Written by Khalil AL-SALEM M.D FRCS, FICO
Introduction on Monkeypox
Monkeypox is a viral disease causing an infectious rash similar to smallpox but generally less severe. Discovered in monkeys in the late 1950s, the virus can infect both animals and humans. It spreads through close contact with an infected person, animal, or contaminated materials. Symptoms include fever, headache, muscle aches, and a distinctive rash that evolves into fluid-filled blisters. Recent outbreaks outside of Africa have raised global concern, prompting efforts to control its spread. Smallpox vaccines have been found effective against monkeypox. In this article will talk about Monkeypox vaccine
Immunity in Farmers and Cattle Workers
Individuals who contract ORF ( a disease cauing infectious rash), is a zoonotic disease caused by the parapoxvirus (commonly infecting sheep and goats), develop immunity to this specific virus. However, this does not confer direct immunity to smallpox or monkeypox, which are caused by orthopoxviruses. While ORF does not provide direct protection against monkeypox, a strong immune response might enhance overall resilience.
Monkeypox Vaccines
JYNNEOS (Imvamune or Imvanex)
A third-generation, live, non-replicating vaccine approved for both smallpox and monkeypox. Given as two subcutaneous injections, 28 days apart. It is effective and safer for immunocompromised individuals.
ACAM2000
A second-generation live, replicating vaccine used for smallpox and monkeypox in specific cases. Administered via scarification, it provides strong protection but has more side effects and is not recommended for those with certain health conditions.
Who Should Get Monkeypox vaccine?
Vaccination is recommended for high-risk individuals, including healthcare workers and those exposed to the virus. In outbreaks, post-exposure prophylaxis may be offered to prevent or lessen disease severity.
Side Effects
JYNNEOS: Mild side effects like pain at the injection site, redness, and mild fever; serious side effects are rare.
ACAM2000: Higher risk of side effects, including potential spread of the vaccinia virus, especially in immunocompromised individuals.
Effectiveness and Duration
The vaccines provide robust, long-lasting protection, often for decades. Booster doses may be necessary in high-risk situations.
Global Availability and Public Health Strategies
Vaccines like JYNNEOS are distributed globally, especially in outbreak regions. Strategies such as ring vaccination target close contacts of confirmed cases to prevent further spread.
Monkeypox Virus (MPXV) Virology
MPXV belongs to the Orthopoxvirus genus in the Poxviridae family, which includes the variola (smallpox) virus. Its large, double-stranded DNA genome (~197 kb) encodes about 190 proteins, some involved in immune evasion and transmission.
Strains and Transmission
There are two clades: the Central African (more severe) and West African (milder). Transmission can occur from animals to humans or between humans via direct contact with lesions, bodily fluids, or contaminated materials.
Pathogenesis and Immune Response
After entering the body, the virus replicates at the entry site, spreads to lymph nodes, and causes viremia. It evades the immune system through various mechanisms, leading to symptoms like fever, rash, and pustules. The immune response includes both innate and adaptive mechanisms, crucial for recovery and long-term immunity.
Replication and Immune Evasion
MPXV replicates entirely in the cytoplasm, avoiding many host defenses. Early proteins inhibit apoptosis and interferon signaling, helping the virus replicate and spread.
Implications for Treatment and Vaccines
Understanding the virus’s replication and immune evasion strategies is key to developing effective vaccines and antiviral therapies. Targeting viral DNA replication or viral factories could offer therapeutic avenues.
Conclusion
The monkeypox virus’s unique replication process and genetic stability make it a fascinating subject for virological study, with significant implications for public health.