Molecular and serological findings in suspected patients with Crimean-Congo hemorrhagic fever virus in Iran

Crimean-Congo hemorrhagic fever (CCHF) is an arthropod-borne disease of humans associated with a severe clinical picture, including hemorrhagic syndrome and a high mortality rate. CCHF virus is widely distributed throughout large areas of the world. To characterize the serological status in CCHF patients, paired clinical samples were collected from suspected CCHF patients and analyzed by microbiological and other laboratory analyses with the aim of: determining the presence of neutralizing antibodies against CCHF virus; investigating the cross-reactivity of these neutralizing antibodies against virus isolated from the same outbreak and against other available laboratory strain; and studying the relationship between the isolated virus with other virus by whole genome sequencing. Patients at Boo-Ali Hospital, Zahedan, Iran, with clinical symptoms ranging from mild to severe hemorrhagic fever were included in the study. Two serum samples were taken from each patient, the first as soon as the patient matched the criteria for CCHF notification and the second when the patient was discharged from hospital (2 weeks later). Commercial and in-house assays revealed a positive IgM signal in acute serum samples from six patients. A novel finding was that CCHF patients develop neutralizing antibodies soon after infection. Interestingly these antibodies were able to neutralize other CCHF virus strains too. The complete sequence of the Zahedan 2007 isolate, including the hitherto unknown first L-segment sequence, was identified using an original clinical sample from one patient with confirmed CCHF infection.

Crimean-Congo hemorrhagic fever virus, Greece

Seroprevalence of Crimean-Congo hemorrhagic fever virus (CCHFV) is high in some regions of Greece, but only 1 case of disease has been reported. We used 4 methods to test 118 serum samples that were positive for CCHFV IgG by commercial ELISA and confirmed the positive results. A nonpathogenic or low-pathogenicity strain may be circulating.

Healthy individuals' immune response to the Bulgarian Crimean-Congo hemorrhagic fever virus vaccine

Crimean-Congo hemorrhagic fever virus (CCHFV) poses a great threat to public health due to its high mortality and transmission rate and wide geographical distribution. There is currently no specific antiviral therapy for CCHF. This study provides the first in-depth analysis of the cellular and humoral immune response in healthy individuals following injection of inactivated Bulgarian vaccine, the only CCHFV vaccine available at present. Vaccinated individuals developed robust, anti-CCHFV-specific T-cell activity as measured by IFN-γ ELISpot assay. The frequency of IFN-γ secreting T-cells was 10-fold higher in individuals after vaccination with four doses than after one single dose. High levels of CCHFV antibodies were observed following the first dose, but repeated doses were required to achieve antibodies with neutralizing activity against CCHFV. However, the neutralizing activity in these groups was low.

Effects of Angipars on oxidative inflammatory indices in a murine model of periodontitis

BACKGROUND AND THE PURPOSE OF THE STUDY

There are strong evidences linking overproduction of reactive oxygen species and periodontal diseases. The aim of this study was to evaluate efficacy of Angipars a natural potent anti oxidative agent on markers of the oxidative damages and periodontal inflammation in the rat.

METHODS

Periodontitis was induced by single injection of lipopolysaccharide (LPS) from E. coli (10 µg/µl saline) into rat mandibular gingiva. After 10 days, animals in the test group received Angipars (2.1 mg/kg) by gavage once a day and those of control group received same amount of vehicle. The amount of interleukin (IL)-1β, lipid peroxidation (LPO), and 8-hydroxydeoxyguanosine (8-OHdG) were measured in gingival biopsy samples and the degree of apical migration of junctional epithelium (JE), alveolar bone resorption, and the number of polymorphonuclears (PMN) were evaluated by histological analysis of block samples of the left mandibular first molars.

RESULTS

Periodontitis group showed a significant increase in periodontal IL-1β, LPO, 8-OHdG, apical migration of JE, alveolar bone resorption and number of PMNs. Angipars treatment resulted in a significant decrease in gingival IL-1β, LPO, 8-OHdG and the apical migration of JE; however, the reduction of alveolar bone resorption was not significant. The number of PMN increased significantly after treatment with Angipars. While intake of vehicle resulted in a significant decrease in gingival IL-1β and LPO, the reduction of 8-OHdG, apical migration of JE, and alveolar bone resorption were not significant. Interestingly, PMNs were increased in groups received Angipars or the vehicle.

