PD-1 antagonists are disclosed that can be used to reduce the expression or activity of PD-1 in a subject. An immune response specific to an infectious agent or to tumor cells can be enhanced using these PD-1 antagonists in conjunction with an antigen from the infectious agent or tumor. Thus, subjects with infections, such as persistent infections can be treated using PD-1 antagonists. In addition, subjects with tumors can be treated using the PD-1 antagonists. In several examples, subjects can be treated by transplanting a therapeutically effective amount of activated T cells that recognize an antigen of interest and by administering a therapeutically effective amount of a PD-1 antagonist.

The present invention provides a peptide with sequence of DEAQETAVSSHEQD, a fragment of rabbit-1 antiproteinase F, and its derivatives DEAQETAVSSHEQ and QETACSSHEQD, which significantly inhibit serum-borne HCV replication in hADSC and human hepatocytes.

The present disclosure provides rapid and non-invasive methods for determining whether a patient will benefit from treatment with therapeutic agents that inhibit Hepatitis C virus (HCV). These methods are based on detecting HCV RNA and/or anti-HCV antibodies in small-volume dried biological fluid samples that are collected using a microsampling device. Kits for use in practicing the methods are also provided.