Table 1.
Host factors determining viral tropism
| Determinants of viral tropism | Example | Factor(s) involved | Type of tropism | Refs |
|---|---|---|---|---|
| Cell surface binding or entry receptors | HIV-1 | Presence of CD4, CCR5 and CXCR4 receptors on T cells required for cell entry | Cellular | 3,4 |
| Antiviral signalling by cytokines | Myxoma virus | ERK-dependent type I IFN signalling restricts productive infection | Host and cellular | 39 |
| Availability of host factors | Hepatitis B virus | The nuclear hormone receptors hepatocyte nuclear factor 4 and retinoid X receptor-α as well as peroxisome proliferator-activated receptor-α, which positively regulate viral RNA synthesis, are enriched in the liver | Tissue and cellular | 118 |
| Route of entrance | Influenza A virus | Trachea and bronchi | Cellular | 119 |
| Cell lineage | Influenza A virus | Lung cells | Cellular | 69 |
| Activation state of the cell | Parvovirus H-1 | Constitutive production of higher levels of nitric oxide and superoxide anion resticts virus infection | Cellular | 120 |
| CCR5, CC-chemokine receptor 5; CXCR4, CXC-chemokine receptor 4; ERK, extracellular signal-regulated kinase; IFN, interferon. | ||||