The investigation of the dynamics of changes in neutralizing antibody titers against type 5 adenovirus in the context of vaccination against a new coronavirus infection

This research focuses on analyzing the dynamics of neutralizing antibody (nAbs) titers against type 5 adenovirus (Ad5) in the adult population of Russia following vaccination against the novel coronavirus infection with recombinant adenovirus type-5 COVID-19 vaccine (CanSino Biologics, China). The impact of the Ad5 vector on nAb titers was investigated using 302 blood serum samples from individuals who received a single dose of the Ad5-nCoV vector vaccine. The research revealed that 33.8% of adults in Russia had pre-existing anti-Ad5 nAbs before the pandemic. Notably, 40% of vaccinated individuals did not exhibit an increase in nAbs titers upon receiving the Ad5-based vaccine. However, in the group with no or low titers of anti-Ad5 nAbs (1:10-1:40), a significant 8-16-fold increase in nAb titers to Ad5 was observed.

Cytomegalovirus UL44 protein induces a potent T-cell immune response in mice

Due to the severity of CMV infection in immunocompromised individuals the development of a vaccine has been declared a priority. However, despite the efforts made there is no yet a vaccine available for clinical use. We designed an approach to identify new CMV antigens able to inducing a broad immune response that could be used in future vaccine formulations. We have used serum samples from 28 kidney transplant recipients, with a previously acquired CMV-specific immune response to identify viral proteins that were recognized by the antibodies present in the patient serum samples by Western blot. A band of approximately 45 kDa, identified as UL44, was detected by most serum samples. UL44 immunogenicity was tested in BALB/c mice that received three doses of the UL44-pcDNA DNA vaccine. UL44 elicited both, a strong antibody response and CMV-specific cellular response. Using bioinformatic analysis we demonstrated that UL44 is a highly conserved protein and contains epitopes that are able to activate CD8 lymphocytes of the most common HLA alleles in the world population. We constructed a UL44 ORF deletion mutant virus that produced no viral progeny, suggesting that UL44 is an essential viral protein. In addition, other authors have demonstrated that UL44 is one of the most abundant viral proteins after infection and have suggested an essential role of UL44 in viral replication. Altogether, our data suggests that UL44 is a potent antigen, and favored by its abundance, it may be a good candidate to include in a vaccine formulation.

Vaccination in twin pregnancies: comparison between immunization before conception and during pregnancy

To evaluate the development of neutralizing Anti-Spike Protein IgG (Anti-S-IgG) during twin pregnancies before conception vs. during pregnancy. In this prospective study, three blood samples were collected from pregnant women and subjected to anti-S-IgG immunodiagnostics. The patient's medical records, including vaccination and PCR test results, were collected from the hospital's electronic database. Age-matched non-pregnant women were used as a control group. We enrolled 83 women with twin pregnancies. 49 women were vaccinated before conception, 21 women were vaccinated during pregnancy, and 13 were not vaccinated. Of the 13 women who weren't vaccinated, three became positive during pregnancy, and all three were severely ill. By contrast, in women who were vaccinated during or before pregnancy, COVID-19 infection during pregnancy caused only mild symptoms. A ten-fold lower level of neutralizing Anti-S-IgG in the 3rd trimester was observed in healthy women who were vaccinated before conception and remained healthy until discharge from the hospital after delivery 1605 (IQR: 763-2410) compared to the healthy women who were vaccinated during pregnancy 152 AU/mL (IQR: 54-360). This difference was higher among women who were infected by COVID-19 (as verified by a positive PCR test). The third-trimester level of neutralizing Ant-S-IgG in the infected group was 4770 AU/mL (4760-6100) in infected women vaccinated before conception compared to those vaccinated during pregnancy who had 70 AU/mL (IQR: 20-170) (p < 0.001). In women vaccinated at 13-16 weeks gestation, neutralizing Anti-S-IgG at 20-22 weeks went up to 372 AU/mL (IQR: 120-1598) but rapidly dropped to 112 AU/mL (IQR: 54-357) at 28-30 weeks, (p < 0.001), a faster decline than in women vaccinated at a median 22 weeks before conception. Being infected by COVID-19 before conception was linked to having low Anti-S-IgG levels during pregnancy, whereas being infected by COVID-19 during pregnancy led to a very high response in the 3rd trimester. In twin pregnancies, significantly lower neutralizing Anti-S-IgG levels were observed in women vaccinated during pregnancy compared to those vaccinated before conception, whether infected or not infected by COVID-19. A full course of vaccination before conception is recommended.Trial registration. ClinicalTrials.gov Protocol Registration and Results System (PRS) Receipt Release Date: October 4, 2021. https://clinicaltrials.gov/ ID: NCT04595214.

Broad antibody and T cell responses to Ebola, Sudan, and Bundibugyo ebolaviruses using mono- and multi-valent adjuvanted glycoprotein vaccines

Currently, there are two approved vaccine regimens designed to prevent Ebola virus (EBOV) disease (EVD). Both are virus-vectored, and concerns about cold-chain storage and pre-existing immunity to the vectors warrant investigating additional vaccine strategies. Here, we have explored the utility of adjuvanted recombinant glycoproteins (GPs) from ebolaviruses Zaire (EBOV), Sudan (SUDV), and Bundibugyo (BDBV) for inducing antibody (Ab) and T cell cross-reactivity. Glycoproteins expressed in insect cells were administered to C57BL/6 mice as free protein or bound to the surface of liposomes, and formulated with toll-like receptor agonists CpG and MPLA (agonists for TLR 9 and 4, respectively), with or without the emulsions AddaVax or TiterMax. The magnitude of Ab cross-reactivity in binding and neutralization assays, and T cell cross-reactivity in antigen recall assays, correlated with phylogenetic relatedness. While most adjuvants screened induced IgG responses, a combination of CpG, MPLA and AddaVax emulsion ("IVAX-1") was the most potent and polarized in an IgG2c (Th1) direction. Breadth was also achieved by combining GPs into a trivalent (Tri-GP) cocktail with IVAX-1, which did not compromise antibody responses to individual components in binding and neutralizing assays. Th1 signature cytokines in T cell recall assays were undetectable after Tri-GP/IVAX-1 administration, despite a robust IgG2c response, although administration of Tri-GP on lipid nanoparticles in IVAX-1 elevated Th1 cytokines to detectable levels. Overall, the data indicate an adjuvanted trivalent recombinant GP approach may represent a path toward a broadly reactive, deployable vaccine against EVD.

VLPs generated by the fusion of RSV-F or hMPV-F glycoprotein to HIV-Gag show improved immunogenicity and neutralizing response in mice

Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) vaccines have been long overdue. Structure-based vaccine design created a new momentum in the last decade, and the first RSV vaccines have finally been approved in older adults and pregnant individuals. These vaccines are based on recombinant stabilized pre-fusion F glycoproteins administered as soluble proteins. Multimeric antigenic display could markedly improve immunogenicity and should be evaluated in the next generations of vaccines. Here we tested a new virus like particles-based vaccine platform which utilizes the direct fusion of an immunogen of interest to the structural human immunodeficient virus (HIV) protein Gag to increase its surface density and immunogenicity. We compared, in mice, the immunogenicity of RSV-F or hMPV-F based immunogens delivered either as soluble proteins or displayed on the surface of our VLPs. VLP associated F-proteins showed better immunogenicity and induced superior neutralizing responses. Moreover, when combining both VLP associated and soluble immunogens in a heterologous regimen, VLP-associated immunogens provided added benefits when administered as the prime immunization.

COVID-19 vaccination in cancer patients: Immune responses one year after the third dose

Cancer patients (CPs), being immunosuppressed due to the treatment received or to the disease itself, are more susceptible to infections and their potential complications, showing therefore an increased risk of developing severe COVID-19 compared to the general population. We evaluated the immune responses to anti-SARS-CoV-2 vaccination in patients with solid tumors one year after the administration of the third dose and the effect of cancer treatment on vaccine immunogenicity was assessed. Healthy donors (HDs) were enrolled. Binding and neutralizing antibody (Ab) titers were evaluated using chemiluminescence immunoassay (CLIA) and Plaque Reduction Neutralization Test (PRNT) respectively. T-cell response was analyzed using multiparametric flow cytometry. CPs who were administered three vaccine doses showed lower Ab titers than CPs with four doses and HDs. Overall, a lower cell-mediated response was found in CPs, with a predominance of monofunctional T-cells producing TNFα. Lower Ab titers and a weaker T-cell response were observed in CPs without prior SARS-CoV-2 infection when compared to those with a previous infection. While no differences in the humoral response were found comparing immunotherapy and non-immunotherapy patients, a stronger T-cell response in CPs treated with immunotherapy was observed. Our results emphasize the need of booster doses in cancer patients to achieve a level of protection similar to that observed in healthy donors and underlines the importance of considering the treatment received to reach a proper immune response.

Comprehensive landscape of neutralizing antibody and cell-mediated response elicited by the 1/5 fractional dose of 17DD-YF primary vaccination in adults

The present study aimed at evaluating the YF-specific neutralizing antibody profile besides a multiparametric analysis of phenotypic/functional features of cell-mediated response elicited by the 1/5 fractional dose of 17DD-YF vaccine, administered as a single subcutaneous injection. The immunological parameters of each volunteer was monitored at two time points, referred as: before (Day 0) [Non-Vaccinated, NV(D0)] and after vaccination (Day 30-45) [Primary Vaccinees, PV(D30-45)]. Data demonstrated high levels of neutralizing antibodies for PV(D30-45) leading to a seropositivity rate of 93%. A broad increase of systemic soluble mediators with a mixed profile was also observed for PV(D30-45), with IFN-γ and TNF-α presenting the highest baseline fold changes. Integrative network mapping of soluble mediators showed increased correlation numbers in PV(D30-45) as compared to NV(D0) (532vs398). Moreover, PV(D30-45) exhibited increased levels of Terminal Effector (CD45RA+CCR7-) CD4+ and CD8+ T-cells and Non-Classical memory B-cells (IgD+CD27+). Dimensionality reduction of Mass Cytometry data further support these findings. A polyfunctional cytokine profile (TNF-α/IFN-γ/IL-10/IL-17/IL-2) of T and B-cells was observed upon in vitro antigen recall. Mapping and kinetics timeline of soluble mediator signatures for PV(D30-45) further confirmed the polyfunctional profile upon long-term in vitro culture, mediated by increased levels of IFN-γ and TNF-α along with decreased production of IL-10. These findings suggest novel insights of correlates of protection elicited by the 1/5 fractional dose of 17DD-YF vaccine.

