Patent Application
20130302786
The present application claims the benefit of priority under 35 U.S.C. §119(a) of European application EP12166266.2 filed on May 1, 2012. The entire disclosure of the above-referenced application is hereby incorporated herein by reference.
The present invention relates to control concepts for diagnostic nucleic acid testing using amplification. In diagnostic tests for detecting or quantitating target nucleic acids by amplification, different controls are generally used. Internal controls are control nucleic acids that are added to the reaction mixtures and allow to control for the quality of every single amplification reaction and/or to quantitate the target nucleic acid in the reaction. Furthermore, negative controls, which are devoid of target nucleic acids, are run to ensure that the reagents used are not contaminated with target nucleic acids, Finally, positive controls are also used to ensure proper functioning of the system (instrument and reagents etc). Generally, for each assay, a corresponding positive control is provided. For example, for an HIV assay, a positive control comprising HIV nucleic acids is provided. For a HBV assay, a positive control comprising HBV nucleic acids is provided. For an assay for simultaneous qualitative and quantitative detection of HIV, HBV and HCV in a single vial, a positive control comprising a mixture of HIV, HBV and HCV is provided. Thus, the positive controls comprise exactly the target nucleic acids for which the assay is designed. This necessitates separate manufacturing of positive controls for each assay. Furthermore, separate control vials for each assay have to be provided to instrument systems in which the methods for detecting or quantitating target nucleic acids are performed.
The invention relates to a method of detecting or quantitating at least two different target nucleic acids in separate vials, comprising:
The methods additionally comprise amplifying in parallel with a) and b) a negative control in a fifth vial, wherein the negative control is provided from a second single negative control stock solution comprised in a negative control vial. The methods can be performed in an automated analyzer.
In an embodiment the positive control vial is provided in a rack, and wherein the negative control vial is provided in a second rack different from the rack comprising the positive control vial. In an embodiment in the rack comprising the positive control vial, a negative control vial is absent; or in the rack comprising the negative control vial, a positive control vial is absent. In an embodiment, the rack comprising the positive control vial comprises at least two positive control vials, wherein all of the at least two positive control vials comprise an identical mixture of positive control nucleic acids.
In another embodiment, at least three different target nucleic acids are detected or quantitated, additionally comprising: in step a), amplifying a third target nucleic acid in a sixth vial without amplifying the first or second target nucleic acid, and in step b), additionally amplifying a third positive control nucleic acid, wherein the third positive control nucleic acid is a positive control for the third target nucleic acid, wherein the third positive control nucleic acid is amplified in a seventh vial, and the first positive control nucleic acid, the second positive control nucleic acid and the third positive control nucleic acid are provided to the third vial, the fourth vial and the seventh vial from a positive control vial comprising a single positive control stock solution comprising a mixture of the first positive control nucleic acid, the second positive control nucleic acid and the third positive control nucleic acid before amplification.
In an embodiment, all positive control vials comprised in the rack comprise the positive control nucleic acids at a concentration of 1×10E5 to 1×10E8 copies/ml or of 1×10E2 to 5×10E3 copies/ml.
The invention further relates to kits comprising a rack comprising at least two positive control vials, wherein each of the positive control vials comprises a stock solution of a mixture of at least two positive control nucleic acids; a label indicating a single target nucleic acid to be detected with the kit components, wherein the single target nucleic acid corresponds to one of the at least two positive control nucleic acids in the stock solution, and a master mix vial comprising a master mix comprising reagents for amplification of the single target nucleic acid and the corresponding positive control nucleic acid.
In an embodiment, the kit comprises a rack comprising at least two positive control vials, wherein each of said positive control vials comprises a stock solution of a mixture of at least two positive control nucleic acids; a label indicating all target nucleic acid for which the corresponding positive control nucleic acids are present in said stock solution, wherein said label also indicates that the rack comprising the stock solutions of positive control nucleic acids is for use in methods for detecting one of the target nucleic acids. Further in an embodiment, the rack comprises at least two openings for receiving the at least two positive control vials.
