Inflammatory Responses to Non-Typeable Haemophilus influenzae Clinical Isolates from Invasive and Non-Invasive Infections
2025
Brenda Huska | Marina Ulanova
Non-typeable Haemophilus influenzae (NTHi) is often asymptomatically carried in the upper airways but can cause a wide spectrum of disease conditions, from local respiratory tract infections to invasive disease such as sepsis or meningitis. The factors driving NTHi&rsquo:s transition from benign carriage to severe systemic disease remain poorly understood. It is unknown whether NTHi strains associated with invasive or non-invasive disease differ in their capacity to trigger inflammatory responses in innate immune cells. To address this question, we have used an in vitro infection model of human THP-1 cells differentiated to macrophages. To evaluate inflammatory responses, we studied the expression of 3 prototypic pro-inflammatory molecules, ICAM-1, TNF-&alpha:, and IL-1&beta:. The role of lipooligosaccharide in triggering inflammatory responses was assessed using inhibition of Toll-like receptor 4 signaling. Our experiments demonstrated that NTHi strains isolated from cases of invasive and non-invasive infections were similarly able to induce strong activations of macrophage pro-inflammatory responses. Our findings support the hypothesis that the development of invasive versus non-invasive NTHi disease may be more significantly influenced by the adaptive immune response than the innate immune response.
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