Memory profiles distinguish cross-reactive and virus-specific T cell immunity to mpox

Monkeypox 2024 outbreak: Fifty essential questions and answers

As the world still vividly recalls the previous monkeypox (mpox) outbreak that impacted over 120 countries worldwide with more than 99,000 cases in 2022, we are now facing a second wave of infections from the monkeypox virus (MPXV), characterized by an exponential increase in cases. The current 2024 outbreak has already recorded more than 20,000 cases in Africa, marking a dramatic escalation compared to previous outbreaks. The predominance of the newly identified clade Ib variant, first detected in the Democratic Republic of the Congo (DRC) and now identified across multiple African nations and beyond, underscores its enhanced transmissibility and potential for international spread, evidenced by cases in Sweden and Thailand. The World Health Organization (WHO) declared on August 14, 2024, the current mpox outbreak a Public Health Emergency of International Concern (PHEIC), calling for heightened global public health measures. The ongoing pattern of unusual, frequent, and extensive outbreaks of mpox with potential global implications poses significant questions. This review addresses, in the format of 50 questions and answers, the 2024 mpox outbreak, detailing its characteristics, epidemiological data, and impact compared to previous outbreaks. It comprehensively explores critical questions related to MPXV virological characteristics, immunological response, clinical manifestations, epidemiology, diagnostics, and available treatments. The review also documents the significant and evolving challenges posed by the current mpox outbreak, highlighting its scale, spread, and public health response.

Mpox-Specific Immune Responses Elicited by Vaccination or Infection in People With HIV

In the recent mpox outbreak, people with human immunodeficiency virus (PWH) were at high risk both for contracting infection and for a more severe disease course. We studied cellular and humoral immune responses elicited by mpox infection (n = 5; n = 3 PWH) or smallpox vaccination (n = 17; all PWH) in a cohort of men who have sex with men. All PWH were successfully treated, with stable CD4 counts and undetectable HIV viral loads. Eleven of 17 vaccinated individuals had received childhood smallpox vaccination. In this group of individuals, both 2-dose modified vaccinia Ankara (MVA) vaccination and natural infection evoked mpox-specific immune responses mediated by B cells as well as CD4 and CD8 T cells. This study improves our understanding of smallpox vaccination-mediated cross-reactivity to other orthopox viruses, and long-lasting durability of childhood smallpox vaccination-mediated immune responses, including in PWH.

The monkeypox virus-host interplays

Monkeypox virus (MPXV) is a DNA virus belonging to the Orthopoxvirus genus within the Poxviridae family which can cause a zoonotic infection. The unexpected non-endemic outbreak of mpox in 2022 is considered as a new global threat. It is imperative to take proactive measures, including enhancing our understanding of MPXV's biology and pathogenesis, and developing novel antiviral strategies. The host immune responses play critical roles in defensing against MPXV infection while the virus has also evolved multiple strategies for immune escape. This review summarizes the biological features, antiviral immunity, immune evasion mechanisms, pathogenicity, and prevention strategies for MPXV.

Diagnostic Value of SAA Levels and Perianal Symptoms in the Complicated Perianal Abscesses Among Mpox-Infected Patients

Objective

Precise prediction of the occurrence of complicated perianal abscesses (PAs) in monkeypox (mpox)-infected patients is important for therapeutic optimization. This study sought to identify risk factors of complicated PA.

Methods

A total of 48 patients with mpox infection (PA group, n = 10; non-PA (NPA) group, n = 38) were enrolled in our study, who were hospitalized in Hangzhou Xixi Hospital, China from 29 June to 3 September 2023. The data of demographic characteristics, and clinical symptoms, serum SAA, PCT, CRP, and IL-6 levels were collected by the Electronic Medical Record. The diagnostic values of these biomarkers were assessed using multivariate logistic regression and ROC curve analyses.

