Identification of Umbre Orthobunyavirus as a Novel Zoonotic Virus Responsible for Lethal Encephalitis in 2 French Patients with Hypogammaglobulinemia.

BACKGROUND: Human encephalitis represents a medical challenge from a diagnostic and therapeutic point of view. We investigated the cause of 2 fatal cases of encephalitis of unknown origin in immunocompromised patients. METHODS: Untargeted metatranscriptomics was applied on the brain tissue of 2 patients to search for pathogens (viruses, bacteria, fungi, or protozoans) without a prior hypothesis. RESULTS: Umbre arbovirus, an orthobunyavirus never previously identified in humans, was found in 2 patients. In situ hybridization and reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) showed that Umbre virus infected neurons and replicated at high titers. The virus was not detected in cerebrospinal fluid by RT-qPCR. Viral sequences related to Koongol virus, another orthobunyavirus close to Umbre virus, were found in Culex pipiens mosquitoes captured in the south of France where the patients had spent some time before the onset of symptoms, demonstrating the presence of the same clade of arboviruses in Europe and their potential public health impact. A serological survey conducted in the same area did not identify individuals positive for Umbre virus. The absence of seropositivity in the population may not reflect the actual risk of disease transmission in immunocompromised individuals. CONCLUSIONS: Umbre arbovirus can cause encephalitis in immunocompromised humans and is present in Europe.

Genetically Intact but Functionally Impaired HIV-1 Env Glycoproteins in the T-Cell Reservoir.

HIV-infected subjects under antiretroviral treatment (ART) harbor a persistent viral reservoir in resting CD4+ T cells, which accounts for the resurgence of HIV replication after ART interruption. A large majority of HIV reservoir genomes are genetically defective, but even among intact proviruses few seem able to generate infectious virus. To understand this phenomenon, we examined the function and expression of HIV envelope glycoproteins reactivated from the reservoir of four HIV-infected subjects under suppressive ART. We studied full-length genetically intact env sequences from both replicative viruses and cell-associated mRNAs. We found that these Env proteins varied extensively in fusogenicity and infectivity, with strongest functional defects found in Envs from cell-associated mRNAs. Env functional impairments were essentially explained by defects in Env protein expression. Our results support the idea that defects in HIV Env expression, preventing cytopathic or immune HIV clearance, contribute to the persistence of the HIV T-cell reservoir in vivoIMPORTANCE In most individuals, evolution of HIV infection is efficiently controlled on the long-term by combination antiviral therapies. These treatments, however, fail to eradicate HIV from the infected subjects, a failure that results both in resurgence of virus replication and in resumption of HIV pathogenicity when the treatment is stopped. HIV resurgence, in these instances, is widely assumed to emerge from a reservoir of silent virus integrated in the genomes of a small number of T lymphocytes. The silent HIV reservoir is mostly composed of heavily deleted or mutated HIV DNA. Moreover, among the seemingly intact remaining HIV, only very few are actually able to efficiently propagate in tissue culture. In this study, we find that intact HIV in the reservoir often carry strong defects in their capacity to promote fusion to neighboring cells and infection of target cells, a defect related to the function and expression of the HIV envelope glycoprotein. Impaired envelope glycoprotein expression and function could explain why cells harboring these viruses tend to remain undetected and unharmed in the reservoir.