6
Biotechnology Trends Relevant to Warfare Initiatives

INTRODUCTION

Developments in biological and biochemical technologies relevant to modern warfare are advancing rapidly. Technology contributions come from scientists working in academic, military, and industrial environments in many countries. Information from academic laboratories is usually published in open source literature, but advances made both by military research laboratories doing biomedical research and by biotechnology companies are likely to be tightly held secrets or proprietary. Therefore, for the United States to maintain superiority requires being prepared for new developments through constant vigilance, research, and information gathering.

Modern techniques allow easy manipulation of the genetic information carried by viruses, bacteria, parasites, cells, and organisms. One obvious area in which biological research is relevant to the health of warfighters is the development of pathogens that are engineered to be resistant to current antibiotics or vaccines, to be more virulent, or to be more easily transmitted. This area of biological warfare, which has been examined by a number of other committees, is excluded from the tasks of this committee at the request of the Technology Warning Division and is not included in this report.

Beyond biological warfare, however, there are many ways in which biological techniques can be used to alter the mental or physical readiness of troops for battle, to confound current methods for detecting biological or chemical agents in the field, or to divert the energies of troops to tasks that are counterproductive; or, such techniques can be used as means for developing bio-inspired approaches for communication. This chapter highlights examples of some of these technologies and assesses their states of development. The approach taken here involves first postulating new BLUE force capabilities that leverage this burgeoning research field and then evaluating potential RED force applications of related technologies.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 73
Avoiding Surprise in an Era of Global Technology Advances 6 Biotechnology Trends Relevant to Warfare Initiatives INTRODUCTION Developments in biological and biochemical technologies relevant to modern warfare are advancing rapidly. Technology contributions come from scientists working in academic, military, and industrial environments in many countries. Information from academic laboratories is usually published in open source literature, but advances made both by military research laboratories doing biomedical research and by biotechnology companies are likely to be tightly held secrets or proprietary. Therefore, for the United States to maintain superiority requires being prepared for new developments through constant vigilance, research, and information gathering. Modern techniques allow easy manipulation of the genetic information carried by viruses, bacteria, parasites, cells, and organisms. One obvious area in which biological research is relevant to the health of warfighters is the development of pathogens that are engineered to be resistant to current antibiotics or vaccines, to be more virulent, or to be more easily transmitted. This area of biological warfare, which has been examined by a number of other committees, is excluded from the tasks of this committee at the request of the Technology Warning Division and is not included in this report. Beyond biological warfare, however, there are many ways in which biological techniques can be used to alter the mental or physical readiness of troops for battle, to confound current methods for detecting biological or chemical agents in the field, or to divert the energies of troops to tasks that are counterproductive; or, such techniques can be used as means for developing bio-inspired approaches for communication. This chapter highlights examples of some of these technologies and assesses their states of development. The approach taken here involves first postulating new BLUE force capabilities that leverage this burgeoning research field and then evaluating potential RED force applications of related technologies.

OCR for page 73
Avoiding Surprise in an Era of Global Technology Advances Watching People Think I have two children and love them very much. But my love to see God was stronger than my love for my children, and I’m sure that God will take care of them if (sic) I become a martyr…. I’m proud to be the first (sic) female martyr. Reem Saleh Riyashi, Seventh female Islamic Fundamentalist suicide bomber, January 14, 2004 The fact that a woman took part for the first time in a Hamas operation marks a significant evolution… women are like the reserve army—when there is a necessity, we use them. Today we needed her because there are a lot of problems for a man to reach out to Israelis in the West Bank and Gaza. Sheik Ahmed Yassin, Founder, Islamic Resistance Movement (Hamas), January 14, 2004 Washington Post Foreign Service M. Moore, Jerusalem Until now, it has been impossible to understand scientifically how persons can behave in ways that Western political, psychological, and psychiatric criteria define as pathological. This inability to understand motivation has caused U.S. military planning and response strategy to be focused on preemptively, post hoc punishment and on attempts to educate through ineffective traditional propaganda and occasional “active measures.” The reason for the confounding nature of the problem and for the failure of this nation to stem its growth relate directly to the simple fact that traditional Western models of behavior cast such actions as psychopathological. It is likely that these actions, rather than being pathological in the contexts in which they reside, are the actions of rational thought and of educational processes that U.S. leadership has not defined, and that they will escalate until and unless the United States can “watch these people think.” Scientific Methods That May Predict Behaviors Physicians and psychologists are now using a new set of technologies for analyzing brain function. Initial data have been collected and analyzed in three parallel research streams which support the contention that the U.S. research community is now poised to change the paradigm of dealing with behavioral phenomena in subjective Western practice. The technologies of structural magnetic resonance imaging (MRI) and functional MRI (fMRI), magnetoencephalography (MEG), and near-infrared spectroscopy (NIRS) are being newly applied to real-time brain imaging. During the brain scans, the subjects of the experiments observe, through virtual-reality technology, images, sounds, and voice commands, and they also see written text. Online proprietary software ensures in real time that the appropriate (hypothesized from past extensive behavioral research) part of the brain cortex (e.g., the occipital sensory visual and auditory centers) is engaging the “message” presented. Pre- and post-identification of activation levels (blood-oxygen-level-dependent, fMRI and MEG) from cognitive processing (e.g., prefrontal cortex), emotional uploading to that process

