HLA class I subtype-dependent expansion of KIR3DS1+ and KIR3DL1+ NK cells during acute human immunodeficiency virus type 1 infection

Abstract

NK cells are critical in the early containment of viral infections. Epidemiological and functional studies have shown an important role of NK cells expressing specific killer immunoglobulin-like receptors (KIRs) in the control of human immunodeficiency virus type 1 (HIV-1) infection, but little is known about the mechanisms that determine the expansion of these antiviral NK cell populations during acute HIV-1 infection. Here we demonstrate that NK cells expressing the activating receptor KIR3DS1(+) and, to a lesser extent, the inhibitory receptor KIR3DL1(+) specifically expand in acute HIV-1 infection in the presence of HLA-B Bw480I, the putative HLA class I ligand for KIR3DL1/3DS1. These data demonstrate for the first time the HLA class I subtype-dependent expansion of specific KIR(+) NK cells during an acute viral infection in humans.

FIG. 1.

Expansion of KIR⁺ NK cells in acute HIV-1 infection. (A) Primary flow panels demonstrate the increase of CD3⁻ CD56^dim KIR⁺ (CD158a, CD158b, CD158e, and NKB1⁺) NK cells in acute infection (left) compared to the level in a patient with chronic infection (middle) or an uninfected control (right). (B) The dot plot shows the overall increase of total KIR⁺ NK cells in patients with acute and chronic HIV-1 infection compared to uninfected controls (HIV neg).

FIG. 2.

Preferential increase in KIR3DS1 transcript levels in acute HIV-1 infection. We analyzed changes in KIR transcription in purified bulk CD3⁻ CD56^+/− CD16^+/− NK cells by quantitative SYBR green PCR. There was an overall increase in KIR transcripts in bulk NK cells in both chronic and acutely infected individuals compared to HIV-negative (HIV−) controls (A). This increase was associated with elevated inhibitory KIR mRNA levels in chronic HIV infection and activating KIR mRNA levels in acute infection (B). Elevated KIR3DS1 transcript levels dominated in primary HIV-1 infection (C). N, HIV negative; A, acute HIV infection; C, chronic HIV infection; *, P < 0.05.

FIG. 3.

Early and persistent elevation in KIR3DS1 and KIR3DL1 transcripts in the presence of HLA-B Bw480I. To determine whether the presence of the putative ligand HLA-B Bw480I had a role in modulating the expression of KIR3DS1 and KIR3DL1 transcripts, we compared transcript levels for these two receptors at the first visit during primary infection and after 1 year of untreated HIV-1 infection compared to those in HIV-negative individuals. All subjects were KIR3DS1/3DL1⁺ and expressed at least one copy of HLA-B Bw480I or two copies of HLA-B Bw6. The dot plots show that the mRNA levels of KIR3DS1 (left) and KIR3DL1 (right) transcripts were elevated in subjects coexpressing HLA-B Bw480I compared to those that only expressed HLA-B Bw6 during primary infection and that the transcript levels stayed elevated over the course of the first year of infection (A). The kinetics of KIR3DS1 (left) or KIR3DL1 (right) transcript decay are depicted on the line graph (B), demonstrating the rapid loss of both receptor transcripts in subjects that lack the coexpression of HLA-B Bw480I.

FIG. 4.

Early and persistent expansion of KIR3DS1⁺ and KIR3DL1⁺ NK cells in the presence of HLA-B Bw480I. To confirm that the changes observed on the transcriptional level correlated with differences on the protein level, we compared the proportions of KIR3DS1⁺ and KIR3DL1⁺ NK cells by flow cytometry in the same subjects described above, at the first visit during primary infection and after 1 year of untreated infection, compared to the level in HIV-uninfected controls. The flow plot depicts the gating strategy utilized to quantify the proportion of KIR3DS1⁺ (z27⁺ DX9⁻) and KIR3DL1⁺ (z27⁺ DX9⁺) NK cells (A). There was a clear elevation in KIR3DS1⁺ and KIR3DL1⁺ NK cells in uninfected controls in HLA-B Bw480I⁺ subjects, but not Bw6⁺ subjects (B), and this difference was amplified during primary infection and remained elevated over the levels during the first year of infection (B and C).