Figure 6

Marek’s disease virus-induced pathological consequences in chickens. A A comparison between the PBS control and ST-1^st treatment groups. Livers from the PBS control (A^A) group showed MDV-induced lesions, whereas those from the ST-1^st group did not show severe lesions (A^A’). In the intestine of the PBS control group animals, cancerous tumours were visible (A^B), but tumours were absent in the ST-1^st group (A^B’). Tumour-like projections were visibly attached to feather bases in both groups (A^C & A^C’). B Histopathological examination. Organ specimens were collected from infected chickens in each group (n = 2) at 6 weeks post-infection and subjected to H & E staining. MDV-induced cancerous transformation was notably evident in the spleen and liver. Aggregation of infiltrated lymphocytes was prominent in lung and intestinal tissues. Delayed symptom development was evident in the ST-1^st group, showing the effectiveness of CRISPR/Cas9 delivery before MDV infection. Yellow arrowheads depict MDV-induced cancerous transformation (spleen and liver) and lymphocyte aggregation in the lungs and intestine.