Expanding Poxviruses Resources at the NCPV
Poxviruses remain among the most biologically distinctive and historically significant viral pathogens, continuing to attract interest across virology, immunology, and public health. As large double-stranded DNA viruses that replicate entirely within the cytoplasm [1], members of the Poxviridae family provide unique insights into virus–host interactions, immune evasion strategies, and vaccine development. At the National Collection of Pathogenic Viruses (NCPV), we are committed to supporting this research landscape by maintaining a robust and expanding catalogue of poxvirus materials, including emerging and re-emerging pathogens such as mpox virus (MPXV).
Orthopoxviruses produce multiple infectious virion forms with distinct membrane compositions, which underpins differences in entry pathways and spread. Primarily, the intracellular mature virus (IMV) and enveloped derivatives that arise during egress, including intracellular enveloped virus (IEV), cell‑associated enveloped virus (CEV), and extracellular enveloped virus (EEV). IEV is formed when IMV acquires additional intracellular membranes and is transported to the cell periphery, where it becomes CEV at the plasma membrane and drives direct cell‑to‑cell spread (through actin-based motility), before release as EEV for dissemination through extracellular spaces, such as in blood. This virus diversity expands virus–host interactions by enabling multiple entry mechanisms, enhances immune evasion, particularly via the additional envelope of EEV containing a different set of proteins and masking the IMV antigens. This has key implications for vaccine design, as effective immunity must target antigens from both IMV and enveloped virions to block infection and dissemination [2].
Figure 1 - Schematic representation of the replication cycle of orthopoxviruses. Above, a schematic of an enveloped particle (EV). The outer membrane is represented by a red line and the inner by a black line. The surface proteins of each membrane are indicated alongside. Below, the main steps of viral replication are indicated. The main neutralization determinants identified so far are highlighted in red, alongside the specific viral step they are involved in. Key abbreviations include MV for mature virion, IV for immature virion, IMV for intracellular mature virion, WV for wrapped virion (IEV), CEV for cell-associated virion, EEV for extracellular enveloped virion, and TGN for trans Golgi network [2]. Description of the proteins present in each virion structure, entry-fusion complex (EFC), attachment, morphogenesis and virulence, and EEV envelope proteins.
Within the Poxviridae family, the genus Orthopoxvirus includes high-profile viruses such as variola virus, the causative agent of smallpox, which is believed to have caused more deaths throughout history than any other viral disease [3, 4]. The process of smallpox eradication started with the process of variolation, which is the deliberate infection of healthy individuals with an inoculum of the disease. This technique started in Asia and was popularised in Europe in the XVIII century [5]. In 1796, Edward Jenner used material from a cowpox lesion on a milkmaid’s hand to inoculate a young boy, demonstrating protection against smallpox and laying the foundation for immunology through the development of the first vaccine [6].
The vaccinia virus-based vaccine, a genetically distinct virus that is serologically different from cowpox and other poxviruses ultimately led to the global eradication of smallpox in 1980 [7]. Today, a milder version of vaccinia virus-based vaccines continues to be the foundation of the vaccines against smallpox and MPXV, including MVA-BN (modified vaccinia Ankara – Bavarian Nordic) [8, 9]. The MPXV clade IIb outbreak of 2022 exposed the continuous threat of poxviruses to human health and how zoonotic spillover events and sustained human transmission drive the spread and increase the probability of re-emergency and emerging in non-endemic areas leading to outbreaks of these diseases [10].
Although, herd immunity driven by the eradication of smallpox continues to be a pilar of public health, these outbreak events in conjugation with waned immunity by using a less immunogenic viral vector in vaccinations against MPXV, is driving the interest in developing protein subunit vaccines [11, 12]. This is a complex process due to the large number of antigens present in the different virions. MPXV, is a large dsDNA virus with over 30 membrane proteins alone. Many studies including the use of in silico methods are now deployed to understand which of these proteins are the best targets for the next generation vaccines and produce reliable immunogenicity [13-15]. As well as for producing the best diagnostic tools [16] and therapeutics [17].
In response to increasing demand and evolving scientific priorities, NCPV is actively expanding its MPXV portfolio, with particular emphasis on representing genetic diversity across clades. NCPV also offers inactivated mpox virus (clade IIb), produced via x-ray irradiation. Irradiated viruses are non-viable and can therefore be handled and transported at lower containment levels while remaining antigenically and genomically integrity [18, 19]. NCPV remains committed to evolving its collection in line with scientific need. Recently, we released an inter-clade recombinant MPXV (Ib/IIb) [4], and we will soon make available additional strains, including clade Ib.
