scholarly journals SARS-CoV-2 spike conformation determines plasma neutralizing activity

2021 ◽  
Author(s):  
John E Bowen ◽  
Alexandra C Walls ◽  
Anshu Joshi ◽  
Kaitlin R Sprouse ◽  
Cameron Stewart ◽  
...  
Keyword(s):  
Antibody Responses ◽  
Specific Antibodies ◽  
Neutralizing Activity ◽  
Cross Neutralization ◽  
Almost All ◽  
Physical Stabilization ◽  
Globally Distributed

Numerous safe and effective COVID-19 vaccines have been developed that utilize various delivery technologies and engineering strategies. The influence of the SARS-CoV-2 spike (S) glycoprotein conformation on antibody responses induced by vaccination or infection in humans remains unknown. To address this question, we compared plasma antibodies elicited by six globally-distributed vaccines or infection and observed markedly higher binding titers for vaccines encoding a prefusion-stabilized S relative to other groups. Prefusion S binding titers positively correlated with plasma neutralizing activity, indicating that physical stabilization of the prefusion conformation enhances protection against SARS-CoV-2. We show that almost all plasma neutralizing activity is directed to prefusion S, in particular the S1 subunit, and that variant cross-neutralization is mediated solely by RBD-specific antibodies. Our data provide a quantitative framework for guiding future S engineering efforts to develop vaccines with higher resilience to the emergence of variants and longer durability than current technologies.

scholarly journals Cervicovaginal Neutralizing Antibodies to Herpes Simplex Virus (HSV) in Women Seropositive for HSV Types 1 and 2

2003 ◽  
Vol 10 (3) ◽  
pp. 388-393 ◽  
Author(s):  
Francois-Xavier Mbopi-Kéou ◽  
Laurent Bélec ◽  
Julie Dalessio ◽  
Jérôme Legoff ◽  
Gérard Grésenguet ◽  
...  
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Neutralizing Antibodies ◽  
Female Genital Tract ◽  
African Women ◽  
Specific Antibodies ◽  
Neutralizing Activity ◽  
Simplex Virus ◽  
Hiv Negative ◽  
Hsv 1

ABSTRACT Antibodies to herpes simplex virus type 1 (HSV-1) and HSV-2 of the immunoglobulin G (IgG) and IgA isotypes were detected in the cervicovaginal secretions (CVS) of 77 HSV-1- and HSV-2-seropositive but clinically asymptomatic African women by type-specific enhanced chemiluminescence Western blotting (ECL-WB). Of the 77 subjects, 34 were HIV negative, shedding HSV-2 DNA in their genital secretions; 20 were HIV positive, shedding HSV-2 DNA; and 23 were HIV negative, not shedding HSV-2 DNA. HSV-specific IgG was detected in CVS of nearly 70% of the women studied. HSV-specific IgA was found in CVS of 50% of the women studied. The distribution of CVS HSV-specific antibodies to each HSV type was highly heterogeneous, with a slight predominance of detectable IgG to HSV-1 (59%) over IgG to HSV-2 (41%), whereas the frequency of detectable IgA to HSV-1 (39%) was similar to that of IgA to HSV-2 (36%). The presence of detectable HSV-specific antibodies was inversely associated with HSV-2 DNA genital asymptomatic shedding but was not affected by HIV seropositivity. In addition, 13 of 77 (17%) CVS samples showed neutralizing activity against HSV-2, as assessed by an HSV-2 in vitro infectivity reduction assay. Neutralizing activity in CVS was associated with the presence of IgG and/or IgA antibodies to HSV-1 and/or to HSV-2 by ECL-WB. Among women whose CVS showed HSV-2-neutralizing activity, the specific activity of HSV-specific neutralizing antibodies was substantially (fivefold) higher in HSV-2 DNA shedders than in nonshedders. In conclusion, HSV-specific antibodies are frequently detected in CVS of asymptomatic African women seropositive for HSV-1 and HSV-2. A subset of these women had functional neutralizing activity against HSV-2 in their CVS. The origin of these antibodies and their role in HSV-2 disease of the female genital tract remain to be determined.

