Generic method for imaging transgene expression.

We propose a generic method to report on gene expression based on the use of an antigen-antibody reporting system and visualization by MRI. This methodology was demonstrated using a truncated form of the H2K(k) antigen, tH2K(k), as the nonendogenous antigen to be imaged. HeLa cells, transfected to express tH2K(k), exposed to tH2K(k) antibodies conjugated to a superparamagnetic iron oxide particle, generated strong negative contrast compared to non-H2K(k) expressing cells by MRI. T(2) of the tH2K(k) expressing cells was 57.6 +/- 17.0 ms, compared to 424.0 +/- 38.7 and 445.4 +/- 47.2 ms for the mock transfected and nontransfected cells, respectively (P < 0.001). tH2K(k) expression in the former cells was confirmed by flow cytometry, fluorescence, and electron microscopy. The methodology can be adapted to image in vivo other nonendogenous antigens in cells/tissues.