Oropouche Virus Infects, Persists and Induces IFN Response in Human Peripheral Blood Mononuclear Cells as Identified by RNA PrimeFlow™ and qRT-PCR Assays

Abstract

Oropouche orthobunyavirus (OROV) is an emerging arbovirus with a high potential of dissemination in America. Little is known about the role of peripheral blood mononuclear cells (PBMC) response during OROV infection in humans. Thus, to evaluate human leukocytes susceptibility, permissiveness and immune response during OROV infection, we applied RNA hybridization, qRT-PCR and cell-based assays to quantify viral antigens, genome, antigenome and gene expression in different cells. First, we observed OROV replication in human leukocytes lineages as THP-1 monocytes, Jeko-1 B cells and Jurkat T cells. Interestingly, cell viability and viral particle detection are maintained in these cells, even after successive passages. PBMCs from healthy donors were susceptible but the infection was not productive, since neither antigenome nor infectious particle was found in the supernatant of infected PBMCs. In fact, only viral antigens and small quantities of OROV genome were detected at 24 hpi in lymphocytes, monocytes and CD11c+ cells. Finally, activation of the Interferon (IFN) response was essential to restrict OROV replication in human PBMCs. Increased expression of type I/III IFNs, ISGs and inflammatory cytokines was detected in the first 24 hpi and viral replication was re-established after blocking IFNAR or treating cells with glucocorticoid. Thus, in short, our results show OROV is able to infect and remain in low titers in human T cells, monocytes, DCs and B cells as a consequence of an effective IFN response after infection, indicating the possibility of leukocytes serving as a trojan horse in specific microenvironments during immunosuppression.

Characterization of experimental Shuni virus infection in the mouse

“…Studies on the related Oropouche virus indicate that the virus enters the CNS in mice by at least 3 different routes: by the neural route, by crossing the blood-brain barrier, and by the Trojan horse mechanism using infected leukocytes and monocytes. 14,16 In the present study, the brain stem was the most severely affected area in the majority of animals showing meningoencephalitis. Viral RNA was most consistently and most abundantly found in the spinal cord, brain stem, and diencephalon.…”

Neural Infection by Oropouche Virus in Adult Human Brain Slices Induces an Inflammatory and Toxic Response

“…We therefore determined the levels of cytokines in the conditioned medium of OROV-infected human brain slices by ELISA. Elevated levels of cytokines have been described as an important initial response to experimental virus infection, including against OROV ( Rempel et al, 2005 ; Kawanokuchi et al, 2006 ; Amorim et al, 2020 ). Interestingly, we observed a significant increase in TNF-α release by brain slices infected with OROV, as compared to control slices ( Figure 5A ).…”

“…Once inside the rodent CNS, OROV infection results in glial activation and neuronal cell death ( Rodrigues et al, 2011 ; Santos et al, 2012 ). It has been shown that OROV infects human leukocytes and monocytes, which could result in CNS invasion by the Trojan horse mechanism ( de Souza Luna et al, 2017 ; Amorim et al, 2020 ). Despite these important findings of OROV neuroinfection, the human brain susceptibility to OROV infection has not yet been investigated in detail.…”

Oropouche virus: A neglected global arboviral threat

“…Research is primarily focused on understanding the mechanism by which OROV infects the CNS. Experimental animals such as mice and hamsters have been used to study the infection ( Ribeiro Amorim et al., 2020 ; Almeida et al., 2021 ). In some studies, animals inoculated with OROV developed systemic infection with neurological motor impairment and paralysis, suggesting hematogenous transmission to the brain and liver ( da Silva Menegatto et al., 2023 ).…”