OCR for page 73
Avoiding Surprise in an Era of Global Technology Advances (e.g., from the limbic system’s amygdala and para-hippocampal nuclei), and the effects of rational behavior (pre-instructed commands to the subjects) are collected and analyzed. Next-generation experiments will extend this work to a clearer understanding of how the following—(1) cultural affects of personality, fashioned especially in fundamentalist ashrams and Islamic fundamentalist schools for preteenagers; (2) ideographic, tonal, and symbolic languages (e.g., Farsi, Hindi, Mandarin, and Thai) versus linear and lexical (e.g., English and German) languages; and (3) constructs of written materials—engage differently the brains of different individuals. The research is objective and repeatable. It is independent of preassigned values of any cultural disposition or orientation. The neurophysiology of thought is being studied now in experiments that demonstrate the active brain centers that subtend language differences, emotional experience (moral repugnance, fear, anger, disgust, sadness, and pleasure), and value-based religious and personal experience. Brain imaging is an area of active research; while discernible progress has been achieved, its full potential is as yet unknown. Brain-imaging technologies may provide a better understanding of behavior, performance, readiness, and stress that is relevant to troop readiness, understanding of cultural differences in motivation, and prisoner motivation. Additional, related information is provided in Appendix E, which also includes more specific descriptions of how such advances could be used by BLUE forces. COMMITTEE FOCUS: CHALLENGES TO COMMUNICATIONS SUPERIORITY Communications superiority plays a dominant role in the effectiveness of BLUE force operations. This capability relies on sophisticated technologies and flexible networking of the knowledge generated through such technologies. Today U.S. forces “own the C4ISR [command, control, communications, computers, intelligence, surveillance, and reconnaissance] information network,” although the direct challenges described in Chapter 3 are on the horizon. The covert transmission of information between forces is essential to effective timing and control of actions (both offensive and defensive). Achieving RED force command, control, and communications (including intelligence gathering, surveillance, and reconnaissance) among its independent, dispersed units could support effective guerilla engagement of traditional forces. Such communications might involve the transmission and receipt of short messages (e.g., commands that trigger prearranged events, coordination for precision fire, or relocation of operations) or more complex messages (e.g., those establishing strategies, complex timing, tiered responses, or detailed changes in operations). A framework to achieve effective, inexpensive, yet reliable communication between RED force units under these conditions must be easily accessible, undetected by BLUE forces, and sufficiently robust to carry all of the required information in a manner that can be validated. Hiding simple to complex packets of information in easily accessible physical form or in widely accessible databases could support the basic requirements. Integrating such seemingly innocuous databases with traditional mail that is physically handed off, or with a global, instantaneous, free-access communications system could generate the capability for RED force C4ISR across dispersed, independent units. The transmission of encrypted messages across the Internet is commonplace, but it provides no cover of invisibility to its users. Hiding information within seemingly innocuous transmissions (steganography) could further veil the information. A successfully hidden message may be overlooked as a part of something else, whether that is the physical package of the information (such as microdots) or the complexity of the message medium itself (such as hidden information in digital images). For example, steganography can be used for the legitimate validation of image authenticity. The Content ID Forum and the Digital Content Association of Japan have created digital watermarks, equivalent to short

