Prime-boost vaccine strategy against viral infections: Mechanisms and benefits

Efficacy of heterologous boosting against SARS-CoV-2 using a recombinant interferon-armed fusion protein vaccine (V-01): a randomized, double-blind and placebo-controlled phase III trial

Waning of neutralizing titres along with decline of protection efficacy after the second dose of COVID-19 vaccines was observed, including China-made inactivated vaccines. Efficacy of a heterologous boosting using one dose of a recombinant SARS-CoV-2 fusion protein vaccine (V-01) in inactivated vaccine-primed population was studied, aimed to restore the immunity. A randomized, double-blind and placebo-controlled phase III trial was conducted in healthy people aged 18 years or older in Pakistan and Malaysia. Each eligible participant received one dose of the V-01 vaccine developed by Livzon Mabpharm Inc. or placebo within the 3-6 months after the two-dose primary regimen, and was monitored for safety and efficacy. The primary endpoint was protection against confirmed symptomatic SARS-CoV-2 infection. A total of 10,218 participants were randomly assigned to receive a vaccine or placebo. Virus-neutralizing antibodies were assessed in 419 participants. A dramatic increase (11.3-fold; 128.3–1452.8) of neutralizing titres was measured in the V-01 group at 14 days after the booster. Over two months of surveillance, vaccine efficacy was 47.8% (95%CI: 22.6–64.7) according to the intention-to-treat principle. The most common adverse events were transient, mild-to-moderate pain at the injection site, fever, headache, and fatigue. Serious adverse events occurred almost equally in V-01 (0.12%) and placebo (0.16%) groups. The heterologous boosting with the V-01 vaccine was safe and efficacious, which could elicit robust humoral immunity under the epidemic of the Omicron variant.

Trial registration:ClinicalTrials.gov identifier: NCT05096832.

Immunological Study of Combined Administration of SARS-CoV-2 DNA Vaccine and Inactivated Vaccine

Objective: We constructed two DNA vaccines containing the receptor-binding domain (RBD) genes of multiple SARS-CoV-2 variants and used them in combination with inactivated vaccines in a variety of different protocols to explore potential novel immunization strategies against SARS-CoV-2 variants. Methods: Two DNA vaccine candidates with different signal peptides (namely, secreted and membrane signal peptides) and RBD protein genes of different SARS-CoV-2 strains (Wuhan-Hu-1, B.1.351, B.1.617.2, C.37) were used. Four different combinations of DNA and inactivated vaccines were tested, namely, Group A: three doses of DNA vaccine; B: three doses of DNA vaccine and one dose of inactivated vaccine; C: two doses of inactivated vaccine and one dose of DNA vaccine; and D: coadministration of DNA and inactivated vaccines in two doses. Subgroups were grouped according to the signal peptide used (subgroup 1 contained secreted signal peptides, and subgroup 2 contained membrane signal peptides). The in vitro expression of the DNA vaccines, the humoral and cellular immunity responses of the immunized mice, the immune cell population changes in local lymph nodes, and proinflammatory cytokine levels in serum samples were evaluated. Results: The antibody responses and cellular immunity in Group A were weak for all SARS-CoV-2 strains; for Group B, there was a great enhancement of neutralizing antibody (Nab) titers against the B.1.617.2 variant strain. Group C showed a significant increase in antibody responses (NAb titers against the Wuhan-Hu-1 strain were 768 and 1154 for Group C1 and Group C2, respectively, versus 576) and cellular immune responses, especially for variant B.1.617.2 (3240 (p < 0.001) and 2430 (p < 0.05) for Group C1 and Group C2, versus 450); Group D showed an improvement in immunogenicity. Group C induced higher levels of multiple cytokines. Conclusion: The DNA vaccine candidates we constructed, administered as boosters, could enhance the humoral and cellular immune responses of inactivated vaccines against COVID-19, especially for B.1.617.2.

Immunogenicity and safety of heterologous versus homologous prime-boost schedules with an adenoviral vectored and mRNA COVID-19 vaccine: a systematic review

BACKGROUND

Heterologous prime-boost with ChAdOx1 nCoV-19 vector vaccine (ChAd) and a messenger RNA vaccine (BNT or mRNA-1273) has been widely facilitating mass coronavirus disease 2019 (COVID-19) immunisation. This review aimed to synthesize immunogenicity and reactogenicity of heterologous immunisations with ChAd and BNT (mRNA-1273) vaccine compared with homologous ChAd or BNT (mRNA-1273) immunisation.

METHODS

PubMed, Web of Science, and Embase databases were searched from inception to March 7, 2022. Immunogenicity involving serum antibodies against different SAS-CoV-2 fragments, neutralizing antibody, or spike-specific T cells response were compared. Any, local and systemic reactions were pooled by meta-analysis for comparison.

RESULTS

Of 14,571 records identified, 13 studies (3024 participants) were included for analysis. Compared with homologous BNT/BNT vaccination, heterologous ChAd/BNT schedule probably induced noninferior anti-spike protein while higher neutralizing antibody and better T cells response. Heterologous ChAd/BNT (mRNA-1273) immunisation induced superior anti-spike protein and higher neutralizing antibody and better T cells response compared with homologous ChAd/ChAd vaccination. Heterologous ChAd/BNT (mRNA-1273) had similar risk of any reaction (RR = 1.30, 95% CI: 0.86-1.96) while higher risk of local reactions (RR = 1.65, 95% CI: 1.27-2.15) and systemic reactions (RR = 1.49, 95% CI: 1.17-1.90) compared with homologous ChAd/ChAd vaccination. There was a higher risk of local reactions (RR = 1.16, 95% CI: 1.03-1.31) in heterologous ChAd/BNT (mRNA-1273) vaccination compare with homologous BNT/BNT but a similar risk of any reaction (RR = 1.03, 95% CI: 0.79-1.34) and systemic reactions (RR = 0.89, 95% CI: 0.60-1.30).

CONCLUSIONS

Heterologous ChAd/BNT schedule induced at least comparable immunogenicity compared with homologous BNT/BNT and better immunogenicity compared with homologous ChAd/ChAd vaccination. The synthetical evidence supported the general application of heterologous prime-boost vaccination using ChAd and BNT COVID-19 vaccines.

Heterologous prime-boost vaccination based on Polymorphic protein D protects against intravaginal Chlamydia trachomatis infection in mice

The control of the worldwide spread of sexually transmitted Chlamydia trachomatis (Ct) infection urgently demands the development of a preventive vaccine. In this work, we designed a vaccine based on a fragment of polymorphic protein D (FPmpD) that proved to be immunogenic enough to generate a robust systemic and mucosal IgG humoral immune response in two strains of mice. We used a heterologous prime-boost strategy, including simultaneous systemic and mucosal administration routes. The high titers of anti-PmpD antibodies elicited by this immunization scheme did not affect murine fertility. We tested the vaccine in a mouse model of Ct intravaginal infection. Anti-PmpD antibodies displayed potent neutralizing activity in vitro and protective effects in uterine tissues in vivo. Notably, the humoral immune response of PmpD-vaccinated mice was faster and stronger than the primary immune response of non-vaccinated mice when exposed to Ct. FPmpD-based vaccine effectively reduced Ct shedding into cervicovaginal fluids, bacterial burden at the genitourinary tract, and overall infectivity. Hence, the FPmpD-based vaccine might constitute an efficient tool to protect against Ct intravaginal infection and decrease the infection spreading.

The History of Live Attenuated Centrin Gene-Deleted Leishmania Vaccine Candidates

Leishmaniasis, caused by an infection of the Leishmania protozoa, is a neglected tropical disease and a major health problem in tropical and subtropical regions of the world, with approximately 350 million people worldwide at risk and 2 million new cases occurring annually. Current treatments for leishmaniasis are not highly efficacious and are associated with high costs, especially in low- and middle-income endemic countries, and high toxicity. Due to a surge in the incidence of leishmaniases worldwide, the development of new strategies such as a prophylactic vaccine has become a high priority. However, the ability of Leishmania to undermine immune recognition has limited our efforts to design safe and efficacious vaccines against leishmaniasis. Numerous antileishmanial vaccine preparations based on DNA, subunit, and heat-killed parasites with or without adjuvants have been tried in several animal models but very few have progressed beyond the experimental stage. However, it is known that people who recover from Leishmania infection can be protected lifelong against future infection, suggesting that a successful vaccine requires a controlled infection to develop immunologic memory and subsequent long-term immunity. Live attenuated Leishmania parasites that are non-pathogenic and provide a complete range of antigens similarly to their wild-type counterparts could evoke such memory and, thus, would be effective vaccine candidates. Our laboratory has developed several live attenuated Leishmania vaccines by targeted centrin gene disruptions either by homologous recombination or, more recently, by using genome editing technologies involving CRISPR-Cas9. In this review, we focused on the sequential history of centrin gene-deleted Leishmania vaccine development, along with the characterization of its safety and efficacy. Further, we discussed other major considerations regarding the transition of dermotropic live attenuated centrin gene-deleted parasites from the laboratory to human clinical trials.

