Vγ9Vδ2 T-cells Are Potent Inhibitors of SARS-CoV-2 Replication and Represent Effector Phenotypes in Patients With COVID-19.

Vγ9Vδ2 T cells play a key role in the innate immune response to viral infections through butyrophilin 3A (BTN3A). Here, we report blood Vγ9Vδ2 T cells decreased in clinically mild COVID-19 compared to healthy volunteers, and this was maintained up to 28 days and in the recovery period. Terminally differentiated Vγ9Vδ2 T cells tended to be enriched on the day of diagnosis, 28 days after, and during the recovery period. These cells showed cytotoxic and inflammatory activities following anti-BTN3A activation. BTN3A upregulation and Vγ9Vδ2 T-cell infiltration were observed in a lung biopsy from a fatal SARS-CoV-2 infection. In vitro, SARS-CoV-2 infection increased BTN3A expression in macrophages and lung cells that enhanced the anti-SARS-CoV-2 Vγ9Vδ2 T-cell cytotoxicity and interferon-γ and tumor necrosis factor-α. Increasing concentrations of anti-BTN3A lead to viral replication inhibition. Altogether, we report Vγ9Vδ2 T cells are important in the immune response against SARS-CoV-2 infection and activation by anti-BTN3A antibody may enhance their response. Clinical Trials Registration. NCT04816760.

Infection and Persistence of Coxiella burnetii Clinical Isolate in the Placental Environment.

Infection by Coxiella burnetii, the etiological agent of Q fever, poses the risk of causing severe obstetrical complications in pregnant women. C. burnetii is known for its placental tropism based on animal models of infection. The Nine Mile strain has been mostly used to study C. burnetii pathogenicity but the contribution of human isolates to C. burnetii pathogenicity is poorly understood. In this study, we compared five C. burnetii isolates from human placentas with C. burnetii strains including Nine Mile (NM) as reference. Comparative genomic analysis revealed that the Cb122 isolate was distinct from other placental isolates and the C. burnetii NM strain with a set of unique genes involved in energy generation and a type 1 secretion system. The infection of Balb/C mice with the Cb122 isolate showed higher virulence than that of NM or other placental isolates. We evaluated the pathogenicity of the Cb122 isolate by in vitro and ex vivo experiments. As C. burnetii is known to infect and survive within macrophages, we isolated monocytes and placental macrophages from healthy donors and infected them with the Cb122 isolate and the reference strain. We showed that bacteria from the Cb122 isolate were less internalized by monocyte-derived macrophages (MDM) than NM bacteria but the reference strain and the Cb122 isolate were similarly internalized by placental macrophages. The Cb122 isolate and the reference strain survived similarly in the two macrophage types. While the Cb122 isolate and the NM strain stimulated a poorly inflammatory program in MDM, they elicited an inflammatory program in placenta macrophages. We also reported that the Cb122 isolate and NM strain were internalized by trophoblastic cell lines and primary trophoblasts without specific replicative profiles. Placental explants were then infected with the Cb122 isolate and the NM strain. The bacteria from the Cb122 isolate were enriched in the chorionic villous foetal side. It is likely that the Cb122 isolate exhibited increased virulence in the multicellular environment provided by explants. Taken together, these results showed that the placental isolate of C. burnetii exhibits a specific infectious profile but its pathogenic role is not as high as the host immune response in pregnant women.

Monocytes and Macrophages, Targets of Severe Acute Respiratory Syndrome Coronavirus 2: The Clue for Coronavirus Disease 2019 Immunoparalysis.

BACKGROUND: Coronavirus disease 2019 (COVID-19) clinical expression is pleiomorphic, severity is related to age and comorbidities such as diabetes and hypertension, and pathophysiology involves aberrant immune activation and lymphopenia. We wondered if the myeloid compartment was affected during COVID-19 and if monocytes and macrophages could be infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). METHODS: Monocytes and monocyte-derived macrophages (MDMs) from COVID-19 patients and controls were infected with SARS-CoV-2 and extensively investigated with immunofluorescence, viral RNA extraction and quantification, and total RNA extraction followed by reverse-transcription quantitative polymerase chain reaction using specific primers, supernatant cytokines (interleukins 6, 10, and 1ß; interferon-ß; transforming growth factor-ß1, and tumor necrosis factor-α), and flow cytometry. The effect of M1- vs M2-type or no polarization prior to infection was assessed. RESULTS: SARS-CoV-2 efficiently infected monocytes and MDMs, but their infection is abortive. Infection was associated with immunoregulatory cytokines secretion and the induction of a macrophagic specific transcriptional program characterized by the upregulation of M2-type molecules. In vitro polarization did not account for permissivity to SARS-CoV-2, since M1- and M2-type MDMs were similarly infected. In COVID-19 patients, monocytes exhibited lower counts affecting all subsets, decreased expression of HLA-DR, and increased expression of CD163, irrespective of severity. CONCLUSIONS: SARS-CoV-2 drives monocytes and macrophages to induce host immunoparalysis for the benefit of COVID-19 progression.SARS-CoV-2 infection of macrophages induces a specific M2 transcriptional program. In Covid-19 patients, monocyte subsets were decreased associated with up-expression of the immunoregulatory molecule CD163 suggesting that SARS-CoV-2 drives immune system for the benefit of Covid-19 disease progression.