In an embodiment, a method of detecting or quantitating at least two different target nucleic acids in separate vials is provided, comprising
In an embodiment, further provided is
Furthermore, a kit is provided comprising a rack as described herein, wherein the rack comprises at least two positive control vials. The at least two positive control vials are held in said openings of said rack. Each of said positive control vials comprises a stock solution of a mixture of at least two positive control nucleic acids. The at least two positive control nucleic acids are for use as external positive controls in amplification reactions performed in said analyzer. The kit comprises a label, wherein said label indicates a single target nucleic acid to be detected with the kit components, wherein said target nucleic acid is one of the positive control nucleic acids in the positive control vials of the rack. The kit further comprises a master mix vial comprising a master mix comprising reagents for amplification of said target nucleic acid and the corresponding positive control nucleic acid. The kit does not comprise a master mix comprising reagents for amplification of target nucleic acids corresponding to the at least one positive control nucleic acid not corresponding to said target nucleic acid indicated on the label but present in the stock solution of said positive control vial.
A kit is also provided comprising a rack with at least two positive control vials, wherein each of said positive control vials comprises a stock solution of a mixture of at least two positive control nucleic acids; a label indicating all target nucleic acid for which the corresponding positive control nucleic acids are present in said stock solution. The label also indicates that the rack comprising the stock solutions of positive control nucleic acids is for use in methods for detecting one of the target nucleic acids, but not the other target nucleic acids for which the corresponding positive control nucleic acids are comprised in the stock solution, in a single vial.
A use of a mixture is provided, wherein said mixture comprises at least a first positive control nucleic acid and a second positive control nucleic acid in separate positive control reactions, wherein said first control nucleic acid is amplified in the absence of amplification of said second positive control nucleic acid, and said second positive control nucleic acid is amplified in the absence of amplification of said first control nucleic acid.
The invention relates to a method of detecting or quantitating at least two different target nucleic acids in separate vials comprising
The advantage of this method is that by using a single positive control stock solution comprising a mixture of at least two different target nucleic acids, only one single positive control stock solution of positive controls is required to run individual positive controls for assays that detect or quantitate different target nucleic acids. This provides improved efficiency and cost savings for manufacturing since larger batches of positive controls can be manufactured for different test kits. It also simplifies an analytical system for detecting or quantitating target nucleic acids since a single vial comprising a mixture of positive controls can be used for detecting or quantitating different target nucleic acids.
In the above method, amplifying the at least two target nucleic acids, wherein the first target nucleic acid is amplified in a first vial without amplifying the second target nucleic acid, and the second target nucleic acid is amplified in a second vial without amplifying the first target nucleic acid is achieved by adding only primers for specifically amplifying the first target nucleic acid to the first vial. Primers for amplifying the second or any further target nucleic acid are not added to the first vial and are, thus, absent from the first vial. Amplification of the second target nucleic acid is achieved by adding only primers for specifically amplifying the second target nucleic acid to the second vial. Primers for amplifying the first or any further target nucleic acid other than the second target nucleic acid are not added to the second vial and are, thus, absent from the second vial. Likewise, only primers for amplifying the positive control for the first target nucleic acid are added to the third vial, and only primers for amplifying the positive control for the second target nucleic acid are added to the fourth vial. Primers for detecting other target nucleic acids are absent from these vials. It is understood that the same principle applies for third or fourth target nucleic acids and their respective positive control reactions. Thus, if a third target nucleic acid is amplified, it is amplified in the presence of specific primers for the third target nucleic acid and in the absence of primers specific for the first or second or any other different target nucleic acid. In a specific embodiment, primers used for one specific target nucleic acid are the same as the primers used for the corresponding positive control.
