TABLE 3.

Reciprocal titers of neutralizing antibodies in chronic-phase patient sera against recombinant viruses with genotype-specific Core-NS2 of genotypes 1a, 2a, 3a, 5a, and 6a with and without HVR1^a

Virus genotype (Core-NS2)	Reciprocal serum neutralization titerb
	90%			50%
	H06 (1a)	AA (4a)	SA3 (5a)	H06 (1a)	AA (4a)	SA3 (5a)
Original virus
1a	<50	•	•	800	•	•
2a	<50	<50	<50	50-51,200c	<50	<50
3a	<50	•	•	50-51,200c	•	•
5a	50	<50	<50	3,200	200	100
6a	6,400	•	•	51,200	•	•
Virus lacking HVR1
1aΔHVR1,H261R,Q444R	6,400	•	•	51,200	•	•
1aΔHVR1,N476D,S733F	6,400	•	•	25,600	•	•
2aΔHVR1	12,800	6,400	1,600	51,200	51,200	12,800
3aΔHVR1,A369V	6,400	•	•	51,200	•	•
5aΔHVR1	6,400	3,200	1,600	25,600	25,600	12,800
6aΔHVR1	51,200	•	•	204,800	•	•

^aFifty to 400 TCID₅₀s of virus stocks with genotype-specific Core-NS2 were incubated in 3 replicates with H06, AA, or SA3 sera in 2-fold dilution series and tested in Huh7.5 cell infections as described in Materials and Methods.

^bReciprocal neutralization titers are indicated as the highest dilution of H06 (genotype 1a), AA (genotype 4a), or SA3 (genotype 5a) sera leading to a reduction of FFU counts of at least 90% or 50% compared to the mean of 6 replicates of virus only. The small solid black circles indicate that no data was obtained for that virus. Mutations are annotated based on the H77 reference sequence (GenBank accession no. AF009606).

^cFor original viruses 2a and 3a, around half the virus population was neutralized at H06 serum dilutions 50 to 51,200 (Fig. 4B).