Evolution of the receptor binding properties of the influenza A(H3N2) hemagglutinin

The hemagglutinin (HA) of influenza A(H3N2) virus responsible for the 1968 influenza pandemic derived from an avian virus. On introduction into humans, its receptor binding properties had changed from a preference for avian receptors (α2,3-linked sialic acid) to a preference for human receptors (α2,6-linked sialic acid). By 2001, the avidity of human H3 viruses for avian receptors had declined, and since then the affinity for human receptors has also decreased significantly. These changes in receptor binding, which correlate with increased difficulties in virus propagation in vitro and in antigenic analysis, have been assessed by virus hemagglutination of erythrocytes from different species and quantified by measuring virus binding to receptor analogs using surface biolayer interferometry. Crystal structures of HA–receptor analog complexes formed with HAs from viruses isolated in 2004 and 2005 reveal significant differences in the conformation of the 220-loop of HA1, relative to the 1968 structure, resulting in altered interactions between the HA and the receptor analog that explain the changes in receptor affinity. Site-specific mutagenesis shows the HA1 Asp-225→Asn substitution to be the key determinant of the decreased receptor binding in viruses circulating since 2005. Our results indicate that the evolution of human influenza A(H3N2) viruses since 1968 has produced a virus with a low propensity to bind human receptor analogs, and this loss of avidity correlates with the marked reduction in A(H3N2) virus disease impact in the last 10 y.Surveillance of influenza viruses is essential for updating vaccines, for tracking the emergence of drug resistant viruses, and for monitoring zoonotic infections. It also gives important insights into the mechanisms of virus evolution. This is particularly the case for interpreting the correlation between antigenic differences and changes in the sialic acid receptor binding properties of the HA glycoprotein. The correlation in these two properties arises because of the close proximity on HA of binding sites for antibodies that neutralize virus infectivity and the sialic acid receptor binding pocket (1), and accounts for the observations that mutations that prevent antibody binding can also result in changes in receptor binding (2–7). Reduction in affinity of human H3N2 viruses for avian receptors since the beginning of the pandemic in 1968 has meant that by the 1990s viruses with reduced ability to agglutinate chicken erythrocytes had emerged (8, 9). Moreover, viruses isolated after 1999 were shown to have reduced affinity for both human and avian receptors, a feature that correlated with their poor growth properties in eggs and different cells in culture (9–14). The evolution of the HA has resulted in at least three key changes that influence receptor binding. Two sequential substitutions occurred at residue 225: in 2001–2002, a substitution Gly-225→Asp was accompanied by a Trp-222→Arg substitution, and in 2004–2005, an Asp-225→Asn substitution was accompanied by the substitution Ser-193→Phe (while maintaining arginine at position 222). Residue 226, a key amino acid in determining receptor specificity (15), also changed twice: before 2001, Leu-226→Val, and in 2004, Val-226→Ile (Fig. S1).To correlate these amino acid substitutions with the biological properties of the viruses, we have analyzed the receptor binding characteristics of H3N2 viruses isolated between 2001 and 2010, examined changes in their ability to infect cells in culture, and determined the structures of two HAs of virus isolates from 2004 and 2005 in the absence of receptor and complexed with a human receptor analog. The data show that the progressive decrease in binding of these viruses to human receptors from 2000 onward correlates with changes in the efficiencies of infection of cultured cells. Comparison of structural data for HAs of viruses from 1968, 2004, and 2005 explain how particular mutations that affect the conformation of the HA1 220-loop component of the receptor binding site define the receptor binding phenotype of recent H3N2 human influenza viruses.     

Characteristics of a Specific Radioimmunoassay for Measurement of Ferritin on the Surface of Peripheral Mononuclear White Blood Cells in Cancer Patients

Using ¹²⁵I-labeled rabbit anti-Hodgkin's spleen ferritin antibody (RHF), a simple radioimmunoassay has been developed for quantitation of ferritin on the surface of peripheral blood mononuclear white blood cells (PBM). This method makes use of a % specific binding determination (%SP) by measuring the amount of ¹²⁵I-labeled RHF bound to 1 × 10⁶ PBM in the presence and absence of soluble ferritin. To standardize this procedure, artificial ferritin positive control cells were prepared by covalently coupling ferritin to cultured acute lymphoblastic luekemia cells. These cells were tested on a daily basis in parallel with patient PBM's to ensure inter and intra-assay precision and remained stable for over two years. Characteristics of ¹²⁵I-labeled RHF binding to control and patient PBM's were evaluated to determine the specificity of interaction and optimum binding parameters. %SP was linear in the range of 1 × 10⁵ - 1 × 10⁶ PBM's and was progressively inhibited by graded concentrations of soluble ferritin. F(ab')₂ preparations of RHF were equally as effective as intact RHF in blocking ¹²⁵I-labeled RHF binding confirming that ¹²⁵I-labeled RHF was not binding non-specifically to PBM Fc receptors. Additional experiments describing kinetics and methods of standardization of new lots of ¹²⁵I-labeled RHF are also described.     

