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Twenty clones were isolated from cultured Aedes albopictus (Singh) cells in the presence of anti-Chikungunya (CHIK) virus serum. Each clone was tested for its yields of Dengue (DEN) viruses, types 1, 2, 3 and 4, and also CHIK virus. Clone C6 showed the highest yield of each virus tested. Forty-three clones obtained by recloning C6 in the presence of anti-DEN sera showed almost the same virus yields as C6. One of the clones, C6/36, showed mild to extensive cytopathic effects several days after virus infection, in contrast to the original uncloned (SAAR) cells. Fluorescent antibody staining revealed that the amount of virus antigen accumulated in the cytoplasm was almost the same in every cell in the case of clone C6/36, while it was highly heterogeneous for uncloned SAAR cells. Growth curves of the viruses indicated that clone C6/36 gave a significantly higher yield for each virus than uncloned SAAR cells up to 7 days after infection. Virus sensitivity of the C6/36 clone did not change by growing the cells with the medium used for uncloned SAAR cells, nor did the virus sensitivity of uncloned cells increase in medium used for clone C6/36. However, the C6/36 clone became resistant to CHIK virus, but not to DEN or Sindbis viruses, after incubation with the medium used for another A. albopictus cell line (SAAK). The transfer of the specific resistance to CHIK may be mediated by some latent virus related to CHIK.
A. Igarashi (Fri,) studied this question.