Intersubtype human immunodeficiency virus type 1 superinfection following seroconversion to primary infection in two injection drug users

Abstract

In this study, we describe two cases of human immunodeficiency virus type 1 (HIV-1) intersubtype superinfection with CRF01_AE and subtype B strains, which occurred in two injection drug users participating in a prospective cohort study in Bangkok, Thailand. In both cases, the superinfecting strain was detected by molecular and serologic analyses several weeks after complete seroconversion to the primary infection with a strain belonging to a different subtype. Superinfection occurred despite specific T-cell and humoral antibody responses to the primary virus. In both cases, cross-subtype immune responses were limited or absent prior to the second infection. These data show that, in some individuals, the quality and quantity of the immune response elicited by primary HIV-1 infection may not protect against superinfection. This finding has important implications for vaccine design. HIV-1 vaccines, at a minimum, will need to include potent, broadly protective, conserved immunogens derived from several group M subtypes.

FIG. 1.

Phylogenetic analysis of HIV-1 sequences from case 1 (bold). (a) Representative sequences from pro subclones (297 bp) from FP, T0, T1, and T12 collection time points. (b) gp120 (env) population sequences (618 bp) obtained from PCR products generated by subtype-specific primers. Sequences generated during this study were obtained from the FP, T0, T1, and T12 collection time points. The source of the sequence (PBMC-DNA lysate or cell-free RNA) is indicated after each collection time when appropriate. Subclones are indicated by an underscore. Standard sequences representing HIV-1 subtypes were obtained from the HIV database at http://www.hiv-web.lanl.gov. HIV-1 subtypes are indicated to the right of the trees, and bootstrap values are indicated to the left of the branch nodes. The trees are unrooted, and branch lengths are proportional to the numbers of molecular changes between individual operational taxonomic units.

FIG. 2.

Phylogenetic analysis of HIV-1 C2-V3 (283-bp) sequences from case 2 (bold) from T4, T8, T20, and T32 collection time points. Population sequences were obtained from the T4, T8, and T20 collection time points; subclone sequences were obtained from the T32 collection time point. The source of the sequence (PBMC-DNA lysate or cell-free RNA) is indicated after each collection time point where appropriate. Standard sequences representing HIV-1 subtypes were obtained from the HIV database at http://www.hiv-web.lanl.gov. THSC09 and THSC12 are representative subtype B sequences from the IDU cohort (35). THSC81 and THSC88 are representative CRF01_AE sequences from the IDU cohort (35). HIV-1 subtypes are indicated to the right of the trees, and bootstrap values are indicated to the left of the branch nodes. The trees are unrooted, and the branch lengths are proportional to the number of molecular changes between operational taxonomic units.

FIG. 3.

Clinical parameters for disease progression for T0 through T32 for case 1 and case 2. Viral load is indicated on a log scale. For case 1, viral load was obtained for the FP time point also. For case 2, there was no detectable virus at FP. Viral load values are copies/milliliter; values for CD4⁺ and CD8⁺ T cells are per cubic millimeter.

FIG. 4.

EIA and PCR amplification for cases 1 and 2. (a) Absorbance was measured at 450 nm; a cutoff value of 0.3 (indicated by a dashed line) was used. (b) Subtype-specific amplification using CRF01_AE and subtype B-specific primers for case 1 (time points FP through T12) and for case 2 (time points FP through T32), respectively. +, positive amplification from both RNA and DNA; ±, positive amplification from RNA and negative amplification for DNA; −, negative amplification from both RNA and DNA; N/A, sample not available.

FIG. 5.

T-cell responses to recombinant vaccinia virus constructs expressing HIV-1 CRF01_AE and subtype B proteins. Counts of IFN-γ-producing T cells expressed as SFU/10⁶ cells are indicated on top of each bar and on the vertical axis. Collection time points sampled are indicated on the horizontal axis. The tables below each bar graph show the CRF01_AE and subtype B T-cell responses for individual gene regions.