scholarly journals An Optimized High-Throughput Neutralization Assay for Hepatitis E Virus (HEV) Involving Detection of Secreted Porf2

Viruses ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 64 ◽  
Author(s):  
Chang Liu ◽  
Wei Cai ◽  
Xin Yin ◽  
Zimin Tang ◽  
Guiping Wen ◽  
...  
Keyword(s):  
High Throughput ◽  
Hepatitis E Virus ◽  
Hepatitis E ◽  
Neutralization Assay ◽  
The Novel ◽  
Specific Antibodies ◽  
Neutralizing Activity ◽  
Elisa Kit ◽  
Neutralizing Capacity ◽  
Potential Threshold

Hepatitis E virus (HEV) is a common cause of acute hepatitis worldwide. Current methods for evaluating the neutralizing activity of HEV-specific antibodies include immunofluorescence focus assays (IFAs) and real-time PCR, which are insensitive and operationally complicated. Here, we developed a high-throughput neutralization assay by measuring secreted pORF2 levels using an HEV antigen enzyme-linked immunosorbent assay (ELISA) kit based on the highly replicating HEV genotype (gt) 3 strain Kernow. We evaluated the neutralizing activity of HEV-specific antibodies and the sera of vaccinated individuals (n = 15) by traditional IFA and the novel assay simultaneously. A linear regression analysis shows that there is a high degree of correlation between the two assays. Furthermore, the anti-HEV IgG levels exhibited moderate correlation with the neutralizing titers of the sera of vaccinated individuals, indicating that immunization with gt 1 can protect against gt 3 Kernow infection. We then determined specificity of the novel assay and the potential threshold of neutralizing capacity using anti-HEV IgG positive sera (n = 27) and anti-HEV IgG negative sera (n = 23). The neutralizing capacity of anti-HEV IgG positive sera was significantly stronger than that of anti-HEV IgG negative. In addition, ROC curve analysis shows that the potential threshold of neutralizing capacity of sera was 8.07, and the sensitivity and specificity of the novel assay was 88.6% and 100%, respectively. Our results suggest that the neutralization assay using the antigen ELISA kit could be a useful tool for HEV clinical research.

scholarly journals Convergent Antibody Responses to SARS-CoV-2 Infection in Convalescent Individuals

2020 ◽  
Author(s):  
Davide F. Robbiani ◽  
Christian Gaebler ◽  
Frauke Muecksch ◽  
Julio C. C. Lorenzi ◽  
Zijun Wang ◽  
...  
Keyword(s):  
Virus Entry ◽  
Protein S ◽  
Memory B Cells ◽  
Antibody Responses ◽  
Spike Protein ◽  
Human Antibody ◽  
Receptor Binding Domain ◽  
Single Digit ◽  
Specific Antibodies ◽  
Specific Memory

AbstractDuring the COVID-19 pandemic, SARS-CoV-2 infected millions of people and claimed hundreds of thousands of lives. Virus entry into cells depends on the receptor binding domain (RBD) of the SARS-CoV-2 spike protein (S). Although there is no vaccine, it is likely that antibodies will be essential for protection. However, little is known about the human antibody response to SARS-CoV-21–5. Here we report on 149 COVID-19 convalescent individuals. Plasmas collected an average of 39 days after the onset of symptoms had variable half-maximal neutralizing titers ranging from undetectable in 33% to below 1:1000 in 79%, while only 1% showed titers >1:5000. Antibody cloning revealed expanded clones of RBD-specific memory B cells expressing closely related antibodies in different individuals. Despite low plasma titers, antibodies to three distinct epitopes on RBD neutralized at half-maximal inhibitory concentrations (IC50s) as low as single digit ng/mL. Thus, most convalescent plasmas obtained from individuals who recover from COVID-19 do not contain high levels of neutralizing activity. Nevertheless, rare but recurring RBD-specific antibodies with potent antiviral activity were found in all individuals tested, suggesting that a vaccine designed to elicit such antibodies could be broadly effective.

