Table 1.
Immune Responses and Postulated Viral Evasion Mechanisms or Interactions
| Host immune response | HCV | HIV-1 |
|---|---|---|
| Innate immunity | ||
| Activation of pathogen-associated molecular pattern via TLRs | Direct stimulation by single-stranded RNA elements17 | |
| Interferon signaling pathways | Core-mediated induction of SOCS3 NS3/4-mediated cleavage of CARDIF and TRIF NS5- or E2-mediated inhibition of PKR activity Reviewed in Chung et al11 |
Tat-mediated interference with PKR activity |
| NK cells | HCV E2 protein interference with NK receptors21 Aberrant cross talk with dendritic cells Reviewed in Golden-Mason and Rosen242 |
Altered expression of NK receptors Aberrant or decreased cytokine secretion Aberrant cross talk with dendritic cells Enhanced apoptosis Reviewed in Ianello et al20,243 |
| Regulators of adaptive immunity | ||
| Dendritic cells | Direct infection and altered function244 | Direct infection Decline in number and function Reviewed in Noursadeghi et al245 |
| Regulatory T cells | Suppression of antiviral responses Reviewed in Billerbeck and Thimme80 |
Suppression of antiviral responses Reviewed in de St Groth and Landay90 |
| Adaptive immunity | ||
| Neutralizing antibody responses | Mutational escape Reviewed in Stamataki et al246 |
Mutational escape Glycan shielding Altered complement Loss of potency with CD4 decline Suppressed class switching Reviewed in Moir and Fauci247 |
| Cell-mediated responses | ||
| T-helper cells (CD4) | Decreased function Exhaustion Apoptosis |
Direct killing Exhaustion Immune activation (producing more targets) Interference with MHC class II processing |
| Cytotoxic T cells (CD8) | Mutational escape Exhaustion Core-mediated down-regulation140 Reviewed in Bowen and Walker248 |
Mutational escape Exhaustion Nef-mediated endocytosis of MHC class I249 Vpu-mediated destabilization of MHC class I250 Reviewed in Goulder and Watkins251 |
NOTE. This table shows various examples of viral evasion mechanisms and does not detail every possible relevant finding or cite every relevant publication; we have included reviews for the reader when appropriate for further reading.
NS, nonstructural protein; MHC, major histocompatibility complex.