An mpox virus mRNA-lipid nanoparticle vaccine confers protection against lethal orthopoxviral challenge

An overview of the progress made in research into the Mpox virus

Mpox is a zoonotic illness caused by the Mpox virus (MPXV), a member of the Orthopoxvirus family. Although a few cases have been reported outside Africa, it was originally regarded as an endemic disease limited to African countries. However, the Mpox outbreak of 2022 was remarkable in that the infection spread to more than 123 countries worldwide, causing thousands of infections and deaths. The ongoing Mpox outbreak has been declared as a public health emergency of international concern by the World Health Organization. For a better management and control of the epidemic, this review summarizes the research advances and important scientific findings on MPXV by reviewing the current literature on epidemiology, clinical characteristics, diagnostic methods, prevention and treatment measures, and animal models of MPXV. This review provides useful information to raise awareness about the transmission, symptoms, and protective measures of MPXV, serving as a theoretical guide for relevant institutions to control MPXV.

Structural insights into tecovirimat antiviral activity and poxvirus resistance

Mpox is a zoonotic disease endemic to Central and West Africa. Since 2022, two human-adapted monkeypox virus (MPXV) strains have caused large outbreaks outside these regions. Tecovirimat is the most widely used drug to treat mpox. It blocks viral egress by targeting the viral phospholipase F13; however, the structural details are unknown, and mutations in the F13 gene can result in resistance against tecovirimat, raising public health concerns. Here we report the structure of an F13 homodimer using X-ray crystallography, both alone (2.1 Å) and in complex with tecovirimat (2.6 Å). Combined with molecular dynamics simulations and dimerization assays, we show that tecovirimat acts as a molecular glue that promotes dimerization of the phospholipase. Tecovirimat resistance mutations identified in clinical MPXV isolates map to the F13 dimer interface and prevent drug-induced dimerization in solution and in cells. These findings explain how tecovirimat works, allow for better monitoring of resistant MPXV strains and pave the way for developing more potent and resilient therapeutics.

Lessons for Medical Countermeasure Development from Unforeseen Outbreaks

The unanticipated emergence of the COVID-19 pandemic and the rapid spread of the mpox epidemic in 2022 and in 2024 brought unforeseen challenges to public health. While distinct in nature, these outbreaks share some similarities and offer valuable insights into responding to novel virus dissemination in vulnerable populations. In light of these two experiences, we aim to discern the prioritization of medical countermeasures (MCM) among antivirals, antibodies and vaccines.Comparative analysis of MCMs reveals that while antivirals serve essential roles as therapeutic tools, monoclonal antibodies can be used for both prevention and treatment, and vaccines remain of paramount importance for controlling epidemics as mass or targeted prophylaxis. Variability in production processes, administration methods, logistics, and costs distinguish these countermeasures. Vaccines, by inducing long-lasting immunity and ideally promoting herd effects, exhibit substantial advantages over other options.To enhance future pandemic readiness, proactive measures must include ready to use vaccine platforms with regulatory approval and manufacturing capacities, as well as prototype vaccines for representative pathogens and preexisting protocols to evaluate their efficacities and side effects. The comparison underscores the challenges of social acceptance and equity, particularly in vaccine production and distribution. As the world faces unknown agents, the 3 major types of MCMs do not have equal and symmetrical effects in terms of epidemic control. Thus, a vaccine-oriented strategy with a community-centered approach, proves essential for effective pandemic preparedness, encouraging continued innovation in vaccinology.

Inhibition of Polo-Like Kinase 1 Dampens the Replication of Vaccinia Virus in Mammalian Cells

Since the eradication of smallpox, zoonotic poxviruses, such as the mpox virus (MPXV), continue to pose a threat to public health. Identifying drugs that reduce poxvirus infection and replication, as well as understanding their molecular mechanisms, is essential for epidemic control. Polo-like kinase 1 (PLK1) has been shown to facilitate vaccinia virus (VACV) infection and replication. This study confirms the effects of the PLK1 inhibitors HMN-214 and ON-01910 on VACV replication in A549 cells. Both viral titers and DNA loads were significantly reduced in treated cells after infection. Additionally, ON-01910 demonstrated broad-spectrum antiviral activity against the lumpy skin disease virus (LSDV) and the infectious bovine rhinotracheitis virus (IBRV) in vitro. PLK1 knockdown in A549 cells also led to a reduction in VACV protein expression, viral titers, and DNA levels. Further analysis showed that VACV infection leads to the accumulation of PLK1 near viral factories. However, despite its strong in vitro effects, ON-01910 did not significantly reduce VACV replication in mice. These findings highlight the critical role of PLK1 in VACV replication and its potential as a target for antiviral therapy against orthopoxviruses.

Mpox treatment evolution: past milestones, present advances, and future directions

An underestimated worldwide health concern, Monkeypox (Mpox) is becoming a bigger menace to the world's population. After smallpox was eradicated in 1970, Mpox was found in a rural region of Africa and quickly spread to other African countries. The etiological agent of the Mpox infection, the Mpox virus, is constantly evolving, and its capability for cross-species transmission led to a global outbreak in 2022 which led to several deaths throughout the world. This review aims to showcase the progressive treatment methods and emerging innovations in the diagnostic and prevention strategies for controlling Mpox. The clinical trial data for antiviral drugs were systematically collected and analyzed using statistical tests to determine the most effective antiviral treatment. Emerging viral protein inhibitors that are under investigation for Mpox treatment were also scrutinized in this review. Additionally, modern diagnostic methods, such as the Streamlined CRISPR On Pod Evaluation platform (SCOPE) and graphene quantum rods were reviewed, and the efficacy of mRNA vaccines with traditional smallpox vaccines used for Mpox were compared. The statistical analysis revealed that tecovirimat (TCV) is the most effective antiviral drug among the other evaluated drugs, showing superior efficacy in clinical trials. Similarly, mRNA vaccines offer greater effectiveness compared to conventional smallpox vaccines. Furthermore, emerging nanomedicine and herbal drug candidates were highlighted as potential future treatments for Mpox. The findings underscore the effectiveness of TCV in treating Mpox and highlight significant advancements in preventive treatments. The review also points to innovative approaches in vaccine technology and potential future therapies, including nanomedicine and herbal remedies, which may enhance Mpox management.

