Mechanisms of Viral Pathogenesis in the Central Nervous System

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications & trials

Abstract

The innate immune response to virus infection has a strong influence on viral pathogenesis, from impacting the initial establishment of infection in the periphery to viral entry into the CNS as well as damage to neurons. Our studies have focused on human cerebral organoid models, animal models and de-identified human patient sera to examine different aspects of viral pathogenesis. In 2024-2025, we examined the relative infection rate of California Serogroup viruses in the state of Montana, examined non-human primates as models for La Crosse virus encephalitis, examined mechanisms of virus-mediated neuronal damage and examined potential therapeutics for treatment of disease as described in the abstracts from our publications below: Potential therapeutics for treatment of encephalitis viruses (PMID:39348391)This study was done in collaboration with Dr. Ron Swanstrom's laboratory from the Univ. of North Carolina, Chapel Hill: A diverse group of RNA viruses have the ability to gain access to the central nervous system (CNS) and cause severe neurological disease. Current treatment for people with this type of infection is generally limited to supportive care. To address the need for reliable antivirals, we utilized a strategy of lethal mutagenesis to limit virus replication. We evaluated ribavirin (RBV), favipiravir (FAV) and N4-hydroxycytidine (NHC) against La Crosse virus (LACV), which is one of the most common causes of pediatric arboviral encephalitis cases in North America and serves as a model for viral CNS invasion during acute infection. NHC was approximately 3 to 170 times more potent than RBV or FAV in neuronal cells. Oral administration of molnupiravir (MOV), the prodrug of NHC, decreased neurological disease development (assessed as limb paralysis, ataxia and weakness, repeated seizures, or death) by 31% (4 mice survived out of 13) when treatment was started on the day of infection. MOV also reduced disease by 23% when virus was administered intranasally (IN). NHC and MOV produced less fit viruses by incorporating predominantly G to A or C to U mutations. Furthermore, NHC also inhibited virus production of two other orthobunyaviruses, Jamestown Canyon virus and Cache Valley virus. Collectively, these studies indicate that NHC/MOV has therapeutic potential to inhibit viral replication and subsequent neurological disease caused by orthobunyaviruses and potentially as a generalizable strategy for treating acute viral encephalitis. Determining the prevalence of encephalitic virus infection in humans (PMID:40133033): Viral encephalitis is often underreported and undiagnosed. To understand the potential causes of viral encephalitis in the state of Montana, USA, we examined the relative incidence of human infections for the California serogroup (CSG) of Orthobunyaviruses by screening random convenience serum samples obtained from different hospitals across Montana. We initially screened deidentified samples for neutralizing antibodies against Jamestown Canyon virus (JCV), a CSG virus that has caused encephalitis in Montana. We then analyzed JCV-positive samples for neutralization of other CSG viruses, and detected neutralizing antibodies against La Crosse virus, California encephalitis virus, and Trivittatus virus. We also found a high level of cross-reactivity, particularly between JCV and California encephalitis virus. Our findings indicate that the relative CSG virus infection rates in humans are quite high, between 21% and 40%. Clinicians should consider CSG viruses in differential diagnosis for cases of encephalitis of unknown etiology in Montana. Examination of animal models of La Crosse virus encephalitis (PMID: 40360698): La Crosse virus (LACV) is a primary cause of pediatric viral encephalitis in the United States but rarely causes disease in adults. We tested whether cynomolgus macaques displayed a similar age-dependent susceptibility to LACV. Immune responses from naïve or LACV infected weanling (9-15 months), juvenile (19-23 months) or adult (> 6 years) animals were measured and infected animals were monitored for disease. Naïve weanling animals had fewer dendritic cells in their blood and weaker induction of IFN-stimulated genes (ISG) and chemokines when PBMCs were stimulated in vitro. While no infected animals developed disease, the weaker innate response in naive weanlings correlated with increased viral RNA in plasma from 2 of 3 infected weanlings out to 7 days post infection (dpi). Activated CD8+ T cells and neutralizing antibody proportions were similar amongst all ages. However, CD4+ T cells proportions were increased in young animals relative to adults. This suggests the CD4+ adaptive response in young animals may be bolstering an initially weak innate response to clear virus. Finally, because macaques were resistant to disease, we infected 3 common marmosets intranasally with LACV. Marmoset were selected due to their susceptibility to viral encephalitis. Although no animals showed disease signs, one animal had evidence of infection in the nasal mucosa out to 23 days with associated vacuolization, edema and immune cell infiltration. Examination of the mechanisms of La Crosse virus induced neuronal death (PMID: 39382324): La Crosse Virus (LACV) encephalitis patients are at risk for long-term deficits in cognitive function due to neuronal apoptosis following virus infection. However, the specific etiology underlying neuronal damage remains elusive. In this study, we examined how differentiation and mitotic inhibition of neuroblastoma cells influence their susceptibility to LACV infection and cell death. Treatment of SH-SY5Y cells with retinoic acid induced a neuronal cell phenotype which was similarly susceptible to LACV infection as untreated cells but had significantly delayed virus-induced cell death. Protein and RNA transcript analysis showed that retinoic acid-treated cells had decreased oxidative stress responses to LACV infection compared to untreated cells. Modulation of oxidative stress in untreated cells with specific compounds also delayed cell death, without substantially impacting virus production. Thus, the oxidative stress response of neurons to virus infection may be a key component of neuronal susceptibility to virus-induced cell death.