Assessing the function of pneumococcal neuraminidases NanA, NanB and NanC inin vitroandin vivolung infection models using monoclonal antibodies

Abstract

Streptococcus pneumoniae isolates express up to three neuraminidases (sialidases), NanA, NanB and NanC, all of which cleave the terminal sialic acid of glycan-structures that decorate host cell surfaces. Most research has focused on the role of NanA with limited investigations evaluating the roles of all three neuraminidases in host-pathogen interactions. We generated two highly potent monoclonal antibodies (mAbs), one that blocks the enzymatic activity of NanA and one cross-neutralizing NanB and NanC. Total neuraminidase activity of clinical S. pneumoniae isolates could be inhibited by this mAb combination in enzymatic assays. To detect desialylation of cell surfaces by pneumococcal neuraminidases, primary human tracheal/bronchial mucocilial epithelial tissues were infected with S. pneumoniae and stained with peanut lectin. Simultaneous targeting of the neuraminidases was required to prevent desialylation, suggesting that inhibition of NanA alone is not sufficient to preserve terminal lung glycans. Importantly, we also found that all three neuraminidases increased the interaction of S. pneumoniae with human airway epithelial cells. Lectin-staining of lung tissues of mice pre-treated with mAbs before intranasal challenge with S. pneumoniae confirmed that both anti-NanA and anti-NanBC mAbs were required to effectively block desialylation of the respiratory epithelium in vivo. Despite this, no effect on survival, reduction in pulmonary bacterial load, or significant changes in cytokine responses were observed. This suggests that neuraminidases have no pivotal role in this murine pneumonia model that is induced by high bacterial challenge inocula and does not progress from colonization as it happens in the human host.

Staphylococcal Protein A ( spa ) Locus Is a Hot Spot for Recombination and Horizontal Gene Transfer in Staphylococcus pseudintermedius

“…Sialidases are important enzymes for sugar acquisition in bacteria, and their role in disease pathogenesis has been shown in many bacterial pathogens (28). In Streptococcus pneumoniae, sialidases are involved in colonization and infection of the upper and lower murine respiratory tract (29,30).…”

Sialidases From Clostridium perfringens and Their Inhibitors

“…So far many studies have shown that sialidases play important roles in the pathogenesis of pathogenic bacteria, providing nutrition for bacteria and promoting bacterial colonization, bacterial adhesion, bacterial internalization, biofilm formation, and the binding of toxins to host cells (Traving and Schauer, 1998;Vimr et al, 2004;Tong et al, 2005;Pastoriza Gallego and Hulen, 2006;Soong et al, 2006;Severi et al, 2007;Parker et al, 2009;Thompson et al, 2009;Trappetti et al, 2009;Banerjee et al, 2010;King, 2010;Honma et al, 2011;Li et al, 2011;Brittan et al, 2012;Lewis and Lewis, 2012;Awad et al, 2016;Blanchette et al, 2016). Recently, a study found that NanA, NanB, and NanC increased the interaction of S. pneumoniae with human airway epithelial cells (Janesch et al, 2018). Some pathogens also use sialic acid to coat their cell surface, flagella, capsule polysaccharides, or lipopolysaccharides, concealing themselves to evade the host immune system (Severi et al, 2007).…”

Transformation of nonencapsulated Streptococcus pneumoniae during systemic infection

“…S2 ) included the liaFSR genes that sense cell envelope stress 24 , and the other event of 10.2 kbp (Fig. S3 ) included the nanB gene associated with cleavage of host sialic acid 25 .

Figure 3 Genomic comparison of recombination regions involving capsule locus among donor, transformant, and recipient.

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