Elucidating the Mechanism of VVTT Infection Through Machine Learning and Transcriptome Analysis

The vaccinia virus (VV) is extensively utilized as a vaccine vector in the treatment of various infectious diseases, cardiovascular diseases, immunodeficiencies, and cancers. The vaccinia virus Tiantan strain (VVTT) has been instrumental as an irreplaceable vaccine strain in the eradication of smallpox in China; however, it still presents significant adverse toxic effects. After the WHO recommended that routine smallpox vaccination be discontinued, the Chinese government stopped the national smallpox vaccination program in 1981. The outbreak of monkeypox in 2022 has focused people's attention on the Orthopoxvirus. However, there are limited reports on the safety and toxic side effects of VVTT. In this study, we employed a combination of transcriptomic analysis and machine learning-based feature selection to identify key genes implicated in the VVTT infection process. We utilized four machine learning algorithms, including random forest (RF), minimum redundancy maximum relevance (MRMR), eXtreme Gradient Boosting (XGB), and least absolute shrinkage and selection operator cross-validation (LASSOCV), for feature selection. Among these, XGB was found to be the most effective and was used for further screening, resulting in an optimal model with an ROC curve of 0.98. Our analysis revealed the involvement of pathways such as spinocerebellar ataxia and the p53 signaling pathway. Additionally, we identified three critical targets during VVTT infection-ARC, JUNB, and EGR2-and further validated these targets using qPCR. Our research elucidates the mechanism by which VVTT infects cells, enhancing our understanding of the smallpox vaccine. This knowledge not only facilitates the development of new and more effective vaccines but also contributes to a deeper comprehension of viral pathogenesis. By advancing our understanding of the molecular mechanisms underlying VVTT infection, this study lays the foundation for the further development of VVTT. Such insights are crucial for strengthening global health security and ensuring a resilient response to future pandemics.

Approaches to Next-Generation Capripoxvirus and Monkeypox Virus Vaccines

Globally, there are two major poxvirus outbreaks: mpox, caused by the monkeypox virus, and lumpy skin disease, caused by the lumpy skin disease virus. While vaccines for both diseases exist, there is a need for improved vaccines. The original vaccines used to eradicate smallpox, which also protect from the disease now known as mpox, are no longer acceptable. This is mainly due to the risk of serious adverse events, particularly in HIV-positive people. The next-generation vaccine for mpox prevention is modified vaccinia Ankara, which does not complete the viral replication cycle in humans and, therefore, has a better safety profile. However, two modified vaccinia Ankara immunizations are needed to give good but often incomplete protection, and there are indications that the immune response will wane over time. A better vaccine that induces a long-lived response with only one immunization is desirable. Another recently available smallpox vaccine is LC16m8. While LC16m8 contains replicating vaccinia virus, it is a more attenuated vaccine than the original vaccines and has limited side effects. The commonly used lumpy skin disease vaccines are based on attenuated lumpy skin disease virus. However, an inactivated or non-infectious vaccine is desirable as the disease spreads into new territories. This article reviews novel vaccine approaches, including mRNA and subunit vaccines, to protect from poxvirus infection.

Current advances and challenges in mpox vaccine development: a global landscape

Given the surge in mpox outbreaks in 2022 and the advancements in domestic and international vaccine research, the effectiveness of smallpox vaccines in providing cross-protection against mpox remains crucial. Having learned from the COVID-19 pandemic, it is significant to continue evaluating existing vaccines to ensure their safety and efficacy. Developing new vaccines for widespread use against mpox and its emerging strains also serves as a preventive strategy in the ongoing battle against this dynamic infection. Here's an opportunity to control human-to-human transmission, give short deadlines, and avoid vaccine disparity. Public health systems must take decisive action to prevent the global spread of mpox, particularly among vulnerable groups. This action should include strengthening global surveillance, improving vaccine access, and ensuring equitable distribution, particularly in resource-poor settings, to prevent future outbreaks. This review aims to assess recent advancements and barriers in mpox vaccine development, emphasizing cross-protection and equitable vaccine distribution in resource-poor settings.

Assessment of MpoxPlex, a high-throughput and multiplexed immunoassay: a diagnostic accuracy study

BACKGROUND

In May, 2022, the first global outbreak of mpox (formerly known as monkeypox) occurred. In response, public health agencies in the UK have made smallpox vaccines available to individuals at the highest risk of infection. With mpox cases still being detected globally, novel tools are required to aid with diagnosis, serosurveillance, and the evaluation of immune responses following infection and immunisation with current and new vaccine candidates. Here, we describe the development of a multiplexed immunoassay, MpoxPlex, able to measure IgG responses to 12 Orthopoxvirus antigens concurrently and distinguish between responses to infection and vaccination.

METHODS

Using the Luminex (DiaSorin, Saluggia, Italy) platform, antibody responses to vaccinia virus (VACV) antigens B5, A27, and A33 and monkeypox virus (MPXV) antigens E8, B6, B2, M1, A27, A35, H3, A29, and A5 were assessed in serum from individuals after MPXV infection (n=24) and after vaccination (n=75) with modified VACV Ankara-Bavarian Nordic. Assay characteristics and cutoffs were calculated by fitting receiver operating characteristic curves to the median fluorescence intensities of these positive samples and negative samples that were run alongside (n=435). P values were calculated using non-parametric Mann-Whitney, Kruskal-Wallis, and Dunn's multiple comparisons tests.

FINDINGS

Using the results from a combination of eight antigens, we were able to distinguish samples as either post-vaccination or post-infection from negative samples with a sensitivity of 98% and a specificity of 95%. IgG responses to MPXV antigen A27 were able to distinguish post-MPXV infection with a sensitivity of 88% and a specificity of 97%. VACV antigen A27 and MPXV antigens A29 and A5 provided little diagnostic advantage.

