Table 1.

Determination of the MID^p=0.98 of EIAVΔS2, Using Poisson Distribution Mathematics and Empirical Data^*

	Input amount of EIAVΔS2 (PERT-predicted TU): a	Observed number of negative replicates: b	p [negative]: c	Calculated IU present: d=−ln (c)*	Correction factor: e=3.912/d	Calculated input of EIAVΔS2 for p=0.98 (PERT-predicted TU): x=a×e
Empirical data	0.313	1/8	0.125	2.080	1.88	0.589
	0.078	5/8	0.625	0.470	8.32	0.649
	0.020	7/8	0.875	0.134	29.19	0.584
Target	x	2/100	0.02	3.912	1	x=0.61**

EIAVΔS2, EIAV mutated to include two stop codons, so as to stop potential downstream translation initiation within S2; IU, infectious units; p, probability of infection; PERT, product-enhanced reverse transcriptase; TU, transducing units.

^*The target dose of virus that enables a 98% infection rate is 3.912 IU according to Eq. (8) (see Materials and Methods), which considers the number of negative outcomes likely at this dose, in this case 2/100 or p=0.02. Three sets of replicate 92BR cultures inoculated with a 4-fold serially diluted stock of EIAVΔS2 (a) resulted in observed negative outcomes presented as a fraction of the experimental set (b); this can also be expressed as a probability of noninfection (c). Using Eq. (8), the number of infectious units present in the inoculums enabling the observed infection rate is calculated (d). The correction factor (e) required to achieve a dose of 3.912 IU allows the calculation of the target dose (x) of virus in arbitrary units (in this case PERT-predicted TU).

^**Average calculated value (x) to 2 dp.