Prime-boost vaccination regimens with INO-4800 and INO-4802 augment and broaden immune responses against SARS-CoV-2 in nonhuman primates

The enhanced transmissibility and immune evasion associated with emerging SARS-CoV-2 variants demands the development of next-generation vaccines capable of inducing superior protection amid a shifting pandemic landscape. Since a portion of the global population harbors some level of immunity from vaccines based on the original Wuhan-Hu-1 SARS-CoV-2 sequence or natural infection, an important question going forward is whether this immunity can be boosted by next-generation vaccines that target emerging variants while simultaneously maintaining long-term protection against existing strains. Here, we evaluated the immunogenicity of INO-4800, our synthetic DNA vaccine candidate for COVID-19 currently in clinical evaluation, and INO-4802, a next-generation DNA vaccine designed to broadly target emerging SARS-CoV-2 variants, as booster vaccines in nonhuman primates. Rhesus macaques primed over one year prior with the first-generation INO-4800 vaccine were boosted with either INO-4800 or INO-4802 in homologous or heterologous prime-boost regimens. Both boosting schedules led to an expansion of T cells and antibody responses which were characterized by improved neutralizing and ACE2 blocking activity across wild-type SARS-CoV-2 as well as multiple variants of concern. These data illustrate the durability of immunity following vaccination with INO-4800 and additionally support the use of either INO-4800 or INO-4802 in prime-boost regimens.

COVID-19 vaccines mix-and-match: The concept, the efficacy and the doubts

The search for developing effective vaccines against SARS-CoV-2 began with the start of the COVID-19 pandemic, and the first vaccine dose was administered in December 2020. Today, full vaccination of most of the world's population is considered the most important means to overcome the COVID-19 pandemic. Vaccination has been associated with various struggles. Some adverse reactions have resulted in the discontinuation of the specific vaccines use in some countries. Countries in poor regions have faced difficulties supplying enough vaccine doses, and the emergence of new variants of concern has resulted in reduced effectiveness of available vaccines against COVID-19. The mix-and-match strategy, using heterologous vaccines in the first and second doses, might successfully solve the mentioned struggles. Moreover, this strategy has been associated with higher cellular and humoral immune responses without significantly increasing the adverse reactions. Hence, this strategy can help improve the vaccines' effectiveness, and act as a solution for vaccine shortage in poor regions.

A randomized clinical trial of a booster dose with low versus standard dose of AZD1222 in adult after 2 doses of inactivated vaccines

Background

Immunogenicity of inactivated SARS-CoV-2 vaccine has waning antibody over time. With the emergence of the SARS-CoV-2 delta variant, which requires higher neutralizing antibody to prevent infection, a booster dose is needed.

Objective

To evaluate immunogenicity and reactogenicity of standard- versus low-dose ChAdOx1 nCoV-19 vaccine booster after CoronaVac in healthy adults.

Methods

A double-blinded, randomized, controlled trial of adult, aged 18–59 years, with completion of 2-dose CoronaVac at 21–28 days apart for more than 2 months was conducted. Participants were randomized to receive AZD1222 (Oxford/AstraZeneca) intramuscularly; standard dose (SD, 5x10¹⁰ viral particles) or low dose (LD, 2.5x10¹⁰ viral particles). Surrogate virus neutralization test (sVNT) against wild type and delta variant, and anti-spike-receptor-binding-domain IgG (anti-S-RBD IgG) were compared as geometric mean ratio (GMR) at day 14 and 90 between LD and SD arms.

Results

From July-August 2021, 422 adults with median age of 44 (IQR 36–51) years were enrolled. The median interval from CoronaVac to AZD1222 booster was 77 (IQR 64–95) days. At baseline, geometric means (GMs) of sVNT against delta variant and anti-S-RBD IgG were 18.1%inhibition (95% CI 16.4–20.0) and 111.5 (105.1–118.3) BAU/ml. GMs of sVNT against delta variant and anti-S-RBD IgG in SD were 95.6%inhibition (95% CI 94.3–97.0) and 1975.1 (1841.7–2118.2) BAU/ml at day 14, and 89.4%inhibition (86.4–92.4) and 938.6 (859.9–1024.4) BAU/ml at day 90, respectively. GMRs of sVNT against delta variant and anti-S-RBD IgG in LD compared to SD were 1.00 (95% CI 0.98–1.02) and 0.84 (0.76–0.93) at day 14, and 0.98 (0.94–1.03) and 0.89 (0.79–1.00) at day 90, respectively. LD recipients had significantly lower rate of fever (6.8% vs 25.0%) and myalgia (51.9% vs 70.7%) compared to SD.

Conclusion

Half-dose AZD1222 booster after 2-dose inactivated SARS-CoV-2 vaccination had non-inferior immunogenicity, yet lower systemic reactogenicity. Fractional low-dose AZD1222 booster should be considered especially in resource-constrained settings.

Modified vaccinia Ankara expressing EEHV1A glycoprotein B elicits humoral and cell-mediated immune responses in mice

Elephant endotheliotropic herpesvirus (EEHV) can cause lethal hemorrhagic disease (EEHV-HD) in Asian elephants and is the largest cause of death in captive juvenile Asian elephants in North America and Europe. EEHV-HD also has been documented in captive and wild elephants in their natural range countries. A safe and effective vaccine to prevent lethal EEHV infection would significantly improve conservation efforts for this endangered species. Recent studies from our laboratory suggest that EEHV morbidity and mortality are often associated with primary infection. Therefore, we aim to generate a vaccine, particularly for EEHV1 naïve animals, with the goal of preventing lethal EEHV-HD. To address this goal, we generated a Modified Vaccinia Ankara (MVA) recombinant virus expressing a truncated form of glycoprotein B (gBΔfur731) from EEHV1A, the strain associated with the majority of lethal EEHV cases. Vaccination of CD-1 mice with this recombinant virus induced robust antibody and polyfunctional T cell responses significantly above mice inoculated with wild-type MVA. Although the vaccine-induced T cell response was mainly observed in CD8+ T cell populations, the CD4+ T cell response was also polyfunctional. No adverse responses to vaccination were observed. Overall, our data demonstrates that MVA-gBΔfur731 stimulates robust humoral and cell-mediated responses, supporting its potential translation for use in elephants.

Immunization with recombinant accessory protein-deficient SARS-CoV-2 protects against lethal challenge and viral transmission

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has led to a worldwide Coronavirus Disease 2019 (COVID-19) pandemic. Despite high efficacy of the authorized vaccines, protection against the surging variants of concern (VoC) was less robust. Live-attenuated vaccines (LAV) have been shown to elicit robust and long-term protection by induction of host innate and adaptive immune responses. We sought to develop a COVID-19 LAV by generating 3 double open reading frame (ORF)-deficient recombinant (r)SARS-CoV-2 simultaneously lacking two accessory open reading frame (ORF) proteins (ORF3a/ORF6, ORF3a/ORF7a, and ORF3a/ORF7b). Here, we report that these double ORF-deficient rSARS-CoV-2 have slower replication kinetics and reduced fitness in cultured cells as compared to their parental wild-type (WT) counterpart. Importantly, these double ORF-deficient rSARS-CoV-2 showed attenuation in both K18 hACE2 transgenic mice and golden Syrian hamsters. A single intranasal dose vaccination induced high levels of neutralizing antibodies against different SARS-CoV-2 VoC, and also activated viral component-specific T-cell responses. Notably, the double ORF-deficient rSARS-CoV-2 were able to protect, as determined by inhibition of viral replication, shedding, and transmission, against challenge with SARS-CoV-2. Collectively, our results demonstrate the feasibility to implement these double ORF-deficient rSARS-CoV-2 as safe, stable, immunogenic and protective LAV for the prevention of SARS-CoV-2 infection and associated COVID-19 disease.

Reactogenicity and immunogenicity of heterologous prime-boost immunization with COVID-19 vaccine

BACKGROUND

The objective of the present work was to assess the reactogenicity and immunogenicity of heterologous COVID-19 vaccination regimens in clinical trials and observational studies.

METHODS

PubMed, Cochrane Library, Embase, MedRxiv, BioRxiv databases were searched in September 29, 2021. The PRISMA instruction for systemic review was followed. Two reviewers independently selected the studies, extracted the data and assessed risk of bias. The quality of studies was evaluated using the New Castle-Ottawa and Cochrane risk of instrument. The characteristics and study outcome (e.g., adverse events, immune response, and variant of concern) were extracted.

RESULTS

Nineteen studies were included in the final data synthesis with 5 clinical trials and 14 observational studies. Heterologous vaccine administration showed a trend toward more frequent systemic reactions. However, the total reactogenicity was tolerable and manageable. Importantly, the heterologous prime-boost vaccination regimens provided higher immunogenic effect either vector/ mRNA-based vaccine or vector/ inactivated vaccine in both humoral and cellular immune response. Notably, the heterologous regimens induced the potential protection against the variant of concern, even to the Delta variant.

CONCLUSIONS

The current findings provided evidence about the higher induction of robust immunogenicity and tolerated reactogenicity of heterologous vaccination regimens (vector-based/mRNA vaccine or vector-based/inactivated vaccine). Also, this study supports the application of heterologous regimens against COVID-19 which may provide more opportunities to speed up the global vaccination campaign and maximize the capacity to control the pandemic.

