Anti-UGV NP IgM antibody titres showed a trend to lower in the older BIBD-negative snakes, which could reflect exhaustion of the immune system or a gradual class switch towards IgY.
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The sentences
We include the graphic representation ( Fig 3B ) as the result may indicate an interesting trend of UGV-1 IgM remaining at higher levels for BIBD-positive animals because of continuous exposure from circulating virus while in BIBD-negative snakes, lack of such exposure may lead to UGV-1 IgM reduction in older animals.