Prevalence, distribution, and sequence diversity of hmwA among commensal and otitis media non-typeable Haemophilus influenzae

Abstract

Nontypeable Haemophilus influenzae (NTHi) are Gram-negative coccobacilli that colonize the human pharynx, their only known natural reservoir. Adherence to the host epithelium facilitates NTHi colonization and marks one of the first steps in NTHi pathogenesis. Epithelial cell attachment is mediated, in part, by a pair of high molecular weight (HMW) adhesins that are highly immunogenic, antigenically diverse, and display a wide range of amino acid diversity both within and between isolates. In this study, the prevalence of hmwA, which encodes the HMW adhesin, was determined for a collection of 170 NTHi isolates recovered from the middle ears of children with otitis media (OM isolates) or throats of healthy children (commensal isolates) from Finland, Israel, and the U. S. Overall, hmwA was detected in 61% of NTHi isolates and was significantly more prevalent (P = 0.004) among OM isolates than among commensal isolates; the prevalence ratio comparing hmwA prevalence among ear isolates with that of commensal isolates was 1.47 (95% CI (1.12, 1.92)). Ninety-five percent (98/103) of the hmwA-positive NTHi isolates possessed two hmw loci. To advance our understanding of hmwA binding sequence diversity, we determined the DNA sequence of the hmwA binding region of 33 isolates from this collection. The average amino acid identity across all hmwA sequences was 62%. Phylogenetic analyses of the hmwA binding revealed four distinct sequence clusters, and the majority of hmwA sequences (83%) belonged to one of two dominant sequence clusters. hmwA sequences did not cluster by chromosomal location, geographic region, or disease status.

Transformed Recombinant Enrichment Profiling Rapidly Identifies HMW1 as an Intracellular Invasion Locus in Haemophilus influenzae

“…HMW1A and HMW2A display wide amino acid diversity both within and between isolates, with the region of lowest sequence identity in the host cell binding domain, which has been predicted to affect tissue tropism and immune evasion [ 42 , 59 , 63 – 67 ]. Phylogenetic analyses of the HMW adhesin binding domain has revealed four distinct sequence clusters, and the majority of sequences belonging to one of two dominant sequence clusters [ 41 ]. Of note, 86-028NP and strain 12 hmw1A binding domains belong to clusters 4 and 2, respectively, which might contribute to their strong and intermediate phenotypes; future studies using mosaic proteins with binding domains from distinct clusters and using multiple human cell lines could identify any clade-specific functions for HMW proteins.…”

Efficacy of 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine against acute otitis media and nasopharyngeal carriage in Panamanian children – A randomized controlled trial

“…It is difficult to conclude on the clinical relevance of the limited (or no) effect of vaccination on overall NTHi carriage, especially if only a pathogenic subset of NTHi is actually responsible for clinical AOM. 70 By analogy, if one had only considered 7vCRM effects on overall pneumococcal colonization, with no net decrease, one might have concluded that the vaccine would not affect pneumococcal AOM; instead, it was necessary to look specifically at the vaccine-type carriage and vaccine-type pneumococcal disease.…”

Evidence of the presence of nucleic acids and β-glucan in the matrix of non-typeable Haemophilus influenzae in vitro biofilms

“…These proteins are synthesized by ≈60% of NT Hi isolates, and 90% of these possess two HMW adhesin-coding genes25. Interestingly, hmw genes are present in strains 86–028NP26 and 37527, but absent in strain Rd KW20.…”