INTERPRETATION

With additional benefits over current serological assays, we believe this assay will provide substantial insight into the current global outbreak of mpox. MpoxPlex shows use for both serosurveillance and immunological studies of vaccination and infection.

FUNDING

Grant-in-aid funding to the Emerging Pathogen Serology Group at Porton Down, UK Health Security Agency.

Enhanced Immunogenicity and Affinity with A35R-Fc-Based Chimeric Protein Compared to MPXV A35R Protein

The re-emergence of the mpox pandemic poses considerable challenges to human health and societal development. There is an urgent need for effective prevention and treatment strategies against the mpox virus (MPXV). In this study, we focused on the A35R protein and created a chimeric A35R-Fc protein by fusing the Fc region of IgG to its C-terminal. We then assessed its reactivity with A35R-specific antibodies and human convalescent plasma, as well as its immunogenicity. Our findings indicate that the A35R-Fc protein significantly enhances affinity to A35R antibodies compared to the commercially available A35R protein and exhibits considerable reactivity to human plasma. Additionally, mice immunized with A35R-Fc exhibited increased neutralizing antibody titers against the live MPXV. These results support the potential of Fc domain chimeric antigens as a strategy to enhance the efficacy of subunit vaccines targeting the MPXV.

Long-Lasting Protection and Dose Optimization of MPXV Polyvalent Mpox mRNA Vaccines Against Lethal Vaccinia Virus Challenge in Mice

The outbreak of clade II monkeypox virus (MPXV) and the additional outbreak in Central Africa of clade I virus from 2023 have attracted worldwide attention. The development of a scalable and effective vaccine against the ongoing epidemic of mpox is urgently needed. We previously constructed two bivalent MPXV mRNA vaccines, LBA (B6R-A29L) and LAM (A35R-M1R), and a quadrivalent mRNA vaccine, LBAAM (B6R-A35R-A29L-M1R). These vaccines at a 20 µg dose could induce potential MPXV antigen-specific immune responses and provide protection against lethal VACV challenge. Compared with the individual bivalent mRNA vaccines, the two quadrivalent vaccines LBAAM and LBA& LAM displayed superior protective effects. To characterize these vaccines further, we monitored long-term immunity and protection as long as 28 weeks after initial immunization and optimized the immunization dosages to decrease the cost of production for future clinical use. Our results demonstrated that both the bivalent MPXV mRNA vaccine LAM (A35R-M1R) and the two tetravalent vaccines LBAAM and LBA& LAM could elicit long-lasting antigen-specific IgG antibodies as well as neutralizing antibodies against VACV and MPXV. They all provided complete protection against VACV challenge until 28 weeks post prime immunization. Moreover, the immunogenicity and protective efficacy of the two tetravalent vaccines (LBAAM and LBA& LAM) are dose dependent, and even the low-dose (1 µg) vaccine could provide sufficient protection against lethal VACV challenge. These results provide valuable clues for the further production of MPXV mRNA vaccines for use in humans.

Immunobiology of MPox Infection and Its Management: Experience From Developing Nations

PURPOSE

As humanity grapples with the COVID-19 pandemic caused by the novel SARS-CoV-2 virus, the rising threats of the MPox virus (MPXV) in 2022 and 2024 have shown signs of global transmission and the potential to spark another pandemic. Though MPXV has been present for over 5 decades, with cases traditionally confined to endemic regions in West and Central Africa, recent outbreaks have occurred in multiple non-endemic regions, declaring itself as a Public Health Emergency of International Concern. This study aims to examine the patterns of MPXV transmission, its zoonotic potential, associated complications, and viable strategies to control its spread.

METHODS

The study examines recent outbreak data, case reports, and literature on MPXV transmission, emphasising zoonotic pathways and healthcare-associated cases. A bibliometric analysis has also been performed to deepen the understanding and identify emerging research trends.

RESULTS

The findings suggest that while MPXV has traditionally been endemic in certain regions of Africa, recent outbreaks indicate an increased transmission risk in non-endemic countries, raising concerns about potential global spread. Data reveals that much of the transmission has occurred within healthcare settings. Additionally, global research on the outbreak remains limited and requires further exploration from various perspectives, emphasising the need for prompt intervention.

CONCLUSION

Containing MPXV's spread is essential to prevent another potential pandemic. Effective management and control strategies, including enhanced surveillance, public health interventions, and targeted education within at-risk communities, are critical to mitigate the spread and impact of MPXV globally. This study advocates for a proactive approach to MPXV control to avoid its escalation into a widespread health crisis.

Mpox mRNA-1769 vaccine inhibits orthopoxvirus replication at intranasal, intrarectal, and cutaneous sites of inoculation

We previously reported that mice immunized twice with a lipid nanoparticle vaccine comprising four monkeypox viral mRNAs raised neutralizing antibodies and antigen-specific T cells and were protected against a lethal intranasal challenge with vaccinia virus (VACV). Here we demonstrated that the mRNA vaccine also protects mice against intranasal and intraperitoneal infections with monkeypox virus and bioluminescence imaging showed that vaccination greatly reduces or prevents VACV replication and spread from intranasal, rectal, and dermal inoculation sites. A single vaccination provided considerable protection that was enhanced by boosting for at least 4 months. Protection was related to the amount of mRNA inoculated, which correlated with neutralizing antibody levels. Furthermore, immunocompetent and immunodeficient mice lacking mature B and T cells that received serum from mRNA-immunized macaques before or after VACV challenge were protected. These findings provide insights into the mechanism and extent of mRNA vaccine-induced protection of orthopoxviruses and support clinical testing.

