アクティブボード・２００９年　６月
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研究発表を行った学会；
・Keystone Symposia
HIV Immunobiology: From Infection to Immune Control (X4).
　２００９年　３月２２日〜２７日（Keystone,Denver,U.S.A.）

タイトル；The effects of CTL-escape conferring mutations on Nef's pathogenic functions in primary macrophages.
　
発表者；　Philip Mwimanzi　氏
　　　（熊本大学　エイズ学研究センター　ウイルス制御分野）
Abstract；
　It has been shown that CTL-mediated pressure selects CTL-escape conferring mutations even in a well-conserved PxxP region of Nef that resulted in impaired pathogenic functions of Nef in the T cell compartment. However, because it has been shown that Nef exhibits different activities in different cell lineages, we asked whether these mutations affect Nef's biological activity in macrophages, another major cell type that supports HIV replication in vivo.
We first prepared monocyte derived macrophages (MDM) from CD14+ cells isolated from HIV-negative donors by culturing them for 5 days in the presence of M-CSF. The resultant MDM was infected with a CCR5-tropic strain JRFL virus in which the nef region had been replaced with that from the SF2 strain. This virus showed replication comparable to the parental JRFL in primary MDM. In contrast, the nef-deficient JRFL variant showed much diminished replication compared to the parental one, confirming the enhancement of viral replication activity by Nef in MDM. We then introduced several mutations (R75T, Y85F, and both) in Nef that confer escape from HLA-B35-restricted CTLs. We observed that the variant viruses had much decreased replication in MDM compared to the wild-type virus. We also examined another Nef activity, that is, cell surface receptor modulation in HIV-infected MDMs. We observed that HLA class I down regulation activity by Nef was impaired as evidenced by higher surface expression of HLA class I molecules on the MDMs infected by the variant viruses compared to those infected by the wild-type virus, whereas the CD4 molecules were comparably down regulated among the cells infected with wild-type and variant viruses. These results suggested that the macrophages infected with variant viruses could lead to increased susceptibility to CTL killing in vivo.
Our present data demonstrate that CTL responses targeting Nef PxxP region can impose functional constraints in two important pathogenic functions of Nef in macrophages, further highlighting the significance of the HIV-1 Nef specific CTL immunosurveillance in Nef`s biological activity during HIV infection.