Virus-like particles of louping ill virus elicit potent neutralizing antibodies targeting multimers of viral envelope protein

Louping ill virus (LIV) is a tick-borne flavivirus that predominantly causes disease in livestock, especially sheep in the British Isles. A preventive vaccine, previously approved for veterinary use but now discontinued, was based on an inactivated whole virion that likely provided protection by induction of neutralizing antibodies recognizing the viral envelope (E) protein. A major disadvantage of the inactivated vaccine was the need for high containment facilities for the propagation of infectious virus, as mandated by the hazard group 3 status of the virus. This study aimed to develop high-efficacy non-infectious protein-based vaccine candidates. Specifically, soluble envelope protein (sE), and virus-like particles (VLPs), comprised of the precursor of membrane and envelope proteins, were generated, characterized, and studied for their immunogenicity in mice. Results showed that the VLPs induced more potent virus neutralizing response compared to sE, even though the total anti-envelope IgG content induced by the two antigens was similar. Depletion of anti-monomeric E protein antibodies from mouse immune sera suggested that the neutralizing antibodies elicited by the VLPs targeted epitopes spanning the highly organized structure of multimer of the E protein, whereas the antibody response induced by sE focused on E monomers. Thus, our results indicate that VLPs represent a promising LIV vaccine candidate.

Blood T cell phenotypes correlate with fatigue severity in post-acute sequelae of COVID-19

PURPOSE

Post-acute sequelae of COVID-19 (PASC) affect approximately 10% of convalescent patients. The spectrum of symptoms is broad and heterogeneous with fatigue being the most often reported sequela. Easily accessible blood biomarkers to determine PASC severity are lacking. Thus, our study aimed to correlate immune phenotypes with PASC across the severity spectrum of COVID-19.

METHODS

A total of 176 originally immunonaïve, convalescent COVID-19 patients from a prospective cohort during the first pandemic phase were stratified by initial disease severity and underwent clinical, psychosocial, and immune phenotyping around 10 weeks after first COVID-19 symptoms. COVID-19-associated fatigue dynamics were assessed and related to clinical and immune phenotypes.

RESULTS

Fatigue and severe fatigue were commonly reported irrespective of initial COVID-19 severity or organ-specific PASC. A clinically relevant increase in fatigue severity after COVID-19 was detected in all groups. Neutralizing antibody titers were higher in patients with severe acute disease, but no association was found between antibody titers and PASC. While absolute peripheral blood immune cell counts in originally immunonaïve PASC patients did not differ from unexposed controls, peripheral CD3+CD4+ T cell counts were independently correlated with fatigue severity across all strata in multivariable analysis.

CONCLUSIONS

Patients were at similar risk of self-reported PASC irrespective of initial disease severity. The independent correlation between fatigue severity and blood T cell phenotypes indicates a possible role of CD4+ T cells in the pathogenesis of post-COVID-19 fatigue, which might serve as a blood biomarker.

Prevalence of neutralizing antibodies against SARS-CoV-2 using a rapid serological test in health workers of a Spanish Department of Health in Alicante (Spain) before the booster dose of the vaccine

AIM

To study the prevalence of neutralizing antibodies in healthcare workers and healthcare support personnel after the administration of the second dose of the BNT162b2 vaccine (Pfizer-BioNTech).

MATERIALS AND METHODS

In December 2021, we undertook a study in the Health Department in Orihuela, Alicante (Spain), which consists of 1500 workers. We collected demographic variables about the study participants, and we performed a "point-of-care" immunochromatography test to measure the presence of neutralizing antibodies (OJABIO® SARS-CoV-2 Neutralizing Antibody Detection Kit, manufactured by Wenzhou OJA Biotechnology Co., Ltd. Wenzhou, Zhejiang, China) before the administration of the third dose of the vaccine.

RESULTS

We obtained complete information about 964 (64%) workers, which consisted of 290 men and 674 women. The average age was 45,8 years (min. 18, max. 68) and the average time since the last dose of the vaccine was 40,5 weeks (min. 1,71, max. 47,71). A total of 131 participants (13,5%) had suffered infection by SARS-CoV-2 confirmed using RT-PCR. The proportion of participants who showed presence of neutralizing antibodies was 38,5%. In the multivariable analysis, the time since the last dose of the vaccine (aOR week: 1,07; 95%CI: 1,04; 1,09) and previous infection by SARS-CoV-2 (aOR: 3,7; 95CI: 2,39; 5,63) showed a statistically significant association with the presence of neutralizing antibodies.

CONCLUSIONS

The time since the administration of the last dose of the vaccine and the previous infection by SARS-CoV-2 determined the presence of neutralizing antibodies in 38,5% of the healthcare workers and support workers.

SARS-CoV-2 journey: from alpha variant to omicron and its sub-variants

The COVID-19 pandemic has affected hundreds of millions of individuals and caused more than six million deaths. The prolonged pandemic duration and the continual inter-individual transmissibility have contributed to the emergence of a wide variety of SARS-CoV-2 variants. Genomic surveillance and phylogenetic studies have shown that substantial mutations in crucial supersites of spike glycoprotein modulate the binding affinity of the evolved SARS-COV-2 lineages to ACE2 receptors and modify the binding of spike protein with neutralizing antibodies. The immunological spike mutations have been associated with differential transmissibility, infectivity, and therapeutic efficacy of the vaccines and the immunological therapies among the new variants. This review highlights the diverse genetic mutations assimilated in various SARS-CoV-2 variants. The implications of the acquired mutations related to viral transmission, infectivity, and COVID-19 severity are discussed. This review also addresses the effectiveness of human neutralizing antibodies induced by SARS-CoV-2 infection or immunization and the therapeutic antibodies against the ascended variants.

Effects of mifepristone on adipocyte differentiation in mouse 3T3-L1 cells

BACKGROUND

Both glucocorticoid receptor and peroxisome proliferator-activated receptor-γ (PPARγ) play a critical role in adipocyte differentiation. Mifepristone is not only an antagonist of the glucocorticoid receptor but also an agonist of PPARγ. Therefore, the present study investigated the effect of mifepristone on adipocyte differentiation.

METHODS

Mouse 3T3-L1 cells were used as a model for adipocyte differentiation. The lipid droplet formation was evaluated with Bodipy493/503 staining and the expression of adipocyte markers [adiponectin and adipocyte fatty acid binding protein-4 (Fabp4)] was evaluated with quantitative PCR and immunoblot analyses for indication of adipocyte differentiation. siRNA and neutralizing antibodies were used to elucidate the molecular mechanism of mifepristone-induced adipocyte differentiation. Luciferase reporter assay was used to examine the effect of mifepristone on the promoter activity of PPAR-response element (PPRE). The DNA microarray analysis was used to characterize the transcriptome of the mifepristone-induced adipocytes. In vivo adipogenic effect of mifepristone was examined in mice.

RESULTS

Mifepristone not only enhanced adipocyte differentiation induced by the conventional protocol consisting of insulin, dexamethasone and 3-isobutyl-1-methylxanthine but also induced adipocyte differentiation alone, as evidenced by lipid droplets formation and induction of the expression of adiponectin and Fabp4. These effects were inhibited by an adiponectin-neutralizing antibody and a PPARγ antagonist. Mifepristone activated the promoter activity of PPRE in a manner sensitive to PPARγ antagonist. A principal component analysis (PCA) of DNA microarray data revealed that the mifepristone-induced adipocytes represent some characteristics of the in situ adipocytes in normal adipose tissues to a greater extent than those induced by the conventional protocol. Mifepristone administration induced an increase in the weight of epididymal, perirenal and gluteofemoral adipose tissues.

CONCLUSIONS

Mifepristone alone is capable of inducing adipocyte differentiation in 3T3-L1 cells and adipogenesis in vivo. PPARγ plays a critical role in the mifepristone-induced adipocyte differentiation. Mifepristone-induced adipocytes are closer to the in situ adipocytes than those induced by the conventional protocol. The present study proposes a single treatment with mifepristone as a novel protocol to induce more physiologically relevant adipocytes in 3T3-L1 cells than the conventional protocol.

The impact of existing total anti-toxin B IgG immunity in outcomes of recurrent Clostridioides difficile infection

Late anti-toxin-B humoral immunity acquired after treatment is important for preventing recurrent Clostridioides difficile infection. We prospectively-measured anti-toxin-B IgG and neutralization titers at diagnosis as potential early predictors of recurrence. High anti-toxin-B-IgG/neutralizing antibodies were associated with short-lasting protection within 6-weeks, however, no difference in recurrence risk was observed by 90-days post-infection.

Neutralizing antibody titers against D8 genotype and persistence of measles humoral and cell-mediated immunity eight years after the first dose of measles, mumps, and rubella vaccine in Brazilian children

OBJECTIVE

Assess the level of measles vaccine-induced neutralizing antibodies against the D8 genotype and the persistence of humoral and cell-mediated immunity in children who received their first dose of the measles, mumps, and rubella vaccine eight years previously.

