Since CD4 is the high-affinity receptor for HIV-1, molecules such as CD4-IgG2, which incorporate the gp120 binding region of CD4, have the potential to bind and neutralize all strains of the virus. [AS PER AMENDMENT 4/25/00: Study results have demonstrated that the product is safe in children, well tolerated, and may have antiviral properties. With these encouraging results in hand, an extra cohort has been added using twice the dose of rCD4-IgG2 as in Cohort I.]