ITIH4 and viral infectious disease: This view was further substantiated by observations that SP-D levels are increased in the broncho-alveolar fluid of HIV-1 patients (27); and recombinant forms of SP-D (rfhSP-D) can bind to gp120 of HIV-1, acting as a potent inhibitor of viral infection in vitro via inhibition of the interaction between CD4 and gp120 (10).