Acute Respiratory Distress in Aged, SARS-CoV-2-Infected African Green Monkeys but Not Rhesus Macaques.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces a wide range of disease severity, ranging from asymptomatic infection to a life-threating illness, particularly in the elderly population and individuals with comorbid conditions. Among individuals with serious coronavirus 2019 (COVID-19) disease, acute respiratory distress syndrome (ARDS) is a common and often fatal presentation. Animal models of SARS-CoV-2 infection that manifest severe disease are needed to investigate the pathogenesis of COVID-19-induced ARDS and evaluate therapeutic strategies. We report two cases of ARDS in two aged African green monkeys (AGMs) infected with SARS-CoV-2 that had pathological lesions and disease similar to severe COVID-19 in humans. We also report a comparatively mild COVID-19 phenotype characterized by minor clinical, radiographic, and histopathologic changes in the two surviving, aged AGMs and four rhesus macaques (RMs) infected with SARS-CoV-2. Notable increases in circulating cytokines were observed in three of four infected, aged AGMs but not in infected RMs. All the AGMs had increased levels of plasma IL-6 compared with baseline, a predictive marker and presumptive therapeutic target in humans infected with SARS-CoV-2. Together, our results indicate that both RMs and AGMs are capable of modeling SARS-CoV-2 infection and suggest that aged AGMs may be useful for modeling severe disease manifestations, including ARDS.

Lung Expression of Human Angiotensin-Converting Enzyme 2 Sensitizes the Mouse to SARS-CoV-2 Infection.

Preclinical mouse models that recapitulate some characteristics of coronavirus disease (COVID-19) will facilitate focused study of pathogenesis and virus-host responses. Human agniotensin-converting enzyme 2 (hACE2) serves as an entry receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to infect people via binding to envelope spike proteins. Herein we report development and characterization of a rapidly deployable COVID-19 mouse model. C57BL/6J (B6) mice expressing hACE2 in the lung were transduced by oropharyngeal delivery of the recombinant human adenovirus type 5 that expresses hACE2 (Ad5-hACE2). Mice were infected with SARS-CoV-2 at Day 4 after transduction and developed interstitial pneumonia associated with perivascular inflammation, accompanied by significantly higher viral load in lungs at Days 3, 6, and 12 after infection compared with Ad5-empty control group. SARS-CoV-2 was detected in pneumocytes in alveolar septa. Transcriptomic analysis of lungs demonstrated that the infected Ad5-hACE mice had a significant increase in IFN-dependent chemokines Cxcl9 and Cxcl10, and genes associated with effector T-cell populations including Cd3 g, Cd8a, and Gzmb. Pathway analysis showed that several Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were enriched in the data set, including cytokine-cytokine receptor interaction, the chemokine signaling pathway, the NOD-like receptor signaling pathway, the measles pathway, and the IL-17 signaling pathway. This response is correlative to clinical response in lungs of patients with COVID-19. These results demonstrate that expression of hACE2 via adenovirus delivery system sensitized the mouse to SARS-CoV-2 infection and resulted in the development of a mild COVID-19 phenotype, highlighting the immune and inflammatory host responses to SARS-CoV-2 infection. This rapidly deployable COVID-19 mouse model is useful for preclinical and pathogenesis studies of COVID-19.

Role for cFMS in maintaining alternative macrophage polarization in SIV infection: implications for HIV neuropathogenesis.

BACKGROUND: Macrophage-colony stimulating factor (M-CSF) has been implicated in HIV neuropathogenesis through its ability to modulate activation of macrophages (MΦs) and microglia, as well as enhance the susceptibility of these cells to infection and promote virus production. We have recently reported that MΦs accumulating perivascularly and within nodular lesions in archival brain tissue of simian immunodeficiency virus (SIV)-infected rhesus macaques with encephalitis (SIVE) express M-CSF. In contrast, IL-34, which shares the same receptor, cFMS, was observed more often in parenchymal cells. METHODS: Frontal white and grey matter from non-infected and SIV-infected rhesus macaques with and without SIVE were examined by single- and double-label immunohistochemistry for M-CSF, IL-34, and CD163 expression. Primary rhesus macaque and human peripheral blood mononuclear cells were cultured with and without 2.5 ng/ml M-CSF or IL-34 alone and with 470 nM or 4.7 µM of GW2580, a receptor tyrosine kinase inhibitor with high specificity for cFMS. After 24 h, cells were analyzed by flow cytometry to examine the effect of these cytokines on promoting an M2 monocyte/MΦ phenotype. RESULTS: Here, we demonstrate that in SIVE brain, accumulating M-CSF(+) MΦs are also CD163(+), while IL-34 does not appear to co-localize significantly with CD163 in the parenchyma. We further demonstrate that M-CSF and IL-34 are expressed by neurons in normal brain but are altered in SIV and SIVE. Through in vitro studies, we show that M-CSF and IL-34 upregulate CD163, a marker for type 2 activation of MΦs (M2), by primary monocytes, which is attenuated by the addition of GW2580. CONCLUSIONS: Together, these data suggest that both cFMS ligands may promote and/or prolong M2 activation of MΦs and microglia in brains of SIV-infected animals with encephalitis. As such, cFMS signaling may be an attractive target for eliminating long-lived MΦ reservoirs of HIV infection in brain, as well as other tissues.

Safety, immunogenicity, and protection provided by unadjuvanted and adjuvanted formulations of a recombinant plant-derived virus-like particle vaccine candidate for COVID-19 in nonhuman primates.