A penta-component mpox mRNA vaccine induces protective immunity in nonhuman primates

The recent worldwide outbreaks of mpox prioritize the development of a safe and effective mRNA vaccine. The contemporary mpox virus (MPXV) exhibits changing virological and epidemiological features, notably affecting populations already vulnerable to human immunodeficiency virus (HIV). Herein, we profile the immunogenicity of AR-MPXV5, a penta-component mRNA vaccine targeting five specific proteins (M1R, E8L, A29L, A35R, and B6R) from the representative contemporary MPXV clade II strain, in both naive and simian immunodeficiency virus (SIV)-infected nonhuman primates. Immunization with two doses of AR-MPXV5 to cynomolgus macaques effectively elicits antibody responses and cellular responses. Importantly, based on the challenge model with a contemporary MPXV clade II strain, AR-MPXV5 demonstrates effective efficacy in preventing skin lesions, eliminating viremia and reducing viral loads in multiple tissues after challenge in naive male animals. More importantly, AR-MPXV5 is well-tolerated in stable chronic SIV-infected rhesus monkeys, while eliciting comparable MPXV-specific humoral and cellular responses in both naive and SIV-infected monkeys. Together, these results support further clinical development of the AR-MPXV5 vaccine.

MVA-BN vaccine effectiveness: A systematic review of real-world evidence in outbreak settings

BACKGROUND

Mpox is a disease endemic to Central and West Africa. It caused outbreaks in non-endemic countries, mainly in 2022. The endemic Democratic Republic of Congo is currently experiencing its largest outbreak yet. The vaccine Modified Vaccinia Ankara-Bavarian Nordic (MVA-BN) is approved for active immunization against mpox and smallpox. Since the outbreak in 2022, real-world studies have assessed MVA-BN's vaccine effectiveness (VE) against mpox, and this systematic literature review aims to summarize the most current evidence.

METHODS

Medline (via PubMed), Embase, and LILACS were searched, as well as grey literature sources and publications' bibliographies to identify observational studies published between 1/Jan/2022 and 28/Feb/2024 that estimate the VE of MVA-BN against mpox or provide risk measures that allow calculation of these VE estimates. Data were presented descriptively in tables and text; the methodological quality of included records was assessed using NHLBI/NIH quality assessment tools.

RESULTS

The literature search identified 16 records that fit the inclusion criteria. The studies took place in high-income countries and were heterogeneous in design, setting, and definition of at-risk populations. MVA-BN VE estimates against mpox infection were assessed. Where the study population was exclusively or primarily those receiving pre-exposure prophylactic vaccination, the adjusted VE estimates ranged from 35 % to 86 % (n = 8 studies) for one dose and from 66 % to 90 % (n = 5) for two doses. Where only post-exposure prophylactic vaccination was assessed, adjusted VE estimates were reported for one dose only at 78 % and 89 % (n = 2). Additionally, MVA-BN reduced the risk of mpox-related hospitalization in one study and the severity of mpox clinical manifestations in two studies.

CONCLUSIONS

Despite heterogeneity in study design, setting, and at-risk populations, the reported VE estimates against mpox infection demonstrated the effectiveness of one or two doses of MVA-BN in the context of an outbreak across multiple countries.

Advanced technologies for the development of infectious disease vaccines

Vaccines play a critical role in the prevention of life-threatening infectious disease. However, the development of effective vaccines against many immune-evading pathogens such as HIV has proven challenging, and existing vaccines against some diseases such as tuberculosis and malaria have limited efficacy. The historically slow rate of vaccine development and limited pan-variant immune responses also limit existing vaccine utility against rapidly emerging and mutating pathogens such as influenza and SARS-CoV-2. Additionally, reactogenic effects can contribute to vaccine hesitancy, further undermining the ability of vaccination campaigns to generate herd immunity. These limitations are fuelling the development of novel vaccine technologies to more effectively combat infectious diseases. Towards this end, advances in vaccine delivery systems, adjuvants, antigens and other technologies are paving the way for the next generation of vaccines. This Review focuses on recent advances in synthetic vaccine systems and their associated challenges, highlighting innovation in the field of nano- and nucleic acid-based vaccines.

Viral infection and antiviral immunity in the oral cavity

Individual tissues have distinct antiviral properties garnered through various mechanisms, including physical characteristics, tissue-resident immune cells and commensal organisms. Although the oral mucosa has long been appreciated as a critical barrier tissue that is exposed to a continuous barrage of pathogens, many fundamental aspects of the antiviral immune response in this tissue remain unknown. Several viral pathogens, such as herpesviruses and human papillomaviruses, have been acknowledged both historically and at present for infections in the oral cavity that result in substantial clinical burden. However, recent viral outbreaks, including those with SARS-CoV-2 and mpox, featured oral symptoms even though these viruses are not generally considered oral pathogens. Ensuing studies have shown that the oral cavity is an important locale for viral infection and potential transmission of newly emergent or re-emergent pathogens, highlighting the need for an increased understanding of the mechanisms of antiviral immunity at this site. In this Review, we provide a broad overview of antiviral immune responses in the oral cavity and discuss common viral infections and their manifestations in the oral mucosa. In addition, we present current mouse models for the study of oral viral infections.

Different immunogens and prime-boost vaccination strategies affect the efficacy of recombinant candidate vaccines against pathogenic orthopoxviruses

Although not as lethal as variola virus (VARV), the cause of smallpox, monkeypox virus (MPXV) represents a threat to public health, with important infection rates and mortality in several African countries and signs of spreading worldwide. MPXV may establish new reservoirs in non-endemic countries and can be considered a possible biological weapon. Human-to-human MPXV transmission is increasing with a growing susceptibility, coincident with the declining herd immunity against smallpox. The emerging threat of MPXV highlights the urgent need for protection from new zoonotic infections, as mankind is completely unprepared for encounters with new viruses. Preventive vaccination remains the most effective control against orthopoxviruses (OPXVs) such as MPXV and prime-boost vaccination strategies can significantly influence vaccine efficacy and enhance immune responses. Our study aimed at characterizing potential vaccine candidates against OPXV infections in a murine model using DNA, viral and protein recombinant vaccines using different prime-boost regimens. The experiments employed Vaccinia virus (VACV) A33, B5, L1, and A27 envelope proteins as immunogens for both priming and boosting. Priming was carried out using a mixture of four plasmids (4pVAXmix), and boosts employed fowlpox (FWPV) recombinants (4FPmix) and/or the purified recombinant proteins (4protmix), all of them expressing the same antigens. One or two doses of the same immunogens were tested and identical protocols were also compared for intranasal (i.n.) or intramuscular (i.m.) viral administration, before challenge with the highly pathogenic VACV VVIHD-J strain. Our results show that a single dose of any combined immunogen elicited a very low antibody response. Protein mixtures administered twice boosted the humoral response of DNA immunizations by electroporation (e. p.), but did not protect from viral challenge. The antibody neutralizing titer was inversely correlated with animals' weight loss, which was initially similar in all of the groups after the challenge, but was then reversed in mice that had been primed twice with the DNA recombinants and boosted twice with the FWPV recombinants.

