Characterization of homologous and heterologous adaptive immune responses in porcine reproductive and respiratory syndrome virus infection

Table 6 Viral neutralization test results using PRRSV strains 3262 and 3267

	Nº of responding pigs; mean titre (log₂ ) and standard deviation Range of titres (log₂ ) for positive pigs
	Strain used in the viral neutralization test
	3262				3267
	Days post-inoculation				Days post-inoculation
Challenge group†	21	42	84	98	21	42	84	98
A + A	0/4	0/4	0/4	0/4	0/4	3/4*	4/4*	4/4*
(3262+3262)	-	-	-	-	-	1.7 ± 0.6^a	2.0 ± 0.8^a	4.25 ± 1.0^b
						(1–2)	(1–3)	(3–5)
A + B	0/4	0/4	0/4	0/4	0/4	2/4	2/4	4/4*
(3262+3267)	-	-	-	-	-	1.0 ± 0.0^a	2.0 ± 0.0^a	5.3 ± 0.5^b
						(1–1)	(2–2)	(5–6)
C1 + B	0/2	0/2	0/2	0/2	0/2	0/2	0/2	2/2*
(C+3267)	-	-	-	-	-	-	-	2.5 ± 0.5
								(2–3)
B + B	0/4	2/4	4/4‡	4/4‡	4/4‡	4/4	4/4	4/4
(3267+3267)	0/4	1.0 ± 0.0	2.2 ± 1.5	2.8 ± 1.7	2.0 ± 0.8^a	2.5 ± 1.0^a	4.8 ± 1.0^b	6.0 ± 0.8^b¶
	-	(1–1)	(1–4)	(1–5)	(1–3)	(2–4)	(4–6)	(5–7)
B + A	0/3	0/3	3/3‡	3/3‡	1/3	3/3	3/3	3/3
(3267+3262)			2.0 ± 1.0	1.3 ± 0.6	1.0 ± 0.0	3.0 ± 1.0^a	4.0 ± 1.0^a	5.3 ± 0.6^b
	-	-	(1–3)	(1–2)	(1–1)	(2–4)	(3–5)	(5–6)
C2 + A	0/3	0/3	0/3	0/3	0/3	0/3	0/3	0/3
(C+3262)	-	-	-	-	-	-	-	-

† Chronological sequence of strains used for inoculation is shown in parentheses.
* The asterisk show statistical differences (p < 0.05) for the proportion of responding pigs using one or the other PRRSV strain.
Superscript letters indicate statistical differences (p < 0.05; ¶ p = 0.08) in the average titres between different days using a given strain.
‡ The symbol indicates statistically significant differences for the proportion of responding pigs for similar groups between experiments (i.e. homologous A + A vs. homologous B + B) using the same strain.

ISSN: 1297-9716