Journal club presentation 10 07 2015
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Journal club presentation from Christa Buckheit Sturdevant et al
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Journal club presentation 10 07 2015
- 2. IF – 8 (2013)
- 3. Background
- 4. HIV in the CNS HAD • Psychomotor slowing • Mood changes • Anxiety • Memory deficits • Abstraction • Information processing • Decision making • Verbal fluency • Attention Microglia Perivascular mΦ CD8 CD4 Th monocytes HIV Acute Neuron Cellularfactors Viralproteins Inflammatoryresponses Astrocyte Blood Brain BBB Diapedesis • Cognitive impairment • Motor disorders • Behavioral changes HAND CD4 Pleocytosis
- 5. Background • Virologic characteristics associated with early CNS infection. • Cross-sectional and longitudinal study • Cohort of 72 ART naïve infected for <2 yrs • Paired CSF and Plasma samples collected at enrollment, 6 wks and every 6 months thereafter – Timing of compartmentalization establishment – Relationship between cellular inflammation, viral loads and phylogenetic state – Longitudinal maintenance and evolution of compartmentalization
- 6. Table 1. Background demographic and clinical characteristics of study participants at baseline.
- 7. Paired blood & CSF SGA 54/144 Phylogenetic analysis Comp: SM Fst Snn Compartmentalization assessment
- 8. Temporal patterns of CNS viral replication and inflammation Treated the 144 samples as independent observations • Acute 0-4 months • Early 5-12 months • Established 13-24 months Conclusion: Detectable CNS compartmentalized populations are present at greater frequency With longer time since HIV-1 exposure
- 9. Factors associated with CSF viral loads Inflammation: WBC>10cell/ulNo Inflammation: WBC<10cell/ul Conc: increased viral burden in the CNS can result from two factors, independent CNS replication or influx of infected cells
- 10. Persistence of viral replication in the CNS Evaluation of the persistence of viral replication in the CNS 20/37CSF viral loads of > 1000cp/ml 2 yrs follow up 9/20- eq(-) with min pleocytosis in all time points 11/20 – pleocytosis and/or comp 6/20 - states in 2 or more time points Concl: Local replication and/or inflammation can persist or reoccur over time
- 11. Viral evolution in the CNS over time Paired blood and CSF SGA Seq and align Neighbor joining trees and Bayesian analysis - BEAST
- 12. Equilibrated < 4 months Compart. > 4 months Viral entry phenotype Paired blood and CSF SGA Pseudotyped viruses Affinofile cells: CD4 and CCR5 differentially induced Infected affinofile cells with either high or low CD4 lysis Luciferase Assay Concl: CNS is initially exposed to R5- tropic variants and the viruses remain R5 T cell tropic for the first 2 years but evolution to macrophage tropism also begins during this period
- 13. InterComp No Low CD4 and MDM Equi populations with low CD4 infectivity had also low MDM infectivity Growth of pseudoviruses in MDM from 3 donors Pseudoviruses were first grown in high CD4 affinofile cells
- 14. Discussion Four states can define the relationship between virus in the CSF/CNS and blood early during infection.
- 15. Conclusions • Local HIV replication and robust CNS inflammatory response in the CNS begins early • In a subset of the subjects CNS involvement can persist over time • Viral population in CSF is dynamic as a result of local replication and influx of infected CD4 T cells.
- 16. Thank you
- 18. No contamination between subjects
Editor's Notes
- The brain is an immune privileged site where CD4 T cells are highly regulated to prevent inflammatory reactions that could affect the brain HIV in the brain is thought to be brought by infected monocytes from the peripheral circulation mainly at the post capillary venules Monocytes are less efficiently infected by HIV, they are infected at low levels during high viremia in acute HIV infection.
