HS GAGs Syndecan-4 (in cis) HA of Influenza virus HN of avian Newcastle disease virus, Sendai virus and human parainfluenza virus PDGF-DD Nidogen-1 PCNA NKp44L expressed on tumor cells, bystander CD4+ T cell during HIV infection, or cartilage-derived chondrocytes Domain III envelope protein from West Nile and Dengue viruses Unknown ligand(s) on Mycobacterium tuberculosis, M. bovis, Nocardia farcinica and Pseudomonas aeruginosa. Here, SDC4 is linked to HIV infectious disease.