The NMRC Infectious Diseases Directorate (IDD) consists of four research departments: Malaria, Enteric Diseases, Viral and Rickettsial Diseases, and Wound Infections.
IDD conducts research on infectious diseases considered to be significant threats to deployed Sailors, Marines, Soldiers, and Airmen. Significant threats are those with the potential to incapacitate a large number of deployed forces over a short time period, hindering the ability of warfighters to accomplish their mission. IDD primarily focuses on three infectious diseases: malaria, bacterial causes of traveler’s diarrhea and dengue fever, and scrub typhus.
The geographical distribution of a disease; the lack of an effective vaccine, treatment, or other control measures; the mode of transmission; and the historical impact during past wars are all factors that determine the importance of an infectious disease to the U.S. Military. In general, the overarching research goal in IDD is to minimize the impact of these infectious diseases by preventing infection or clinical disease. In most cases, the best approach to achieve this goal is through the development of effective and safe vaccines – because of this, most of the biomedical research in IDD is focused on vaccine discovery and testing.
IDD departments have the unique research capability of developing a new vaccine from the conceptual stage through construction, "test tube" evaluation, animal model testing, human volunteer safety and immunogenicity trials to final large-scale human volunteer field trials to prove efficacy as required for FDA licensure of a vaccine. The field testing of vaccines is made easier by IDD's close association with the Navy's overseas medical research laboratories located in Lima, Peru (Naval Medical Research Unit No. 6); Cairo, Egypt (Naval Medical Research Unit No. 3); and the Pacific region (Naval Medical Research Center-Asia and Naval Medical Research Unit No. 2) since these laboratories are located in areas of the world where the target infectious diseases are highly endemic.
With the direct use of recombinant DNA techniques for vaccine delivery combined with genomic and proteomic approaches to discover new vaccine components, the Navy can expect to make rapid progress in the new millennium towards controlling many of the infectious diseases that currently remain as major threats to U.S. military forces deployed around the world.
The Naval Infectious Diseases Diagnostics Laboratory (NIDDL) is a CAP accredited, CLIP certified clinical reference laboratory. The NIDDL provides specialized laboratory diagnostics tests for emerging infectious diseases that the Military Treatment Facilities do not perform. In addition, the NIDDL has the ability to quickly bring on-line diagnostic tests for new emerging diseases.
Malaria Research Department
U.S. military forces are at great risk of developing malaria while deployed in endemic areas. In fact, more person-days were lost among U.S. military personnel due to malaria than to bullets during every military campaign fought in malaria-endemic regions during the 20th century. Malaria also is a major threat to non-military travelers, who face this infection as likely the single greatest health risk associated with travel. To address this threat, researchers within the IDD have been investigating methods to control and conquer malaria for more than two decades. This comprehensive research program is at the forefront of malaria research worldwide.
According to the Center for Disease Control, the natural ecology of malaria involves malaria parasites infecting successively two types of hosts: humans and female Anopheles mosquitoes. In humans, the parasites grow and multiply first in the liver cells and then in the red cells of the blood. In the blood, successive broods of parasites grow inside the red cells and destroy them, releasing daughter parasites ("merozoites") that continue the cycle by invading other red cells.
The blood stage parasites are those that cause the symptoms of malaria. When certain forms of blood stage parasites ("gametocytes") are picked up by a female Anopheles mosquito during a blood meal, they start another, different cycle of growth and multiplication in the mosquito.
After 10-18 days, the parasites are found (as "sporozoites") in the mosquito's salivary glands. When the Anopheles mosquito takes a blood meal on another human, the sporozoites are injected with the mosquito's saliva and start another human infection when they parasitize the liver cells.
Thus the mosquito carries the disease from one human to another (acting as a "vector"). Differently from the human host, the mosquito vector does not suffer from the presence of the parasites.
The malaria life cycle is also more complex that the life cycle of most viruses and bacteria; in order to work effectively, it may be necessary for a vaccine to induce an equally complex immune response that attacks the parasite at multiple stages. As one important initiative, the Malaria Program played a key role in the Malaria Genome Project, a consortium that determined the entire genetic sequence of the most deadly of the four human malaria parasites, P. falciparum.
