CROI 2015 Program and Abstracts

Abstract Listing

Poster Abstracts

Methods: 46 Nef clones isolated from chronically HIV subtype B-infected subjects were analyzed for down-regulation of HLA-A, HLA-B, and HLA-C on the surface of virus-infected cells by flow cytometry. A set of cells singly expressing various HLA class I alleles (HLA-A2, A24, A33, B35, B57, and Cw4) and a T cell line endogenously expressing multiple HLA class I, including HLA-A2 and HLA-B51, were analyzed. Results: In 46 primary Nef clones, HLA-B showed greater resistance to Nef-mediated down-regulation compared to HLA-A (p<0.001), regardless of cell type examined. No Nef clone down-regulated HLA-C. A Nef codon-function analysis revealed that amino acid variations at Nef-202 substantially affected Nef-mediated HLA-A and HLA-B down-regulation function; this was subsequently confirmed by site-directed mutagenesis. Specifically, the Tyr-202 to Glu mutation alone was sufficient to selectively impair Nef-mediated HLA-B down-regulation. Moreover, a crystal structure of the ternary complex of Nef, HLA-A2 cytoplasmic tail peptide and the mu1 subunit of the host AP1 revealed that Nef-202 is in close proximity to the end of the HLA-A cytoplasmic tail where HLA-B lacks three amino acids compared to HLA-A, suggesting that this Nef residue may play a role in increased binding to the HLA-A cytoplasmic tail and facilitating down-regulation. Conclusions: Taken together, results indicate that natural sequence variability within HIV-1 Nef affects the interaction with polymorphic HLA class I cytoplasmic tails for down- regulation, providing us with further insight into this complex pathway of immune evasion.

THURSDAY, FEBRUARY 26, 2015 Session P-B1 Poster Session 2:30 pm– 4:00 pm Viral Origins and Recombinant Forms 229 Geopolitical Effects in the Epidemiology of HIV-1 Subtype

Poster Hall

Gkikas Magiorkinis 2 ; Kostantinos Angelis 1 ; Ioannis Mamais 1 ; Angelos Hatzakis 1 ; Jan Albert 3 ; Glenn Lawyer 4 ; AnnemarieWensing 5 ; Charles Boucher 6 ; Anne-MiekeVandamme 7 ; Dimitrios Paraskevis 1 1 University of Athens, Athens, Greece; 2 University of Oxford, Oxford, United Kingdom; 3 Karolinska Institutet, Stockholm, Sweden; 4 Max Planck Institute for Informatics, Saarbrücken, Germany; 5 University Medical Center Utrecht, Utrecht, Netherlands; 6 Erasmus University Medical Center, Rotterdam, Netherlands; 7 KU Leuven, Leuven, Belgium Background: HIV-1 was discovered in the early 1980’s when the virus had already established a pandemic. For at least three decades the epidemic in the Western World has been dominated by subtype B infections. Initially, the virus travelled from Africa through Haiti to the USA. Methods: We assembled a globally representative dataset of HIV-1 subtype B sequences (N=8,370), by pooling molecular data collected from patient-cohorts and systematically selected molecular epidemiology studies from around the world. We analyzed the sequences using statistical phylogeography run on 250 bootstrap trees. To date, this is the largest global phylogeographic study of subtype B. Results: We found that North America provided an active hub of dispersal for most local epidemics globally, while Western Europe also received infections frommost of the other regions, namely from North and Central/South America, the Caribbean, Africa and Oceania. Significant migration events from Africa and Oceania to Europe, suggests that only a small number of subtype B infections are imported from these areas to Europe. Eastern Europe was initially isolated, but more recently provided spill-overs to Western Europe. Global phylogeographic trees show that European strains tend to cluster together, whereas North American strains are highly dispersed across the global genetic diversity. Sequences from North America also tend to have deeper roots than groups of sequences found in other regions, suggesting that North America has seeded the pandemic through multiple founder effect. Within Western Europe the United Kingdomwas the most active in exchanging infections with non-European countries. As for mobility the most connected areas within Europe were found in the South. We also found that the degree of viral export from countries correlated with their number of subtype B infections. Major migrations can be connected to historical events. Conclusions: The global spread of subtype B was not random. Viewing these patterns against the historical background, we observe that they strikingly mirror major geopolitical landmarks and trends since the end of World War II, namely the American influence over the Western World, the rise and fall of the Iron Curtain and major colonial relationships. 230 The 2 Phases of HIV-1 Group O Diversification Marie Leoz 1 ; Felix Feyertag 2 ; Anfumbom Kfutwah 3 ; Philippe Mauclere 4 ; Guillaume Lachenal 5 ; Florence Damond 6 ;Veronique Lemee 1 ; Francois Simon 7 ; David Robertson 2 ; Jean-Christophe Plantier 1 1 University Hospital Rouen, Rouen, France; 2 Manchester University, Manchester, United Kingdom; 3 Centre Pasteur du Cameroun, Yaounde, Cameroon; 4 Direction Interarmées du Service de Santé, Noumea, New Caledonia; 5 Université Paris Diderot, Paris, France; 6 APHP CHU Bichat Claude Bernard, Paris, France; 7 APHP CHU Saint Louis, Paris, France Background: HIV-1 is subdivided into four groups: M, O, N and P. Group M is responsible for the pandemic, N and P are found in very few patients, and group O is endemic in Cameroon where it represents ~1% of HIV infections. Group O genetic diversity and evolution remain poorly characterised. Previous studies estimated its emergence to be as early as group M and have proposed different nomenclature systems. Here we fully investigate group O evolution, using an extensive dataset comprising sequences sampled from France, Cameroon and Gabon. Methods: 190 HIV-O patients were sampled in France, Cameroon and Gabon between 1987 and 2012. Viral sequences from three regions of the genome were concatenated (total: 2012 base pairs) and analysed using phylogenetic and Bayesian population genetic methods to characterize evolutionary history. Results: The tree topology was atypical, with a predominant clade emerging from a broad and genetically diverse base population. The presence of the Y181C mutation, naturally conferring resistance to non-nucleoside reverse transcriptase inhibitors, was significantly associated to the emergent clade. The year of the most recent common ancestor (MRCA) was estimated to be around 1930, close to that of group M and consistent with previous estimates. Bayesian skyline analysis indicates group O diversification has gone through two exponential growth phases. The first phase, around 1950, resulted in widespread genetic diversity, while the second, from the late 1970s to the early 1990s, gave rise to the emergent clade. According to the historical context in Cameroon, the first wave of group O expansion might have been favoured by iatrogenic routes of transmission between 1940 – 1960, while the second wave would rather be associated to the development of urbanization. Conclusions: While groups O and M share a similar age, group O has remained largely confined to Cameroon. This has resulted in broad genetic diversity and intermixing of sub-populations, making it impossible to classify subtypes using a similar system as is used for group M. However, two subgroups can be observed corresponding to two successive phases of diversification. The viral properties of the two subgroups need to be investigated, to better understand why the now predominant clade was the most recent to emerge.

Poster Abstracts

213

CROI 2015