Mismatched hemagglutinin and neuraminidase specificities in recent human H3N2 influenza viruses

The hemagglutinin (HA) of influenza viruses initiates infection by binding to sialic acid on the cell surface via alpha2,6 (human) or alpha2,3 (avian) linkage. The influenza neuraminidase (NA) can cleave both alpha2,3- and alpha2,6-linked sialic acids, but all influenza NAs have a marked preference for the non-human alpha2,3 linkage. Recent H3N2 influenza viruses have lost the ability to agglutinate chicken red blood cells. To determine if changes in HA specificity or affinity correlate with NA specificity or activity, we examined red cell binding and elution of a series of H3N2 viruses. We found that the NA activity of many influenza viruses does not release binding by their HA. In some egg-adapted strains, lack of elution correlates with low levels of viral NA activity, and these elute rapidly when bacterial NA is added. However, a Fujian-like virus, A/Oklahoma/323/03, does not elute by its own NA or with Vibrio cholerae sialidase, and it binds to red cells pre-treated with V. cholerae sialidase. It elutes after addition of the broad specificity Micromonospora viridifaciens sialidase. Human glycophorin inhibits A/Oklahoma/323/03 hemagglutination 6-fold better than fetuin. We conclude that specific forms of sialic acid are used as receptor by recent human H3N2 influenza viruses, perhaps involving branched alpha2,6 sialic acid or alpha2,8 sialic acid structures on O-linked carbohydrates. The virus itself has no O-linked glycans, so even though the NA is not able to cleave receptors on cells, the viruses will not self-aggregate. It will be important to monitor efficacy of neuraminidase inhibitors in case there are NA-resistant receptors in the human respiratory tract that allow the viruses to be less dependent on NA activity.     

Culture of phenotypically defined hematopoietic stem cells and other progenitors at limiting dilution on Dexter monolayers.

Highly enriched, phenotypically defined hematopoietic stem, Thy-1loLin-Sca-1+, and progenitor cell populations from mouse bone marrow (BM) were tested at limiting dilution for their ability to reconstitute Dexter monolayers. Several classes of BM cells can reconstitute Dexter cultures, first forming discrete "cobblestone" areas which then mature into colonies consisting primarily of maturing myeloid and erythroid cells. Most such colonies have a limited lifespan in culture. Only the Thy-1loLin-Sca-1+ cell fraction gives rise to colonies that survive longer than 3 weeks, which suggests that a limiting-dilution analysis for long-term reconstitution of Dexter cultures can serve as a quantitative measure of stem cell activity. Additional experiments were performed to assess the formation of new progenitor cells in reconstituted Dexter cultures. Again, only cultures seeded with the stem cell-enriched fraction contained expanded numbers of replatable WEHI-3 CM responsive colony-forming cells (CFU-GM). Quantitative analysis indicates that 97% of the replatable CFU-GM of whole BM is contributed by the Thy-1loLin-Sca-1+ cell fraction, again suggesting a potential stem cell-specific assay. Such quantitative in vitro assays might prove useful in characterization and isolation of human stem cells where in vivo assays are lacking.     

Bone marrow transplantation: how important is CD34 cell dose in HLA-identical stem cell transplantation?

A recent analysis of Fred Hutchinson Cancer Research Center data has been undertaken to investigate the association of infused CD34 cell dose with various clinical outcomes after HLA-identical transplantation. Separate assessments for unrelated vs related donors and the use of bone marrow or mobilized G-CSF stimulated peripheral blood mononuclear cells (G-PBMC) have been incorporated. The three primary findings are: (1) Higher CD34 dose results in better neutrophil and platelet recovery in all settings. (2) Higher CD34 doses (8 x 10(6)/kg) are associated with the development of more chronic graft-versus-host disease when using related G-PBMC. (3) Higher CD34 dose is correlated with improved survival after unrelated donor bone marrow transplantation. These data suggest that the CD34 content of a graft can have a significant impact on clinical outcome after allogeneic transplantation, but defining an optimal dose is dependent on both the type of donor and the stem cell source.     