The positive controls are amplified in parallel. This means that they are amplified using the same thermal profile. In one embodiment, the first, second, third and fourth vials are vessels of one multiwell plate, and the thermoblock in which the multiwell plate is placed applies the same thermal profile to all of the vessels of the multiwell plate. Positive controls are used for ensuring the quality of amplification reagents and conditions during detection or quantitation of a target nucleic acid in a diagnostic assay.
In one specific embodiment, in a further step, the target nucleic acids and positive control nucleic acids are detected or quantitated.
The term “detecting” as used herein relates to a qualitative test aimed at assessing the presence or absence of a target nucleic acid in a sample. By way of example, detection may be by measuring a fluorescent dye associated with the target nucleic acid. Further, detection may be performed by the use of oligonucleotide probes.
The term “quantitating” as used herein relates to the determination of the amount or concentration of a target nucleic acid present in a sample. Quantitation is performed based on the amplification of internal standards of known concentration.
The term “amplifying” as used herein generally refers to the production of a plurality of nucleic acid molecules from a target nucleic acid wherein primers hybridize to specific sites on the target nucleic acid molecules in order to provide an initiation site for extension by a polymerase. Amplification can be carried out by any method generally known in the art, such as but not limited to: standard PCR, long PCR, hot start PCR, qPCR, RT-PCR and Isothermal Amplification. Other amplification reactions comprise, among others, the Ligase Chain Reaction, Polymerase Ligase Chain Reaction, Gap-LCR, Repair Chain Reaction, 3SR, NASBA, Strand Displacement Amplification (SDA), Transcription Mediated Amplification (TMA), and Oβ-amplification.
The term “different target nucleic acids” as used herein relates to different targets that are assayed. A target nucleic acid is a nucleic acid that may be present in a biological sample and that is targeted by the assay. Nucleic acids comprise RNA or DNA, double stranded or single stranded nucleic acids. In one embodiment, the nucleic acids may be human or animal or viral or microbial. The term “different target nucleic acids” as used herein, thus, relates to different targets that are assayed.
If two target nucleic acids are tested in separate vials, what is meant is that one target nucleic acid is tested in one vial but not the other and vice versa for the second target nucleic acid.
The term “vial” relates to a receptacle or tube or container or vessel for holding a liquid solution. Such vials include vials in which a reaction takes place. Such vials may also relate to vials in which solutions or mixtures for use in a reaction are stored before being transferred to a different vial in which the reaction takes place. In some embodiments, more than one vial are integrally formed. In one embodiment, vials in which a reaction takes place are vessels of a multiwell plate. In another embodiment, vials are individual vials which may comprise a penetrable cap and which are held in a rack.
The term “positive control nucleic acid” as used herein relates to a control nucleic acid which is a positive control for the respective target nucleic acid which, when amplified with the same primers and probes as the target nucleic acid result in a detectable signal indicating that the reaction mixture and amplification conditions permit amplification and detection of the target nucleic acid if present. As an non-limiting example, when a method is directed to quantitating HIV, the positive control nucleic acid comprises the HIV sequence and is packaged, e.g. as an armored particle. Armored particles are known in the art and mimic the envelope of HIV. Thus, the positive control nucleic acid serves as a positive control for the target nucleic acid. The positive control is generally amplified in parallel with the target nucleic acid in a separate vial.
The term “positive control vial” as used herein relates to the vial which comprises a single positive control stock solution which comprises a mixture of at least a first and a second positive control nucleic acid. The term “single positive control stock solution” means that the first and second positive control nucleic acids are present in a common positive control stock solution, not in two different individual positive control stock solutions.
The first positive control nucleic acid and the second positive control nucleic acid are, thus, provided to the third vial and the fourth vial from one single common positive control stock solution, e.g. by pipetting using a pipettor. Thus, for example only one positive control stock solution may be required for running different individual assays for different target nucleic acids, which simplifies the system.
