Identification and characterization of two antisense transcripts from the major immediate early region of rat cytomegalovirus

We have identified and characterized two antisense transcripts from the rat cytomegalovirus (RCMV) major immediate early (MIE) region. These transcripts, designated IE-AS1 and IE-AS2, are complementary to part of the sense IE1 transcript. The IE-AS transcripts were first detected in peripheral blood leukocytes (PBL) of RCMV-infected rats at 7 days post-infection (pi) in the absence of IE1 transcription. Nevertheless, both the IE1 and IE-AS transcripts were found at the same time in the salivary glands of RCMV-infected rats at 7 and 120 days pi as well as in RCMV-infected rat embryo fibroblasts (REFs) at 48 h pi.

Patients with an unclassified genetic variant in the BRCA1 or BRCA2 genes show different clinical features from those with a mutation

PURPOSE

To obtain and compare the probabilities of finding a mutation in the BRCA1 or BRCA2 genes, the clinical features, and the family history among patients with an unclassified variant (UV) and those with a pathogenic mutation.

PATIENTS AND METHODS

The study included 70 patients: 24 with a UV (BRCA1, n = 4; BRCA2, n = 19; both, n = 1), and 46 with a mutation (BRCA1, n = 32; BRCA2, n = 14). Two of the UVs were novel variants; the rest had been reported previously as UVs. Probabilities of finding a mutation were retrospectively obtained using BRCAPRO and Myriad II programs.

RESULTS

The probability to detect a mutation was significantly lower in the group of patients with a UV than in those with a mutation (BRCAPRO [mean +/- standard deviation], 0.297 +/- 0.312 v 0.627 +/- 0.315, P = .001; and Myriad II, 0.124 +/- 0.090 v 0.283 +/- 0.176, P = .001, respectively). Independent predictive factors of finding either a UV or a mutation were number of affected relatives (2.9 +/- 1.4 v 4.0 +/- 1.9; P = .039) and number of tumors among relatives (3.3 +/- 1.4 v 4.4 +/- 1.8; P = .031), respectively.

CONCLUSION

The combined data about the predictive models show significant differences between both groups. Individual probabilities can be regarded as a help to guide the clinical management of patients with a UV in those genes. However, a definitive conclusion about the pathogenicity of a UV can not be obtained from the clinical features alone, but only in combination with biochemical and epidemiologic data.

Onset and duration of cytomegalovirus immediate early 1 mRNA expression in the blood of renal transplant recipients

Human cytomegalovirus (CMV) messenger (m) RNA expression in circulating leukocytes reflects directly viral activity in the human host. In this study, sixty-nine patients were monitored prospectively for CMV infection and mRNA expression during the first year after renal transplantation. Of the 69 recipients, 58 (84%) recipients were positive for CMV immediate early 1 (IE1) mRNA as detected by nucleic acid sequence-based amplification. The median onset of IE1 expression started at day 22 after transplantation and continued for a median duration of 82 days. IE1 mRNA expression started significantly earlier in recipients who developed an active CMV infection (P = 0.001) and in mycophenolate mofetil (MMF) treated recipients (P = 0.002). The duration of IE1 mRNA expression was significantly longer in recipients that had previously an early onset of IE1 mRNA expression (P = 0.001) and in recipients with active CMV infection (P = 0.007). Remarkably, longer prednisolone intake was correlated with a significantly (P = 0.02) shorter duration of IE1 expression compared to a longer duration of IE1 expression in recipients with only a short prednisolone intake. In recipients infected with glycoprotein B (gB) type 1 CMV strains, the duration of IE1 expression was significantly (P = 0.04) shorter compared to recipients infected with non-gB type 1 CMV strains (64 days vs. 150 days). The study indicates that multiple factors play a role in the onset and/or duration of CMV IE1 mRNA expression, for example, MMF treatment, prednisolone intake, and gB type of the specific CMV strain. The clinical significance of these correlations remains to be studied in more detail.

A rat cytomegalovirus strain with a disruption of the r144 MHC class I-like gene is attenuated in the acute phase of infection in neonatal rats

We previously generated an RCMV strain in which the r144 gene, encoding a major histocompatibility complex class I homolog, had been deleted (RCMVdelta r144). To investigate the role of r144 during acute infection of neonatal rats, we infected three days-old neonatal rats with either RCMVdelta r144 or wild type (wt) RCMV and the presence of infectious virus as well as viral DNA in various organs was determined at either 3, 5 or 21 days p.i.. In addition, we assessed both type and number of inflammatory cells in these organs. Interestingly, a significantly lower concentration of infectious virus as well as viral DNA was found in spleens of RCMVdelta r144-infected rats than in those of wt RCMV-infected animals at 3 days p.i.. At the same time point, a significantly lower amount of infiltrating NK cells and monocytes/macrophages was seen in the spleens of RCMVdelta r144-infected rats than in spleens of rats infected with wt RCMV. At 21 days p.i., RCMVdelta r144-infected rats were found to have lower virus titers in the salivary glands than wt RCMV-infected animals. Significant differences between RCMVdelta r144- and wt RCMV-infected rats were detected neither at other time points nor at other sites. We conclude that after infection of neonatal rats, the replication of RCMVdelta r144 is severely restricted compared to wt RCMV.