METHODS

Measles-specific IgG and neutralizing antibodies were determined in serum using ELISA and plaque reduction neutralization test, respectively. Cellular response was evaluated from peripheral blood mononuclear cells (PBMC). IFN-γ-secreting cells, memory B and T cells, and immunological mediators were assayed by ELISpot, flow cytometry, and multiplex liquid microarray assay, respectively.

RESULTS

Antibody concentrations declined over time; however, the vaccine-induced neutralizing antibodies' effect against D8 and vaccinal genotypes persisted. PBMC stimulated with the vaccine virus exhibited specific IFN- γ-measles-secreting responses in most participants. Participants with high levels of neutralizing antibodies showed a higher proportion of activated B cells compared to participants with low levels of neutralizing antibodies, while proportions of memory CD4+ and CD8+ T cells were similar between these groups. PBMC supernatant cytokine levels showed a significant difference between stimulated and non-stimulated conditions for IL-2, TNF-α, IL-10, and CXCL10.

CONCLUSION

Despite the decline in antibody concentrations over time, the participants still demonstrated neutralizing capacity against the measles D8 genotype five to eight years after the second dose of the measles, mumps, and rubella vaccine. Additionally, most of the enrolled children exhibited cell-mediated immunity responses to measles virus stimulation.

Prevalence of Neutralizing Autoantibodies Against Type I Interferon in a Multicenter Cohort of Severe or Critical COVID-19 Cases in Shanghai

OBJECTIVE

We sought to explore the prevalence of type I interferon-neutralizing antibodies in a Chinese cohort and its clinical implications during the Omicron variant wave of SARS-CoV-2.

METHODS

Type I interferon (IFN) autoantibodies possessing neutralizing capabilities were identified using luciferase assays. The capacity of the autoantibodies for in vitro interference with antiviral activity of IFN was assessed by using a SARS-CoV-2 replicon system. An analysis of the demographic and clinical profiles of patients exhibiting neutralizing antibodies was also conducted.

RESULTS

In this cohort, 11.8% of severe/critical cases exhibited the existence of type I IFN-neutralizing antibodies, specifically targeting IFN-α2, IFN-ω, or both, with an elderly male patient tendency. Notably, these antibodies exerted a pronounced inhibitory effect on the antiviral activity of IFN against SARS-CoV-2 under controlled in vitro conditions. Furthermore, a noteworthy correlation was discerned between the presence of these neutralizing antibodies and critical clinical parameters, including C-reactive protein (CRP) levels, D-dimer levels, and lymphocyte counts.

CONCLUSION

The presence of type I IFN-neutralizing antibodies is a pervasive risk factor for severe/critical COVID-19 in the Chinese population.

Vaccine-induced neutralizing antibodies bind to the H protein of a historical measles virus

Measles is a highly contagious airborne viral disease. It can lead to serious complications and death and is preventable by vaccination. The live-attenuated measles vaccine (LAMV) derived from a measles virus (MV) isolated in 1954 has been in use globally for six decades and protects effectively by providing a durable humoral and cell-mediated immunity. Our study addresses the temporal stability of epitopes on the viral surface glycoprotein hemagglutinin (H) which is the major target of MV-neutralizing antibodies. We investigated the binding of seven vaccine-induced MV-H-specific monoclonal antibodies (mAbs) to cell-free synthesized MV-H proteins derived from the H gene sequences obtained from a lung specimen of a fatal case of measles pneumonia in 1912 and an isolate from a current case. The binding of four out of seven mAbs to the H protein of both MV strains provides evidence of epitopes that are stable for more than 100 years. The binding of the universally neutralizing mAbs RKI-MV-12b and RKI-MV-34c to the H protein of the 1912 MV suggests the long-term stability of highly conserved epitopes on the MV surface.

Immunogenicity and safety of COVID-19 booster vaccination: A population-based clinical trial to identify the best vaccination strategy

BACKGROUND

Various SARS-CoV-2 variants of concerns (VOCs) characterized by higher transmissibility and immune evasion have emerged. Despite reduced vaccine efficacy against VOCs, currently available vaccines provide protection. Population-based evidence on the humoral immune response after booster vaccination is crucial to guide future vaccination strategies and in preparation for imminent COVID-19 waves.

METHODS

This multicenter, population-based cohort study included 4697 individuals ≥18 years of age who received a booster vaccination. Antibody levels against SARS-CoV-2 receptor binding domain (RBD) and neutralizing antibodies against wild-type (WT) virus and Omicron variants were assessed at baseline (day of booster vaccination) and after four weeks. Safety was evaluated daily within the first week using a participant-completed electronic diary. Antibody levels were compared across different vaccination strategies, taking into account individual host factors.

RESULTS

Our main model including 3838 participants revealed that individuals who received a booster with mRNA-1273 compared to BNT162b2 vaccine had a significantly higher increase (95 %CI) in anti-RBD-antibody levels (37,707 BAU/mL [34,575-40,839] vs. 27,176 BAU/mL [26,265-28,087]), and of neutralization levels against WT (1,681 [1490-1872] vs. 1141 [1004-1278] and Omicron variant (422 [369-474] vs. 329 [284-374]). Neutralizing antibody titres highly correlated with anti-RBD antibodies, with neutralizing capacity 4.4 fold higher against WT compared to Omicron. No differences in safety were found between the two booster vaccines.

CONCLUSION

Our study underlines the superiority of a booster vaccination with mRNA-1273, independent of the primary vaccination and therefore provides guidance on the vaccination strategy.

Role of pre-existing immunity in driving the dengue virus serotype 2 genotype shift in the Philippines: A retrospective analysis of serological data

OBJECTIVE

The invasion of dengue virus (DENV)-2 Cosmopolitan genotype into the Philippines, where the Asian II genotype previously circulated challenges the principle of dengue serotype-specific immunity. Assessment of antibodies in this population may provide a mechanistic basis for how new genotypes emerge in dengue-endemic areas.

METHODS

We evaluated the neutralizing antibody (nAb) and antibody-dependent enhancement (ADE) responses against the two genotypes using archived serum samples collected from 333 patients with confirmed dengue in Metro Manila, Philippines, before, during, and after the introduction of the Cosmopolitan genotype. We quantified nAb titers in baby hamster kidney (BHK-21) cells with or without the Fcγ receptor IIA (FcγRIIA) to detect the capacity of virus-antibody complexes to neutralize or enhance DENV.

RESULTS

The nAb potency of the archived serum samples against the two genotypes was greatly affected by the presence of FcγRIIA. We found significant differences in nAb titers between the two genotypes in BHK-21 cells with FcγRIIA (P <0.0001). The archived serum samples were incapable of fully neutralizing the Cosmopolitan genotype, but instead strongly promoted its ADE compared to the Asian II genotype (P <0.0001).

CONCLUSION

These results reinforce the role of pre-existing immunity in driving genotype shifts. Our finding that specific genotypes exhibit differing susceptibilities to ADE by cross-reactive antibodies may have implications for dengue vaccine development.

Bridging the gap - estimation of 2022/2023 SARS-CoV-2 healthcare burden in Germany based on multidimensional data from a rapid epidemic panel

OBJECTIVES

Throughout the SARS-CoV-2 pandemic, Germany like other countries lacked adaptive population-based panels to monitor the spread of epidemic diseases.

METHODS

To fill a gap in population-based estimates needed for winter 2022/23 we resampled in the German SARS-CoV-2 cohort study MuSPAD in mid-2022, including characterization of systemic cellular and humoral immune responses by interferon-γ-release assay (IGRA) and CLIA/IVN assay. We were able to confirm categorization of our study population into four groups with differing protection levels against severe COVID-19 courses based on literature synthesis. Using these estimates, we assessed potential healthcare burden for winter 2022/23 in different scenarios with varying assumptions on transmissibility, pathogenicity, new variants, and vaccine booster campaigns in ordinary differential equation models.

RESULTS

We included 9921 participants from eight German regions. While 85% of individuals were located in one of the two highest protection categories, hospitalization estimates from scenario modeling were highly dependent on viral variant characteristics ranging from 30-300% compared to the 02/2021 peak. Our results were openly communicated and published to an epidemic panel network and a newly established modeling network.

CONCLUSIONS

We demonstrate feasibility of a rapid epidemic panel to provide complex immune protection levels for inclusion in dynamic disease burden modeling scenarios.

Predicting the immune escape of SARS-CoV-2 neutralizing antibodies upon mutation

COVID-19 has resulted in millions of deaths and severe impact on economies worldwide. Moreover, the emergence of SARS-CoV-2 variants presented significant challenges in controlling the pandemic, particularly their potential to avoid the immune system and evade vaccine immunity. This has led to a growing need for research to predict how mutations in SARS-CoV-2 reduces the ability of antibodies to neutralize the virus. In this study, we assembled a set of 1813 mutations from the interface of SARS-CoV-2 spike protein's receptor binding domain (RBD) and neutralizing antibody complexes and developed a machine learning model to classify high or low escape mutations using interaction energy, inter-residue contacts and predicted binding free energy change. Our approach achieved an Area under the Receiver Operating Characteristics (ROC) Curve (AUC) of 0.91 using the Random Forest classifier on the test dataset with 217 mutations. The model was further utilized to predict the escape mutations on a dataset of 29,165 mutations located at the interface of 83 RBD-neutralizing antibody complexes. A small subset of this dataset was also validated based on available experimental data. We found that top 10 % high escape mutations were dominated by charged to nonpolar mutations whereas low escape mutations were dominated by polar to nonpolar mutations. We believe that the present method will allow prioritization of high/low escape mutations in the context of neutralizing antibodies targeting SARS-CoV-2 RBD region and assist antibody design for current and emerging variants.

