Use of forensic methods under exigent circumstances without full validation

The use of host factors in microbial forensics

Advances have been made in the forensic analysis of microbes and toxins. An underdeveloped and underutilized area in microbial forensics is how the host interacts with microorganisms in a way that provides unique signatures for forensic use. For forensic purposes, an immediate goal is to distinguish a potential victim and innocent person from a perpetrator, and to distinguish between a naturally acquired or intentional infection. Principal methods that are sufficiently developed are characterization of the humoral immune response to microbial antigens including vaccine-induced immunity and detection of antibiotics that may be present in a possible perpetrator. This chapter presents central elements of the host response in a simplified fashion and describes a representative example, which, in the appropriate context, has a high potential of providing evidence that may aid an investigation to distinguish a perpetrator from a victim. This chapter also presents information about the immune system so that the interested reader can have a fuller understanding of the immune response in general.

Expansion of Microbial Forensics

Microbial forensics has been defined as the discipline of applying scientific methods to the analysis of evidence related to bioterrorism, biocrimes, hoaxes, or the accidental release of a biological agent or toxin for attribution purposes. Over the past 15 years, technology, particularly massively parallel sequencing, and bioinformatics advances now allow the characterization of microorganisms for a variety of human forensic applications, such as human identification, body fluid characterization, postmortem interval estimation, and biocrimes involving tracking of infectious agents. Thus, microbial forensics should be more broadly described as the discipline of applying scientific methods to the analysis of microbial evidence in criminal and civil cases for investigative purposes.

Validation of high throughput sequencing and microbial forensics applications

High throughput sequencing (HTS) generates large amounts of high quality sequence data for microbial genomics. The value of HTS for microbial forensics is the speed at which evidence can be collected and the power to characterize microbial-related evidence to solve biocrimes and bioterrorist events. As HTS technologies continue to improve, they provide increasingly powerful sets of tools to support the entire field of microbial forensics. Accurate, credible results allow analysis and interpretation, significantly influencing the course and/or focus of an investigation, and can impact the response of the government to an attack having individual, political, economic or military consequences. Interpretation of the results of microbial forensic analyses relies on understanding the performance and limitations of HTS methods, including analytical processes, assays and data interpretation. The utility of HTS must be defined carefully within established operating conditions and tolerances. Validation is essential in the development and implementation of microbial forensics methods used for formulating investigative leads attribution. HTS strategies vary, requiring guiding principles for HTS system validation. Three initial aspects of HTS, irrespective of chemistry, instrumentation or software are: 1) sample preparation, 2) sequencing, and 3) data analysis. Criteria that should be considered for HTS validation for microbial forensics are presented here. Validation should be defined in terms of specific application and the criteria described here comprise a foundation for investigators to establish, validate and implement HTS as a tool in microbial forensics, enhancing public safety and national security.

Designing an effective microbial forensics program for law enforcement and national security purposes

Forensic capabilities that provide lead information, and investigative, intelligence, prosecution and policy decision support can be invaluable for responding to and resolving bioterrorism events. Attributing biological attacks through scientific and other resources and processes is an important goal, for which science can be instrumental. Some even believe that having effective microbial forensics capabilities along with others can even deter adversaries from using biological weapons. For those nations that do not have such or wish to integrate or upgrade capabilities, thoughtful analysis and consideration of certain design principles will increase the likelihood that success will be attained.

Rapidly maturing field of proteomics: a gateway to studying diseases

The proteomics work reported by Smith et al. represents a giant step forward in characterizing the cerebrospinal fluid (CSF) proteome in mouse models of human diseases. Whereas prior studies were limited to analysis of CSF pools, Smith et al. (Proteomics 2014, 14, 1102-1106) base their conclusions on data derived from individual mice, thereby capturing a fuller range of the biological diversity present. These results underscore how far proteomics has come in the past few years, developing into a modern tool with the capacity to remove bottlenecks in the study of neuropsychiatric diseases. Past efforts with mass spectrometry (MS) have been hampered by limitations in access to CSF samples, and small volumes when available. These barriers have been overcome with newer MS platforms and advances in sample preparation. We are far closer than before to producing the production of clinically useful proteomic data for biomarker discovery and for deriving insights into pathogenesis that can lead to more effective treatments for many diseases.

Distinct cerebrospinal fluid proteomes differentiate post-treatment lyme disease from chronic fatigue syndrome

Background

Neurologic Post Treatment Lyme disease (nPTLS) and Chronic Fatigue (CFS) are syndromes of unknown etiology. They share features of fatigue and cognitive dysfunction, making it difficult to differentiate them. Unresolved is whether nPTLS is a subset of CFS.

