Duration of humoral immunity from smallpox vaccination and its cross-reaction with Mpox virus

Global perspectives on smallpox vaccine against monkeypox: a comprehensive meta-analysis and systematic review of effectiveness, protection, safety and cross-immunogenicity

A large outbreak of monkeypox occurred in 2022, and most people lack immunity to orthopoxvirus. Smallpox vaccination is essential for preventing further smallpox outbreaks. This study evaluated the effectiveness, protection, safety, and cross-immunogenicity of smallpox vaccine in preventing monkeypox infection. PubMed, Embase, Scopus, and Web of Science were searched from database inception to 10 March 2024. We included studies involving "monkeypox virus" and "vaccinations", and excluded reviews, animal studies, and articles with missing or duplicate data. A total of 37 studies with 57,693 participants were included in the final analysis. The effectiveness data showed that monkeypox infection rates were lower in the smallpox-vaccinated group than in the unvaccinated group (risk ratio [RR]: 0.46; 95% confidence interval [CI]: 0.31-0.68). The protection data showed that smallpox vaccination effectively reduced the risk of severe monkeypox infection (RR: 0.61; 95% CI: 0.42-0.87). Third-generation vaccines showed greater efficacy (RR: 0.36, 95% CI: 0.22-0.56) than first-generation vaccines. The number of doses of smallpox vaccine has no significant effect on monkeypox. Safety data showed that adverse reactions after smallpox vaccination were mainly mild and included local erythema, swelling, induration, itching, and pain. Meanwhile, we found that smallpox vaccination could induce the production of neutralizing antibodies against monkeypox. Our findings offer compelling evidence supporting the clinical application of the smallpox vaccine for preventing monkeypox and advocate that high-risk groups should be prioritized for receiving one dose of the smallpox vaccine if the vaccine stockpile is low.

An mpox quadrivalent mRNA vaccine protects mice from lethal vaccinia virus challenge

The outbreak of 2022 monkeypox virus (MPXV) infection in nonendemic regions is a global public health concern. A highly effective and safe MPXV vaccine that is available to the general public is urgently needed to control the mpox pandemic. Here, we developed a multivalent mRNA vaccine candidate, MPXV-1103, which expresses the full-length B6, A35, A29 and M1 proteins with three flexible linkers (G4S1)3 in a single sequence. Compared with the monovalent MPXV mRNA vaccine candidates or the quadrivalent mRNA vaccine from mixtures of the four monovalent MPXV mRNA vaccines, MPXV-1103 elicits a robust humoral response and an MPXV-specific T-cell response and protects mice from lethal vaccinia virus (VACV) challenge, with no live virus detected in the nasal or lungs even at dosages as low as 1 μg. Furthermore, analysis of complete blood counts and photomicrographs of tissue from the main organs of mice vaccinated with MPXV-1103 at doses of 5 μg and 20 μg revealed that two doses of MPXV-1103 did not cause any observable pathological changes in the mice. Collectively, our results suggest that MPXV-1103, with features of high efficacy, safety and a simplified manufacturing process, is a promising vaccine candidate for defending against MPXV infection.

Clinical features and viral load variations of Mpox: a retrospective study in Chongqing, China

PURPOSE

Since May 2022, Mpox has spread extensively outside of Africa, posing a serious threat to the health of people globally, and particularly to the men who have sex with men (MSM) population. Chongqing, a province in Southwest China, has relatively large MSM and people living with HIV (PLWH) populations, presenting conditions conducive to the wide dissemination of Mpox. In this study, we investigated the clinical characteristics of Mpox patients among MSM and PLWH in Chongqing, aiming to inform the development of targeted prevention, control, and treatment strategies for Mpox.

METHOD

We evaluated the clinical characteristics, travel history, time of onset, distribution and number of skin lesions of Mpox patients admitted to the Chongqing Public Health Medical Center between September 2022 and October 2023. Meanwhile, a series of clinical samples were collected and the pathogen of interest was identified as Mpox virus using quantitative polymerase chain reaction (qPCR). The results were presented in the form of cycle thresholds (Ct), which help to approximate the quantification of viral load.

RESULTS

As of October 11, 2023, the Chongqing Public Health Medical Center reported a total of nine Mpox virus infections. All the patients identified were male and belonged to the MSM population, among whom seven (77.8%) were living with HIV, and maintained a preserved immune system while achieving viral suppression via effective ART. We observed no discernible clinical differences between MSM with Mpox with or without HIV, and no fatalities were recorded. Viral loads were observed to be higher in samples taken from the skin than those from the throat, nasopharynx, blood, or semen.

