Strauss, W. an active immune response. In this case, having an array of alphavirus-based vectors with comparable cell tropisms would be highly advantageous. These vectors may also be useful in diagnostic assays in which infectious VEEV is usually undesirable but immune reactivity to native epitopes is required. The production of novel pseudotyped vectors is particularly useful for the growth of tissue types that can potentially be targeted by virus-based gene therapy vectors (29). Retroviral vectors permit the efficient transduction of a broad array of cell Etidronate Disodium types. Originally, retroviral vectors based on murine oncoretroviruses were used in a number of human gene therapy trials with some success (6). These vectors have the disadvantage that they require actively dividing cells for efficient transduction. Lentiviral vectors have been developed to overcome this limitation and can efficiently deliver genes Etidronate Disodium to nondividing cells. For each vector, the outcome of infection is the same: a packaged gene becomes permanently integrated into the host genome. In the case of gene therapy, the gene may be corrective or may encode a dominant negative factor to down regulate specific genes and cellular pathways. The cell tropism of these retroviral vectors is usually predominantly defined by Rabbit Polyclonal to SRY the envelope proteins that coat the particle. Both discrete and broad-specificity vectors have their advantages. The first broad-specificity vector utilized the amphotropic murine leukemia computer virus (MLV) envelope protein. Later, however, it was shown that MLV vectors could be efficiently pseudotyped with vesicular stomatitis computer virus (VSV) envelope proteins (4). These chimeric particles comprised the core of an MLV, coated with the foreign envelope protein. Even though VSV G protein (VSV-G) provides high titers, typically exceeding 106 to 107 CFU/ml, its use has been problematic due to significant cell toxicity and neutralization by human match. Recently, other novel, broad-specificity pseudotypes have been produced. These include pseudotypes of lymphocytic choriomeningitis computer virus (LCMV), Ebola computer virus, and a number of alphaviruses, namely, Semliki Forest computer virus (SFV), Sindbis computer virus (SINV), and Ross River computer virus (RRV). Pseudotypes of Ebola computer virus (36) and SFV (11) yielded low-titer viruses that reach only 103 to 104 CFU/ml, but LCMV (1), RRV (30), and SINV (21) have been more encouraging, with 10- to 100-fold-higher titers with murine oncoretroviral vectors. In the case of SINV, targeting specificity could be enhanced by insertion of the Fc-binding portion of protein A and by the binding of specific antibodies, a property that other alphaviruses may also permit. More recently, RRV envelope lentiviral pseudotypes have been made and applied in a mouse model to show efficient gene transduction of tissues (12). The potential of alphavirus envelope proteins to be efficiently incorporated into both oncoretroviral and lentiviral vectors and transduce many tissue types is particularly useful. Venezuelan equine encephalitis computer virus (VEEV) is usually a distant relative of SINV, RRV, and SFV and is a representative of the New World alphaviruses. It is an arbovirus that is normally maintained in a silent enzootic cycle between mosquitoes of (and other mosquitoes (34). Humans succumb to Etidronate Disodium a debilitating acute febrile illness with rapid onset, typically lasting up to 2 weeks. It is recognized as a significant and emerging health threat in North America and also as a potential biological weapon. Like other alphaviruses, VEEV has broad cell tropism in infected animals and in tissue culture. However, unlike the other alphaviruses that have been used to produce pseudotypes, which produce an arthralgia syndrome, VEEV is usually lymphotropic and also causes acute encephalitis, presumably because this computer virus has greater tropism for the brain. Indeed, in mice, infectious computer virus can be recovered from the brain as well as from blood, the lungs, and the spleen (24). However, disease is thought to Etidronate Disodium be a product of replication and not directly due to action of the viral envelope proteins. The broad specificity of the VEEV envelope protein, the potential to access novel tissues from organs such as the brain and lungs, and the lack of antigenic.