CONCLUSION

From the results of this study, it seems that Angipars is beneficial in periodontitis by reduction of inflammatory and oxidative damage. Unexpected increase of PMN count by Angipars strengthens the hypothesis that chronic inflammatory disorders like periodontitis may need more time to get best advantage of anti oxidative drugs like Angipars. Regarding role of microbes in pathogenesis of periodontitis, further studies should be focused on antimicrobial effects of Angipars.

Crimean-Congo hemorrhagic fever virus delays activation of the innate immune response

As a first line of defence against virus infection, mammalian cells elicit an innate immune response, characterized by secretion of type I interferons and the up-regulation of interferon stimulated genes. Many viruses down-regulate the innate immune responses in order to enhance their virulence. Crimean-Congo hemorrhagic fever virus (CCHFV), a Nairovirus of the family Bunyaviridae is the causative agent of severe hemorrhagic fever in humans with high mortality. Knowledge regarding the innate immune response against CCHFV is most limited. Interestingly, in this study it is shown that replicating CCHFV delays substantially the IFN response, possibly by interfering with the activation pathway of IRF-3. In addition, it is demonstrated that CCHFV replication is almost insensitive to subsequent treatment with interferon-alpha. Once the virus is replicating, virus replication is more or less insensitive to the antiviral effects induced by the interferon. By using an interferon bioassay, it is shown that infected cells secrete interferon relatively late after infection, that is, 48 hr post-infection. In summary, the results suggest the presence of a virulence factor encoded by CCHFV that delays the host defence in order to allow rapid viral spread in the host.

Spontaneous mutations in the human CMV HLA class I homologue UL18 affect its binding to the inhibitory receptor LIR-1/ILT2/CD85j

Human cytomegalovirus (HCMV) down-regulates cell surface expression of HLA class I molecules (HLA-I). UL18, an HCMV-encoded HLA-I homologue, has been proposed to protect virus-infected cells against NK cell recognition by engaging the inhibitory receptor leukocyte Ig-like receptor (LIR)-1, which also binds a broad spectrum of HLA-I alleles, including HLA-G1. Because genetic and biological differences exist among HCMV strains, we characterized laboratory (AD169) and clinical (4636, 13B, 109B) strain-derived UL18 proteins. Compared to the known AD169-derived UL18, mutations were found in clinical strain-derived UL18. They were clustered in the alpha3 domain (13B), previously shown to be critical for LIR-1 binding, or in the alpha1 domain (4636). Iotan cytotoxicity assays, pretreatment of LIR-1+ NKL with soluble 4636-UL18 completely abolished LIR-1-dependent protection from NK lysis, conferred by the expression of HLA-G1 on target cells (721.221-HLA-G1+). Similarly, flow cytometry, Biacore and ELISA experiments showed 4636-UL18 and 13B-UL18 to have the strongest binding capacity to LIR-1. Our results suggest the importance of two independent UL18 regions for LIR-1 binding, one localized on the tip of the alpha3 domain, and another composed of two loops that emerge from the alpha1 domain. Strain variations in these domains may result in different UL18-mediated effects on LIR-1+ cells during the course of HCMV infection.

LightUp probes in clinical diagnostics

The LightUp^® Probe technology has now matured and reached the phase where it has been implemented in commercial reagent kits, i.e. the ReSSQ^® product line. Several properties of the LightUp^® probes make them particularly suitable for clinical settings. For instance, extraordinary shelf life and a chemical stability that allows convenient fridge storage. The origin of the higher stability of LightUp^® probe kits compared to others, based on alternative probe technologies, is partly the relatively good stability of cyanine dyes but also the resistance towards nucleases and proteases of the synthetic DNA analogue peptide nucleic acid that is used as the sequence recognizing element in LightUp probes. It is clear from recent trends in the PCR amplification hardware technology that the instrumentation is becoming more flexible and less adapted for dedicated probe chemistries. This will pave the way for increased standardization in the field of DNA diagnostics and the development of cross-platform assays.

In the present review the LightUp technology will briefly be presented and discussed. The utility of the technology will be illustrated by examples from cytomegalovirus quantification and monitoring of the viral load of the SARS Coronavirus. An example of cancer diagnostics by detection of altered gene expression patterns will also be shown.

