A novel, internally competitive polymerase chain reaction for quantification of human cytomegalovirus DNA in human leukocytes

The rapid, low cost estimation of Human Cytomegalovirus (HCMV) viral load in the blood of immunosupressed individuals is crucial for the timely diagnosis of transplant recipients with clinically significant HCMV infections requiring treatment. To this end we have developed a novel polymerase chain reaction (PCR) assay with internal controls for competitive quantification of cytomegalovirus DNA in human leukocytes. The reaction simultaneously amplifies, under reduced stringency conditions, a 136 bp fragment of the HCMV LA gene together with a single anonymous 200 bp fragment of human DNA using a single-primer pair. The primers used are specific for the HCMV gene sequence but contain a single mismatch that permits the amplification of the competing human DNA fragment. Quantification is achieved by comparison of the amount of the two products. The assay quantifies between 10(3)and 10(6)HCMV genomes in 10(6)leukocytes, a range that permits low-level clinically unimportant HCMV infections to be distinguished from those likely to cause serious disease. The advantages of the method are that no external controls are needed, quantification is achieved from a single reaction and no separate measurement of host DNA concentration is required.

Highly sensitive single-step PCR protocol for diagnosis and monitoring of human cytomegalovirus infection in renal transplant recipients

A multiplex, single-step PCR protocol for the detection of human cytomegalovirus (HCMV) DNA is described. The protocol amplifies regions of the viral LA and IE genes and employs elevated temperatures for both reagent mixing and primer annealing together with product detection by silver staining on polyacrylamide gels. This assay detects one to five HCMV genomes in clinical samples containing up to 100 ng of human DNA, a level of sensitivity equivalent to that of more complex assays involving either nested PCR or postamplification hybridization. As well as being of importance in clinical situations where high-sensitivity qualitative diagnosis is required, this assay is also applicable to the monitoring of HCMV infection in renal transplant recipients. Due to its multiplex format the assay provides quantitative information, in that samples from which a single target is amplified contain on average sevenfold fewer viral genomes per 10(6) leukocytes than those from which both targets are amplified. When weekly blood leukocyte DNA preparations from renal transplant patients were assayed, findings of three consecutive tests in which both HCMV targets were amplified were highly indicative of patients who had developed very high loads of HCMV (100% sensitivity, 88% specificity). We thus show that the same simple PCR assay which permits highly sensitive HCMV diagnosis can also be used for the efficient identification of transplant recipients at risk of clinically significant infection.

Randomly amplified polymorphic DNA (RAPD) and isoenzyme analysis of Trypanosoma rangeli strains

Sixteen Trypanosoma rangeli strains were compared by isoenzyme and randomly amplified polymorphic DNA (RAPD) analysis. Eight strains were isolated from either Rhodnius prolixus or Homo sapiens from Honduras, Colombia and Venezuela. Another eight strains were isolated from either Panstrongylus megistus or the rodent Echimys dasythrix from the State of Santa Catarina, southern Brazil. All six T. rangeli strains isolated from P. megistus were co-infections with Trypanosoma cruzi, demonstrating an overlap of the sylvatic cycles of these parasites and that the accurate identification of species is of utmost importance. Both isoenzyme and RAPD analysis revealed two distinct groups of T. rangeli strains, one formed by the strains from Santa Catarina and the other, by the strains from Honduras, Colombia and Venezuela. With the five enzymes used, all the strains from Santa Catarina had identical profiles which overlapped with those of the other regions only in the pattern obtained with malic enzyme. Analysis of 138 RAPD bands by means of an unweighted pair group method analysis (UPGMA) phenogram using the Dice similarity coefficient allowed the separation of the two groups based on their divergence at a lower level of similarity than the phenon line. We show that the identification of T. cruzi and T. rangeli in naturally mixed infections is readily achieved by either RAPD or isoenzyme analysis.