The effectiveness of the annual influenza vaccine has declined in recent years, especially for the H3N2 component, and is a concern for global public health. A major cause for this lack in ...effectiveness has been attributed to the egg-based vaccine production process. Substitutions on the hemagglutinin glycoprotein (HA) often arise during virus passaging that change its antigenicity and hence vaccine effectiveness. Here, we characterize the effect of a prevalent substitution, L194P, in egg-passaged H3N2 viruses. X-ray structural analysis reveals that this substitution surprisingly increases the mobility of the 190-helix and neighboring regions in antigenic site B, which forms one side of the receptor binding site (RBS) and is immunodominant in recent human H3N2 viruses. Importantly, the L194P substitution decreases binding and neutralization by an RBS-targeted broadly neutralizing antibody by three orders of magnitude and significantly changes the HA antigenicity as measured by binding of human serum antibodies. The receptor binding mode and specificity are also altered to adapt to avian receptors during egg passaging. Overall, these findings help explain the low effectiveness of the seasonal vaccine against H3N2 viruses, and suggest that alternative approaches should be accelerated for producing influenza vaccines as well as isolating clinical isolates.
•Early viral infections shape B cell response recalled against future viral strains.•Competition between memory and naïve B cells occurs in secondary viral exposures.•Antibodies become focused on ...epitopes conserved in past influenza virus strains.•Focused antibody responses fail to protect against mutated viral strains.
Antibody responses to influenza viruses are critical for protection, but the ways in which repeated viral exposures shape antibody evolution and effectiveness over time remain controversial. Early observations demonstrated that viral exposure history has a profound effect on the specificity and magnitude of antibody responses to a new viral strain, a phenomenon called ‘original antigenic sin.’ Although ‘sin’ might suppress some aspects of the immune response, so far there is little indication that hosts with pre-existing immunity are more susceptible to viral infections compared to naïve hosts. However, the tendency of the immune response to focus on previously recognized conserved epitopes when encountering new viral strains can create an opportunity cost when mutations arise in these conserved epitopes. Hosts with different exposure histories may continue to experience distinct patterns of infection over time, which may influence influenza viruses’ continued antigenic evolution. Understanding the dynamics of B cell competition that underlie the development of antibody responses might help explain the low effectiveness of current influenza vaccines and lead to better vaccination strategies.
Identifying viral mutations that confer escape from antibodies is crucial for understanding the interplay between immunity and viral evolution. We describe a high-throughput approach to quantify the ...selection that monoclonal antibodies exert on all single amino-acid mutations to a viral protein. This approach, mutational antigenic profiling, involves creating all replication-competent protein variants of a virus, selecting with antibody, and using deep sequencing to identify enriched mutations. We use mutational antigenic profiling to comprehensively identify mutations that enable influenza virus to escape four monoclonal antibodies targeting hemagglutinin, and validate key findings with neutralization assays. We find remarkable mutation-level idiosyncrasy in antibody escape: for instance, at a single residue targeted by two antibodies, some mutations escape both antibodies while other mutations escape only one or the other. Because mutational antigenic profiling rapidly maps all mutations selected by an antibody, it is useful for elucidating immune specificities and interpreting the antigenic consequences of viral genetic variation.
Influenza vaccines must be updated regularly because influenza viruses continuously acquire mutations in antibody binding sites of hemagglutinin (HA). The majority of H3N2 strains circulating in the ...Northern Hemisphere during the 2014–2015 season are antigenically mismatched to the A/Texas/50/2012 H3N2 vaccine strain. Recent H3N2 strains possess several new HA mutations, and it is unknown which of these mutations contribute to the 2014–2015 vaccine mismatch. Here, we use reverse genetics to demonstrate that mutations in HA antigenic site B are primarily responsible for the current mismatch. Sera isolated from vaccinated humans and infected ferrets and sheep had reduced hemagglutination inhibition and in vitro neutralization titers against reverse-genetics-derived viruses possessing mutations in the HA antigenic site B. These data provide an antigenic explanation for the low influenza vaccine efficacy observed during the 2014–2015 influenza season. Furthermore, our data support the World Health Organization’s decision to update the H3N2 component of future vaccine formulations.
