Neurologic Alterations Due to Respiratory Virus Infections

Bohmwald, Karen; Gálvez, Nicolás M. S.; Ríos, Mariana; Kalergis, Alexis M.

Additionally, the hypothesis of the transneural invasion was corroborated in a study performed by Matsuda et al. (2004) , which showed that IAV reaches CNS mainly via the vagus nerve (Figure 2) . Moreover, through an in vitro assay-utilizing neuron cultures in a compartmentalized system-authors suggested that the mechanism of the neurotropic H5N3 to reach CNS is a retrograde axonal transport (Matsuda et al., 2005) . Another research using the H5N1 IAV (Hong Kong/483/97) also found that both RNA and viral antigens were detected, first in the vagal and trigeminal ganglia, then later in the brainstem (Park et al., 2002) . The next step in the research was to evaluate in more detail the effects of IV in the brain of challenged mice. In this context, Jang et al. (2009 Jang et al. ( , 2012 observed that mice challenged intranasally with H5N1(Vietnam/1203/04), viral detection in CNS was positive at 3 days post-infection and that the virus can infect neurons and microglia but not astrocytes (Figure 2) . In addition to this, they report that H5N1 infection promotes microglial apoptosis, inducing an inflammatory state, which lasts up to 90 days post-infection, similarly to the idiopathic Parkinson's disease in human (Jang et al., 2009) . Moreover, the authors show a loss in dopaminergic neurons in about a 17%, that began as a local immune response that could contribute to CNS disease as is described in humans (Jang et al., 2009) . Later research demonstrated that the recovery of the neuronal lasted until 90 days post-infection and that, mainly in the substantia nigra pars compacta (SNpc), the profile of cytokines was altered due to the H5N1 infection (Jang et al., 2012) .