In contrast to human immunodeficiency virus (HIV)-infected humans, natural hosts for simian immunodeficiency virus (SIV) very rarely progress to acquired immunodeficiency syndrome (AIDS).While the mechanisms underlying this disease resistance are still poorly understood, a consistent feature of natural SIV infection is the absence of the generalized immune activation associated with HIV infection. To investigate the immunologic mechanisms underlying the absence of AIDS in SIV-infected sooty mangabeys (SMs), a natural host species, we performed a detailed analysis of the SIV-specific cellular immune responses in 110 SIV-infected SMs. We found that while SIV-specific T-cell responses are detectable in the majority of animals, their magnitude and breadth are, in fact, lower than what has been described in HIVinfected humans, both in terms of cytokine production (ie, IFN-␥, TNF-␣, and IL-2) and degranulation (ie, CD107a expression). Of importance, SIV-specific Tcell responses were similarly low when either SIVmac239-derived peptides or autologous SIVsmm peptides were used as stimuli. No correlation was found between SIV-specific T-cell responses and either viral load or CD4 ؉ T-cell count, or between these responses and markers of T-cell activation and proliferation. These findings indicate that the absence of AIDS in naturally SIV-infected sooty mangabeys is independent of a strong cellular immune response to the virus. IntroductionThe acquired immunodeficiency syndrome (AIDS) pandemic originated from zoonotic transmission of simian immunodeficiency viruses (SIVs) from infected African monkey species to humans. 1 Of the natural SIV hosts, sooty mangabeys (Cercocebus atys, SMs) are of interest for 2 main reasons. First, SIVsmm, the virus infecting SMs, is the origin of the human immunodeficiency virus 2 (HIV-2) epidemic in humans. 1-3 Second, SIVsmm is the source of the prototype SIVmac strains (ie, SIVmac239, SIVmac251) that induce an AIDS-like disease in the rhesus macaque (RM), a nonnatural host for SIV, and consequently are widely used for studies of AIDS pathogenesis and vaccines. 2,4-6 SIVsmm and HIV-1/2 share many features in terms of life cycle and molecular structure, and the extent of virus replication is similarly high in naturally SIV-infected SMs and HIV-infected humans. 7-9 However, the outcome of these infections is strikingly different. The vast majority of HIV-infected humans, unless treated chronically with antiretroviral therapy (ART), will develop progressive CD4 ϩ T-cell depletion and eventually succumb to AIDS. In contrast, the vast majority of naturally SIV-infected SMs maintain normal CD4 ϩ T-cell counts and live an apparently normal lifespan in captivity, [7][8][9] with only one report of classic AIDS to date. 10 It is important to note that the disease resistance of naturally SIV-infected SMs that show high levels of SIV viremia is substantially different from that of a rare subset of HIV-infected individuals defined as long-term nonprogressors, in whom viral replication is usually very lo...

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Previous studies suggested that the topological properties of brain anatomical networks may be aberrant in schizophrenia (SCZ), and most of them focused on the chronic and antipsychotic-medicated SCZ patients which may introduce various confounding factors due to antipsychotic medication and duration of illness. To avoid those potential confounders, a desirable approach is to select medication-naïve, first-episode schizophrenia (FE-SCZ) patients. In this study, we acquired diffusion tensor imaging datasets from 30 FE-SCZ patients and 34 age- and gender-matched healthy controls. Taking a distinct gray matter region as a node, inter-regional connectivity as edge and the corresponding streamline counts as edge weight, we constructed whole-brain anatomical networks for both groups, calculated their topological parameters using graph theory, and compared their between-group differences using nonparametric permutation tests. In addition, network-based statistic method was utilized to identify inter-regional connections which were impaired in the FE-SCZ patients. We detected only significantly decreased inter-regional connections in the FE-SCZ patients compared to the controls. These connections were primarily located in the frontal, parietal, occipital, and subcortical regions. Although small-worldness was conserved in the FE-SCZ patients, we found that the network strength and global efficiency as well as the degree were significantly decreased, and shortest path length was significantly increased in the FE-SCZ patients compared to the controls. Most of the regions that showed significantly decreased nodal parameters belonged to the top-down control, sensorimotor, basal ganglia, and limbic-visual system systems. Correlation analysis indicated that the nodal efficiency in the sensorimotor system was negatively correlated with the severity of psychosis symptoms in the FE-SCZ patients. Our results suggest that the network organization is changed in the early stages of the SCZ disease process. Our findings provide useful information for further understanding the brain white matter dysconnectivity of schizophrenia.

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