OCR for page 73
Avoiding Surprise in an Era of Global Technology Advances messages, to prevent piracy.1 The information density of such watermarks allows a single letter of ASCII (American Standard Code for Information Interchanges) text to be fixed across three pixels,2 generating enough capacity to carry a small message hidden in the noise of the image signal. However, as document size increases, the induced noise will degrade the quality of the image to the point of becoming detectable. Covert Communications via DNA One inexpensive and reliable way to transmit more complex information might be to hide data or messages in the sequences of DNA or in the databases describing the sequences of DNA (or in the sequences and structural data of proteins) that are so prevalent in the scientific literature. While digital systems are binary in nature, the information content of a DNA database is coded in a base-four sequence represented by the letters A, T, C, and G. (In a physical sense, the actual structure and sequences of DNA that hold a potential data density are more than 1 million gigabits per square inch, compared with a typical PC hard drive of approximately 7 gigabits per square inch.3) Recent publications have projected this approach to the construction of actual DNA containing hidden messages. Typically, data describing functional DNA in the scientific literature contain large stretches of sequences that are not intimately related to the function of the gene. The capacity of the human genome database to hold steganographic data without exceeding the normal noise-to-signal ratio is enormous. Researchers Clelland and Bancroft developed a simple physical methodology to encode and recover secret DNA messages embedded in the 3 million-fold excess of normal human DNA.4 However, there is potentially a much more rapid and simpler way of transmitting the hidden information than physically moving constructed DNA as samples or microdots. Simply encrypting a message into the base-four language of DNA (IBM has developed a language for storing information in DNA sequence data5) might be sufficient to hide messages between RED force teams. Such coded information might seem perfectly normal in the context of daily scientific discussions on the Internet. (See Chart 6-1.) These messages could be transmitted and received quickly, but they would rely on the appearance of scientific validity to remain undetected. More secure transmission of information could be achieved by embedding the encrypted message into the redundant or apparently superfluous regions of a database describing an actual genome (the 1   For more information, see, for example, http://www.cidf.org/japanese/english/docs/gen/cidf-gen-en-38.pdf. Last accessed on February 11, 2005. 2   For more information, see, for example, http://en.wikipedia.org/wiki/Steganography#Steganographic_techniques. Last accessed on February 11, 2005. 3   For more information, see, for example, http://www.kuro5hin.org/story/2004/10/26/02313/946. Last accessed on February 11, 2005. 4   For more information, see, for example, http://inka.mssm.edu/~bancroft/papers/NATURE.pdf. Last accessed on February 11, 2005. Clelland and Bancroft have won a patent for DNA steganographic authentication. Applied DNA Sciences (Los Angeles) is actively pursuing DNA-based authentication of a wide range of materials and has been the subject of recent press coverage. Application of the steganographic potential of DNA (in the form of DNA microdots or packets of DNA transmitted through conventional methods) increases the potential to hide the medium of delivery while further hiding the message or identifier within the DNA itself. Encryption of the base-four lexicon is a logical extension of this approach, but may not be necessary in practical application. Such a physical or database-representation medium for covert message transmission is capable of holding information ranging from single words to very large documents. 5   For more information, see, for example, http://www.bio-itworld.com/news/090904_report6001.html. Last accessed on February 11, 2005.

OCR for page 73
Avoiding Surprise in an Era of Global Technology Advances CHART 6-1 Technology Assessment: Exploitation of DNA Databases for Covert Communications Technology Observables Exploitation of DNA databases for covert communications Registration for access to Web site resident DNA or protein structure databases is easy to obtain but can be tracked. Most such databases can be copied but not modified by the user (limiting their usefulness for transmitting messages to the provision of the legitimate database with its well-known signal-to-noise ratio). Comparison of the signal-to-noise ratio of candidate messages to the authentic database might indicate the presence of hidden data. Open literature Web sites that do not require registration and allow some manipulation of the data could be candidate mailboxes. The convergence of (1) Internet discussion of DNA databases that are small enough to afford short upload and download characteristics and (2) unlikely participants might suggest steganography. Accessibility Maturity Consequence Level 1 Warning Threaten BLUE communications superiority. “noise” regions among the “signal” regions of legitimate scientific interest). Typical noise-to-signal ratios in such data could effectively hide large amounts of information. This approach might be expanded to include the data sets for three-dimensional structures of proteins to hide the coordinates for a literal map of a battle theater. To the extent that Internet access (telephone, digital subscriber line, cable, wireless, satellite) is available and reliable, communication between RED force units might approach real-time capability. Many approaches to encryption and steganographic hiding could be imagined. The potential of this approach derives from the large “noise” component of current databases and the ease with which such databases are shared in the global community. As molecular biology defines the noise regions, it may become easier to identify false or incorrect databases. Covert Communications via Bacteriorhodopsin Biomolecular electronics are being applied to the encryption of messages using protein-based holograms. Much of the work has focused on the use of bacteriorhodopsin, a protein produced by the salt marsh archaebacteria Halobacterium salinarium found in high-temperature brine pools. This transmembrane protein is a green, sunlight-driven proton pump that can maintain its structure and function at temperatures as high as 140°C (Shen et al., 1993). The native molecule is composed of three protein chains, each of which has a molecule of retinal bound deep inside. Retinal contains a string of carbons that strongly absorb light. When a photon is absorbed, it causes a change in the conformation of the