In one specific embodiment, the method additionally comprises amplifying in parallel with a) and b) a negative control in a fifth vial, wherein the negative control is provided from a second single negative control stock solution comprised in a negative control vial.
The term “negative control” as used herein relates to a control in which target nucleic acids are absent. For example a purpose of the negative control may be to test if any reagents or the instrument parts of the analyzer in which the method may be performed are contaminated with target nucleic acid.
In one embodiment, the method is performed in an automated analyzer. When the method is performed in an automated analyzer, the method has the advantage that the number of positive control vials with different contents provided to the analyzer can be reduced. Thus, fewer vials have to be loaded, processed and identified in the analyzer.
A biological sample is provided in the method herein described by pipetting an aliquot of the biological sample into a vial. Target nucleic acids may be released from cells or viral particles by lysis. The target nucleic acid may then be enriched prior to amplification, e.g. by solid phase separation, e.g. using magnetic particles, and in the presence of a chaotropic compound. Alternatively, the target nucleic acid may be separated from other material by target capture using an oligonucleotide which specifically hybridizes to the target nucleic acid or to poly A, and which is coupled to a solid phase, e.g. a polymer material or a glass particle. Such methods are well known in the art. Following separation, the solid phase may be washed to remove inhibitors for the amplification reaction, and the bound nucleic acids may be eluted and then subjected to amplification. The positive controls and the negative controls may be exposed to the same lysis and enrichment steps as the nucleic acids to be tested.
The term “biological sample” relates to material that can be subjected to a diagnostic assay targeting nucleic acids and is usually derived from a biological source. In some embodiments, the biological sample is derived from a human and is a body liquid. In one embodiment of the invention, the biological sample is human blood, urine, sputum, sweat, swab, pipettable stool, or spinal fluid. The biological sample may also be a tissue from which target nucleic acids may be extracted.
A “target nucleic acid” is a polymeric compound of nucleotides as known to the expert skilled in the art. “Target nucleic acid” is used herein to denote a nucleic acid in a sample which should be analyzed, i.e. the presence, non-presence and/or amount thereof in a sample should be determined. The target nucleic acid may be a genomic sequence, e.g. part of a specific gene, DNA or RNA. In other embodiments, the target nucleic acid may be viral or microbial. In a specific embodiment, the target nucleic acids may be HIV, HCV and/or HBV.
The term “aliquot” as used herein relates to portions of a liquid which are employed for testing. Aliquots are typically generated by pipetting a portion of a liquid into a vial where then further treatment is conducted. When two or more aliquots of a liquid are needed it is for example possible to aspirate a volume of that liquid and to discharge portions of that volume into two or more wells. Alternatively, only the volume of a liquid intended for a single vial is dispensed at a time.
In one specific embodiment, the positive control vial is provided in a rack, and the negative control vial is provided in a second rack different from the rack comprising the positive control vial.
Positive control vials are provided to the analyzer by loading into the analyzer. The positive control vials are, thus, held in a rack when they are loaded into the analyzer. Loading positive control vials and negative control vials in separate racks has the advantage that negative controls can be run at a higher frequency than positive controls. This leads to higher efficiency of handling of racks holding positive or negative control vials. Thus, in one embodiment, in the rack comprising the positive control vial, a negative control vial is absent. In one embodiment, in the rack comprising a negative control vial, a positive control vial is absent. The absence of a negative control vial in a rack holding at least one positive control vial reduces the risk of contamination of the negative control vial.
In one embodiment, the rack comprising the positive control vial comprises at least two positive control vials, wherein all of the at least two positive control vials comprise an identical mixture of positive control nucleic acids. The term “identical” relates to the mixture of positive control nucleic acids comprising the same positive control nucleic acids, although one positive control vial may have a different concentration of the positive control nucleic acids than another positive control vial in the same rack. None of the positive control vials of this embodiment comprises a positive control nucleic acid that is not comprised in the other positive control vials of the same rack. By this, the complexity of the automated system is reduced as one rack only holds positive control vials which comprise the same positive control nucleic acids. Furthermore, this also reduces the risk of cross-contamination between vials comprising different mixtures of positive control nucleic acids.
