Recombinant HIV Envelope Proteins Fail to Engage Germline Versions of Anti-CD4bs bNAbs

Vaccine candidates for HIV-1 so far have not been able to elicit broadly neutralizing antibodies (bNAbs) although they express the epitopes recognized by bNAbs to the HIV envelope glycoprotein (Env). To understand whether and how Env immunogens interact with the predicted germline versions of known bNAbs, we screened a large panel (N:56) of recombinant Envs (from clades A, B and C) for binding to the germline predecessors of the broadly neutralizing anti-CD4 binding site antibodies b12, NIH45-46 and 3BNC60. Although the mature antibodies reacted with diverse Envs, the corresponding germline antibodies did not display Env-reactivity. Experiments conducted with engineered chimeric antibodies combining the mature and germline heavy and light chains, respectively and vice-versa, revealed that both antibody chains are important for the known cross-reactivity of these antibodies. Our results also indicate that in order for b12 to display its broad cross-reactivity, multiple somatic mutations within its VH region are required. A consequence of the failure of the germline b12 to bind recombinant soluble Env is that Env-induced B-cell activation through the germline b12 BCR does not take place. Our study provides a new explanation for the difficulties in eliciting bNAbs with recombinant soluble Env immunogens. Our study also highlights the need for intense efforts to identify rare naturally occurring or engineered Envs that may engage the germline BCR versions of bNAbs

HIV-1 gp120 Induces Expression of IL-6 through a Nuclear Factor-Kappa B-Dependent Mechanism: Suppression by gp120 Specific Small Interfering RNA

In addition to its role in virus entry, HIV-1 gp120 has also been implicated in HIV-associated neurocognitive disorders. However, the mechanism(s) responsible for gp120-mediated neuroinflammation remain undefined. In view of increased levels of IL-6 in HIV-positive individuals with neurological manifestations, we sought to address whether gp120 is involved in IL-6 over-expression in astrocytes. Transfection of a human astrocyte cell line with a plasmid encoding gp120 resulted in increased expression of IL-6 at the levels of mRNA and protein by 51.3±2.1 and 11.6±2.2 fold respectively; this effect of gp120 on IL-6 expression was also demonstrated using primary human fetal astrocytes. A similar effect on IL-6 expression was observed when primary astrocytes were treated with gp120 protein derived from different strains of X4 and R5 tropic HIV-1. The induction of IL-6 could be abrogated by use of gp120-specific siRNA. Furthermore, this study showed that the NF-κB pathway is involved in gp120-mediated IL-6 over-expression, as IKK-2 and IKKβ inhibitors inhibited IL-6 expression by 56.5% and 60.8%, respectively. These results were also confirmed through the use of NF-κB specific siRNA. We also showed that gp120 could increase the phosphorylation of IκBα. Furthermore, gp120 transfection in the SVGA cells increased translocation of NF-κB from cytoplasm to nucleus. These results demonstrate that HIV-1 gp120-mediated over-expression of IL-6 in astrocytes is one mechanism responsible for neuroinflammation in HIV-infected individuals and this is mediated by the NF-κB pathway

International Differences in Conditional Conservatism - The Role of Unconditional Conservatism and Income Smoothing

Prior research documents that conditional conservatism, measured as the asymmetric timeliness of earnings reflecting bad vs. good news, varies with cross-country differences in institutional regimes. In this paper, we examine the determinants of conditional conservatism and related earnings attributes internationally. First, using panel data, we investigate whether competing earnings attributes such as unconditional conservatism and income smoothing affect conditional conservatism and its international differences. We find that these attributes are predictably correlated with conditional conservatism. Second, we address the question whether income smoothing and conditional conservatism are two fundamentally different earnings attributes. We show theoretically that both attributes yield different earnings distributions and that the motivations for producing earnings which possess these attributes differ. To test these predictions empirically, we calculate firm-specific time-series measures of asymmetric timeliness, using a novel trigonometric measure based on the standard Basu (1997)-type regression. Using this cross-sectional data, we test whether conditional conservatism and income smoothing are different and find them to be only weakly correlated for a broad international sample. Also, we demonstrate that income smoothing explains international differences in conditional conservatism. Finally, we estimate simple determinant models of conditional conservatism and income smoothing, showing that both earnings attributes are driven by different explanatory firm-level factors: Conditional conservatism increases with the importance of debt financing, while income smoothing increases with the importance of dividends. Despite some important limitations, we believe our results to be meaningful because they show that cross-country differences in conditional conservatism are influenced by the effects of other accounting properties, predominantly income smoothing. Especially, legal regime appears to drive income smoothing while losing its explanatory power for conditional conservatism when firm-specific factors are controlled for.