Lung pathology due to hRSV infection impairs blood–brain barrier permeability enabling astrocyte infection and a long-lasting inflammation in the CNS

Abstract

The human respiratory syncytial virus (hRSV) is the most common infectious agent that affects children before two years of age. hRSV outbreaks cause a significant increase in hospitalizations during the winter season associated with bronchiolitis and pneumonia. Recently, neurologic alterations have been associated with hRSV infection in children, which include seizures, central apnea, and encephalopathy. Also, hRSV RNA has been detected in cerebrospinal fluids (CSF) from patients with neurological symptoms after hRSV infection. Additionally, previous studies have shown that hRSV can be detected in the lungs and brains of mice exposed to the virus, yet the potential effects of hRSV infection within the central nervous system (CNS) remain unknown. Here, using a murine model for hRSV infection, we show a significant behavior alteration in these animals, up to two months after the virus exposure, as shown in marble-burying tests. hRSV infection also produced the expression of cytokines within the brain, such as IL-4, IL-10, and CCL2. We found that hRSV infection alters the permeability of the blood-brain barrier (BBB) in mice, allowing the trespassing of macromolecules and leading to increased infiltration of immune cells into the CNS together with an increased expression of pro-inflammatory cytokines in the brain. Finally, we show that hRSV infects murine astrocytes both, in vitro and in vivo . We identified the presence of hRSV in the brain cortex and colocalizes with vWF, MAP-2, Iba-1, and GFAP, which are considered markers for endothelial cells, neurons, microglia, and astrocyte, respectively. hRSV-infected murine astrocytes displayed increased production of nitric oxide (NO) and TNF-α. Our results suggest that hRSV infection alters the BBB permeability to macromolecules and immune cells and induces CNS inflammation which can contribute to the behavioral alterations observed on infected mice. A better understanding of the neuropathy caused by hRSV could help to reduce the potential detrimental effects on the CNS in hRSV-infected patients.

Contribution of Pro-Inflammatory Molecules Induced by Respiratory Virus Infections to Neurological Disorders

“…These cells not only were susceptible to the hRSV infection but also increased levels of IL-6 and TNF-α were detected in the supernatant of N2a hRSV-infected cells [ 151 ]. According to the fact that hRSV infection promotes learning and behavioral impairment and possibly infects neurons, new data showed that hRSV could disrupt the BBB, promoting immune cell infiltration [ 66 ]. Moreover, the behavioral alteration reporter previously in hRSV infected mice can be observed up to 60 days p.i.…”

“…Moreover, the behavioral alteration reporter previously in hRSV infected mice can be observed up to 60 days p.i. and also increased levels of anti-inflammatory molecules, such as IL-4 and IL-10, and pro-inflammatory molecules including CCL2 were found in the brain of these mice [ 66 ]. Moreover, GFAP was found elevated in hRSV-infected mice′s brains, suggesting that which suggest that are active and possibly causing chronic inflammation [ 66 ].…”

“…and also increased levels of anti-inflammatory molecules, such as IL-4 and IL-10, and pro-inflammatory molecules including CCL2 were found in the brain of these mice [ 66 ]. Moreover, GFAP was found elevated in hRSV-infected mice′s brains, suggesting that which suggest that are active and possibly causing chronic inflammation [ 66 ]. Besides infecting neurons, hRSV was able to infect endothelial cells, microglia, and astrocytes, being these last cells infected in a higher percentage [ 66 ].…”

“…Moreover, GFAP was found elevated in hRSV-infected mice′s brains, suggesting that which suggest that are active and possibly causing chronic inflammation [ 66 ]. Besides infecting neurons, hRSV was able to infect endothelial cells, microglia, and astrocytes, being these last cells infected in a higher percentage [ 66 ]. Primary cultures of astrocytes infected with hRSV showed elevated amounts of anti-inflammatory molecules, such as IL-4, IL-10, and pro-inflammatory molecules including TNF-α during the first 12h p.i.…”

“…It is known that some viruses, such as influenza, hRSV, coronaviruses, among others, can complete their viral cycle in CNS cells and further cause alterations in normal function [ 25 , 65 , 66 , 67 ]. However, viral infections can also cause CNS inflammation without brain invasion and lead to alterations in this tissue′s function that could cause neurological damage.…”