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1.  Low frequency of genotypic resistance in HIV-1-infected patients failing an atazanavir-containing regimen: a clinical cohort study 
Dolling, David I. | Dunn, David T. | Sutherland, Katherine A. | Pillay, Deenan | Mbisa, Jean L. | Parry, Chris M. | Post, Frank A. | Sabin, Caroline A. | Cane, Patricia A. | Aitken, Celia | Asboe, David | Webster, Daniel | Cane, Patricia | Castro, Hannah | Dunn, David | Dolling, David | Chadwick, David | Churchill, Duncan | Clark, Duncan | Collins, Simon | Delpech, Valerie | Geretti, Anna Maria | Goldberg, David | Hale, Antony | Hué, Stéphane | Kaye, Steve | Kellam, Paul | Lazarus, Linda | Leigh-Brown, Andrew | Mackie, Nicola | Orkin, Chloe | Rice, Philip | Pillay, Deenan | Phillips, Andrew | Sabin, Caroline | Smit, Erasmus | Templeton, Kate | Tilston, Peter | Tong, William | Williams, Ian | Zhang, Hongyi | Zuckerman, Mark | Greatorex, Jane | Wildfire, Adrian | O'Shea, Siobhan | Mullen, Jane | Mbisa, Tamyo | Cox, Alison | Tandy, Richard | Hale, Tony | Fawcett, Tracy | Hopkins, Mark | Ashton, Lynn | Booth, Claire | Garcia-Diaz, Ana | Shepherd, Jill | Schmid, Matthias L. | Payne, Brendan | Hay, Phillip | Rice, Phillip | Paynter, Mary | Bibby, David | Kirk, Stuart | MacLean, Alasdair | Gunson, Rory | Coughlin, Kate | Fearnhill, Esther | Fradette, Lorraine | Porter, Kholoud | Ainsworth, Jonathan | Anderson, Jane | Babiker, Abdel | Fisher, Martin | Gazzard, Brian | Gilson, Richard | Gompels, Mark | Hill, Teresa | Johnson, Margaret | Kegg, Stephen | Leen, Clifford | Nelson, Mark | Palfreeman, Adrian | Post, Frank | Sachikonye, Memory | Schwenk, Achim | Walsh, John | Huntington, Susie | Jose, Sophie | Thornton, Alicia | Glabay, Adam | Orkin, C. | Garrett, N. | Lynch, J. | Hand, J. | de Souza, C. | Fisher, M. | Perry, N. | Tilbury, S. | Gazzard, B. | Nelson, M. | Waxman, M. | Asboe, D. | Mandalia, S. | Delpech, V. | Anderson, J. | Munshi, S. | Korat, H. | Welch, J. | Poulton, M. | MacDonald, C. | Gleisner, Z. | Campbell, L. | Gilson, R. | Brima, N. | Williams, I. | Schwenk, A. | Ainsworth, J. | Wood, C. | Miller, S. | Johnson, M. | Youle, M. | Lampe, F. | Smith, C. | Grabowska, H. | Chaloner, C. | Puradiredja, D. | Walsh, J. | Weber, J. | Ramzan, F. | Mackie, N. | Winston, A. | Leen, C. | Wilson, A. | Allan, S. | Palfreeman, A. | Moore, A. | Wakeman, K.
Journal of Antimicrobial Chemotherapy  2013;68(10):2339-2343.
Objectives
To determine protease mutations that develop at viral failure for protease inhibitor (PI)-naive patients on a regimen containing the PI atazanavir.
Methods
Resistance tests on patients failing atazanavir, conducted as part of routine clinical care in a multicentre observational study, were randomly matched by subtype to resistance tests from PI-naive controls to account for natural polymorphisms. Mutations from the consensus B sequence across the protease region were analysed for association and defined using the IAS-USA 2011 classification list.
Results
Four hundred and five of 2528 (16%) patients failed therapy containing atazanavir as a first PI over a median (IQR) follow-up of 1.76 (0.84–3.15) years and 322 resistance tests were available for analysis. Recognized major atazanavir mutations were found in six atazanavir-experienced patients (P < 0.001), including I50L and N88S. The minor mutations most strongly associated with atazanavir experience were M36I, M46I, F53L, A71V, V82T and I85V (P < 0.05). Multiple novel mutations, I15S, L19T, K43T, L63P/V, K70Q, V77I and L89I/T/V, were also associated with atazanavir experience.