Navy Malaria Program
The primary objective of the Navy Malaria Program is to develop a vaccine that kills the parasite during its first few days of development in the liver, before it breaks out into the blood. If this approach is successful, it will prevent the clinical manifestation of malaria, which occurs only in conjunction with blood stage infection and not with the liver stage. Such a vaccine would benefit deployed military personnel as well as travelers and other non-immune populations. At the same time, the program is investigating vaccines that would target blood stage infection to limit the severity of symptoms associated with this stage. Both liver and blood stage vaccines, if deployed in endemic areas, could alleviate much of the suffering caused by this parasite in tropical countries.
The program’s strategy is based on the idea that protective immunity will depend on using multiple antigens to induce both cellular and humoral immunity. We are characterizing several promising Plasmodium antigens in a variety of antigen delivery platforms, including plasmid DNA, vaccinia vectors, adenoviral vectors, Venezuelan equine encephalitis replicons, and recombinant proteins. We are testing heterologous prime-boost immunization strategies to find effective combinations of these antigens and vectors. We are using genomic and proteomic strategies to identify novel proteins with potential as vaccine antigens. We are also investigating the protective potential of attenuated malaria parasites.
The Malaria Program’s activities range from discovery research, in which we try to understand the nature of protective immunity, to clinical trials of candidate vaccines, carried out in our clinical trials center on the campus of Walter Reed National Military Medical Center. Successful vaccines can be transitioned to testing in field settings, with collaborating institutions in Africa, Asia, and South America. The Malaria Program also benefits from the Navy’s overseas laboratories, which allow study of the epidemiology of parasite in its native habitat, and also help to coordinate field testing of novel vaccines and drugs.
Infectious diarrhea has historically been a substantial cause of morbidity for deployed U.S. military personnel and continues to the present day in those deployed in the global war on terrorism. Pathogenic bacteria, including Campylobacter, enterotoxigenic Escherichia coli (ETEC), and Shigella, are principal causative agents. These pathogens are major causes of travelers’ diarrhea in civilian populations and endemic diarrheal diseases in young children in resource-limited regions of the globe. While acute infections resolve on their own in three to five days, half of those infected report decrease in job performance - one in ten will go on to develop post-infectious irritable bowel syndrome.
The Enteric Diseases Department’s research program is centered on the development of effective countermeasures to prevent or abate bacterial diarrhea, with most efforts aimed at vaccine research and development.
Research efforts for Campylobacter and ETEC include studies of molecular pathogenesis, antigen discovery, and vaccine development and clinical trials. In addition, the department’s Clinical Trials Branch works closely with the Walter Reed Army Institute of Research (WRAIR) Division of Bacterial and Rickettsial Diseases in the clinical evaluation of new Shigella vaccine candidates.
The department is organized into four closely integrated branches: Molecular Biology, Immunology, Biochemistry, and Clinical Trials. Principal investigators within the program work with a number of extramural academic, industry, and government partners to achieve the goal of developing new-generation vaccines against bacterial diarrhea. In the realm of clinical trials, the WRAIR/NMRC facilities afford access to the WRAIR Pilot Bioproduction Facility for scale-up and manufacture of investigational vaccines and with a state-of-the-art outpatient clinical trials center where Phase I safety and immunogenicity trials are conducted.
The Enteric Diseases Department (EDD) continues to make substantial progress in the development of countermeasures against diarrhea and dysentery caused by Campylobacter, enterotoxigenic Escherichia coli (ETEC), and Shigella.
Enterotoxigenic Escherichia coli Vaccine Research and Development
Most Escherichia coli are normal inhabitants of our environment and gastrointestinal tracts and do not cause disease. However, a number of different so-called diarrheagenic E. coli have the ability to colonize the gastrointestinal tract and cause diarrhea in humans and animals. The most common is enterotoxigenic E. coli (ETEC), which causes disease by attaching to the intestinal lining through specialized projections called fimbriae. Once attached, ETEC multiply and produce toxins that stimulate an outpouring of intestinal fluids, which can cause diarrhea and consequent dehydration. NMRC researchers are developing vaccines that would block attachment and toxin activity, interrupting the infection at its earliest stages, which should reduce the number and severity of ETEC diarrhea cases.