scholarly journals Development and validation of an assay for detection of Japanese Encephalitis virus specific antibody responses

2020 ◽  
Author(s):  
Pradeep Darshana Pushpakumara ◽  
Chandima Jeewandara ◽  
Laksiri Gomes ◽  
Yashodha Perera ◽  
Ananda Wijewickrama ◽  
...  
Keyword(s):  
Immune Responses ◽  
Japanese Encephalitis Virus ◽  
Disease Severity ◽  
Japanese Encephalitis ◽  
Specific Antibody ◽  
Encephalitis Virus ◽  
Antibody Responses ◽  
Specific Antibodies ◽  
Dengue Disease ◽  
Conserved Regions

AbstractBackgroundAlthough immune responses to the Japanese Encephalitis virus (JEV), and the dengue viruses (DENV) have a potential to modulate the immune responses to each other, this has been poorly investigated. Therefore, we developed an ELISA to identify JEV specific, DENV non cross-reactive antibody responses by identifying JEV specific, highly conserved regions of the virus and proceeded to investigate if the presence of JEV specific antibodies associate with dengue disease severity.Methodology/Principal findings20 JEV specific peptides were identified from highly conserved regions of the virus and the immunogenicity and specificity of these peptides were assessed in individuals who were non-immune to JEV and DENV (JEV-DENV-, N=30), those who were only immune to the JEV and not DENV (JEV+DENV-, N=30), those who were only immune to DENV(JEV-DENV+, N=30) and in those who were immune to both viruses (JEV+DENV+, N=30). 7/20 peptides were found to be highly immunogenic and specific and these 7 peptides were used as a pool to further evaluate JEV-specific responses. All 30/30 JEV+DENV-and 30/30 JEV+DENV+individuals, and only 3/30 (10%) JEV-DENV+individuals responded to this pool. We further evaluated this pool of 7 peptides in patients following primary and secondary dengue infection during the convalescent period and found that the JEV-specific peptides, were unlikely to cross react with DENV IgG antibodies. We further compared this in-house ELISA developed with the peptide pool with an existing commercial JEV IgG assay to identify JEV-specific IgG following vaccination, and our in-house ELISA was found to be more sensitive. We then proceeded to investigate if the presence of JEV-specific antibodies were associated with dengue disease severity, and we found that those who had past severe dengue (n=175) were significantly more likely (p<0.0001) to have JEV-specific antibodies than those with past non-severe dengue (n=175) (OR 5.3, 95% CI 3.3 to 8.3).Conclusions/SignificanceAs our data show that this assay is highly sensitive and specific for detection of JEV-specific antibody responses, it would be an important tool to determine how JEV seropositivity modulate dengue immunity and disease severity when undertaking dengue vaccine trials.Author summaryBoth Japanese Encephalitis virus (JEV), and the dengue viruses (DENV) co-circulate in the same geographical region and have a potential to modulate the immune responses to each other. However, due to the difficulty in identifying antibody responses specific to either virus due to the highly cross-reactive nature of virus-specific antibodies, this has been poorly investigated. Therefore, we developed an ELISA to identify JEV-specific, DENV non cross-reactive antibody responses by identifying JEV-specific, highly conserved regions of the virus and proceeded to investigate if the presence of JEV-specific antibodies associates with dengue disease severity. 20 JEV-specific peptides were identified from highly conserved regions of the virus and the immunogenicity and specificity of these peptides were assessed. We found that seven peptides were highly immunogenic and specific to the JEV and we further evaluated the usefulness of an ELISA developed using these pools of peptides. We found that our in-house ELISA was found to be significantly more sensitive some of the existing commercial assays. As this assay appears to be highly sensitive and specific for detection of JEV-specific antibody responses, it would be an important tool to determine how JEV seropositivity modulate dengue immunity and disease severity when undertaking dengue vaccine trials.

