Quantitation of cytomegalovirus DNA in lung tissue of bone marrow transplant recipients

Pulmonary involvement during cytomegalovirus infection in immunosuppressed patients

Although cytomegalovirus (CMV) pulmonary involvement after solid organ transplantation is infrequently seen nowadays, CMV pneumonitis is still a potential lethal complication. Introduction of the pp65 antigenemia assay enabled early and rapid diagnosis of CMV viremia in transplant patients prior to symptoms. Also, in asymptomatic patients with CMV viremia, a decreased pulmonary diffusion capacity could be demonstrated. In this review, we discuss clinical and subclinical pulmonary involvement of CMV infection in the immunocompromised host with an emphasis on transplant recipients. The clinical course, diagnosis, therapy, prophylaxis, and pathophysiology of CMV pneumonitis are discussed.

Flow cytometric analysis of cytomegalovirus-specific cell-mediated immunity in the congenital infection

Flow cytometric analysis of CD4(+) and CD8(+) T cells specific to human cytomegalovirus (CMV) was undertaken in seven patients with congenital CMV infection, six healthy infants who had acquired infection, and six CMV-seropositive adults. Intracellular cytokine assays showed that 0.03-2.23% of CD4(+) T cells in the healthy infants and adults produced interferon-gamma (IFN-gamma) in response to CMV antigens. In contrast, such CD4(+) T cells were almost undetectable in patients with congenital CMV infection who were younger than 2 years of age. Tetrameric major histocompatibility complex/peptide complex analysis demonstrated HLA*A2402-restricted phosphoprotein 65-specific CD8(+) T cells to be present in most healthy infants and adults tested, but almost absent in the patients. Interestingly, CMV-specific CD4(+) T-cell responses were observed in two patients with congenital infection beyond the age of 5 years. The present study points to impairment of CMV-specific cellular immunity in patients in single-cell levels with congenital CMV infection during the infant period and possible restoration in later childhood.

Quantitative analysis of cytomegalovirus load using a real-time PCR assay

A novel real-time PCR assay system was developed to quantify the cytomegalovirus (CMV) genome load. The real-time PCR assay could detect from 6 to over 10(6) copies of CMV-DNA with a wide linear range. The virus load of immunocompromised patients with symptomatic CMV infections was quantified and compared to that of asymptomatic ones. In symptomatic patients, all 17 peripheral blood leukocytes were positive for CMV DNA, and its mean value was 10(3.3) copies/10(6) cells. On the other hand, only 9 of 38 samples (24%) were positive in the asymptomatic patients, and its mean titer was lower (10(2.0) copies/10(6) cells) than that of the symptomatic group (P = 0.002). In plasma, the virus genome was detected in 13 out of 17 samples from symptomatic patients (76%), and its mean value was 10(4.0) copies/ml. In contrast, for the asymptomatic group, only one out of 36 samples were positive (3%). Finally, this system was used to monitor two patients with CMV infections serially. The CMV DNA copy number changed with their clinical symptoms and anti-CMV therapy, and virtually paralleled the result of the pp65 antigenemia assay in both cases. In one patient with the cord blood transplantation, however, the CMV DNA became positive faster than the antigenemia assay. These results indicate that this assay is sensitive and useful for estimating the CMV genome load not only in peripheral blood leukocytes but also in plasma. It can be very helpful for diagnosing CMV-related diseases and monitoring the virus load in patients with CMV infections.

