Vero cells of control group
Confluent monolayer of normal Vero cells at both unstained and stained (H& E stain) on 12 and 36 hr post seeding (Fig. 1, 2 &3) conditions are also shown for comparative study with same time category infected cells. Cells of all non-infected controls showed almost similar morphology in microscopic study. The cells were flattened, disc or fish scale shaped with almost rounded nuclei.
Morphology of cytopathic effect (CPE) in Vero cells by adapted PPRV isolates
In general, the cells become contracted and decrease in size over the time. Initial stage of cell rounding appeared at 12 hpi (Fig. 4 &10). As infection progressed, the cells become smaller; rounded, showed a thin peripheral layer of cytoplasm (Fig. 4). Detachment, rounding and aggregation of cells, at 24 hpi (Fig. 5) and at 36 hpi (Fig. 6). The affected cells fused to form small group or cluster or syncytia (Fig. 6) which in later transformed into large syncytia (Fig. 7 and 8) and finally the monolayer of cells were completely detached from floor of the cell culture flask (Fig. 9).
CPE produced in Vero cells on cover slip (stained with H & E) by PPRV
Vero cells of infected group:Cytoplasmic changes
Alterations in the cytoplasm began at 24 hpi. Initially, the cells showed a single, well defined, eosinophilic cytoplasmic mass adjacent to the nucleus (Fig. 11). The mass frequently displaced the nucleus to one side of the cell, and the cytoplasm of few adjacent cells come in contact (cytoplasmic fusion) and gathered together to form small syncytia consisting of approximately 3 cells (Fig. 11). As the infection progressed, the number of small syncytia increases up to 60 hpi. The syncytia increased in size with time and consisted of around 5 cells at 36 hpi (Fig. 12), around 10 cells at 48 hpi (Fig. 13), around 15 cells at 60 hpi (Fig. 14). Numerous deeply stained eosinophilic cytoplasmic granules varied in diameter and number were seen in cytoplasm of cell, termed as intracytoplasmic inclusion bodies (Fig. 15). In earlier study with BD_ PPR_2008, very few intracytoplasmic inclusion body was found at 72 hpi on 9th passage level (Fig. 19, collected from PhD Thesis, Rahman MM, 2013) but on 60th passage level the inclusion body increased in number and number varied between 6-8 at same time category (Fig. 15).
Vero cells of infected group: Nuclear Changes
A significant nuclear alteration at 60th passage level appeared at 36 hpi. The number of nuclei containing eosinophilic granules (inclusion body) was increased up to 60 hpi and thereafter maintained a steady state level. The eosinophilic granules were smaller in size and increased in number at the beginning of its appearance but at later stages the size of the inclusion became larger and number also reduced (Fig. 16 – 17). The number of small granules varied from 1 to 7 per nucleus, termed as intranuclear inclusion bodies. In the later stages, only one or two large granules per nucleus were present, and these were more round and deeply eosinophilic (Fig. 17 and 18). In very later stage (72 hpi) degradation of cells were observed (Fig. 18).