Hemagglutination Inhibition Data Research Articles

Glycopolymer with Sulfated Fucose and 6'-Sialyllactose as a Dual-Targeted Inhibitor on Resistant Influenza A Virus Strains.

The frequent mutations of influenza A virus (IAV) have led to an urgent need for the development of innovative antiviral drugs. Glycopolymers offer significant advantages in biomedical applications owing to their biocompatibility and structural diversity. However, the primary challenge lies in the design and synthesis of well-defined glycopolymers to precisely control their biological functionalities. In this study, functional glycopolymers with sulfated fucose and 6'-sialyllactose were successfully synthesized through ring-opening metathesis polymerization and a postmodification strategy. The optimized heteropolymer exhibited simultaneous targeting of hemagglutinin and neuraminidase on the surface of IAV, as evidenced by MU-NANA assay and hemagglutination inhibition data. Antiviral experiments demonstrated that the glycopolymer displayed broad and efficient inhibitory activity against wild-type and mutant strains of H1N1 and H3N2 subtypes in vitro, thereby establishing its potential as a dual-targeted inhibitor for combating IAV resistance.

Using interpretable machine learning to extend heterogeneous antibody-virus datasets

A central challenge in biology is to use existing measurements to predict the outcomes of future experiments. For the rapidly evolving influenza virus, variants examined in one study will often have little to no overlap with other studies, making it difficult to discern patterns or unify datasets. We develop a computational framework that predicts how an antibody or serum would inhibit any variant from any other study. We validate this method using hemagglutination inhibition data from seven studies and predict 2,000,000 new values± uncertainties. Our analysis quantifies the transferability between vaccination and infection studies in humans and ferrets, shows that serum potency is negatively correlated with breadth, and provides a tool for pandemic preparedness. In essence, this approach enables a shift in perspective when analyzing data from "what you see is what you get" into "what anyone sees is what everyone gets."

Dual-Action Heteromultivalent Glycopolymers Stringently Block and Arrest Influenza A Virus Infection In Vitro and Ex Vivo.

Here, we demonstrate the concerted inhibition of different influenza A virus (IAV) strains using a low-molecular-weight dual-action linear polymer. The 6'-sialyllactose and zanamivir conjugates of linear polyglycerol are optimized for simultaneous targeting of hemagglutinin and neuraminidase on the IAV surface. Independent of IAV subtypes, hemagglutination inhibition data suggest better adsorption of the heteromultivalent polymer than homomultivalent analogs onto the virus surface. Cryo-TEM images imply heteromultivalent compound-mediated virus aggregation. The optimized polymeric nanomaterial inhibits >99.9% propagation of various IAV strains 24 h postinfection in vitro at low nM concentrations and is up to 10000× more effective than the commercial zanamivir drug. In a human lung ex vivo multicyclic infection setup, the heteromultivalent polymer outperforms the commercial drug zanamivir and homomultivalent analogs or their physical mixtures. This study authenticates the translational potential of the dual-action targeting approach using small polymers for broad and high antiviral efficacy.

H3N2 influenza hemagglutination inhibition method qualification with data driven statistical methods for human clinical trials.

Hemagglutination inhibition (HAI) antibody titers to seasonal influenza strains are important surrogates for vaccine-elicited protection. However, HAI assays can be variable across labs, with low sensitivity across diverse viruses due to lack of standardization. Performing qualification of these assays on a strain specific level enables the precise and accurate quantification of HAI titers. Influenza A (H3N2) continues to be a predominant circulating subtype in most countries in Europe and North America since 1968 and is thus a focus of influenza vaccine research. As a part of the National Institutes of Health (NIH)-funded Collaborative Influenza Vaccine Innovation Centers (CIVICs) program, we report on the identification of a robust assay design, rigorous statistical analysis, and complete qualification of an HAI assay using A/Texas/71/2017 as a representative H3N2 strain and guinea pig red blood cells and neuraminidase (NA) inhibitor oseltamivir to prevent NA-mediated agglutination. This qualified HAI assay is precise (calculated by the geometric coefficient of variation (GCV)) for intermediate precision and intra-operator variability, accurate calculated by relative error, perfectly linear (slope of -1, R-Square 1), robust (<25% GCV) and depicts high specificity and sensitivity. This HAI method was successfully qualified for another H3N2 influenza strain A/Singapore/INFIMH-16-0019/2016, meeting all pre-specified acceptance criteria. These results demonstrate that HAI qualification and data generation for new influenza strains can be achieved efficiently with minimal extra testing and development. We report on a qualified and adaptable influenza serology method and analysis strategy to measure quantifiable HAI titers to define correlates of vaccine mediated protection in human clinical trials.

