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          IL-21         |  
      | Vaxjo ID | 251 |  
      | Vaccine Adjuvant Name | IL-21 |  
      | Alternative Names | Interleukin-21 |  
      | Adjuvant VO ID | VO_0005738 |  
      | Description | A pleiotropic cytokine critical for T follicular helper (Tfh) cell development, germinal center (GC) responses, B cell help, and antibody production. In this study, IL-21 was used as an immunotherapy to boost influenza vaccine responses in aged SIV+ macaques |  
      | Stage of Development | Research |  
      | Host Species for Testing | Macaque |  
      | Structure | Recombinant IL-21 fused with an IgFc domain to enhance half-life and delivery. |  
      | Preparation | Administered subcutaneously at 50 µg/kg on days −2, 0, and +7 relative to each influenza vaccination dose. |  
      | Dosage | 50 µg/kg subcutaneously Administered 3 times per vaccination cycle (days −2, 0, +7) |  
      | Function | We conclude that IL-21 enhances flu vaccine-induced Ab responses in SIV+ aged RM acting as an adjuvant modulating LN germinal center activity. Strategies to supplement IL-21 in aging could be a valuable addition in the toolbox for improving vaccine responses in an aging HIV+ population. |  
      | Safety | Well-tolerated in SIV-infected aged macaques |  
	  | References | Kvistad et al., 2021: Kvistad D, Pallikkuth S, Sirupangi T, Pahwa R, Kizhner A, Petrovas C, Villinger F, Pahwa S. IL-21 enhances influenza vaccine responses in aged macaques with suppressed SIV infection. JCI insight. 2021; 6(20); . [PubMed: 34491910]. |  |