Yonas Bekele [1,2], DesalegnYibeltal [2,3], Kidist Bobosha , Temesgen E Andargie , Mahlet Lemma [1,2], Meseret Gebre , Anna Nilsson , Abraham Aseffa , Rawleigh Howe , Francesca Chiodi 
Affiliates:  Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm.  Armauer Hansen Research Institute (AHRI), P.O. Box 1005, Addis Ababa, Ethiopia.  Department of Pharmacology, School of Medicine, Addis Ababa University, Addis Ababa.  All Africa Leprosy, Tuberculosis and Rehabilitation Training (ALERT) center, Addis Ababa.  Department of Woman and Child Health, Karolinska Institutet, Stockholm.
HBV vaccine has 95% efficacy to prevent HBV infection and related cancer. We conducted a prospective study in HIV-1 infected children receiving ART (n=49) and controls (n=63) to assess humoral and cellular responses to HBV vaccine provided with three doses under an accelerated schedule of 4 weeks apart.
The levels of HBV vaccine antibodies and CXCL13, a chemokine mediating homing of B cells to germinal centers, were measured prior to vaccination and at 1 and 6 months post-vaccination. Circulating T follicular helper cells (cTFh) cells were characterized in blood; the capacity of these cells to respond to stimulation with HBV proteins was evaluated by cytokine expression (IFN-, IL-2, IL-4 and IL-21).
At 1 month post-vaccination all children, except 4 HIV-1 infected, displayed protective antibody (ab) titers to HBV vaccine; ab titers were lower in infected children (P<0.0001). Ab titers decreased (P<0.0001) in both HIV-1 infected and control children at 6 months. The frequency of cTFh cells was 20.3% for controls and 20.8% for infected children prior to vaccination and remained comparable post-vaccination. Cytokine expression by cTfh cells upon activation with HBV antigen was comparable in the two groups at baseline and 1 month post-vaccination. Higher plasma levels (P<0.0001) of CXCL13 were found in infected children which correlated with cTfh cell frequency at baseline.
A lower ab response to HBV vaccine was measured in HIV-1 infected children. The frequency and activation profile of cTfh cells was comparable in infected children and controls suggesting that cells other than Tfh cells are responsible for impaired ab response to HBV vaccine.