Revival of the heterologous prime-boost technique in COVID-19: An outlook from the history of outbreaks

BACKGROUND

The heterologous prime-boost vaccination technique is not novel as it has a history of deployment in previous outbreaks.

AIM

Hence, this narrative review aims to provide critical insight for reviving the heterologous prime-boost immunization strategy for SARS-CoV-2 vaccination relative to a brief positive outlook on the mix-dose approach deployed in previous and existing outbreaks (ie, Ebola virus disease (EVD), malaria, tuberculosis, hepatitis B, HIV and influenza virus).

METHODOLOGY AND MATERIALS

A Boolean search was carried out to find the literature in MEDLINE-PubMed, Clinicaltrials, and Cochrane Central Register of Controlled Trials databases up till December 22, 2021, using the specific keywords that include "SARS-CoV2", "COVID-19", "Ebola," "Malaria," "Tuberculosis," "Human Immunodeficiency Virus," "Hepatitis B," "Influenza," "Mix and match," "Heterologous prime-boost," with interposition of "OR" and "AND." Full text of all the related articles in English language with supplementary appendix was retrieved. In addition, the full text of relevant cross-references was also retrieved.

RESULTS

Therefore, as generally evident by the primary outcomes, that is, safety, reactogenicity, and immunogenicity reported and updated by preclinical and clinical studies for addressing previous and existing outbreaks so far, including COVID-19, it is understood that heterologous prime-boost immunization has been proven successful for eliciting a more efficacious immune response as of yet in comparison to the traditional homologous prime-boost immunization regimen.

DISCUSSION

Accordingly, with increasing cases of COVID-19, many countries such as Germany, Pakistan, Canada, Thailand, and the United Kingdom have started administering the heterologous vaccination as the technique aids to rationalize the usage of the available vaccines to aid in the global race to vaccinate majority to curb the spread of COVID-19 efficiently. However, the article emphasizes the need for more large controlled trials considering demographic details of vaccine recipients, which would play an essential role in clearing the mistrust about safety concerns to pace up the acceptance of the technique across the globe.

CONCLUSION

Consequently, by combatting the back-to-back waves of COVID-19 and other challenging variants of concerns, including Omicron, the discussed approach can also help in addressing the expected evolution of priority outbreaks as coined by WHO, that is, "Disease X" in 2018 with competency, which according to WHO can turn into the "next pandemic" or the "next public health emergency," thus would eventually lead to eradicating the risk of "population crisis."

Increased neutralization of SARS-CoV-2 Delta variant after heterologous ChAdOx1 nCoV-19/BNT162b2 versus homologous BNT162b2 vaccination

Heterologous SARS-CoV-2 vaccine approaches with a second mRNA-based vaccine have been favored in the recommendations of many countries over homologous vector-based ChAdOx1 nCoV-19 vaccination after reports of thromboembolic events and lower efficacy of this regimen. In the middle of 2021, the SARS-CoV-2 Delta variant of concern (VoC) has become predominant in many countries worldwide. Data addressing the neutralization capacity of a heterologous ChAdOx1 nCoV-19/mRNA-based vaccination approach against the Delta VoC in comparison to the widely used homologous mRNA-based vaccine regimen are limited. Here, we compare serological immune responses of a cohort of ChAdOx1 nCoV-19/BNT162b2-vaccinated participants with those of BNT162b2/BNT162b2 vaccinated ones and show that neutralization capacity against the Delta VoC is significantly increased in sera of ChAdOx1 nCoV-19/BNT162b2-vaccinated participants. This overall effect can be attributed to ChAdOx1 nCoV-19/BNT162b2-vaccinated women, especially those with more severe adverse effects leading to sick leave following second immunization.

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Heterologous ChAd/BNT vaccination is highly immunogenic

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Delta VoC neutralization is increased after heterologous ChAd/BNT vaccination

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This effect is attributable to women with sick leave after second vaccination

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IgA levels are overall low, but higher after BNT/BNT vaccination

Heterologous AD5-nCOV plus CoronaVac versus homologous CoronaVac vaccination: a randomized phase 4 trial

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants and the waning of vaccine-elicited neutralizing antibodies suggests that additional coronavirus disease 2019 (COVID-19) vaccine doses may be needed for individuals who initially received CoronaVac. We evaluated the safety and immunogenicity of the recombinant adenovirus type 5 (AD5)-vectored COVID-19 vaccine Convidecia as a heterologous booster versus those of CoronaVac as homologous booster in adults previously vaccinated with CoronaVac in an ongoing, randomized, observer-blinded, parallel-controlled phase 4 trial ( NCT04892459 ). Adults who had received two doses of CoronaVac in the past 3-6 months were vaccinated with Convidecia (n = 96) or CoronaVac (n = 102). Adults who had received one dose of CoronaVac in the past 1-3 months were also vaccinated with Convidecia (n = 51) or CoronaVac (n = 50). The co-primary endpoints were the occurrence of adverse reactions within 28 d after vaccination and geometric mean titers (GMTs) of neutralizing antibodies against live wild-type SARS-CoV-2 virus at 14 d after booster vaccination. Adverse reactions after vaccination were significantly more frequent in Convidecia recipients but were generally mild to moderate in all treatment groups. Heterologous boosting with Convidecia elicited significantly increased GMTs of neutralizing antibody against SARS-CoV-2 than homologous boosting with CoronaVac in participants who had previously received one or two doses of CoronaVac. These data suggest that heterologous boosting with Convidecia following initial vaccination with CoronaVac is safe and more immunogenic than homologous boosting.

Does Anybody Want an Injectable Rotavirus Vaccine, and Why? Understanding the Public Health Value Proposition of Next-Generation Rotavirus Vaccines

Routine infant immunization with live, oral rotavirus vaccines (LORVs) has had a major impact on severe gastroenteritis disease. Nevertheless, in high morbidity and mortality settings rotavirus remains an important cause of disease, partly attributable to the sub-optimal clinical efficacy of LORVs in those settings. Regardless of the precise immunological mechanism(s) underlying the diminished efficacy, the introduction of injectable next-generation rotavirus vaccines (iNGRV), currently in clinical development, could offer a potent remedy. In addition to the potential for greater clinical efficacy, precisely how iNGRVs are delivered (multiple doses to young infants; alongside LORVs or as a booster; co-formulated with Diphtheria-Tetanus-Pertussis (DTP)-containing vaccines), their pricing, and their storage and cold chain characteristics could each have major implications on the resultant health outcomes, on cost-effectiveness as well as on product preferences by national stakeholders and healthcare providers. To better understand these implications, we critically assessed whether there is a compelling public health value proposition for iNGRVs based on potential (but still hypothetical) vaccine profiles. Our results suggest that the answer is highly dependent on the specific use cases and potential attributes of such novel vaccines. Notably, co-formulation of iNGRVs with similar or greater efficacy than LORVs with a DTP-containing vaccine, such as DTP-Hib-HepB, scored especially high on potential impact, cost-effectiveness, and strength of preference by national stakeholders and health care providers in lower and middle income countries.

Safety and immunogenicity of ChAdOx1 MERS vaccine candidate in healthy Middle Eastern adults (MERS002): an open-label, non-randomised, dose-escalation, phase 1b trial

BACKGROUND

ChAdOx1-vectored vaccine candidates against several pathogens have been developed and tested in clinical trials and ChAdOx1 nCoV-19 has now been licensed for emergency use for COVID-19. We assessed the safety and immunogenicity of the ChAdOx1 MERS vaccine in a phase 1b trial in healthy Middle Eastern adults.

METHOD

MERS002 is an open-label, non-randomised, dose-escalation, phase 1b trial. Healthy Middle Eastern adults aged 18-50 years were included in the study. ChAdOx1 MERS was administered as a single intramuscular injection into the deltoid muscle of the non-dominant arm at three different dose groups: 5·0 × 109 viral particles in a low-dose group, 2·5 × 1010 viral particles in an intermediate-dose group, and 5·0 × 1010 viral particles in a high-dose group. The primary objective was to assess the safety and tolerability of ChAdOx1 MERS, measured by the occurrence of solicited and unsolicited adverse events after vaccination for up to 28 days and occurrence of serious adverse events up to 6 months. The study is registered with ClinicalTrials.gov, NCT04170829.

FINDINGS

Between Dec 17, 2019, and June 1, 2020, 24 participants were enrolled (six to the low-dose, nine to the intermediate-dose, and nine to the high-dose group) and received a dose; 23 were available for follow-up at 6 months. The one dose of ChAdOx1 MERS vaccine was well tolerated with no serious adverse event reported during the 6 months of follow-up. Most adverse events were mild (67, 74%) and moderate (17, 19%). Six (7%) severe adverse events were reported by two participants in the intermediate-dose group (two feverish, two headache, one joint pain, and one muscle pain). Pain at the injection site was the most common local and overall adverse event, reported by 15 (63%) of the 24 participants. The most common systemic adverse event was headache, reported by 14 (58%), followed by muscle pain reported by 13 (54%). The vaccine induced both antibody and T cell immune responses in all volunteers; antibodies peaked at day 28 and T cell responses peaked at day 14; and continued until the end of follow-up at 6 months.

