FIG. 5.

Detection of neutralizing antibodies in sera from SIVagm3mc- and SIVagm3-X4mc-infected PT macaques against SIVagm3-X4mc or SIVagm3mc. The neutralization of SIVagm3mc (A) and SIVagm3-X4mc (B) infections by sera of PT macaques infected with SIVagm3mc (PT232 [▵]; PT7337 [○]) and with SIVagm3-X4mc (PT236 [▴]; PT6502 [•]) is shown. Neutralizing activity was measured in C8166 T cells as described in Materials and Methods. The titers are the reciprocal serum dilutions at which 50% of the cells were protected from virus infection (ND₅₀). ND₅₀ values below the detection limit were arbitrarily assigned the value of 35.