV co-infected group vs HCVspecific responses in HCV mono-infected group]. In summary, although viral-specific T-cells, simultaneously expressing all 5 measured markers were rarely found in the liver, intra-hepatic HIV-specific T-cells showed greater functional capacity when compared to those being HCV-specific.