Algorithmically-guided discovery of viral epitopes via linguistic parsing: Problem formulation and solving by soft computing

Effective identification of detailed biochemical features at the protein level has the potential to boost genome-based Virology and Vaccinology, by enhancing detection of viruses’ weak spots. Precise mapping of such sensitive sites, also known as the epitopes identification problem, constitutes a grand computational challenge: solving it may lead to an improved vaccine efficacy against existing as well as future viral strains. We consider the open-ended challenge of discovering unmapped epitopes. We introduce a spatial-linguistic approach, in which the relevant proteins’ sequences are considered as alphabetical strings with a linked, known 3D structure. The explicit aim is to correctly parse them into meaningful tokens/subsets with respect to the chemical space, to be associated with the virus’ epitopes. The problem is then translated into seeking an effective tokenizer/word-splitter, adhering to prescribed biochemical criteria and satisfying spatial constraints, whose output specifies subsequences that accurately map the epitopes. We devise three competing procedures, namely two chemistry-driven, parameterized heuristics as well as a constrained Subset Selection problem-solver. The heuristics require tuning, which we conduct by Evolution Strategies, whereas we employ a Genetic Algorithm as the latter problem-solver. Empirical results are presented herein for detecting epitopes of influenza A(H3N2), exhibiting an improvement with respect to the baseline reference when applied to experimental Hemagglutination Inhibition data. Finally, we discuss the potential of the proposed approach with respect to the recent SARS-CoV-2 coronavirus, in the effort to further develop and improve effective vaccines and fight the COVID-19 pandemic.

Evaluation of the immune response of a H7N9 candidate vaccine virus derived from the fifth wave A/Guangdong/17SF003/2016

Highly pathogenic influenza H7N9 viruses that emerged in the fifth wave of H7N9 outbreak pose a risk to human health. The World Health Organization has updated the candidate vaccine viruses for H7N9 viruses recently. In this study, we evaluated the immune response to an updated H7N9 candidate vaccine virus, which derived from the highly pathogenic A/Guangdong/17SF003/2016 (GD/16) in mice and rhesus macaques. GD/16 vaccination elicited robust neutralizing, virus-specific immunoglobulin G antibodies and effective protection, but poor hemagglutination inhibition antibody titers. Furthermore, mouse and rhesus macaque serum raised against the previous H7N9 CVV A/Anhui/1/2013 (AH/13) were tested for its cross-reactivity to GD/16 virus. We found that although AH/13-immune serum has poor hemagglutination inhibition reactivity against GD/16 virus, AH/13 elicit efficient cross-neutralizing antibodies and in vivo protection against GD/16. Further studies showed that the hemagglutinin of GD/16 has strong receptor binding avidity, which might be associated with the decreased hemagglutination inhibition assay sensitivity. This study underscores the point that receptor binding avidity should be taken into account when performing quantitative interpretation of hemagglutination inhibition data. A combination of multiple serological assays is required for accurate vaccine evaluation and antigenic analysis of influenza viruses.