OCR for page 73
Avoiding Surprise in an Era of Global Technology Advances molecule from a straight form to a bent form that powers the pumping of protons.6 The protein has been adapted for device application because it can undergo structural changes induced by light once every few milliseconds for hundreds of millions of times. As stated in the NRC report Opportunities in Biotechnology for Future Army Applications: Bacteriorhodopsin has excellent holographic properties because of the large change in refractive index that occurs following light activation. It converts light into a refractive index change with approximately 65% efficiency. Furthermore, the protein is 10 times smaller than the wavelength of light. This means that the resolution of the thin film is determined by the diffraction limit of the optical geometry rather than the graininess of the film. Bacteriorhodopsin can absorb 2 photons simultaneously and therefore can be used to store information in 3 dimensions by using 2-photon architectures (NRC, 2001). Bacteriorhodopsin can also be genetically engineered to do different tasks and adapted for numerous protein-based devices (Wise et al., 2002; Hillebrecht et al., 2004). Mutations have been introduced that enhance its holographic properties, and one of the most successful device applications has been in the development of holographic and volumetric three-dimensional (3-D) memories. In principle, an optical 3-D memory can store roughly three orders of magnitude more information than that on a 2-D optical disk in the same size enclosure. These protein-based memories have the advantage of the memory medium’s being extremely rugged. It can withstand substantial gravitational forces and is unaffected by high-intensity electromagnetic radiation and cosmic rays. These memories are also lightweight and insensitive to moisture. Therefore, protein-based polymer cuvettes would be a suitable memory medium for troops to carry with them into harsh environments. Bacteriorhodopsin-based films can also be produced for use in developing pattern-recognition devices and large-scale associative memories and associative processors that would allow for the processing of intelligence and sensor data in visual formats from multiple sources in real time (NRC, 2001). One company offering bacteriorhodopsin for sale for use in “optical data processing, optical switches, holography, information processing, nonlinear optics and light sensors” is the Consortium für Elektrochemische Industrie GmbH in Munich. (See Chart 6-2.) The current problem with the use of this technology is that, to be read, such a protein-based hologram cube (the size of a sugar cube) requires a light source the size of a large suitcase. However, if the light sources and instrumentation are shrunk to the size of a personal digital assistant, the cube becomes practical to be carried and read in the field. COMMITTEE FOCUS: CHALLENGES TO BATTLE READINESS Troops must be ready to respond to threats on short notice as well as to participate in planned military actions. Disease that incapacitates but does not kill (as opposed to the effects of weapons of mass destruction) can be disabling and the source of the infection difficult to determine. Particular vulnerabilities are the foodborne, vectorborne, and zoonotic diseases that could be introduced locally and for which vaccines, good diagnostics, and treatment are not available. A number of pathogens could be envisioned for such development. Two that are particularly likely are noroviruses and avian influenza virus. The committee notes that such developments fall outside the realm of acceptable offense from the BLUE perspective. As observed in Chapter 1, however, BLUE forces may well encounter RED forces that are willing to employ capabilities that the United States would not consider. 6   For more information, see, for example, Protein Data Bank, http://www.rcsb.org/pdb/molecules/pdb27_1.html. Last accessed on February 11, 2005.

