Natural Host Genetic Resistance to Lentiviral CNS Disease: A Neuroprotective MHC Class I Allele in SIV-Infected Macaques

Human immunodeficiency virus (HIV) infection frequently causes neurologic disease even with anti-retroviral treatment. Although associations between MHC class I alleles and acquired immunodeficiency syndrome (AIDS) have been reported, the role MHC class I alleles play in restricting development of HIV-induced organ-specific diseases, including neurologic disease, has not been characterized. This study examined the relationship between expression of the MHC class I allele Mane-A*10 and development of lentiviral-induced central nervous system (CNS) disease using a well-characterized simian immunodeficiency (SIV)/pigtailed macaque model. The risk of developing CNS disease (SIV encephalitis) was 2.5 times higher for animals that did not express the MHC class I allele Mane-A*10 (P = 0.002; RR = 2.5). Animals expressing the Mane-A*10 allele had significantly lower amounts of activated macrophages, SIV RNA, and neuronal dysfunction in the CNS than Mane-A*10 negative animals (P<0.001). Mane-A*10 positive animals with the highest CNS viral burdens contained SIV gag escape mutants at the Mane-A*10-restricted KP9 epitope in the CNS whereas wild type KP9 sequences dominated in the brain of Mane-A*10 negative animals with comparable CNS viral burdens. These concordant findings demonstrate that particular MHC class I alleles play major neuroprotective roles in lentiviral-induced CNS disease

Diastolic dysfunction is associated with myocardial viral load in simian immunodeficiency virus-infected macaques

Objective: To establish the relationship between HIV-induced cardiac diastolic dysfunction, immune responses, and virus replication in the heart using the simian immunodeficiency virus (SIV)/macaque model. Design: Cardiac diastolic dysfunction is common in HIV-infected individuals including asymptomatic patients and those treated with combination antiretroviral therapy. SIV-infected macaques develop cardiac dysfunction, serving as a useful model to establish mechanisms underlying HIV-induced cardiac dysfunction. To understand the relationship between functional cardiac impairment, viral replication in the heart, and associated host inflammatory responses, cardiac function was evaluated in SIV-infected macaques and functional decline was correlated with features of the host immune response and the extent of viral replication in both the myocardium and plasma. Methods: Cardiac function was evaluated longitudinally in 22 SIV-infected and eight uninfected macaques using mitral inflow and tissue Doppler echocardiography. Myocardial macrophage populations were evaluated by CD68 and CD163 immunostaining. SIV RNA levels in both myocardium and plasma were measured by qRT-PCR. Results: Echocardiographic abnormalities developed in SIV-infected macaques that closely resembled diastolic dysfunction reported in asymptomatic HIV-infected individuals. Although CD68 and CD163 were upregulated in the myocardium of SIV-infected animals, neither macrophage marker correlated with functional decline. SIV-induced diastolic dysfunction was strongly correlated with extent of SIV replication in the myocardium, implicating virus or viral proteins in the initiation and progression of cardiac dysfunction. Conclusion: This study demonstrated a strong correlation between cardiac functional impairment and extent of SIV replication in the myocardium, suggesting that persistent viral replication in myocardial macrophages induces cardiomyocyte damage manifest as diastolic dysfunction.9 page(s

SIV infection induced encephalitis, increased CNS CD68 expression, and axonal accumulation of APP.

<p>SIV-infected pig-tailed macaques that developed encephalitis had multifocal perivascular accumulations of infiltrating macrophages and multinucleate giant cells (A, arrows denote giant cells, * denotes blood vessel lumen, hematoxylin and eosin stain, bar = 50 uM), increased CNS CD68 expression reflecting activation of macrophages and microglia in subcortical white matter shown by immunohistochemical staining with an anti-CD68 antibody (B, bar = 50 uM), and accumulation of APP in axons (arrows) in the corpus callosum (C, bar = 100 uM).</p

Viral Escape in the CNS of <i>Mane-A*10</i> Animals with SIV Encephalitis.

<p>The four <i>Mane-A^*10</i> positive animals (animals 18292, PVg2, A4P012, and A2P005) with the highest CNS viral burdens contained high levels of <i>gag</i> escape mutants (K165R) in the CNS. In contrast, wild type KP9 sequences strongly dominated in the brain of <i>Mane-A^*10</i> negative animals. Wild type KP9 sequences also were exclusively detected in viral stocks of SIV/DeltaB670 and SIV/17E-Fr used for inoculation.</p

Reduced CNS macrophage activation, SIV replication, and axonal APP accumulation associated with <i>Mane-A*10</i> expression.

