TABLE 2.

Neutralizing antibody titers of human serum samples against DENV-1 as determined using BHK, BHK-FcγRIIA/2, and BHK-FcγRIIA/4 cells

Sample source	Disease phase	Serum ID no.	DENV typea	Neutralizing titer (PRNT50) to DENV-1 in:
				BHK-21	BHK- FcγRIIA/2b	BHK- FcγRIIA/4c
Primary DENV infection	Earlyd	1f	1	<5	<5	<5
		2g	2	<5	<5	<5
	Latee	3f	1	160	160	160
		4g	2	<20j	<20j	<20j
		5h	3	10	<5	<5
		6h	4	320	10	10
Secondary DENV infection	Earlyd	7h	1i	10	<5	<5
		8h	1i	<5	<5	<5
		9h	2i	10	<5	<5
		10h	3i	320	160	160
	Latee	11h	1i	320	40	40
		12h	2i	320	40	40
		13h	3i	160	<5	<5
		14h	4i	640	10	10
Non-DENV patient	DENV IgG negative	15		<5	<5	<5
		16		<5	<5	<5
		17		<5	<5	<5
		18		<5	<5	<5

^aDENV types that infected the patients. The types of dengue virus were determined by type-specific real-time RT-PCR.

^bFcγRIIA-expressing BHK cell line 2.

^cFcγRIIA-expressing BHK cell line 4.

^dDays 1 to 3 after onset of the disease.

^eDays 6 to 14 after onset of the disease.

^fSamples 1 and 3 were obtained from the same patient, infected with DENV-1.

^gSamples 2 and 4 were obtained from the same patient, infected with DENV-2.

^hSerum samples 5 to 14 were obtained from patients 5 to 14, respectively.

ⁱDengue virus types of primary infection of patient numbers 7 to 14 were not determined. Dengue virus types in secondary infections are included in the table.

^jSerum was serially diluted 2-fold, starting from 1:20.