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•Recent H3N2 strains are antigenically distinct in comparison to the 2014–2015 vaccine strain•Most humans produce antigenic site B HA antibodies•New mutations in antigenic site B of HA likely led to 2014–2015 vaccine mismatch
Most H3N2 influenza viruses circulating during the 2014–2015 influenza season were antigenically mismatched to the H3N2 component of the 2014–2015 influenza vaccine. Chambers et al. use reverse genetics to identify the hemagglutinin mutations responsible for this antigenic mismatch.
Human antibodies (Abs) elicited by influenza viruses often bind with a high affinity to past influenza virus strains, but paradoxically, do not bind to the viral strain actually eliciting the ...response. This phenomena is called 'original antigenic sin' (OAS) since this can occur at the expense of generating new de novo Abs. Here, we characterized the specificity and functionality of Abs elicited in mice that were sequentially exposed to two antigenically distinct H1N1 influenza virus strains. Many Abs elicited under these conditions had an OAS phenotype, in that they bound strongly to the viral strain used for the first exposure and very weakly to the viral strain used for the second exposure. We found that OAS and non-OAS Abs target the same general region of the influenza hemagglutinin protein and that B cells expressing these two types of Abs can be clonally-related. Surprisingly, although OAS Abs bound with very low affinities, some were able to effectively protect against an antigenically drifted viral strain following passive transfer in vivo. Taken together, our data indicate that OAS Abs share some level of cross-reactivity between priming and recall viral strains and that B cells producing these Abs can be protective when recalled into secondary immune responses.
Abstract
Influenza viruses routinely acquire mutations in their hemagglutinin (HA) and neuraminidase (NA) glycoproteins that abrogate binding of pre-existing antibodies in a process known as ...antigenic drift. Most human antibodies against HA and NA are directed against epitopes that are hypervariable and not against epitopes that are conserved among different influenza virus strains. Universal influenza vaccines are currently being developed to elicit protective responses against functionally conserved sites on influenza proteins where viral escape mutations can result in large fitness costs 1. Universal vaccine targets include the highly conserved HA stem domain 2–12, the less conserved HA receptor-binding site (RBS) 13–16, as well as conserved sites on NA 17–19. One central challenge of universal vaccine efforts is to steer human antibody responses away from immunodominant, variable epitopes and towards subdominant, functionally conserved sites. Overcoming this challenge will require further understanding of the structural basis of broadly neutralizing HA and NA antibody binding epitopes and factors that influence immunodominance hierarchies of human antibody responses.
Currently available influenza virus vaccines have inadequate effectiveness and are reformulated annually due to viral antigenic drift. Thus, development of a vaccine that confers long-term protective ...immunity against antigenically distant influenza virus strains is urgently needed. The highly conserved influenza virus hemagglutinin (HA) stalk represents one of the potential targets of broadly protective/universal influenza virus vaccines. Here, we evaluate a potent broadly protective influenza virus vaccine candidate that uses nucleoside-modified and purified mRNA encoding full-length influenza virus HA formulated in lipid nanoparticles (LNPs). We demonstrate that immunization with HA mRNA-LNPs induces antibody responses against the HA stalk domain of influenza virus in mice, rabbits, and ferrets. The HA stalk-specific antibody response is associated with protection from homologous, heterologous, and heterosubtypic influenza virus infection in mice.