- A small number of monocytes will become infected and then enter the brain by transmigration across the BBB by a process called diapedesis at the post capillary venules. These monocytes then differentiate into perivascular MΦ and microglia cells which are specialized brain macrophages. These cells support virus replication and can transmit the virus to uninfected perivascular MΦ and microglia cells. Infection of the brain however does not lead to encephalitis due to adequate control of the viral replication by HIV-specific CD8+ and CD4+ Th cells that are recruited into the brain from the peripheral. This is partly because the brain is an immune privileged site where T cell activation and inflammatory responses are regulated to avoid immune-mediated damage to neurons and glial cells HIV therefore remains latent within perivascular MΦ or microglial cells throughout the asymptomatic period HIV propagates better in activated CD4 cells than in macrophages or microglial cells. The turnover of virus in monocytes-derived cells is slow and non-cytopathic, hence the cells serve as reservoir of HIV during the chronic stage of disease. The phenotype of this virus shows that it is adapted to monocyte-derived cells and preferentially use the CCR5 co-receptor for entry. As the disease progresses, there is eventual lack of immune control of HIV infection in the periphery. During the late stage of infection, or AIDS, latent HIV replication is activated including in the brain. HIV replication in the brain result in increase in inflammatory cytokines that overwhelm the immune regulatory mechanisms and lead to damage of neurons resulting in HAD. Neurodegeneration is not a direct effect of infection of HIV to neurons, astrocytes and oligodendrocytes which are poor target. It is thought that it is caused indirectly by inflammatory mediators released from activated macrophages and microglial cells during excessive inflammatory responses as well as by neurotoxic viral products such as gp 120, tat and vpr released from infected cells Astrocytes are also damaged leading to reduced glutamate reuptake and diminished maintenance of the neurons. Excess glutamate promotes apoptosis Damage to oligodendrocytes affects the myelin sheath necessary for nerve signal transduction. Pleocytosis is increased WBC count in the CSF, typically more than 5 WBC/ul of CSF.
- Values shown are medians Subjects with sufficient viral RNA loads in the CSF (&gt;1,000 copies of viral RNA/ml; to ensure adequate sampling) for further SGA analysis at one or more time points within the first two years.
- CNS lineages were interpreted as being significantly compartmentalized if all three tests were significant (p values &lt; 0.05) CNS phylogenetic state are defined as: Fig A; Equilibrated, with similar populations between the blood and CSF, with no evidence of independence CNS replication and Fig B: compartmentalized: with a genetically distinct CSF population as indicated by three statistically significant measures of compartmentalization. Compartmentalized populations typically included clonally amplified variants often with more genetically diverse variants fig B, 9040 and sometimes with the presence of recombinants between clonally amplified variants fig B, 9096 HIV-1 blood and CSF populations early during infection can be equilibrated or compartmentalized. HIV CNS replication evidence by clonal amplification can lead to influx of T-cells that amplify some of these lineages
- Regardless of the time of infection, The CSF viral concentration was less than 1000c/ml in approx. 65% of the samples, approx 30% equilibrated with blood viral populations, 25-50% of equilibrated had pleocytosis. Compartmentalization occur only after 4 months
- CSF samples with compartmentalized populations had elevated viral RNA loads when compared to the samples with only equilibrated populations in the absence of pleocytosis When pleocytosis was present and the CSF viral loads were high enough for SGA analysis, the viral populations were most often equilibrated fig D open circles, with a CSF viral load that was significantly higher than for equilibrated populations without pleocytosis (p = 0.0008) This suggest that the influx of infected CD4 T cells associated with pleocytosis brings virus into the CSF/CNS from blood
- 37 subjects followed longitudinally 17/37 of the subjects were not analyzed by SGA coz viral loads were &lt;1000cp/ml 9/20 had equilibrated populations with minimal to no pleocytosis at all time points analyzed. The remaining 11 subjects all showed evidence of pleocytosis and/or compartmentalized viral replication at one or more time points within the initial two yrs period 6/20 had one of these states at two or more time points (reoccurrence) Evidence of persistent viral replication in the CNS If the initial sample showed evidence of compartmentalization or an equilibrated population with pleocytosis then subsequent samples were significantly more likely to also be compartmentalized of have pleocytosis than if the initial sample was not in one of these states