Quantitation of cytomegalovirus: methodologic aspects and clinical applications

Cytomegalovirus (CMV) is an important pathogen in transplant recipients and human immunodeficiency virus (HIV)-infected individuals. Major progress has been made in developing quantitative detection methods for CMV in recent years. Due to their high sensitivity, these assays can detect CMV early, and quantitation may be useful in predicting the patient's risk for disease and in monitoring the effect of antiviral therapy. This review discusses methodological aspects of currently used quantitative assays for CMV (i.e., viral culture techniques, antigen detection assays, DNA detection assays including PCR, branched-DNA assay, and the DNA hybrid capture assay) and addresses the correlation of systemic and site-specific CMV load and CMV disease in different populations of immunosuppressed patients as well as the response to antiviral treatment. To date, direct antigen detection and molecular techniques have largely replaced traditional culture-based techniques for CMV quantitation. In general, a high systemic CMV load is correlated with CMV disease. This correlation is strong in the HIV-infected population and in solid-organ transplant recipients but less clear in allogeneic marrow transplant recipients. Measuring the viral load at specific anatomic sites may be an alternative way to assess disease activity in situations where the systemic viral load correlates poorly with disease activity. A reduction of the systemic CMV load also correlates with a response to antiviral treatment, but more research is needed to evaluate the role of viral load as a surrogate marker for drug resistance. Due to the widespread use of quantitative CMV detection techniques to direct and monitor antiviral treatment, there is a great need for an assessment of the reproducibility of test results and better standardization of the assays.

Detection of human cytomegalovirus DNA from allogeneic bone marrow transplant recipients with interstitial pneumonitis

Interstitial pneumonitis (IP) due to human cytomegalovirus (HCMV) infection can kill patients who receive allogeneic bone marrow transplants (BMT). However, making a definitive diagnosis of HCMV-associated IP is difficult, except in pathologically defined cases. The authors tried to detect HCMV DNA amplified by the polymerase chain reaction with nonradioactive Southern blot analysis from paraffin-embedded lung tissue. Human cytomegalovirus DNA was detected in all of ten BMT recipients with IP and all of three non-BMT recipients with histologically diagnosed HCMV IP. Clinical diagnoses indicated that three of ten allogeneic BMT recipients had HCMV IP, and they showed amplified HCMV DNA despite the lack of histologic viral inclusions. However, HCMV DNA was not detected in 11 immunosuppressed patients with non-HCMV pneumonitis who were included as controls. These observations indicate that the polymerase chain reaction and Southern blot analysis used with lung tissue is more sensitive than histologic examination, and that these tests may be applicable to transbronchial lung biopsy specimens for the early specific diagnosis of HCMV IP. Further analysis of allogeneic BMT recipients showed that four patients who died of HCMV IP fewer than 90 days after BMT had higher quantities of HCMV DNA, whereas six patients who died of HCMV IP more than 90 days after BMT showed lower quantities of HCMV DNA. THis result suggests that HCMV IP in the late phase after MBT might not be attributable to active virus replication alone but rather to the immune response involved in the graft-versus-host reaction.

Quantitation of human cytomegalovirus genomes in the brain of AIDS patients

Human cytomegalovirus (HCMV) is one of the major pathogens causing neurologic disease in the immunocompromised host. A competitive nested polymerase chain reaction (PCR) was used to determine DNA load, distribution, and sequence variability of HCMV genomes in the brain of AIDS patients with and without HCMV encephalitis confirmed by histology and immunocytochemistry. By quantitative PCR, HCMV genomes were found to be distributed diffusely in the central nervous system (CNS) of all five patients with histologically proven HCMV encephalitis, but also in the brain of five of eight AIDS patients without neuropathological evidence of HCMV encephalitis. The viral DNA load in cases with HCMV encephalitis was increased 10- to 1,000-fold as compared to patients without evidence of encephalitis. A viral load above 6,000 copies HCMV/10(6) copies beta-globin was found to be highly suggestive for HCMV encephalitis. Characterization of PCR products by temperature gradient gel electrophoresis (TGGE) and direct sequencing allowed us to detect a sequence variability of the amplified fragment of HCMV glycoprotein B (gB) among different patients, but also among different HCMV foci within the same patient. Furthermore, two of five AIDS patients with HCMV encephalitis most likely experienced double infections with different HCMV strains. The experimental procedure described in this study should also be applicable to the detection of significant HCMV DNA levels in biopsy samples.