Although antivirals are important tools to control severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, effective vaccines are essential to control the current coronavirus disease 2019 (COVID-19) pandemic. Plant-derived virus-like particle (VLP) vaccine candidates have previously demonstrated immunogenicity and efficacy against influenza. Here, we report the immunogenicity and protection induced in rhesus macaques by intramuscular injections of a VLP bearing a SARS-CoV-2 spike protein (CoVLP) vaccine candidate formulated with or without Adjuvant System 03 (AS03) or cytidine-phospho-guanosine (CpG) 1018. Although a single dose of the unadjuvanted CoVLP vaccine candidate stimulated humoral and cell-mediated immune responses, booster immunization (at 28 days after priming) and adjuvant administration significantly improved both responses, with higher immunogenicity and protection provided by the AS03-adjuvanted CoVLP. Fifteen micrograms of CoVLP adjuvanted with AS03 induced a polyfunctional interleukin-2 (IL-2)-driven response and IL-4 expression in CD4 T cells. Animals were challenged by multiple routes (i.e., intratracheal, intranasal, and ocular) with a total viral dose of 106 plaque-forming units of SARS-CoV-2. Lower viral replication in nasal swabs and bronchoalveolar lavage fluid (BALF) as well as fewer SARS-CoV-2-infected cells and immune cell infiltrates in the lungs concomitant with reduced levels of proinflammatory cytokines and chemotactic factors in the BALF were observed in animals immunized with the CoVLP adjuvanted with AS03. No clinical, pathologic, or virologic evidence of vaccine-associated enhanced disease was observed in vaccinated animals. The CoVLP adjuvanted with AS03 was therefore selected for vaccine development and clinical trials.

Neuropathology and virus in brain of SARS-CoV-2 infected non-human primates.

Neurological manifestations are a significant complication of coronavirus disease (COVID-19), but underlying mechanisms aren't well understood. The development of animal models that recapitulate the neuropathological findings of autopsied brain tissue from patients who died from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are critical for elucidating the neuropathogenesis of infection and disease. Here, we show neuroinflammation, microhemorrhages, brain hypoxia, and neuropathology that is consistent with hypoxic-ischemic injury in SARS-CoV-2 infected non-human primates (NHPs), including evidence of neuron degeneration and apoptosis. Importantly, this is seen among infected animals that do not develop severe respiratory disease, which may provide insight into neurological symptoms associated with "long COVID". Sparse virus is detected in brain endothelial cells but does not associate with the severity of central nervous system (CNS) injury. We anticipate our findings will advance our current understanding of the neuropathogenesis of SARS-CoV-2 infection and demonstrate SARS-CoV-2 infected NHPs are a highly relevant animal model for investigating COVID-19 neuropathogenesis among human subjects.

Elevated indoleamine-2,3-dioxygenase enzyme activity in a novel mouse model of HIV-associated atherosclerosis.

OBJECTIVE: HIV atherosclerosis and cardiovascular disease (CVD) represent a significant human health burden in the era of combination antiretroviral therapy (cART). The pathogenesis of HIV atherosclerosis is still poorly understood, due, in part, to the lack of a suitable small animal model. Indoleamine-2,3-dioxygenase (IDO) enzyme activity is the first and rate-limiting step in tryptophan catabolism and is measured by the kynurenine to tryptophan ratio (KTR). The serum KTR is a biomarker of inflammation and has recently been implicated as an important risk factor for CVD in patients living with HIV (PLWH) who are virologically suppressed under cART. However, IDO activity in HIV-associated CVD has not been studied in mouse model before. DESIGN: A novel mouse model of HIV atherosclerosis (Tg26/ApoE) was generated and examined for IDO activity and atherogenesis throughout 8 weeks on a high-fat diet. Tg26/ApoE mice were compared with Tg26 and ApoE single transgenic mice, before and during a high-fat diet. METHOD: Serum kynurenine, tryptophan and percentage of aortic plaque formation were measured. Additionally, levels of relevant cytokines were investigated in Tg26/ApoE and ApoE. RESULTS: Tg26/ApoE developed an accelerated atherosclerosis with increasing levels of KTR that were associated with plaque progression. This accelerated plaque was potentially driven by elevated levels of circulating IL-6. CONCLUSION: These results indicate that Tg26/ApoE serve as a new mouse model for HIV-induced atherogenesis, and aid in understanding the role of tryptophan catabolism in the pathogenesis of HIV atherosclerosis/CVD.

CSF-1R up-regulation is associated with response to pharmacotherapy targeting tyrosine kinase activity in AML cell lines.

BACKGROUND: The oncogenic potential of colony stimulating factor 1 receptor (CSF-1R) has been well described, while its relevance for human acute myelogenous leukemia (AML) is still undetermined. In a recent clinical trial for AML, sunitinib was found to hold potential therapeutic benefit, however, the mechanism for this remains unknown. MATERIALS AND METHODS: In this study, we treated three myeloid cell lines, Mono-Mac 1, THP-1, and U937, with sunitinib, and a small-molecule CSF-1R inhibitor (cFMS-I) to test the anticancer effect of such treatment. RESULTS: Mono-Mac 1 cells had inhibited proliferation and extracellular-signal regulated kinase activity as a result of CSF-1R inhibition and a dose-dependent increase in CSF-1R expression with both sunitinib and cFMS-I. CONCLUSION: Our results suggest potential for CSF-1R as an important target of sunitinib or other similar drugs. Future study of CSF-1R may produce more targeted therapeutic approaches and aid in the development of personalized medicine for AML.