Non-typeable Haemophilus influenzae surface protein (NTHi surface protein)

**Non-typeable Haemophilus influenzae surface proteins** are a diverse group of outer membrane proteins expressed by non-capsulated (non-typeable) Haemophilus influenzae (NTHi). Major representatives include high-molecular-weight (HMW) adhesins (HMW1, HMW2), P5, Hap, and Hia, which mediate bacterial colonization and persistence in the human respiratory tract[1][2][4][5][6][8]. - HMW1 and HMW2 are large surface-exposed proteins directly associated with adherence to distinct epithelial surfaces[4][5][6]. - P5 is a major outer membrane protein essential for resistance to complement-mediated serum killing, binding of complement regulators (C4BP, factor H), and contributing to immune evasion[1][3][7][8]. - Hap (Haemophilus adherence and penetration) is an autotransporter protein with serine protease and adhesive activities, promoting adherence and limited invasion[2][8]. - Hia is a high-molecular-weight non-pilus adhesin found in a subset of NTHi strains, with strong homology to the Hsf protein of encapsulated strains and serving a similar adhesive function when HMW proteins are absent[2][6]. These proteins are proposed as major vaccine and immunotherapy targets due to their surface exposure, crucial role in colonization and immune evasion, and ability to trigger host immune responses[5][8]. However, high genetic variability among NTHi strains, phase variation, and antigenic heterogeneity remain substantial barriers to universal vaccine or therapeutic targeting.

Other names

P5Hap (Haemophilus adherence and penetration)HMW1HMW2HiaHsfProtein EProtein FP4Outer membrane protein P5HMW adhesins

Potential: Vaccine candidates/antibodies could neutralize adhesive functions, impair colonization, and enhance complement-mediated bactericidal clearance. No approved small molecule or antibody drugs with a defined mechanism of action targeting these proteins as of the current knowledge.