Prolonged control of replication-competent dual- tropic human immunodeficiency virus-1 following cessation of highly active antiretroviral therapy

Abstract

Background: While initiation of highly active antiretroviral therapy (HAART) during primary HIV-1 infection occasionally results in transient control of viral replication after treatment interruption, the vast majority of patients eventually experience a rebound in plasma viremia.

Results: Here we report a case of a patient who was started on HAART during symptomatic primary infection and who has subsequently maintained viral loads of < 50 copies/mL for more than nine years after the cessation of treatment. This patient had a high baseline viral load and has maintained a relatively high frequency of latently infected CD4(+) T cells. In addition, he does not have any known protective HLA alleles. Thus it is unlikely that he was destined to become a natural elite controller or suppressor. The mechanism of control of viral replication is unclear; he is infected with a CCR5/CXCR4 dual-tropic virus that is fully replication-competent in vitro. In addition, his spouse, who transmitted the virus to him, developed AIDS. The patient's CD4(+) T cells are fully susceptible to HIV-1 infection, and he has low titers of neutralizing antibodies to heterologous and autologous HIV-1 isolates. Furthermore, his CD8(+) T cells do not have potent HIV suppressive activity.

Conclusion: This report suggests that some patients may be capable of controlling pathogenic HIV-1 isolates for extended periods of time after the cessation of HAART through a mechanism that is distinct from the potent cytotoxic T lymphocyte (CTL) mediated suppression that has been reported in many elite suppressors.

Figure 1

Clinical characteristics of Patient 169. The patient's CD4 counts and viral load are shown. Viral load measurements below the limit of detection are denoted by open symbols. The time on HAART is denoted by the shaded region.

Figure 2

Phylogenetic Analysis: An alignment of the variable regions of env is shown for replication-competent isolates obtained from Patient 169 and his spouse. Numbering is from the first amino acid in gp120. (A). The sequences are also compared to other Clade B sequences(B). Phylogenies were estimated by using a classical approach, functioning under a maximum-likelihood (ML) optimality criterion.

Figure 3

Phenotypic analyses of viral isolates from Patient 169. (A) Viral tropism was determined using GHOST cells expressing CCR5 and/or CXCR4. Open bars were below the limit of the detection (B) Replication kinetics was determined in primary CD4+ T cells (left) and the MT-2 cell line (right).

Figure 4

CD4+ T cell susceptibility assay. CD4+ T cells from five healthy donors (grey columns) and Patient 169 (shaded column) were infected with CCR5 tropic (Bal) and CXCR4 tropic (NL43) pseudotypevirus by spinoculation (A) or with NL43pseudotype virus without spinoculation (B). Infection with serial dilutions of CXCR4-tropic (C), CCR5-tropic (D) and dual-tropic virus (E) was also performed by spinoculation. The percent of infected cells (GFP positive) are shown.

Figure 5

Titers of HIV-specific neutralizing antibodies. (A) Neutralizing activity of plasma from viremic patients, ES, and patient 169 against recombinant virus with Env from the laboratory strain SF162. The open symbols denote titers that were greater than 1:4. (B) Neutralizing activity of plasma from Patient 169 against recombinant virus with Env from 1999 and 2010-1A isolates. Relative infection of TZMb1 cells by the recombinant isolates is shown in the presence of four fold dilutions of plasma.

Figure 6

CD8+ T cell epitope analysis. Epitopes in Nef (A) and Gag (B) targeted by CD8+ T cells as determined by an IFN-g ELISPOT assay using overlapping 15 mers. Open boxes represent actual peptides targeted in the assay whereas the shaded boxes represent predicted optimal HLA-B*42 restricted epiotpes which were not targeted.

Figure 7

CD8+ T cell functional analysis. The effect of CD8+ T cell depletion on autologous virus outgrowth is shown by a comparison of virus replication in activated unfractionated PBMC or activated PBMC from which CD8+ T cells were depleted (A). The ability of CD8+ T cells to inhibit replication of GFP expression virus in activated autologous CD4+ T cells is shown. Open bars were below the limit of the detection. (B) by comparing the percentage of infected CD4+ T cells (GFP positive) in the absence and presence of CD8+ T cells.