HIV patients stable on ART retain evidence of a high CMV load but changes to Natural Killer cell phenotypes reflect both HIV and CMV

Which NK cell populations mark the high burden of CMV present in all HIV patients beginning ART in Indonesia?

Background

Cytomegalovirus (CMV) has been linked with cardiovascular disease (CVD) in populations where some individuals are seronegative. However, effects of CMV are unclear in HIV patients who all have high levels of CMV antibodies. Other metrics of their CMV burden are needed. Amongst transplant recipients, CMV drives the expansion of NK cell populations expressing NKG2C and/or LIR1 and lacking FcRγ.

Methods

Indonesian HIV patients (n = 40) were tested before ART and after 6 months, with healthy local controls (n = 20). All patients had high CMV antibody titres. 52% started therapy with CMV DNA detectable by qPCR, providing a crude measure of CMV burden. Proportions of CD56^Hi or CD56^Lo NK cells expressing FcRγ, NKG2C or LIR1 were determined flow cytometrically. CVD was predicted using carotid intimal media thickness (cIMT). Values were correlated with levels of CMV antibodies on ART.

Results

Patients had low proportions of CD56^Lo and more CD56^Hi NK cells. However proportions of FcRγ⁻ NK cells were lowest in patients with CMV DNA, and cIMT values related inversely with FcRγ⁻ NK cells in these patients. Percentages of NKG2C⁺CD56^Lo NK cells were similar in patients and controls, but rose in patients with CMV DNA. Proportions of NKG2C⁺ CD56^Hi NK cells correlated with levels of CMV antibodies in CMV DNA-negative patients.

Conclusions

We show that the very high burdens of CMV in this population confound systems developed to study effects of CMV in other populations. FcRγ⁻ NK cells may be depleted by very high CMV burdens, but NKG2C and antibody levels may be informative in patients on ART.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12981-022-00439-2.

The Role of Natural Killer Cells and Regulatory T Cells While Aging with Human Immunodeficiency Virus

Combined antiretroviral therapy (cART) has increased the quality of life of people living with HIV (PLHIV). Consequently, the number of PLHIV >50 years is increasing worldwide. Patients on cART are known to remain in a proinflammatory state. The latter is linked to the development of non-AIDS-related chronic conditions. Although the number of aging PLHIV is increasing, the effect of HIV infection on the process of aging is not fully understood. Understanding the complexity of aging with HIV by investigating the effect of the latter on different components of the innate and adaptive immune systems is important to reduce the impact of these comorbid conditions and improve the quality of life of PLHIV. The role of killer immunoglobulin receptors (KIRs), expressed on the surface of natural killer (NK) cells, and their human leukocyte antigen (HLA) ligands in the clearance, susceptibility to or disease progression following HIV infection is well established. However, data on the effect of KIR-HLA interaction in aging HIV-infected population and the development of non-AIDS-related comorbid conditions are lacking. Moreover, conflicting data exist on the role of regulatory T cells (Tregs) during HIV infection. The purpose of this review is to advance the current knowledge on the role of NK cells and Tregs while aging with HIV infection.

Characterization of Natural Killer Cells in HIV Patients Beginning Therapy with a High Burden of Cytomegalovirus

BACKGROUND

Active infections with cytomegalovirus (CMV) increase NK cell expression of the inhibitory receptor LIR-1 and the activating receptor NKG2C in transplant recipients. However, the effects of CMV on NK cells are different in HIV patients stable on antiretroviral therapy (ART) and have not been analyzed in young HIV patients beginning ART.

METHODOLOGY

We followed a cohort of 78 Indonesian HIV patients beginning ART. CMV antibodies were measured in plasma before ART (baseline), and after 1, 3, 6, and 12 months. CMV DNA was sought in blood granulocytes at baseline by quantitative PCR assay and a deletion in the NKG2C gene was identified by PCR. NK cell profiles were monitored by flow cytometry in 19 patients stratified by the presence of CMV DNA. Healthy controls (n = 17) were assessed once.

RESULTS

All 78 patients were CMV seropositive and 41 had detectable CMV DNA. CMV DNA+ patients had higher proportions of total NK cells and CD16⁺ NK cells at baseline, but similar expression of LIR-1 and NKp30 on NK cells on ART. However, levels of CMV antibody were inversely related to median LIR-1 expression on NK cells. A dramatic elevation in cells expressing NKG2C was restricted to CMV DNA+ patients heterozygous for the NKG2C deletion. Patients with High NKG2C expression had lower levels of CMV antibodies.

CONCLUSION

A subpopulation of NK cells expressing NKG2C was induced by CMV replication in HIV patients heterozygous for a deletion in this gene. Individuals with an abundant NKG2C⁺ and LIR-1⁺ NK cells displayed lower levels of CMV reactive antibody.

Persistence of Activated and Adaptive-Like NK Cells in HIV+ Individuals despite 2 Years of Suppressive Combination Antiretroviral Therapy

Innate immune dysfunction persists in HIV⁺ individuals despite effective combination antiretroviral therapy (cART). We recently demonstrated that an adaptive-like CD56^dim NK cell population lacking the signal transducing protein FcRγ is expanded in HIV⁺ individuals. Here, we analyzed a cohort of HIV⁺ men who have sex with men (MSM, n = 20) at baseline and following 6, 12, and 24 months of cART and compared them with uninfected MSM (n = 15) to investigate the impact of cART on NK cell dysfunction. Proportions of NK cells expressing markers of early (CD69⁺) and late (HLA-DR⁺/CD38⁺) activation were elevated in cART-naïve HIV⁺ MSM (p = 0.004 and 0.015, respectively), as were FcRγ⁻ NK cells (p = 0.003). Using latent growth curve modeling, we show that cART did not reduce levels of FcRγ⁻ NK cells (p = 0.115) or activated HLA-DR⁺/CD38⁺ NK cells (p = 0.129) but did reduce T cell and monocyte activation (p < 0.001 for all). Proportions of FcRγ⁻ NK cells were not associated with NK cell, T cell, or monocyte activation, suggesting different factors drive CD56^dim FcRγ⁻ NK cell expansion and immune activation in HIV⁺ individuals. While proportions of activated CD69⁺ NK cells declined significantly on cART (p = 0.003), the rate was significantly slower than the decline of T cell and monocyte activation, indicating a reduced potency of cART against NK cell activation. Our findings indicate that 2 years of suppressive cART have no impact on CD56^dim FcRγ⁻ NK cell expansion and that NK cell activation persists after normalization of other immune parameters. This may have implications for the development of malignancies and co-morbidities in HIV⁺ individuals on cART.