In this work, sulfur-functionalized ordered mesoporous carbons were synthesized by activating the soft-templated mesoporous carbons with sulfur bearing salts that simultaneously enhanced the surface ...area and introduced sulfur functionalities onto the parent carbon surface. XPS analysis showed that sulfur content within the mesoporous carbons were between 8.2% and 12.9%. The sulfur functionalities include C–S, CS, −COS, and SO x . SEM images confirmed the ordered mesoporosity within the material. The BET surface areas of the sulfur-functionalized ordered mesoporous carbons range from 837 to 2865 m2/g with total pore volume of 0.71–2.3 cm3/g. The carbon with highest sulfur functionality was examined for aqueous phase adsorption of mercury (as HgCl2), lead (as Pb(NO3)2), cadmium (as CdCl2), and nickel (as NiCl2) ions in both noncompetitive and competitive mode. Under noncompetitive mode and at a pH greater than 7.0 the affinity of sulfur-functionalized carbons toward heavy metals were in the order of Hg > Pb > Cd > Ni. At lower pH, the adsorbent switched its affinity between Pb and Cd. In the noncompetitive mode, Hg and Pb adsorption showed a strong pH dependency whereas Cd and Ni adsorption did not demonstrate a significant influence of pH. The distribution coefficient for noncompetitive adsorption was in the range of 2448–4000 mL/g for Hg, 290–1990 mL/g for Pb, 550–560 mL/g for Cd, and 115–147 for Ni. The kinetics of adsorption suggested a pseudo-second-order model fits better than other models for all the metals. XPS analysis of metal-adsorption carbons suggested that 7–8% of the adsorbed Hg was converted to HgSO4, 14% and 2% of Pb was converted to PbSO4 and PbS/PbO, respectively, and 5% Cd was converted to CdSO4. Ni was below the detection limit for XPS. Overall results suggested these carbon materials might be useful for the separation of heavy metals.
Coronavirus disease 2019 (COVID-19) is currently a global pandemic, but human immune responses to the virus remain poorly understood. We used high-dimensional cytometry to analyze 125 COVID-19 ...patients and compare them with recovered and healthy individuals. Integrated analysis of ~200 immune and ~50 clinical features revealed activation of T cell and B cell subsets in a proportion of patients. A subgroup of patients had T cell activation characteristic of acute viral infection and plasmablast responses reaching >30% of circulating B cells. However, another subgroup had lymphocyte activation comparable with that in uninfected individuals. Stable versus dynamic immunological signatures were identified and linked to trajectories of disease severity change. Our analyses identified three immunotypes associated with poor clinical trajectories versus improving health. These immunotypes may have implications for the design of therapeutics and vaccines for COVID-19.
SARS-CoV-2 mRNA vaccines have shown remarkable clinical efficacy, but questions remain about the nature and kinetics of T cell priming. We performed longitudinal antigen-specific T cell analyses on ...healthy SARS-CoV-2-naive and recovered individuals prior to and following mRNA prime and boost vaccination. Vaccination induced rapid antigen-specific CD4+ T cell responses in naive subjects after the first dose, whereas CD8+ T cell responses developed gradually and were variable in magnitude. Vaccine-induced Th1 and Tfh cell responses following the first dose correlated with post-boost CD8+ T cells and neutralizing antibodies, respectively. Integrated analysis revealed coordinated immune responses with distinct trajectories in SARS-CoV-2-naive and recovered individuals. Last, whereas booster vaccination improved T cell responses in SARS-CoV-2-naive subjects, the second dose had little effect in SARS-CoV-2-recovered individuals. These findings highlight the role of rapidly primed CD4+ T cells in coordinating responses to the second vaccine dose in SARS-CoV-2-naive individuals.
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•mRNA vaccines generate antigen-specific T cells in a coordinated immune response•Vaccine-induced T cells resemble the durable memory cells primed by infection•Th1 and cTfh cell responses to the first dose correlate with second-dose responses•SARS-CoV-2-recovered individuals benefit from the first but not the second dose
SARS-CoV-2 mRNA vaccines have demonstrated remarkable efficacy, but T cell responses to vaccination have not been well studied. In a longitudinal cohort, Painter et al. show that mRNA vaccines activate SARS-CoV-2-specific T cells that could contribute to durable immunity. The findings highlight the central role of T cells in the two-dose vaccine regimen for individuals not previously infected with SARS-CoV-2.
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