The circumstances under which unintegrated lentivirus DNA can persist and be a functional template for transcription and protein expression are not clear. We constructed and validated the first class I (nonpleiotropic) integrase (IN) mutants for a non-human lentivirus (feline immunodeficiency virus [FIV]) and analyzed both these and known class I human immunodeficiency virus type 1 IN mutants. The FIV IN mutants (D66V and D66V/D118A) had class I properties: Gag/Pol precursor expression, proteolytic processing, particle formation, and reverse transcriptase (RT) production were normal, while the transduction of dividing fibroblasts was prevented and integration was blocked. When injected into rat retinas, the wild-type ( Shortly after infection of a cell by a retrovirus, reverse transcription of the RNA genome yields a linear cDNA copy, which along with the viral integrase (IN) and other proteins comprises the preintegration complex (PIC), the functional precursor to integration (5). Certain features of the IN structure are conserved among retroelements, and conserved amino acid residues that are critical for catalysis have been identified. Retroviral INs have three domains: an N-terminal domain, a central catalytic core domain, and a C-terminal domain (26). The N-terminal domain contains a zinc finger-like sequence that influences IN oligomerization (9). The C-terminal domain, which is the most divergent, binds DNA in a sequenceindependent manner (20, 58). IN has also been reported to play other roles in the lentiviral life cycle, in particular in nuclear import of the PIC (23).The genetic analysis of IN functions is not straightforward because the enzyme is generated by viral protease-mediated cleavage from the Gag/Pol precursor. Many IN mutations produce pleiotropic effects on Gag/Pol-derived functions, including particle formation and reverse transcription (17). Accordingly, two types of IN mutants are generally recognized. Nonspecific phenotypes (which have been termed class II) result from deletions, truncations, and numerous single amino acid changes (17,19,56). In contrast, nonpleiotropic (class I) mutations affect only the DNA cleaving and joining reaction, while leaving intact other measurable aspects of the virus life cycle, such as Gag/Pol precursor processing, particle formation, virion morphogenesis, reverse transcription, and PIC nuclear import (17,18,28,29). In human immunodeficiency virus type 1 (HIV-1), mutations of any of three residues that participate in the catalytic center (D64, D116, and E152) produce class I properties (15,18,29). These residues form a catalytic triad (DX 39-58 DX 35 E) that is broadly conserved in retroelement INs (5,17). Experimentally, class I IN mutants enable control designs that compare the fates of integration-defective, structurally normal particles differing in only one amino acid in a single enzyme that comprises a very small molar fraction of virion protein molecules (17).

We injected lentiviral vectors into the eyes of live nonhuman primates to assess potential for glaucoma gene therapy. Anterior chambers of five cynomolgus monkeys were injected with green fluorescent protein (GFP)-encoding feline immunodeficiency viral vectors. The monkeys were monitored for in vivo transgene expression and clinical parameters. Their eyes were harvested 2-15 months postinjection for tissue analyses. All seven eyes injected with 1.0-2.0 x 10(8) transducing units (TU) showed substantial GFP fluorescence in the trabecular meshwork (TM), which was observable even by goniophotographic monitoring for up to 15 months. Only the lowest dose (0.03 x 10(8) TU) failed to result in TM fluorescence detectable in vivo, and five of the eight vector-injected eyes continued to display substantial GFP expression when enucleated eyes were examined at 2, 7, or 15 months postinjection. Some transduced cells were also detected in the iris and ciliary body. Mild, transient postinjection inflammatory responses exceeding that induced by a control saline injection were observed, but vectors did not raise intraocular pressure and were well tolerated. The results demonstrate the first lentiviral vector transduction of the nonhuman primate aqueous humor outflow pathway and support application of the system to human glaucoma gene therapy.

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Cyclooxygenase-2 (COX-2) is a rate-limiting enzyme in prostaglandin (PG) biosynthesis. In the eye, loss of COX-2 expression in aqueous humor-secreting cells has been associated with primary open-angle glaucoma (POAG). Reduction of intraocular pressure (IOP) is the main treatment goal in this disease. We used lentiviral vectors to stably express COX-2 and other PG biosynthesis and response transgenes in the ciliary body epithelium and trabecular meshwork (TM), the ocular suborgans that produce aqueous humor and regulate its outflow, respectively. We show that robust ectopic COX-2 expression and PG production require COX-2 complementary DNA (cDNA) sequence optimization. When COX-2 expression was coupled with a similarly optimized synthetic PGF2alpha receptor transgene to enable downstream signaling, gene therapy produced substantial and sustained reductions in IOP in a large animal model, the domestic cat. This study provides the first gene therapy for correcting the main cause of glaucoma.

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