- Compartmentalization can persist and evolve independently within the CSF over time. In subjects 9040 and 9021, a compartmentalized CNS population was observed at enrollment and for all analyzed longitudinally time points, spanning a period of 753 and 201 days p.i. Pattern 1 observed in subject 9040: a compartmentalized, clonally amplified population present at the initial time point (d165) was replaced with a second compartmentalized, clonally amplified variants at day 352 but the sampling included a recombinant between the first and second clonally amplified variants. Several recombinants between these two early populations were maintained through day 918, however, the overall population was equilibrated at this last time point. The TMRCA of blood population at the initial time point was estimated to be 209 days, which was reasonably consistent with the reported date of transmission (165 days) Initial clonally amplified CSF population was established 33 days prior to sampling (approx. 170 days after transmission), followed by a subsequent clonal amplidication event and recombination between the two lineages. Second trend was seen in subject 9021 The reported date of transmission, 140 days was reasonably close to the transmission bottleneck estimated using BEAST at 159 days prior to sampling. One compartmentalized clonally amplified lineage was detected in the CSF at the first sampling time point with an estimated age of 102 days. This lineage was not present in the second sampling point at d341 but was replaced by a different compartmentalized clonally amplified variant with estimated age of 55 days For subject 9021 a permissive environment for viral replication in which variants were successively and independently amplified within the CNS. Sub 7146 Transmission of two variants with one sequestered in the CNS also occurs in aldults Two transmitted variants diverged from each other in the donor (965 days but with a reported date of transmission of 156 days prior to sampling) while the transmitted variants diversified in the recipient. One lineage that was present in the blood and CSF went through a bottleneck (presumably genetic bottleneck) at 134 days prior to sampling, consistent with the reported transmission date of 156 days prior to sampling. The other variant was sequestered in the CNS with an estimated bottleneck of 85 days, appearing early as a clonally amplified variant. In addition, a series of recombinants between these two lineages appeared in both the blood and CSF over time.
- Fig 5. All viruses required high levels of CD4 for efficient entry, indicative of primarily being selected for replication in CD4+ T cells. All pseudotyped viruses representing all phylogenetic states and a wide range of days p.i. all required high levels aof CCR5 and CD4 for efficient entry and were considered R5 T-cell-tropic Env proteins derived from CSF samples containing compartmentalized viral lineages were significantly better at entering cells expressing low CD4 than Env proteins derived from equilibrated CSF samples, although their level didn’t near the level of a macrophage-tropic Env protein-Ba-L This shows that the compartmentalized lineages are adapting to enter low CD4 cells in the CNS Viruses isolated from CSF of adults within four months of infection are uniformly poor at infecting low CD4 cells indication that they have been selected for replication in T cells which adds to the proof that macrophage-tropic viruses are not transmitted.
- Infectivity of macrophage pseudotyped viruses on monocyte-derived macrophages generated from three separate donors The viruses were first grown in cells expressing high levels of CD4 and then added to MDM There was a general concordance between infectivity on affinofile cells and infectivity on MDMs although the level of infectivity differed significantly between three donors. Viruses representing subjects with equilibrated populations with low infectivity on affinofile cells with low CD4 had low infectivity on MDM. Viruses from four of the five subjects with CNS compartmentalization were also assessed for their ability to enter affinofile cells expressing low levels of CD4 and MDMs. Both blood and CSF derived viruses from one subject, 9096 were observed to have intermediate infectivity on low CD4 affinofile cells and MDMs. Two of the compartmentalized subjects, 9018 and 9021 had CSF-derived viruses with elevated infectivity of low CD4 affinofile cells and MDMs. Both blood and CSF- derived viruses from one compartmentalized subject, 7146 were unable to efficiently enter both low CD4 expressing affinofile cells and MDMs. The conclusion here remains the same as that from infection of affinofile cells although the variability of infectivity of MDMs between donors precludes an accurate assessment of the range of CD4 entry phenotypes that can be observed using affinofile cells.
- Fig A was observed in subjects with little evidence of CNS replication or pleocytosis, with CSF HIV-1 RNA concentrations proportionally 1-2% of the viral load in the periphery. In many of the subjects, the CSF HIV-1 RNA level was very low, below the limit of detection of standard assays. With little or no pleocytosis, HIV-1 is likely entering the CNS at low levels via incomplete partitioning of virus at BBB or low level trafficking of immune cells including small numbers of infected CD4+ T cells. The viral population is very similar to the population in the blood. Fig B Equilibrated viral populations with elevated viral load and high levels of pleocytosis. These equilibrated populations were most likely the result of the release of virus from increased numbers on infected CD4+ T cells trafficking from the periphery into the CNS. Fig C Clonally amplified CSF populations of low complexity representing the recent expansion of identical or nearly identical variants that required high levels of CD4 fro entry (CD4 R5-tropic viruses) Fig D More genetically complex compartmentalized viral replication within the CSF/CNS indication of persistent replication beyond a single clonal amplification event.