In one embodiment, at least three different target nucleic acids are detected or quantitated, additionally comprising, in step a), amplifying a third target nucleic acid in a sixth vial without amplifying the first or second target nucleic acid, and, in step b), additionally amplifying a third positive control nucleic acid, wherein the third positive control nucleic acid is a positive control for the third target nucleic acid, wherein the third positive control nucleic acid is amplified in a seventh vial, wherein the first positive control nucleic acid, the second positive control nucleic acid and the third positive control nucleic acid are provided to the third vial, the fourth vial and the seventh vial from a positive control vial comprising a single positive control stock solution comprising a mixture of the first positive control nucleic acid, the second positive control nucleic acid and the third positive control nucleic acid before amplification. By this method, one mixture of controls can, thus, be used to perform positive control reactions for three different assays detecting or quantitating three different target nucleic acids, each individually in separate vials.
In one specific embodiment, all positive control vials comprised in the first rack comprise the positive control nucleic acids at a concentration of 1×10E5 to 1×10E8 copies/ml or of 1×10E2 to 5×10E3 copies/ml. The concentrations may also be provided in other units, such as IU/ml. The factors for converting copies/ml into IU per ml depend on the specific target and may range from 1.0 to 16. Thus, the rack comprises either positive control nucleic acid at the higher or positive control nucleic acids at the lower concentration. This reduces the risk of any cross-contamination between vials comprising positive control nucleic acid at the higher concentration and vials comprising positive control nucleic acid at the lower concentration, as specified herein. Vials with only positive control nucleic acids at the higher concentration described above are used for quantitative assays. The positive control mixtures can be used despite the fact that there are more non-amplified nucleic acids in the reaction mixtures which may affect the stringency of the reactions.
In the method hereinbefore described, the tests performed may be sorted into batches of assays which match the composition of the mixture of positive control nucleic acids in the vials of one rack.
The invention also relates to a rack comprising at least one high concentration positive control vial and/or at least one low concentration positive control vial, wherein the high concentration positive control vial comprises a mixture of at least two different positive control nucleic acids at a concentration of 1×10E5 to 1×10E8 copies/ml, and the low concentration positive control vial comprises a mixture of the same two different positive control nucleic acids at a concentration of 1×10E2 to 5×10E3 copies/ml. With this rack, a mixture of high positive control nucleic acids and/or low positive control nucleic acids can be provided to an automated analyzer for performing quantitative and/or qualitative assays of at least two different parameters in different vials. In one embodiment, one rack comprises an equal number of high positive control nucleic acids and low positive control nucleic acids. The term “high positive control nucleic acids” relates to positive control nucleic acids at a higher concentration as described herein, and “low positive control nucleic acid” relates to positive control nucleic acids at a lower concentration as described herein.
The invention further relates to a rack adapted to be loaded into an automated nucleic acid analyzer. The rack comprises at least two openings to receive at least two vials. The at least two vials are held in the openings of the rack. Each of the vials comprises a stock solution of a mixture of at least two positive control nucleic acids. The at least two positive control nucleic acids are for use as external positive controls in amplification reactions performed in the analyzer. The advantage is as described herein.
The invention also relates to a rack comprising at least two openings to receive at least two positive control vials. The at least two positive control vials are held in the openings of the rack. Each of the positive control vials comprises a stock solution of a mixture of at least two positive control nucleic acids. The at least two positive control nucleic acids are for use as external positive controls in amplification reactions performed in the analyzer. In one embodiment, the rack comprises at least two positive control vials held in openings of the rack, wherein at least one positive control vial is a high concentration positive control vial and one positive control vial is a low concentration positive control vial, wherein the high concentration positive control vial comprises a mixture of at least two different positive control nucleic acids at a concentration of 1×10E5 to 1×10E8 copies/ml, and the low concentration positive control vial comprises a mixture of the same two different positive control nucleic acids at a concentration of 1×10E2 to 5×10E3 copies/ml. The advantage is as described herein. In one embodiment, the rack comprises a cover which can be closed after the positive control vials have been received in the openings of the rack. In a further embodiment, the positive control vials comprise a lid. In a specific embodiment, the lid of the control vials comprises a frangible seal such as a foil.
