In vitro infection of lymphocytes with Marek's disease virus

Suspension cultures of splenic lymphocytes, incubated at 41 degrees C, became infected with Marek's disease virus (MDV) following exposure to a) other infected lymphocytes, b) infected chicken kidney monolayer cultures, or c) cell-free MDV. Both viral antigen expression and virus isolation could be demonstrated after more than 40 passages made by the addition of fresh spleen cells at 2- to 3-day intervals. Susceptibility of spleen cells from bursectomized chickens was markedly lower than that of cells from intact birds. Furthermore, when spleen cell suspensions were depleted of cells having characteristics of bursa-derived cells, e.g., those with surface IgM, Fc receptors, or ability to adhere to nylon wool, the susceptibility of the cell suspension was diminished. Enrichment of the suspension with cells having those features enhanced overall susceptibility. The target cells for virus infection in vitro also were shown to be nonphagocytic, to be of low or medium density, and to bear Ia-like antigen. In vitro susceptibility to infection of spleen cells did not correlate with the genetic susceptibility of the donor to Marek's disease.