Studies have reported more than 60,000 human cases of monkeypox in non-endemic countries as of May 2022. The current outbreak has been noted to be different from previous monkeypox infections in central and western Africa. This was due to the asynchronous evolution of the lesions, as well as more frequent perianal and genital locations. This unusual outbreak of monkeypox virus led the scientific community to discuss vaccination strategies for high-risk groups, which were mostly men who have sex with men.
Study: Immunological signature in human cases of monkeypox infection in the 2022 outbreak: an observational study. Image credit: Dotted Yeti/Shutterstock
background
Smallpox vaccine has been reported to be 85% cross-protective against monkeypox virus. However, its limitations include the restriction to people aged 40 and over and the debatable background immunity. The unavailability of protective immunity among the young may result in the circulation of monkeypox virus among humans.
Previous experiments in animal models suggest that all immune players assist in viral clearance, with CD8+ T cells being the most important. In addition, one study reported that all convalescent cases were positive for orthopoxvirus-specific IgG, IgM, B-cell, and T-cell responses. In addition, an orthopoxvirus-specific immune response was observed in some individuals who did not develop monkeypox infection.
It was noted that the smallpox vaccination could not provide complete protection against the smallpox virus, but could protect against serious disease. In addition, cytokine overproduction has been observed in patients with severe monkeypox infection, suggesting a link between clinical severity and an unbalanced immune response. However, no information is available on the dynamics of the immune response in humans in the current outbreak.
A new study published in The Lancet Infectious Diseases aimed to analyze the kinetics of smallpox-specific T-cell induction, the inflammatory profile, and the inflammatory profile in human cases from the current monkeypox outbreak.
About the study
The study included 17 patients with laboratory-confirmed monkeypox virus positivity tested 10 to 12 days after the onset of symptoms and ten healthy controls. The samples collected from all patients were divided into four groups: T0-T3, T4-T7, T8-T11 and T12-T20 days from the onset of symptoms. Demographic, epidemiological, laboratory and clinical data were collected from all patients.
Flow cytometry was performed to analyze the activation and differentiation of CD4+ and CD8+ T cells. Standard interferon-γ ELISpot was used to determine the frequency of T cell response to modified vaccinia virus Ankara (MVA) peptides. Assessment of spontaneous cytokine production was performed by incubating peripheral blood mononuclear cells (PBMCs) collected from all participants in DMSO. An ELISA assay was performed to assess cytokine production after specific stimulation. Finally, IL-1β, IL-6, IL-8 and TNF were quantified in patients’ plasma using automated multiplex immunoassays.
Results of the study
The results indicated that the mean age of the patients was 39.5 years. 7 were reported to be seropositive with antiretroviral therapy, but undetectable HIV RNA and a CD4+ T-cell count greater than 350 cells/µl. All 10 HIV-negative participants were reported to be on pre-exposure prophylaxis (PrEP). The route of transmission was reported to be sexual intercourse for 14 patients.
Systemic symptoms were observed in 14 patients, while those without systemic symptoms were considered paucisymptomatic. One patient had received a smallpox vaccine during childhood, while five were treated with antiviral drugs. The average recovery time was reported to be 15 days.
A lower percentage of CD4+ T cells and a higher percentage of CD8+ T cells were reported in patients early after infection compared to healthy controls. Six out of nine cases of monkeypox were reported to have a lower naïve CD4+ T cell frequency than healthy controls. A lower proportion of naïve and superior terminally differentiated CD8+ T cells was observed in all patients. However, the ratio of the frequency of CD4 + effector memory T cells was observed to be similar in patients and healthy controls after 12 to 20 days.
A higher frequency of CD4+CD38+ and CD8+CD38+ T cells was observed in patients compared to healthy controls, which were also similar for PD-1 and CD57 markers. No differences in immune cell profile were observed between HIV-positive and HIV-negative patients, while a less altered immune profile was observed for paucisymptomatic patients. Higher inflammatory cytokines (IL-1β, IL-6, IL-8, and TNF) were observed in patients with monkeypox virus compared to controls that remained higher even after recovery.
In addition, higher expression of CCR7, CD69, CXCR5, CD95, CCR6, CXCR3, CD28, CD4RA and CD27 was observed in patients compared to healthy controls in the post-acute phase. Similar results were observed for CD8+ T cells along with CD45RA reexpression. In addition, monkeypox patients showed a higher percentage of CD45RA-reexpressing memory effector T cells that expressed CD57, PD1, or both.
Therefore, the current study demonstrated an early expansion of activated CD4+ and CD8+ effector T cells as a result of monkeypox virus infection that persists over time. All participants also developed a strong cytokine response regardless of HIV infection. Thus, MVA vaccine can be used as a monkeypox vaccine for the high-risk population. Further research on prolonged immunity is required to support the current hypothesis.
limitations
The study has certain limitations. First, data on humoral response analysis were not available. Second, only three poxvirus proteins were used as antigens. Third, the study does not involve a random selection of participants. Fourth, the number of participants was limited.