Immunity and Protection – Basic Considerations

2021 ◽  
Author(s):  
Heinz-Josef Schmitt
Keyword(s):  
T Cells ◽  
Real Life ◽  
Booster Vaccination ◽  
Immune Memory ◽  
Specific Antibodies ◽  
Cell Immunity ◽  
Time Of Infection ◽  
Individual Protection ◽  
Functional Antibodies ◽  
Almost All

Innate and adaptive immunity generate pathogen-specific antibodies and cells as basis for the efficacy and effectiveness of vaccines: immunity results in protection. For almost all currently licensed vaccines, functional antibodies are the most relevant mechanism of action; they work by binding of an antigen, agglutination, neutralization, complement activation and opsonization directed against specific pathogens or toxins. Immune memory generated by either infection or vaccine priming allows rapid production of antibodies and immune cells (3-7 days) upon later re-infection or (booster-) vaccination. Vaccine-induced immunity may result in protection even in the absence of any measurable specific antibodies at the time of infection – due to memory cells, and due to the effects of T-cells. CD4+ T-cells (“T-helper cells”) induce protection largely by cytokine production, CD8+ T-cells can directly or indirectly kill infected or cancerous cells and they can help clear infections. While antibodies against vaccine antigens can easily be measured by a variety of methods, testing for specific T-cell immunity is less well standardized and more difficult to perform. The term “seroprotection” indicates a serological value (e.g. a titre), associated with protection used for the purpose of vaccine licensure. Measurements of seroprotection can be the percentage of seroresponders, GMTs, fold rise of antibodies or RCD curves. In real life, many factors may contribute to individual protection in both, a positive and a negative direction, including factors inherent with the infecting pathogen, epidemiological factors, host factors, and characteristics of the vaccine and vaccination. Unlike general public belief, the “failure to vaccinate” is more relevant than “vaccine failures” in a population.

scholarly journals High Epstein-Barr Virus Load and Genomic Diversity Are Associated with Generation of gp350-Specific Neutralizing Antibodies following Acute Infectious Mononucleosis

2016 ◽  
Vol 91 (1) ◽  
Author(s):  
Eric R. Weiss ◽  
Galit Alter ◽  
Javier Gordon Ogembo ◽  
Jennifer L. Henderson ◽  
Barbara Tabak ◽  
...  
Keyword(s):  
Peripheral Blood ◽  
Neutralizing Antibodies ◽  
Epstein Barr Virus ◽  
Antibody Responses ◽  
Specific Antibodies ◽  
Barr Virus ◽  
Ebv Infection ◽  
Epstein Barr ◽  
Acute Infectious Mononucleosis ◽  
Major Target