Estimates of protection levels against SARS-CoV-2 infection and severe COVID-19 in Germany before the 2022/2023 winter season: the IMMUNEBRIDGE project

PURPOSE

Despite the need to generate valid and reliable estimates of protection levels against SARS-CoV-2 infection and severe course of COVID-19 for the German population in summer 2022, there was a lack of systematically collected population-based data allowing for the assessment of the protection level in real time.

METHODS

In the IMMUNEBRIDGE project, we harmonised data and biosamples for nine population-/hospital-based studies (total number of participants n = 33,637) to provide estimates for protection levels against SARS-CoV-2 infection and severe COVID-19 between June and November 2022. Based on evidence synthesis, we formed a combined endpoint of protection levels based on the number of self-reported infections/vaccinations in combination with nucleocapsid/spike antibody responses ("confirmed exposures"). Four confirmed exposures represented the highest protection level, and no exposure represented the lowest.

RESULTS

Most participants were seropositive against the spike antigen; 37% of the participants ≥ 79 years had less than four confirmed exposures (highest level of protection) and 5% less than three. In the subgroup of participants with comorbidities, 46-56% had less than four confirmed exposures. We found major heterogeneity across federal states, with 4-28% of participants having less than three confirmed exposures.

CONCLUSION

Using serological analyses, literature synthesis and infection dynamics during the survey period, we observed moderate to high levels of protection against severe COVID-19, whereas the protection against SARS-CoV-2 infection was low across all age groups. We found relevant protection gaps in the oldest age group and amongst individuals with comorbidities, indicating a need for additional protective measures in these groups.

Caveats of chimpanzee ChAdOx1 adenovirus-vectored vaccines to boost anti-SARS-CoV-2 protective immunity in mice

Several COVID-19 vaccines use adenovirus vectors to deliver the SARS-CoV-2 spike (S) protein. Immunization with these vaccines promotes immunity against the S protein, but against also the adenovirus itself. This could interfere with the entry of the vaccine into the cell, reducing its efficacy. Herein, we evaluate the efficiency of an adenovirus-vectored vaccine (chimpanzee ChAdOx1 adenovirus, AZD1222) in boosting the specific immunity compared to that induced by a recombinant receptor-binding domain (RBD)-based vaccine without viral vector. Mice immunized with the AZD1222 human vaccine were given a booster 6 months later, with either the homologous vaccine or a recombinant vaccine based on RBD of the delta variant, which was prevalent at the start of this study. A significant increase in anti-RBD antibody levels was observed in rRBD-boosted mice (31-61%) compared to those receiving two doses of AZD1222 (0%). Significantly higher rates of PepMix™- or RBD-elicited proliferation were also observed in IFNγ-producing CD4 and CD8 cells from mice boosted with one or two doses of RBD, respectively. The lower efficiency of the ChAdOx1-S vaccine in boosting specific immunity could be the result of a pre-existing anti-vector immunity, induced by increased levels of anti-adenovirus antibodies found both in mice and humans. Taken together, these results point to the importance of avoiding the recurrent use of the same adenovirus vector in individuals with immunity and memory against them. It also illustrates the disadvantages of ChAdOx1 adenovirus-vectored vaccine with respect to recombinant protein vaccines, which can be used without restriction in vaccine-booster programs. KEY POINTS: • ChAdOx1 adenovirus vaccine (AZD1222) may not be effective in boosting anti-SARS-CoV-2 immunity • A recombinant RBD protein vaccine is effective in boosting anti-SARS-CoV-2 immunity in mice • Antibodies elicited by the rRBD-delta vaccine persisted for up to 3 months in mice.

Humoral responses to wild type and ancient BA.1 SARS-CoV-2 variant after heterologous priming vaccination with ChAdOx1 nCoV-19 and BNT162b2 booster dose

Several countries have recommended a booster dose of Pfizer BNT162b2 vaccine for subjects under the age of 60, who have already received the first dose of ChAdOx1. This is due to several ChAdOx1 vaccine-associated adverse vascular events and thrombocytopenia. Neutralization assay and quantitative IgG anti-SARS-CoV-2 Spike antibody (anti-S-IgG) were conducted to investigate the long-term responses to vaccine treatment in a cohort of Sardinian participants, who have received heterologous Prime-Boost Vaccination via ChAdOx1 vector vaccine and a booster dose via BNT162b2. The obtained results were compared with those of a cohort of healthcare workers (HCW) who received homologous BNT162b2 (BNT/BNT/BNT) vaccination. One month (T2) and five months after the second and before the third dose (T3), anti-spike antibody or neutralizing titers in the subjects vaccinated with ChAdOx1-S/BNT162b2 were significantly higher than those who experienced the ChAdOx1-S/ChAdOx1-S or BNT162b2/BNT162b2 schedule. These results suggest that a ChAdOx1-S/BNT162b2 regimen provides a more robust antibody response than either of the homologous regimens. However, the anti-spike antibodies or neutralizing titers after the third injection (mRNA vaccine) of ChAdOx1-S as a second dose and BNT162b2 were not statistically different. Homologous and heterologous vaccination provided a strong antibody response. Neutralizing activities were also described against the Omicron BA.1 variant in a sub-group (40) representative of the three vaccination regimens among our cohort.

Comparison of neutralization potency across passive immunotherapy approaches as potential treatments for emerging infectious diseases

The use of passive immunotherapy, either as plasma or purified antibodies, has been recommended to treat the emerging infectious diseases (EIDs) in the absence of alternative therapeutic options. Here, we compare the neutralization potency of various passive immunotherapy approaches designed to provide the immediate neutralizing antibodies as potential EID treatments. To prepare human plasma and purified IgG, we screened and classified individuals into healthy, convalescent, and vaccinated groups against SARS-CoV-2 using qRT-PCR, anti-nucleocapsid, and anti-spike tests. Moreover, we prepared purified IgG from non-immunized and hyperimmunized rabbits against SARS-CoV-2 spike protein. Human and rabbit samples were used to evaluate the neutralization potency by sVNT. All vaccinated and convalescent human plasma and purified IgG groups, as well as purified IgG from hyperimmunized rabbits, had significantly greater levels of spike-specific antibodies than the control groups. Furthermore, when compared to the other groups, the purified IgG from hyperimmunized rabbits exhibited superior levels of neutralizing antibodies, with an IC50 value of 2.08 μg/ml. Additionally, our results indicated a statistically significant positive correlation between the neutralization IC50 value and the positive endpoint concentration of spike-specific antibodies. In conclusion, our study revealed that purified IgG from hyperimmunized animals has greater neutralization potency than other passive immunotherapy methods and may be the most suitable treatment of critically ill patients in EIDs.

Characterization of SARS-CoV-2-specific humoral immunity and associated factors in the healthy population post-vaccination

OBJECTIVES

To investigate factors that may influence humoral immunity post-vaccination with a COVID-19-inactivated vaccine (SC2IV).

METHODS

A total of 1596 healthy individuals from the Seventh Affiliated Hospital, Sun Yat-sen University (1217) and Shenzhen Baotian Hospital (379) were enrolled in this study among which 694 and 218 participants were vaccinated with two-dose SC2IV, respectively. Physical examination indices were recorded. The levels of neutralizing antibody (NA), Spike IgG, receptor-binding domain (RBD) IgG, RBD IgG + IgM + IgA, and nucleocapsid IgG of SARS-CoV-2 were measured by a non-virus ELISA kit. Multiple statistical analyses were carried out to identify factors that influence humoral immunity post-vaccination.

RESULTS

The two-dosage vaccination could induce NA in more than 90 % of recipients. The NA has the strongest correlation with anti-RBD IgG. Age is the most important independent index that affects the NA level, while basophil count, creatine kinase-MB, mean corpuscular hemoglobin, the ratio of albumin to urine creatinine, and thyroglobulin antibody have relatively minor contributions. Indices that affect the NA level were different between males and females. Antibodies targeting other epitopes of SARS-CoV-2 were detected in recipients without anti-RBD.

CONCLUSIONS

The factors identified in association with the NA level post-vaccination may help to evaluate the protective effect, risk of re-infection, the severity of symptoms, and prognosis for vaccine recipients in clinical.

Biological and glucocorticoids treatment impair the medium-term immunogenicity to SARS-CoV-2 mRNA vaccines in autoimmune inflammatory rheumatic diseases

BACKGROUND

This study aims to assess the sustained immunological response to the SARS-CoV-2 vaccine in patients with autoimmune inflammatory rheumatic diseases (AIRD) undergoing different treatment regimens.

METHODS

We conducted a prospective observational study involving 157 AIRD patients without prior COVID-19 infection. Treatment regimens included non-treatment or glucocorticoid-only (not-treated/GCs), non-biological drugs, biological therapy, and JAK inhibitors. All participants completed the two-dose vaccine schedule, and 110 of them received an additional booster dose. Serum samples were collected approximately 3-6 months after the second and third vaccine doses to measure antibodies against the Spike protein (antiS-AB) and neutralizing antibodies (nAB) targeting six SARS-CoV-2 variants.

RESULTS

Following the third dose, all patients exhibited a significant increase in antiS-AB (FC = 15, p < 0.0001). Patients under biological therapy had lower titres compared to the non-biological (66% decrease, p = 0.038) and the not-treated/GCs group (62% decrease, p = 0.0132), with the latter persisting after the booster dose (86% decrease, p = 0.0027). GC use was associated with lower antiS-AB levels in the biological group (87% decrease, p = 0.0124), although not statistically significant after confounders adjustment. nABs showed the highest positivity rates for the wild-type strain before (50%) and after the booster dose (93%), while the Omicron variant exhibited the lowest rates (11% and 55%, respectively). All variants demonstrated similar positivity patterns and good concordance with antiS-AB (AUCs from 0.896 to 0.997).