Results

A decrease in serum IL-6, SAA, and CRP levels (all p-value < 0.05), but not PCT, was observed in all mpox-infected patients. A significant positive correlation was also noted between IL-6, SAA, CRP, and PCT levels (all p-value < 0.05). There was a significant increase in IL-6 and SAA levels and the SAA/CRP ratio in serum samples from patients in the PA group. Multivariate logistic regression and ROC curve analyses identified that the combined use of perianal symptoms and SAA was more sensitive than perianal symptoms or SAA alone as predictors of complicated PA. This combination had the highest predictive value for disease progression, with an AUC of 0.920 (p-value < 0.001).

Conclusion

The combination of perianal symptoms and SAA levels was strongly linked to the occurrence of complicated PA in mpox-infected patients. These findings may inform the early diagnosis of this patient population.

Characterization of the Monkeypox Virus [MPX]-Specific Immune Response in MPX-Cured Individuals Using Whole Blood to Monitor Memory Response

BACKGROUND

Monkeypox (Mpox) is a zoonotic disease caused by monkeypox virus (MPXV), an Orthopoxvirus (OPXV). Since we are observing the first MPXV outbreak outside the African continent, the general population probably does not have a pre-existing memory response for MPXV but may have immunity against the previous smallpox vaccine based on a live replicating Vaccinia strain (VACV). Using a whole blood platform, we aim to study the MPXV- T-cell-specific response in Mpox-cured subjects.

METHODS

We enrolled 16 subjects diagnosed with Mpox in the previous 3-7 months and 15 healthy donors (HD) with no recent vaccination history. Whole blood was stimulated overnight with MPXV and VACV peptides to elicit CD4 and CD8 T-cell-specific responses, which were evaluated by ELISA and multiplex assay.

RESULTS

Mpox-cured subjects showed a significant IFN-γ T-cell response to MPXV and VACV. Besides IFN-γ, IL-6, IP-10, IL-8, IL-2, G-CSF, MCP-1, MIP1-α, MIP-1β, IL-1Rα, and IL-5 were significantly induced after specific stimulation compared to the unstimulated control. The specific response was mainly induced by the CD4 peptides MPX-CD4-E and VACV-CD4.

CONCLUSIONS

We showed that MPXV-specific responses have a mixed Th1- and Th2-response in a whole blood platform assay, which may be useful for monitoring the specific immunity induced by vaccination or infection.

Innate Immune Response to Monkeypox Virus Infection: Mechanisms and Immune Escape

BACKGROUND

The reemergence of monkeypox virus (Mpox, formerly monkeypox) in 2022 in non-endemic countries has raised significant concerns for global health due to its high transmissibility and mortality rate. A major challenge in combating Mpox is its ability to evade the host's innate immune system, the first line of defense against viral infections.

SUMMARY

Mpox encodes various proteins that interfere with key antiviral pathways and mechanisms, such as the nuclear factor kappa B signaling, cytokine production, complement and inflammasome activation, and chemokine binding. These proteins modulate the expression and function of innate immune mediators, such as interferons, interleukins, and Toll-like receptors, and impair the recruitment and activation of innate immune cells, such as natural killer cells. By suppressing or altering these innate immune responses, Mpox enhances its replication and infection in the host tissues and organs, leading to systemic inflammation, tissue damage, and organ failure.

KEY MESSAGES

This study reveals new insights into the molecular and cellular interactions between Mpox and the host's innate immune system. It identifies potential targets and strategies for antiviral interventions, highlighting the importance of understanding these interactions to develop effective treatments and improve global health responses to Mpox outbreaks.

Immune responses associated with mpox viral clearance in men with and without HIV in Spain: a multisite, observational, prospective cohort study

BACKGROUND

Since the emergence of the global mpox outbreak in May, 2022, more than 90 000 cases have been diagnosed across 110 countries, disproportionately affecting people with HIV. The durability of mpox-specific immunity is unclear and reinfections have been reported. We aimed to compare mpox immune responses up to 6 months after diagnosis in participants with and without HIV and assess their effect on disease severity and viral clearance dynamics.

