Detection of late pp67-mRNA by NASBA in peripheral blood for the diagnosis of human cytomegalovirus disease in AIDS patients

Isothermal Amplification of Nucleic Acids

Isothermal amplification of nucleic acids is a simple process that rapidly and efficiently accumulates nucleic acid sequences at constant temperature. Since the early 1990s, various isothermal amplification techniques have been developed as alternatives to polymerase chain reaction (PCR). These isothermal amplification methods have been used for biosensing targets such as DNA, RNA, cells, proteins, small molecules, and ions. The applications of these techniques for in situ or intracellular bioimaging and sequencing have been amply demonstrated. Amplicons produced by isothermal amplification methods have also been utilized to construct versatile nucleic acid nanomaterials for promising applications in biomedicine, bioimaging, and biosensing. The integration of isothermal amplification into microsystems or portable devices improves nucleic acid-based on-site assays and confers high sensitivity. Single-cell and single-molecule analyses have also been implemented based on integrated microfluidic systems. In this review, we provide a comprehensive overview of the isothermal amplification of nucleic acids encompassing work published in the past two decades. First, different isothermal amplification techniques are classified into three types based on reaction kinetics. Then, we summarize the applications of isothermal amplification in bioanalysis, diagnostics, nanotechnology, materials science, and device integration. Finally, several challenges and perspectives in the field are discussed.

Multiple intravitreal injections of ganciclovir for cytomegalovirus retinitis after stem-cell transplantation

BACKGROUND

Cytomegalovirus (CMV) infection is a major cause of morbidity and mortality in patients after hematopoietic stem cell transplantation (HSCT). Although much effort has been put into dealing with CMV retinitis secondary to acquired immunodeficiency syndrome (AIDS), the few reports which have been published have mainly focused on treatment of CMVR after HSCT.

METHODS

This clinical interventional retrospective study included 14 patients (eight men; mean age 23.89 ± 12.09; 23 eyes) who suffered from CMV retinitis after stem-cell transplantation, in order to evaluate the efficacy and safety of multiple intravitreal injections of ganciclovir (IVG) for patients with CMV retinitis. All patients received 4 injections of IVG of 1 mg at 1 week intervals, and were followed up weekly for at least 2 months with measurement of best-corrected visual acuity (BCVA) and CMV levels in anterior aqueous humor with real-time polymerase chain reaction. Anterior aqueous humor was obtained before each injection.

RESULTS

The levels of CMV in anterior aqueous humor showed significant decrease from (6.34 ± 15.78) × 10(5) copies/ml at baseline to (5.22 ± 12.15) × 10(3) copies/ml at 1 month (P < 0.001, Mann-Whitney U test). CMV couldn't be detected in 11 eyes (47.8 %) after two injections, and this rose to 18 eyes (78.3 %) at 1 month. The mean logMAR BCVA was 0.659 ± 0.572 at baseline and 0.680 ± 0.527 at 2 months, which suggested no significant improvement (P = 0.736, Mann-Whitney U test) during the procedure. All patients experienced improved vitreous opacity and diminished area of the lesion under funduscopy after 4 injections of IVG. No severe complications developed.

CONCLUSIONS

Multiple IVG seemed to be beneficial for patients with CMV retinitis after stem-cell transplantation, in reducing CMV levels in aqueous humor. Further study to optimize the dose of ganciclovir is needed in order to achieve better treatment outcomes.

Isothermal nucleic acid amplification technologies for point-of-care diagnostics: a critical review

Nucleic Acid Testing (NAT) promises rapid, sensitive and specific diagnosis of infectious, inherited and genetic disease. The next generation of diagnostic devices will interrogate the genetic determinants of such conditions at the point-of-care, affording clinicians prompt reliable diagnosis from which to guide more effective treatment. The complex biochemical nature of clinical samples, the low abundance of nucleic acid targets in the majority of clinical samples and existing biosensor technology indicate that some form of nucleic acid amplification will be required to obtain clinically relevant sensitivities from the small samples used in point-of-care testing (POCT). This publication provides an overview and thorough review of existing technologies for nucleic acid amplification. The different methods are compared and their suitability for POCT adaptation are discussed. Current commercial products employing isothermal amplification strategies are also investigated. In conclusion we identify the factors impeding the integration of the methods discussed in fully automated, sample-to-answer POCT devices.

Overview of the diagnosis of cytomegalovirus infection

Cytomegalovirus (CMV) is recognized as the most common congenital viral infection in humans and an important cause of morbidity and mortality in immunocompromised hosts. This recognition of the clinical importance of invasive CMV disease in the setting of immunodeficiency and in children with congenital CMV infection has led to the development of new diagnostic procedures for the rapid identification of CMV. Diagnosis of acute maternal CMV infection by the presence of immunoglobulin (Ig)M and low-avidity IgG requires confirmation of fetal infection, which is typically performed using polymerase chain reaction (PCR) assays for CMV on amniotic fluid. Viral culture of the urine and saliva obtained within the first two weeks of life continues to be the gold standard for diagnosis of congenitally-infected infants. PCR assays of dried blood spots from newborns have been shown to lack sufficient sensitivity for the identification of most neonates with congenital CMV infection for universal screening purposes. However, saliva PCR assays are currently being assessed as a useful screening method for congenital CMV infection. In the immunocompromised host, newer rapid diagnostic assays, such as phosphoprotein 65 antigenemia and CMV real-time PCR of blood or plasma have allowed for preemptive treatment, reducing morbidity and mortality. However, lack of standardized real-time PCR protocols hinders the comparison of data from different centers and the development of uniform guidelines for the management of invasive CMV infections in immunocompromised individuals.