Polymerase chain reaction for the early diagnosis of cytomegalovirus hepatitis in liver transplant patients

BACKGROUND

In liver transplant (LTX) patients, cytomegalovirus (CMV) hepatitis as a cause of graft dysfunction occurs in 15-25% of the patients. Polymerase chain reaction (PCR), applied to liver biopsy specimens, may increase the ability to detect CMV DNA at a local site. In this study, PCR was used to compare its relation to the development of clinical CMV hepatitis.

STUDY DESIGN

Nested polymerase chain reaction (nPCR), derived from a conserved region of the CMV major immediate-early gene, was used to examine 141 frozen liver biopsies from 61 LTX patients for the presence of CMV DNA. 134 biopsies were obtained from 54 patients with pathological liver function tests within four months after transplantation. The remaining seven patient biopsies were derived from the one-year investigation after LTX and served as controls. The results were compared to virus isolation, antigen detection by immunohistology and in situ hybridization for CMV DNA of the biopsy specimens. Histological examination was performed to verify a diagnosis of viral hepatitis.

RESULTS

CMV DNA was amplified in 11% (15/134) of the biopsies, corresponding to 20% (11/54) of the patients. Virus isolation revealed CMV in 5% (7/134) of the samples. None of the nPCR-negative biopsies was virus culture positive. CMV genomes were detected by nPCR more frequently than CMV hepatitis was diagnosed by using the combination of CMV-specific histopathology and/or immunohistology and/or CMV-positive virus isolation (p < 0.01). However, when this comparison was performed within individual patients, the difference was not significant (p > 0.05). If the results of in situ hybridization were included in the diagnostic criteria of CMV hepatitis, the nPCR was comparable to these, both at the biopsy and the patient levels (p > 0.1 and p > 0.05, respectively). For the diagnosis of CMV hepatitis the negative predictive value of CMV-nPCR was 1.0. The positive predictive value ranged from 0.55 to 0.82 depending on the criteria of CMV hepatitis. The nPCR also detected signs of CMV infection in the liver graft earlier than virus isolation, 11 versus 21 days, respectively, after transplantation.

CONCLUSION

The frequency of CMV DNA positivity, measured by nPCR, was similar to that revealed by other combined methods. We suggest that the combined findings of histological cholangitis and/or lobulitis together with nPCR for CMV DNA can be used as a diagnostic criterion for initiation of antiviral treatment against CMV hepatitis.

Detection and quantification of virus DNA in plasma of patients with Epstein-Barr virus-associated diseases

Epstein-Barr virus (EBV) causes various diseases, such as infectious mononucleosis (IM), fatal IM, EBV-associated hemophagocytic syndrome (EBVAHS), and chronic active EBV infection (CAEBV). In the present study, cell-free EBV DNA was detected in the plasma of patients with EBV-associated diseases by PCR assay. The patients included 20 patients with IM, 2 patients with fatal IM, 4 patients with EBVAHS, 4 patients with CAEBV, and 38 healthy children (20 EBV seropositive and 18 EBV seronegative). In patients with IM, plasma samples were positive for EBV DNA in all patients (100%) in the acute phase and in 44% of the patients in the convalescent phase, but plasma samples from the 38 healthy control children were negative (0%) for EBV DNA. Quantitative PCR assay revealed that plasma from patients with IM contained the highest amount of virus DNA within 7 days following the onset of disease (mean, 6 x 10(4) copies per ml). The EBV DNA concentration decreased thereafter as the patients recovered. Plasma from patients with fatal IM contained more than 100 times more copies of EBV DNA (3 x 10(7) copies per ml) than plasma from patients with IM. Plasma from patients with the acute phase of EBVAHS contained 10 times more copies of EBV DNA (5 x 10(5) copies per ml) than plasma from IM, and then patients with the number of copies decreased similarly in both groups of patients in the convalescent phase (2 x 10(4) copies per ml). The amount of virus DNA in patients with CAEBV (6 x 10(4) copies per ml) was similar to that noted in patients with IM; however, it became higher (1 x 10(6) copies per ml) when the patients' clinical status deteriorated. These data suggest that the presence of cell-free EBV DNA in plasma is a common phenomenon in patients with EBV-associated diseases. The concentration of EBV DNA in plasma seems to be higher in patients with the more severe clinical categories of EBV diseases.

