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author:("Myers, maclyn")
1.  Compensatory Hemagglutinin Mutations Alter Antigenic Properties of Influenza Viruses 
Journal of Virology  2013;87(20):11168-11172.
Influenza viruses routinely acquire mutations in antigenic sites on the globular head of the hemagglutinin (HA) protein. Since these antigenic sites are near the receptor binding pocket of HA, many antigenic mutations simultaneously alter the receptor binding properties of HA. We previously reported that a K165E mutation in the Sa antigenic site of A/Puerto Rico/8/34 (PR8) HA is associated with secondary neuraminidase (NA) mutations that decrease NA activity. Here, using reverse genetics, we show that the K165E HA mutation dramatically decreases HA binding to sialic acid receptors on cell surfaces. We sequentially passaged reverse-genetics-derived PR8 viruses with the K165E antigenic HA mutation in fertilized chicken eggs, and to our surprise, viruses with secondary NA mutations did not emerge. Instead, viruses with secondary HA mutations emerged in 3 independent passaging experiments, and each of these mutations increased HA binding to sialic acid receptors. Importantly, these compensatory HA mutations were located in the Ca antigenic site and prevented binding of Ca-specific monoclonal antibodies. Taken together, these data indicate that HA antigenic mutations that alter receptor binding avidity can be compensated for by secondary HA or NA mutations. Antigenic diversification of influenza viruses can therefore occur irrespective of direct antibody pressure, since compensatory HA mutations can be located in distinct antibody binding sites.
PMCID: PMC3807274  PMID: 23926344
2.  Single Hemagglutinin Mutations That Alter both Antigenicity and Receptor Binding Avidity Influence Influenza Virus Antigenic Clustering 
Journal of Virology  2013;87(17):9904-9910.
The hemagglutination inhibition (HAI) assay is the primary measurement used for identifying antigenically novel influenza virus strains. HAI assays measure the amount of reference sera required to prevent virus binding to red blood cells. Receptor binding avidities of viral strains are not usually taken into account when interpreting these assays. Here, we created antigenic maps of human H3N2 viruses that computationally account for variation in viral receptor binding avidities. These new antigenic maps differ qualitatively from conventional antigenic maps based on HAI measurements alone. We experimentally focused on an antigenic cluster associated with a single N145K hemagglutinin (HA) substitution that occurred between 1992 and 1995. Reverse-genetics experiments demonstrated that the N145K HA mutation increases viral receptor binding avidity. Enzyme-linked immunosorbent assays (ELISA) revealed that the N145K HA mutation does not prevent antibody binding; rather, viruses possessing this mutation escape antisera in HAI assays simply by attaching to cells more efficiently. Unexpectedly, we found an asymmetric antigenic effect of the N145K HA mutation. Once H3N2 viruses acquired K145, an epitope involving amino acid 145 became antigenically dominant. Antisera raised against an H3N2 strain possessing K145 had reduced reactivity to H3N2 strains possessing N145. Thus, individual mutations in HA can influence antigenic groupings of strains by altering receptor binding avidity and by changing the dominance of antibody responses. Our results indicate that it will be important to account for variation in viral receptor binding avidity when performing antigenic analyses in order to identify genuine antigenic differences among influenza virus variants.
PMCID: PMC3754131  PMID: 23824816
3.  Immune history shapes specificity of pandemic H1N1 influenza antibody responses 
The Journal of Experimental Medicine  2013;210(8):1493-1500.
The specificity of H1N1 antibody responses can be shifted to epitopes near the HA receptor–binding domain after sequential infections with viral strains that share homology in this region.
Human antibody responses against the 2009 pandemic H1N1 (pH1N1) virus are predominantly directed against conserved epitopes in the stalk and receptor-binding domain of the hemagglutinin (HA) protein. This is in stark contrast to pH1N1 antibody responses generated in ferrets, which are focused on the variable Sa antigenic site of HA. Here, we show that most humans born between 1983 and 1996 elicited pH1N1 antibody responses that are directed against an epitope near the HA receptor–binding domain. Importantly, most individuals born before 1983 or after 1996 did not elicit pH1N1 antibodies to this HA epitope. The HAs of most seasonal H1N1 (sH1N1) viruses that circulated between 1983 and 1996 possess a critical K133 amino acid in this HA epitope, whereas this amino acid is either mutated or deleted in most sH1N1 viruses circulating before 1983 or after 1996. We sequentially infected ferrets with a 1991 sH1N1 virus and then a pH1N1 virus. Sera isolated from these animals were directed against the HA epitope involving amino acid K133. These data suggest that the specificity of pH1N1 antibody responses can be shifted to epitopes near the HA receptor–binding domain after sequential infections with sH1N1 and pH1N1 viruses that share homology in this region.
