Profiling of viral load, antibody and inflammatory response of people with monkeypox during hospitalization: a prospective longitudinal cohort study in China

Abstract

Background: The dynamics of viral shedding and the specific humoral response against monkeypox virus (MPXV) have not been well characterized in patients across their disease course during hospitalisation. The aim of this study was to determine the viral load and the levels of antibodies against MPXV using longitudinal paired-collected samples from hospitalized patients.

Methods: Patients who were hospitalised with mpox were recruited at Beijing Ditan Hospital Capital Medical University in China between June 2 and September 23, 2023. Paired samples, including samples from skin lesions, the oropharynx, saliva, faeces, urine, plasma, and serum, were serially collected at days 1, 3, 7, and 14 after admission until discharge. Not all of the patients had samples obtained at all of the timepoints. All the samples were analysed via quantitative PCR. Virus isolation was performed by using clinical samples and Vero cells. The presence of IgM, IgA, IgG, and neutralising antibodies (NAbs) against MPXV was evaluated. The first collected plasma sample was taken when the patient was hospitalised, and the levels of cytokines and chemokines were measured in the sample. The demographic data, smallpox vaccination status, history of known exposure to MPVX, HIV status and other clinical data were collected using a standard case report form.

Findings: A total of 510 specimens were serially collected from 39 recruited people with mpox. Among all the samples, the skin lesions had the highest viral DNA detection rates and viral loads, and the saliva samples had the second highest rates and viral loads. One day before discharge, 85% of the dry scrabs (median Ct 28.2, range 19.0-38.3) and 70% of the saliva samples (median Ct 32.4, range 24.5-38.1) were positive for viral DNA, Of which, 23.1% of dry scrabs were positive in viral culture. The rate of viral DNA detection in the oropharyngeal, saliva, and faecal samples decreased with time, while the rates in the plasma, serum, and urine samples increased quickly before 10 days post symptom onset (PSO). The median days of appearance of MPXV-IgM, MPXV-IgA, MPXV-IgG, and NAb were at 8 (interquartile range [IQR] 7-9), 9 (7-10), 12 (9-15), and 12 (9-15) PSO, respectively. The IgM, IgA, IgG, and NAb titres increased with time. Between days 11 and 21 PSO, the NAb titres were lower in people living with HIV (PWH) than in people living without HIV (PWOH). Increased NAb titres were associated with decreased viral loads in the saliva (r = 0.28, p = 0.025), faeces (r = 0.35, p = 0.021), plasma (r = 0.30, p = 0.0044), and serum samples (r = 0.37, p = 0.001). Compared with PWOH, PWH had higher plasma levels of MIP-1α, MIP-1β, G-CSF, IL-4, and FGF-basic.

Interpretation: The high positive viral culture rate of clinical samples of patients when they are discharged from the hospital indicates that effective public health management strategies are needed for people with mpox. The low NAb titres and high levels of cytokines in PWH shows that earlier treatment is needed to control inflammation in high-risk populations.

Funding: National Natural Science Foundation of China, Chinese Academy of Medical Sciences, Fundamental Research Funds for the Central Universities for Peking Union Medical College, National Key R&D Program of China.

Keywords: Antibody; Cytokines; Monkeypox virus; Temporal changes; Viral load.

Fig. 1

Flow chart of the study.

Fig. 2

The kinetics of the load and detection rate for viral DNA and temporal trend curves for specimens collected from patients infected with monkeypox virus (MPXV). (a) Fitted curve of the detection rate of viral DNA in skin lesion, oropharynx, saliva, faeces, urine, plasma, and serum samples by PCR on different days post symptom onset. The dots represent the PCR detection rates at each timepoint. (b) Dynamics of viral load in association with days post symptom onset in skin lesion, oropharynx, saliva, faeces, urine, plasma, and serum samples. The dots represent one sample per patient at each time point. The fitted curves were created by GraphPad Software.

Fig. 3

Characteristics of plasma antibodies in patients infected with monkeypox virus (MPXV). The detectable time (a) and cumulative seroconversion (b) of IgM, IgA, IgG, and neutralising antibodies against MPXV over time post symptom onset, as determined by ELISA (IgM, IgA, IgG) and PRNT (neutralising antibody) using plasma samples. (c) Temporal changes in IgM, IgA, IgG, and neutralising antibody titres against MPXV in plasma samples determined by the locally weighted scatterplot smoothing method. The antibody titres were log2 transformed. The dots in panels a and c represent one sample per patient at each time point. The dots in panel b represent the cumulative detection rates of antibodies in all the samples at each timepoint. The red dots shown in panel c represent the two patients, who were born in 1972 and 1975, respectively, who were vaccinated. Ig, immunoglobulin; ELISA, enzyme-linked immunosorbent assay; PRNT, plaque reduction neutralization test.

Fig. 4

The correlation between neutralising antibody titres and viral load. The correlation between neutralising antibody titres and viral load in skin lesions (a), saliva (b), faeces (c), and plasma (d). The dots in the panels represent one sample per patient at each time point. The neutralizing antibody titres were log2 transformed.