Monitoring of renal allograft recipients by quantitation of human cytomegalovirus genomes in peripheral blood leukocytes

The ratio of human cytomegalovirus (HCMV) genomes per cellular genomes in serial peripheral blood leukocyte (PBL) extracts of renal allograft recipients was quantitated by competitive nested polymerase chain reaction (PCR). Patients were also monitored for the development of acute HCMV infection by detection of HCMV pp65 antigenemia, HCMV IgM antibodies, and viruria. Compared to qualitative nested HCMV PCR, the frequency of positive PCR results in renal allograft recipients without further evidence of acute HCMV infection was significantly reduced by quantitative HCMV PCR. HCMV DNA levels > or = 1,000 copies HCMV/10(6) copies beta-globin were found to be highly indicative for the development of a clinically symptomatic HCMV infection following renal allograft transplantation. In patients treated with ganciclovir, quantitation of HCMV target sequences allowed the assessment of the efficacy of antiviral therapy.

Quantitative analysis in molecular diagnostics

Quantitative analysis of DNA products derived from polymerase chain reaction (PCR)-based assays depends on the careful optimization of each of the reaction parameters to achieve highly efficient amplification of target sequences. In practice, however, measurement of the accumulated PCR product is reliable only when analyses are performed at points in the exponential phase of the PCR amplification curve and before the onset of the plateau phase. The recent development of more sensitive DNA product detection systems has permitted the analysis of PCR assays after fewer amplification cycles, where the accumulation of product approaches linearity, while at the same time maintaining superior assay specificity. These methods include the use of high performance liquid chromatography, automated fluorescence detection, electrochemiluminescence, and the ligase chain reaction. Clinical applications of these methods are numerous and include diagnostic testing as well as therapeutic monitoring for neoplastic, infectious, and inherited genetic disease.

T-cell receptor V alpha region usage in the cerebrospinal fluid of patients with mumps meningitis

To investigate clonality of local T cells in viral infections of the central nervous system, the T-cell receptor (TCR) repertoire was evaluated in T cells from the cerebrospinal fluid (CSF) of nine patients with mumps meningitis, using the polymerase chain reaction (PCR) assay. The usage of the variable region of TCR alpha chain gene (V alpha gene) in the CSF was widespread, and an average of 13 out of the 18 V alpha families were expressed. Quantitative PCR analyses showed that the V alpha gene expression was biased toward three or less V alpha families in the CSF of each patient. When compared with peripheral blood T cells, the average percentages of V alpha 11 and V alpha 12 gene expression were significantly higher in the CSF than in the peripheral blood. These results suggested that mumps-specific T lymphocytes with a restricted TCR repertoire are selectively recruited to the central nervous system in mumps meningitis, although polyclonal, probably nonspecific, T-cell populations are present in the CSF.

Quantitative analysis of herpes simplex virus DNA in cerebrospinal fluid of children with herpes simplex encephalitis

Herpes simplex virus (HSV) DNA in the cerebrospinal fluid (CSF) of children with herpes simplex encephalitis (HSE) was quantified and typed using the polymerase chain reaction (PCR) assay. During the acute phase, HSV-DNA was detected in the CSF of 13 patients with HSE, including 5 neonates. A restriction profile of the PCR products cleaved with the restriction enzymes XhoI and BglII showed that 2 neonatal samples were HSV-2, and the remainder were HSV-1. The amount of HSV-DNA in the initial CSF ranged from 10(2)-10(5) copies/ml. A significantly greater number of HSV-DNA copies was detected in neonates than in older children (mean 3.9 vs. 2.5, log 10 copies/ml p < .05). Except for one patient, the amount of HSV-DNA decreased gradually with acyclovir therapy. These results show that a quantitative PCR assay is applicable not only to the diagnosis of HSE but also for monitoring the response to antiviral drugs.