Functional Perturbation of Mucosal Group 3 Innate Lymphoid and Natural Killer Cells in Simian-Human Immunodeficiency Virus/Simian Immunodeficiency Virus-Infected Infant Rhesus Macaques

Abstract

Mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1) via breastfeeding is responsible for nearly half of new infections of children with HIV. Although innate lymphoid cells (ILC) and natural killer (NK) cells are found throughout the oral mucosae, the effects of HIV/simian-human immunodeficiency virus (SHIV) in these tissues are largely unknown. To better understand the mechanics of postnatal transmission, we performed a comprehensive study of simian immunodeficiency virus (SIV)/SHIV-infected infant rhesus macaques (RM) and tracked changes in frequency, trafficking, and function of group 3 ILC (ILC3) and NK cells using polychromatic flow cytometry and cell stimulation assays in colon, tonsil, and oral lymph node samples. Infection led to a 3-fold depletion of ILC3 in the colon and an increase in the levels of NK cells in tonsils and oral lymph nodes. ILC3 and NK cells exhibited alterations in their trafficking repertoires as a result of infection, with increased expression of CD103 in colon NK cells and curtailment of CXCR3, and a significant decrease in α4β7 expression in colon ILC3. SPICE analyses revealed that ILC3 and NK cells displayed distinct functional profiles by tissue in naive samples. Infection perturbed these profiles, with a nearly total loss of interleukin-22 (IL-22) production in the tonsil and colon; an increase in the levels of CD107a, gamma interferon (IFN-γ), and tumor necrosis factor alpha (TNF-α) from ILC3; and an increase in the levels of CD107a, macrophage inflammatory protein 1 beta (MIP-1β), and TNF-α from NK cells. Collectively, these data reveal that lentivirus infection alters the frequencies, receptor repertoires, and functions of innate cells in the oral and gut mucosa of infants. Further study will be required to delineate the full extent of the effect that these changes have on oral and gut homeostasis, SHIV/SIV pathogenesis, and oral opportunistic disease. IMPORTANCE Vertical transmission of HIV from mother to child accounts for many of the new cases seen worldwide. There is currently no vaccine to mitigate this transmission, and there has been limited research on the effects that lentiviral infection has on the innate immune system in oral tissues of infected children. To fill this knowledge gap, our laboratory studied infant rhesus macaques to evaluate how acute SIV/SHIV infections impacted ILC3 and NK cells, which are immune cells critical for mucosal homeostasis and antimicrobial defense. Our data revealed that SIV/SHIV infection led to a depletion of ILC3 and an increase of NK cells and to a functional shift from a homeostatic to a multifunctional proinflammatory state. Taking the results together, we describe how lentiviral infection perturbs the oral and gastrointestinal mucosae of infant macaques through alterations of resident innate immune cells giving rise to chronic inflammation and potentially exacerbating morbidity and mortality in children living with HIV.

Type 3 Innate Lymphoid Cells as Regulators of the Host-Pathogen Interaction

“…The infection altered the trafficking and chemokine receptors in ILC3s, reducing the expression of a4b7 integrin in colonic ILC3s and consequently minimizing IL-22 secretion in colon and oral mucosa. The aforementioned study corroborated the premise that the lentivirus infection could have significant effects on the frequency, phenotype, and function of innate cells in the oral and gut mucosa such as the reduction of ILC3 IL-22 + which might be particularly relevant in infants infected through breastfeeding, because their immune system is not fully functional (62). Importantly, it has recently been demonstrated that NKp44 + ILCs play a protective role in the progression of the disease, as their higher frequency in the mucosa was associated with delayed SIV acquisition and decreased viremia in vaccinated macaques (63), thus confirming previous published data (64).…”

Evolution and Diversity of Immune Responses during Acute HIV Infection

“…Although not yet measured in humans, SIV studies have shown depletion of ILC3s in the infant NHP gut (Hueber et al, 2020), as well as depletion and phenotypic skewing of NKp44 + ILCs during acute infection in adult gut (Li et al, 2014), and suggested protective qualities of ILC3s in adenovirus-SIV vaccination and With the advent of next-generation sequencing and steady improvements in low-input and single-cell profiling technologies, highcontent measurements of gene expression, protein expression, open chromatin, and other cellular features are becoming increasingly accessible and affordable substantial insights into disease biology in heterogeneous tissue environments (Hartmann and Bendall, 2020;Shema et al, 2019;Stubbington et al, 2017). Critically, many of these assays can be used to study rare cell types from low-input samples like tissue biopsies, fine-needle aspirates, and small amounts of blood.…”

“…OPEN ACCESS mother-to-child transmission (Hueber et al, 2020;Rahman et al, 2019). Groups 1 and 3 ILCs present in the GI tract during SIV infection potentially contribute to pro-inflammatory responses by producing higher levels of IFN-g, tumor necrosis factor (TNF)-a, and IL-22 during the breakdown of the epithelium (Cogswell et al, 2020); however, when these pro-inflammatory ILCs arise is unknown.…”

Tissue-Dependent Adaptations and Functions of Innate Lymphoid Cells

“…In response to mouse enteric rotavirus infections, epithelial IL-1a induced ILC3-derived IL-22 which synergized with epithelial IFN-l, promoting the induction of antiviral gene expression in intestinal epithelial cells, limiting viral replication and tissue damage (Figure 6C) (220). While ILC3s can promote antiviral immunity, they experience cytokine-dependent depletion in the intestinal tract of HIV + human and SIV + non-human primates, altering epithelial permeability and homeostasis (221)(222)(223). Collectively, ILCs promote intestinal barrier defense against enteric bacterial, fungal, and viral infections by exerting cytokine or cell contactdependent effects on intestinal epithelial cells.…”