Methods and Principal Findings

Pooled cerebrospinal fluid (CSF) samples from nPTLS patients, CFS patients, and healthy volunteers were comprehensively analyzed using high-resolution mass spectrometry (MS), coupled with immunoaffinity depletion methods to reduce protein-masking by abundant proteins. Individual patient and healthy control CSF samples were analyzed directly employing a MS-based label-free quantitative proteomics approach. We found that both groups, and individuals within the groups, could be distinguished from each other and normals based on their specific CSF proteins (p<0.01). CFS (n = 43) had 2,783 non-redundant proteins, nPTLS (n = 25) contained 2,768 proteins, and healthy normals had 2,630 proteins. Preliminary pathway analysis demonstrated that the data could be useful for hypothesis generation on the pathogenetic mechanisms underlying these two related syndromes.

Conclusions

nPTLS and CFS have distinguishing CSF protein complements. Each condition has a number of CSF proteins that can be useful in providing candidates for future validation studies and insights on the respective mechanisms of pathogenesis. Distinguishing nPTLS and CFS permits more focused study of each condition, and can lead to novel diagnostics and therapeutic interventions.

Keeping Track of Viruses

This chapter reviews methods of isolating, identifying, and tracking viruses with potential applications to microbial forensic investigations. Viruses are the most abundant biological entities on earth. These obligate parasites infect every form of life, from archaea and eubacteria to fungi, plants, and animals. Viruses play key roles in global ecology—they form a vast reservoir of genetic diversity, influence the composition and evolution of host populations, and affect the cycling of chemical compounds through the environment. Research has focused on the tiny fraction that causes disease in humans, domestic animals, and crops; sequencing surveys have suggested that the majority of viruses are completely unknown. The ability of viruses to jump species barriers, move between habitats, and circle the globe rapidly underscores the importance of continued vigilance for naturally emerging or deliberately engineered outbreaks. Viruses are extremely simple “life” forms without metabolic capacity, organelles, translational machinery, or autonomous replicative potential. Virus particles constitute a minimal set of components, primarily those required to deliver the genome to the target cell and initiate replication. Consequently, virus particles (or virions) are extremely small, most in the range of 20 to 200 nm in diameter. Virions are diverse not only in size but also in composition, morphology, and genome characteristics. Virus particles may be irregular in shape or possess a distinct symmetry, such as helical or icosahedral. Particles may be surrounded by a host-derived membrane, termed “enveloped,” or a tight protein shell, termed “nonenveloped.”

Accurate, rapid and high-throughput detection of strain-specific polymorphisms in Bacillus anthracis and Yersinia pestis by next-generation sequencing

Background

In the event of biocrimes or infectious disease outbreaks, high-resolution genetic characterization for identifying the agent and attributing it to a specific source can be crucial for an effective response. Until recently, in-depth genetic characterization required expensive and time-consuming Sanger sequencing of a few strains, followed by genotyping of a small number of marker loci in a panel of isolates at or by gel-based approaches such as pulsed field gel electrophoresis, which by necessity ignores most of the genome. Next-generation, massively parallel sequencing (MPS) technology (specifically the Applied Biosystems sequencing by oligonucleotide ligation and detection (SOLiD™) system) is a powerful investigative tool for rapid, cost-effective and parallel microbial whole-genome characterization.

Results

To demonstrate the utility of MPS for whole-genome typing of monomorphic pathogens, four Bacillus anthracis and four Yersinia pestis strains were sequenced in parallel. Reads were aligned to complete reference genomes, and genomic variations were identified. Resequencing of the B. anthracis Ames ancestor strain detected no false-positive single-nucleotide polymorphisms (SNPs), and mapping of reads to the Sterne strain correctly identified 98% of the 133 SNPs that are not clustered or associated with repeats. Three geographically distinct B. anthracis strains from the A branch lineage were found to have between 352 and 471 SNPs each, relative to the Ames genome, and one strain harbored a genomic amplification. Sequencing of four Y. pestis strains from the Orientalis lineage identified between 20 and 54 SNPs per strain relative to the CO92 genome, with the single Bolivian isolate having approximately twice as many SNPs as the three more closely related North American strains. Coverage plotting also revealed a common deletion in two strains and an amplification in the Bolivian strain that appear to be due to insertion element-mediated recombination events. Most private SNPs (that is, a, variant found in only one strain in this set) selected for validation by Sanger sequencing were confirmed, although rare false-positive SNPs were associated with variable nucleotide tandem repeats.

Conclusions

The high-throughput, multiplexing capability, and accuracy of this system make it suitable for rapid whole-genome typing of microbial pathogens during a forensic or epidemiological investigation. By interrogating nearly every base of the genome, rare polymorphisms can be reliably discovered, thus facilitating high-resolution strain tracking and strengthening forensic attribution.