In situ hybridization vRNA patterns in secondary lymphoid tissues in chronically SIV-infected RMs. In situ hybridization signal at (A) low magnification and (B) high magnification within the secondary lymphoid tissue shows 2 distinct and distinguishable patterns: (1) FDC-trapped virions showing a typical “lattice-like” diffuse vRNA pattern, and (2) productively infected vRNA⁺ T cells showing a strong intense spherical staining pattern. Follicles are outlined in red. Red arrows indicate productively infected SIV vRNA⁺ cells. Scale bars represent 50 μm.