Cytomegalovirus infection, viral DNA, and immediate early-1 gene expression in rejecting rat liver allografts

BACKGROUND

Cytomegalovirus (CMV) infection has been linked to acute and chronic rejection. We have previously shown that concomitant rat cytomegalovirus (RCMV) infection increases portal inflammation and bile duct destruction in rejecting rat liver allografts. Many of the pro-inflammatory effects of CMV have been attributed to the immediate early (IE) proteins of CMV. We wanted to investigate whether RCMV and IE-1 gene expression persist in the liver graft in our model.

METHODS

Liver transplantations were performed from PVG (RT1c) into BN (RT1n) rats. One day after transplantation, the rats were infected with RCMV. No immunosuppression was given. The graft infection was studied by viral culture, immunofluorescence, DNA in situ hybridization and RT-PCR for the detection of IE-1 mRNA at various time points.

RESULTS

RCMV caused an active infection from 5 days to 2 weeks after transplantation, during which infectious virus was found in the graft. Thereafter the cultures were negative. RCMV antigens and DNA were found in hepatocytes, endothelial, inflammatory, and bile duct cells during the active infection. At 4 weeks, RCMV DNA positive hepatocytes, endothelial, inflamma tory, and bile duct cells could still be found, but in much smaller quantities. IE-1 mRNA expression was, however, only detected during the active infection, not at 4 weeks postinfection.

CONCLUSIONS

RCMV IE-1 expression does not persist in the graft after the active infection, although some viral DNA can be detected in the graft up to 4 weeks. In our model, the CMV-induced increase in graft damage does not seem to require the continued expression of IE-1.

Diagnostic implications of human cytomegalovirus immediate early-1 and pp67 mRNA detection in whole-blood samples from liver transplant patients using nucleic acid sequence-based amplification

Nucleic acid sequence-based amplification (NASBA) was used for detection of the human cytomegalovirus (CMV) immediate early-1 (IE) and the late pp67 mRNA in 353 blood samples collected from 34 liver transplant patients. The diagnostic value of these assays was compared to that of the pp65 antigenemia assay. Overall, 95 and 42% of the antigenemia-positive samples were IE NASBA and pp67 NASBA positive, respectively. Although the results from pp67 NASBA and the antigenemia assay appeared to correspond poorly, a clear correlation was seen between pp67 NASBA-negative results and low numbers of pp65 antigen-positive cells. Twenty patients (59%) were treated with ganciclovir after the diagnosis of symptomatic CMV infection. Before initiation of the antiviral therapy, the antigenemia assay detected the onset of symptomatic infection in all patients, whereas 95 and 60% of these patients were IE NASBA and pp67 NASBA positive, respectively. Although the sensitivity of IE NASBA was very high, the positive predictive value (PPV) of this assay for the onset of a symptomatic infection was only 63%. The PPV of the antigenemia assay as well as pp67 NASBA was considerably higher (80 and 86%, respectively). Thus, the detection of IE mRNA using NASBA appears to be particularly useful as a marker for early initiation of antiviral therapy in patients at high risk for the development of a symptomatic infection. Also, IE NASBA was found to be more sensitive than the antigenemia assay for monitoring CMV infection during antiviral therapy. On the contrary, pp67 NASBA did not appear to have additional diagnostic value compared to the antigenemia assay.

Diagnostic value of nucleic-acid-sequence- based amplification for the detection of cytomegalovirus infection in renal and liver transplant recipients

To evaluate the diagnostic value of nucleic-acid-sequence-based amplification (NASBA) for the detection of cytomegalovirus (CMV) infection in transplant recipients, we compared immediate early 1 (IE1) and late pp67 mRNA detection by NASBA with the antigenemia assay, PCR and viral culture in 72 renal transplant (RTx) recipients and with antigenemia and serology in 25 liver transplant (LTx) recipients. Antigenemia, viral culture and pp67 NASBA were almost equivalent for the detection of CMV in RTx recipients. In LTx recipients, antigenemia detected more positive samples and more positive recipients compared to pp67 NASBA. In RTx recipients, PCR detected more positive samples and positive recipients compared to pp67 NASBA, antigenemia and viral culture. Also the first day of detection was slightly earlier for PCR. However, IE1 NASBA was the most sensitive test and detected 96% of all positive samples and positive transplant recipients. In addition, IE1 NASBA preceded PCR and all other positive results. This makes IE1 NASBA a very attractive screening test for the early detection of CMV infection.