INTERPRETATION

The acceptable safety and immunogenicity data from this phase 1b trial of ChAdOx1 MERS vaccine candidate in Healthy Middle Eastern adults, combined with previous safety and immunogenicity data from a trial in the UK, support selecting the ChAdOx1 MERS vaccine for advancement into phase 2 clinical evaluation.

FUNDING

UK Department of Health and Social Care, using UK Aid funding, managed by the UK National Institute for Health Research; and King Abdullah International Medical Research Center.

Self-amplifying mRNA-Based Vaccine Technology and Its Mode of Action

Self-amplifying mRNAs derived from the genomes of positive-strand RNA viruses have recently come into focus as a promising technology platform for vaccine development. Non-virally delivered self-amplifying mRNA vaccines have the potential to be highly versatile, potent, streamlined, scalable, and inexpensive. By amplifying their genome and the antigen encoding mRNA in the host cell, the self-amplifying mRNA mimics a viral infection, resulting in sustained levels of the target protein combined with self-adjuvanting innate immune responses, ultimately leading to potent and long-lasting antigen-specific humoral and cellular immune responses. Moreover, in principle, any eukaryotic sequence could be encoded by self-amplifying mRNA without the need to change the manufacturing process, thereby enabling a much faster and flexible research and development timeline than the current vaccines and hence a quicker response to emerging infectious diseases. This chapter highlights the rapid progress made in using non-virally delivered self-amplifying mRNA-based vaccines against infectious diseases in animal models. We provide an overview of the unique attributes of this vaccine approach, summarize the growing body of work defining its mechanism of action, discuss the current challenges and latest advances, and highlight perspectives about the future of this promising technology.

Heterologous prime-boost immunizations with chimpanzee adenoviral vectors elicit potent and protective immunity against SARS-CoV-2 infection

A safe and effective vaccine for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is urgently needed to tackle the COVID-19 global pandemic. Here, we describe the development of chimpanzee adenovirus serotypes 6 and 68 (AdC6 and AdC68) vector-based vaccine candidates expressing the full-length transmembrane spike glycoprotein. We assessed the vaccine immunogenicity, protective efficacy, and immune cell profiles using single-cell RNA sequencing in mice. Mice were vaccinated via the intramuscular route with the two vaccine candidates using prime-only regimens or heterologous prime-boost regimens. Both chimpanzee adenovirus-based vaccines elicited strong and long-term antibody and T cell responses, balanced Th1/Th2 cell responses, robust germinal center responses, and provided effective protection against SARS-CoV-2 infection in mouse lungs. Strikingly, we found that heterologous prime-boost immunization induced higher titers of protective antibodies, and more spike-specific memory CD8+ T cells in mice. Potent neutralizing antibodies produced against the highly transmissible SARS-CoV-2 variants B.1.1.7 lineage (also known as N501Y.V1) and B.1.351 lineage (also known as N501Y.V2) were detectable in mouse sera over 6 months after prime immunization. Our results demonstrate that the heterologous prime-boost strategy with chimpanzee adenovirus-based vaccines is promising for further development to prevent SARS-CoV-2 infection.

Role of Senescence and Aging in SARS-CoV-2 Infection and COVID-19 Disease

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in a global pandemic associated with substantial morbidity and mortality worldwide, with particular risk for severe disease and mortality in the elderly population. SARS-CoV-2 infection is driven by a pathological hyperinflammatory response which results in a dysregulated immune response. Current advancements in aging research indicates that aging pathways have fundamental roles in dictating healthspan in addition to lifespan. Our review discusses the aging immune system and highlights that senescence and aging together, play a central role in COVID-19 pathogenesis. In our review, we primarily focus on the immune system response to SARS-CoV-2 infection, the interconnection between severe COVID-19, immunosenescence, aging, vaccination, and the emerging problem of Long-COVID. We hope to highlight the importance of identifying specific senescent endotypes (or "sendotypes"), which can used as determinants of COVID-19 severity and mortality. Indeed, identified sendotypes could be therapeutically exploited for therapeutic intervention. We highlight that senolytics, which eliminate senescent cells, can target aging-associated pathways and therefore are proving attractive as potential therapeutic options to alleviate symptoms, prevent severe infection, and reduce mortality burden in COVID-19 and thus ultimately enhance healthspan.

An overview of the production methods for core-shell microspheres for parenteral controlled drug delivery

Core-shell microspheres hold great promise as a drug delivery system because they offer several benefits over monolithic microspheres in terms of release kinetics, for instance a reduced initial burst release, the possibility of delayed (pulsatile) release, and the possibility of dual-drug release. Also, the encapsulation efficiency can significantly be improved. Various methods have proven to be successful in producing these core-shell microspheres, both the conventional bulk emulsion solvent evaporation method and methods in which the microspheres are produced drop by drop. The latter have become increasingly popular because they provide improved control over the particle characteristics. This review assesses various production methods for core-shell microspheres and summarizes the characteristics of formulations prepared by the different methods, with a focus on their release kinetics.

Early Immunogenicity and safety of the third dose of BNT162b2 mRNA Covid-19 vaccine among adults older than 60 years; real world experience

BACKGROUND

Despite high vaccine coverage, an increase in breakthrough COVID-19 infections, prompted administration of a third BNT162b2 dose to people>60 years in Israel since July 2021. Here, we report real-world immunogenicity following third dose.

METHODS

Overall, 208 healthcare workers aged>60 were included. Paired pre- and post-second and/or -third dose IgG and neutralizing-antibody titers were compared. A subpopulation of low-responders to the second dose were also tested for T-cell activation. For 25 paired serum samples we tested neutralization of wild-type vs. neutralization of delta and lambda variants, pre- and post-third dose. Active surveillance of vaccine adverse-events was conducted through surveys.

RESULTS

A pronounced immune response was observed following the third dose, including a 33-fold and 51-fold increase in IgG and neutralizing ab, respectively. The neutralizing antibody levels post-third-dose were 9.34 times higher than post-second-dose (GMT 2598 95%CI 2085-3237 vs. 207 95%CI 126-339). Nine previously low-responders, had a significant antibody increase post-third-dose, and 7/9 showed increase in T cell activation. Additionally, sera obtained post-third-dose, highly and comparably neutralized the wild-type, delta and lambda variants. Of 1056 responders to the adverse-event survey, none had serious events.

CONCLUSIONS

We demonstrate a rapid and broad immune response to the third BNT162b2 dose in individuals>60 years.

A Review of UK-Registered and Candidate Vaccines for Bovine Respiratory Disease

Vaccination is widely regarded as a cornerstone in animal or herd health and infectious disease management. Nineteen vaccines against the major pathogens implicated in bovine respiratory disease are registered for use in the UK by the Veterinary Medicines Directorate (VMD). However, despite annual prophylactic vaccination, bovine respiratory disease is still conservatively estimated to cost the UK economy approximately £80 million per annum. This review examines the vaccine types available, discusses the surrounding literature and scientific rationale of the limitations and assesses the potential of novel vaccine technologies.

The Combined Expression of the Non-structural Protein NS1 and the N-Terminal Half of NS2 (NS21-180) by ChAdOx1 and MVA Confers Protection against Clinical Disease in Sheep upon Bluetongue Virus Challenge

Bluetongue, caused by bluetongue virus (BTV), is a widespread arthropod-borne disease of ruminants that entails a recurrent threat to the primary sector of developed and developing countries. In this work, we report modified vaccinia virus Ankara (MVA) and ChAdOx1-vectored vaccines designed to simultaneously express the immunogenic NS1 protein and/or NS2-Nt, the N-terminal half of protein NS2 (NS2_1-180). A single dose of MVA or ChAdOx1 expressing NS1-NS2-Nt improved the protection conferred by NS1 alone in IFNAR(-/-) mice. Moreover, mice immunized with ChAdOx1/MVA-NS1, ChAdOx1/MVA-NS2-Nt, or ChAdOx1/MVA-NS1-NS2-Nt developed strong cytotoxic CD8⁺ T-cell responses against NS1, NS2-Nt, or both proteins and were fully protected against a lethal infection with BTV serotypes 1, 4, and 8. Furthermore, although a single immunization with ChAdOx1-NS1-NS2-Nt partially protected sheep against BTV-4, the administration of a booster dose of MVA-NS1-NS2-Nt promoted a faster viral clearance, reduction of the period and level of viremia and also protected from the pathology produced by BTV infection.

IMPORTANCE Current BTV vaccines are effective but they do not allow to distinguish between vaccinated and infected animals (DIVA strategy) and are serotype specific. In this work we have develop a DIVA multiserotype vaccination strategy based on adenoviral (ChAdOx1) and MVA vaccine vectors, the most widely used in current phase I and II clinical trials, and the conserved nonstructural BTV proteins NS1 and NS2. This immunization strategy solves the major drawbacks of the current marketed vaccines.