Gesunderhaltung und Entlastung pflegender Angeh?riger von Demenzkranken durch ein ?initiales Case Management“

Background

When facing the well-known demographic development with an increasing number of people suffering from dementia, there is a need of programmes to support nursing relatives and care at home. Many support services have been established in the past few years but they are rarely used by the relatives and the patients. The purpose of the Lighthouse Project Ulm (ULTDEM Study) was to prove the effectiveness of a single advisory approach in order to provide support services after care level classification and to relieve the burden placed on relatives caring for family members suffering from dementia (“initial case management”).

Methods

The ULTDEM Study is a prospective, open, randomized, controlled, interventional study with different parallel outcome measures (burden of caring, quality of life and mood). After the randomization, the interventional group was given comprehensive, individual advice about available treatment possibilities for dementia patients. Control group participants received standard treatment. Inclusion criteria were application of a care level (0 or 1) as well as dementia diagnosis. All participants (patients/relatives) underwent an initial and a 6?month comprehensive assessment.

Results

Our results show that a single advisory approach does not lead to a significant difference in outcome measures in interventional and control groups. Those tendencies described have to be interpreted as clinically not relevant. Although utilization of support services increases, it remains similar in both study groups. A confirmatory interpretation has not been possible due to a lack of adjustment to the findings regarding multiple testing and an insufficient degree of recruitment. Possible causes will be discussed such as premature intervention during the course of the disease, a lack of intervention blinding, recruitment bias and lack of an influence on adherence with regard to the use of support services.

Implications

The study demonstrates that there is a substantial information deficit for persons affected by dementia and their relatives. Innovative ways still have to be developed to ensure that this information actually reaches the target audience.     

Combined Liver Transplantation and Gastric Sleeve Resection for Patients With Medically Complicated Obesity and End‐Stage Liver Disease

Obesity is increasingly common before and after liver transplantation (LT), yet optimal management remains unclear. Our aim was to analyze the effectiveness of a multidisciplinary protocol for obese patients requiring LT, including a noninvasive pretransplant weight loss program, and a combined LT plus sleeve gastrectomy (SG) for obese patients who failed to lose weight prior to LT. Since 2006, all patients referred LT with a BMI > 35 were enrolled. There were 37 patients who achieved weight loss and underwent LT alone, and 7 who underwent LT combined with SG. In those who received LT alone, weight gain to BMI > 35 was seen in 21/34, post‐LT diabetes (DM) in 12/34, steatosis in 7/34, with 3 deaths plus 3 grafts losses. In patients undergoing the combined procedure, there were no deaths or graft losses. One patient developed a leak from the gastric staple line, and one had excess weight loss. No patients developed post‐LT DM or steatosis, and all had substantial weight loss (mean BMI = 29). Noninvasive pretransplant weight loss was achieved by a majority, though weight gain post‐LT was common. Combined LT plus SG resulted in effective weight loss and was associated with fewer post‐LT metabolic complications. Long‐term follow‐up is needed.     

Eating Disorders “Mental Health Literacy” in Low Risk,High Risk and Symptomatic Women: Implications for Health Promotion Programs

Attitudes and beliefs concerning the nature and treatment of bulimia nervosa (BN) were compared among young adult women at low risk of an eating disorder (n = 332), at high risk (n = 83), or already showing symptoms (n = 94). Participants completed a self-report questionnaire that included a measure of eating disorder symptoms. A vignette of a fictional person suffering from BN was presented, followed by a series of questions addressing the nature and treatment of the problem described. High-risk and symptomatic participants were more likely than low-risk participants to report that they would not approach anyone for advice or help, were they to have BN or a similar problem, because they would not want anyone to know. Symptomatic participants were more likely to believe that someone with BN would be discriminated against, more likely to consider bulimic behaviors to be acceptable, and more likely to view BN as being common among women in the community, than low-risk participants, participants in the high-risk group being intermediate on each of these questions. The findings suggest that the attitudes and beliefs of individuals with eating disorder symptoms differ systematically from those of individuals at high risk, but who do not yet have symptoms, and from those at low risk. They also indicate specific attitudes and beliefs that may need to be addressed in prevention and early intervention programs. The potential benefits of assessing individuals' attitudes and beliefs concerning the nature and treatment of eating-disordered behaviour and tailoring program content accordingly may be worthy of investigation.