Moraxella catarrhalis and nontypeable Haemophilus influenzae are Gram-negative opportunistic respiratory tract pathogens responsible for 60% otitis media cases in children and 4.2 million deaths globally as a result of chronic obstructive pulmonary disease in adults. In-fact Otitis media cases are quite high in children of the Australian indigenous community, where 99% of children will contract this infection by the time they reach 3 years of age, it’s no wonder that it’s the 2nd leading cause of surgery in infants worldwide. Both bacteria have shown to produce beta-lactamase, which has led to emergence of antibiotic resistance. Currently, there’s no licenced vaccine for this infections.
It’s well known that virulence factors are traits that contribute to bacterial pathogenicity, and for many Gram-negative organisms lipopolysaccharide is a known virulence factor. In-fact several studies have suggested that this cell surface glycan could potentially be incorporated into vaccines to prevent infections by these bacteria.
The aim of study is to develop a novel vaccine using lipooligosaccharide of M. catarrhalis and an outer membrane protein from NTHi.
M.catarrhalis strain 2951/3292 wild-types and 2951lgt1/4∆ mutant are grown and LOS isolated using the hot water/phenol extraction method. LOS is then O-deacylated and linker incorporated. Transformed E-coli (consisting OMP26 gene from NTHi) is expressed to produce OMP26 protein and purified. M. catarrhalis LOS is then conjugated to OMP26 protein and tested for immunogenicity in mouse pulmonary challenge model, complement mediated killing via bactericidal assay and antigen-specific ELISAs to determine IgG level and cross reactivity.
To date LOS has been O-deacylated, linker incorporated and OMP26 expressed and purified. The next step is to conjugate the LOS to OMP26. Three subcutaneous immunizations using LOS-OMP26 from 2951lgt1/4∆ is expected to elicit significant increases of serum immunoglobulin-(Ig)G against M. catarrhalis LOS and NTHi in mice, but further in-vivo efficacy studies is required.