Intervention to reduce intentions to use tobacco among pediatric cancer survivors.

PURPOSE: In this randomized controlled trial, we sought to determine whether a risk counseling intervention would increase knowledge and perceived vulnerability to tobacco-related health risks and decrease future intentions to use tobacco among preadolescents and adolescents previously treated for cancer. PATIENT AND METHODS: Participants included 103 cancer survivors between the ages of 10 and 18 years who were randomly assigned to either a standard care control (SCC) group or a tobacco intervention (TI) group. Patients in the SCC group received standard advice about the risks of tobacco use. Patients in the TI group received more intensive late effects risk counseling in addition to an educational video, goal setting, written physician feedback, smoking literature, and follow-up telephone counseling. The effect of our intervention was assessed by self-reported knowledge, perceived vulnerability, and intentions at baseline, 6, and 12 months. RESULTS: Compared with the SCC group, patients who received our intervention had significantly higher knowledge scores, higher perceived vulnerability scores, and lower intention scores at 12 months. No significant differences between the SCC and TI groups at 6 months, across all measures, were found. CONCLUSION: Pediatric survivors' knowledge, perceived vulnerability to health risks, and intentions to use tobacco can be modified by a risk counseling intervention. The delayed effect of our intervention indicates that these changes may evolve over time. Implications for health care providers who engage in tobacco counseling with young cancer survivors are discussed. Additional longitudinal studies are needed to determine definitive long-term intervention effects on actual tobacco use in this high-risk population.     

Airborne Infection with Bacillus anthracis��from Mills to Mail

The lack of identified exposures in 2 of the 11 cases of bioterrorism-related inhalation anthrax in 2001 raised uncertainty about the infectious dose and transmission of Bacillus anthracis. We used the Wells-Riley mathematical model of airborne infection to estimate 1) the exposure concentrations in postal facilities where cases of inhalation anthrax occurred and 2) the risk for infection in various hypothetical scenarios of exposure to B. anthracis aerosolized from contaminated mail in residential settings. These models suggest that a small number of cases of inhalation anthrax can be expected when large numbers of persons are exposed to low concentrations of B. anthracis. The risk for inhalation anthrax is determined not only by bacillary virulence factors but also by infectious aerosol production and removal rates and by host factors.     

The Association Between Influenza Vaccine in Pregnancy and Adverse Neonatal Outcomes

ObjectiveTo determine whether neonatal outcomes differ between women vaccinated during pregnancy and those not vaccinated.MethodsSelf-reported history of receipt of influenza vaccination during pregnancy was collected from women at the time of admission for obstetrical delivery at the IWK Health Centre in Halifax, Nova Scotia, beginning in April 2006. The cohort for this study included women who delivered a singleton infant prior to November 2009, reflecting the pre-pandemic H1N1 vaccination period. Neonatal outcomes were compared using logistic regression between vaccinated and non-vaccinated women.ResultsOverall, 1957 of 9781 women (20%) included in the cohort received influenza vaccine during their pregnancy. The adjusted odds ratio and 95% confidence interval for a small for gestational age infant (lowest 10th percentile birth weight for gestational age and sex) was 0.80 (95% CI 0.65 to 0.95) for vaccinated women relative to non-vaccinated women. The adjusted odds ratio for a low birth weight infant was 0.74 (95% CI 0.58 to 0.95). Rates of preterm birth and a composite indicator of adverse neonatal outcomes were lower among vaccinated women, but were not statistically significant. The effects of maternal vaccination on neonatal outcomes did not differ between high- and low-risk women.ConclusionAs evidence continues to mount in support of improved neonatal outcomes associated with receiving influenza vaccination during pregnancy, enhanced public health measures are necessary to encourage pregnant women to receive the influenza vaccine.