Method for nucleic acid detection via Qbeta replicase

A method of assaying for a target nucleic acid, comprising the steps of:

• (a) combining a first amplification probe and second amplification probe with a nucleic acid sample under conditions suitable for hybridization, the nucleic acid sample comprising a target sequence having a complementary antitarget sequence, the first amplification probe comprising a first antitarget sequence segment capable of hybridizing to a portion of the target sequence and a first partial replicable sequence, the second probe comprising a second antitarget sequence segment which is capable of hybridizing to a portion of the target segment and a second partial replicable sequence, such that the first and second antitarget sequence segments hybridize to the target sequence to form a hybridized complex, such that the first and second partial replicable sequences together in the hybridized complex have the sequence, or a complementary sequence, of an quasi-autocatalytically replicable sequence;
• (b) subjecting the hybridized complex to conditions suitable for activity of the replicase to cause quasi-autocatalytic replication of both the first and second partial replicable sequences and the first and second antitarget sequence segments;
• (c) detecting amplified levels of at least one of the replicated first and second antitarget sequence segments.

A method of assaying for a target nucleic acid, comprising the steps of:

• (a) combining a complete amplification probe with a nucleic acid sample under conditions suitable for hybridization, the nucleic acid sample comprising a target sequence, the complete amplification probe comprising an antitarget sequence which is capable of hybridizing to a portion of the target sequence and a replicable sequence or a complementary sequence thereto, whereby the antitarget sequence hybridizes to the target sequence, such that the replicable sequence comprises a nucleic acid sequence which is quasi-autocatalytically replicable;
• (b) subjecting the amplifiable segments to conditions effective for catalysis with the replicase resulting in quasi-autocatalytic replication of both the amplifiable sequence and the antitarget sequence;
• (c) detecting the presence of the replicated antitarget sequence.

A method of increasing the signal to noise ratio for detecting a target sequence obtainable from a first detection probe that hybridizes to a first target sequence segment comprising employing a second detection probe that hybridizes to a second target sequence segment,

• wherein the second target sequence segment does not overlap in sequence with the first target sequence segment, both the first target sequence segment and the second target sequence segment residing in a region comprising thee target sequence and the signal to noise ratio for detection of the target from the first detection probe taken alone is enhanced by the presence of the second detection probe.