OCR for page 73
Avoiding Surprise in an Era of Global Technology Advances CHART 6-2 Technology Assessment: Bacteriorhodopsin for Holographic Messaging and Development of Advanced Holographic Technologies Technology Observables Bacteriorhodopsin for holographic messaging and development of advanced holographic technologies This technology is likely to come from advances in DVD (digital video disc) technology for movies. The most likely source would be the commercial sector (e.g., technology companies such as Apple Computer and Gentec). Web sites for light shows, rock bands, pseudomilitary companies, and special-effects houses should be monitored. Accessibility Maturity Consequence Level 2 Watch Threaten BLUE communications superiority. Noroviruses Particularly disabling pathogens are viruses in the Norovirus family. Noroviruses (also called Norwalk-like viruses) are spread through contaminated food or water; they cause acute vomiting, diarrhea, and fever. There are many viruses in this group, so multiple episodes of infection are common. Noroviruses are extremely contagious because of their low infectious dose (<100 viral particles), prolonged asymptomatic shedding (up to 2 weeks after recovery), ability to resist chlorination, and stability in the environment. Norovirus outbreaks are common in military deployments and were the most common cause of disability among soldiers in Operations Desert Storm and Desert Shield (McCarthy et al., 2000). A 2002 outbreak among British soldiers and hospital staff in Afghanistan resulted in closure of the field hospital. Eleven people with severe symptoms were evacuated to Germany and England, partly because of the inability to diagnose the disease (MMWR, 2002). Currently, this group of viruses cannot be cultured, so the ability of individuals to purposefully introduce infection through contamination of the food or water supply is limited (the only source of virus is stool of an infected person). However, this is an area of intense investigation, and the recent report of the culture of a mouse norovirus may lead the way to the culture of human noroviruses (Wobus et al., 2004). If cultured organisms were available, strains for which immunity is uncommon or does not exist could be chosen for introduction at strategic times and places. The DNA copy of the virus could then be used to produce specifically altered forms of the virus that could be designed to evade immunity, to have increased virulence, or to deliver genes encoding toxins or other virulence factors. (See Chart 6-3.) Avian Influenza Another pathogen of concern is the family of avian influenza viruses—both H5N1 and H7N2 have caused severe human illness. Influenza virus is spread by the respiratory route, so an introduction of infection into a military population might be more difficult than with a foodborne or waterborne virus. However, it could be introduced through infection of local animals such as pigs or chickens. Lack of immunity in the human population would ensure widespread disease. The major current barrier to the use of this virus to disable military populations is the lack of human-to-human transmission of current strains. (See Chart 6-4.)

OCR for page 73
Avoiding Surprise in an Era of Global Technology Advances CHART 6-3 Technology Assessment: Development and Distribution of Norovirus Organisms Technology Observables Development and distribution of norovirus organisms An indicator is evidence that a laboratory is conducting research aimed at producing a representative of this group of viruses in culture. This would include development of new lines of cells derived from the gastrointestinal tract. Development of mechanisms of stabilizing the virus and development of vaccines that could be used to protect the adversary would be an indicator of deployment. Accessibility Maturity Consequence Level 2/3 Warning Debilitation of BLUE forces. CHART 6-4 Technology Assessment: Development and Distribution of Avian Influenza Organisms Technology Observables Development and distribution of avian influenza organisms Indicators would include construction of high-containment laboratories for work with virulent strains, reports of laboratory-acquired infections, or increased use of primates in containment facilities. Development of vaccines to protect the adversary would be an important component of such a research program. Accessibility Maturity Consequence Level 2/3 Watch Debilitation of BLUE forces. Research that leads to an understanding of the biologic determinants of transmissibility by respiratory secretions will allow scientists to engineer current virus strains for efficient spread. The technology is already available and in use for genetically engineering influenza virus. Although many laboratories are working on influenza, relatively few are investigating the determinants of transmissibility. Initial work is likely to be with easily manipulated animal model systems (e.g., mice, ferrets) in which virologic determinants of transmission from one animal to another by the respiratory route can be identified using genetically engineered strains of virus. Synthesis of Decoys A release of infectious agents as weapons of mass destruction (WMDs) is a current major military concern. Several organisms have been developed as WMDs by one country or another. Sophisticated sensors based on the known antigenic composition and genetic or protein sequence of these organisms considered to be of highest risk are in current use, and advanced versions are under development. A release of compounds or agents that react with these detectors, but are not the actual agents, would be of

