The Detection of Latent Virus Infection by Polymerase Chain Reaction

Many standard techniques involving electron microscopy, tissue culture, and protein (antigen) analysis have been developed (reviewed in 1 ) for virus diagnosis and typing. Since most viral infections can be assigned to a particular virus type by these means, it is now increasingly important to identify pathogenic variants of each type by more sensitive, discriminating techniques. The main drawbacks of the traditional methods are: the time involved to achieve results; the requirement to find a convalescent patient from a particular infection to provide immune serum, and in many cases, the sheer bulk of infected material that had to be extracted for macromolecular analysis. The advent of nucleic acid based techniques showed much promise, in that the genomes of some viruses could be analyzed to produce what appeared to be an unambiguous “fingerprint,” based on restriction endonuclease cleavage patterns of the viral DNA (2 ). However, these techniques were again limited by tissue culture techniques for the virus, the time required to produce a result, and the expense involved in analysis of single samples. In addition, the techniques were limited in resolution to the number of restriction enzyme cleavage sites that could be assayed at one time. The ultimate fingerprint of any virus would be determination of its complete nucleotide base sequence. This has now been achieved for many viruses, but is a long-term, high cost strategy that could never be implemented in the routine laboratory.