From Bench to Field: A Guide to Formulating and Evaluating Anti-Tick Vaccines Delving beyond Efficacy to Effectiveness

Ticks are ubiquitous blood-sucking ectoparasites capable of transmitting a wide range of pathogens such as bacteria, viruses, protozoa, and fungi to animals and humans. Although the use of chemicals (acaricides) is the predominant method of tick-control, there are increasing incidents of acaricide tick resistance. Furthermore, there are concerns over accumulation of acaricide residues in meat, milk and in the environment. Therefore, alternative methods of tick-control have been proposed, of which anti-tick cattle vaccination is regarded as sustainable and user-friendly. Over the years, tremendous progress has been made in identifying and evaluating novel candidate tick vaccines, yet none of them have reached the global market. Until now, Bm86-based vaccines (Gavac™ in Cuba and TickGARD^PLUS™ Australia-ceased in 2010) are still the only globally commercialized anti-tick vaccines. In contrast to Bm86, often, the novel candidate anti-tick vaccines show a lower protection efficacy. Why is this so? In response, herein, the potential bottlenecks to formulating efficacious anti-tick vaccines are examined. Aside from Bm86, the effectiveness of other anti-tick vaccines is rarely assessed. So, how can the researchers assess anti-tick vaccine effectiveness before field application? The approaches that are currently used to determine anti-tick vaccine efficacy are re-examined in this review. In addition, a model is proposed to aid in assessing anti-tick vaccine effectiveness. Finally, based on the principles for the development of general veterinary vaccines, a pipeline is proposed to guide in the development of anti-tick vaccines.

Heterologous prime-boost regimens with HAdV-5 and NDV vectors elicit stronger immune responses to Ebola virus than homologous regimens in mice

The 2014 Ebola outbreak in West Africa resulted in more than 11,000 deaths, highlighting the need for a vaccine. A phase I clinical trial of a human adenovirus type 5 vector-based Ebola virus (EBOV) vaccine (HAdV-5-MakGP) showed that a homologous prime-boost regimen with HAdV-5 vaccine elicited a robust humoral response but a weak cellular immune response. Due to pre-existing anti-vector immunity, boosting with the same vaccine did not increase the magnitude of the cellular immune response, which contributes significantly to protection against EBOV infection. Here, we generated a recombinant Newcastle disease virus (NDV), based on the LaSota vaccine strain, expressing the GP protein of the EBOV variant Makona (rLS/EB-GP) using reverse genetics technology. The humoral and cellular immune responses to this vaccine candidate in mice immunized using a homologous prime-boost regimen or a heterologous prime-boost regimen with the HAdV-5-vectored Ebola vaccine were assessed using ELISA and ELISPOT assays. The ELISA and ELISPOT results showed that mice primed with rLS/EB-GP and boosted with HAdV-5-MakGP (NDV+HAdV-5) or, reversed, primed with HAdV-5-MakGP and boosted with rLS/EB-GP (HAdV-5+NDV) exhibited more-potent EBOV GP-specific antibody and cellular immune responses than those receiving the same vaccine twice. The most robust EBOV GP-specific antibody and T-cell responses were detected in the HAdV-5-MakGP-primed and rLS/EB-GP-boosted (HAdV-5+NDV) mice. These results suggest that the HAdV-5 prime-NDV boost regimen is more effective in stimulating EBOV-specific immunity than homologous regimens alone, indicating the potential boosting ability of the NDV vector in human vaccine use.

The Immune Response to SARS-CoV-2 and Variants of Concern

At the end of 2019 a newly emerged betacoronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified as the cause of an outbreak of severe pneumonia, subsequently termed COVID-19, in a number of patients in Wuhan, China. Subsequently, SARS-CoV-2 rapidly spread globally, resulting in a pandemic that has to date infected over 200 million individuals and resulted in more than 4.3 million deaths. While SARS-CoV-2 results in severe disease in 13.8%, with increasing frequency of severe disease with age, over 80% of infections are asymptomatic or mild. The immune response is an important determinant of outcome following SARS-CoV-2 infection. While B cell and T cell responses are associated with control of infection and protection against subsequent challenge with SARS-CoV-2, failure to control viral replication and the resulting hyperinflammation are associated with severe COVID-19. Towards the end of 2020, several variants of concern emerged that demonstrate increased transmissibility and/or evasion of immune responses from prior SARS-CoV-2 infection. This article reviews what is known about the humoral and cellular immune responses to SARS-CoV-2 and how mutation and structural/functional changes in the emerging variants of concern impact upon the immune protection from prior infection or vaccination.

From infection to vaccination: reviewing the global burden, history of vaccine development, and recurring challenges in global leishmaniasis protection

INTRODUCTION

Leishmaniasis is a major public health problem and the second most lethal parasitic disease in the world due to the lack of effective treatments and vaccines. Even when not lethal, leishmaniasis significantly affects individuals and communities through life-long disabilities, psycho-sociological trauma, poverty, and gender disparity in treatment.

AREAS COVERED

This review discusses the most relevant and recent research available on Pubmed and GoogleScholar highlighting leishmaniasis' global impact, pathogenesis, treatment options, and lack of effective control strategies. An effective vaccine is necessary to prevent morbidity and mortality, lower health care costs, and reduce the economic burden of leishmaniasis for endemic low- and middle-income countries. Since there are several forms of leishmaniasis, a pan-Leishmania vaccine without geographical restrictions is needed. This review also focuses on recent advances and common challenges in developing prophylactic strategies against leishmaniasis.

EXPERT OPINION

Despite advances in pre-clinical vaccine research, approval of a human leishmaniasis vaccine still faces major challenges - including manufacturing of candidate vaccines under Good Manufacturing Practices, developing well-designed clinical trials suitable in endemic countries, and defined correlates of protection. In addition, there is a need to explore Challenge Human Infection Model to avoid large trials because of fluctuating incidence and prevalence of leishmanasis.

An approach to chimeric subunit immunogen provides efficient protection against toxicity, type III and type v secretion systems of Shigella

OBJECTIVES

Shigellosis is one of the infectious diseases causing severe intestinal illness in human beings. Development of an effective vaccine against Shigella is a key to deal with this bacterium. The present study aimed at evaluation of the antibody response as well as the protection of the recombinant chimeric protein containing IpaD, IpaB, StxB, and VirG against Shigella dysentery and flexneri.

METHODS

Chimeric protein was expressed and purified by Ni-NTA resin. The identity of the protein was determined by Western blot analysis. Mouse groups were immunized with the recombinant protein and the humoral immune response was measured by Enzyme-Linked Immunosorbent Assay (ELISA). Additionally, neutralization of the bacterial toxin by antibody was assessed by MTT assay. Animal challenge against S.dysentery and S. flexneri was evaluated, as well.

RESULTS

Protein expression and purification were confirmed by SDS-PAGE and western blotting. Analysis of the immune responses demonstrated that the antibody responses were higher in the sera of the subcutaneously immunized mice compared to those immunized intraperitoneally. In vitro neutralization analysis indicated that the 1:10000 dilution of the sera had a high ability to neutralize 0.25 ng/µl (CD50) of the toxin on the Vero cell line. Furthermore, the results of the animal challenge showed that the immunized mice were completely protected against 50 LD50 of the bacterial toxin. Immunization also protected 80% of the mice from 10 LD₅₀ by S. flexneri and S.dysentery. In addition, passive immunization conferred 60% protection in the mice against S. flexneri and S.dysentery. Organ burden studies also revealed a significant reduction in infection among the immunized mice.

CONCLUSION

This study revealed that the chimeric protein produced inE. colicould be a promising chimeric immunogen candidate against Shigella.

Anti-COVID-19 Vaccination in Patients with Autoimmune-Autoinflammatory Disorders and Primary/Secondary Immunodeficiencies: The Position of the Task Force on Behalf of the Italian Immunological Societies

The Coronavirus disease 2019 (COVID-19) pandemic has represented an unprecedented challenge for humankind from health, economic, and social viewpoints. In February 2020, Italy was the first western country to be deeply hit by the pandemic and suffered the highest case/fatality rate among western countries. Brand new anti-COVID-19 vaccines have been developed and made available in <1-year from the viral sequence publication. Patients with compromised immune systems, such as autoimmune-autoinflammatory disorders (AIAIDs), primary (PIDs) and secondary (SIDs) immunodeficiencies, have received careful attention for a long time regarding their capacity to safely respond to traditional vaccines. The Italian Immunological Societies, therefore, have promptly faced the issues of safety, immunogenicity, and efficacy/effectiveness of the innovative COVID-19 vaccines, as well as priority to vaccine access, in patients with AIADs, PIDs, and SIDs, by organizing an ad-hoc Task Force. Patients with AIADs, PIDs, and SIDs: (1) Do not present contraindications to COVID-19 vaccines if a mRNA vaccine is used and administered in a stabilized disease phase without active infection. (2) Should usually not discontinue immunosuppressive therapy, which may be modulated depending on the patient's clinical condition. (3) When eligible, should have a priority access to vaccination. In fact, immunizing these patients may have relevant social/health consequences, since these patients, if infected, may develop chronic infection, which prolongs viral spread and facilitates the emergence of viral variants.