410. Influence of Pre-season Antibody Titers to Influenza on Influenza Risk in a Cohort of Healthcare Personnel

BackgroundInfluenza (flu) and other respiratory viruses circulate regularly throughout healthcare systems, often placing healthcare personnel (HCP) at high risk for illness. Hemagglutination inhibition (HAI) titers are associated with protection from flu illness, though few studies have characterized HAI in HCP. The Respiratory Protection Effectiveness Clinical Trial (ResPECT), provided HAI titers and data to assess infection risk based on four flu seasons. Participants from multiple outpatient settings wore respiratory protection within six feet of symptomatic patients.MethodsSerological samples obtained at the beginning and end of each season and anterior nasopharyngeal swabs were taken randomly and when participants reported respiratory symptoms were assessed. Our primary outcome was PCR-confirmed influenza.ResultsDuring 5,180 participant-seasons of observation, 128 PCR-confirmed influenza A infections (20 H1N1, 108 H3N2) and 34 PCR-confirmed influenza B infections. 4,041 (78%) reported receiving an annual influenza vaccine. Each log base 2 increase in titer subtype-specific titer reduced the hazard of influenza infection with A/H3N2 by 18%(Relative Risk (RR) 0.82 95% CI 0.72,0.94), by 28% for influenza B (RR 0.72 95% CI 0.56,0.92 and by 25% for influenza A H1N1 (RR 0.75 95% CI 0.57–1.0). After adjusting for HAI titers, age was not significantly associated with risk for any of the subtypes.ConclusionIn this prospective cohort of monitored HCPs, these findings support the current literature demonstrating that HAI titers are associated with protection from influenza infection. The relationship between HAI titers, influenza, and vaccination is complex, however. Vaccination was not shown to be associated with infection outcome in our model, though their effect may be difficult to separate from their effect on HAI titers.DisclosuresTrish M. Perl, MD, MSc, 7–11: Advisory Board; medimmune: Research Grant.

CAUSES OF DEATH AND DETECTION OF ANTIBODIES AGAINST JAPANESE ENCEPHALITIS VIRUS IN MISAKI FERAL HORSES (EQUUS CABALLUS) IN SOUTHERN JAPAN, 2015–17

We performed postmortem examinations on seven Misaki feral horses (Equus caballus) and evaluated Misaki feral horses, Japanese wild boars (Sus scrofa leucomystax), domestic pigs (Sus scrofa), and wild Japanese macaques (Macaca fuscata fuscata) from 2015 to 2017 in Cape Toi, Kushima, Miyazaki Prefecture, southern Japan, for antibodies against Japanese encephalitis virus (JEV). Strongylus vulgaris infection with severe arterial lesions and hemomelasma ilei was present in all necropsied horses. We frequently found intestinal ulcers, perihepatitis filamentosa, and poor body condition. We recorded degenerative arthropathy in metacarpophalangeal joints in two cases and a fracture of the rib with diaphragmatic rupture in one case. A total of 73% (177/242) of horses were seropositive for JEV as tested by hemagglutination inhibition (HI). The HI data also revealed that 74% (59/80) of the wild boars, 67% (60/90) of the pigs, and 29% (22/75) of the wild monkeys were seropositive for JEV. Our findings showed that Strongylus spp. are still a risk to horses in this region, and that environmental factors such as topographic location of the pasture and steep slope may have caused of degenerative arthropathy and bone fracture. Our results showed that JEV is endemic in Japan. The wild boars and pigs were presumed to act as strong amplifiers and sources of infection, with subsequent risk to humans.

A digital data interpretation method for hemagglutination inhibition assay by using a plate reader

Hemagglutination inhibition (HAI) assay is a simple method quantifying relative binding activities of glycan-lectin interactions. Currently, interpretation of HAI data remains a manual task depending on visual observation. In this study we developed a digital data reading method for HAI assay by using the area scanning function of a microplate reader. This was based on galectin-3-induced hemagglutination inhibition assay. OD values showed a four-parameter logistic correlation with concentrations of galectin-3 inhibitors (R2 ≥ 0.97), and IC50 values were obtained from the curve fitting. The method provides an objective and robust data interpretation for HAI assays conducted with chicken erythrocytes.