Single-chain A35R-M1R-B6R trivalent mRNA vaccines protect mice against both mpox virus and vaccinia virus

BACKGROUND

Mpox has spread to many countries around the world. While the existing live attenuated mpox vaccines are effective, advances in 21st century technologies now enable the development of vaccines with more specific antigens, clearer mechanisms, and more controllable side effects.

METHODS

We systematically evaluated the immunogenicity and protective efficacy of the A35R, M1R and B6R antigens of the mpox virus (MPXV). With these findings, we designed three single-chain trivalent mRNA vaccines (AMAB-wt, AMAB-C140S and AMB-C140S) by integrating the soluble regions of these antigens into single mRNA-encoded polypeptides based on their protein structures. Then, the immunogenicity and protective efficacy of these single-chain mRNA vaccines were evaluated in mice models against both VACV and MPXV.

FINDINGS

The three single-chain vaccines elicited neutralising antibodies that effectively neutralised both VACV and MPXV. The single-chain vaccines or cocktail vaccine containing mRNAs encoding soluble antigen (sA35R + sM1R + sB6R) exhibited 100% or 80% protection against a lethal dose of VACV challenge, while the cocktail of full-length antigens (A35 + M1 + B6) and the live attenuated vaccine, VACV Tian Tan (VACV-VTT), completely failed to protect mice. Moreover, the single-chain vaccines significantly reduced viral load in the lungs and ovaries of MPXV-challenged mice.

INTERPRETATION

Compared with the cocktail vaccines, our single-chain designs demonstrated similar or superior immunogenicity and protective efficacy. Importantly, the simplicity of the single-chain vaccines enhances both the controllability and accessibility of mpox vaccines. We believe these single-chain vaccines qualify as the next-generation mpox vaccines.

FUNDING

National Natural Science Foundation of China and Youth Innovation Promotion Association of the CAS.

mRNA vaccines for infectious diseases - advances, challenges and opportunities

The concept of mRNA-based vaccines emerged more than three decades ago. Groundbreaking discoveries and technological advancements over the past 20 years have resolved the major roadblocks that initially delayed application of this new vaccine modality. The rapid development of nucleoside-modified COVID-19 mRNA vaccines demonstrated that this immunization platform is easy to develop, has an acceptable safety profile and can be produced at a large scale. The flexibility and ease of antigen design have enabled mRNA vaccines to enter development for a wide range of viruses as well as for various bacteria and parasites. However, gaps in our knowledge limit the development of next-generation mRNA vaccines with increased potency and safety. A deeper understanding of the mechanisms of action of mRNA vaccines, application of novel technologies enabling rational antigen design, and innovative vaccine delivery strategies and vaccination regimens will likely yield potent novel vaccines against a wide range of pathogens.

Advancements in monkeypox vaccines development: a critical review of emerging technologies

Monkeypox (mpox) is a zoonotic illness caused by the monkeypox virus (MPXV), with higher health concerns among people who are pregnant, children, and persons who are immunocompromised, including people with untreated and advanced HIV disease. Significant progress has been made in developing vaccines against mpox, yet critical challenges and limitations persist in ensuring their effectiveness, safety, and accessibility. The pertinence of this review is highlighted by the World Health Organization's declaration of a global health emergency on August 14, 2024, due to the recent mpox outbreak, underscoring the critical necessity for effective vaccine solutions in the face of a rapidly evolving virus. Here, we comprehensively analyze various vaccine platforms utilized in mpox prevention, including attenuated and non-replicating virus vaccines, viral vector-based vaccines, recombinant protein vaccines, and DNA and mRNA vaccines. We evaluate the advantages and limitations of each platform, highlighting the urgent need for ongoing research and innovation to enhance vaccine efficacy and safety. Recent advancements, such as incorporating immunostimulatory sequences, improved delivery systems, and developing polyvalent vaccines, are explored for their potential to offer broader protection against diverse orthopoxvirus strains. This work underscores the need to optimize currently available vaccines and investigate novel vaccination strategies to address future public health emergencies effectively. By focusing on these advanced methodologies, we aim to contribute to the development of robust and adaptable vaccine solutions for mpox and other related viral threats.

Comparison of protection against mpox following mRNA or modified vaccinia Ankara vaccination in nonhuman primates

In 2022, mpox virus (MPXV) spread worldwide, causing 99,581 mpox cases in 121 countries. Modified vaccinia Ankara (MVA) vaccine use reduced disease in at-risk populations but failed to deliver complete protection. Lag in manufacturing and distribution of MVA resulted in additional MPXV spread, with 12,000 reported cases in 2023 and an additional outbreak in Central Africa of clade I virus. These outbreaks highlight the threat of zoonotic spillover by Orthopoxviruses. mRNA-1769, an mRNA-lipid nanoparticle (LNP) vaccine expressing MPXV surface proteins, was tested in a lethal MPXV primate model. Similar to MVA, mRNA-1769 conferred protection against challenge and further mitigated symptoms and disease duration. Antibody profiling revealed a collaborative role between neutralizing and Fc-functional extracellular virion (EV)-specific antibodies in viral restriction and ospinophagocytic and cytotoxic antibody functions in protection against lesions. mRNA-1769 enhanced viral control and disease attenuation compared with MVA, highlighting the potential for mRNA vaccines to mitigate future pandemic threats.