Clinical utility of CMV early and late transcript detection with NASBA in bronchoalveolar lavages

BACKGROUND

Cytomegalovirus (CMV) infection can cause severe disease in immunocompromised individuals, with CMV pneumonia, most commonly seen in lung or bone marrow transplant recipients, carrying a particularly high fatality rate. Early and accurate diagnosis of CMV pneumonia is therefore critical.

OBJECTIVES

Current diagnostic tests for CMV pneumonia in bronchoalveolar lavage (BAL) specimens are either insensitive or poor prognostic indicators of disease. We therefore examined nucleic acid sequence-based amplification (NASBA) assays for CMV transcripts in BAL for the prediction of CMV pneumonia and associated diseases.

STUDY DESIGN

A total of 220 BAL specimens from lung transplant recipients and other patients with suspected viral pneumonia were studied. Ninety-nine samples had previously tested positive for CMV by shell vial (SV) culture, while the other 121 had tested negative. All specimens were assayed for CMV pp67 and immediate early (IE) transcripts by NASBA. Results were correlated with evidence of concurrent or subsequent CMV pneumonia, rejection, and infection with other microbes.

RESULTS

From a total of 220 BAL specimens, 27 tested positive for pp67 mRNA, 25 tested positive for IE mRNA, and 17 tested positive for both. Only 10 specimens tested positive for CMV by either or both NASBA assays while testing negative by SV assay. However, 74 specimens were SV positive but negative in both NASBA assays. Detection of CMV by any of the three methods was associated with an increased prevalence of pneumonia (i.e., pulmonary interstitial inflammation with radiographic or clinical evidence of lung injury), but not with pulmonary CMV pathology. Detection of CMV by SV was associated with moderate to severe graft rejection. There was no evidence of increased bacterial or fungal pulmonary infections associated with a positive CMV result by any of the three assays.

CONCLUSIONS

Detection of either CMV pp67 or IE mRNA transcripts by NASBA in BAL specimens can occasionally identify CMV infections that are negative by conventional shell vial culture, but does not have sufficient sensitivity or positive predictive value to be employed routinely for pre emptive management of pulmonary CMV disease in transplant recipients.

Comparison of two commercially available pp65 antigenemia tests and COBAS Amplicor CMV Monitor for early detection and quantification of episodes of human CMV-viremia in transplant recipients

The performance of two commercially available CMV pp65 antigenemia (AG) assays (CINA kit, Argene Biosoft, CK, and CMV Brite kit, IQ Products, CBK), and a quantitative PCR test (COBAS Amplicor CMV Monitor Test, Roche Diagnostics, CACM) was evaluated with 667 blood samples from 215 transplant recipients. The diagnostic value of the three tests was defined by their ability to detect episodes of systemic CMV activity. A test score was defined, assigning 7 virtual units (VU) for any episode detected first, 5 VU for any episode detected second, and three VU for any episode detected last. Within the evaluated collective, the following overall scores could be determined for the three assays: 45 VU for the CK, 39 for CACM and 31 for the CBK assay. We conclude from our results that (1) the CK is superior to the CBK assay in detecting episodes of CMV antigenemia, and (2) quantitative serum CMV PCR with CACM is not generally superior to pp65 antigenemia testing.

Quantitative detection of HIV-1 RNA using NucliSens EasyQ HIV-1 assay

HIV-1 RNA viral load has become the major biological marker for disease prognosis and outcome of antiretroviral therapy in the treatment of HIV-infected individuals. The aim of this study was to compare the performance of the new CE marked NucliSens EasyQ HIV-1 assay with NucliSens HIV-1 QT assay (reference method). NucliSens EasyQ HIV-1 (EasyQ) couples nucleic acid sequence-based amplification (NASBA) with real-time detection using molecular beacons utilizing the NucliSens EasyQ analyzer. NASBA is a sensitive, isothermal, transcription-based amplification system designed specifically for the detection of RNA targets. There was significant correlation (r = 0.878, P < 0.0001) between the two different assays in the analysis of clinical samples and the frequency of concordant results (log difference <0.5) was 74%. The two assays detected HIV-1 RNA in 81 specimens, and neither detected (below the lower detection limit, 400 copies/ml for NucliSens HIV-1 QT and 500IU/ml for EasyQ) HIV-1 RNA in 12 specimens. Three clinical specimens had detectable HIV-1 RNA using the EasyQ only, and two specimens had detectable HIV-1 RNA using the NucliSens HIV-1 QT only. The EasyQ procedure can analyze 48 clinical samples within 6h. The coefficient of variation of EasyQ ranged from 3.0 to 9.5% (3% at 4.9 log; 5.7% at 3.7 log; 9.5% at 2.7 log). The new assay is shown to be a rapid, convenient, and reliable procedure for HIV-1 RNA viral load monitoring.

Human cytomegalovirus: clinical aspects, immune regulation, and emerging treatments

After initial infection, human cytomegalovirus remains in a persistent state with the host. Immunity against the virus controls replication, although intermitent viral shedding can still take place in the seropositive immunocompetent person. Replication of cytomegalovirus in the absence of an effective immune response is central to the pathogenesis of disease. Therefore, complications are primarily seen in individuals whose immune system is immature, or is suppressed by drug treatment or coinfection with other pathogens. Although our increasing knowledge of the host-virus relationship has lead to the development of new pharmacological strategies for cytomegalovirus-associated infections, these strategies all have limitations-eg, drug toxicities, development of resistance, poor oral bioavailability, and low potency. Immune-based therapies to complement pharmacological strategies for the successful treatment of virus-associated complications should be prospectively investigated.