TABLE 5.

Identification of the minimal CD4⁺ T-cell epitope recognized by C97 Th-cell clones

Peptide	Amino acid sequencea	SIe
		4C9f	3G5f
Expt 1
P1	DQEVIIDEQTGLPIKSHDYSEKPSVIYKPS	20.7	51.8
P1-1	DQEVIIDEQTGLPIKS	31.2	52.9
P1-2	PIKSHDYSEKPSVIY	1.4	1.1
P1-3	EQTGLPIKS	0.9	1.1
P1-4	DEQTGLPIKS	5.4	18.5
P1-5	IDEQTGLPIKS	25.5	37.6
P1-5ΔS	IDEQTGLPIK	1.4	0.2
P1-5ΔKS	IDEQTGLPI	1.1	0.4
Expt 2
BboP1-4	DEQTGLPIKS	10.3	34.8
BbgP1-4b	DEQTGLPVKN	0.8	15.0
P1-4Nc	DEQTGLPIKN	5.7	18.3
P1-4Vd	DEQTGLPVKS	0.8	41.2

^aThe minimal T-cell epitope that stimulated CD4⁺ T cell clones is underlined.

^bAmino acid sequence of B. bigemina Hsp20 corresponding to P1-4. Amino acid residues in bold type indicate differences between the B. bovis and B. bigemina Hsp20 epitopes.

^cReplacement of the serine residue with an asparagine residue (bold type).

^dReplacement of the isoleucine residue with a valine residue (bold type).

^eSI, stimulation index (mean counts per minute of cells stimulated with 1 μg of Hsp20 peptide per ml/mean counts per minute of control MSP2 peptide). SI values of >3.0 are considered positive and are shown in bold type.

^fHsp20-specific CD4⁺ T-cell clones described previously (13).