The monkeypox virus-host interplays

Monkeypox virus (MPXV) is a DNA virus belonging to the Orthopoxvirus genus within the Poxviridae family which can cause a zoonotic infection. The unexpected non-endemic outbreak of mpox in 2022 is considered as a new global threat. It is imperative to take proactive measures, including enhancing our understanding of MPXV's biology and pathogenesis, and developing novel antiviral strategies. The host immune responses play critical roles in defensing against MPXV infection while the virus has also evolved multiple strategies for immune escape. This review summarizes the biological features, antiviral immunity, immune evasion mechanisms, pathogenicity, and prevention strategies for MPXV.

Analysis of binding and authentic virus-neutralizing activities of immune sera induced by various monkeypox virus antigens

Monkeypox cases continue to increase globally, and there is an urgent need to develop a highly effective vaccine against monkeypox. This study investigated the binding and authentic-virus neutralizing activities of sera from mice immunized with EEV (extracellularly enveloped viruses) antigens B6R and A35R, and IMV (intrinsic material viruses) antigens M1R, A29L, E8L, and H3L against monkeypox virus. The results showed that immunizations of A35R and E8L could only induce lower titers of binding antibodies, in contrast, immunization of M1R induced the highest titers of binding antibodies, while immunization of B6R, H3L, and A29L induced moderate titers of binding antibodies. For the live monkeypox virus neutralization assay, the results showed that immunization with two doses of EEV antigen B6R did not effectively induce humoral immune responses to neutralize monkeypox live virus, immunization with EEV-A35R only induced weak monkeypox-neutralizing antibodies. In contrast, the immunization of the four types of monkeypox virus IMV antigens can all induce neutralizing antibodies against authentic monkeypox virus, among them, A29L and H3L induced the highest neutralizing antibody titers. The results of this study provide important references for the selection of antigens in the development of the next generation of monkeypox vaccines.

Mpox mRNA-1769 Vaccine Inhibits Orthopoxvirus Replication at Intranasal, Intrarectal, and Cutaneous Sites of Inoculation

The increasing incidence of mpox in Africa and the recent global outbreak with evidence of sexual transmission have stimulated interest in new vaccines and therapeutics. Our previous study demonstrated that mice immunized twice with a quadrivalent lipid nanoparticle vaccine comprising four monkeypox virus mRNAs raised neutralizing antibodies and antigen-specific T cells and were protected against a lethal intranasal challenge with vaccinia virus. Here we extended these findings by using live animal imaging to demonstrate that the mRNA vaccine greatly reduced virus replication and spread from an intranasal site of inoculation and prevented detectable replication at intrarectal and cutaneous inoculation sites. Moreover, considerable protection was achieved with a single vaccination and a booster vaccination enhanced protection for at least 4 months. Protection was related to the amount of mRNA inoculated, which correlated with neutralizing antibody levels. The role of antibody in protection was demonstrated by passive transfer of immune serum pre- or post-challenge to immunocompetent and immunodeficient mice lacking mature B and T cells and therefore unable to mount an adaptive response. These findings provide insights into the mechanism and extent of mRNA vaccine induced protection of orthopoxviruses and support clinical testing.

Immunogenicity of a 30-valent M protein mRNA group A Streptococcus vaccine

BACKGROUND

Group A Streptococcus (Strep A) causes both uncomplicated and severe invasive infections, as well as the post-infection complications acute rheumatic fever and rheumatic heart disease. Despite the high global burden of disease resulting from Strep A infections, there is not a licensed vaccine. A 30-valent M protein-based vaccine has previously been shown to be immunogenic in animal models and in a Phase I clinical trial (NCT02564237). Here, we assessed the immunogenicity of a 30-valent messenger (m)RNA vaccine designed to express the same M peptide targets as the 30-valent protein vaccine and compared it with the protein vaccine.

METHODS

Female New Zealand white rabbits were immunized with one of four vaccine formulations (3 doses of each formulation at days 1, 28, and 56): soluble mRNA (100 μg/animal), C-terminal transmembrane mRNA (100 μg/animal), protein vaccine (400 μg/animal), or a non-translatable RNA control (100 μg/animal). Serum was collected one day prior to the first dose and on days 42 and 70. Rabbit serum samples were assayed for antibody levels against synthetic M peptides by ELISA. HL-60 opsonophagocytic killing (OPK) assays were performed to assess functional antibody levels.

RESULTS

Serum IgG levels were similar for the mRNA and protein vaccines. The CtTM version of the mRNA vaccine elicited slightly higher antibody levels than the mRNA designed to express soluble proteins. OPK activity was similar for the mRNA and protein vaccines, regardless of M type.

CONCLUSIONS

The total antibody responses and functional antibody levels elicited by the 30-valent mRNA Strep A vaccines were similar to those observed following immunization with the analogous protein vaccine. The mRNA vaccine platform provides potential advantages to protein-based vaccines including inherent adjuvant activity, increased production efficiency, lower cost, and the potential to rapidly change epitopes/peptides, all of which are important considerations related to multivalent Strep A vaccine development.

Rapid Decline of Mpox Antibody Responses Following MVA-BN Vaccination

The replication-incompetent modified vaccinia Ankara-Bavarian Nordic vaccine (MVA-BN; Jynneos) was deployed during the 2022 clade IIb mpox outbreak. On August 14, 2024, the World Health Organization declared the mpox clade Ib outbreak in the Democratic Republic of the Congo a public health emergency of international concern, which has raised the question about the durability of vaccine immunity after MVA-BN vaccination. In this study, we show that the MVA-BN vaccine generated mpox serum antibody responses that largely waned after 6-12 months.