Development of a subunit vaccine based on fiber2 and hexon against fowl adenovirus serotype 4

Hepatitis-hydropericardium syndrome (HHS) is widespread in China and causes high chicken mortality that results in great economic losses. A safe and effective vaccine is needed, and a subunit vaccine has potential for development. In this study, a truncated region of the FAdV-4 fiber 2 fused with coding sequence of one epitope of hexon was expressed in a prokaryotic expression system, and the immune protective effects of different doses of recombinant fiber 2 subunit vaccine on SPF chickens were compared. The recombinant fiber2 (Gly275- Pro479 aa)-hexon (Met21-Val51 aa) protein (rFH) obtained in Escherichia coli showed good solubility. The chicken survival rate at the lowest dose (2.5 μg/bird) was 75% (6/8), and at higher doses (≥5 μg/bird) was 100% (8/8) in challenge experiment. Two chickens in the 2.5 μg/bird treatment showed severe lesions, while birds in the higher dose treatments showed no obvious tissue damage as determined by histopathologic analysis of liver and spleen. Absolute quantitative real-time PCR showed no viral load in the ≥5 μg/bird treatments, but two chickens in the 2.5 μg/bird treatment had high viral loads. The challenge experience demonstrated that the rFH vaccine provided 100% protection at ≥5 μg/bird. These results suggested that rFH protein as an effective vaccine to protect against FAdV-4 and provided a new idea for the development of vaccine against HHS.

An Immunogenicity Report for the Comparison between Heterologous and Homologous Prime-Boost Schedules with ChAdOx1-S and BNT162b2 Vaccines

BACKGROUND

There is a small amount of immunological data on COVID-19 heterologous vaccination schedules in humans. We assessed the immunogenicity of BNT162b2 (Pfizer/BioNTech) administered as a second dose in healthcare workers primed with ChAdOx1-S (Vaxzevria, AstraZeneca).

METHODS

197 healthcare workers were included in a monocentric observational study in Foch hospital, France, between June and July 2021. The main outcome was the immunogenicity measured by serum SARS-CoV-2 IgG antibodies.

RESULTS

130 participants received the ChAdOx1-S/BNT vaccine and 67 received the BNT/BNT vaccine. The geometric mean of IgG antibodies was significantly higher in the BNT/BNT vaccine group compared to the ChAdOx1-S/BNT vaccine group, namely 10,734.9, 95% CI (9141.1-12,589.3) vs. 7268.6, 95% CI (6501.3-8128.3), respectively (p < 0.001). However, after adjustment for time duration between the prime and second vaccinations, no significant difference was observed (p = 0.181). A negative correlation between antibody levels and time duration between second dose and serology test was observed for the BNT/BNT vaccine (p < 0.001), which remained significant after adjustment for all covariates (p < 0.001), but not for the ChAdOx1-S/BNT vaccine (p = 0.467).

CONCLUSIONS

Heterologous and homologous schedules of ChAdOx1-S and BNT vaccines present robust immune responses after the second vaccination. The results observed were equivalent after adjustment for covariates and emphasize the importance of flexibility in deploying mRNA and viral vectored vaccines. Nevertheless, applying the ChAdOx1-S schedule vaccination for the heterologous second dose of BNT was associated with decreased IgG antibody levels compared to the homologous BNT/BNT vaccination.

A self-assembling nanoparticle: Implications for the development of thermostable vaccine candidates

Effective controls on viral infections rely on the continuous development in vaccine technology. Nanoparticle (NP) antigens are highly immunogenic based on their unique physicochemical properties, making them molecular scaffolds to present soluble vaccine antigens. Here, viral targets (113-354 aas) were genetically fused to N terminal of mi3, a protein that self-assembles into nanoparticles composed of 60 subunits. With transmission electron microscopy, it was confirmed that target-mi3 fusion proteins which have insertions of up to 354 aas in N terminal form intact NPs. Moreover, viral targets are surface-displayed on NPs as indicated in dynamic light scattering. NPs exhibit perfect stability after long-term storage at room temperature. Moreover, SP-E2-mi3 NPs enhance antigen uptake and maturation in dendritic cells (DCs) via up-regulating marker molecules and immunostimulatory cytokines. Importantly, in a mouse model, SP-E2-mi3 nanovaccines against Classical swine fever virus (CSFV) remarkably improved CSFV-specific neutralizing antibodies (NAbs) and cellular immunity related cytokines (IFN-γ and IL-4) as compared to monomeric E2. Specially, improved NAb response with more than tenfold increase in NAb titer against both CSFV Shimen and HZ-08 strains indicated better cross-protection against different genotypes. Collectively, this structure-based, self-assembling NP provides an attractive platform to improve the potency of subunit vaccine for emerging pathogens.

Self-Assembling Nanovaccine Enhances Protective Efficacy Against CSFV in Pigs

Classical swine fever virus (CSFV) is a highly contagious pathogen, which pose continuous threat to the swine industry. Though most attenuated vaccines are effective, they fail to serologically distinguish between infected and vaccinated animals, hindering CSFV eradication. Beneficially, nanoparticles (NPs)-based vaccines resemble natural viruses in size and antigen structure, and offer an alternative tool to circumvent these limitations. Using self-assembling NPs as multimerization platforms provides a safe and immunogenic tool against infectious diseases. This study presented a novel strategy to display CSFV E2 glycoprotein on the surface of genetically engineered self-assembling NPs. Eukaryotic E2-fused protein (SP-E2-mi3) could self-assemble into uniform NPs as indicated in transmission electron microscope (TEM) and dynamic light scattering (DLS). SP-E2-mi3 NPs showed high stability at room temperature. This NP-based immunization resulted in enhanced antigen uptake and up-regulated production of immunostimulatory cytokines in antigen presenting cells (APCs). Moreover, the protective efficacy of SP-E2-mi3 NPs was evaluated in pigs. SP-E2-mi3 NPs significantly improved both humoral and cellular immunity, especially as indicated by the elevated CSFV-specific IFN-γ cellular immunity and >10-fold neutralizing antibodies as compared to monomeric E2. These observations were consistent to in vivo protection against CSFV lethal virus challenge in prime-boost immunization schedule. Further results revealed single dose of 10 μg of SP-E2-mi3 NPs provided considerable clinical protection against lethal virus challenge. In conclusion, these findings demonstrated that this NP-based technology has potential to enhance the potency of subunit vaccine, paving ways for nanovaccine development.

Immunogenicity and reactogenicity of BNT162b2 booster in ChAdOx1-S-primed participants (CombiVacS): a multicentre, open-label, randomised, controlled, phase 2 trial

BACKGROUND

To date, no immunological data on COVID-19 heterologous vaccination schedules in humans have been reported. We assessed the immunogenicity and reactogenicity of BNT162b2 (Comirnaty, BioNTech, Mainz, Germany) administered as second dose in participants primed with ChAdOx1-S (Vaxzevria, AstraZeneca, Oxford, UK).

METHODS

We did a phase 2, open-label, randomised, controlled trial on adults aged 18-60 years, vaccinated with a single dose of ChAdOx1-S 8-12 weeks before screening, and no history of SARS-CoV-2 infection. Participants were randomly assigned (2:1) to receive either BNT162b2 (0·3 mL) via a single intramuscular injection (intervention group) or continue observation (control group). The primary outcome was 14-day immunogenicity, measured by immunoassays for SARS-CoV-2 trimeric spike protein and receptor binding domain (RBD). Antibody functionality was assessed using a pseudovirus neutralisation assay, and cellular immune response using an interferon-γ immunoassay. The safety outcome was 7-day reactogenicity, measured as solicited local and systemic adverse events. The primary analysis included all participants who received at least one dose of BNT162b2 and who had at least one efficacy evaluation after baseline. The safety analysis included all participants who received BNT162b2. This study is registered with EudraCT (2021-001978-37) and ClinicalTrials.gov (NCT04860739), and is ongoing.

FINDINGS

Between April 24 and 30, 2021, 676 individuals were enrolled and randomly assigned to either the intervention group (n=450) or control group (n=226) at five university hospitals in Spain (mean age 44 years [SD 9]; 382 [57%] women and 294 [43%] men). 663 (98%) participants (n=441 intervention, n=222 control) completed the study up to day 14. In the intervention group, geometric mean titres of RBD antibodies increased from 71·46 BAU/mL (95% CI 59·84-85·33) at baseline to 7756·68 BAU/mL (7371·53-8161·96) at day 14 (p<0·0001). IgG against trimeric spike protein increased from 98·40 BAU/mL (95% CI 85·69-112·99) to 3684·87 BAU/mL (3429·87-3958·83). The interventional:control ratio was 77·69 (95% CI 59·57-101·32) for RBD protein and 36·41 (29·31-45·23) for trimeric spike protein IgG. Reactions were mild (n=1210 [68%]) or moderate (n=530 [30%]), with injection site pain (n=395 [88%]), induration (n=159 [35%]), headache (n=199 [44%]), and myalgia (n=194 [43%]) the most commonly reported adverse events. No serious adverse events were reported.

INTERPRETATION

BNT162b2 given as a second dose in individuals prime vaccinated with ChAdOx1-S induced a robust immune response, with an acceptable and manageable reactogenicity profile.

FUNDING

Instituto de Salud Carlos III.

TRANSLATIONS

For the French and Spanish translations of the abstract see Supplementary Materials section.