Nitric oxide inhibits the replication cycle of severe acute respiratory syndrome coronavirus

Nitric oxide (NO) is an important signaling molecule between cells which has been shown to have an inhibitory effect on some virus infections. The purpose of this study was to examine whether NO inhibits the replication cycle of the severe acute respiratory syndrome coronavirus (SARS CoV) in vitro. We found that an organic NO donor, S-nitroso-N-acetylpenicillamine, significantly inhibited the replication cycle of SARS CoV in a concentration-dependent manner. We also show here that NO inhibits viral protein and RNA synthesis. Furthermore, we demonstrate that NO generated by inducible nitric oxide synthase, an enzyme that produces NO, inhibits the SARS CoV replication cycle.

Human MxA protein inhibits the replication of Crimean-Congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever virus (CCHFV) belongs to the genus Nairovirus within the family Bunyaviridae and is the causative agent of severe hemorrhagic fever. Despite increasing knowledge about hemorrhagic fever viruses, the factors determining their pathogenicity are still poorly understood. The interferon-induced MxA protein has been shown to have an inhibitory effect on several members of the Bunyaviridae family, but the effect of MxA against CCHFV has not previously been studied. Here, we report that human MxA has antiviral activity against CCHFV. The yield of progeny virus in cells constitutively expressing MxA was reduced up to 1,000-fold compared with control cells, and accumulation of viral genomes was blocked. Confocal microscopy revealed that MxA colocalizes with the nucleocapsid protein (NP) of CCHFV in the perinuclear regions of infected cells. Furthermore, we found that MxA interacted with NP by using a coimmunoprecipitation assay. We also found that an amino acid substitution (E645R) within the C-terminal domain of MxA resulted in a loss of MxA antiviral activity and, concomitantly, in the capacity to interact with CCHFV NP. These results suggest that MxA, by interacting with a component of the nucleocapsid, prevents replication of CCHFV viral RNA and thereby inhibits the production of new infectious virus particles.

Effects of human cytomegalovirus infection on ligands for the activating NKG2D receptor of NK cells: up-regulation of UL16-binding protein (ULBP)1 and ULBP2 is counteracted by the viral UL16 protein

Human CMV (HCMV) interferes with NK cell functions at various levels. The HCMV glycoprotein UL16 binds some of the ligands recognized by the NK-activating receptor NKG2D, namely UL16-binding proteins (ULBP) 1 and 2 and MHC class I-related chain B, possibly representing another mechanism of viral immune escape. This study addressed the expression and function of these proteins in infected cells. HCMV induced the expression of all three ULBPs, which were predominantly localized in the endoplasmic reticulum of infected fibroblasts together with UL16. However, while at a lower viral dose ULBP1 and 2 surface expression was completely inhibited compared to ULBP3, at a higher viral dose cell surface expression of ULBP1 and ULBP2 was delayed. The induction of ULBPs correlated with an increased dependency on NKG2D for recognition; however, the overall NK sensitivity did not change (suggesting that additional viral mechanisms interfere with NKG2D-independent pathways for recognition). Infection with a UL16 deletion mutant virus resulted in a different pattern compared to the wild type: all three ULBP molecules were induced with similar kinetics at the cell surface, accompanied by a pronounced, entirely NKG2D-dependent increase in NK sensitivity. Together our findings show that upon infection with HCMV, the host cell responds by expression of ULBPs and increased susceptibility to the NKG2D-mediated component of NK cell recognition, but UL16 limits these effects by interfering with the surface expression of ULBP1 and ULBP2.

Point mutations induced by foscarnet (PFA) in the human cytomegalovirus DNA polymerase

BACKGROUND

In vitro selection of viruses with decreased drug susceptibility is a useful tool for mapping drug resistance-associated alterations, evaluating cross-resistance profiles, and elucidating molecular mechanisms of antiviral activity.

OBJECTIVES

To provide data on mechanisms of selective drug action and features of drug resistance that may be clinically important.

STUDY DESIGN

Foscarnet (PFA) and ganciclovir (GCV) were used to induce mutants of the human cytomegalovirus (HCMV) Towne strain.

RESULTS

Three new mutations, selected in the presence of PFA, were identified with single base substitutions resulting in T419M, Q578H, and L773V in conserved regions of the HCMV DNA polymerase. None of these mutations have been reported previously. These mutations conferred resistance to PFA but did not change the susceptibility to GCV. A mutant was selected in the presence of GCV. This GCV-selected mutant had no mutation in the UL54 but had an amino acid alteration at codon M460V of UL97, which conferred resistance to GCV. All the mutants had the same growth phenotype as the parental laboratory strain Towne.

CONCLUSIONS

We have determined three novel alterations in HCMV DNA polymerase inducing reduced susceptibility to PFA. None of these alterations changed the growth phenotype of the parental virus.