ABSTRACT The Epstein-Barr virus (EBV) gp350 glycoprotein interacts with the cellular receptor to mediate viral entry and is thought to be the major target for neutralizing antibodies. To better understand the role of EBV-specific antibodies in the control of viral replication and the evolution of sequence diversity, we measured EBV gp350-specific antibody responses and sequenced the gp350 gene in samples obtained from individuals experiencing primary EBV infection (acute infectious mononucleosis [AIM]) and again 6 months later (during convalescence [CONV]). EBV gp350-specific IgG was detected in the sera of 17 (71%) of 24 individuals at the time of AIM and all 24 (100%) individuals during CONV; binding antibody titers increased from AIM through CONV, reaching levels equivalent to those in age-matched, chronically infected individuals. Antibody-dependent cell-mediated phagocytosis (ADCP) was rarely detected during AIM (4 of 24 individuals; 17%) but was commonly detected during CONV (19 of 24 individuals; 79%). The majority (83%) of samples taken during AIM neutralized infection of primary B cells; all samples obtained at 6 months postdiagnosis neutralized EBV infection of cultured and primary target cells. Deep sequencing revealed interpatient gp350 sequence variation but conservation of the CR2-binding site. The levels of gp350-specific neutralizing activity directly correlated with higher peripheral blood EBV DNA levels during AIM and a greater evolution of diversity in gp350 nucleotide sequences from AIM to CONV. In summary, we conclude that the viral load and EBV gp350 diversity during early infection are associated with the development of neutralizing antibody responses following AIM. IMPORTANCE Antibodies against viral surface proteins can blunt the spread of viral infection by coating viral particles, mediating uptake by immune cells, or blocking interaction with host cell receptors, making them a desirable component of a sterilizing vaccine. The EBV surface protein gp350 is a major target for antibodies. We report the detection of EBV gp350-specific antibodies capable of neutralizing EBV infection in vitro. The majority of gp350-directed vaccines focus on glycoproteins from lab-adapted strains, which may poorly reflect primary viral envelope diversity. We report some of the first primary gp350 sequences, noting that the gp350 host receptor binding site is remarkably stable across patients and time. However, changes in overall gene diversity were detectable during infection. Patients with higher peripheral blood viral loads in primary infection and greater changes in viral diversity generated more efficient antibodies. Our findings provide insight into the generation of functional antibodies, necessary for vaccine development.

Analysis of Spontaneous Vs. Vaccine-Induced Antibody Responses Against Cancer-Testis Antigen MAGE-A3 in Cancer Patients

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 5087-5087
Author(s):  
Yanran Cao ◽  
Sacha Gnjatic ◽  
Vincent G. Brichard ◽  
Tim Luetkens ◽  
Sebastian Kobold ◽  
...  
Keyword(s):  
T Cell ◽  
Immune Responses ◽  
Cancer Patients ◽  
Peripheral Blood ◽  
Memory B Cells ◽  
Antibody Responses ◽  
Specific Antibodies ◽  
Fine Specificity ◽  
Specific Memory ◽  
Cancer Testis

Abstract Abstract 5087 Background: Cancer-testis antigens (CTA) are attractive targets for cancer immunotherapy based on their tumor-restricted expression and immunogenicity. A number of CTA, including Melanoma-associated antigen 3 (MAGE-A3), are already under clinical investigation and CTA have been shown to induce strong T cell and humoral immunity in cancer patients receiving active immunotherapy. However, little is known about the fine specificity and the function of vaccine-induced humoral immune responses and it is unclear how they relate to spontaneous CTA-specific immune responses occurring in a minority of patients. Methods: We have performed a longitudinal analysis of spontaneously occurring antibody responses against the CT antigen MAGE-A3 in sera (N=1537), which were collected from patients with multiple myeloma (N=355) over a period of 6 years. Antibody titers were determined by ELISA technique and a B cell ELISPOT assay was applied to estimate the number of MAGEA3-specific memory B cells in peripheral blood of the patients. Fine specificity of the antibody responses was examined using overlapping 20mer peptides spanning the whole sequence of MAGE-A3. The given IgG subtype was determined, and the quality of MAGE-A3-specific antibodies was analyzed using western blot as well as affinity assays. Results were compared to those obtained with MAGE-A3-specific antibody responses induced by vaccination with full-length MAGE-A3 protein and adjuvants AS02B or AS15 in patients with non-small cell lung cancer (NSCLC; N=15). Results: Out of 355 myeloma patients 4 (1.1%) evidenced spontaneous antibody responses against MAGE-A3 at least at one point during the course of their disease. Spontaneously occurring anti-MAGE-A3 humoral responses were usually of low titer. In contrast, all of the vaccinated patients showed high-titered and persisting antibody responses which usually appeared around week 6 after the first application of the vaccine. Accordingly, we found high frequencies of vaccine-induced MAGE-A3-specific memory B cells in the peripheral blood of NSCLC patients while they remained undetectable in most myeloma patients. Vaccine-induced antibody responses underwent affinity maturation reaching affinity levels of spontaneous immune responses after repeated cycles of treatment. MAGE-A3-specific antibodies consisted of IgG1 and IgG3>IgG2>IgG4 subtypes in vaccinated patients whereas spontaneously occurring antibodies were mainly of the IgG2 subtype. Spontaneous as well as vaccine-induced IgG antibodies both recognized the natural full-length protein. Analysis of the fine specificity of the antibody responses revealed that vaccine-induced antibodies recognized a much larger number of MAGE-A3 epitopes than spontaneously occurring antibodies. However, both, spontaneous as well as vaccine-induced responses, most frequently and strongly recognized a specific region within the MAGE-A3 protein corresponding to amino acids 51–70. Conclusions This study demonstrates for the first time important qualitative differences between spontaneously occurring and vaccine-induced antibody responses against the MAGE-A3 antigen in cancer patients. While the potential of both types of antibody responses to promote antigen uptake and induction of T cell responses by antigen-presenting cells might differ, they both recognized the same restricted region within the MAGE-A3 protein. The latter finding might be of importance for the design of future immunotherapies targeting MAGE-A3. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Enhancement of neutralizing activity of influenza virus-specific antibodies by serum components

