Adjunct antibody therapy for severe antibiotic-resistant Acinetobacter baumannii infections

Unlike in the UK and other Western countries, the bacteria Acinetobacter baumannii is a common cause of pneumonia and other infections in Asian countries. Unfortunately A. baumannii both often causes severe infections and is frequently highly resistant to antibiotics, including penems and extended spectrum penicillins, and A. baumannii infections therefore have a high mortality and require considerable hospital resources. We will investigate whether antibodies that bind to the surface of A. baumannii bacteria could be used as way of providing additional treatment to patients with an A. baumannii infection along with antibiotics. We will look for several protein targets for an antibody therapy that can increase killing of A. baumannii by human white cells or which by inhibiting mechanisms of antibiotic resistance makes a previously ineffective antibiotic able to kill A. baumannii. To do so we will:
Aims 1 and 2. Use information that we have recently obtained on the gene content of 300 Thai A. baumannii strains to identify proteins present in most strains, and use these to construct what is called an antigenome array. Antigenome arrays allow all the proteins that cause an antibody response to be identified, and we will use the A. baumannii conserved protein antigenome array to identify which proteins can cause an antibody response after human or mouse A. baumannii infections.
Aims 3. Identify which A. baumannii proteins are abundant on the bacteria during infection or in response to antibiotics using a technology called RNAseq to see which genes are highly expressed during infection or when the bacteria has been stressed by antibiotics; these genes should b particularly good candidates for an antibody therapy.
Aim 4. Use the data obtained in aims 1 to 3 to identify which A. baumannii proteins should be investigated further as potential targets for an antibody therapy. We will make each protein antigen and obtain rabbit antibodies to the protein to test the ability of the antibody to recognise and kill different A. baumannii strains using laboratory assays of immune function and mouse models of infection. From these data we select a few protein antigens for use in a protective multivalent antibody therapy that targets several important proteins rather than just individual protein antigens as targeting several proteins should make the treatment more effective as a therapy.
Aim 5. To identify which patients with A. baumannii infection and when during infection those patients could benefit from an antibody therapy we will collect data on 100 Thai patients with proven A. baumannii infection. In addition we will purify antibodies developing in these patients as a result of the A. baumannii infection for use in our blood infection model to confirm that antibody therapy can inhibit A. baumannni growth in the blood or resistance to antibiotics.
Overall the project will identify which A. baumannii proteins would make good targets for an antibody therapy and confirm the potential of this approach for treating antibiotic resistant A. baumannii infections in Thailand and other Asian countries. By allowing experienced research scientists who work on bacterial infections to start investigating A. baumanii as well, the project will also increase the number of researchers investigating how to combat antibiotic resistant bacteria both in the UK and in Thailand.

Acinetobacter baumannii is a major cause of severe infections in Asian LMICs and has high levels of resistance to multiple antibiotics. To counter the threat of A. baumannii infections in LMICs will require the rapid introduction of new therapies which don't stimulate antibiotic resistance. To address this need we will develop an adjunct multivalent antibody therapy against protein antigens to promote A. baumannii clearance and improve antibiotic efficacy. We will use our recent A. baumannii genome data for 232 strains isolated from Thai patients to construct a comprehensive protein microarray of conserved proteins. This will be probed with sera from Thai subjects recovering from A. baumannii infection and from mice exposed to non-fatal A. baumannii infection to identify antigenic proteins. RNAseq of bacteria recovered from mouse and ex-vivo blood models of infection will identify A. baumannii proteins that are highly expressed during infection and in response to antibiotics and therefore are suitable targets for an antibody therapy. From these data, we will select protein antigens for testing as targets for antibody therapy using in vitro immune assays and mouse models of A. baumannii infection. The most effective antigens will be combined for a multivalent antibody therapy. To better define the role of adjunct antibody therapy we will prospectively collect clinical data on 100 Thai patients with proven A. baumannii infection. In addition, we will purify from these subjects antibody the above data demonstrate are effective at controlling A. baumannii infection for efficacy and dose response testing using a human blood infection model. Overall, the project will develop a novel antibody adjunct therapy for use in severe A. baumannii infections in LMICs that can help combat antibiotic resistance, and provide the clinical and in vitro proof of principle data important for further clinical development of the therapy.

Given the importance of AMR bacterial infections especially in LMICs, the proposed studies could make a major impact for the health and well-being of humans. A. baumannii infections are an under-appreciated yet common cause of pneumonia in Asia and have very high rates of antibiotic resistance; as a consequence A. baumannii has been nominated as the number 1 antimicrobial resistance threat by the WHO. Our approach will develop a novel adjunct therapy against A. baumannii that will be able to reduce the substantial morbidity and mortality caused by this organism in LMICs (and also as a cause of nosocomial infections in industrialised countries).

There will be four main area of impact from this research:

Scientific impact:
The research in this project will provide a platform for the production of adjunct antibody therapy against A. baumannii. The data will give a comprehensive overview of the potential efficacy of this approach and characterise a multivalent antibody therapy for future clinical development. These data are likely to be of interest to a wide range of academic researchers investigating bacterial infection. There is also likely to be considerable interest from industry and where appropriate we will exploit our close links with GSK, Pfizer, VaxAlta and Malicisbo. We will use licensing agreements through our respective technology transfer offices to ensure an antibody therapy developed in this proposal can be effectively exploited. The antigens or live attenuated A. baumannii strains identified by this proposal will also be of interest as vaccine targets, an area of potential commercial interests that will be exploited as described above for the antibody therapy approach. The detailed data and physical resources the proposal will generate (listed in academic beneficiaries section) will be invaluable for other researchers in the field.

Direct economic impact:
Our program will primarily offer a potential new treatment for A. baumannii infections that will be important for Asian LMICs where this pathogen is a common cause of community and nosocomially acquired disease with a high mortality. An effective adjunct therapy will reduce costs incurred treating severe A. baumannii infections by reducing admission to intensive care and the use of expensive antibiotics. In addition commercial development of this approach could provide significant benefits to the UK economy.

Societal:
An effective adjunct treatment for A. baumannii infections in Asian LMICs will reduce the use of reserved antibiotics and this will reduce the drive for the development of antibiotic resistance by bacterial pathogens. The general public in Asian LMICs will benefit from improved treatment of A. baumannii infections due to reduced loss of productivity from affected patients during their illness and recovery period, diversion of medical resources to other conditions, and reduction in the loss of work force expertise and longterm economic deprivation for the patient's dependents in fatal cases.

Outreach:
It is important that any publically funded research benefits the wider public, and we will impart new knowledge from this proposal to the general public utilising the institutes outreach programmes.

Training of researchers:
The project will offer excellent training opportunities for the three researchers. The London based PDRAs will be encouraged to exchange between the two laboratories to ensure maxmm sharing of technical expertise. All researchers will be encouraged to present their work regularly at scientific meetings, and to attend advanced training courses. The multidisciplinary experience that they will gain will add to both the UK and Thai science base in an important and economically vital research area. Training of a Thai researcher will improve research capacity in a field that is of major importance for the Thailand.