CONCLUSIONS

The SARS-CoV-2 vaccine booster strategy effectively elicited a sustained antibody immune response in AIRD patients. However, patients under biological therapies exhibited a reduced response to the booster dose, particularly when combined with GCs.

Quantitative and Standardized Pseudovirus Neutralization Assay for COVID-19

COVID-19 is a global pandemic caused by the highly infectious SARS-CoV-2 virus. Efforts to combat SARS-CoV-2 infection include mass vaccination and development of monoclonal and convalescent plasma therapeutics that require precise measurements of correlative, functional neutralizing antibodies that prevent virus infection. Developing rapid, safe, easy-to-use, and high-quality neutralization assays are essential for the success of the massive effort. Here, we developed a vesicular stomatitis virus-based neutralization assay that was capable of quantifying varying degrees of neutralization in patient serum samples. This assay has two detection readouts, flow cytometry and live cell imaging. The two readout methods produced consistent values of all 50% neutralization titers, further enhancing measurement confidence on the assay. Moreover, the use of available reference standards such as the World Health Organization International Standard (NIBSC code 20/136) enables quantification and standardization of the pseudovirus neutralization assay with neutralizing antibody titers measured in International Units/mL. Quantitative and standardized neutralization assays are critical for reliable efficacy evaluation and comparison of numerous vaccines and therapeutics.

Comparative assessment of immunogenicity of recombinant insulin Aspart from BioGenomics and its originator NovoRapid® in adult patients with type 2 diabetes mellitus

OBJECTIVES

To assess and compare the immunogenicity of recombinant Insulin Aspart [manufactured by BioGenomics Limited (BGL-ASP)] with its originator NovoRapid® (manufactured by Novo Nordisk) in adult patients with type 2 diabetes mellitus.

RESEARCH DESIGN AND METHODS

BGL-IA-CTP301 study was a randomized, open label, parallel group, multicenter phase-III clinical study to compare the efficacy and safety of recombinant Insulin Aspart 100 U/mL [manufactured by BioGenomics Limited (BGL-ASP)] with its reference medicinal product (RMP); NovoRapid® [manufactured by Novo Nordisk], in adult patients with Type 2 diabetes mellitus (T2DM). The primary objective of the study was to compare the immunogenicity of BGL-ASP and RMP; NovoRapid® in patient serum samples collected from phase-III clinical study. Immunogenicity was studied as the incidence of patients positive for anti-insulin Aspart (AIA) antibodies, developed against BGL-ASP/RMP at baseline, end of 12 week and end of 24 week of the treatment period. The changes in incidence of patients positive for AIA antibodies post-baseline were also studied to assess and compare the treatment-emergent antibody response (TEAR) between the treatment groups (BGL-ASP and RMP). Statistical evaluation was done by Fisher's exact test to compare the overall incidence of patients positive for AIA antibodies and the TEAR positives observed post-baseline in both the treated groups. An in-vitro neutralizing antibody assay (Nab assay) was also performed to study the effect of AIA antibodies in neutralizing the biological activity/metabolic function of the insulin. The neutralizing potential of AIA was studied by its effect on %glucose uptake. We also evaluated the association between AIA antibody levels and its impact on biological activity by studying the correlation between them.

RESULTS

Analysis of immunogenicity data suggested that the percentage of patients positive for AIA antibodies until week 24 was similar and comparable in both the treatment groups, BGL-ASP and RMP; NovoRapid®. The changes in incidence of patients positive for AIA post-baseline in terms of TEAR positives were also similar and comparable between the treatment groups. The results of the Nab assay with confirmed positive AIA samples from BGL-ASP- and RMP-treated groups did not have any negative impact on %glucose uptake by the cells in Nab assay, confirming the absence of neutralizing antibodies in both the treatment groups. The correlation studies also showed absence of association between AIA antibody levels and percentage glucose uptake in both BGL-ASP and RMP-NovoRapid® treatment groups. CONCLUSIONS: The immunogenicity assessment based on the overall incidence of patients positive for AIA, changes in incidence of patients positive for AIA post-baseline, TEAR rates and absence of neutralizing antibodies, were found to be apparently similar and comparable in both the treatment groups (BGL-ASP and RMP). We conclude from our studies that the immunogenicity of BGL-ASP is similar and comparable to RMP and the observed immunogenicity in terms of anti-insulin Aspart antibody levels had no impact on the biological activity of insulin.

RBD class 1 and 2 antibody epitopes elicit around 70% neutralizing capacity against SARS-CoV-2 virus following boosting with inactivated virus vaccine

A third dose of inactivated virus vaccine (IVV) boosts neutralizing antibodies, reducing SARS-CoV-2 transmission rate and COVID-19 severity. However, the impact of RBD-elicited antibodies and their neutralizing activity by the boost of IVV is unknown. We investigated the impact of IVV's boost shot on RBD-elicited antibodies and their neutralizing activity in 18 subjects receiving the second and third IVV doses. Using an RBD antibodies depletion assay, we assessed the neutralizing activity of RBD-elicited antibodies. After the second dose, RBD-antigen elicitation accounted for ∼60% of neutralizing activity, which increased to 82% after the IVV boost against ancestral SARS-CoV-2. Depleting class 3 and class 4-specific antibodies with the Beta-RBD protein revealed that NAbs targeting RBD class 1 and class 2 subdomains increased from 57% to 75% post-boost. These findings highlight the significant enhancement of RBD-specific antibodies, especially against RBD class 1 and class 2, with IVV booster doses. Our study offers valuable insights for optimizing COVID-19 vaccine strategies.

[COVID-19 vaccination at the University of Alicante (Spain): detection of neutralizing antibodies against SARS-CoV-2 by rapid serological test, a cross-sectional study]

OBJECTIVE

Neutralizing antibodies against SARS-CoV-2 have shown to be an effective tool for the analysis of the immunity generated against COVID-19. Numerous seroprevalence studies carried out in different groups have made it possible to draw a global map of vaccination coverage through the use of rapid lateral flow immunochromatography serological tests for clinical and epidemiological purposes. The objective of our study was to determine the degree of immunity against SARS-CoV-2 associated with the presence of neutralizing antibodies in administrative staff, teachers and students at the University of Alicante by means of a rapid serological test and to learn about their experience with vaccination against COVID-19.

METHODS

A cross-sectional epidemiological study was designed, based on the prevalence of antibodies against the S protein (spike) of SARS-CoV-2. A total of 888 people participated. The study was carried out with a single test (July 6 to July 22, 2021). Using logistic regression, adjusted Odds Ratios were calculated according to sex, age, type of vaccine, number of vaccine doses received, complete vaccination schedule, and having had COVID-19.

RESULTS

The vaccines received mostly were Vaxzevria® and Comirnaty®, with 73.3% between both, although 67.2% presented a complete regimen. The results of the OJABIO rapid neutralizing antibody test gave a positive result in 61.4% of the sample. There was a high association between the variables COVID-19 infection, two doses of vaccine, Spikevax® or Comirnaty® vaccine, and eighteen/twenty-nine years old group with a positive result on the OJABIO test. A total of 712 subjects answered the parallel survey (80%) on adverse effects and preferences between the different vaccines against COVID-19.

CONCLUSIONS

The vaccination status against COVID-19 in the university community after six months of the start of national immunization strategies reflects low coverage despite the excellent willingness to get vaccinated. Neutralizing antibodies (NAb) rapid tests can be useful to guide immunization strategies and decide when to administer new booster doses.

What can neutralizing antibodies tell us about the quality of immunity in COVID-19 convalescents and vaccinees?

During the SARS-CoV-2 pandemic, the lack of standardized measurements of the immune response after vaccination or recovery from COVID-19 resulted in incomparable results and hindered correlation establishment. Prioritizing reliable and standardized methods to monitor pathogen-specific immunity is crucial, not only during the COVID-19 pandemic but also for future outbreaks. During our study of the humoral immune response, we used a SARS-CoV-2 wild-type neutralization assay, ensuring the measurement of the immune response directed to all SARS-CoV-2 antigens in their proper conformation. A head-to-head comparison of the neutralizing antibody (NAb) responses elicited by four vaccines used in Europe during 2021 (BNT162b2, mRNA-1273, ChAdOx nCoV-19, and Ad26.COV2.S) and their comparison to NAb responses in convalescents showed that while the amount was comparable, NAbs induced by natural infection were of higher quality. Namely, NAbs produced by disease were better activators of the complement system than NAbs induced by vaccination. Furthermore, the contribution of spike protein-specific IgGs to the SARS-CoV-2 neutralization was lower in convalescents compared to vaccinees, indicating that those who recovered from COVID-19 were armed with antibodies of additional specificities and/or classes that contributed to virus neutralization. These findings suggest that a higher stringency of public policy measures targeting individuals who have recovered from COVID-19, in comparison to those who have been vaccinated, may not have been fully justified.

Antibody responses to recombinant vesicular stomatitis virus-Zaire Ebolavirus vaccination for Ebola virus disease across doses and continents: 5-year durability

OBJECTIVES

To report 5-year persistence and avidity of antibodies produced by the live-attenuated recombinant vesicular stomatitis virus (rVSV) expressing the Zaire Ebolavirus (ZEBOV) glycoprotein (GP), known as rVSV-ZEBOV (Ervebo®).

METHODS

Healthy adults vaccinated with 300,000 or 10-50 million plaque-forming units of rVSV-ZEBOV in the WHO-coordinated trials of 2014-2015 were followed for up to 4 (Lambaréné, Gabon) and 5 (Geneva, Switzerland) years. We report seropositivity rates, geometric mean titres (GMTs), and population distribution of ZEBOV-GP ELISA IgG antibodies, neutralizing antibodies (pseudovirus and live-virus neutralization) and antibody avidity; the primary outcome was ZEBOV-GP ELISA IgG GMTs at 4 or 5 years compared with 1 year (Y1) after immunization.

