Real-time fluorescent quantitative PCR assay for measuring cytomegalovirus DNA load in patients after haematopoietic stem cell transplantation:

Correlation between systemic lupus erythematosus and cytomegalovirus infection detected by different methods

Human cytomegalovirus (HCMV), a β-herpes virus subfamily member, leads to a lifelong, latent infection in most humans, but the correlation between HCMV infection and systemic lupus erythematosus (SLE) remains controversial. We analyzed the relevance of HCMV infection in SLE by analyzing the peripheral blood leukocytes (PBLs) and serum samples of 60 patients with SLE and 111 healthy individuals. HCMV genes UL55 and UL138 were detected in PBLs by polymerase chain reaction (PCR), and HCMV-specific serum IgG and IgM antibodies were investigated by enzyme-linked immunosorbent assay. The relationship between cellular HCMV infection in PBLs and common clinical indicators of SLE was further explored. Data indicated that the frequency of positive IgG and IgM anti-CMV antibodies was not significantly different in SLE patients and controls. However, compared to the healthy controls, the titers of IgG and IgM anti-CMV antibodies in SLE patients were significantly higher. The detection of cellular HCMV infection showed that almost all subjects were positive for UL138 gene in PBLs, but the positivity for UL55 gene was lower in PBLs. HCMV UL138 detection in PBLs was highly consistent with the frequency of the HCMV-specific IgG test and did not show significant difference in SLE patients and healthy controls. However, compared with that in healthy people, the positivity rate for cellular HCMV UL55 detection was significantly higher in SLE patients (P < 0.001). In addition, cellular HCMV UL55 with positive detection in PBLs was associated with significantly different clinical characteristics of SLE than that with negative detection. In conclusion, our data confirmed that the HCMV infection was related to the development of SLE. Especially, some clinical strains or substrains of HCMV, such as containing the UL55 gene in HCMV's genome, might play a vital role in the development of SLE.

Human cytomegalovirus detection by real-time PCR and pp65-antigen test in hematopoietic stem cell transplant recipients: a challenge in low and middle-income countries

AIM

Cytomegalovirus (CMV) infection is one of the most common complications in patients submitted to hematopoietic stem cell transplant (HSCT). Pre-emptive therapy has been indicated in patients with laboratory evidence of CMV replication. The aims of this study were to compare real-time PCR or pp65 antigen assay methodologies to detect CMV replication in HSCT patients, define a viral load threshold for initiation of pre-emptive therapy, and assess the feasibility of its implementation in hospitals of countries with low and middle income.

MATERIAL AND METHODS

Human CMV detection by real-time PCR and pp65 antigen assay was carried out in blood and plasma samples of HSCT patients collected weekly during 3 months. Pre-emptive therapy was based on CMV antigenemia results.

RESULTS

Twenty-one patients were monitored with a total of 227 samples collected; 13 (62%) patients were children. A poor correlation was observed between qualitative results, though quantitative results showed statistically significant difference, with higher viral loads detected in patients with positive antigenemia. Compared to a positive antigenemia, a cutoff value of 1067·5 copies/ml, 3·03 log10/ml, for viral load was obtained with 100% sensitivity and 71% specificity.

CONCLUSION

CMV real-time PCR in whole blood was suitable for monitoring HSCT patients. However, its high cost is a limiting factor, and it could be used to monitor selected patients, those with prolonged leukopenia and underweight children, and subsequently switched to pp65 antigen test. Further studies involving larger numbers of patients should be performed to confirm this statement.

Quantification of cytomegalovirus glycoprotein Bn DNA in hematopoietic stem cell transplant recipients by real-time PCR

Based on sequence variation in the N-terminus of the UL55 gene, which encodes glycoprotein B (gB), human cytomegalovirus (CMV) can be classified into four gBn genotypes. We assessed the distribution of CMV gBn genotypes and the correlation between CMV gBn DNA (detected by real-time PCR) and CMV-positive pp65 cells (identified by immunohistochemical staining) in a cohort of hematopoietic stem cell transplant patients. The distribution of gB genotypes was as follows: gBn1, 60% of patients; gBn2, 13.3%; mixed gBn1 and gBn3 infection, 26.7%; and gBn4 and other mixed infections, 0%. CMV gBn1 was the most common genotype. The detected level of CMV gB DNA correlated well with the number of CMV-positive pp65 cells detected by immunostaining (r = 0.585).

Monitoring of human cytomegalovirus infection in bone marrow and liver transplant recipients by antigenaemia assay and enzyme-linked immunosorbent assay

Human cytomegalovirus (HCMV) infection is a common complication in transplant recipients. Sensitive, specific and timely diagnostic tests for the detection of HCMV infection remain essential for successful therapy. The results of three tests to detect HCMV in bone marrow and liver transplant recipients were compared: a pp65 antigenaemia assay, an immediate-early (IE) antigenaemia assay and an anti-HCMV immunoglobulin M (IgM) antibody enzyme-linked immunosorbent assay (ELISA). Of 1344 samples, 911 (67.8%) and 917 (68.2%) samples were positive for pp65 and IE, respectively. The coincidence level was 85.1%. There was no statistical difference after transplantation to the first positive detection of HCMV (mean first checkout time) between the pp65 and IE antigenaemia assays. Moreover, the levels of HCMV detected by the pp65 and IE antigenaemia assays were significantly correlated. The HCMV-positivity rate as detected by the anti-HCMV IgM ELISA was 11.1%, which was significantly different from the IE and pp65 antigenaemia assays. We suggest that the IE antigenaemia assay could replace the pp65 antigenaemia assay for monitoring active HCMV infection and early detection of HCMV infection.

[Evaluation of Biosewoom Real-Q Cytomegalovirus Quantification kit for Cytomegalovirus viral load measure]

BACKGROUND

Rapid and accurate laboratory tests are essential to detect cytomegalovirus (CMV) infections in solid organs and haematopoietic stem cell transplant recipients. We assessed the realtime quantitative PCR (RQ-PCR) technology for its usefulness in detecting CMV DNA.

METHODS

We evaluated the analytical performance of CMV RQ-PCR using Real-Q Cytomegalovirus Quantification kit (BioSewoom Inc., Korea). To evaluate its clinical utility, we also compared it to pp65 antigenemia test, an immunostaining method, on 343 samples of total 84 patients, including 63 transplant recipients.

RESULTS

The detection limit of RQ-PCR was 63 copies/mL and none of hepatitis B virus, hepatitis C virus, or human immunodeficiency virus showed a cross-reactivity with CMV. Total coefficient of variation (CV) was 10.4-19.5%. It detected CMV DNA in a linear range from 1 x 10(2) to 5 x 10(11) copies/mL (P<10(-13), R(2)=0.9994). The qualitative positive rates of pp65 antigenemia test and RQ-PCR were 4.7%, 16.3%, respectively and concordance rate between the two tests was 84.8% (Kappa=0.221, P<10(-6)). In comparison of quantitative results, the correlation between two tests was significant (r=0.45, P<10(-17)). In comparison among three groups by pp65 antigen level, CMV DNA level obtained with RQ-PCR increased significantly (P<10(-3) and P<10(-7), respectively).

CONCLUSIONS

The RQ-PCR is easier to perform than the immunostaining method, has good analytical performance and reflects the blood level of viral DNA well. It may be a new method substituting the pp65 antigenemia test. Further studies determining RQ-PCR value starting pre-emptive therapy will be required.