Transformation of Primary Cultures of Shrimp (Penaeus stylirostris) Lymphoid (Oka) Organ with Simian Virus-40 (T) Antigen

Primary cultures of lymphoid (Oka) organ from Penaeus stylirostris were transformed with naked or Lipofectin-mediated pSV-3 neo, a shuttle vector containing the tumor (T) antigen gene from Simian virus-40. The transformed cells, OKTr-1 and OKTr-23, exhibited the following characteristics: rounded morphology forming grapelike aggregates, loosely adhesive, increased growth rate in Medium-199, resistance to G-418 (a neomycin analog marker in the shuttle vector), cloning efficiencies of 68.7% and 36.7% in soft agarose, respectively, and stability in liquid nitrogen storage. Immunofluorescence staining (IFA) of the transformed cells using a monoclonal antibody against SV-40 tumor antigen showed positive results. In contrast, primary cell cultures exhibited fibroblast-like morphology and formed a tight, adhesive monolayer on the surface of the culture vessel. They were sensitive to G-418, and showed negative results with IFA. To date, OKTr-1 and OKTr-23 have undergone 44 and 18 passages, respectively. Primary cultures of the lymphoid organ have not been successfully passaged beyond the primary stage.