RESULTS

Among the 168 eligible vaccinees (Geneva: 97 and Lambaréné: 71) enrolled 1 year post-immunization, 146 (87%) remained enrolled at 4 years (Geneva: n = 88, Lambaréné: n = 58), and 84 (87%, Geneva) at 5 years post-vaccination. ZEBOV-GP ELISA IgG GMTs plateaued, with no declining trend from 1 year through the last time point assessed (1147.8 [95% CI 874.3-1507.0] at Y1 versus 1548.1 [95% CI 1136.6-2108.5] at Y5 in Geneva volunteers receiving ≥10 million plaque-forming units of rVSV-ZEBOV), their avidity matching that of ZEBOV convalescents. Live-virus neutralizing antibodies were detected for shorter periods and in fewer vaccinees (53/95 [56%] at Y1 versus 35/84 [42%] at Y5 in Geneva volunteers, all dose levels).

DISCUSSION

Titres at Y1 emerged as a correlate of antibody persistence at Y5. The findings of persistent ZEBOV-GP ELISA IgG titres yet shorter-lasting, lower titres of live-virus neutralizing antibodies suggest the contribution of antibody-mediated protective mechanisms other than neutralization. Long-term clinical efficacy of rVSV-ZEBOV, however, requires further study.

Evaluation of two anti-SARS-CoV-2 antibody immunoassays for monitoring patients on pre-exposure prophylaxis

Pre-exposure prophylaxis (PrEP) is crucial to prevent severe COVID-19 in immunocompromised patients. A reliable method is needed to quantify anti-SARS-CoV-2 antibody levels for personalized monitoring during PrEP. We measured the binding antibody concentrations of 63 immunocompromised patients receiving 300mg or 600mg tixagevimab/cilgavimab on PrEP day and twice during the following 3 months. All blood samples were tested using the Abbott anti-SARS-CoV-2 IgG II Quant assay, the Roche Elecsys anti-SARS-CoV-2 S assay, and live virus-based neutralization assays. The results of the two immunoassays were correlated on day 0, 1 month, and 3 months post-PrEP. Passing-Bablok regression demonstrated higher anti-S concentration values measured with the Roche immunoassay compared to those measured with the Abbott immunoassay. Antibody concentrations were higher after 600 mg tixagevimab/cilgavimab prophylaxis than after 300 mg. The neutralizing antibody titers obtained using the omicron BA.5 and BA.2.75 strains were low. Both automated immunoassays are suitable for monitoring immunocompromised patients on PrEP.

Effective Neutralizing Antibody Response Against SARS-CoV-2 Virus and Its Omicron BA.1 Variant in Fully Vaccinated Hematological Patients

SARS-CoV-2 and its variants cause CoronaVIrus Disease 19 (COVID-19), a pandemic disease. Hematological malignancies increase susceptibility to severe COVID-19 due to immunosuppression. Anti-SARS-CoV-2 neutralizing antibodies protect against severe COVID-19. This retrospective real-life study aimed to evaluate seropositivity and neutralizing antibody rates against SARS-CoV-2 and its Omicron BA.1 variant in hematological patients. A total of 106 patients with different hematologic malignancies, who have mostly received three or more vaccine doses (73%), were included in this study. Serum was collected between May and June 2022. The primary endpoint was anti-SARS-CoV-2 antibody response against ancestral (wild type; wt) and Omicron BA.1 virus, defined as a neutralizing antibody titer ≥ 1:10. Adequate neutralizing antibody response was observed in 75 (71%) and 87 (82%) of patients for wt and Omicron BA.1 variants, respectively.However, patients with B-cell lymphoproliferative disorders and/or those treated with anti-CD20 monoclonal antibodies in the prior 12 months showed a lower seropositivity rate compared to other patients against both Omicron BA.1 variant (73% vs 91%; P = 0.02) and wt virus (64% vs 78%; P = 0.16). Our real-life experience confirmed that full vaccination against SARS-CoV-2 induces adequate neutralizing antibody protection for both the wt virus and Omicron BA.1 variants, even in hematological frail patients. However, protective measures should be maintained in hematological patients, especially those with B-cell lymphoproliferative diseases treated with anti-CD20 monoclonal antibodies, because these subjects could have a reduced neutralizing antibody production.

Broadly potent anti-SARS-CoV-2 antibody shares 93% of epitope with ACE2 and provides full protection in monkeys

OBJECTIVES

Due to the rapid evolution of SARS-CoV-2 to variants with reduced sensitivity to vaccine-induced humoral immunity and the near complete loss of protective efficacy of licensed therapeutic monoclonal antibodies, we isolated a potent, broad-spectrum neutralizing antibody that could potentially provide prophylactic protection to immunocompromised patient populations.

METHODS

Spike-specific B-cell clones isolated from a vaccinated post-infected donor were profiled for those producing potent neutralizing antibodies against a panel of SARS-CoV-2 variants. The P4J15 antibody was further characterized to define the structural binding epitope, viral resistance, and in vivo efficacy.

RESULTS

The P4J15 mAb shows <20 ng/ml neutralizing activity against all variants including the latest XBB.2.3 and EG.5.1 sub-lineages. Structural studies of P4J15 in complex with Omicron XBB.1 Spike show that the P4J15 epitope shares ∼93% of its buried surface area with the ACE2 contact region, consistent with an ACE2 mimetic antibody. In vitro selection of SARS-CoV-2 mutants escaping P4J15 neutralization showed reduced infectivity, poor ACE2 binding, and mutations are rare in public sequence databases. Using a SARS-CoV-2 XBB.1.5 monkey challenge model, P4J15-LS confers complete prophylactic protection with an exceptionally long in vivo half-life of 43 days.

CONCLUSIONS

The P4J15 mAb has potential as a broad-spectrum anti-SARS-CoV-2 drug for prophylactic protection of at-risk patient populations.

Development of IFNβ-1a versions with reduced immunogenicity and full in vitro biological activity for the treatment of multiple sclerosis

IFNβ (recombinant interferon Beta) has been widely used for the treatment of Multiple sclerosis for the last four decades. Despite the human origin of the IFNβ sequence, IFNβ is immunogenic, and unwanted immune responses in IFNβ-treated patients may compromise its efficacy and safety in the clinic. In this study, we applied the DeFT (De-immunization of Functional Therapeutics) approach to producing functional, de-immunized versions of IFNβ-1a. Two de-immunized versions of IFNβ-1a were produced in CHO cells and designated as IFNβ-1a(VAR1) and IFNβ-1a(VAR2). First, the secondary and tertiary protein structures were analyzed by circular dichroism spectroscopy. Then, the variants were also tested for functionality. While IFNβ-1a(VAR2) showed similar in vitro antiviral activity to the original protein, IFNβ-1a(VAR1) exhibited 40% more biological potency. Finally, in vivo assays using HLA-DR transgenic mice revealed that the de-immunized variants showed a markedly reduced immunogenicity when compared to the originator.

Detection of pre-existing neutralizing antibodies against Ad26 in HIV-1-infected individuals not responding to the Ad26.COV2.S vaccine

PURPOSE

The Ad26.COV2.S vaccine is a replication-incompetent human adenovirus type 26 vector encoding the SARS-CoV-2 spike protein. In a phase 1-2a trial, a single dose of Ad26.COV2.S induced SARS-CoV-2 spike-specific antibodies in ≥ 96% of healthy adults. To investigate vaccine immunogenicity in HIV-1-infection, we measured SARS-CoV-2 spike-specific antibodies in Ad26.COV2.S vaccinated HIV-1-infected patients and analyzed the presence of pre-existing Ad26 neutralizing antibodies.

METHODS

We included all Ad26.COV2.S vaccinated HIV-1-infected patients of Erlangen HIV cohort fulfilling all inclusion criteria. The study cohort consisted of 15 HIV-1-infected patients and three HIV-1-uninfected subjects who received the Ad26.COV2.S vaccine between April and November 2021. Pre-vaccination sera were collected between October 2014 and June 2021, post-vaccination sera between June and December 2021. Neutralizing antibodies towards Ad26 were determined by a FACS-based inhibition assay measuring the expression of SARS-CoV-2 spike and adenoviral proteins in HEK293T cells after in-vitro transduction with Ad26.COV2.S or the control ChAdOx1-S.

RESULTS

Six out of 15 HIV-1-infected patients failed to develop SARS-CoV-2-specific antibodies and four patients developed weak antibody responses after vaccination with Ad26.COV2.S. Pre-vaccination sera of four of the six vaccine non-responders showed neutralizing activity towards Ad26.COV2.S but not toward the ChAdOx1-S vaccine at 1:50 dilution. After Ad26.COV2.S vaccination, 17 of the 18 subjects developed strong Ad26-neutralizing activity and only one of the 18 subjects showed neutralizing activity towards the ChAdOx1-S vaccine.

CONCLUSION

Ad26.COV2.S vaccination showed a high failure rate in HIV-1-infected patients. Pre-existing immunity against Ad26 could be an important contributor to poor vaccine efficacy in a subgroup of patients.

Factors influencing neutralizing antibody response to the original SARS-CoV-2 virus and the Omicron variant in a high vaccination coverage country, a population-based study

The study compared immunity to the original SARS-CoV-2 virus (Wuhan) and the Omicron variant using neutralizing antibodies (NAbs), that provide a good approximation of protective immunity. The results might help determine immunization strategies.

DESIGN AND METHODS

Unlike previous studies, we analyzed NAbs in a random sample of 110 IgG positive sera from individuals who participated in a population-based seroprevalence transversal study, carried out in May 2022 in two Chilean cities, a country with high vaccination coverage.

