Promising new assays and technologies for the diagnosis and management of infectious diseases

Abstract

In the first decade of the 21st century, we have seen the completion of the human genome project and marked progress in the human microbiome project. The vast amount of data generated from these efforts combined with advances in molecular and biomedical technologies have led to the development of a multitude of assays and technologies that may be useful in the diagnosis and management of infectious diseases. Here, we identify several new assays and technologies that have recently come into clinical use or have potential for clinical use in the near future. The scope of this review is broad and includes topics such as the serum marker procalcitonin, gene expression profiling, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and nucleic acid aptamers. Principles that underlie each assay or technology, their clinical applications, and potential strengths and limitations are addressed.

Figure 1.

Schematic diagram of a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry instrument. The specimen is irradiated with a laser and converted into an ionic gas in the ionization chamber. Positively charged particles are accelerated in an electric field and then traverse the time-of-flight mass analyzer before colliding with a particle detector. The mass spectrogram is calculated from the measured flight times.

Figure 2.

In systematic evolution of ligands by exponential enrichment (SELEX), a large pool of random oligonucleotides is incubated with a target molecule. Upon binding, the short nucleic acid sequence folds into a 3-dimensional structure that binds to its target. Bound nucleic acids are then eluted and amplified by polymerase chain reaction. This cycle is repeated until oligonucleotides with suitably high specificity and binding affinity are isolated [47]. Through this process aptamers with low picomolar to nanomolar dissociation constants (K_d) can be obtained [48]. The SELEX process involves 5 main steps: (1) incubation of a random pool of nucleic acids with a target molecule or cell; (2) separating bound nucleic acids from unbound nucleic acids; (3) eluting the bound nucleic acid from the target; (4) amplifying the eluted nucleic acids to generate a refined pool of nucleic acids; and (5) using amplicons as new nucleic acid pools in subsequent rounds of selection. This process is repeated until “aptamers” with high specificity and affinity for the target are isolated. Abbreviations: PCR, polymerase chain reaction; SELEX, systematic evolution of ligands by exponential enrichment.