Antigenic characterization of H5N1 highly pathogenic avian influenza viruses isolated from poultry in India, 2006-2015.

Highly pathogenic avian influenza (HPAI) is a major health concern worldwide. In this study, we focused on antigenic analysis of HPAI H5N1 viruses isolated from poultry in India between 2006 and 2015 comprising 25 isolates from four phylogenetic clades 2.2 (1 isolate), 2.2.2.1 (1 isolate), 2.3.2.1a (17 isolates) and 2.3.2.1c (6 isolates). Seven H5N1 isolates from all four clades were selected for production of chicken antiserum, and antigenic analysis was carried out by hemagglutination inhibition (HI) assay. HI data indicated antigenic divergence (6-21 fold reduction in cross-reactivity) between the two recently emerged clades 2.3.2.1a and 2.3.2.1c. These two clades are highly divergent (21-128 fold reduction in HI titre) from the earlier clades 2.2 /2.2.2.1 isolated in India. However, a maximum of 2-fold and 4-fold reduction in cross-reactivity was observed within the isolates of homologous clades 2.3.2.1c and 2.3.2.1a, respectively. The molecular basis of inter-clade antigenic divergence was examined in the haemagglutinin (HA) antigenic sites of the H5N1 virus. Amino acid changes at 8 HA antigenic sites were observed between clades 2.3.2.1a and 2.3.2.1c, whereas 20-23 substitutions were observed between clades 2.3.2.1a/2.3.2.1c and 2.2/2.2.2.1. Therefore, a systematic analysis of antigenic drift of the contemporary field isolates is a pre-requisite for determining the suitable strain(s) for vaccine candidature.

Determination of antigenicity-altering patches on the major surface protein of human influenza A/H3N2 viruses.

Human influenza viruses are rapidly evolving RNA viruses that cause short-term respiratory infections with substantial morbidity and mortality in annual epidemics. Uncovering the general principles of viral coevolution with human hosts is important for pathogen surveillance and vaccine design. Protein regions are an appropriate model for the interactions between two macromolecules, but the currently used epitope definition for the major antigen of influenza viruses, namely hemagglutinin, is very broad. Here, we combined genetic, evolutionary, antigenic, and structural information to determine the most relevant regions of the hemagglutinin of human influenza A/H3N2 viruses for interaction with human immunoglobulins. We estimated the antigenic weights of amino acid changes at individual sites from hemagglutination inhibition data using antigenic tree inference followed by spatial clustering of antigenicity-altering protein sites on the protein structure. This approach determined six relevant areas (patches) for antigenic variation that had a key role in the past antigenic evolution of the viruses. Previous transitions between successive predominating antigenic types of H3N2 viruses always included amino acid changes in either the first or second antigenic patch. Interestingly, there was only partial overlap between the antigenic patches and the patches under strong positive selection. Therefore, besides alterations of antigenicity, other interactions with the host may shape the evolution of human influenza A/H3N2 viruses.

Genetic and antigenic characterization of H5N1 viruses of clade 2.3.2.1 isolated in India

The recurrent circulation of highly pathogenic avian influenza (HPAI) H5N1 in Indian poultry since 2006 resulted in emergence of the viruses of distinct antigenic clades of haemagglutinin (HA) with the majority of the H5N1 outbreaks since 2011 belonging to clade 2.3.2.1. The present study was aimed to characterize the antigenic profile of a collection of H5N1 HPAI viruses of clade 2.3.2.1 isolated in India by applying antigenic cartography, serological data and phylogenetic analysis. Eleven H5N1 viruses (2 of clade 2.2 and 9 of clade 2.3.2.1) were selected based on genetic analysis and were further characterized by antigenic cartography analysis based on cross HI (hemagglutination inhibition) data. This study highlights the intercladal antigenic differences between clades 2.3.2.1 and 2.2 and the intracladal antigenic divergence among the clade 2.3.2.1 viruses. Five viruses of clade 2.3.2.1 were also studied for analysis of glycosylation pattern of Hemagglutinin (HA) gene and the growth kinetics analysis in MDCK cells in which the viruses CL03485/H5N1 and 03CL488/H5N1 showed better replication kinetics than other viruses. The study presents a baseline data of antigenicity and other factors that can be used in the selection of suitable H5 vaccine strains or HA donor viruses to develop H5 vaccine strains by reverse genetics or other methods for control of currently circulating H5N1 viruses in Indian region.

