Addition of a UL5 helicase-primase subunit point mutation eliminates bursal–thymic atrophy of Marek's disease virus ∆Meq recombinant virus but reduces vaccinal protection

Figures & data

Figure 1. In vivo replication of MDV within PBLs in MD vaccinated, unvaccinated or 648A strain MDV challenged birds at 6, 13 and 20 days post vaccination. Panels A and B show two replicate experiments designated Trials 1 and 2, respectively. The “x” at 20 dpi for unvaccinated birds challenged with 648A indicates no data as there was high mortality around 2 weeks post infection.

Figure 2. Weight of lymphoid organs in vaccinated and unvaccinated birds at 15 dpv relative to total body weight in Trial 1 (Panel A) and Trial 2 (B).

Figure 3. Survival of vaccinated birds following challenge with vv+ 648A MDV. Panels A and B show data from the Trials 1 and 2, respectively. Data for birds vaccinated with bivalent vaccines were unavailable for Trial 2 due to flood causing complete loss of the isolator housing that lot.

Table 1. Vaccinal protection against challenge with 648A strain MDV.

	Trial	# MD + birds/total birds	MD (%)	PI
Unvaccinated	1	16/16	100	0
	2	17/17	100	0
∆Meq+UL5 p4	1	6/14	42	57
	2	10/18	56	44
∆Meq BAC p5	1	1/15	7	93
	2	1/18	6	94
∆Meq p40	1	0/14	0	100
	2	1/18	6	94
Bivalent (HVT+SB-1)	1	2/15	13	87
	2	n.d.	n.d.	n.d.
Rispens	1	0/15	0	100
	2	2/17	12	88

n.d., indicates no data available due to all birds lost due to a flood in the isolator.