A kit is also disclosed comprising a rack as described herein, wherein the rack comprises at least two positive control vials. The at least two positive control vials are held in the rack. Each of the positive control vials comprises a stock solution of a mixture of at least two positive control nucleic acids. The at least two positive control nucleic acids are for use as external positive controls in amplification reactions performed in the analyzer. The kit comprises a label, wherein the label indicates a single target nucleic acid to be detected with the kit components, wherein the target nucleic acid is one of the positive control nucleic acids in the positive control vials of the rack. The kit further comprises a master mix vial comprising a master mix comprising reagents for amplification of the target nucleic acid and the corresponding positive control nucleic acid. The kit does not comprise a master mix comprising reagents for amplification of target nucleic acids corresponding to the at least one positive control nucleic acid not corresponding to the target nucleic acid indicated on the label but present in the stock solution of the positive control vial. In one embodiment, the kit comprises a positive control vial with a high concentration of positive control nucleic acids, and a positive control vial with a low concentration of positive control nucleic acids as described herein. In one embodiment, the rack comprises at least two openings to receive at least two positive control vials.
The term “amplification reagents” as used herein relates to chemical or biochemical components that enable the amplification of nucleic acids. Such reagents may comprise, but are not limited to, nucleic acid polymerases, buffers, mononucleotides such as nucleoside triphosphates, oligonucleotides e.g. as oligonucleotide primers, salts and their respective solutions, detection probes, dyes, and more.
In one specific embodiment, the master mix comprises oligonucleotides which specifically hybridize to the target nucleic acid to be amplified by the reagents. For example the master mix may comprise oligonucleotide primers and a probe or multiple probes.
“Oligonucleotides” may include “modified oligonucleotides” (or “oligonucleotide analogs”). They are subgroups of oligomeric compounds. In the context of this invention, the term “oligonucleotide” refers to components formed from a plurality of nucleotides as their monomeric units. The phosphate groups are commonly referred to as forming the internucleoside backbone of the oligonucleotide. The normal linkage or backbone of RNA and DNA is a 3′ to 5′ phosphodiester linkage. Oligonucleotides and modified oligonucleotides (see below) useful for the invention may be synthesized as principally described in the art and known to the expert in the field. Methods for preparing oligomeric compounds of specific sequences are known in the art, and include, for example, cloning and restriction of appropriate sequences and direct chemical synthesis. Chemical synthesis methods may include, for example, the phosphotriester method described by Narang S. A. et al., Methods in Enzymology 68 (1979) 90-98, the phosphodiester method disclosed by Brown E. L., et al., Methods in Enzymology 68 (1979) 109-151, the phosphoramidite method disclosed in Beaucage et al., Tetrahedron Letters 22 (1981) 1859, the H-phosphonate method disclosed in Garegg et al., Chem. Scr. 25 (1985) 280-282 and the solid support method disclosed in U.S. Pat. No. 4,458,066.
In the method according to the invention, the oligonucleotides may be chemically modified, i.e. the primer and/or the probe comprise a modified nucleotide or a non-nucleotide compound. The probe or the primer is then a modified oligonucleotide.
