TABLE 3.

Infectious titers of rNDV incubated in pH 7.0 buffers of different ionic strengths as measured by FFA^a

Method no.	Predilution concn of stock rNDVa in bufferb	Final buffer compositionc ,d	Ionic strength (M)	Serial dilution buffer for FFA set up with initial 90-min incubation	Final titer (log10 FFU/ml) corrected for dilutione	Difference from stock titer (log10 FFU/ml)
2	1:50 in buffer A	Buffer A0	0.011	Buffer A	8.89 ± 0.06	−0.43
	1:10 in buffer A	Buffer A1	0.025	Buffer A	8.93 ± 0.08	−0.40
	1:10 in buffer B	Buffer B1	0.160	Buffer B	9.27 ± 0.12	−0.06
	1:10 in buffer C	Buffer C1	0.475	Buffer C	9.06 ± 0.11	−0.27
3	1:50 in buffer A	Buffer A0	0.011	VCGM	9.21 ± 0.06	−0.11
	1:10 in buffer A	Buffer A1	0.025	VCGM	9.25±0.11	−0.08
	1:10 in buffer B	Buffer B1	0.160	VCGM	9.29 ± 0.10	−0.04
	1:10 in buffer C	Buffer C1	0.475	VCGM	9.18 ± 0.07	−0.15
	None (stock)	VCGM	0.181	VCGM	9.33 ± 0.10

^aStock rNDV was stored frozen at −80^°C in 20 mM phosphate containing 150 mM NaCl and 10% (wt/vol) sucrose at pH 7.0 and thawed shortly prior to dilution and sample preparation for FFA.

^bCompositions of dilution buffers A, B, and C are described in “rNDV sample preparation” in Materials and Methods.

^cpH 7.0.

^dCompositions of final buffers A₀, A₁, B₁, and C₁ (resulting from dilution of stock rNDV into buffers A, B, and C) are described in “rNDV sample preparation” in Materials and Methods.

^eMean and standard deviation values obtained from four independent incubation of samples (inoculum) with cells, including two samples incubated at 75 μl and the other two at 100 μl; n = 4.