A single subcutaneous or intranasal immunization with adenovirus-based SARS-CoV-2 vaccine induces robust humoral and cellular immune responses in mice

Optimal vaccines are needed for sustained suppression of SARS-CoV-2 and other novel coronaviruses. Here, we developed a recombinant type 5 adenovirus vector encoding the gene for the SARS-CoV-2 S1 subunit antigen (Ad5.SARS-CoV-2-S1) for COVID-19 immunization and evaluated its immunogenicity in mice. A single immunization with Ad5.SARS-CoV-2-S1 via S.C. injection or I.N delivery induced robust antibody and cellular immune responses. Vaccination elicited significant S1-specific IgG, IgG1, and IgG2a endpoint titers as early as 2 weeks, and the induced antibodies were long lasting. I.N. and S.C. administration of Ad5.SARS-CoV-2-S1 produced S1-specific GC B cells in cervical and axillary LNs, respectively. Moreover, I.N. and S.C. immunization evoked significantly greater antigen-specific T-cell responses compared to unimmunized control groups with indications that S.C. injection was more effective than I.N. delivery in eliciting cellular immune responses. Mice vaccinated by either route demonstrated significantly increased virus-specific neutralization antibodies on weeks 8 and 12 compared to control groups, as well as BM antibody forming cells (AFC), indicative of long-term immunity. Thus, this Ad5-vectored SARS-CoV-2 vaccine candidate showed promising immunogenicity following delivery to mice by S.C. and I.N. routes of administration, supporting the further development of Ad-based vaccines against COVID-19 and other infectious diseases for sustainable global immunization programs.

Combination immunotherapy with two attenuated Listeria strains carrying shuffled HPV-16 E6E7 protein causes tumor regression in a mouse tumor model

Cervical cancer continues to impose a heavy burden worldwide, and human papilloma virus (HPV) infection, especially persistent infection with type 16 (HPV-16), is known to be the primary etiological factor. Therapeutic vaccines are urgently needed because prophylactic vaccines are ineffective at clearing pre-existing HPV infection. Here, two recombinant Listeria strains (LMΔ-E6E7 & LIΔ-E6E7) with deletions of the actA and plcB genes, expressing the shuffled HPV-16 E6E7 protein were constructed. The strains were delivered into the spleen and liver by intravenous inoculation, induced antigen-specific cellular immunity and were eliminated completely from the internal organs several days later. Intravenously treating with single strain for three times, or with both strains alternately for three times significantly reduced the tumor size and prolonged the survival time of model mice. Combination immunotherapy with two strains seemed more effective than immunotherapy with single strain in that it enhanced the survival of the mice, and the LMΔ-E6E7-prime-LIΔ-E6E7-boost strategy showed significant stronger efficacy than single treatment with the LIΔ-E6E7 strain. The antitumor effect of this treatment might due to its ability to increase the proportion of CD8⁺ T cells and reduce the proportion of T regulatory cells (Tregs) in the intratumoral milieu. This is the first report regarding Listeria ivanovii-based therapeutic vaccine candidate against cervical cancer. Most importantly we are the first to confirm that combination therapy with two different recombinant Listeria strains has a more satisfactory antitumor effect than administration of a single strain. Thus, we propose a novel prime-boost treatment strategy.

The next generation of HCV vaccines: a focus on novel adjuvant development

INTRODUCTION

Considerable efforts have been made to treat and prevent acute and chronic infections caused by the hepatitis C virus (HCV). Current treatments are unable to protect people from reinfection. Hence, there is a need for development of both preventive and therapeutic HCV vaccines. Many vaccine candidates are in development to fight against HCV, but their efficacy has so far proven limited partly due to low immunogenicity.

AREAS COVERED

We explore development of novel and powerful adjuvants to achieve an effective HCV vaccine. The basis for developing strong adjuvants is to understand the innate immunity pathway, which subsequently stimulates humoral and cellular immune responses. We have also investigated immunogenicity of developed adjuvants that have been used in recent studies available in online databases such as PubMed, PMC, ScienceDirect, Google Scholar, etc.

EXPERT OPINION

Adjuvants are used as a part of vaccine formulation to boost vaccine immunogenicity and antigen delivery. Several FDA-approved adjuvants are used in licensed human vaccines. Unfortunately, no adjuvant has yet been proven to boost HCV immune responses to the extent needed for an effective vaccine. One of the promising approaches for developing an effective adjuvant is the combination of various adjuvants to trigger several innate immune responses, leading to activation of adaptive immunity.[Figure: see text].

HIV-1 Accessory Proteins: Which one is Potentially Effective in Diagnosis and Vaccine Development?

BACKGROUND

The combination antiretroviral therapy (cART) could increase the number of circulating naive CD4 T lymphocytes, but was not able to eradicate human immunodeficiency virus-1 (HIV-1) infection.

OBJECTIVE

Thus, induction of strong immune responses is important for control of HIV-1 infection. Furthermore, a simple and perfect serological method is required to detect virus in untreated-, treated- and drug resistant- HIV-1 infected individuals.

METHODS

This study was conducted to assess and compare immunogenic properties of Nef, Vif, Vpr and Vpu accessory proteins as an antigen candidate in mice and their diagnostic importance in human as a biomarker.

RESULTS

Our data showed that in mice, all heterologous prime/ boost regimens were more potent than homologous prime/ boost regimens in eliciting Th1 response and Granzyme B secretion as CTL activity. Moreover, the Nef, Vpu and Vif proteins could significantly increase Th1 immune response. In contrast, the Vpr protein could considerably induce Th2 immune response. On the other hand, among four accessory proteins, HIV-1 Vpu could significantly detect treated group from untreated group as a possible biomarker in human.

CONCLUSION

Generally, among accessory proteins, Nef, Vpu and Vif antigens were potentially more suitable vaccine antigen candidates than Vpr antigen. Human antibodies against all these proteins were higher in HIV-1 different groups than healthy group. Among them, Vpu was known as a potent antigen in diagnosis of treated from untreated individuals. The potency of accessory proteins as an antigen candidate in an animal model and a human cohort study are underway.

Vaccines in Gastrointestinal Malignancies: From Prevention to Treatment

Gastrointestinal (GI) malignancies are some of the most common and devastating malignancies and include colorectal, gastric, esophageal, hepatocellular, and pancreatic carcinomas, among others. Five-year survival rates for many of these malignancies remain low. The majority presents at an advanced stage with limited treatment options and poor overall survival. Treatment is advancing but not at the same speed as other malignancies. Chemotherapy and radiation treatments are still only partially effective in GI malignancies and cause significant side effects. Thus, there is an urgent need for novel strategies in the treatment of GI malignancies. Recently, immunotherapy and checkpoint inhibitors have entered as potential new therapeutic options for patients, and thus, cancer vaccines may play a major role in the future of treatment for these malignancies. Further advances in understanding the interaction between the tumor and immune system have led to the development of novel agents, such as cancer vaccines.

Pollution, Inflammation, and Vaccines: A Complex Crosstalk

The importance of pollution in determining human health is becoming increasingly clear, also given the dramatic consequences it has had on recent geopolitical events. Yet, the consequences of contamination are not always straightforward. In this paper, we will discuss the effects of different pollutants on different aspects of human health, in particular on the immune system and inflammation. Different environmental pollutants can have different effects on the immune system, which can then promote complex pathologies, such as autoimmune disorders and cancer. The interaction with the microbiota also further helps to determine the consequences of contamination on wellbeing. The pollution can affect vaccination efficacy, given the widespread effects of vaccination on immunity. At the same time, some vaccinations also can exert protective effects against some forms of pollution.

Prime-boost vaccination of mice and rhesus macaques with two novel adenovirus vectored COVID-19 vaccine candidates

ABSTRACTCOVID-19 vaccines are being developed urgently worldwide. Here, we constructed two adenovirus vectored COVID-19 vaccine candidates of Sad23L-nCoV-S and Ad49L-nCoV-S carrying the full-length gene of SARS-CoV-2 spike protein. The immunogenicity of two vaccines was individually evaluated in mice. Specific immune responses were observed by priming in a dose-dependent manner, and stronger responses were obtained by boosting. Furthermore, five rhesus macaques were primed with 5 × 10⁹ PFU Sad23L-nCoV-S, followed by boosting with 5 × 10⁹ PFU Ad49L-nCoV-S at 4-week interval. Both mice and macaques well tolerated the vaccine inoculations without detectable clinical or pathologic changes. In macaques, prime-boost regimen induced high titers of 10^3.16 anti-S, 10^2.75 anti-RBD binding antibody and 10^2.38 pseudovirus neutralizing antibody (pNAb) at 2 months, while pNAb decreased gradually to 10^1.45 at 7 months post-priming. Robust T-cell response of IFN-γ (712.6 SFCs/10⁶ cells), IL-2 (334 SFCs/10⁶ cells) and intracellular IFN-γ in CD4⁺/CD8⁺ T cell (0.39%/0.55%) to S peptides were detected in vaccinated macaques. It was concluded that prime-boost immunization with Sad23L-nCoV-S and Ad49L-nCoV-S can safely elicit strong immunity in animals in preparation of clinical phase 1/2 trials.

