MASAO NAKAGAKI1), TOMOHIKO MORINAGA, CHUI-QIN ZHOU, ZENTA KAJIURA and RYUZO TAKEI: Increasing curves of two virus DNAs in the midgut epithelium of silkworm infected with Bombyx mori densonucleosis virus type 2 (BmDNV-2) Increasing curves of 6.1 and 6.6 kb DNAs of Bombyx mori densonucleosis virus type 2 (BmDNV-2) in the midgut epithelium infected with BmDNV-2 were investigated using a quantitative competitive PCR technique. The 6.1 and 6.6 kb DNAs in midgut epithelium increased logarithmically

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... th time, reaching a maximum titer of 500,000-fold at 48 h since the infection (h postinf ection, hpi). The maximum titer was maintained until 102 hpi after reaching the maximum. Two DNAs during larval ecdysis decreased to 1/625 of maximum titer, indicating that virus-infected cells have dropped out of midgut epithelium. Since increasing curves of two DNAs were very similar, each of two DNAs could be used as template DNA for BmDNV-2 detection by PCR. In insusceptible race of the silkwarm to BmDNV-2 disease, two virus DNAs increased until 12 hpi and then decreased rapidly, suggesting that some of viral DNAs have replicated and accumulated in midgut of the insusceptible race. The replication of 6.1 kb DNA went ahead of that of 6.6 kb DNA in sensitive and insusceptible races of the silkworm. It is suggesting that two DNAs could replicate independently.