In a hepatitis B vaccination study in ART-treated HIV-1-infected adults, significantly elevated plasma levels of CXCL13 were measured in vaccine non-responders compared to responders; among responders, CXCL13 levels were negatively associated with anti-HBs levels, suggesting that pre-existing GC hyper-activation could impair vaccine responses during HIV-1 infection (29). Here, CXCL13 is linked to HIV-1 infection.