pp65 test

The pp65 test is a virological method used in cytomegalovirus diagnostics. In the pp65 test, immunofluorescence staining detects the human cytomegalovirus (HCMV) specific antigen pp65 (pp for phosphoprotein , molecular weight 65  kDa ) in lymphocytes isolated from whole blood . The pp65 antigen is only present in cells that change from the dormant form ( latency ) to an active replication of the HCMV, since as an activating control protein of the HCMV it initiates the transition from the resting phase to the replication phase.

The importance of the pp65 test lies in the detection of an actual multiplication of the virus. The detection of IgG antibodies would only detect an old, now persistent infection (detectable in about 60% of all people), IgM antibodies against HCMV are detectable in a fresh infection and also in a reactivation of an old infection that has existed for years. The detection of HCMV DNA by means of PCR in whole blood also detects all latent, dormant viruses. In patients under immunosuppression (after organ transplantation or under chemotherapy ), a recurring multiplication of the virus can lead to life-threatening diseases. Therefore, the pp65 test was necessary regularly in these patients in order to prevent this in good time by administering medication (e.g. ganciclovir ).

The test can hardly be used in routine diagnostics because it requires a very complex preparation of the lymphocytes from the blood (so-called buffy coat ), staining with anti-pp65 antibodies and an assessment using fluorescence microscopy . The results of the pp65 test are subject to a wide range of variation and are hardly comparable between different laboratories. A high rate of false positives and up to 18% false negatives is known. Determining the pp65 antigen alone no longer meets today's standards. A quantitative virus detection in the blood serum or blood plasma (records the viruses actually freely circulating) is sufficient in most cases for the clinical requirements. The quantification of HCMV in serum or plasma is often superior to the pp65 test for the kinetic assessment of the course and for the early detection of reactivation, since the pp65 test cannot be used in many patients due to the low lymphocyte count. However, the correlation between clinical symptoms and detection of the pp65 antigen seems to be more possible, probably also because of its lower sensitivity. A quantitative detection of pp66 mRNA in lymphocytes by means of PCR is also possible, but is only rarely used. This detection of the mRNA of the regulatory protein pp66 corresponds in the assessment to the detection of the pp65 antigen, but is easier to standardize.

Although the sole pp65 test no longer meets the more modern virological requirements for the detection of HCMV reactivation, it is still recommended by transplant medical and oncological societies.

swell

1. ↑ S. Gouarin, A. Vabret, C. Scieux et al .: Multicentric evaluation of a new commercial cytomegalovirus real-time PCR quantitation assay. In: J Virol Methods. 146 (1-2), Dec 2007, pp. 147-154. PMID 17673304
2. ↑ G. Gentile, A. Picardi, A. Capobianchi et al .: A prospective study comparing quantitative cytomegalovirus (CMV) polymerase chain reaction in plasma and pp65 antigenemia assay in monitoring patients after allogeneic stem cell transplantation. In: BMC Infect Dis. 6, Nov 21, 2006, p. 167. PMID 17118205
3. ↑ L. Mhiri, B. Kaabi et al .: Comparison of pp65 antigenemia, quantitative PCR and DNA hybrid capture for detection of cytomegalovirus in transplant recipients and AIDS patients. In: J Virol Methods. 143 (1), Jul 2007, pp. 23-28. PMID 17336402
4. ↑ L. von Muller, J. Hinz et al: CMV monitoring using blood cells and plasma: a comparison of apples with oranges? In: Bone Marrow Transplant . 39 (6), Mar 2007, pp. 353-357. PMID 17277789

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !