Cells were cultured overnight and then treated with compound and IFN-b for 6 h. Thereafter, cells were washed and then were inoculated with EMCV (strain VR-129B, ATCC, Manassas, VA) for 1 h at MOI 1 as described previously [13] . Cells were then washed twice and cultured in medium containing 2% fetal bovine serum for 28 h. At that time, cell supernatants were used to determine viral titer based on real-time quantitative PCR assay for EMCV RNA with 59-ctgccttcggtgtcgc-39 (forward primer), 59tgggtcgaatcaaagttggag-39 (reverse primer), and 59caaggttttgagcgtgtctacgatgtgg-39 (probe). A TA plasmid containing the EMCV 3D protein was used as a standard for absolute quantitation of viral copy number. In addition, cell viability was determined using the Cellomics Arrayscan VTi high content imager (Thermo Scientific). For this assay, 15 images per well were obtained with a 10x objective. After background subtraction, cells were identified by nuclei stained by cell permeable dye Hoechst 33342. Propidium iodide fluorescence was quantified by defining a boundary of 2 pixels around the nuclei and then gating on a cell population that showed higher staining. For each sample replicate, cytotoxicity was calculated as the percentage of cells that showed increased propidium iodide staining based on samples of at least 5000 cells per well.  Feline Immunodeficiency Virus in South America The rapid emergence of AIDS in humans during the period between 1980 and 2000 has led to extensive efforts to understand more fully similar etiologic agents of chronic and progressive acquired immunodeficiency disease in several mammalian species. Lentiviruses that have gene sequence homology with human immunodeficiency virus (HIV) have been found in different species (including sheep, goats, horses, cattle, cats, and several Old World monkey species). Lentiviruses, comprising a genus of the Retroviridae family, cause persistent infection that can lead to varying degrees of morbidity and mortality depending on the virus and the host species involved. Feline immunodeficiency virus (FIV) causes an immune system disease in domestic cats (Felis catus) involving depletion of the CD4+ population of T lymphocytes, increased susceptibility to opportunistic infections, and sometimes death. Viruses related to domestic cat FIV occur also in a variety of nondomestic felids. This is a brief overview of the current state of knowledge of this large and ancient group of viruses (FIVs) in South America. Feline immunodeficiency virus (FIV) is a Lentivirus, closely related to HIV and SIV, which infects members of Felidae family. FIV is an important viral pathogen worldwide in the domestic cat (Felis catus), causes a slow progressive degeneration of immune functions that eventually leads to a disease. FIV is unique among the nonprimate lentiviruses because in its natural host species it induces a disease similar to AIDS in humans infected with human immunodeficiency virus type 1 (HIV-1), characterized by a progressive depletion of CD4 + T lymphocytes [5, 28, 35, 48, 77] . Species-specific strains, related to domestic cat FIV, have been isolated from a variety of nondomestic Felidae [11, 43] . Like HIV, FIV can be transmitted via mucosal exposure, blood transfer, and vertically either prenatally or postnatally [26] . For these reasons, FIV has been studied widely as both an important veterinary pathogen and an animal model for HIV/AIDS. Although FIV was first recognized in 1993 in Brazil [23] and in 1994 in Argentina [65] , there are few data describing the prevalence, ecology, clinical aspects, or genetic analyses of FIV in South America ( Figure 1 ). The prevalence of FIV within the continent is summarized in Table 1 . A better characterization of FIV strains circulating within South America will be required to augment our understanding of the importance of this lentivirus in felids. This paper provides an overview of the current state of knowledge of this large and ancient group of viruses (FIVs) in South America, grouped according to domestic and nondomestic felids. The data obtained allow a better understanding on FIV epidemiology and distribution. Efforts were made to gather and review all of the available information for each country. 