A case of diffuse leptomeningeal oligodendrogliomatosis associated with HHV-6 variant A

We describe a rare case of diffuse leptomeningeal oligodendrogliomatosis associated with the human herpes virus 6 variant A (HHV-6 A). A 2-year-old boy presented with progressive neurological symptoms and hydrocephalus. The patient had a VP shunt placement but did not fully recover. HHV-6 A was detected in both CSF and serum by nested PCR. His symptoms improved repeatedly, but temporarily, on antiviral treatment. An open brain biopsy, ten months after presentation, revealed leptomeningeal tumour as well as the presence of viral DNA in the tumour tissue. The role of HHV-6 A could be that of a reactivated opportunist. However, this case also raises the question whether this neurotropic virus, with malignant transforming properties in vitro, may have a role in pathogenesis in some cases of brain malignancy.

Pivotal role of KARAP/DAP12 adaptor molecule in the natural killer cell-mediated resistance to murine cytomegalovirus infection

Natural killer (NK) cells are major contributors to early defense against infections. Their effector functions are controlled by a balance between activating and inhibiting signals. To date, however, the involvement of NK cell activating receptors and signaling pathways in the defense against pathogens has not been extensively investigated. In mice, several NK cell activating receptors are coexpressed with and function through the immunoreceptor tyrosine-based activation motif (ITAM)-bearing molecule KARAP/DAP12. Here, we have analyzed the role of KARAP/DAP12 in the early antiviral response to murine cytomegalovirus (MCMV). In KARAP/DAP12 mutant mice bearing a nonfunctional ITAM, we found a considerable increase in viral titers in the spleen (30-40-fold) and in the liver (2-5-fold). These effects were attributed to NK cells. The formation of hepatic inflammatory foci appeared similar in wild-type and mutant mice, but the latter more frequently developed severe hepatitis with large areas of focal necrosis. Moreover, the percentage of hepatic NK cells producing interferon gamma was reduced by 56 +/- 22% in the absence of a functional KARAP/DAP12. This is the first study that shows a crucial role for a particular activating signaling pathway, in this case the one induced through KARAP/DAP12, in the NK cell-mediated resistance to an infection. Our results are discussed in relation to recent reports demonstrating that innate resistance to MCMV requires the presence of NK cells expressing the KARAP/DAP12-associated receptor Ly49H.

Variations in the cytomegalovirus DNA polymerase and phosphotransferase genes in relation to foscarnet and ganciclovir sensitivity

BACKGROUND

Identification of human cytomegalovirus (CMV) genome variation is important for understanding mutations associated with drug resistance.

OBJECTIVES

To investigate the CMV resistance to foscarnet (PFA) and ganciclovir (GCV) in patients treated with antiviral drugs and to identify the DNA polymerase (UL54) and phosphotransferase (UL97) gene mutations inducing resistance.

STUDY DESIGN

Antiviral susceptibility of CMV strains/isolates for PFA and GCV was compared by plaque reduction assay and in situ ELISA. UL54 and UL97 gene mutations were identified by sequencing. Growth phenotype of two CMV recombinants with mutations in UL54 was studied.

RESULTS

Six of seven GCV resistant strains had alterations within the UL97. Five of them also had alterations in the UL54 (F412C, L802M or K513E), previously shown to induce GCV resistance. Seven isolates had no or reduced susceptibility to PFA, which had alterations in the UL54 (D588N, E756K, V781I or L802M). By in vitro mutagenesis, it was shown that a mutation at codon D588N of UL54 conferred 9-fold reduced susceptibility to PFA, while a mutation at codon V781I induced 4-fold reduced susceptibility to PFA and GCV. Both recombinants showed the same kinetics of protein expression (IE, E, and L antigen) and virus yields as the CMV Towne strain.

CONCLUSIONS

The recombinants containing alterations within the UL54 (D588N and V781I) showed a reduced susceptibility to antiviral drugs but no change in the replication rate compared to the CMV Towne.

Sequence analysis of UL54 and UL97 genes and evaluation of antiviral susceptibility of human cytomegalovirus isolates obtained from kidney allograft recipients before and after treatment

The frequency of infections caused by drug-resistant cytomegalovirus (CMV) in solid-organ transplant recipients is not known. Only a few resistant strains have been described in transplant recipients. Antiviral susceptibility to ganciclovir (GCV) and foscarnet (PFA) of CMV isolates from 24 renal transplant patients with CMV viremia and CMV disease before and after therapy were investigated by a solid phase ELISA. The CMV DNA polymerase (UL54) and viral phosphotransferase (UL97) genes were also sequenced. Ten patients did not receive antiviral treatment; five and nine patients were treated with PFA and GCV, respectively. No appearance of drug-resistant viruses was observed in the present study, but one isolate showed a reduced sensitivity to PFA after treatment with GCV. This finding could not be explained by the presence or development of mutations that have been associated with drug resistance in UL54. We found no evidence that short-term treatment of CMV with PFA- or GCV-induced resistance.

