SYNCYTIUM FORMATION IN CULTURED HUMAN LYMPHOID-TISSUE - FUSION OF IMPLANTED HIV GLYCOPROTEIN 120/41-EXPRESSING CELLS WITH NATIVE CD4(+) CELLS

While glycoprotein gp120/41 clearly causes HIV-infected cells to form syncytia in monolayers and in suspension, there is unfortunately scant knowledge on syncytium formation in tissues, We implanted gp120/41-expressing cells labeled with fluorescent particles inside blocks of human lymphoid tissue kept in long-term histoculture. Observed by confocal microscopy, together with immunohistochemical and morphological analysis of implanted cells, more than one-third of these gp120/41-expressing cells fused with native CD4(+) cells of the host tissue, yielding small (three to five nuclei) syncytia, Such widespread fusion of gp120/41-expressing cells in tissue in vitro, together with the finding of increased virulence of syncytium-inducing isolates of HIV, support the hypothesis that syncytium formation within lymph tissue of HIV-infected individuals contributes to AIDS pathogenesis.(1-4) This system and the methods developed may provide a way to study HIV-infected cells inside the very tissue whose destruction may prevent immune system repopulation.