<p><i>Mane-A*10</i> expression was associated with reduced CNS inflammation, SIV replication and neuronal damage in SIV-infected macaques. A) SIV-infected macaques expressing the <i>Mane-A*10</i> allele (circles) had significantly lower CNS macrophage infiltration and activation than animals without the allele (triangles, <i>P</i> = 0.001) shown by measuring the amount of CD68 immunostaining in subcortical white matter of the brain. B) Animals expressing the <i>Mane-A*10</i> allele (circles) also had significantly lower SIV RNA in the basal ganglia of the brain than animals without the allele (triangles, <i>P</i><0.001). SIV RNA was measured by real time RT-PCR. C) Animals expressing the <i>Mane-A*10</i> allele (circles) also had significantly lower axonal accumulation of APP in the corpus callosum than animals without the allele (triangles, <i>P</i><0.001,) demonstrating that expression of <i>Mane-A*10</i> is neuroprotective. Solid (black) symbols represent the SIV-infected animals that developed SIV encephalitis whereas the open symbols indicate animals that were SIV-infected but did not develop SIV encephalitis.</p

Mane-A*10 expression did not influence CD4+ T cell decline or plasma viral load but was associated with lower CSF viral loads.

<p>Comparing longitudinal trends in CD4+ T cell decline from baseline pre-infection values and plasma SIV RNA demonstrated that <i>Mane-A*10</i> expression was not associated with either extent of CD4+ T cell decline throughout infection (A) or with altered plasma viral load set points in untreated SIV-infected macaques at any time point from primary through asymptomatic to terminal stages of (B). To determine whether <i>Mane-A*10</i> expression was associated with altered viral replication in the periphery, mean plasma viral load throughout infection was measured in untreated SIV-infected animals grouped by <i>Mane-A*10</i> status (<i>Mane-A*10</i> positive animals represented by circles, n = 11; <i>Mane-A*10</i> negative animals represented by triangles, n = 21). Plasma viral load also did not differ significantly between these groups at any time-point from day 14 post-inoculation until terminal sampling (<i>P</i>>0.05). Similarly, <i>Mane-A*10</i> expression status was not associated with extent of % CD4+ T cell decline in SIV-infected macaques, with no statistically significant difference between groups of animals composed of <i>Mane-A*10</i> positive animals (circles) versus <i>Mane-A*10</i> negative macaques (triangles). Combined, these data indicate that neither plasma viral load or CD4+ T cell loss are associated with expression of <i>Mane-A*10</i> in pigtailed macaques inoculated with SIV/17E-Fr and SIV/DeltaB670. In contrast, mean SIV RNA levels in CSF were lower in the group of <i>Mane-A*10</i> positive animals (circles) versus <i>Mane-A*10</i> negative macaques (triangles).</p

HIV and SIV Induce Alterations in CNS CaMKII Expression and Activation : A Potential Mechanism for Cognitive Impairment

The molecular mechanisms underlying learning and memory impairment in patients with HIV-associated neurological disease have remained unclear. Calcium/calmodulin-dependent kinase II (CaMKII) has key roles in synaptic potentiation and memory storage in neurons and also may have immunomodulatory functions. To determine whether HIV and simian immunodeficiency virus (SIV) induce alterations in CaMKII expression and/or activation (autophosphorylation) in the brain, we measured CaMKII alterations by quantitative immunoblotting in both an in vitro HIV/neuronal culture model and in vivo in an SIV-infected macaque model of HIV-associated neurological damage. Using primary rat hippocampal neuronal cultures treated with culture supernatants harvested from HIV-1–infected human monocyte-derived macrophages (HIV/MDM), we found that CaMKII activation declined after exposure of neurons to HIV/MDM. Consistent with our in vitro measurements, a significant decrease in CaMKII activation was present in both the hippocampus and frontal cortex of SIV-infected macaques compared with uninfected animals. In SIV-infected animals, total CaMKII expression in the hippocampus correlated well with levels of synaptophysin. Furthermore, CaMKII expression in both the hippocampus and frontal cortex was inversely correlated with viral load in the brain. These findings suggest that alterations in CaMKII may compromise synaptic function in the early phases of chronic neurodegenerative processes induced by HIV