A Pseudovirus Nanoparticle Displaying the Vaccinia Virus L1 Protein Elicited High Neutralizing Antibody Titers and Provided Complete Protection to Mice against Mortality Caused by a Vaccinia Virus Challenge

The recent worldwide incidence of mpox infection and concerns about future emerging variants of mpox viruses highlight the need for the development of a new generation of mpox vaccines. To achieve this goal, we utilized our norovirus S nanoparticle vaccine platform to produce and evaluate two pseudovirus nanoparticles (PVNPs), S-L1 and S-J1. These PVNPs displayed the L1 neutralizing antigen target of the vaccinia virus and a yet-untested J1 antigen of the mpox virus, respectively, with the aim of creating an effective nanoparticle-based mpox vaccine. Each self-assembled PVNP consists of an inner shell resembling the interior layer of the norovirus capsid and multiple L1 or J1 antigens on the surface. The PVNPs improved the antibody responses toward the displayed L1 or J1 antigens in mice, resulting in significantly greater L1/J1-specific IgG and IgA titers than those elicited by the corresponding free L1 or J1 antigens. After immunization with the S-L1 PVNPs, the mouse sera exhibited high neutralizing antibody titers against the vaccinia virus, and the S-L1 PVNPs provided mice with 100% protection against mortality caused by vaccinia virus challenge. In contrast, the S-J1 PVNPs induced low neutralizing antibody titers and conferred mice weak protective immunity. These data confirm that the L1 protein is an excellent vaccine target and that the readily available S-L1 PVNPs are a promising mpox vaccine candidate worthy of further development.

Polyvalent mpox mRNA vaccines elicit robust immune responses and confer potent protection against vaccinia virus

The 2022 mpox outbreak led the World Health Organization (WHO) to declare it a public health emergency of international concern (PHEIC). There is a need to develop more effective and safer mpox virus (MPXV)-specific vaccines in response to the mpox epidemic. The mRNA vaccine is a promising platform to protect against MPXV infection. In this study, we construct two bivalent MPXV mRNA vaccines, designated LBA (B6R-A29L) and LAM (A35R-M1R), and a quadrivalent mRNA vaccine, LBAAM (B6R-A35R-A29L-M1R). The immunogenicity and protective efficacy of these vaccines alone or in combination were evaluated in a lethal mouse model. All mRNA vaccine candidates could elicit potential antigen-specific humoral and cellular immune responses and provide protection against vaccinia virus (VACV) infection. The protective effect of the combination of two bivalent mRNA vaccines and the quadrivalent vaccine was superior to that of the individual bivalent mRNA vaccine. Our study provides valuable insights for the development of more efficient and safer mRNA vaccines against mpox.

Understanding the biology of monkeypox virus to prevent future outbreaks

Historically, monkeypox (mpox) was a zoonotic disease endemic in Africa. However, in 2022, a global outbreak occurred following a substantial increase in cases in Africa, coupled with spread by international travellers to other continents. Between January 2022 and October 2023, about 91,000 confirmed cases from 115 countries were reported, leading the World Health Organization to declare a public health emergency. The basic biology of monkeypox virus (MPXV) can be inferred from other poxviruses, such as vaccinia virus, and confirmed by genome sequencing. Here the biology of MPXV is reviewed, together with a discussion of adaptive changes during MPXV evolution and implications for transmission. Studying MPXV biology is important to inform specific host interactions, to aid in ongoing outbreaks and to predict those in the future.

Longitudinal viral shedding and antibody response characteristics of men with acute infection of monkeypox virus: a prospective cohort study

Understanding of infection dynamics is important for public health measures against monkeypox virus (MPXV) infection. Herein, samples from multiple body sites and environmental fomites of 77 acute MPXV infections (HIV co-infection: N = 42) were collected every two to three days and used for detection of MPXV DNA, surface protein specific antibodies and neutralizing titers. Skin lesions show 100% positivity rate of MPXV DNA, followed by rectum (88.16%), saliva (83.78%) and oropharynx (78.95%). Positivity rate of oropharynx decreases rapidly after 7 days post symptom onset (d.p.o), while the rectum and saliva maintain a positivity rate similar to skin lesions. Viral dynamics are similar among skin lesions, saliva and oropharynx, with a peak at about 6 d.p.o. In contrast, viral levels in the rectum peak at the beginning of symptom onset and decrease rapidly thereafter. 52.66% of environmental fomite swabs are positive for MPXV DNA, with highest positivity rate (69.89%) from air-conditioning air outlets. High seropositivity against A29L (100%) and H3L (94.74%) are detected, while a correlation between IgG endpoint titers and neutralizing titers is only found for A29L. Most indexes are similar between HIV and Non-HIV participants, while HIV and rectitis are associated with higher viral loads in rectum.

Rapid development of double-hit mRNA antibody cocktail against orthopoxviruses

The Orthopoxvirus genus, especially variola virus (VARV), monkeypox virus (MPXV), remains a significant public health threat worldwide. The development of therapeutic antibodies against orthopoxviruses is largely hampered by the high cost of antibody engineering and manufacturing processes. mRNA-encoded antibodies have emerged as a powerful and universal platform for rapid antibody production. Herein, by using the established lipid nanoparticle (LNP)-encapsulated mRNA platform, we constructed four mRNA combinations that encode monoclonal antibodies with broad neutralization activities against orthopoxviruses. In vivo characterization demonstrated that a single intravenous injection of each LNP-encapsulated mRNA antibody in mice resulted in the rapid production of neutralizing antibodies. More importantly, mRNA antibody treatments showed significant protection from weight loss and mortality in the vaccinia virus (VACV) lethal challenge mouse model, and a unique mRNA antibody cocktail, Mix2a, exhibited superior in vivo protection by targeting both intracellular mature virus (IMV)-form and extracellular enveloped virus (EEV)-form viruses. In summary, our results demonstrate the proof-of-concept production of orthopoxvirus antibodies via the LNP-mRNA platform, highlighting the great potential of tailored mRNA antibody combinations as a universal strategy to combat orthopoxvirus as well as other emerging viruses.