Daytime variation in SARS-CoV-2 infection and cytokine production.

S. Ray and A. Reddy recently anticipated the implication of circadian rhythm in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is the causative agent of the coronavirus disease (Covid-19). In addition to its key role in the regulation of biological functions, the circadian rhythm has been suggested as a regulator of viral infections. Specifically, the time of day of infection was found critical for illness progression, as has been reported for influenza, respiratory syncytial and parainfluenza type 3 viruses. We analyzed circadian rhythm implication in SARS-CoV-2 virus infection of isolated human monocytes, key actor cells in Covid-19 disease, from healthy subjects. The circadian gene expression of BMAL1 and CLOCK genes was investigated with q-RTPCR. Monocytes were infected with SARS-CoV-2 virus strain and viral infection was investigated by One-Step qRT-PCR and immunofluorescence. Interleukin (IL)-6, IL-1ß and IL-10 levels were also measured in supernatants of infected monocytes. Using Cosinor analysis, we showed that BMAL1 and CLOCK transcripts exhibited circadian rhythm in monocytes with an acrophase and a bathyphase at Circadian Time (CT)6 and CT17. After 48 h, the amount of SARS-CoV-2 virus increased in the monocyte infected at CT6 compared to CT17. The high virus amount at CT6 was associated with significant increased release in IL-6, IL-1ß and IL-10 compared to CT17. Our results suggest that time day of SARS-CoV-2 infection affects viral infection and host immune response. They support consideration of circadian rhythm in SARS-CoV-2 disease progression and we propose circadian rhythm as a novel target for managing viral progression.

Role of Vγ9vδ2 T lymphocytes in infectious diseases.

The T cell receptor Vγ9Vδ2 T cells bridge innate and adaptive antimicrobial immunity in primates. These Vγ9Vδ2 T cells respond to phosphoantigens (pAgs) present in microbial or eukaryotic cells in a butyrophilin 3A1 (BTN3) and butyrophilin 2A1 (BTN2A1) dependent manner. In humans, the rapid expansion of circulating Vγ9Vδ2 T lymphocytes during several infections as well as their localization at the site of active disease demonstrates their important role in the immune response to infection. However, Vγ9Vδ2 T cell deficiencies have been observed in some infectious diseases such as active tuberculosis and chronic viral infections. In this review, we are providing an overview of the mechanisms of Vγ9Vδ2 T cell-mediated antimicrobial immunity. These cells kill infected cells mainly by releasing lytic mediators and pro-inflammatory cytokines and inducing target cell apoptosis. In addition, the release of chemokines and cytokines allows the recruitment and activation of immune cells, promoting the initiation of the adaptive immune response. Finaly, we also describe potential new therapeutic tools of Vγ9Vδ2 T cell-based immunotherapy that could be applied to emerging infections.

BTN3A Targeting Vγ9Vδ2 T Cells Antimicrobial Activity Against Coxiella burnetii-Infected Cells.

Vγ9Vδ2 T cells have been reported to participate to the immune response against infectious diseases such as the Q fever caused by Coxiella burnetii infection. Indeed, the number and proportion of Vγ9Vδ2 T cells are increased during the acute phase of Q fever. Human Vγ9Vδ2 T cell responses are triggered by phosphoantigens (pAgs) produced by pathogens and malignant cells, that are sensed via the membrane receptors butyrophilin-3A1 (BTN3A1) and -2A1 (BTN2A1). Here, by using CRISPR-Cas9 inactivation in THP-1 cells, we show that BTN3A and BTN2A are required to Vγ9Vδ2 T cell response to C. burnetii infection, though not directly involved in the infection process. Furthermore, C. burnetii-infected monocytes display increased BTN3A and BTN2A expression and induce Vγ9Vδ2 T cell activation that can be inhibited by specific antagonist mAb. More importantly, we show that the antimicrobial functions of Vγ9Vδ2 T cells towards C. burnetii are enhanced in the presence of an BTN3A activating antibody. This supports the role of Vγ9Vδ2 T cells in the control of C. burnetii infection and argues in favor of targeting these cells as an alternative treatment strategy for infectious diseases caused by intracellular bacteria.

