Jean Gagnon

Animal lentiviruses (LVs) have been proven to have the capacity to cross the species barrier, to adapt in the new hosts, and to increase their pathogenesis, therefore leading to the emergence of threatening diseases. However, their potential for widespread diffusion is limited by restrictive cellular factors that block viral replication in the cells of many species. In previous studies, we demonstrated that the restriction of CAEV infection of sheep choroid plexus cells was due to aberrant post-translation cleavage of the CAEV Env gp170 precursor. Later, we showed that the lack of specific receptor(s) for caprine encephalitis arthritis virus (CAEV) on the surface of human cells was the only barrier to their infection. Here, we examined whether small ruminant (SR) cells can support the replication of primate LVs. Three sheep and goat cell lines were inoculated with cell-free HIV-1 and SIVmac viral stocks or transfected with infectious molecular clone DNAs of these viruses. The two recombinant lentiviral clones contained the green fluorescent protein (GFP) reporter sequence. Infection was detected by GFP expression in target cells, and the infectious virus produced and released in the culture medium of treated cells was detected using the indicator TZM-bl cell line. Pseudotyped HIV-GFP and SIV-GFP with vesicular stomatitis virus G glycoprotein (VSV-G) allowed the cell receptors to be overcome for virus entry to further evaluate the viral replication/restriction in SR cells. As expected, neither HIV nor SIV viruses infected any of the SR cells. In contrast, the transfection of plasmid DNAs of the infectious molecular clones of both viruses in SR cells produced high titers of infectious viruses for human indicators, but not SR cell lines. Surprisingly, SR cells inoculated with HIV-GFP/VSV-G, but not SIV-GFP/VSV-G, expressed the GFP and produced a virus that efficiently infected the human indictor, but not the SR cells. Collectively, these data provide a demonstration of the lack of replication of the SIVmac genome in SR cells, while, in contrast, there was no restriction on the replication of the IV-1 genome in these cells. However, because of the lack of functional receptors to SIVmac and HIV-1 at the surface of SR cells, there is specific lentiviral entry.

HIV-1 remains a major public health issue worldwide in spite of efficacious antiviral therapies, but with no cure or preventive vaccine. The latter has been very challenging, as virus infection is associated with numerous escape mechanisms from host specific immunity and the correlates of protection remain incompletely understood. We have developed an innovative vaccine strategy, inspired by the efficacy of live-attenuated virus, but with the safety of a DNA vaccine, to confer both cellular and humoral responses. The CAL-SHIV-IN⁻ lentiDNA vaccine comprises the backbone of the pathogenic SHIV_KU2 genome, able to mimic the early phase of viral infection, but with a deleted integrase gene to ensure safety precluding integration within the host genome. This vaccine prototype, constitutively expressing viral antigen under the CAEV LTR promoter, elicited a variety of vaccine-specific, persistent CD4 and CD8 T cells against SIV-Gag and Nef up to 80 weeks post-immunization in cynomolgus macaques. Furthermore, these specific responses led to antiviral control of the pathogenic SIV_mac251. To further improve the efficacy of this vaccine, we incorporated the IL-7 or IL-15 genes into the CAL-SHIV-IN⁻ plasmid DNA in efforts to increase the pool of vaccine-specific memory T cells. In this study, we examined the immunogenicity of the two co-injected lentiDNA vaccines CAL-SHIV-IN⁻ IRES IL-7 and CAL-SHIV-IN⁻ IRES IL-15 in BALB/cJ mice and rhesus macaques and compared the immune responses with those generated by the parental vaccine CAL-SHIV-IN⁻. This co-immunization elicited potent vaccine-specific CD4 and CD8 T cells both in mice and rhesus macaques. Antibody-dependent cell-mediated cytotoxicity (ADCC) antibodies were detected up to 40 weeks post-immunization in both plasma and mucosal compartments of rhesus macaques and were enhanced by the cytokines.

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.

We investigated whether dairy beef cattle raised in Algeria are Shiga toxin-producing Escherichia coli (STEC) carriers. Stx1 and stx2 genes were analysed in DNA isolated from 200 faecal samples collected from adult dairy cows from 27 randomly selected farms in Blida, North Algeria, after amplification by PCR. Samples from 61 (30.5%) animals out of the 200 were positive and were located in 18 farms with a prevalence of 66.7%. Interestingly, no sample from any cow was positive for only the stx2 gene, while in contrast, samples from 51 cows were positive for the stx1 gene alone (83.6%) and those from 10 other cows were positive for both stx1 and stx2 genes (16.4%). It should be noted that the faecal samples infected with pathogens carrying the two genes originated from 4 out of the 18 farms that were found to be positive, with a rate of 22.2%.

Mutations within the central region of prion protein (PrP) have been shown to be associated with severe neurotoxic activity similar to that observed with Dpl, a PrP-like protein. To further investigate this neurotoxic effect, we generated lines of transgenic (Tg) mice expressing three different chimeric PrP-Dpl proteins. Chi1 (amino acids 1–57 of Dpl replaced by amino acids 1–125 of PrP) and Chi2 (amino acids 1–66 of Dpl replaced by amino acids 1–134 of PrP) abrogated the pathogenicity of Dpl indicating that the presence of a N-terminal domain of PrP (23–134) reduced the toxicity of Dpl, as reported. However, when the amino acids 1–24 of Dpl were replaced by amino acids 1–124 of PrP, Chi3 Tg mice, which express the chimeric protein at a very low level, start developing ataxia at the age of 5–7 weeks. This phenotype was not counteracted by a single copy of full-length-PrP^cbut rather by its overexpression, indicating the strong toxicity of the chimeric protein Chi3. Chi3 Tg mice exhibit severe cerebellar atrophy with a significant loss of granule cells. We concluded that aa25 to aa57 of Dpl, which are not present in Chi1 and Chi2 constructs, confer toxicity to the protein. We tested this possibility by using the 25–57 Dpl peptide in primary culture of mouse embryo cortical neurons and found a significant neurotoxic effect. This finding identifies a protein domain that plays a role in mediating Dpl-related toxicity.