HIV-1 pseudotypes, including envelope-deficient pseudotypes enter BeWo cells. A) BeWo-CD4+ cells were exposed to 20 ng/ml of p24 antigen of the HIV-1 pseudotypes at 37°C or 4°C by one hour spinoculation and one hour incubation at according temperature; the cells were washed, treated with pronase to eliminate residual virions on the cell surface, and the cell pellet was lysed in preparation for p24 antigen detection in lysates. Experiments were repeated at least three times. Graph shows a representative experiment. B) Wild type BeWo cells and CD4 expressing BeWo cells were exposed to HIV-1 pseudotypes. Viral entry was determined by p24 antigen quantification in cell lysates. The bars indicate the mean of at least three independent experiments; the error bars indicate SEM.