Immunopathogenesis of Orthopoxviridae: Insights into Immunology from Smallpox to Monkeypox (Mpox)

Abstract

Since 2019, notable global viral outbreaks have occurred necessitating further research and healthcare system investigations. Following the COVID—19 pandemic, an unexpected duality has occurred of SARS–CoV–2 and monkeypox virus (MPXV) infections. Monkeypox virus is of the Orthopoxviridae genus, belonging to the family Poxviridae. Zoonotic transmission (animal to human transmission) may occur. The Orthopoxviridae genus includes other Orthopoxviruses (OPXV) present in animal host reservoirs that include cowpox viruses (CPXV), vaccinia virus (VACV) and variola virus (VARV), with the latter being causal agent of smallpox and excessive mortality. The aim in this review is to present facts about MPXV specific pathogenesis, epidemiology, and immunology alongside historical perspectives. Monkeypox virus was rarely reported outside Africa before April 2000. Early research since 1796 contributed towards eradication of VARV leading to immunisation strategies. The World Health Organisation (WHO) announcement that VARV had been eradicated was confirmed in 1980. On the 23rd of July 2022, the WHO announced MPXV as a health emergency. Therefore, concern due to propagation of MPXV causing MPOX disease requires clarity. Infected hosts display symptoms like extensive cellular initiated rashes and lesions. Infection with MPXV makes it difficult to differentiate from other diseases or skin conditions. Anti–viral therapeutic drugs were typically prescribed for smallpox and MPOX disease; however, the molecular and immunological mechanisms with cellular changes remain of interest. Furthermore, no official authorised treatment exists for MPOX disease. Some humans across the globe may be considered at risk. Historically, presenting symptoms of MPOX resemble other viral diseases. Symptoms include rashes or lesions like Streptococcus, but also human herpes viruses (HHV) including Varicella zoster (VZV).