Jack Alden

National Institute for Biological Standards and Control, Potters Bar, England, United Kingdom

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Publications (3)8.96 Total impact

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    ABSTRACT: Vaccination with live attenuated SIV in non-human primate species provides a means of characterising the protective processes of retroviral superinfection and may lead to novel advances of HIV/AIDS vaccine design. The minimally attenuated SIVmacC8 vaccine has been demonstrated to elicit early potent protection against pathogenic re-challenge with genetically diverse viral isolates in cynomolgus macaques (Macaca fascicularis). In this study, we have characterised further the biological breadth of this vaccine protection by assessing the ability of both the nef-disrupted SIVmacC8 and its nef-intact counterpart SIVmacJ5 viruses to prevent superinfection with the macrophage/neurotropic SIVmac239/17E-Fr (SIVmac17E-Fr) isolate. Inoculation with either SIVmacC8 or SIVmacJ5 and subsequent detailed characterisation of the viral replication kinetics revealed a wide range of virus-host outcomes. Both nef-disrupted and nef-intact immunising viruses were able to prevent establishment of SIVmac17E-Fr in peripheral blood and secondary lymphoid tissues. Differences in virus kinetics, indicative of an active process, identified uncontrolled replication in one macaque which although able to prevent SIVmac17E-Fr superinfection led to extensive neuropathological complications. The ability to prevent a biologically heterologous, CD4-independent/CCR5+ viral isolate and the macrophage-tropic SIVmac316 strain from establishing infection support the hypothesis that direct target cell blocking is unlikely to be a central feature of live lentivirus vaccination. These data provide further evidence to demonstrate that inoculation of a live retroviral vaccine can deliver broad spectrum protection, against both macrophage-tropic as well as lymphocytotropic viruses. These data add to our knowledge of live attenuated SIV vaccines but further highlight potential safety concerns of vaccinating with a live retrovirus.
    Journal of General Virology 04/2015; 96(7). DOI:10.1099/vir.0.000135 · 3.18 Impact Factor
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    ABSTRACT: The neuropathology of simian immunodeficiency (SIV) infection in cynomolgus macaques (Macaca fascicularis) was investigated following infection with either T cell tropic SIVmacJ5, SIVmacC8 or macrophage tropic SIVmac17E-Fr. Formalin fixed, paraffin embedded brain tissue sections were analysed using a combination of in situ techniques. Macaques infected with either wild-type SIVmacJ5 or neurovirulent SIVmac17E-Fr showed evidence of neuronal dephosphorylation, loss of oligodendrocyte and CCR5 staining, lack of microglial MHC II expression, infiltration by CD4⁺ and CD8⁺ T cells and mild astrocytosis. SIVmacJ5-infected animals exhibited activation of microglia whilst those infected with SIVmac17E-Fr demonstrated a loss of microglia staining. These results are suggestive of impaired central nervous system (CNS) physiology. Furthermore, infiltration by T cells into the brain parenchyma indicated disruption of the blood brain barrier (BBB). Animals infected with the Δnef-attenuated SIVmacC8 showed microglial activation and astrogliosis indicative of an inflammatory response, lack of MHC II and CCR5 staining and infiltration by CD8⁺ T cells. These results demonstrate that the SIV infection of cynomolgus macaque can be used as a model to replicate the range of CNS pathologies observed following HIV infection of humans and to investigate the pathogenesis of HIV associated neuropathology.
    Journal of NeuroVirology 03/2012; 18(2):100-12. DOI:10.1007/s13365-012-0084-3 · 2.60 Impact Factor
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    ABSTRACT: Vaccination with live attenuated simian immunodeficiency virus (SIVmacC8) confers potent, reproducible protection against homologous wild-type virus challenge (SIVmacJ5). The ability of SIVmacC8 to confer resistance to superinfection with an uncloned ex vivo derivative of SIVmac251 (SIVmac32H/L28) was investigated. In naïve, Mauritian-derived cynomolgus macaques (Macaca fascicularis), SIVmac32H/L28 replicated to high peak titres (>10(8) SIV RNA copies ml(-1)), persisted at high levels and induced distinctive pathology in lymphoid tissues. In cynomolgus macaques vaccinated with SIVmacC8, no evidence of detectable superinfection was observed in 3/8 vaccinates following challenge 3 or 20 weeks later with SIVmac32H/L28. Analyses after SIVmac32H/L28 challenge revealed a significant reduction in viral RNA (P<0.001) and DNA levels between 20 week vaccinates and challenge controls. Amongst 3 week vaccinates, less potent protection was observed. However, analysis of env from breakthrough virus indicated >99% sequence similarity with the vaccine virus. Highly sensitive PCR assays that distinguish vaccine and challenge virus stocks demonstrated restimulation of replication of the vaccine virus SIVmacC8 in the face of potent protection against a vigorous, homologous challenge virus. Vaccine-induced antiviral neutralizing antibodies and anti-Nef CD8+ cytotoxic T cell responses did not correlate with the outcome of the challenge. Defining the mechanism of vaccine protection will need to account for the effective control of a genetically closely related challenge virus whilst remaining unable to suppress replication of the pre-existing vaccine virus. The role of innate and intrinsic anti-retroviral immunity in the protection conferred by live attenuated SIV vaccines warrants careful study.
    Journal of General Virology 10/2008; 89(Pt 9):2240-51. DOI:10.1099/vir.0.2008/001693-0 · 3.18 Impact Factor