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Cross-group neutralization of HIV-1 and evidence for conservation of the PG9/PG16 epitopes within divergent groups

Braibant, Martinea; Gong, Eun-Yeunga,*; Plantier, Jean-Christophec; Moreau, Thierryd; Alessandri, Elodiec; Simon, Françoise; Barin, Francisa,b

doi: 10.1097/QAD.0b013e32835ecb42
Basic Science: Concise Communication

Objective: HIV-1 has been classified into four groups: M, N, O and P. The aim of this study was to revisit the cross-group neutralization using a highly diverse panel of primary isolates.

Design: The panel of viruses included nine HIV-1 group O primary isolates, one recombinant M/O primary isolate, one group N primary isolates, one group P primary isolate, two group M (subtype B) primary isolates and the HIV-1 group M adapted strain MN.

Methods: All the viruses were tested for neutralization in TZM-bl cells, using sera issued from patients infected by viruses of group M (n = 11), O (n = 12) and P (n = 1), and a panel of nine human monoclonal broadly neutralizing antibodies (HuMo bNAbs).

Results: Although the primary isolates displayed a wide spectrum of sensitivity to neutralization by the human sera, cross-group neutralization was clearly observed. In contrast, the bNAbs did not show any cross-group neutralization, except PG9 and PG16. Interestingly, the group N prototype strain YBF30 was highly sensitive to neutralization by PG9 (IC50: 0.28 μg/ml) and PG16 (IC50: < 0.12 μg/ml). The interaction between PG9 and key residues of YBF30 was confirmed by molecular modeling.

Conclusion: The conservation of the PG9 and PG16 epitopes within groups M and N provides an argument for their relevance as components of a potentially efficient HIV vaccine immunogen.

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aUniversité François-Rabelais - Inserm U966

bLaboratoire de Bactériologie-Virologie, CHU Bretonneau, Tours

cUniversité de Rouen and CHU Charles Nicolle, Rouen

dUniversité François Rabelais - Inserm U1100, Tours

eLaboratoire de Virologie, Hôpital Saint-Louis, Paris, France.

*Present address: The Beatson Institute for Cancer Research, Switchback Road, Bearsden, G61 1BD, Glasgow, UK.

Correspondence to Dr Francis Barin, Laboratoire de Virologie, CHU Bretonneau, 37044, Tours Cedex, France. Tel: +33 2 4747 8058; fax: +33 2 4747 3610; e-mail:

Received 3 November, 2012

Revised 17 December, 2012

Accepted 9 January, 2013

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© 2013 Lippincott Williams & Wilkins, Inc.