Small ruminant lentivirus Tat protein induces apoptosis in caprine cells in vitro by the intrinsic pathway

Caprine arthritis encephalitis virus-induced apoptosis associated with brain lesions in naturally infected kids

Acute demyelinating leucoencephalomyelitis was the most conspicuous microscopic change in the brain and spinal cord of kids infected with caprine arthritis encephalitis virus (CAEV). TUNEL positivity and labelling of anti-bax and anti-caspases-3, -8 and -9 were found in a distinct population of glial cells, mainly at the edges of the demyelinated plaques and perivascular areas and, to a lesser extent, in neurons. Double labelling revealed that most of these apoptotic cells in the demyelinated plaques were astrocytes and a few were oligodendroglia. In contrast, expression of bcl-2, an anti-apoptotic protein, was found mainly in neurons of the brainstem and cerebellum and motor neurons of the spinal cord, but was restricted in glial cells. These results suggest that apoptosis plays an important role in the pathogenesis of CAE demyelinating encephalitis.

Comparative Analysis of Tat-Dependent and Tat-Deficient Natural Lentiviruses

The emergence of human immunodeficiency virus (HIV) causing acquired immunodeficiency syndrome (AIDS) in infected humans has resulted in a global pandemic that has killed millions. HIV-1 and HIV-2 belong to the lentivirus genus of the Retroviridae family. This genus also includes viruses that infect other vertebrate animals, among them caprine arthritis-encephalitis virus (CAEV) and Maedi-Visna virus (MVV), the prototypes of a heterogeneous group of viruses known as small ruminant lentiviruses (SRLVs), affecting both goat and sheep worldwide. Despite their long host-SRLV natural history, SRLVs were never found to be responsible for immunodeficiency in contrast to primate lentiviruses. SRLVs only replicate productively in monocytes/macrophages in infected animals but not in CD4+ T cells. The focus of this review is to examine and compare the biological and pathological properties of SRLVs as prototypic Tat-independent lentiviruses with HIV-1 as prototypic Tat-dependent lentiviruses. Results from this analysis will help to improve the understanding of why and how these two prototypic lentiviruses evolved in opposite directions in term of virulence and pathogenicity. Results may also help develop new strategies based on the attenuation of SRLVs to control the highly pathogenic HIV-1 in humans.