Binding properties and infectivity of CD4-dependent (IIIB) and CD4-independent (IIIBx) strains of HIV-1.

<p>(<b>A, B</b>) Superimposed sensorgrams (acoustic biosensor) of fluid phase IIIB (<b>A</b>) and IIIBx (<b>B</b>) viral particles (34–250 nM determined by p24 ELISA and normalized assuming 2500 gag proteins per virion) binding to immobilized DC-SIGN. K_D values are indicated. (<b>C, D</b>) Binding of IIIB and IIIBx to THP-1 (<b>C</b>) and THP-1 DC-SIGN (<b>D</b>) cells. Virus was incubated with cells for 2 h and after washing and cell lysis, p24 levels were estimated. Experiments were repeated twice, each point in triplicate. (<b>E</b>) Infection (10⁻⁴ MOI) by IIIB and IIIBx of THP-1 DC-SIGN and THP-1 cells represented as concentration of p24 antigen released in the supernatant. (<b>F</b>) Data from (<b>E</b>) as fold-increase in infection relative to THP-1. IIIBx infection level was significantly lower than IIIB (**, P = 0.001). Experiments were repeated twice (5 replicates).