Campylobacter Vaccine Research and Development
Campylobacter jejuni is a relatively newly identified pathogen, yet it has been a focus of the Navy enterics research program since its importance was first recognized. A
food-borne pathogen, Campylobacter jejuni causes a more severe disease than ETEC, causing high fever, severe stomach cramps, headache, and joint pains in addition to diarrhea. NMRC’s Enteric Diseases Department has identified many surface structures of the bacteria, found how it invades human cells, and characterized many aspects of the immune response. This work continues with the use of comparative genomics, expression arrays, and studies to try to better understand the protective immune response, all of which will enable researchers to develop an effective vaccine.
Viral and Rickettsial Diseases Department
The Viral and Rickettsial Diseases Department is comprised of the Viral Diseases Division, the Rickettsial Diseases Division and the Naval Infectious Diseases Diagnostic Laboratory. The primary focus of the Viral Diseases Division is the development of a vaccine to prevent dengue fever; the main objective of the Rickettsial Diseases Division is to develop a scrub typhus vaccine.
Viral Diseases Division
Because of the historic and current military impact of dengue virus infections, the key focus of the Viral Diseases Division is the development of a FDA approved vaccine to prevent dengue fever. The major thrust is on utilizing novel vaccine technologies and several approaches are in pre-clinical investigation. A critical corollary to vaccine development efforts is the exploration of novel and improved measures for immunological protection against dengue infection. This work is critical to the evaluation of vaccine candidates as well as to the understanding of the beneficial and detrimental aspects of the human immune response to natural dengue infections.
Other areas of effort in the Viral Diseases Division are the development of therapeutics for novel and emerging viral diseases and studies that address military relevant viral pathogens to help inform force health protection decision making.
Rickettsial Diseases Division
Rickettsial diseases such as murine typhus, epidemic typhus, scrub typhus, and trench fever, cause significant medical problems for military personnel deployed throughout the world in both wartime and peacetime activities.
Product development: The primary objective of the Rickettsial Diseases Division (RDD) is to develop a vaccine for scrub typhus. Current vaccine development efforts include the use of recombinant proteins and/or modified DNA. A critical corollary to vaccine development includes ongoing projects to characterize cellular and humoral immune responses to scrub typhus infection.
RDD continues to develop assays to detect and identify rickettsia disease-causing pathogens (typhus and spotted fever diseases), orientia (scrub typhus), borrelia (lyme disease), and bartonella (trench and other fevers) in arthropod vectors, clinical specimens and vertebrate hosts. Assays developed at RDD include novel quantitative
real time PCR (qPCR), ELISA, Western blot, LAMP (loop-mediated amplification) and RPA (recombinase polymerase amplification). Validation studies of assays specific for Rickettsia and Orientia tsutsugamushi have been performed to obtain sufficient data to request FDA approval.
Risk Assessment and critical reagent program: RDD uses serological surveys to assess the risk of rickettsia, scrub typhus and leptospirosis to military personnel on an ongoing basis, in multiple regions throughout the world.
RDD maintains one of the largest collections of rickettsial pathogens in the world. Additionally, RDD provides assay reagents, qPCR primers, probes, protocols and training to DoD overseas research laboratories (NAMRU-2, NAMRU-3, NAMRU-6, AFRIMS, USAMRD-G, USAMRD-K), The Department of Homeland Security and other global partners so that researchers can conduct rickettsial detection and identification on-site at facilities throughout the world.
Comparative genomics, proteomics and pathogen discovery: Rickettsial and closely related pathogens often exhibit different virulence or sensitivity to therapeutic drugs. RDD uses a variety of genomic and proteomic approaches to elucidate mechanisms of virulence and facilitate the discovery of new drug targets and vaccine candidates.
RDD has been involved in the discovery, characterization and culture of several new disease agents including: Orientia chuto (UAE), Orientia sp. Chiloè (Chile), Rickettsia asembonensis (Kenya), Candidatus Rickettsia andeanae (Peru), and Bartonella ancashensis (Peru).
Wound Infections Department
Treatment of combat injuries is complicated by the severity of the injuries and the prolonged duration between injury and higher echelon care, often leading to deep seated polymicrobial infections that are even further complicated by the increasing prevalence of antibiotic-resistant bacteria. Following the Navy Surgeon General’s call for research activities that will provide direct benefit to our wounded warfighters, the Navy established the Wound Infections research program with the mission to better understand the complex microbiology and immunology of combat injuries that can be used to develop and evaluate novel strategies and therapeutics to prevent and treat afflicted U.S. military members.