OCR for page 73
Avoiding Surprise in an Era of Global Technology Advances CHART 6-5 Technology Assessment: Development and Distribution of Organisms as Decoys Technology Observables Development and distribution of organisms as decoys One indicator would be evidence that an adversary had gained knowledge of the specific technology being used (e.g., stolen or missing data, devices, technical reports). Research on genetic manipulation of antigenic determinants or key signature sequences through recombinant technology would be relevant. Accessibility Maturity Consequence Level 3 (likely dedicated military laboratories) Unknown Spoofing of weapons of mass destruction sensors. no risk to the adversary, but it would precipitate time-consuming responses in U.S. troops. The responses could include preparing medical units, delaying operations while time- and energy-consuming confirmatory tests are performed, and causing military personnel to put on protective gear that might impair mobility, comfort, and function. Such mimics would create reticence to enter certain areas. Similar approaches are applicable to chemical agents. For decoys to be developed, the adversary would need to have knowledge of the methods and identifiers used by the sensors. For instance, mass spectrometry methods will identify signature peptides or protein or nucleic acid sequences, and immunologic detectors will identify specific protein antigens in the organism. (See Chart 6-5.) SUMMARY Biotechnology capabilities are rapidly expanding and becoming more and more readily available to scientists throughout the world. Emerging biotechnologies in functional brain imaging, communications, the spread of disabling infections, and sensor spoofing are likely to affect the conduct of military operations and the status of national security in the future. These biotechnologies have been highlighted in this chapter. The neuroimaging techniques of EEG, MEG, fMRI, and NIRS provide direct measurement of brain function. Technology underlying these modalities is advancing rapidly to allow a multitude of measurements. These technologies may provide a better understanding of behavior, performance, readiness, and stress that is relevant to understanding the cultural differences in motivation and prisoner interrogation. There are many opportunities on the horizon for biology to play a role in communications. These include protein cube holography and bacteriorhodopsin solid-state devices for storing high-density information, and DNA sequences as a medium for hiding covert messages. DNA is currently available, capable of storing and communicating large amounts of hidden information, in a compact and stable medium as DNA itself or in the signal-to-noise ratio of sequence data. Work on bacteriorhodopsin has been ongoing for a substantial period, and genetic manipulation of this remarkable molecule continues to open new opportunities for its use. One of these uses is holography, but there are also other technologies that are maturing for embedding messages in holograms. The technology for reading holograms is the current limiting factor in exercising this potential.

OCR for page 73
Avoiding Surprise in an Era of Global Technology Advances Infectious diseases are a continuing concern. They offer opportunities for a wide range of genetic modifications and could be deployed in many different ways but were not a primary focus of this report. However, the current emphasis on weapons of mass destruction has led to the development of sophisticated sensors that, when activated, trigger responses that can be costly in time and can limit troop responses. A release of materials that trigger sensors, but are not threats, is one way of decreasing battle readiness in U.S. troops. The area of application of biotechnology to military purposes is currently wide-ranging. It will expand very rapidly over the next decade. REFERENCES Hillebrecht, J.R., K.J. Wise, J.F. Koscielecki, and R.R. Birge. 2004. Directed evolution of bacteriorhodopsin for device applications. Methods in Enzymology 388:333-347. McCarthy, M., M.K. Estes, and K.C. Hyams. 2000. Norwalk-like virus infection in military forces: Epidemic potential, sporadic disease, and the future direction of prevention and control efforts. Journal of Infectious Diseases 181(SUPP/2): S387-S391. MMWR (Morbidity and Mortality Weekly Report). 2002. Outbreak of acute gastroenteritis associated with Norwalk-like viruses among British military personnel—Afghanistan, May 2002. June 7, Vol. 51, No. 22: pp. 477-479. Available online at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5122a1.htm. NRC (National Research Council). 2001. Opportunities in Biotechnology for Future Army Applications. National Academy Press, Washington, D.C. Shen, Y., C.R. Safinya, and K.S. Liang. 1993. Stabilization of the membrane protein bacteriorhodopsin to 140 degree C in two-dimensional films. Nature 366(6450):48. Wise, K.J., N.B. Gillespie, J.A. Stuart, M.P. Krebs, and R.R. Birge. 2002. Optimization of bacteriorhodopsin for bioelectronic devices. Trends in Biotechnology 20(9):387-394. Wobus, C.E., S.M. Karst, L.B. Thackray, K-O. Chang, S.V. Sosnovtsev, G. Belliot, A. Krug, J.M. Mackenzie, K.Y. Green, and H.W. Virgin IV. 2004. Replication of norovirus in cell culture reveals a tropism for dendritic cells and macrophages. Public Library of Science Biology 2(12):e432.