Reversal of human immunodeficiency virus type 1 IIIB to a neutralization-resistant phenotype in an accidentally infected laboratory worker with a progressive clinical course

Abstract

The role of humoral immunity in controlling human immunodeficiency virus type 1 (HIV-1) is still controversial. The resistance of primary HIV-1 variants to neutralization by antibodies, sera from HIV-1-infected patients, and soluble CD4 protein has been suggested to be a prerequisite for the virus to establish persistence in vivo. To further test this hypothesis, we studied the neutralization sensitivity of two IIIB/LAV variants that were isolated from a laboratory worker who accidentally was infected with the T-cell-line-adapted neutralization-sensitive IIIB isolate. Compared to the original virus in the inoculum, the reisolated viruses showed an increased resistance to neutralization over time. The ratio of nonsynonymous to synonymous nucleotide substitutions in the envelope gene pointed to strong positive selection. The emergence of neutralization-resistant HIV preceded disease development in this laboratory worker. Our results imply that the neutralization resistance of primary HIV may indeed be considered an escape mechanism from humoral immune control.

FIG. 1

Neutralization sensitivity of HIV-IIIB and LW-F isolates as determined on human PHA-stimulated PBMC. Of the tested viruses, HIV-IIIB (●), fe0233 (○), and FF3346(▾), 100 TCID₅₀/ml was incubated with increasing concentrations of recombinant sCD4 (a), polyclonal pooled serum of HIV-1-infected patients (HIVIg and Ams^hps) (b), anti-CD4 binding site-directed MAbs (IgG1b12, 902, gp13, gp68, and F105) (c), and anti-gp41 MAbs 2F5 and 1577 (d). In the neutralization assay, p24 was measured, and mean optical densities (OD) were calculated from quadruplicate cultures from at least duplicate experiments. The percent neutralization was calculated by determining the reduction in supernatant p24 production in the presence of the neutralizing agent relative to that for control cultures lacking these agents.

FIG. 2

Phylogenetic analysis of complete HIV envelope sequences of the HXB2D and LW-F isolates. Included are two other IIIB-related sequences, BH10 (M15654) and PV22 (K02083), respectively, and an LW-F clone named LW90-2 (U12053) from which the envelope sequence was determined previously (50). The phylogenetic tree was constructed with the neighbor-joining, Kimura two-parameter distance estimation method. The MN branch is truncated to facilitate presentation and was used as an outgroup.

FIG. 3

Sequence of the parental HXB2D and the two reisolated LW-F isolates. The predicted amino acid sequences of the envelope glycoproteins of the fe0233 and FF3346 viruses, based on the consensus sequence of the Env fragment amplified from infected human PBMC, are aligned with the HXB2D sequence. Differences in amino acid residues are indicated. The start sites of gp120 and gp41 are shown, as are the locations of the different gp120 regions.