Antigenic Maps of Influenza A(H3N2) Produced With Human Antisera Obtained After Primary Infection

BackgroundAntigenic characterization of influenza viruses is typically based on hemagglutination inhibition (HI) assay data for viral isolates tested against strain-specific postinfection ferret antisera. Here, similar virus characterizations were performed using serological data from humans with primary influenza A(H3N2) infection.MethodsWe screened sera collected between 1995 and 2011 from children between 9 and 24 months of age for influenza virus antibodies, performed HI tests for the positive sera against 23 influenza viruses isolated between 1989 and 2011, and measured HI titers of antisera against influenza A(H3N2) from 24 ferrets against the same panel of viruses.ResultsOf the 17 positive human sera, 6 had a high response, showing HI patterns that would be expected from primary infection antisera, while 11 sera had lower, more dispersed patterns of reactivity that are not easily explained. The antigenic map based on the high-response human HI data was similar to the map created using ferret data.ConclusionsAlthough the overall structure of the ferret and human antigenic maps is similar, local differences in virus positions indicate that the human and ferret immune system might see antigenic properties of viruses differently. Further studies are needed to establish the degree of similarity between serological patterns in ferret and human data.

Multi-Dimensional Measurement of Antibody-Mediated Heterosubtypic Immunity to Influenza.

The human immune response to influenza vaccination depends in part on preexisting cross-reactive (heterosubtypic) immunity from previous infection by, and/or vaccination with, influenza strains that share antigenic determinants with the vaccine strains. However, current methods for assessing heterosubtypic antibody responses against influenza, including the hemagglutination-inhibition (HAI) assay and ELISA, are time and labor intensive, and require moderate amounts of serum and reagents. To address these issues we have developed a fluorescent multiplex assay, mPlex-Flu, that rapidly and simultaneously measures strain specific IgG, IgA, and IgM antibodies against influenza hemagglutinin (HA) from multiple viral strains. We cloned, expressed and purified HA proteins from 12 influenza strains, and coupled them to multiplex beads. Assay validation showed that minimal sample volumes (<5 μl of serum) were needed, and the assay had a linear response over a four Log10 range. The assay detected nanogram levels of anti-influenza specific antibodies, had high accuracy and reproducibility, with an average percentage coefficient of variation (%CV) of 9.06 for intra-assay and 12.94 for inter-assay variability. Pre- and post-intramuscular trivalent influenza vaccination levels of virus specific Ig were consistent with HAI titer and ELISA measurements. A significant advantage of the mPLEX-Flu assay over the HAI assay is the ability to perform antigenic cartography, determining the antigenic distances between influenza HA’s, without mathematical correction for HAI data issues. For validation we performed antigenic cartography on 14 different post-influenza infection ferret sera assayed against 12 different influenza HA’s. Results were in good agreement with a phylogenetic tree generated from hierarchical clustering of the genomic HA sequences. This is the first report of the use of a multiplex method for antigenic cartography using ferret sera. Overall, the mPlex-Flu assay provides a powerful tool to rapidly assess the influenza antibody repertoire in large populations and to study heterosubtypic immunity induced by influenza vaccination.

Variation in protection of four divergent avian influenza virus vaccine seed strains against eight clade 2.2.1 and 2.2.1.1. Egyptian H5N1 high pathogenicity variants in poultry.

