Alex van Breda

Detection and quantitation of human cytomegalovirus DNA in faeces

The development and performance of a robust and sensitive PCR assay are described for the detection and quantitation of human cytomegalovirus DNA in human faecal specimens. In this assay, CMV DNA was purified by an optimised DNA extraction protocol together with internal control DNA that monitored both DNA extraction efficiency and PCR efficiency. The lower detection limit of the assay was reached at about 100 CMV particles per ml of (25-50%) faecal suspension. CMV DNA could be quantitated in the range of about 300-100000 molecules per ml of faecal suspension. CMV DNA loads obtained in clinical faeces specimens suggest that the assay can be used to monitor the efficacy of antiviral treatment. Reconstruction experiments that monitored the efficiency of DNA extraction of a preliminary DNA extraction protocol, showed low DNA yields for 9% of the specimens (n = 78). In all cases, low DNA extraction efficiency seemed to be due to a component present in faeces that prevented DNA binding to silica particles, presumably by competitive binding. Choosing the right ratio of silica particles to faeces specimen solved this problem. Similarly, reconstruction experiments showed that the strong PCR inhibition that was observed in 8% of the specimens could effectively be relieved by the inclusion of alpha-casein in the PCR mixtures.

Human cytomegalovirus DNA in plasma and serum specimens of renal transplant recipients is highly fragmented.

ABSTRACT Quantitation of cytomegalovirus (CMV) DNA in plasma and serum by PCR is increasingly used to identify patients at risk for developing CMV disease and to monitor the efficacy of antiviral therapy. Although CMV DNA levels are generally interpreted as viral loads, the exact nature of the viral DNA in these specimens is unknown. We studied the state of CMV DNA in plasma and serum specimens obtained from three renal transplant recipients at peak viral DNA levels during primary CMV infection. For this purpose, DNA isolated from these specimens was fractionated by size, and CMV DNA levels in the resulting DNA fractions were measured by quantitative PCR targeted at large (578-bp) and small (134-bp) amplicons. These experiments showed that the molecular sizes of DNA fragments from which CMV DNA is amplified were small (<2,000 bp), indicating that CMV DNA in plasma and serum is highly fragmented. Furthermore, CMV DNA levels were consistently higher when targeted at the smaller amplicon, providing additional evidence for the fragmentation of viral DNA. In conclusion, the first results with three patients have shown that CMV DNA in plasma and serum is highly fragmented and does not necessarily reflect the amount of infectious virus. These observations have potential consequences for understanding CMV pathogenesis and interpreting CMV DNA levels in individual patient management.

Reduced PCR Sensitivity Due to Impaired DNA Recovery with the MagNA Pure LC Total Nucleic Acid Isolation Kit

ABSTRACT The increasing demand for molecular diagnostics in clinical microbiology laboratories necessitates automated sample processing. In the present study, we evaluated the performance of the MagNA Pure LC total nucleic acid isolation kit (M extraction) in comparison with the manual method (Si extraction) according to Boom et al. (R. Boom, C. J. A. Sol, M. M. M. Salimans, C. L. Jansen, P. M. Wertheim-van Dillen, and J. van der Noordaa, J. Clin. Microbiol. 28:495-503, 1990) for the detection of viral DNA by competitive quantitative PCR. Reconstruction experiments with HindIII-digested phage lambda DNA and HaeIII-digested φX174 DNA showed that the recovery of DNA from phosphate-buffered saline, cerebrospinal fluid, EDTA-anticoagulated plasma, and EDTA-anticoagulated whole blood by M extraction is, on average, 6.6-fold lower compared to Si extraction. PCR signals of spiked PCR control DNAs for Epstein-Barr virus and varicella-zoster virus were also between 1.9- and 14.2-fold lower after M extraction compared to Si extraction, also suggesting impaired DNA recovery. M extraction of spiked cytomegalovirus strain AD 169 in whole blood showed a 5- to 10-fold reduction in PCR sensitivity compared to Si extraction. This reduction of PCR sensitivity was also observed when clinical whole blood samples were processed by M extraction. Before implementing M extraction, the clinical consequences of the reduced recovery should first be considered, especially when maximal sensitivity is required.

Epstein-Barr Virus Infects B and Non-B Lymphocytes in HIV-1–Infected Children and Adolescents

Epstein-Barr virus (EBV) is a widespread, persistent herpesvirus that can transform B cells and that is associated with malignant lymphomas. EBV dynamics and specific immunity in human immunodeficiency virus (HIV)-1-infected children are unknown. We found that, in 74% of EBV-seropositive, HIV-1-infected children, EBV DNA loads at the start of highly active antiretroviral therapy (HAART) were comparable with those in acutely EBV-infected, HIV-negative children. EBV DNA load remained elevated in most HIV-1-infected children for months to years of follow-up. Frequencies of interferon-gamma-producing EBV-specific CD8+ T cells were comparable with those in healthy control children, and antibodies to EBV nuclear antigen were detected in 73% of EBV-seropositive children. Detectable EBV DNA load was not correlated with HIV-1 RNA level or with CD4+ T cell count increase after the start of HAART. Because of its resemblance to chronic active EBV, we studied the cellular tropism of EBV in these patients. EBV DNA was found not only in the CD19+ B cell fraction but also--at stable levels--in the CD4+ and CD8+ T cell fractions. Although the reason for the aberrant T cell tropism of EBV remains unclear, these data may provide an explanation for the differential EBV dynamics in the presence of normal serological findings.

The nature of placental steroid sulphatase deficiency in man

Human placental steroid sulphatase was partially purified from microsome suspensions of control and steroid sulphatase deficient placentae. After polyacrylamidegel electrophoresis, staining for protein and enzymatic activity revealed that steroid sulphatase from control placenta migrates at Rf = 0.44. In steroid sulphatase deficient microsomes no protein band and only a very faint sulphatase activity band could be detected at Rf = 0.44. Immunoelectrophoresis employing antisera raised against both steroid sulphatase preparations, only gave a protein precipitation line with sulphatase activity when using control placenta microsomes and the antiserum against steroid sulphatase from control placenta. All other placental microsomes-antisera combinations appeared to be negative. Our results strongly suggest that the nature of X-linked steroid sulphatase deficiency is a decreased amount of steroid sulphatase protein.