In another embodiment, a kit comprises a rack with at least two positive control vials, wherein each of the positive control vials comprises a stock solution of a mixture of at least two positive control nucleic acids; a label indicating all target nucleic acid for which the corresponding positive control nucleic acids are present in the stock solution. The label also indicates that the rack comprising the stock solutions of positive control nucleic acids is for use in methods for detecting one of the target nucleic acids, but not the other target nucleic acids for which the corresponding positive control nucleic acids are comprised in the stock solution, in a single vial. In one embodiment, the kit comprises a positive control vial with a high concentration of positive control nucleic acids, and a positive control vial with a low concentration of positive control nucleic acids as described herein. In one embodiment, the rack at least two openings to receive at least two positive control vials.
The term “label” relates to any type of label that can be fixed or attached to the kit and/or rack and/or positive control vials. The label may comprise a side on which information is imprinted in an operator readable manner, and a second side which comprises glue for attachment to kit, rack and/or positive control vials.
In one specific embodiment, negative control vials comprising a negative control solution are absent from the rack. The absence of a negative control vial in a rack holding at least one positive control vial reduces the risk of contamination of the negative control vial.
In one embodiment of the rack herein described, no negative control vial comprising a solution in which nucleic acids are absent is held in any one of the openings of the rack. The advantage is as described herein.
Also disclosed is an analytical system for detecting or quantitating at least two different target nucleic acids in separate vials. The analytical system comprises vials for target nucleic acid detection, positive control and negative control detection. In one embodiment, the vials are integrally formed. A specific embodiment of vials for amplification is vessels of a multiwell plate. The method herein described can be performed on the analytical system. In one specific embodiment, the analytical system comprises a rack comprising positive control vials as described herein. In a specific embodiment, the analytical system further comprises a rack comprising negative control vials as described herein. Specific embodiments of the components of the analytical system are described herein. Specific embodiments of the rack are also as described herein.
In one specific embodiment, the analytical system comprises a loading station to load the rack into the analytical system, and a pipetting station for transferring aliquots of the stock solution of positive control nucleic acids in the positive control vials held in the rack from the positive control vials to vials for amplification of a target nucleic acid. In one specific embodiment, the analytical system further comprises a station for isolating nucleic acids. In a further specific embodiment, the analytical system comprises a station for amplifying and/or detecting target nucleic acids.
A loading station relates to a station into which the rack comprising positive control vials can be loaded either manually or automatically, and from which the rack can be transferred to the pipetting station within the analytical system.
A pipetting station relates to a station comprising a pipetting device. A pipetting device can aspirate a liquid from a vial, e.g. a positive control vial and can dispense the liquid into a different vial.
A station for isolating nucleic acids relates to a station which can separate a nucleic acid from other materials comprised in a biological sample in which the nucleic acid is to be detected or quantitated. Non-limiting examples for such stations for isolating nucleic acids are magnetic separation stations in which the nucleic acids are bound to a solid support such as a magnetic particle, and separated from other material in the biological sample by applying a magnetic field. The bound nucleic acid may be washed to remove inhibitors of amplification. The nucleic acid may be either eluted from the solid support before amplification, or amplified in the presence of the solid support.
A station for amplifying and/or detecting nucleic acids relates, in one embodiment, an incubator in which the target nucleic acid is amplified. The incubator may be an incubator held at a uniform temperature in case an isothermal amplification method is used, or a thermocycler. In one embodiment, the station for amplifying nucleic acids also includes a station for detecting the amplified nucleic acids. As a non-limiting example, such a station may be a real-time PCR thermocycler or an isothermal incubator with a built in detection module. In a further embodiment, the analytical system comprises a separate detection station in which the amplified target nucleic acid is detected.
The analytical system, in one specific embodiment, also includes a computer controller adapted to determine the presence or absence of the target nucleic acid. In a specific embodiment, the computer controller is adapted to quantitate the target nucleic acid based on the fluorescence signal detected during or following amplification of the target nucleic acid and the internal standard. Furthermore, the computer controller is adapted to determine the quality of the amplification reagents and amplification conditions for amplification of the target nucleic acid based on the detection of the positive control nucleic acid for the target nucleic acid.
