The VG/GA strain of Newcastle disease virus: mucosal immunity, protection against lethal challenge and molecular analysis

Figures & data

Table 1.  NDV vaccine-challenge trial local and systemic humoral immunity, and protection against lethal challenge

Group	Age
	14 days			21 days			28 days^c			42 days
	ELISA^a titres	Trachea^b	Bile	ELISA titres	Trachea	Bile	ELISA titres	Trachea	Bile	Challenge results: number of dead (% protection)
		NDV IgA	IgA		NDV IgA	NDV IgA		NDV IgA	NDV IgA
VG/GA day 1	134^A	0.45^B	0.93^A	403^B	1.02^B	1.16^A	1172^B	1.21^B	1.96^A	1/19 (95%)
VG/GA days 1 + 14	62^A	0.41^B	1.01^A	261^C	1.04^B	1.57^A	1865^A	1.18^B	2.41^A	0/18 (100%)
VG/GA day 14	25^A	0.05^C	0.02^C	47^C	0.19^C	0.31^B	952^B	0.90^B	1.40^B	0/20 (100%)
La Sota day 1	271^A	0.80^A	0.42^B	1049^A	1.33^A	0.42^B	1578^A	1.76^A	1.04^B	0/19 (100%)
La Sota days 1 + 14	209^A	0.72^A	0.39^B	1231^A	1.23^A	0.57^B	1913^A	1.98^A	1.27^B	0/19 (100%)
La Sota day 14	5^A	0.02^C	0.06^C	483^C	0.65^B	0.21^C	874^B	1.82^A	0.42^C	0/19 (100%)
VG/GA day 1 + La Sota day 14	92^A	0.40^B	1.01^A	437^B	0.72^B	1.81^A	1514^A	1.44^B	2.13^A	0/20 (100%)
La Sota day 1 + VG/GA day 14	216^A	0.74^A	0.48^B	547^B	1.44^A	1.74^A	1485^A	1.67^A	2.29^A	1/19 (95%)
Control challenged	24^A	0.05^C	0^C	22^C	0.07^C	0^C	42^C	0.05^C	0.1^C	9/9 (0%)
^aEight birds per group were tested and results are expressed as the geometric mean of the ELISA titres. ^bFour birds per group were sampled for local immunity; results are expressed as the average of the corrected optical densities. ^cBirds were challenged with a lethal dose of Texas GB strain at 28 days of age and observed for 14 days. The same uppercase capital letters within columns indicate no significant differences (P<0.05).

Figure 1.  Newcastle disease ELISA serology. Results are expressed as the geometric mean of the ELISA titres (GMT). No statistical differences were observed between the vaccine strains. Both differed P < 0.05 from the non-vaccinated control.

Figure 2.  Mucosal immunity measured as IgA levels in SPF birds. 2a: IgA levels in tracheal washings. 2b: IgA levels in intestinal washings. 2c: IgA levels in bile. Results are expressed as the corrected optical density at 650 nm (COD650).

Table 2.  RT-PCR detection of virus tissue distribution

RT-PCR treatment	Organ
	1 day post inoculation				4 days post inoculation				7 days post inoculation				11 days post inoculation				15 days post inoculation				21 days post inoculation
	T	L	D	Ct	T	L	D	Ct	T	L	D	Ct	T	L	D	Ct	T	L	D	Ct	T	L	D	Ct
VG/GA	−	−	+	−	+	+	+	+	+	+	+	+	−	−	+	+	−	−	−	+	−	−	−	−
La Sota	+	−	−	−	+	+	−	−	+	+	−	−	+	+	−	−	−	−	−	−	−	−	−	−
Control	All tissues negative
Samples from four birds where obtained and pooled each day. T, trachea; L, lung; D, duodenum; Ct, caecal tonsil; +, RT-PCR-positive signal (250 base pair amplicon); −, no amplification.

Figure 3.  Full nucleotide phylogeny of the VG/GA strain of NDV. The VG/GA strain grouped among the class II genotype II viruses, which corresponds with most of the classic poultry vaccine strains.

Table 3.  Amino acid changes among VG/GA and La Sota strains of NDV.

Protein	Amino acid La Sota	Residue position	Amino acid VG/GA
HN	G	169	R
	Y	203	H
	S	324	T
	V	495	E
	T	522	I
F	V	106	M
	I	135	M
	T	136	A
	V	255	I
M	G	29	D
	L	48	S
	I	104	V
	I	114	M
	V	196	I
N	M	389	R
	K	390	R
	D	401	E
	D	402	V
	I	407	D
P	E	8	D
	F	109	L
	P	164	L
	T	317	I
	K	352	R
L	P	18	S
	Q	97	E
	M	187	I
	K	191	R
	T	253	M
	T	305	I
	S	897	P
L (V domain)	CHLTFTYPMILKGCSLKKESKRGMWFTNRV	1287 to 1316	VSPYIHISNDSQRLFTEEGVKEGNVVYQQI
	V	1366	A
	S	1385	L
	E	1620	G
	I	2103	K