CONCLUSION

In this retrospective study, the clinical manifestations of MPXV infection appeared consistent among MSM patients, regardless of HIV status. Elevated MPXV viral loads in the skin and mucosal tissues, particularly at genital and anal sites, indicate that transmission is more likely to occur via direct physical contact as opposed to respiratory pathways or through exposure to bodily fluids.

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.

Circular RNA vaccines against monkeypox virus provide potent protection against vaccinia virus infection in mice

Since the outbreak of monkeypox (mpox) in 2022, widespread concern has been placed on imposing an urgent demand for specific vaccines that offer safer and more effective protection. Using an efficient and scalable circular RNA (circRNA) platform, we constructed four circRNA vaccines that could induce robust neutralizing antibodies as well as T cell responses by expressing different surface proteins of mpox virus (MPXV), resulting in potent protection against vaccinia virus (VACV) in mice. Strikingly, the combination of the four circular RNA vaccines demonstrated the best protection against VACV challenge among all the tested vaccines. Our study provides a favorable approach for developing MPXV-specific vaccines by using a circular mRNA platform and opens up novel avenues for future vaccine research.

Mpox: An Overview of Pathogenesis, Diagnosis, and Public Health Implications

Mpox, caused by viruses of the genus Orthopoxvirus, is an emerging threat to human and animal health. With increasing urbanization and more frequent interaction between humans and wild animals, the risk of Mpox transmission to humans has increased significantly. This review aims to examine in depth the epidemiology, pathogenesis, and diagnosis of Mpox, with a special focus on recent discoveries and advances in understanding the disease. Molecular mechanisms involved in viral replication will be examined, as well as risk factors associated with interspecific transmission and spread of the disease in human populations. Currently available diagnostic methods will also be discussed, with a critical analysis of their limitations and possible future directions for improving the accuracy and timeliness of diagnosis. Finally, this review will explore the public health implications associated with Mpox, emphasizing the importance of epidemiological surveillance, vaccination, and emergency preparedness to prevent and manage possible outbreaks. Understanding the epidemiology and control strategies for Mpox is critical to protecting the health of human and animal communities and mitigating the risk of interspecific transmission and spread of the disease.

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.

The Current State and Progress of Mpox Vaccine Research

On July 23, 2022, the World Health Organization (WHO) declared the monkeypox (mpox) outbreak a "Public Health Emergency of International Concern." Since 2022, outbreaks of mpox in many countries around the world have primarily resulted in fatalities among immunocompromised individuals, such as untreated HIV/AIDS patients. Since the eradication of smallpox was declared by the WHO in 1980, the global vaccination against smallpox has been gradually discontinued. China also stopped routine smallpox vaccination in 1981. The protective effect of the smallpox vaccine has decreased over time due to aging and declining immunity in those who were vaccinated. For individuals, timely vaccination against smallpox is an effective means of protection against mpox. However, due to safety concerns with the smallpox vaccine and the limitations of current mpox vaccines, there is no vaccine that is safe, effective, and has low side effects applied in clinical settings. This article provides a comprehensive review of the development of mpox virus (MPXV) vaccines, their application in special populations, and the current state of vaccine research, considering the etiology, transmission, and prevention of the MPXV. Vaccination, as an effective method of epidemic prevention, can provide long-term immune protection and effectively reduce the severity of infection. However, as there is no licensed specific MPXV vaccine available globally, the vaccines currently used for mpox prevention are mostly smallpox vaccines. These smallpox vaccines can offer some degree of protection against mpox by activating cross-protection in the body.

Immunogenicity and Tolerability of a SARS-CoV-2 TNX-1800, a Live Recombinant Poxvirus Vaccine Candidate, in Syrian Hamsters and New Zealand White Rabbits

TNX-1800 is a preclinical stage synthetic-derived live attenuated chimeric horsepox virus vaccine engineered to express the SARS-CoV-2 spike (S) gene. The objectives of this study were to assess the safety, tolerability, and immunogenicity of TNX-1800 administration in Syrian golden hamsters and New Zealand white rabbits. Animals were vaccinated at three doses via percutaneous inoculation. The data showed that the single percutaneous administration of three TNX-1800 vaccine dose levels was well tolerated in both hamsters and rabbits. At all dose levels, rabbits were more decerning regarding vaccine site reaction than hamsters. Lastly, no TNX-1800 genomes could be detected at the site of vaccination. Post-vaccination, all animals had anti-SARS-CoV-2 spike protein IgG specific antibody responses. These data demonstrate that TNX-1800 infection was limited, asymptomatic, and cleared by the end of this study, and a single dose was able to generate immune responses.