Secretory IgA in Mucosa of Pharynx and Larynx Plays an Important Role against Influenza A Virus Infection in Kidney Yang Deficiency Syndrome Model

Abstract

Objective. Influenza virus poses a major threat to human health and has serious morbidity and mortality which commonly occurs in high-risk populations. Pharynx and larynx of the upper respiratory tract mucosa is the first defense line against influenza virus infection. However, the ability of the pharynx and larynx organ to eliminate the influenza pathogen is still not clear under different host conditions. Methods. In this study, a mouse model of kidney yang deficiency syndrome (KYDS) was used to mimic high-risk peoples. Two different methods of influenza A (H1N1) virus infection by nasal dropping or tracheal intubation were applied to these mice, which were divided into four groups: normal intubation (NI) group, normal nasal dropping (ND) group, model intubation (MI) group, and model nasal dropping (MD) group. e normal control (NC) group was used as a negative control. Body weight, rectal temperature, and survival rate were observed every day. Histopathologic changes, visceral index, gene expressions of H1N1, cytokine expressions, secretory IgA (SIgA) antibodies of tracheal lavage fluids in the upper respiratory tract, and bronchoalveolar lavage fluids were analyzed by ELISA. Results. e MD group had an earlier serious morbidity and mortality than the others. MI and NI groups became severe only in the 6 th to 7 th day after infection. e index of the lung increased significantly in NI, MI, and MD groups. Conversely, indices of the thymus and spleen increased significantly in NC and ND groups. H&E staining showed severe tissue lesions in MD, MI, and NI groups. H1N1 gene expressions were higher in the MD group compared with the MI group on the 3 rd day; however, the MD group decreased significantly on the 7 th day. IL-6 levels increased remarkably, and SIgA expressions decreased significantly in the MD group compared with the NC group. Conclusions. SIgA secretions are influenced directly by different conditions of the host in the pharynx and larynx in the upper respiratory tract mucosa. In the KYDS virus disease mode, SIgA expressions could be inhibited severely, which leads to serious morbidity and mortality after influenza A virus infection. e SIgA expressions of the pharynx and larynx would be an important target in highrisk populations against the influenza A virus for vaccine or antiviral drugs research.

In Nasal Mucosal Secretions, Distinct IFN and IgA Responses Are Found in Severe and Mild SARS-CoV-2 Infection

“…Regarding the SIgA levels, it was reported that these antibodies present in the mucosa are closely associated with the severity of viral infection and the reduction of these levels can compromise severely the local immune response ( 13 ). So, the observation that COVID-19 patients with ARDS presented higher SIgA levels can reinforce the previous literature concerning other respiratory virus.…”

“…According to the literature, reduced airways mucosal SIgA levels leads to an increased risk of developing upper respiratory tract infections (URTI) ( 11 ), mainly by respiratory virus ( 12 ). It is also of utmost highlight that decreased SIgA levels are closely related to the illness severity ( 13 ).…”

Elderly Subjects Supplemented with L-Glutamine Shows an Improvement of Mucosal Immunity in the Upper Airways in Response to Influenza Virus Vaccination

“…It is noteworthy to mention that a reduction in the airways mucosal SIgA levels is associated with a higher risk of upper respiratory tract infection (URTI) development [39] mainly by a respiratory virus [41], such as rhinovirus, respiratory syncytial virus, and influenza virus [42]. In addition, it was reported that lower SIgA levels are associated with illness severity [43].…”

Distinct Immunological Profiles Help in the Maintenance of Salivary Secretory IgA Production in Mild Symptoms COVID-19 Patients

“…According to the literature, the production and release of cytokines by the upper airway’s mucosa, in response to respiratory infection, can elicit different immune response profiles such as Th1, Th2, and Th17, which can help in the production of mucosal specific-SIgA against the infective agent ( 10 ). Among some SIgA features, it is paramount to point out that it was reported that reduction in SIgA levels is closely associated with illness severity ( 13 ). Secretory immunoglobulin A is considered as the “first line of defense” against many different pathogens due to its capacity to directly bind and inhibit many pathogenic agents in the mucosa ( 14 – 16 ).…”