RESULTS

Our findings indicate that 98.2% of individuals had NAbs against Wuhan, 65.5% against Omicron, and 32.7% tested positive for Wuhan but not Omicron. Factors influencing protective immunity included a prior natural infection and the number of vaccines received. NAbs titers against the original virus were high, demonstrating vaccine effectiveness in the population. However, the level of antibodies decreased when measuring NAbs against Omicron, particularly among older individuals, indicating a decline in vaccine protection. Previous COVID-19 episodes acted as a natural booster, increasing NAbs titers against both virus strains.

CONCLUSIONS

Protective immunity against the original Wuhan SARS-CoV-2 virus is reduced when compared to Omicron variant. Updating vaccine to target emerging variants and continued monitoring of effectiveness at the population level are necessary.

A competitive ligand binding assay for detection of neutralizing antibodies against an insulin analog

Biotherapeutics have the potential to trigger undesired immune responses in the patients. For therapeutic proteins, immunogenicity is manifested as anti-drug antibodies (ADA). Because ADA could compromise pharmacokinetics, efficacy, and safety, regulatory agencies require immunogenicity assessment during clinical development. A tiered bioanalytical approach is recommended to monitor clinical immunogenicity, and neutralizing antibodies (NAb) are studied in Tier 4 if the molecule is immunogenic. Although cell-based assays, which reflect the pharmacological mechanism of action, are in some cases the preferred assay format for detecting NAbs, they are associated with operational complexity and sometimes suboptimal assay performance. Alternatively, non-cell-based assays have also been developed and implemented. In our current study, a competitive ligand binding assay (CLBA) was developed to detect NAbs for insulin efsitora alfa (efsitora, basal insulin Fc, LY3209590), a novel fusion protein being studied for the treatment of Type 1 diabetes and Type 2 diabetes. The CLBA demonstrated acceptable sensitivity, drug tolerance, precision, and robustness, and thus provides a suitable approach for detecting NAbs against efsitora.

Fading SARS-CoV-2 humoral VOC cross-reactivity and sustained cellular immunity in convalescent children and adolescents

Cross-reactive cellular and humoral immunity can substantially contribute to antiviral defense against SARS-CoV-2 variants of concern (VOC). While the adult SARS-CoV-2 cellular and humoral immunity and its cross-recognition potential against VOC is broadly analyzed, similar data regarding the pediatric population are missing. In this study, we perform an analysis of the humoral and cellular SARS-CoV-2 response immune of 32 convalescent COVID-19 children (children), 27 convalescent vaccinated adults(C + V+) and 7 unvaccinated convalescent adults (C + V-). Similarly to adults, a significant reduction of cross-reactive neutralizing capacity against delta and omicron VOC was observed 6 months after SARS-CoV-2 infection. While SAR-CoV-2 neutralizing capacity was comparable among children and C + V- against all VOC, children demonstrated as expected an inferior humoral response when compared to C + V+. Nevertheless, children generated SARS-CoV-2 reactive T cells with broad cross-recognition potential. When compared to V + C+, children presented even comparable frequencies of WT-reactive CD4 + and CD8 + T cells with high avidity and functionality. Taking into consideration the limitations of study - unknown disease onset for 53% of the asymptomatic pediatric subjects, serological detection of SARS-CoV-2 infection-, our results suggest that following SARS-CoV-2 infection children generate a humoral SARS-CoV-2 response with neutralizing potential comparable to unvaccinated COVID-19 convalescent adults as well a sustained SARS-CoV-2 cellular response cross-reactive to VOC.

Cell-based passive immunization for protection against SARS-CoV-2 infection

BACKGROUND

Immunologically impaired individuals respond poorly to vaccines, highlighting the need for additional strategies to protect these vulnerable populations from COVID-19. While monoclonal antibodies (mAbs) have emerged as promising tools to manage infectious diseases, the transient lifespan of neutralizing mAbs in patients limits their ability to confer lasting, passive prophylaxis from SARS-CoV-2. Here, we attempted to solve this problem by combining cell and mAb engineering in a way that provides durable immune protection against viral infection using safe and universal cell therapy.

METHODS

Mouse embryonic stem cells equipped with our FailSafe™ and induced allogeneic cell tolerance technologies were engineered to express factors that potently neutralize SARS-CoV-2, which we call 'neutralizing biologics' (nBios). We subcutaneously transplanted the transgenic cells into mice and longitudinally assessed the ability of the cells to deliver nBios into circulation. To do so, we quantified plasma nBio concentrations and SARS-CoV-2 neutralizing activity over time in transplant recipients. Finally, using similar cell engineering strategies, we genetically modified FailSafe™ human-induced pluripotent stem cells to express SARS-CoV-2 nBios.

RESULTS

Transgenic mouse embryonic stem cells engineered for safety and allogeneic-acceptance can secrete functional and potent SARS-CoV-2 nBios. As a dormant, subcutaneous tissue, the transgenic cells and their differentiated derivatives long-term deliver a supply of protective nBio titers in vivo. Moving toward clinical relevance, we also show that human-induced pluripotent stem cells, similarly engineered for safety, can secrete highly potent nBios.

CONCLUSIONS

Together, these findings show the promise and potential of using 'off-the-shelf' cell products that secrete neutralizing antibodies for sustained protective immunity against current and future viral pathogens of public health significance.

Follow up and comparative assessment of IgG, IgA, and neutralizing antibody responses to SARS-CoV-2 between mRNA-vaccinated naïve and unvaccinated naturally infected individuals over 10 months

BACKGROUND

Evidence on the effectiveness of vaccination-induced immunity compared to SARS-CoV-2 natural immunity is warranted to inform vaccination recommendations.

AIM

In this study, we aimed to conduct a comparative assessment of antibody responses between vaccinated naïve (VN) and unvaccinated naturally infected individuals (NI) over 10 Months.

METHOD

The study comprised fully-vaccinated naïve individuals (VN; n = 596) who had no history of SARS-CoV-2 infection, and received two doses of either BNT162b2 or mRNA-1273, and naturally infected individuals who had a documented history of SARS-CoV-2 infection and no vaccination record (NI cohort; n = 218). We measured the levels of neutralizing total antibodies (NtAbs), anti-S-RBD IgG, and anti-S1 IgA titers among VN and NI up to ∼10 months from administration of the first dose, and up to ∼7 months from SARS-CoV-2 infection, respectively. To explore the relationship between the antibody responses and time, Spearman's correlation coefficient was computed. Furthermore, correlations between the levels of NtAbs/anti-S-RBD IgG and NtAbs/anti-S1 IgA were examined through pairwise correlation analysis.

RESULTS

Up to six months, VN individuals had a significantly higher NtAb and anti-S-RBD IgG antibody responses compared to NI individuals. At the 7th month, there was a significant decline in antibody responses among VN individuals, but not NI individuals, with a minimum decrease of 3.7-fold (p < 0.001). Among VN individuals, anti-S1 IgA levels began to decrease significantly (1.4-fold; p = 0.007) after two months, and both NtAb and S-RBD IgG levels began to decline significantly (NtAb: 2.0-fold; p = 0.042, S-RBD IgG: 2.4-fold; p = 0.035) after three months. After 10 months, the most significant decline among VN individuals was observed for S-RBD-IgG (30.0-fold; P < 0.001), followed by NtAb (15.7-fold; P < 0.001) and S-IgA (3.7-fold; P < 0.001) (most stable). Moreover, after 5 months, there was no significant difference in the IgA response between the two groups.

CONCLUSION

These findings have important implications for policymakers in the development of vaccination strategies, particularly in the consideration of booster doses to sustain long-lasting protection against COVID-19.

Current limitations of gene therapy for rare pediatric diseases: Lessons learned from clinical experience with AAV vectors

Gene therapy using adeno-associated viral (AAV) vectors is a promising therapeutic strategy for multiple inherited diseases. Following intravenous injection, AAV vectors carrying a copy of the missing gene or the genome-editing machinery reach their target cells and deliver the genetic material. Several clinical trials are currently ongoing and significant success has already been achieved with at least six AAV gene therapy products with market approval in Europe and the United States. Nonetheless, clinical trials and preclinical studies have uncovered several limitations of AAV gene transfer, which need to be addressed in order to improve the safety and enable the treatment of the largest patient population. Limitations include the occurrence of immune-mediated toxicities, the potential loss of correction in the long run, and the development of neutralizing antibodies against AAV vectors preventing re-administration. In this review, we summarize these limitations and discuss the potential technological developments to overcome them. © 2023 Published by Elsevier Masson SAS on behalf of French Society of Pediatrics.

Seroprevalence of dengue virus infection in Pune City in India, 2019: A decadal change

BACKGROUND

The burden of dengue infection needs to be monitored along with tracking of the changes in dengue virus (DENV) transmission intensity for vaccine introduction decisions.

METHODS

The seroprevalence of dengue was investigated in Pune City in India, in early 2019 using 1654 sera from apparently healthy human participants enrolled randomly through multistage cluster sampling. We used 797 retrospective human sera from late 2009 for comparison. All sera were assessed for the presence of dengue-specific IgG antibodies. A subset (n = 230) was tested for serotype-specific plaque reduction-neutralizing antibodies against all four serotypes.

RESULTS

The dengue IgG seroprevalence of 62.9% (95% CI 59.4-66.1) in 2009 increased to 88.4% (95% CI 86.8-89.8) in 2019. Age-stratified dengue seroprevalence revealed a gradual increase in IgG seropositivity from 70.1% in 0-9 years to 85.0% in 10-19 years. The annual probability of dengue infection estimated as a force of infection was 4.1 (95% CI 3.8-4.5) in 2009, which increased to 10.9 (95% CI 10.2-11.6) in 2019. Analysis of dengue serotype-specific neutralizing antibodies revealed DENV-3 as the dominant serotype. The age of exposure to at least one dengue serotype was reduced in 2019 over 2009.