In one embodiment, the rack is used in the method described herein. The rack may also be used in an automated analyzer as described herein.
The present invention also relates to a use of a mixture of at least a first positive control nucleic acid and a second positive control nucleic acid in separate positive control reactions, wherein the first control nucleic acid is amplified in the absence of amplification of the second positive control nucleic acid, and the second positive control nucleic acid is amplified in the absence of amplification of the first control nucleic acid. By this, separate positive control reactions for individual targets can be based on a single positive control stock solution.
In one embodiment, the mixture is used in the method described herein. In one specific embodiment, the mixture is a high concentration mixture or a low concentration mixture. Embodiments of high and low concentration mixtures are described hereinbefore. In one embodiment, a high concentration mixture and a low concentration mixture are used in parallel. Thus, one single mixture can be used for quantitative assays and/or for qualitative assays of different target nucleic acids in parallel.
It is understood that the examples and embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the claimed invention.
Sample Preparation
This example describes a process for isolating and simultaneously amplifying a first, a second and a third target nucleic acid in separate vials using a single positive control stock solution comprising a mixture of HIV, HBV and HCV. The same positive control stock solution was evaluated in three individual runs with the respective assay for individually quantitating HIV, HBV or HCV.
In brief, in the depicted embodiment, sample preparation and realtime PCR is carried out simultaneously under identical conditions on the positive control stock solution comprising HIV target RNA, HCV target RNA and HBV target DNA. The following positive control stock solution and negative control stock solution were analysed (HPC: High concentration positive control; LPC: Low concentration positive control):
Each respective sample (200 ul) was pipetted manually into a deep well plate. To each well 50 ul of an internal quantitation standard was manually added. For the HIV and HCV assay, an RNA serving as a quantitative control was added (6×E4 armoured particles/sample). For the quantitative HBV assay, a DNA serving as a quantitative standard was added (1×E4 lambda particles/sample). The sequence of the standard nucleic acid was identical in all cases. Suitable sequences for detecting HIV, HCV and HBV as well as sequences for a standard and for detecting the standard are disclosed in EP2426222. The same standard can be used both for qualitative and for quantitative determinations.
Sample preparation was performed following the workflow according to the scheme depicted in
Amplification and Detection
After the final sample preparation step of each run, the fluids containing the isolated nucleic acids were transferred to a corresponding well of a microwell plate for carrying out amplification, and the isolated nucleic acids were mixed with the respective master mixes R1 and R2 containing amplification reagents.
For amplification and detection, the microwell plate was sealed with an automated plate sealer, and the plate was transferred to an Analytical Cycler.
The following thermocycling profile was used for all assays:
The Pre-PCR program comprises initial denaturing at 94° C. and incubation at 55° C., 60° C. and 65° C. for reverse transcription of RNA templates. Incubating at three temperatures combines the advantageous effects that at lower temperatures slightly mismatched target sequences (such as genetic variants of an organism) are also transcribed, while at higher temperatures the formation of RNA secondary structures is suppressed, thus leading to a more efficient transcription.
PCR cycling is divided into two measurements, wherein both measurements apply a one-step setup (combining annealing and extension). The first 5 cycles at 55° C. allow for an increased inclusivity by pre-amplifying slightly mismatched target sequences, whereas the 45 cycles of the second measurement provide for an increased specificity by using an annealing/extension temperature of 58° C.
Using this profile on all assays mentioned above, amplification and detection was achieved for all assays and samples.
The following table 4 shows the results of H×V LPC and H×V HPC sample preparation and amplification along with the quantitation standard. It can be seen that H×V LPC and H×V HPC were successfully amplified in all cases and successfully quantitated using the quantitation standard.
It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. All publications, sequence accession numbers, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes.
| Number | Date | Country | Kind |
|---|---|---|---|
| 12166266.2 | May 2012 | EP | regional |