Assessing the risk of recurrence of porcine epidemic diarrhea virus in affected farms on Jeju Island, South Korea

Background

Porcine epidemic diarrhea virus (PEDV) is a swine enteropathogenic coronavirus that has devastated the swine industry in South Korea over the last 30 years. The lack of an effective method to control the endemics has led to a surge in PEDV recurrences in affected farms throughout the country.

Objectives

In the first step toward establishing systematic monitoring of and active control measures over the swine populations, we constructed an assessment model that evaluates the status of (1) biosecurity, (2) herd immunity, and (3) virus circulation in each of the PEDV-infected farms.

Methods

A total of 13 farrow-to-finish pig farms with a history of acute PEDV infection on Jeju Island were chosen for this study. The potential risk of the recurrence in these farms was estimated through on-site data collection and laboratory examination.

Results

Overall, the data indicated that a considerable number of the PEDV-infected farms had lax biosecurity, achieved incomplete protective immunity in the sows despite multi-dose vaccination, and served as incubators of the circulating virus; thus, they face an increased risk of recurrent outbreaks. Intriguingly, our results suggest that after an outbreak, a farm requires proactive tasks, including reinforcing biosecurity, conducting serological and virus monitoring to check the sows’ immunity and to identify the animals exposed to PEDV, and improving the vaccination scheme and disinfection practices if needed.

Conclusions

The present study highlights the significance of coordinated PEDV management in infected farms to reduce the risk of recurrence and further contribute towards the national eradication of PEDV.

Comparison of the immune response following subcutaneous versus intranasal modified-live virus booster vaccination against bovine respiratory disease in pre-weaning beef calves that had received primary vaccination by the intranasal route

This study was performed to elucidate whether the route of booster vaccination affects the immune response against respiratory vaccine viruses in pre-weaning beef calves that receive primary intranasal (IN) vaccination during the first month of life. The objective was to compare the serum neutralizing antibody (SNA) titers to BHV1, BRSV, and BPI3V, cytokine mRNA expression and mucosal BHV1- and BRSV-specific IgA in nasal secretions following administration of IN or subcutaneous (SC) modified-live virus (MLV) booster vaccines 60 days after primary IN vaccination in young beef calves. Twenty-one beef calves were administered 2 mL of an IN MLV vaccine containing BHV1, BRSV, and BPI3V (Inforce3®) between one and five weeks of age. Sixty days after primary vaccination, calves were randomly assigned to one of two groups: IN-MLV (n = 11): Calves received 2 mL of the same IN MLV vaccine used for primary vaccination and 2 mL of a SC MLV vaccine containing BVDV1 & 2 (Bovi- Shield GOLD® BVD). SC-MLV (n = 10): Calves were administered 2 mL of a MLV vaccine containing, BHV1, BRSV, BPI3V, and BVDV1 & 2 (Bovi-Shield GOLD® 5). Blood and nasal secretion samples were collected on days -61 (primary vaccination), -28, -14, 0 (booster vaccination), 14, 21, 28, 42 and 60 for determination of SNA titers, cytokine gene expression analysis and nasal virus-specific IgA concentrations. Statistical analysis was performed using a repeated measures analysis through PROC GLIMMIX of SAS®. Booster vaccination by neither IN nor SC routes induced a significant increase in SNA titers against BHV1, BRSV, and BPI3V. Subcutaneous booster vaccination induced significantly greater BRSV-specific SNA titers (on day 42) and IgA concentration in nasal secretions (on days 21 and 42) compared to calves receiving IN booster vaccination. Both IN and SC booster vaccination were able to stimulate the production of BHV1-specific IgA in nasal secretions. In summary, booster vaccination of young beef calves using either SC or IN route two months after IN MLV primary vaccination resulted in comparable SNA titers, cytokine gene expression profile and virus-specific IgA concentration in nasal secretions. Only a few differences in the systemic and mucosal immune response against BHV1 and BRSV were observed. Subcutaneous booster vaccination induced significantly greater BRSV-specific SNA and secretory IgA titers compared to IN booster vaccination.

Enhanced dengue vaccine virus replication and neutralizing antibody responses in immune primed rhesus macaques

Antibody-dependent enhancement (ADE) is suspected to influence dengue virus (DENV) infection, but the role ADE plays in vaccination strategies incorporating live attenuated virus components is less clear. Using a heterologous prime-boost strategy in rhesus macaques, we examine the effect of priming with DENV purified inactivated vaccines (PIVs) on a tetravalent live attenuated vaccine (LAV). Sera exhibited low-level neutralizing antibodies (NAb) post PIV priming, yet moderate to high in vitro ADE activity. Following LAV administration, the PIV primed groups exhibited DENV-2 LAV peak viremias up to 1,176-fold higher than the mock primed group, and peak viremia correlated with in vitro ADE. Furthermore, PIV primed groups had more balanced and higher DENV-1–4 NAb seroconversion and titers than the mock primed group following LAV administration. These results have implications for the development of effective DENV vaccine prime-boost strategies and for our understanding of the role played by ADE in modulating DENV replication.

Mice Immunized with the Vaccine Candidate HexaPro Spike Produce Neutralizing Antibodies against SARS-CoV-2

Updated and revised versions of COVID-19 vaccines are vital due to genetic variations of the SARS-CoV-2 spike antigen. Furthermore, vaccines that are safe, cost-effective, and logistic-friendly are critically needed for global equity, especially for middle- to low-income countries. Recombinant protein-based subunit vaccines against SARS-CoV-2 have been reported using the receptor-binding domain (RBD) and the prefusion spike trimers (S-2P). Recently, a new version of prefusion spike trimers, named HexaPro, has been shown to possess two RBD in the “up” conformation, due to its physical property, as opposed to just one exposed RBD found in S-2P. Importantly, this HexaPro spike antigen is more stable than S-2P, raising its feasibility for global logistics and supply chain. Here, we report that the spike protein HexaPro offers a promising candidate for the SARS-CoV-2 vaccine. Mice immunized by the recombinant HexaPro adjuvanted with aluminum hydroxide using a prime-boost regimen produced high-titer neutralizing antibodies for up to 56 days after initial immunization against live SARS-CoV-2 infection. Also, the level of neutralization activity is comparable to that of convalescence sera. Our results indicate that the HexaPro subunit vaccine confers neutralization activity in sera collected from mice receiving the prime-boost regimen.

A Nanoscaffolded Spike-RBD Vaccine Provides Protection against SARS-CoV-2 with Minimal Anti-Scaffold Response

The response of the adaptive immune system is augmented by multimeric presentation of a specific antigen, resembling viral particles. Several vaccines have been designed based on natural or designed protein scaffolds, which exhibited a potent adaptive immune response to antigens; however, antibodies are also generated against the scaffold, which may impair subsequent vaccination. In order to compare polypeptide scaffolds of different size and oligomerization state with respect to their efficiency, including anti-scaffold immunity, we compared several strategies of presentation of the RBD domain of the SARS-CoV-2 spike protein, an antigen aiming to generate neutralizing antibodies. A comparison of several genetic fusions of RBD to different nanoscaffolding domains (foldon, ferritin, lumazine synthase, and β-annulus peptide) delivered as DNA plasmids demonstrated a strongly augmented immune response, with high titers of neutralizing antibodies and a robust T-cell response in mice. Antibody titers and virus neutralization were most potently enhanced by fusion to the small β-annulus peptide scaffold, which itself triggered a minimal response in contrast to larger scaffolds. The β-annulus fused RBD protein increased residence in lymph nodes and triggered the most potent viral neutralization in immunization by a recombinant protein. Results of the study support the use of a nanoscaffolding platform using the β-annulus peptide for vaccine design.

Safety and Immunogenicity of Adenovirus and Poxvirus Vectored Vaccines against a Mycobacterium Avium Complex Subspecies

Heterologous prime-boost strategies are known to substantially increase immune responses in viral vectored vaccines. Here we report on safety and immunogenicity of the poxvirus Modified Vaccinia Ankara (MVA) vectored vaccine expressing four Mycobacterium avium subspecies paratuberculosis antigens as a single dose or as a booster vaccine following a simian adenovirus (ChAdOx2) prime. We demonstrate that a heterologous prime-boost schedule is well tolerated and induced T-cell immune responses.

Zika virus-an update on the current efforts for vaccine development

In 2015, the world witnessed the resurgence and global spread of Zika virus (ZIKV). This arbovirus infection is associated with Guillain-Barré syndrome in adults and with devastating congenital malformations during pregnancy. Despite scientific efforts, the development of a vaccine capable of inducing long-term protection has been challenging. Without a safe and efficacious licensed vaccine, control of virus transmission is based on vector control, but this strategy has been shown to be inefficient. An effective and protective vaccine relies on several requirements, which include: (i) induction of specific immune response against immunodominant antigens; (ii) selection of adjuvant-antigen formulation; and (iii) assessment of safety, effectiveness, and long-term protection. In this commentary, we provide a brief overview about the current efforts for the development of an efficacious ZIKV vaccine, covering the most important preclinical trials up to the formulations that are now being evaluated in clinical trials.