Synergistic effect of IFN-gamma and human cytomegalovirus protein UL40 in the HLA-E-dependent protection from NK cell-mediated cytotoxicity

Human CMV (HCMV) has evolved several strategies to evade the immune system of the infected host. Here, we investigated the role of the HCMV-encoded protein UL40 in the modulation of NK cell lysis. UL40 carries in its leader sequence a nonameric peptide similar to that found in many HLA class I molecules leader sequences. This peptide up-regulates the expression of HLA-E, the ligand for the NK cell inhibitory receptor CD94/NKG2A. The UL40-encoded HLA-E-binding peptide was present in all HCMV clinical (4636, 13B, 109B, 3C) and laboratory (AD169) strains analyzed. However, transfection of UL40 in different cell lines (293T, 721.221, K562) did not consistently confer protection from NK lysis (as measured using NKL and the newly generated NK line Nishi), despite a moderate up-regulation of HLA-E. Interestingly, combined transfection and treatment with IFN-gamma increased the inhibitory effect, via an HLA-E- and CD94/NKG2A-dependent mechanism. Although cells transfected with UL40 derived from either AD169 or 3C showed protection from NK cell lysis, infection of fibroblasts with the viruses resulted in a strong inhibition only with the clinical strain 3C. Our results suggest that UL40 and IFN-gamma-dependent up-regulation of HLA-E is only one possible mechanism to avoid NK cell recognition of HCMV infected cells.

Growth phenotypes of cytomegalovirus isolates do not correlate with glycoprotein B, major immediate early genotypes or antiviral sensitivity

Human Cytomegalovirus (CMV) is generally described from in vitro experiments as a slowly replicating virus. A doubling time of one day in blood, however, has been shown in vivo. The growth phenotypes of CMV isolates and laboratory strains were studied in human fibroblasts. The viruses were found to replicate either rapidly or slowly. Comparison of CMV protein expression in lung and foreskin fibroblast cultures showed that two tissue culture adapted CMV strains (AD169 and Towne) and 3 clinical isolates belonged to the rapidly replicating viruses, whereas another 3 clinical isolates replicated slowly. CMV antigen concentrations were 6-fold and virus yields were 10-1000-fold higher for the rapidly replicating viruses than for the slow replicators. The antigen expression of two slowly replicating isolates was enhanced after 20 passages compared to the isolates at passage 5, but it was not as efficient as that of strain Towne. Slow or fast replication was related neither to major immediate early gene exon 4, and gB genotypes, nor to antiviral susceptibility. Proteins of the beta cascade may contribute to differences in the replication rate of CMV isolates.

Human cytomegalovirus strain-dependent changes in NK cell recognition of infected fibroblasts

NK cells play a key role in the control of CMV infection in mice, but the mechanism by which NK cells can recognize and kill CMV-infected cells is unclear. In this study, the modulation of NK cell susceptibility of human CMV (hCMV)-infected cells was examined. We used a human lung and a human foreskin fibroblast cell line infected with clinical isolates (4636, 13B, or 109B) or with laboratory strains (AD169, Towne). The results indicate that all three hCMV clinical isolates confer a strong NK resistance, whereas only marginal or variable effects in the NK recognition were found when the laboratory strains were used. The same results were obtained regardless of the conditions of infection, effector cell activation status, cell culture conditions, and/or donor-target cell combinations. The NK cell inhibition did not correlate with HLA class I expression levels on the surface of the target cell and was independent of the leukocyte Ig-like receptor-1, as evaluated in Ab blocking experiments. No relevant changes were detected in the adhesion molecules ICAM-I and LFA-3 expressed on the cell surface of cells infected with hCMV clinical and laboratory strains. We conclude that hCMV possesses other mechanisms, related neither to target cell expression of HLA-I or adhesion molecules nor to NK cell expression of leukocyte Ig-like receptor-1, that confer resistance to NK cell recognition. Such mechanisms may be lost during in vitro passage of the virus. These results emphasize the differences between clinical hCMV isolates compared with laboratory strains.