Virology ◽  
2006 ◽  
Vol 352 (2) ◽  
pp. 418-426 ◽  
Author(s):  
Krystyna Mozdzanowska ◽  
JingQi Feng ◽  
Mark Eid ◽  
Darya Zharikova ◽  
Walter Gerhard
Keyword(s):  
Influenza Virus ◽  
Specific Antibodies ◽  
Neutralizing Activity ◽  
Serum Components

scholarly journals Antibody responses to rhesus cytomegalovirus glycoprotein B in naturally infected rhesus macaques

2003 ◽  
Vol 84 (12) ◽  
pp. 3371-3379 ◽  
Author(s):  
Yujuan Yue ◽  
Shan Shan Zhou ◽  
Peter A. Barry
Keyword(s):  
Specific Antibody ◽  
Transmembrane Domain ◽  
Solid Phase ◽  
Rhesus Macaques ◽  
Antibody Responses ◽  
Full Length ◽  
Glycoprotein B ◽  
Primate Model ◽  
Specific Antibodies ◽  
Rhesus Cytomegalovirus

Rhesus cytomegalovirus (RhCMV) exhibits strong parallels with human CMV (HCMV) in terms of nucleic and amino acid identities, natural history, and mechanisms of persistence and pathogenesis in its natural host, rhesus macaques (Macaca mulatta). To determine whether this non-human primate model would be useful to assess vaccine strategies for HCMV, host immune responses to RhCMV glycoprotein B (gB) were evaluated in RhCMV-infected monkeys. Total protein extracts were prepared from cells transiently transfected with an expression plasmid for either the full-length gB or a derivative (gBΔ, 1–680 aa) lacking both the transmembrane domain and cytoplasmic tail. Western blot analysis showed identical reactivity of macaque sera with full-length gB and its derivative gBΔ, indicating that the immunodominant epitopes of gB are contained in the extracellular portion of the protein. Using gBΔ extract as a solid phase, a sensitive and specific ELISA was established to characterize gB antibody responses in monkeys acutely and chronically infected with RhCMV. During primary infection (seroconversion), gB-specific antibodies developed concurrently and in parallel with total RhCMV-specific antibodies. However, during chronic infection gB-specific antibody responses were variable. A strong correlation was observed between neutralizing and gB-specific antibody levels in RhCMV-seropositive monkeys. Taken together, the results of this study indicate that, similar to host humoral responses to HCMV gB, anti-gB antibodies are an integral part of humoral immunity to RhCMV infection and probably play an important protective role in limiting the extent of RhCMV infection. Thus, the rhesus macaque model of HCMV infection is relevant for testing gB-based immune therapies.

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