Conclusions
Viral failure on atazanavir-containing regimens was not common and major resistance mutations were rare, suggesting that adherence may be a major contributor to viral failure. Novel mutations were described that have not been previously documented.
doi:10.1093/jac/dkt199
PMCID: PMC3772741  PMID: 23711895
HIV; drug resistance mutations; naive patients; protease inhibitors; virological failure
2.  Host–Pathogen Interaction in Invasive Salmonellosis 
PLoS Pathogens  2012;8(10):e1002933.
Salmonella enterica infections result in diverse clinical manifestations. Typhoid fever, caused by S. enterica serovar Typhi (S. Typhi) and S. Paratyphi A, is a bacteremic illness but whose clinical features differ from other Gram-negative bacteremias. Non-typhoidal Salmonella (NTS) serovars cause self-limiting diarrhea with occasional secondary bacteremia. Primary NTS bacteremia can occur in the immunocompromised host and infants in sub-Saharan Africa. Recent studies on host–pathogen interactions in Salmonellosis using genome sequencing, murine models, and patient studies have provided new insights. The full genome sequences of numerous S. enterica serovars have been determined. The S. Typhi genome, compared to that of S. Typhimurium, harbors many inactivated or disrupted genes. This can partly explain the different immune responses both serovars induce upon entering their host. Similar genome degradation is also observed in the ST313 S. Typhimurium strain implicated in invasive infection in sub-Saharan Africa. Virulence factors, most notably, type III secretion systems, Vi antigen, lipopolysaccharide and other surface polysaccharides, flagella, and various factors essential for the intracellular life cycle of S. enterica have been characterized. Genes for these factors are commonly carried on Salmonella Pathogenicity Islands (SPIs). Plasmids also carry putative virulence-associated genes as well as those responsible for antimicrobial resistance. The interaction of Salmonella pathogen-associated molecular patterns (PAMPs) with Toll-like receptors (TLRs) and NOD-like receptors (NLRs) leads to inflammasome formation, activation, and recruitment of neutrophils and macrophages and the production of pro-inflammatory cytokines, most notably interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, and interferon-gamma (IFN)-γ. The gut microbiome may be an important modulator of this immune response. S. Typhimurium usually causes a local intestinal immune response, whereas S. Typhi, by preventing neutrophil attraction resulting from activation of TLRs, evades the local response and causes systemic infection. Potential new therapeutic strategies may lead from an increased understanding of infection pathogenesis.
doi:10.1371/journal.ppat.1002933
PMCID: PMC3464234  PMID: 23055923
3.  Gag Determinants of Fitness and Drug Susceptibility in Protease Inhibitor-Resistant Human Immunodeficiency Virus Type 1▿ †  
Journal of Virology  2009;83(18):9094-9101.
Mutations can accumulate in the protease and gag genes of human immunodeficiency virus in patients who fail therapy with protease inhibitor drugs. Mutations within protease, the drug target, have been extensively studied. Mutations in gag have been less well studied, mostly concentrating on cleavage sites. A retroviral vector system has been adapted to study full-length gag, protease, and reverse transcriptase genes from patient-derived viruses. Patient plasma-derived mutant full-length gag, protease, and gag-protease from a multidrug-resistant virus were studied. Mutant protease alone led to a 95% drop in replication capacity that was completely rescued by coexpressing the full-length coevolved mutant gag gene. Cleavage site mutations have been shown to improve the replication capacity of mutated protease. Strikingly, in this study, the matrix region and part of the capsid region from the coevolved mutant gag gene were sufficient to achieve full recovery of replication capacity due to the mutant protease, without cleavage site mutations. The same region of gag from a second, unrelated, multidrug-resistant clinical isolate also rescued the replication capacity of the original mutant protease, suggesting a common mechanism that evolves with resistance to protease inhibitors. Mutant gag alone conferred reduced susceptibility to all protease inhibitors and acted synergistically when linked to mutant protease. The matrix region and partial capsid region of gag sufficient to rescue replication capacity also conferred resistance to protease inhibitors. Thus, the amino terminus of Gag has a previously unidentified and important function in protease inhibitor susceptibility and replication capacity.
doi:10.1128/JVI.02356-08
PMCID: PMC2738216  PMID: 19587031

Results 1-3 (3)