We encourage users to explore the full catalogue for detailed strain information. Table 1 provides an overview of the orthopoxviruses currently available through the NCPV.
| Virus | Virus strain | Catalogue number | TEM images |
|---|---|---|---|
|
Cowpox virus |
Brighton red |
|
|
|
Vaccinia virus |
Vaccine strain |
|
|
|
Camelpox virus |
|
|
|
|
Buffalopox virus |
H170/05 |
|
|
|
MPXV |
Clade IIb (May 2022, UK) |
|
|
|
MPXV |
Clade IIb (May 2022, UK) x-ray irradiated |
|
|
|
MPXV |
Recombinant Ib/IIb |
|
|
|
MPXV |
Clade Ib |
|
References
1. Moss, B., Poxvirus DNA replication. Cold Spring Harb Perspect Biol, 2013. 5(9).
2. Riccardo, V. and G.C. Pablo, Neutralization Determinants on Poxviruses. Viruses, 2023. 15(12).
3. Behbehani, A.M., The smallpox story: life and death of an old disease. Microbiol Rev, 1983. 47(4): p. 455–509.
4. Berche, P., Life and death of smallpox. Presse Med, 2022. 51(3): p. 104117.
5. Boylston, A., The origins of inoculation. J R Soc Med, 2012. 105(7): p. 309–13.
6. WHO. History of the smallpox vaccine. Available from: https://www.who.int/news-room/spotlight/history-of-vaccination/history-of-smallpox-vaccination.
7. Henderson, D.A., The eradication of smallpox--an overview of the past, present, and future. Vaccine, 2011. 29 Suppl 4: p. D7–9.
8. Navarro, C., et al., Effectiveness of modified vaccinia Ankara-Bavarian Nordic vaccine against mpox infection: emulation of a target trial. BMJ, 2024. 386: p. e078243.
9. Meyer, H. Summary report on first, second and third generation smallpox
vaccines. 2013; Available from: https://terrance.who.int/mediacentre/data/sage/SAGE_Docs_Ppt_Nov2013/8_session_smallpox/Nov2013_session8_smallpox_vaccine.pdf.
10. Parker, E., et al., Genomics reveals zoonotic and sustained human mpox spread in West Africa. Nature, 2025. 643(8074): p. 1343–1351.
11. Byrne, J., et al., Immune Response to MVA-BN Vaccination for Mpox: Current Evidence and Future Directions. Vaccines (Basel), 2025. 13(9).
12. Collier, A.Y., et al., Rapid Decline of Mpox Antibody Responses Following MVA-BN Vaccination. medRxiv, 2024.
13. Akhtar, N., et al., Immunoinformatics-Aided Design of a Peptide Based Multiepitope Vaccine Targeting Glycoproteins and Membrane Proteins against Monkeypox Virus. Viruses, 2022. 14(11).
14. Gupta, K., Correction: In silico structural and functional characterization of hypothetical proteins from Monkeypox virus. J Genet Eng Biotechnol, 2023. 21(1): p. 54.
15. Wang, Y., K. Yang, and H. Zhou, Immunogenic proteins and potential delivery platforms for mpox virus vaccine development: A rapid review. Int J Biol Macromol, 2023. 245: p. 125515.
16. Sagdat, K., A. Batyrkhan, and D. Kanayeva, Exploring monkeypox virus proteins and rapid detection techniques. Front Cell Infect Microbiol, 2024. 14: p. 1414224.
17. Yefet, R., et al., Potent neutralization by antibodies targeting the MPXV A28 protein. Nat Commun, 2025. 16(1): p. 11455.
18. Campbell, E., Afrough, B., Bonney, L., Curran-French, M., Chamberlain, J., Daddiego, J., Fotheringham, V., Stanley, M., Drinkwater, E., Ferreira, P., Tolley, H., Dugg, S., Burton, J., Eastbrook, L., and Hewson, R. , X-ray Inactivation of SARS-CoV-2: A Safe, Cost-effective Approach for Pandemic Testing Workflows. Research Square, 2024.
19. Afrough, B., et al., X-ray inactivation of RNA viruses without loss of biological characteristics. Sci Rep, 2020. 10(1): p. 21431.
Written by Teresa Ramalho