Macrophages and γδ T cells interplay during SARS-CoV-2 variants infection.

Introduction: The emergence of several SARS-CoV-2 variants during the COVID pandemic has revealed the impact of variant diversity on viral infectivity and host immune responses. While antibodies and CD8 T cells are essential to clear viral infection, the protective role of innate immunity including macrophages has been recognized. The aims of our study were to compare the infectivity of different SARS-CoV-2 variants in monocyte-derived macrophages (MDM) and to assess their activation profiles and the role of ACE2 (Angiotensin-converting enzyme 2), the main SARS-CoV-2 receptor. We also studied the ability of macrophages infected to affect other immune cells such as γδ2 T cells, another partner of innate immune response to viral infections. Results: We showed that the SARS-CoV-2 variants α-B.1.1.7 (United Kingdom), ß-B.1.351 (South Africa), γ-P.1 (Brazil), δ-B.1.617 (India) and B.1.1.529 (Omicron), infected MDM without replication, the γ-Brazil variant exhibiting increased infectivity for MDM. No clear polarization profile of SARS-CoV-2 variants-infected MDM was observed. The ß-B.1.351 (South Africa) variant induced macrophage activation while B.1.1.529 (Omicron) was rather inhibitory. We observed that SARS-CoV-2 variants modulated ACE2 expression in MDM. In particular, the ß-B.1.351 (South Africa) variant induced a higher expression of ACE2, related to MDM activation. Finally, all variants were able to activate γδ2 cells among which γ-P.1 (Brazil) and ß-B.1.351 (South Africa) variants were the most efficient. Conclusion: Our data show that SARS-CoV-2 variants can infect MDM and modulate their activation, which was correlated with the ACE2 expression. They also affect γδ2 T cell activation. The macrophage response to SARS-CoV-2 variants was stereotypical.

Impact of Sex Hormones on Macrophage Responses to Coxiella burnetii.

Introduction: Q fever, a zoonosis caused by Coxiella burnetii, affects more males than females despite a similar level of exposure. A protective role of estradiol has been reported in mice, suggesting that sex hormones are involved in C. burnetii infection. We wondered whether the responses of monocytes and monocyte-derived macrophages (MDMs) to C. burnetii are influenced by sex hormones. Materials and Methods: The bacterial intracellular fate in monocytes was studied using quantitative PCR, and monocyte cytokine production in response to C. burnetii was assessed using qRT-PCR and immunoassays. Before infection, MDMs from males and females were incubated with testosterone and estradiol, respectively. Results: Bacterial uptake and persistence were similar in monocytes from males and females but were slightly increased in male MDMs. The expression of inflammatory genes, including those encoding TNF and CXCL10, was higher in MDMs from females than in MDMs from males infected by C. burnetii. Adding testosterone to male MDMs amplified their immunoregulatory properties, including increased expression of IL10 and TGFB genes and TGF-ß production in response to C. burnetii. In contrast, adding estradiol to MDMs from females had no effect on their inflammatory profile. Conclusion: The stronger inflammatory profile of macrophages from females may have a protective role, likely under estrogen control, while testosterone may affect disease progression by promoting an anti-inflammatory response. This finding may have consequences for personalized management of patients with Q fever.

Sexual Dimorphism and Gender in Infectious Diseases.

Epidemiological studies and clinical observations show evidence of sexual dimorphism in infectious diseases. Women are at less risk than men when it comes to developing most infectious diseases. However, understanding these observations requires a gender approach that takes into account an analysis of both biological and social factors. The host's response to infection differs in males and females because sex differences have an impact on hormonal and chromosomal control of immunity. Estradiol appears to confer protective immunity, while progesterone and testosterone suppress anti-infectious responses. In addition, genetic factors, including those associated with sex chromosomes, also affect susceptibility to infections. Finally, differences in occupational activities, lifestyle, and comorbidities play major roles in exposure to pathogens and management of diseases. Hence, considering sexual dimorphism as a critical variable for infectious diseases should be one of the steps taken toward developing personalized therapeutic approaches.