METHODS

This study was embedded within a prospective, observational, multicentre cohort study of viral clearance dynamics among people with mpox in Spain (MoViE). We included women and men aged 18 years or older, who had signs of mpox, and reported having symptom onset within the previous 10 days at the moment of mpox diagnosis from three sex clinics of the Barcelona metropolitan area. Samples from skin ulcers were collected weekly to estimate the time to clear monkeypox virus (MPXV) from skin lesions. Blood samples were taken at diagnosis, 29, 91, and 182 days later for immune analysis. This included quantifying IgG and IgA against three mpox antigens by ELISA, evaluating in-vitro neutralisation, and characterising mpox-specific T-cell responses using interferon γ detecting enzyme-linked immunospot (ELISpot) assay and multiparametric flow cytometry.

FINDINGS

Of the 77 originally enrolled participants, we included 33 participants recruited between July 19, and Oct 6, 2022. Participants without HIV (19 [58%] participants) and participants with HIV (14 [42%] participants) had similar clinical severity and time to MPXV clearance in skin lesions. Participants with HIV had a CD4+ T-cell count median of 777 cells per μL (IQR 484-1533), and 11 (78%) of 14 were virally suppressed on antiretroviral therapy. Nine (27%) of 33 participants were age 49 years or older. 15 (45%) of 33 participants were originally from Spain, and all participants were men. Early humoral responses, particularly concentrations and breadth of IgG and IgA, were associated with milder disease and faster viral clearance. Orthopoxvirus-specific T cells count was also positively correlated with MPXV clearance. Antibody titres declined more rapidly in participants with HIV, but T-cell responses against MPXV were sustained up to day 182 after diagnosis, regardless of HIV status.

INTERPRETATION

Higher breadth and magnitude of B-cell and T-cell responses are important in facilitating local viral clearance, limiting mpox dissemination, and reducing disease severity in individuals with preserved immune system. Antibodies appear to contribute to early viral control and T-cell responses are sustained over time, which might contribute to milder presentations during reinfection.

FUNDING

Fundació Lluita contra les Infeccions, IrsiCaixa, and Consorcio Centro de Investigación Biomédica en Red, Instituto de Salud Carlos III, Ministerio de Ciencia, Innovación e Universidades.

The emerging role of effector functions exerted by tissue-resident memory T cells

The magnitude of the effector functions of memory T cells determines the consequences of the protection against invading pathogens and tumor development or the pathogenesis of autoimmune and allergic diseases. Tissue-resident memory T cells (TRM cells) are unique T-cell populations that persist in tissues for long periods awaiting re-encounter with their cognate antigen. Although TRM cell reactivation primarily requires the presentation of cognate antigens, recent evidence has shown that, in addition to the conventional concept, TRM cells can be reactivated without the presentation of cognate antigens. Non-cognate TRM cell activation is triggered by cross-reactive antigens or by several combinations of cytokines, including interleukin (IL)-2, IL-7, IL-12, IL-15 and IL-18. The activation mode of TRM cells reinforces their cytotoxic activity and promotes the secretion of effector cytokines (such as interferon-gamma and tumor necrosis factor-alpha). This review highlights the key features of TRM cell maintenance and reactivation and discusses the importance of effector functions that TRM cells exert upon being presented with cognate and/or non-cognate antigens, as well as cytokines secreted by TRM and non-TRM cells within the tissue microenvironment.

Smallpox vaccination campaigns resulted in age-associated population cross-immunity against monkeypox virus

Increased human-to-human transmission of monkeypox virus (MPXV) is cause for concern, and antibodies directed against vaccinia virus (VACV) are known to confer cross-protection against Mpox. We used 430 serum samples derived from the Scottish patient population to investigate antibody-mediated cross-neutralization against MPXV. By combining electrochemiluminescence immunoassays with live-virus neutralization assays, we show that people born when smallpox vaccination was routinely offered in the United Kingdom have increased levels of antibodies that cross-neutralize MPXV. Our results suggest that age is a risk factor of Mpox infection, and people born after 1971 are at higher risk of infection upon exposure.

