Cell-type specific innate immune responses shape rabies virus tropism

Abstract

Viral tropism, or the specificity of a particular virus to infect a certain cell type, is crucial in determining virus replication, viral spread, and ultimately host survival. Rabies, one of the deadliest known zoonotic diseases, is still causing 60.000 human deaths annually. Upon central nervous system (CNS) entry, neurotropic rabies virus (RABV) preserves the neural network by limiting apoptosis and inflammation. To date, we do not fully understand the factors determining RABV tropism and why glial cells are unable to clear RABV from the infected brain. Here, we compare susceptibilities and innate immune responses of CNS cell types towards infection with virulent dog RABV Tha and less virulent Th2P-4M in vitro , highlighting differences in cellular susceptibility and antiviral responses. Less virulent Th2P-4M bears mutations introduced in viral phosphoprotein (P-protein) and matrix protein (M-protein) thereby hindering viral immune evasion of the host nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and Janus kinase (JAK) - signal transducer and activator of transcription protein (STAT) pathways. Our results reveal that human neural stem cell (hNSC)-derived neurons and astrocytes, in contrast to human iPSC-derived microglia, are highly susceptible to Tha and Th2P-4M infection in vitro . Surprisingly, Th2P-4M presents a stronger neurotropism in hNSC-derived CNS cultures compared to Tha suggesting that NF-κB- and JAK-STAT-mediated antiviral host responses are defining RABV replication and thereby its tropism. Further, we show that astrocyte-like (SVGp12) and microglia-like (HMC3) cells protect neuroblastoma cells (SK-N-SH) from Tha infection in vitro . Transcription profiles and quantification of intracellular protein levels revealed major differences in antiviral immune responses mediated by neurons, astrocytes ( IFN B1 , CCL5 , CXCL10 , IL1 B , IL6 , LIF ), and microglia ( CCL5 , CXCL10 , ISG15 , MX1 , IL6 ) upon virulent Tha infection. Overall, we provide evidence that RABV tropism depends on its capability to evade cell-type specific immune responses via P- and M-proteins.

The Causes and Long-Term Consequences of Viral Encephalitis

“…In this line, RABV Tha (the WT strain) and Th2P-4M (a less virulent strain) can replicate more efficiently in human neuroblastoma cell lines (SK-N-SH) as compared to astrocyte-like (SVGp12) and microglia-like (HMC3) cell lines. It has also been reported that RABV only infects human neural stem cells (hNSC) differentiated into hiNeurons and hiAstrocytes, while it does not infect iPSC differentiated into hiMicros ( Feige et al, 2021 ). Interestingly, it has been reported that glial cells display a protective role when co-cultured with infected neurons, reducing and limiting the infection of RABV.…”

“…Interestingly, it has been reported that glial cells display a protective role when co-cultured with infected neurons, reducing and limiting the infection of RABV. Additionally, glial cells differentially express and secrete cytokines such as IL-6, CCL5, and CXCL10, as part of the innate immune response against RABV, which varies depending on the viral strain ( Tian et al, 2018 ; Feige et al, 2021 ).…”

Innate Immune Signaling and Role of Glial Cells in Herpes Simplex Virus- and Rabies Virus-Induced Encephalitis

“…Ray and colleagues provided some evidence that human microglia are susceptible to RABV infection in vitro [127]. Recently, the susceptibility of human induced pluripotent stem cell-derived microglia-like cells in vitro has been questioned [160]. Thus, more research is necessary to assess whether microglia productively support RABV infection.…”

“…Positive viral antigen staining has been demonstrated to occur in neurons, astrocytes, and oligodendrocytes of postmortem human brain tissues [192], whereas infection of SCs has thus far only been shown in a mouse animal model [123]. Fetal human microglia have only stained positive for RABV antigen in vitro (italics) [127]; however, the susceptibility of human induced pluripotent stem cell-derived microglia-like cells has been questioned recently [160]. In postmortem human brain tissues, neurons, astrocytes, and oligodendrocytes have stained positive for HSV antigens [173], whereas infected SCs have only been demonstrated in a mouse animal model [187].…”

Structural and Mechanistic Usage and Preference of Human, Dog, and Bat Receptors by Rabies Virus

“…Rabies virus represents a historically broad host and cellular range with the ability to infect diverse cell types among multiple species (12). Globally, dogs are associated with the human rabies cases in Africa and Asia, which has consequently linked dogs to RABV spillover events (13).…”