FIG. 4.

Increased numbers of virus-infected macrophages in the LNs of animals receiving cell-associated virus. Combined ISH and IH data for the draining LNs of six representative animals, biopsied 14 days after injection of cell-associated versus cell-free SIV, are shown. Animal I686 received wild-type virus (wt)-infected DCs, J995 received wild-type virus-infected T cells, AR 70 and G402 were injected with cell-free wild-type virus, and AR 80 and AT 88 were i.v. infected with wild-type virus. Frozen tissues were processed for IH against the indicated markers (red), counterstained with hemalaun (purple-blue), and followed by ISH for SIV RNA (black grains). Small CD4⁺ T cells (arrows, I686), large CD4⁺ cells (macrophages or activated T cells; asterisks, I686), and CD169⁺ and CD68⁺ macrophages (arrowheads, I686 and J995) that are positive for SIV are apparent in animals injected with either DC- or T-cell-associated SIV. SIV-positive cells are negative for the DC markers CD208 (I686 and J995) and CD1a (J995). The SIV-positive cells in AR 70 and G402 lacked CD169 but expressed CD4 (asterisk). The CD4⁺ cell expressing SIV in the example shown for AR 70 appears to be intermediate in size and is thus difficult to definitively identify as either a T cell or macrophage. SIV-positive cells in the cell-free SIV-infected i.v. controls (AR 80 and AT 88) are smaller CD4⁺ cells (arrow) with few CD68⁺ cells (arrowhead) that lack CD169. Magnifications, ×40 (CD1a and CD208 panels of J995) and ×100 (all other panels).