Simultaneous analysis of pMHC binding and reactivity unveils virus-specific CD8 T cell immunity to a concise epitope set

CD8 T cells provide immunity to virus infection through recognition of epitopes presented by peptide major histocompatibility complexes (pMHCs). To establish a concise panel of widely recognized T cell epitopes from common viruses, we combined analysis of TCR down-regulation upon stimulation with epitope-specific enumeration based on barcode-labeled pMHC multimers. We assess CD8 T cell binding and reactivity for 929 previously reported epitopes in the context of 1 of 25 HLA alleles representing 29 viruses. The prevalence and magnitude of CD8 T cell responses were evaluated in 48 donors and reported along with 137 frequently recognized virus epitopes, many of which were underrepresented in the public domain. Eighty-four percent of epitope-specific CD8 T cell populations demonstrated reactivity to peptide stimulation, which was associated with effector and long-term memory phenotypes. Conversely, nonreactive T cell populations were associated primarily with naive phenotypes. Our analysis provides a reference map of epitopes for characterizing CD8 T cell responses toward common human virus infections.

A Case of Varicella Zoster and Mpox Coinfection in a Patient Living With HIV

ABSTRACT

We present a case of recurrent, cutaneous mpox with coinfection of disseminated varicella zoster in an immunocompromised patient with poorly controlled HIV. This case demonstrates the importance of maintaining a high index of suspicion for mpox despite prior infection and vaccination, as suboptimal immune response is possible in immunocompromised patients, and also noting the potential for coinfection necessitating timely diagnosis and appropriate testing.

Long-lasting humoral and cellular memory immunity to vaccinia virus Tiantan provides pre-existing immunity against mpox virus in Chinese population

Investigating immune memory to vaccinia virus and pre-existing immunity to mpox virus (MPXV) among the population is crucial for the global response to this ongoing mpox epidemic. Blood was sampled from vaccinees inoculated with vaccinia virus Tiantan (VTT) strain born before 1981 and unvaccinated control subjects born since 1982. After at least 40 years of the inoculation, 60% or 5% VTT vaccinees possess neutralizing antibodies (NAbs) to VTT or MPXV, with at least 50% having T cell memory to VTT protein antigens. Notably, 46.7% vaccinees show pre-existing T cell responses to MPXV. Broad pre-existing CD8+ T cell reactivities to MPXV are detected not only against conserved epitopes but also against variant epitopes between VTT and MPXV. Persistent NAbs and T cell memory to VTT among vaccinees, along with pre-existing T cells to MPXV among both vaccinees and the unvaccinated population, indicate a particular immune barrier to mpox.

Mpox (formerly monkeypox): pathogenesis, prevention, and treatment

In 2022, a global outbreak of Mpox (formerly monkeypox) occurred in various countries across Europe and America and rapidly spread to more than 100 countries and regions. The World Health Organization declared the outbreak to be a public health emergency of international concern due to the rapid spread of the Mpox virus. Consequently, nations intensified their efforts to explore treatment strategies aimed at combating the infection and its dissemination. Nevertheless, the available therapeutic options for Mpox virus infection remain limited. So far, only a few numbers of antiviral compounds have been approved by regulatory authorities. Given the high mutability of the Mpox virus, certain mutant strains have shown resistance to existing pharmaceutical interventions. This highlights the urgent need to develop novel antiviral drugs that can combat both drug resistance and the potential threat of bioterrorism. Currently, there is a lack of comprehensive literature on the pathophysiology and treatment of Mpox. To address this issue, we conducted a review covering the physiological and pathological processes of Mpox infection, summarizing the latest progress of anti-Mpox drugs. Our analysis encompasses approved drugs currently employed in clinical settings, as well as newly identified small-molecule compounds and antibody drugs displaying potential antiviral efficacy against Mpox. Furthermore, we have gained valuable insights from the process of Mpox drug development, including strategies for repurposing drugs, the discovery of drug targets driven by artificial intelligence, and preclinical drug development. The purpose of this review is to provide readers with a comprehensive overview of the current knowledge on Mpox.