PMCID: PMC3727314  PMID: 23857983
4.  Neuronal ferritin heavy chain and drug abuse affect HIV-associated cognitive dysfunction 
Interaction of the chemokine CXCL12 with its receptor CXCR4 promotes neuronal function and survival during embryonic development and throughout adulthood. Previous studies indicated that μ-opioid agonists specifically elevate neuronal levels of the protein ferritin heavy chain (FHC), which negatively regulates CXCR4 signaling and affects the neuroprotective function of the CXCL12/CXCR4 axis. Here, we determined that CXCL12/CXCR4 activity increased dendritic spine density, and also examined FHC expression and CXCR4 status in opiate abusers and patients with HIV-associated neurocognitive disorders (HAND), which is typically exacerbated by illicit drug use. Drug abusers and HIV patients with HAND had increased levels of FHC, which correlated with reduced CXCR4 activation, within cortical neurons. We confirmed these findings in a nonhuman primate model of SIV infection with morphine administration. Transfection of a CXCR4-expressing human cell line with an iron-deficient FHC mutant confirmed that increased FHC expression deregulated CXCR4 signaling and that this function of FHC was independent of iron binding. Furthermore, examination of morphine-treated rodents and isolated neurons expressing FHC shRNA revealed that FHC contributed to morphine-induced dendritic spine loss. Together, these data implicate FHC-dependent deregulation of CXCL12/CXCR4 as a contributing factor to cognitive dysfunction in neuroAIDS.
PMCID: PMC3904611  PMID: 24401274
5.  Educating Pharmacy Students to Improve Quality (EPIQ) in Colleges and Schools of Pharmacy 
Objective. To assess course instructors’ and students’ perceptions of the Educating Pharmacy Students and Pharmacists to Improve Quality (EPIQ) curriculum.
Methods. Seven colleges and schools of pharmacy that were using the EPIQ program in their curricula agreed to participate in the study. Five of the 7 collected student retrospective pre- and post-intervention questionnaires. Changes in students’ perceptions were evaluated to assess their relationships with demographics and course variables. Instructors who implemented the EPIQ program at each of the 7 colleges and schools were also asked to complete a questionnaire.
Results. Scores on all questionnaire items indicated improvement in students’ perceived knowledge of quality improvement. The university the students attended, completion of a class project, and length of coverage of material were significantly related to improvement in the students’ scores. Instructors at all colleges and schools felt the EPIQ curriculum was a strong program that fulfilled the criteria for quality improvement and medication error reduction education.
Conclusion The EPIQ program is a viable, turnkey option for colleges and schools of pharmacy to use in teaching students about quality improvement.
PMCID: PMC3425924  PMID: 22919085
quality improvement; medication error; pharmacy education; pharmacy student; assessment; curriculum
6.  Oseltamivir-resistant influenza viruses get by with a little help from permissive mutations 
Influenza A viruses (IAVs) encode two critical glycoproteins, hemagglutinin and neuraminidase (NA). Hemagglutinin promotes viral docking onto cells via interactions with IAV’s receptor, sialic acid and NA facilitates release of newly synthesized virions by cleaving cellular and viral sialic acid. NA inhibitors, such as oseltamivir, are widely used drugs that work by binding to the active site of NA. Although oseltamivir-resistant viruses were easily generated years ago in laboratory experiments, it was widely believed that these viruses would not be able to circulate in the human population as they did not replicate efficiently. However, oseltamivir-resistant H1N1 viruses rapidly spread during the 2007–2008 IAV season and these viruses contained precisely the same exact drug-resistance mutation identified years prior, a histidine to tyrosine substitution at NA residue 274 (H274Y). Unlike the experimentally derived NA inhibitor-resistant viruses, 2007–2008 H1N1 viruses containing H274Y replicated efficiently. Bloom et al. have solved this riddle by identifying permissive NA mutations that allow viruses to tolerate H274Y. Here, we discuss these important findings and speculate how these studies may facilitate early detection of drug-resistant strains in the future.
PMCID: PMC3102564  PMID: 21504394
influenza virus; neuraminidase; neuraminidase inhibitors; oseltamivir

Results 1-6 (6)