Abstract: The present invention is directed to improved helper vectors and cell lines for the production of pseudoadenoviral (PAV) vectors containing substantially reduced levels of contaminating helper vector. The invention provides for helper vectors for the production of substantially helper vector-free PAV stocks comprising phag C31 recombinase recognition sequences which, depending upon their arrangement within the helper vector, can prevent helper vector packaging. The invention also provides for improved cell lines for the production of substantially helper vector-free PAV stocks comprising a stably introduced novel circular PAV genome into the cell.

Abstract: The present invention relates to transgene expression systems, related compositions comprising the transgene expression systems, and methods of making and using them. Preferred systems employ an adenovirus transgene expression vector comprising DNA encoding a transgene which codes for a desired product operably linked to expression control sequence, and at least a portion of the adenovirus E3 region and certain portions of the E4 region. The E4 portions comprise the open reading frame sequence known as E40RF3 and at least one other portion of E4. Preferably the E4 portion of the vector (or “E4 cassette”) includes E40RF3 and at least one other portion selected from E40RF4, E40RF6/7 and E40RF3/4. The invention has a number of important features including improving persistency of transgene expression in a desired host cell.

Abstract: The invention relates to a method for determining homocysteine concentration in samples in which homocysteine is condensed using an enzyme cystathionine &bgr; sythase to form cystathionine. Pyruvate and/or ammonia are released from cystathionine by action of an enzyme, cystathionine &bgr; lyase, and homocysteine is regenerated. The release of pyruvate and/or ammonia can be correlated to the concentration of homocysteine present in the sample.