www.thelancet.com/infection Vol 24 November 2024 / 線上發布 September 2, 2024 https://doi.org/10.1016/ S1473-3099(24)00556-5

猴痘病毒 (MPXV) 是一種人畜共通病毒，也是猴痘（以前稱為猴痘）疾病的病原體，以前僅限於奈及利亞和剛果民主共和國等國家，但偶爾在全球範圍內輸入。然而，2022 年，全球爆發了 IIb 分支 MPOX，主要在同性戀、雙性戀和其他男男性行為者中傳播，在118 個國家有超過 98 000 例病例，183 人死亡。mpox I分支仍孤立於剛果民主共和國等地區流行乏國家，但仍引起大量爆發。巴伐利亞北歐IMVANEX（即Jynneos）天花疫苗因其對mpox疾病的交叉保護，因而受到世界各地公共衛生當局的推薦。

因此，雖然mpox正在持續傳播，但需要對病例進行快速診斷（IgM檢測）以確認抗體狀態並告知高風險個體的患者疫苗接種建議（例如加強建議），或進行血清監測研究確定疾病在人群中的真實傳播情況。我們先前開發了支持 MPOX 血清學的檢測方法，用於免疫原性、研究和血清監測研究，但是，這些需要使用多抗原 ELISA 和專用平台。因此，我們試圖了解抗體側流裝置 (LFD) 在評估 MPOX 和疫苗衍生免疫和診斷方面的效用，以便在現場和高流行地區（例如剛果民主共和國）使用。

         使用五種不同的市售MPXV 特異性抗體LFD，旨在檢測抗MPXV IgG（在某些情況下為IgM）抗體的存在，我們使用了一組正痘病毒陰性、mpox 恢復期（2022 Clade IIb 和2018 Clade II），以及IMVANEX 接種的血清樣本用於測試每個 LFD 的敏感性和特異性。所有LFD 對陰性樣本均具有高特異性（在一個LFD 上只有一個樣本對IgM 呈陽性），但更重要的是，所有LFD 在MPOX 恢復期樣本和/或IMVANEX 後樣本中的敏感性均低於56%（表，附錄p） 3）。一些檢測甚至未能檢測到不到 3% 的陽性樣本，這表明這些 LFD 中使用了非免疫顯性抗原。我們先前的工作強調了mpox感染和IMVANEX疫苗接種之間相似的體液抗原識別，其中一些抗原的識別有所不同。製造商可能選擇了一種總是能被正痘病毒感染或疫苗接種識別的抗原。

這些發現對使用側流裝置 (lateral flow devices) 進行mpox監測和診斷提出了相當大的質疑，因為缺乏檢測到的恢復期樣本，也沒有觀察到mpox病毒疫苗接種的交叉反應。在建議將此類 LFD 廣泛用於公共衛生措施或人口層級監測研究之前，應認真考慮和驗證其可靠性和準確性。

雖然抗原 LFDs 已顯示出前景，但這些都還沒有商業化。我們的研究結果支持需要開發一種新的 MPOX 抗體 LFD，用於快速診斷、監測和優先考慮後續醫療介入措施，更準確地針對高危險群，特別是在全球 MPOX 病例數量持續增加的情況下。

表：mpox 側流裝置的特性和性能

我們聲明不存在競爭利益。

托比瓊斯、史考特瓊斯、貝瑟尼希克斯、漢娜塞爾曼、凱西羅、

*艾希莉D歐特 ashley.otter@ukhsa.gov.uk

英國衛生安全局疫苗開發與評估中心 (VDEC) 新興病原體血清學小組，Porton Down SP4 0JG，英國（TJ、SJ、BH、HS、CR、ADO）；英國南安普敦大學醫院 NHS 基金會信託基金會微生物學系 (HS)

Limitations of mpox lateral flow tests in assessing orthopoxvirus immunity

www.thelancet.com/infection Vol 24 November 2024  / Published Online September 2, 2024 https://doi.org/10.1016/ S1473-3099(24)00556-5

Monkeypox virus (MPXV) is a zoonotic virus and the causative agent of mpox (formerly known as monkeypox) disease1 previously limited to countries, such as Nigeria and the Democratic Republic of the Congo, except for occasional importations globally. However, in 2022 a global outbreak of Clade IIb mpox occurred spreading primarily within gay, bisexual, and other men-who-have-sex-with-men with more than 98 000 cases and 183 deaths across 118 countries.2 Clade I mpox remains isolated to endemic countries, such as the Democratic Republic of the Congo, but still causes considerable outbreaks.3 The Bavarian Nordic IMVANEX (ie, Jynneos) smallpox vaccine has been recommended by public health authorities worldwide because of its cross-protection against mpox disease.

Therefore, while there is ongoing spread of mpox, there is a requirement for rapid diagnosis of cases (IgM detection) to confirm antibody status and inform on patient vaccination recommendations in at-risk individuals (eg, booster recommendations), or to conduct serosurveillance studies to establish the true spread of disease in a population. We previously developed assays to support with mpox serology for immunogenicity, research, and serosurveillance studies,4 however, these require the use of multi-antigen ELISAs and dedicated platforms. As such, we sought to understand the utility of antibody lateral flow devices (LFDs) to assess both mpox and vaccine-derived immunity and diagnosis for use within the field and high-endemicity regions, such as the Democratic Republic of the Congo.

        Using five different commercially available MPXV-specific antibody LFDs designed to detect the presence of anti-MPXV IgG (and in some cases IgM) antibodies, we used a panel of orthopoxvirus negative, mpox convalescent (2022 Clade IIb and 2018 Clade II), and IMVANEX-vaccinated serum samples to test sensitivity and specificity of each LFD. All LFDs had high specificity on negative samples (only a single sample was positive to IgM on one LFD), but more importantly, all had less than 56% sensitivity in mpox-convalescent samples, and or post-IMVANEX samples (table, appendix p 3). Some assays even failed to detect less than 3% of positive samples, suggesting the use of non-immunodominant antigen within these LFDs. Our previous work highlighted similar humoral antigen recognition between mpox infection and IMVANEX vaccination,4 with some antigens variably recognised. It is possible that the manufacturers chose an antigen that is invariably recognised by orthopoxvirus infection or vaccination.

        These findings raise considerable doubts on the use of lateral flow devices for mpox surveillance and diagnosis, with a lack of convalescent samples detected and cross-reaction by poxvirus vaccination observed. Serious considerations and validation should be made regarding the reliability and accuracy of such LFDs before they are recommended for widespread use in public health initiatives or population-level surveillance studies.

        While antigen LFDs have shown promise,5 none of these have become commercially available. Our findings support the need for the development of a new mpox antibody LFD for quick diagnosis, surveillance, and prioritising subsequent medical interventions more accurately targeted to the most at-risk people, especially with the ongoing sustained number of mpox cases globally.

Table: Characteristics and performance of mpox lateral flow devices

We declare no competing interests.

Toby Jones, Scott Jones, Bethany Hicks, Hannah Selman, Cathy Rowe, *Ashley D Otter ashley.otter@ukhsa.gov.uk

Emerging Pathogen Serology group, Vaccine Development and Evaluation Centre (VDEC), UK Health Security Agency, Porton Down SP4 0JG, UK (TJ, SJ, BH, HS, CR, ADO); Department of Microbiology, University Hospital Southampton NHS Foundation Trust, Southampton, UK (HS)