TABLE 2.

Affinity-purified human anti-gM/gN antibodies neutralize unrelated HCMV strains

Virusa	Antibody	% Reduction in input infectivity at the following dilutionb:
		With complement		Without complement
Expt 1		1:20	1:40	1:20	1:40
AD169	Anti-gM/gN	59	68	73	70
Toledo	Anti-gM/gN	NT	50	NT	50
AD169	Anti-gM/gN MAbc	NT	96	NT	NT
Toledo	Anti-gM/gN MAb	NT	96	NT	NT
Expt 2		1:18	1:54	1:18	1:54
TR	Anti-gM/gNad	46	29	NT	NT
	Anti-gM/gNb	45	50	NT	NT
	Anti-gM/gNc	64	64	NT	NT
	Human IgG	98	84	NT	NT
	Anti-gN MAb (14-16a)	77	69	NT	NT

^aStrains of HCMV used in this assay included AD169 (gN genotype 1), Toledo (gN genotype 4a), and TR (gN genotype 3a) (27).

^bVirus neutralization expressed as percent reduction in input infectivity as quantified in a microneutralization assay (1). Dilutions of antibodies are indicated, and neutralizing activity was determined in the presence of 5% guinea pig serum as the source of complement or in the absence of complement. NT, not tested.

^cThe neutralizing activity of monoclonal antibody 14-16 (anti-gN) was carried out in the presence of complement.

^dThree different preparations of affinity-purified anti-gM/gN antibodies (indicated by subscript letters a, b, and c) were tested in experiment 2, and each differed from the preparation tested in experiment 1. Each preparation was characterized for specificity by immunofluorescence assays using cells expressing gB, pp150, and gM/gN. The concentration of IgG in these preparations was not determined. Note that in each experiment, antibodies were prepared from the same starting pool of human antibodies using the protocol described in Materials and Methods. The human anti-CMV immune IgG (human IgG) is the starting material used for preparation of affinity-purified antibodies, and MAb 14-16a is a murine MAb reactive with gN (5). Both were used as positive controls in these assays.