BackgroundHighly pathogenic (HP) H5N1 avian influenza virus (AIV) was introduced to Egyptian poultry in 2006 and has since become enzootic. Vaccination has been utilized as a control tool combined with other control methods, but for a variety of reasons, the disease has not been eradicated. In 2007, an antigenically divergent hemagglutinin subclade, 2.2.1.1, emerged from the original clade 2.2.1 viruses.ObjectivesThe objective was to evaluate four diverse AIV isolates for use as vaccines in chickens, including two commercial vaccines and two additional contemporary isolates, against challenge with numerous clade 2.2.1 and clade 2.2.1.1 H5N1 HPAIV Egyptian isolates to assess the variation in protection among different vaccine and challenge virus combinations.MethodsVaccination-challenge studies with four vaccines and up to eight challenge strains with each vaccine for a total of 25 vaccination-challenge groups were conducted with chickens. An additional eight groups served as sham-vaccinated controls. Mortality, mean death time, morbidity, virus, and pre-challenge antibodies were evaluated as metrics of protection. Hemagglutination inhibition data were used to visualize the antigenic relatedness of the isolates.Results and conclusionsAlthough all but one vaccine-challenge virus combination significantly reduced shed and mortality as compared to sham vaccinates, there were differences in protection among the vaccines relative to one another based on challenge virus. This emphasizes the difficulty in vaccinating against diverse, evolving virus populations, and the importance of selecting optimal vaccine seed strains for successful HPAIV control.

Integrating influenza antigenic dynamics with molecular evolution

Influenza viruses undergo continual antigenic evolution allowing mutant viruses to evade host immunity acquired to previous virus strains. Antigenic phenotype is often assessed through pairwise measurement of cross-reactivity between influenza strains using the hemagglutination inhibition (HI) assay. Here, we extend previous approaches to antigenic cartography, and simultaneously characterize antigenic and genetic evolution by modeling the diffusion of antigenic phenotype over a shared virus phylogeny. Using HI data from influenza lineages A/H3N2, A/H1N1, B/Victoria and B/Yamagata, we determine patterns of antigenic drift across viral lineages, showing that A/H3N2 evolves faster and in a more punctuated fashion than other influenza lineages. We also show that year-to-year antigenic drift appears to drive incidence patterns within each influenza lineage. This work makes possible substantial future advances in investigating the dynamics of influenza and other antigenically-variable pathogens by providing a model that intimately combines molecular and antigenic evolution. DOI: http://dx.doi.org/10.7554/eLife.01914.001.

A joint matrix completion and filtering model for influenza serological data integration.

Antigenic characterization based on serological data, such as Hemagglutination Inhibition (HI) assay, is one of the routine procedures for influenza vaccine strain selection. In many cases, it would be impossible to measure all pairwise antigenic correlations between testing antigens and reference antisera in each individual experiment. Thus, we have to combine and integrate the HI tables from a number of individual experiments. Measurements from different experiments may be inconsistent due to different experimental conditions. Consequently we will observe a matrix with missing data and possibly inconsistent measurements. In this paper, we develop a new mathematical model, which we refer to as Joint Matrix Completion and Filtering, for HI data integration. In this approach, we simultaneously handle the incompleteness and uncertainty of observations by assuming that the underlying merged HI data matrix has low rank, as well as carefully modeling different levels of noises in each individual table. An efficient blockwise coordinate descent procedure is developed for optimization. The performance of our approach is validated on synthetic and real influenza datasets. The proposed joint matrix completion and filtering model can be adapted as a general model for biological data integration, targeting data noises and missing values within and across experiments.