The Wound Infections Department (WID) was established in September 2011 in response to the Navy Surgeon General’s call for research activities that will provide direct benefit to our wounded warfighters. The primary mission of the WID is to develop and evaluate novel and alternative treatment and prevention strategies for skin and soft tissue infections (SSTIs) associated with multidrug-resistant organisms, which have increasingly afflicted U.S. military members wounded in combat.
Immunology of skin and soft tissue infections—Skin and soft tissue infections (SSTIs) in service members, especially those that are caused by community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA), can adversely affect military training and combat missions. Currently, virtually nothing is understood about the changes in humoral immunity that occur during the course of an active SSTI or how humoral immunity changes over time. In collaboration with clinical and research investigators at the Uniformed Services University of the Health Sciences, we are conducting studies that will (1) examine the association between the occurrence of SSTI and pre-exposure/pre-infection antibodies and (2) prospectively examine human humoral and cell mediated responses to CA-MRSA SSTIs in a closed military population. By identifying potential correlate immune of protection for skin and soft tissue infections, particularly against MRSA, is a critical step for developing protective vaccines against Staphylococcus aureus that can protect military troops in training and operational environments.
Alternative therapies for treatment of antibiotic-resistant bacteria—The overall pattern in both military and civilian hospitals is that infections due to multi-drug resistant organisms (MDROs), such as Acinetobacter baumannii and other ESKAPE pathogens, are increasingly common in hospitalized populations. These multi-drug resistant infections increase morbidity and mortality and require broad-spectrum antimicrobial coverage, which in turn may contribute to increasing prevalence of MDROs. The failure of current treatment protocols requires new strategies for combatting these infections. WID is actively involved in investigating a variety of alternative options to supplement antibiotic therapy, including natural plant compounds, commensal microorganism derived antimicrobial and immuno-stimulatory products, antimicrobial proteins from animal and plant sources, synthetic antimicrobial peptides, metal ions, and photodynamic therapy activated nanoparticles. To determine the mechanism of action and therapeutic safety and efficacy, WID investigators continue to develop animal models for high-priority clinical infections (e.g. SSTI, abscess, osteomyelitis) involving the ESKAPE organisms. These preclinical studies are the foundation to support advanced product development and human clinical trials necessary for FDA-approval and clinical use to treat afflicted military personnel.
Phage Therapy for Wound Infections
Bacteriophage (phage) therapy has been researched and used for the treatment of bacterial infections since before the antibiotic era, but has received increasing attention as an alternative therapy to antibiotics due the rapid increase in antibiotic-resistance across the globe. In collaboration with the NMRC Biological Defense Research Directorate (BDRD) and Walter Reed Army Institute of Research (WRAIR) Bacterial Diseases program, Navy WID investigators have launched a Phage Therapy research program that is developing and evaluating phage against the ESKAPE pathogens. Recent findings have shown safety and efficacy in a mouse A. baumannii SSTI model studies are in progress to examine efficacy versus other pathogens in more advanced infections models. Additional objectives include optimization of formulation, dosing, delivery, and investigating the role of host immunity in response to phage and in complementing pathogen clearance. Future aims are to begin human clinical trials for high-priority clinical indications and determine optimal strategies to routine clinical applications of phage therapy alongside current standard of care practices.
Bacteriology Support Services
The WID provides basic bacteriology services in support of the NMRC Regenerative Medicine Department by isolating, identifying, and providing information about the strains of bacteria that are associated with wounds that lead to heterotopic ossification (HO). In collaboration with the Trauma Infectious Disease Outcomes Study (TIDOS) at the Uniformed Services University of the Health Sciences and Walter Reed Army Institute of Research, WID has supported characterization of bacteria isolated from combat injury infections, leading to a better understanding of the complex interplay between host and pathogenic organisms found in these wounds. These findings have not only shed light on the higher risks for non-healing and chronic wounds associated with the presence of pathogens, but has opened a novel area of research investigating the antibacterial activity of host flora bacteria that is a potential avenue to develop novel therapeutics to treat antibiotic-resistant bacteria.