Low-replicating viruses and strong anti-viral immune response associated with prolonged disease control in a superinfected HIV-1 LTNP elite controller

Abstract

Objective: To study the causes for the lack of clinical progression in a superinfected HIV-1 LTNP elite controller patient.

Methodology and principal findings: We studied host genetic, virological and immunological factors associated with viral control in a SI long term non progressor elite controller (LTNP-EC). The individual contained both viruses and maintained undetectable viral loads for >20 years and he did not express any of the described host genetic polymorphisms associated with viral control. None of four full-length gp160 recombinants derived from the LTNP-EC replicated in heterologous peripheral blood mononuclear cells. CTL responses after SI were maintained in two samples separated by 9 years and they were higher in breadth and magnitude than responses seen in most of 250 treatment naïve patients and also 25 controller subjects. The LTNP-EC showed a neutralization response, against 4 of the 6 viruses analyzed, superior to other ECs.

Conclusions: The study demonstrated that a strong and sustained cellular and humoral immune response and low replicating viruses are associated with viral control in the superinfected LTNP-EC.

Figure 1. Clinical characteristics of the patient.

CD4⁺ T cell counts and viral load are represented in the Y axis against time in the X axis. The first sample was taken 78 months after the first documented HIV-1 positive test diagnosis. Blue arrow shows the first sample available, close to the estimated moment of SI (1995). In yellow are represented samples taken to perform quasispecies analysis and gp160 amplification. Serum samples used for neutralization analysis (○) and PBMC samples used for CTL response (□) are indicated.

Figure 2. Maximum likelihood tree derived from the C2-V5 env sequences obtained during the patient follow-up.

Maximum Likelihood tree was performed with the help of the MEGA program. Symbols represent sequences taken in different year: 1995 □, 1996 ▾, 1998 ◊, 2001♦, ○ 2005, •2006 and 2007▿. Virus “a” corresponds to the primoinfecting virus and the encircled groups identify the different a1, a2, and a3 variants. Virus “b” corresponds to the superinfecting virus. Samples chosen for molecular cloning are marked with arrows a1, a2 and a3 from virus “a” and b1 from virus “b”. Nucleotide sequences from control Spanish isolates are denoted by standard typeface and sequences from subtype B reference viruses from the Los Alamos HIV Data Base are shown in italic. The scale bar on the bottom of the figure represents 5% of genetic distance.

Figure 3. Replicative capacity of the recombinant viruses.

Viral replication was measured by the p24 production, showed in logarithmic scale in the Y axis, in U87.CD4.CCR5 in panel A) and PBMC cells in panel B). In X axis are represented days of culture.

Figure 4. Gp160 amino-acid sequences of LTNP-EC viruses.

Amino acid sequences of viruses a1, a2, a3 and b1 are shown. Underlined residues marked the N-glycosylation sites. Empty vertical arrows signal CD4⁺ binding residues. Cysteines in the variable loops in gp120 are marked with asterisks. Shaded areas correspond to the signal peptide, variable regions in gp120, fusion peptide, homology regions and lentivirus lytic peptide (LLP1-2) region in gp41. In green are shown the two positions in common for a2 and b1 viruses and that are different from the non-replicating viruses.

Figure 5. IFN-γ ELISPOT analysis of the HIV-1 specific CD8⁺ T cell response in the LTNP-EC.

The analysis was performed in the first sample available after SI (▪) and on a second one taken 8.8 years later (▪). The results are expressed as spot-forming cells (SFC) per million inputs PBMC in Y axis. The X axis shows the overlapping peptides in viral proteins along the genome eliciting a positive response.