Use of Antigenic Cartography in Vaccine Seed Strain Selection

Human influenza A viruses are classic examples of antigenically variable pathogens that have a seemingly endless capacity to evade the host's immune response. The viral hemagglutinin (HA) and neuraminidase (NA) proteins are the main targets of our antibody response to combat infections. HA and NA continuously change to escape from humoral immunity, a process known as antigenic drift. As a result of antigenic drift, the human influenza vaccine is updated frequently. The World Health Organization (WHO) coordinates a global influenza surveillance network that, by the hemagglutination inhibition (HI) assay, routinely characterizes the antigenic properties of circulating strains in order to select new seed viruses for such vaccine updates. To facilitate a quantitative interpretation and easy visualization of HI data, a new computational technique called "antigenic cartography" was developed. Since its development, antigenic cartography has been applied routinely to assist the WHO with influenza surveillance activities. Until recently, antigenic variation was not considered a serious issue with influenza vaccines for poultry. However, because of the diversification of the Asian H5N1 lineage since 1996 into multiple genetic clades and subclades, and because of the long-term use of poultry vaccines against H5 in some parts of the world, this issue needs to be re-addressed. The antigenic properties of panels of avian H5N1 viruses were characterized by HI assay, using mammalian or avian antisera, and analyzed using antigenic cartography methods. These analyses revealed antigenic differences between circulating H5N1 viruses and the H5 viruses used in poultry vaccines. Considerable antigenic variation was also observed within and between H5N1 clades. These observations have important implications for the efficacy and long-term use of poultry vaccines.

Genetic analysis of H3N2 influenza A viruses isolated in 2006–2007 in Nairobi, Kenya

Minimal influenza surveillance has been carried out in sub-Saharan Africa to provide information on circulating influenza subtypes for the purpose of vaccine production and monitoring trends in virus spread and mutations. The aim of this study was to investigate a surveillance program in Kenya to isolate and characterize influenza viruses. In the 2006-2007 influenza season, nine influenza A viruses were isolated. All were of H3N2 subtype with key amino acid (aa) changes indicating that they were more closely related to recent World Health Organization recommended vaccine strains than to older vaccine strains, and mirroring the evolution of circulating influenza A globally. Hemagglutination inhibition data showed that the 2006 Kenya isolates had titers identical to the 2005-2006 H3N2 vaccine strain but two- to threefold lower titers to the 2006-2007 vaccine strain, suggesting that the isolates were antigenic variants of the 2006-2007 vaccine strains. Analysis of aa substitutions of hemagglutinin-1 (HA1) protein of the 2006 Kenyan viruses revealed unique genetic variations with several aa substitutions located at immunodominant epitopes of the HA1 protein. These mutations included the V112I change at site E, the K 173 E substitution at site D and N 278 K change at site C, mutations that may result in conformational change on the HA molecule to expose novel epitopes thus abrogating binding of pre-existing antibodies at these sites. Characterization of these important genetic variations in influenza A viruses isolated from Kenya highlights the importance of continuing surveillance and characterization of emerging influenza drift variants in sub-Saharan Africa.

Blocking of Pseudomonas aeruginosa lectins by human milk glycans.

The opportunistic human pathogen Pseudomonas aeruginosa produces a D-galactophilic (PA-IL) lectin and another lectin (PA-IIL) that binds L-fucose > D-arabinose > D-mannose in close association with its host-attacking factors. These lectins contribute to the virulence of P. aeruginosa by their involvement in the production, adhesion, and pathogenic effects of its biofilm on host cells. Therefore, they are considered targets for anti-Pseudomonas therapy. The present study compares their blocking by human milk samples with that of the plant lectin Con A. It demonstrates that human milk inhibits the hemagglutinating activities of the three lectins, with PA-IIL much more strongly inhibited than PA-IL or Con A. Using these lectins, Western blots of the milk samples accord with the hemagglutination inhibition data and disclose the distribution of the human milk glycoproteins that inhibit each lectin. The data of this paper reveal the high efficiency of human milk components in blocking the P. aeruginosa lectins and the usefulness of these lectins for detecting milk glycoprotein saccharides, which may protect the infant against infections.