A Protein E-PilA Fusion Protein Shows Vaccine Potential against Nontypeable Haemophilus influenzae in Mice and Chinchillas

Abstract

PE-PilA is a fusion protein composed of immunologically relevant parts of protein E (PE) and the majority subunit of the type IV pilus (PilA), two major antigens of nontypeable Haemophilus influenzae (NTHi). Here we report on the preclinical evaluation of PE-PilA as a vaccine antigen. The immunogenic potential of the PE and PilA within the fusion was compared with that of isolated PE and PilA antigens. When injected intramuscularly into mice, the immunogenicity of PE within the fusion was equivalent to that of isolated PE, except when it was formulated with alum. In contrast, in our murine models PilA was consistently found to be more immunogenic as a subentity of the PE-PilA fusion protein than when it was injected as an isolated antigen. Following immunization with PE-PilA, anti-PE antibodies demonstrated the same capacity to inhibit the binding of PE to vitronectin as those induced after PE immunization. Likewise, PE-PilA-induced anti-PilA antibodies inhibited the formation of NTHi biofilms and disrupted established biofilms in vitro. These experiments support the immunogenic equivalence between fused PE-PilA and isolated PE and PilA. Further, the potential of PE-PilA immunization against NTHi-induced disease was evaluated. After intranasal NTHi challenge, colonization of the murine nasopharynx significantly dropped in animals formerly immunized with PE-PilA, and in chinchillas, signs of otitis media were significantly reduced in animals that had received anti-PE-PilA antibodies. Taken together, our data support the use of PE-PilA as an NTHi vaccine antigen.

Complement evasion by the human respiratory tract pathogens Haemophilus influenzae and Moraxella catarrhalis

“…Importantly, GSK has developed a vaccine consisting of protein D, and a fusion protein of the major subunit of the NTHi type IV pilus (PilA) and Protein E [96]. This vaccine preparation is protective in the mouse and chinchilla [97] and has also been found safe in a phase 2 clinical trial giving a partial protection against exacerbations in COPD patients [98]. Moreover, an investigational NTHi-M. catarrhalis vaccine consisting of PilA-Protein E, Protein D and UspA2 has also recently been proven safe in a randomized, observer-blind, placebo-controlled study on COPD patients [99].…”

Nontypeable Haemophilus influenzae Responds to Virus-Infected Cells with a Significant Increase in Type IV Pilus Expression

“…NTHI T4P are essential for many important biological processes that include adherence, twitching motility, colonization, biofilm formation, and competence (16)(17)(18)(19)(20). Due to the importance of NTHI T4P during both asymptomatic colonization and infection, and because expression of the majority subunit of T4P, PilA, is highly conserved among diverse NTHI isolates (16,26,27), the vaccine candidate immunogen PilA is in clinical trials for protection against NTHI-induced exacerbations of COPD (28,29).…”

“…Furthermore, antibodies against PilA prevent the development of, as well as therapeutically resolve, existing experimental NTHI-induced OM in chinchilla models (21,(23)(24)(25). Due to the importance of T4P for NTHI colonization and pathogenesis, and as a result of the conservation of the amino acid sequence of PilA among diverse NTHI strains (16,26,27), PilA is in clinical trials as a candidate vaccine immunogen for the prevention of NTHI-induced exacerbations of COPD (28,29). To further validate the strategy of immunization with PilA against multiple NTHI-induced diseases, it is important to demonstrate T4P expression under microenvironmental conditions that commonly predispose to these diseases and, specifically, under conditions of viral coinfection.…”

Nontypeable Haemophilus influenzae newly released (NRel) from biofilms by antibody-mediated dispersal versus antibody-mediated disruption are phenotypically distinct

“…Our first target is the NTHI T4P, a critical adhesin with multiple roles in adherence, colonization, biofilm formation, twitching motility and competence [ [22] , [23] , [24] , [25] , [26] , [27] , [28] ]. Antibodies against the majority subunit of NTHI T4P (PilA), and specifically a r ecombinant and s oluble form of PilA (‘rsPilA’), induce dispersal of pre-existing NTHI as well as polymicrobial biofilms in vitro , and also those present within the middle ear in a chinchilla model of NTHI-induced OM wherein biofilm dispersal leads to rapid disease resolution [ [29] , [30] , [31] , [32] , [33] , [34] ]. The mechanism for this outcome requires expression of both T4P and LuxS, the latter mediates quorum sensing in NTHI [ [35] , [36] , [37] ].…”