ABSTRACT
Natural killer (NK) cells play a critical role in virus control. However, it has remained largely unclear whether NK cell mobilization in SARS-CoV-2 infections is beneficial or pathologic. To address this deficit, we employed a validated experimental NK cell depletion non-human primate (NHP) model with SARS-CoV-2 Delta variant B.1.617.2 challenge. Viral loads (VL), NK cell numbers, activation, proliferation, and functional measures were evaluated in blood and tissues. In non-depleted (control) animals, infection rapidly induced NK cell expansion, activation, and increased tissue trafficking associated with VL. Strikingly, we report that experimental NK cell depletion leads to higher VL, longer duration of viremia, significantly increased levels of pro-inflammatory cytokines in the lungs, and overt lung damage. Overall, we find the first significant and conclusive evidence for NK cell-mediated control of SARS-CoV-2 virus replication and disease pathology. These data indicate that adjunct therapies for infection could largely benefit from NK cell-targeted approaches.
Subject(s)
Lung Diseases , Severe Acute Respiratory Syndrome , COVID-19 , ViremiaABSTRACT
Natural killer (NK) cells are innate lymphocytes with potent activity against a wide range of viruses. In SARS-CoV-2 infection, NK cell activity might be of particular importance within lung tissues. Here, we investigated whether NK cells with activity against Spike+ cells are induced during SARS-CoV-2 infection and have a role in modulating viral persistence beyond primary clearance from nasopharyngeal and tracheal tissues. We performed an integrated analysis of NK cells and macrophages in blood and bronchoalveolar lavage fluids (BALF) of COVID-19 convalescent non-human primates in comparison to uninfected control animals. SARS-CoV-2 protein expression was detected for at least 9–18 months post-infection in alveolar macrophages. Convalescent animals segregated into two groups based on cellular phenotypes and viral persistence profiles in BALF. The animals with lower persistent antigen displayed macrophages with a regulatory phenotype and enhanced MHC-E restricted NK cell activity toward cells presenting peptides derived from the SARS-CoV-2 Spike protein leader sequence, while NK cell activity from the other convalescent animals, control animals and healthy humans were strongly inhibited by these Spike peptides. The adaptive NK cell activity was not detected in blood but in tissue-resident NK cells, and cross-reacted against MERS-CoV and SARS-CoV Spike-derived peptides.
Subject(s)
COVID-19ABSTRACT
ABSTRACT COVID-19 has forced rapid clinical translation of novel vaccine technologies, principally mRNA vaccines, that have resulted in meaningful efficacy and adequate safety in response to the global pandemic. Notwithstanding this success, there remains an opportunity for innovation in vaccine technology to address current limitations and meet the challenges of inevitable future pandemics. We describe a universal vaccine cell (UVC) rationally designed to mimic the natural physiologic immunity induced post viral infection of host cells. Induced pluripotent stem cells were CRISPR engineered to delete MHC-I expression and simultaneously overexpress a NK Ligand adjuvant to increase rapid cellular apoptosis which was hypothesized to enhance viral antigen presentation in the resulting immune microenvironment leading to a protective immune response. Cells were further engineered to express the parental variant WA1/2020 SARS-CoV-2 spike protein as a representative viral antigen prior to irradiation and cryopreservation. The cellular vaccine was then used to immunize non-human primates in a standard 2-dose, IM injected prime + boost vaccination with 1e8 cells per 1 ml dose resulting in robust neutralizing antibody responses (1e3 nAb titers) with decreasing levels at 6 months duration. Similar titers generated in this established NHP model have translated into protective human neutralizing antibody levels in SARS-Cov-2 vaccinated individuals. Animals vaccinated with WA1/2020 spike antigens were subsequently challenged with 1.0 × 10 5 TCID 50 infectious Delta (B.1.617.2) SARS-CoV-2 in a heterologous challenge which resulted in an approximately 3-log order decrease in viral RNA load in the lungs. These heterologous viral challenge results reflect the ongoing real-world experience of original variant WA1/2020 spike antigen vaccinated populations exposed to rapidly emerging variants like Delta and now Omicron. This cellular vaccine is designed to be a rapidly scalable cell line with a modular poly-antigenic payload to allow for practical, large-scale clinical manufacturing and use in an evolving viral variant environment. Human clinical translation of the UVC is being actively explored for this and potential future pandemics.