Rapid and highly potent humoral responses to mpox nanovaccine candidates adjuvanted by thermostable scaffolds

Monkeypox (mpox) is a zoonotic disease caused by monkeypox virus (MPXV) of the orthopoxvirus genus. The emergence and global spread of mpox in 2022 was declared as a public health emergency by World Health Organization. This mpox pandemic alarmed us that mpox still threaten global public health. Live vaccines could be used for immunization for this disease with side effects. New alternative vaccines are urgently needed for this re-emerging disease. Specific antibody responses play key roles for protection against MPXV, therefore, vaccines that induce high humoral immunity will be ideal candidates. In the present study, we developed thermostable nanovaccine candidates for mpox by conjugating MPXV antigens with thermostable nanoscafolds. Three MPXV protective antigens, L1, A29, and A33, and the thermostable Aquafex aeolicus lumazine synthase (AaLS), were expressed in E. coli and purified by Ni-NTA methods. The nanovaccines were generated by conjugation of the antigens with AaLS. Thermal stability test results showed that the nanovaccines remained unchanged after one week storage under 37℃ and only partial degradation under 60℃, indicating high thermostability. Very interesting, one dose immunization with the nanovaccine could induce high potent antibody responses, and two dose induced 2-month high titers of antibodes. In vitro virus neutralization test showed that nanovaccine candidates induced significantly higher levels of neutralization antibodies than monomers. These results indicated that the AaLS conjugation nanovaccines of MPXV antigens are highly thermostable in terms of storage and antigenic, being good alternative vaccine candidates for this re-emerging disease.

A multivalent mRNA monkeypox virus vaccine (BNT166) protects mice and macaques from orthopoxvirus disease

In response to the 2022 outbreak of mpox driven by unprecedented human-to-human monkeypox virus (MPXV) transmission, we designed BNT166, aiming to create a highly immunogenic, safe, accessible, and scalable next-generation vaccine against MPXV and related orthopoxviruses. To address the multiple viral forms and increase the breadth of immune response, two candidate multivalent mRNA vaccines were evaluated pre-clinically: a quadrivalent vaccine (BNT166a; encoding the MPXV antigens A35, B6, M1, H3) and a trivalent vaccine (BNT166c; without H3). Both candidates induced robust T cell responses and IgG antibodies in mice, including neutralizing antibodies to both MPXV and vaccinia virus. In challenge studies, BNT166a and BNT166c provided complete protection from vaccinia, clade I, and clade IIb MPXV. Furthermore, immunization with BNT166a was 100% effective at preventing death and at suppressing lesions in a lethal clade I MPXV challenge in cynomolgus macaques. These findings support the clinical evaluation of BNT166, now underway (NCT05988203).

An overview on mRNA-based vaccines to prevent monkeypox infection

The human monkeypox virus (Mpox) is classified as a member of the Poxviridae family and belongs to the Orthopoxvirus genus. Mpox possesses double-stranded DNA, and there are two known genetic clades: those originating in West Africa and the Congo Basin, commonly known as Central African clades. Mpox may be treated with either the vaccinia vaccination or the therapeutics. Modifying the smallpox vaccine for treating and preventing Mpox has shown to be beneficial because of the strong link between smallpox and Mpox viruses and their categorization in the same family. Cross-protection against Mpox is effective with two Food and Drug Administration (FDA)-approved smallpox vaccines (ACAM2000 and JYNNEOSTM). However, ACAM2000 has the potential for significant adverse effects, such as cardiac issues, whereas JYNNEOS has a lower risk profile. Moreover, Mpox has managed to resurface, although with modified characteristics, due to the discontinuation and cessation of the smallpox vaccine for 40 years. The safety and efficacy of the two leading mRNA vaccines against SARS-CoV-2 and its many variants have been shown in clinical trials and subsequent data analysis. This first mRNA treatment model involves injecting patients with messenger RNA to produce target proteins and elicit an immunological response. High potency, the possibility of safe administration, low-cost manufacture, and quick development is just a few of the benefits of RNA-based vaccines that pave the way for a viable alternative to conventional vaccines. When protecting against Mpox infection, mRNA vaccines are pretty efficient and may one day replace the present whole-virus vaccines. Therefore, the purpose of this article is to provide a synopsis of the ongoing research, development, and testing of an mRNA vaccine against Mpox.

Rational design of a 'two-in-one' immunogen DAM drives potent immune response against mpox virus

The global outbreak of the mpox virus (MPXV) in 2022 highlights the urgent need for safer and more accessible new-generation vaccines. Here, we used a structure-guided multi-antigen fusion strategy to design a 'two-in-one' immunogen based on the single-chain dimeric MPXV extracellular enveloped virus antigen A35 bivalently fused with the intracellular mature virus antigen M1, called DAM. DAM preserved the natural epitope configuration of both components and showed stronger A35-specific and M1-specific antibody responses and in vivo protective efficacy against vaccinia virus (VACV) compared to co-immunization strategies. The MPXV-specific neutralizing antibodies elicited by DAM were 28 times higher than those induced by live VACV vaccine. Aluminum-adjuvanted DAM vaccines protected mice from a lethal VACV challenge with a safety profile, and pilot-scale production confirmed the high yield and purity of DAM. Thus, our study provides innovative insights and an immunogen candidate for the development of alternative vaccines against MPXV and other orthopoxviruses.

Neutralization Determinants on Poxviruses

Smallpox was a highly contagious disease caused by the variola virus. The disease affected millions of people over thousands of years and variola virus ranked as one of the deadliest viruses in human history. The complete eradication of smallpox in 1980, a major triumph in medicine, was achieved through a global vaccination campaign using a less virulent poxvirus, vaccinia virus. Despite this success, the herd immunity established by this campaign has significantly waned, and concerns are rising about the potential reintroduction of variola virus as a biological weapon or the emergence of zoonotic poxviruses. These fears were further fueled in 2022 by a global outbreak of monkeypox virus (mpox), which spread to over 100 countries, thereby boosting interest in developing new vaccines using molecular approaches. However, poxviruses are complex and creating modern vaccines against them is challenging. This review focuses on the structural biology of the six major neutralization determinants on poxviruses (D8, H3, A27, L1, B5, and A33), the localization of epitopes targeted by neutralizing antibodies, and their application in the development of subunit vaccines.