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Anti-HIV-1 broadly neutralizing antibodies (bnAbs) have been extensively tested against pesudoviruses of diverse strains. We generated and characterized HIV-1 primary isolates from antiretroviral naïve infected Indian children, and determined their susceptibility to known NAbs. All the 8 isolates belonged to subtype-C and were R5 tropic. Majority of these viruses were resistant to neutralization by NAbs, suggesting that the bnAbs, known to efficiently neutralize pseudoviruses (adult and pediatric) of different strains, are less effective against pediatric primary isolates. Interestingly, AIIMS_329 isolate displayed high susceptibility to neutralization by PG9 and PG16bnAbs, with IC 50 titer of 1.3 and 0.97 μg/ml, suggesting exposure of this epitope on this virus. All isolates except AIIMS_506 were neutralized by contemporaneous plasma antibodies. Our findings suggest that primary isolates, due to close resemblance to viruses in natural infection, should be used to evaluate NAbs as effective vaccine candidates in both children and adults. [ABSTRACT FROM AUTHOR]

Abstract: One approach to the development of an HIV vaccine is to design a protein template which can present gp120 epitopes inducing cross-neutralizing antibodies. To select a V3 sequence for immunogen design, we compared the neutralizing activities of 18 anti-V3 monoclonal antibodies (mAbs) derived from Cameroonian and Indian individuals infected with clade AG and C, respectively. It was found that V3 mAbs from the Cameroonian patients were significantly more cross-neutralizing than those from India. Interestingly, superior neutralizing activity of Cameroonian mAbs was also observed among the nine VH5-51/VL lambda genes encoding V3 mAbs which mediate a similar mode of recognition. This correlated with higher relative binding affinity to a variety of gp120s and increased mutation rates in V3 mAbs from Cameroon. These results suggest that clade C V3 is probably weakly immunogenic and that the V3 sequence of CRF02_AG viruses can serve as a plausible template for vaccine immunogen design. [Copyright &y& Elsevier]

Abstract: Chemokine receptors CXCR7 and CXCR4 bind to the same ligand stromal cell derived factor-1alpha (SDF-1α/CXCL12). We assessed the downstream signaling pathways mediated by CXCL12–CXCR7 interaction in Jurkat T cells. All experiments were carried out after functionally blocking the CXCR4 receptor. CXCL12, on binding CXCR7, induced phosphorylation of extra cellular regulated protein kinases (ERK 1/2) and Akt. Selective inhibition of each signal demonstrated that phosphorylated ERK 1/2 is essential for chemotaxis and survival of T cells whereas activation of Akt promotes only cell survival. Another interesting finding of this study is that CXCL12–CXCR7 interaction under normal physiological conditions does not activate the p38 pathway. Furthermore, we observed that the CXCL12 signaling via CXCR7 is Giα independent. Our findings suggest that CXCR7 promotes cell survival and does not induce cell death in T cells. The CXCL12 signaling via CXCR7 may be crucial in determining the fate of the activated T cells. [Copyright &y& Elsevier]