The r144 major histocompatibility complex class I-like gene of rat cytomegalovirus is dispensable for both acute and long-term infection in the immunocompromised host

The rat cytomegalovirus (RCMV) r144 gene encodes a polypeptide homologous to major histocompatibility complex class I heavy chains. To study the role of r144 in virus replication, an RCMV r144 null mutant strain (RCMVDeltar144) was generated. This strain replicated with efficiency similar to that of wild-type (WT) RCMV in vitro. Additionally, WT RCMV and RCMVDeltar144 were found not to differ in their replication characteristics in vivo. First, the survival rate was similar among groups of immunosuppressed rats infected with either RCMVDeltar144 or WT RCMV. Second, the dissemination of virus did not differ in either RCMVDeltar144- or WT RCMV-infected, immunosuppressed rats, either in the acute phase of infection or approximately 1 year after infection. These data indicate that the RCMV r144 gene is essential neither for virus replication in the acute phase of infection nor for long-term infection in immunocompromised rats. Interestingly, in a local infection model in which footpads of immunosuppressed rats were inoculated with virus, a significantly higher number of infiltrating macrophage cells as well as of CD8(+) T cells was observed in WT RCMV-infected paws than in RCMVDeltar144-infected paws. This suggests that r144 might function in the interaction with these leukocytes in vivo.

Early detection of human cytomegalovirus infection after kidney transplantation by nucleic acid sequence-based amplification

BACKGROUND

The early detection of human cytomegalovirus infection after organ transplantation is a prerequisite for effective antiviral therapy. We evaluated the diagnostic value of monitoring the viral immediate-early (IE) 1 mRNA expression in blood leukocytes by nucleic acid sequence-based amplification (NASBA).

METHODS

Nucleic acids were isolated from 489 blood samples collected from 42 kidney transplant recipients and subjected to amplification by IE NASBA. The IE NASBA results were compared to those from pp67 NASBA, pp65 antigenemia, cell culture (DEAFF and CPE), and serology.

RESULTS

IE NASBA proved to be the most sensitive assay which detected the onset of both primary and secondary cytomegalovirus infection significantly earlier than the other assays.

CONCLUSIONS

The early detection of cytomegalovirus infection with IE NASBA would enable the start of effective antiviral therapy at an early state of infection to prevent cytomegalovirus disease in patients at risk.

Evaluation of a new method for early detection of active cytomegalovirus infections. A study in kidney transplant recipients

Early detection of active cytomegalovirus (CMV) infection after organ transplantation is necessary to start effective antiviral treatment. In the present study, blood specimens of kidney transplant recipients (n = 38) were monitored for the expression of CMV immediate early (IE) and late (L) mRNA using nucleic acid sequence-based amplification (NASBA). Results were compared with virus isolation, pp65 antigenemia and serology. In patients developing active CMV infection, pp65 antigen and L mRNA were detected simultaneously. At the same time, positive cell culture results could be reported to the clinic. CMV was detected significantly earlier with IE NASBA than with the other assays. However, the specificity of IE NASBA is lower than that of antigenemia, late NASBA and cell culture. Early detection of IE mRNA is especially useful for patients at high risk of developing symptomatic CMV infection in order that early, adequate antiviral therapy may be started. Late NASBA can be used to monitor further development of CMV infection, comparable to antigenemia.

Diagnostic value of monitoring human cytomegalovirus late pp67 mRNA expression in renal-allograft recipients by nucleic acid sequence-based amplification

The diagnostic value of monitoring human cytomegalovirus (HCMV) late pp67 mRNA expression by nucleic acid sequence-based amplification (NASBA) after renal-allograft transplantation was evaluated. RNAs were isolated from 489 whole-blood specimens of 42 patients for the specific amplification of the late pp67 (UL65) mRNA. NASBA results were compared to results from the pp65 antigenemia assay, virus isolation by cell culture, and serology. The sensitivity value for NASBA proved to be higher than that for the antigenemia assay (50 versus 35%) for the detection of HCMV infection, while the sensitivity values of cell culture and NASBA were comparable (54 and 50%, respectively). NASBA detected the onset of HCMV infection simultaneously with cell culture and the antigenemia assay. Both the antigenemia assay and NASBA are very specific (100%) and highly predictive (100%) for the onset of HCMV infection. Antiviral therapy with ganciclovir resulted in negative results for cell culture, the antigenemia assay, and NASBA. In conclusion, monitoring HCMV pp67 mRNA expression by NASBA is a highly specific method for the detection of HCMV infection in renal-allograft recipients and is more sensitive than the antigenemia assay. Furthermore, NASBA can be used to monitor the progression of HCMV infections and the effect of antiviral therapy on viral activity.

Analysis of the 3' terminal sequence recognized by the Rift Valley fever virus transcription complex in its ambisense S segment

A reconstituted transcription system composed of the Rift Valley fever phlebovirus (Bunyaviridae family) proteins L and N expressed via recombinant vaccinia viruses and an S-like model RNA containing the CAT gene in the antisense orientation, has been described previously by Lopez et al. (J. Virol., 1995, 69, 3972-3979). We extended the use of this in vivo system to determine the sequence at the 3' end of the ambisense S segment recognized by the transcription complex. A mutational analysis of the sequences at the 3' end of the S-like genomic or antigenomic RNA was undertaken. The data indicated that the minimal sequence required for transcription resides in the 13 first 3' nucleotides of the genomic or antigenomic RNA. In these sequences, two regions appeared crucial: the bases at positions 3 to 8 and the purine at position 13. In addition, the terminal repeat ...GU could be deleted without affecting significantly the template activity of the RNA. These data support the prime and realign mechanism proposed recently for Bunya- and Arenaviruses