Reactivation of human herpesvirus 6 during pregnancy

Reactivation of human herpesvirus 6 (HHV-6) and cytomegalovirus (CMV) during pregnancy and transmission of the viruses to the fetus were investigated by polymerase chain reaction (PCR) and serology. In all, 104 blood samples were obtained 3 times during pregnancy and once at delivery. In another 107 women, samples were obtained only at delivery. Cord blood samples were obtained from both groups of women. HHV-6 DNA was detected in 41%-44% of the samples during months 3-8 of pregnancy, in 25% at delivery, and in 24% of age-matched controls. HHV-6 DNA was found in 1.0% of the cord blood samples. CMV DNA was detected in 1.7% of leukocytes from 104 pregnant women but in no cord blood sample. IgG antibodies to HHV-6 were found in 96% and CMV IgG in 62.5% of the women. HHV-6 IgG titers were significantly higher in HHV-6 PCR-positive women. Thus, HHV-6 reactivation seems common during pregnancy, and transfer of HHV-6 to the fetus may occur in approximately 1% of pregnancies.

Free thiol groups are essential for infectivity of human cytomegalovirus

The membrane-impermeable thiol blocker 5'5-dithiobis 2- nitrobenzoic acid (DTNB) blocked infectivity of human cytomegalovirus (CMV) although the virus still bound to cells. DTNB-treated CMV regained 65% of its infectivity after incubation with the disulfide bond-reducing agent dithiothreitol. These observations suggest that free thiol groups on CMV are required for infectivity and may participate in disulfide bond formation during virus entry.

Infrequent detection of cytomegalovirus and Epstein-Barr virus DNA in synovial membrane of patients with rheumatoid arthritis

OBJECTIVE

To study the role of the cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes simplex virus types 1 and 2 (HSV-1 and 2), varicella zoster virus (VZV), and human herpes virus 6 (HHV-6) in the etiology of rheumatoid arthritis (RA).

METHODS

Polymerase chain reaction (PCR) was used to detect DNA of the different herpes viruses in synovial membranes from 31 patients with chronic RA and 14 control patients. Specific antibodies were determined by indirect immunofluorescence and ELISA.

RESULTS

Out of 31 patients with RA, CMV DNA was detected in synovial membranes from 2 patients and EBV DNA was detected in synovial membranes from 2 other patients. All samples from the patients with RA were negative for DNA from HSV-1 and 2, VZV, and HHV-6. All samples from the 14 control patients were negative in all PCR assays. No statistically significant differences in IgG antibodies were found for CMV, HSV-1, VZV, and HHV-6 in patients with RA compared to controls. Higher titers of IgG antibodies against EBV viral capsid antigen were found in patients with RA, with a significance of p < 0.05.

CONCLUSION

Both CMV and EBV DNA were detected in synovial membranes from 6% of the patients with RA. We cannot exclude the possibility that these viruses were associated with disease development in a minority of patients with RA.

Cytomegalovirus DNA in peripheral blood leukocytes and plasma from bone marrow transplant recipients

Granulocytes, monocytes, and T- and B-lymphocytes were separated from 28 blood samples collected from 5 bone marrow transplant (BMT) recipients. About 40% of granulocyte, monocyte, and B-lymphocyte samples were CMV DNA-positive by polymerase chain reaction in recipients with cytomegalovirus (CMV) infection. CMV DNA was rarely detected in separated T-lymphocytes. Within each of the simultaneously separated paired samples, there were several with single positive cell subtypes. Monocytes, granulocytes, and B-lymphocytes were the single positive samples in some instances. Thus, it is important to have all of the different cell subtypes present in samples for detection of CMV DNA in peripheral blood. We also studied the appearance of CMV DNA in plasma and peripheral blood leukocytes (PBLs) from 351 blood samples collected from 30 BMT recipients during a follow-up period of at least 3 months after BMT. All cell subtypes were represented in the PBL samples. In the 13 recipients who developed symptoms possibly associated with CMV infection or CMV disease, a correlation with the detection of CMV DNA in < or = 2 x 10(5) PBLs was found. In PBLs from 11 of the 13 BMT recipients, CMV DNA was detected before the onset of symptoms. CMV DNA was not detected in < or = 2 x 10(5) PBLs from recipients without CMV infection. The virus load in PBLs decreased during ganciclovir treatment. Nine of the 13 recipients displayed PCR-positive plasma samples, and CMV DNA was detected frequently after the onset of symptoms.