Multiple choice Which immune marker is observable during the window period of HIV infection? Antigen p17 Antibodies to gp 41 Antibodies to gp 120 p24 antigen GSK-3 Reveal answer Fill a bubble to check yourself E Correct answer Explanation Glycogen synthase kinase 3 is a serine/threonine protein kinase that mediates the addition of phosphate molecules onto serine and threonine amino acid residues.