CONCLUSIONS

There was a significant increase in the intensity of dengue virus transmission in Pune City over the decade. Since over 85% of the participants above nine years of age had exposure to DENV by 2019, dengue vaccine introduction can be considered. Moreover, such repeated serosurveys in different regions might inform about the readiness of the population for dengue vaccination.

Standardization, validation, and comparative evaluation of a faster and high-performance test for quantification of yellow fever neutralizing antibodies

Although it is considered the reference for quantification of neutralizing antibodies, classical method of the plaque reduction neutralization test (PRNT) is labor intensive, requires specific equipment and inputs, besides a long time for its finalization, even in the micro-PRNT version (in 96-well plates). It has a higher sample throughput, however the smaller wells make the reading of plaques more difficult. With an immunoenzymatic revelation step and a semi-automated reading, the μFRN-HRP (micro Focus Reduction Neutralization - Horseradish Peroxidase) is a faster and more efficient test for the quantification of YF neutralizing antibodies. This study aimed to standardize, validate, and compare it with the reference method in 6-well plates (PRNT). Once the execution protocol was standardized, precision, accuracy, selectivity, and robustness were evaluated to validate the μFRN-HRP. In addition, 200 sera of vaccinees were processed by the μFRN-HRP and by the micro-PRNT to compare with the reference test, estimating agreement by Intraclass Correlation Coefficient (ICC). The standardization and validation of the μFRN-HRP was carried out successfully. Weak to moderate agreement was observed between μFRN-HRP and PRNT for titers in reciprocal dilution, while the same comparison between the classical tests resulted in a better ICC. However, titers in milli-international units obtained by μFRN-HRP showed a substantial agreement with PRNT, while the agreement between micro-PRNT and PRNT was inferior. Therefore, μFRN-HRP can be used in the confirmation of natural YF infection and immune response to vaccination, replacing the micro-PRNT, gaining agility, while preserving the specificity of the result.

Levels of neutralizing antibodies against resident farm strain or vaccine strain are not indicators of protection against PRRSV-1 vertical transmission under farm conditions

BACKGROUND

Vertical transmission is key for the maintenance of porcine reproductive and respiratory syndrome virus (PRRSV) infection. In vaccinated farms, vertical transmission can still occur despite sows having some level of immunity because of repeated vaccination or contact with the wild-type virus. The present study aimed to correlate the age of sows and the amplitude of neutralizing antibodies (Nab) (heterologous neutralization) with PRRSV-1 vertical transmission (VT). For this purpose, umbilical cords of 1,554 newborns (corresponding to 250 litters) were tested for PRRSV by RT-PCR in two PRRSV-unstable vaccinated farms. In parallel, the sows were bled after farrowing and the levels of antibodies were determined by ELISA and by the viral neutralization test against the vaccine virus, the virus circulating in the farm, and other unrelated contemporary PRRSV-1 strains. The relationship between the parity and the probability of delivering infected piglets and the presence of broadly Nabs examined.

RESULTS

The proportion of VT events in the two examined farms ranged from 18.9% to 23.0%. Young sows (parity 1-2) were 1.7 times more likely to have VT than older sows (p < 0.05). Despite higher ELISA S/P antibody ratios in younger sows (p < 0.05), NAb against the resident farm strain were at a similar level between sows delivering infected and healthy piglets regardless of age, mostly with low titers (2-3 log2). The titers of NAb against the vaccine virus were also low, and no correlations with VT were observed. When a panel of another 4 strains (1 isolated in the 1990s, and 3 contemporary strains) were used for the neutralization test, most sow sera were not capable of neutralizing the contemporary strains.

CONCLUSIONS

Titers of NAb could not be correlated with the occurrence of PRRSV VT. The amplitude of NAb present in most vaccinated sows is limited with a considerable proportion unresponsive regarding NAb production.

Impact of the COVID-19 vaccine booster strategy on vaccine protection: a pilot study of a military hospital in Taiwan

Purpose

The global fight against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has led to widespread vaccination efforts, yet the optimal dosing schedule for SARS-CoV-2 vaccines remains a subject of ongoing research. This study aims to investigate the effectiveness of administering two booster doses as the third and fourth doses at different intervals to enhance vaccine protection.

Materials and Methods

This study was conducted at a military regional hospital operated by the Ministry of National Defense in Taiwan. A cohort of vaccinated individuals was selected, and their vaccine potency was assessed at various time intervals following their initial vaccine administration. The study participants received booster doses as the third and fourth doses, with differing time intervals between them. The study monitored neutralizing antibody titers and other relevant parameters to assess vaccine efficacy.

Results

Our findings revealed that the potency of the SARS-CoV-2 vaccine exhibited a significant decline 80 days after the initial vaccine administration. However, a longer interval of 175 days between booster injections resulted in significantly higher neutralizing antibody titers. The individuals who received the extended interval boosters exhibited a more robust immune response, suggesting that a vaccine schedule with a 175-day interval between injections may provide superior protection against SARS-CoV-2.

Conclusion

This study underscores the importance of optimizing vaccine booster dosing schedules to maximize protection against SARS-CoV-2. The results indicate that a longer interval of 175 days between the third and fourth doses of the vaccine can significantly enhance the neutralizing antibody response, potentially offering improved protection against the virus. These findings have important implications for vaccine distribution and administration strategies in the ongoing battle against the SARS-CoV-2 pandemic. Further research and large-scale trials are needed to confirm and extend these findings for broader public health implications.

Immunogenicity of COVID-19 vaccines in lung cancer patients

OBJECTIVE

Patients with lung cancer are at increased risk of SARS-CoV-2 infection and severe complications from COVID-19, but information on the efficacy of anti-SARS-CoV-2 vaccine in these patients is scarce. We aimed at evaluating the safety and immunogenicity of COVID-19 vaccines in this population.

PATIENTS AND METHODS

The prospective, nationwide SOLID substudy, enrolled adults with lung cancer who were fully vaccinated against COVID-19. Serum anti-SARS-CoV-2 IgG antibody levels were quantitatively assessed two weeks and six months after receipt of the last dose using a chemiluminescent microparticle immunoassay. Multivariate odds ratios for the association between demographic and clinical factors and seronegativity after vaccination were estimated.

RESULTS

1973 lung cancer patients were enrolled. Most patients had stage IV disease (66%) and were receiving active cancer treatment (82.7%). No significant differences were found in the probability of being seronegative for anti-SARS-CoV-2 IgG antibodies after full vaccination between patients who were receiving active cancer treatment and those who were not (p = 0.396). The administration of immunotherapy or oral targeted therapy and immunization with mRNA-1273 COVID-19 vaccine were factors independently associated with increased odds of being seropositive after vaccination. From all patients, 1405 received the second dose of vaccine and high levels of antibody titers were observed in 93.6% of patients two weeks after second dose. At six months, multivariate logistic regression analysis showed that performance status ≥ 2 was independently associated with a higher probability of being seronegative after full vaccination with an OR 4.15. On the other hand, received chemotherapy or oral target therapy and vaccination with mRNA-1273 were a factor independently associated with lower odds of being seronegative after full vaccination with an OR 0.52, 0.37 and 0.34, respectively.

CONCLUSIONS

Lung cancer patients can safely achieve a strong immune response against SARS-CoV-2 after full vaccination, regardless of the cancer treatment received.

TRIAL REGISTRATION

NCT04407143.

Recombinant protein based on domain III and capsid regions of zika virus induces humoral and cellular immune response in immunocompetent BALB/c mice

Zika virus infection continues to be a global concern for human health due to the high-risk association of the disease with neurological disorders and microcephaly in newborn. Nowadays, no vaccine or specific antiviral treatment is available, and the development of safe and effective vaccines is yet a challenge. In this study, we obtained a novel subunit vaccine that combines two regions of zika genome, domain III of the envelope and the capsid, in a chimeric protein in E. coli bacteria. The recombinant protein was characterized with polyclonal anti-ZIKV and anti-DENV antibodies that corroborate the specificity of the molecule. In addition, the PBMC from zika-immune donors stimulated with the ZEC recombinant antigen showed the capacity to recall the memory T cell response previously generated by the natural infection. The chimeric protein ZEC was able to self-assemble after combination with an immunomodulatory specific oligonucleotide to form aggregates. The inoculation of BALB/c mice with ZEC aggregated and not aggregated form of the protein showed a similar humoral immune response, although the aggregated variant induced more cell-mediated immunity evaluated by in vitro IFNγ secretion. In this study, we propose a novel vaccine candidate against the zika disease based on a recombinant protein that can stimulate both arms of the immune system.

Exosomes mediate the antibody-resistant intercellular transmission of porcine epidemic diarrhea virus

Porcine epidemic diarrhea virus (PEDV) is a highly pathogenic enteric coronavirus that causes severe enteritis and lethal watery diarrhea in suckling piglets, leading to tremendous economic losses. Exosomes have been reported to participate in intercellular communication by the transportation of a variety of biological materials, including RNAs, lipids, and proteins. However, PEDV transmission routes have not yet been fully elucidated, and whether exosomes function in PEDV transmission remains unclear. In this study, we extracted and purified exosomes from PEDV-infected Vero cells using a stringent isolation method with a combination of chemical precipitation, ultracentrifugation, and incubation with CD63-labeled magnetic beads. We found that exosomes from PEDV-infected Vero cells contain viral genomic RNA and viral nucleocapsid protein. Furthermore, we demonstrated that the purified exosomes from PEDV-infected cells are capable of transmitting the virus to both PEDV-susceptible and non-susceptible cells. Importantly, exosome-mediated PEDV infection was resistant to neutralization by PEDV-specific neutralizing antibodies that potently neutralized free PEDV. Our study reveals a potential immune evasion mechanism utilized by PEDV and provides new insight into the transmission and infection of this important pathogen.