Evaluation of Cross-Immunity to the Mpox Virus Due to Historic Smallpox Vaccination

When the Mpox virus (MPXV) began spreading globally in 2022, it became critical to evaluate whether residual immunity from smallpox vaccination provided cross-protection. To assess the cross-immune response to MPXV, we collected serum samples (n = 97) and PBMCs (n = 30) from healthy-donors, either born before 1974 and reporting smallpox vaccination during childhood or born after 1975 and not vaccinated with Vaccinia virus (VACV)-based vaccines. We evaluated the levels of anti-MPXV IgG and neutralizing antibodies (Nabs) and the presence of a T cell response against MPXV. We found anti-MPXV IgG and Nabs in 60 (89.6%) and 40 (70.1%) vaccinated individuals, respectively. We observed a T cell response to Orthopoxviruses and MPXV peptide pools in 30% of vaccinated individuals. We thus show that a high proportion of subjects who received the smallpox vaccine 40 to 60 years ago have humoral cross-immunity, while the T-cell-specific response against MPXV was observed in a smaller group (30%) of vaccinated individuals. This study, combined with information on immunity developed during natural infection or the administration of current vaccines, will contribute to a better understanding of humoral and cellular responses against MPXV.

Update on Mpox: a brief narrative review

Mpox (formerly Monkeypox), a neglected tropical disease once confined to Central and West Africa, emerged as a global epidemic outbreak in May, 2022 with 87,529 cases reported as of May, 23, 2023. It predominantly affected men (96.2%) who have sex with men (84-100%), although other transmission routes have been reported, including occupational exposure and vertical transmission. Concomitant HIV infection has been recorded in 21-46.9% and pre-exposure prophylaxis against HIV infection has been reported in 11-57% of published cases. The current outbreak clinical presentation differs from endemic cases with prodromal symptoms that could be absent: the number of lesions is generally low, with skin lesions predominantly localised in the ano-genital areas and frequent lesions present in different stages of progression (i.e., asynchronous). Asymptomatic Mpox infection can occur in 1.8-6.5% of at-risk subjects. People living with HIV with severe immunodeficiency (less than 100 CD4+ lymphocytes per microliter) are at risk of more severe clinical manifestations and death. According to a systematic review and meta-analysis, the hospitalisation rate is around 6% and the observed case-fatality rate is less than 0.1%. Tecovirimat is the drug of choice for treating severe cases although there is no evidence of efficacy from randomised controlled trials. Immunization with a live non-replicating vaccine (JYNNEOS) effectively reduces the disease's incidence.

Epidemiologic and Clinical Features of Mpox in Adults Aged >50 Years - United States, May 2022-May 2023

During May 2022-May 2023, approximately 30,000 mpox cases were reported in the United States, predominantly among young adult men. Persons aged >50 years might experience more severe mpox disease because of a higher prevalence of comorbidities. Conversely, they could have residual protection from childhood smallpox vaccination against monkeypox virus infection and severe mpox, as has been suggested by investigation of some previous mpox outbreaks. To examine the characteristics of mpox cases among adults aged >50 years, analysts compared mpox epidemiology and clinical outcomes among all adults aged ≥18 years, by age group. Further, outcomes were compared among adults aged >50 years by JYNNEOS vaccination status. During May 10, 2022-May 17, 2023, among 29,984 adults with probable or confirmed mpox reported to CDC, 2,909 (9.7%) were aged >50 years, 96.3% of whom were cisgender men. Compared with adults aged 18-50 years, adults aged >50 years had higher prevalences of immunocompromising conditions (p<0.001) and HIV infection (p<0.001). Among adults with mpox aged >50 years, 27.6% had received JYNNEOS vaccination; this group had lower prevalences of constitutional symptoms (p<0.001), pruritus (p<0.001), and hospitalization (p = 0.002) compared with those who had not received JYNNEOS vaccine. Currently recommended JYNNEOS vaccination among all adults at risk for mpox should be encouraged, irrespective of childhood smallpox vaccination status.