Long-Term Arthralgia after Mayaro Virus Infection Correlates with Sustained Pro-inflammatory Cytokine Response

Abstract

Mayaro virus (MAYV), an alphavirus similar to chikungunya virus (CHIKV), causes an acute debilitating disease which results in the development of long-term arthralgia in more than 50% of infected individuals. Currently, the immune response and its role in the development of MAYV-induced persistent arthralgia remain unknown. In this study, we evaluated the immune response of individuals with confirmed MAYV infection in a one-year longitudinal study carried out in Loreto, Peru. We report that MAYV infection elicits robust immune responses that result in the development of a strong neutralizing antibody response and the secretion of pro-inflammatory immune mediators. The composition of these inflammatory mediators, in some cases, differed to those previously observed for CHIKV. Key mediators such as IL-13, IL-7 and VEGF were strongly induced following MAYV infection and were significantly increased in subjects that eventually developed persistent arthralgia. Although a strong neutralizing antibody response was observed in all subjects, it was not sufficient to prevent the long-term outcomes of MAYV infection. This study provides initial immunologic insight that may eventually contribute to prognostic tools and therapeutic treatments against this emerging pathogen.

Fig 1. Kinetic profile of cytokines and chemokines similar to the concentrations detected in healthy donor controls following MAYV infection.

Serum samples were collected at the acute visit as well as the convalescent visit (20±10 days), at 90±10 days, at 180±15 days, and at 360±30 days after the acute visit. The serum concentrations of a variety of cytokines were assessed by a multiplex cytokine bead array. The box plot denotes the median, 25^th percentile, and 75^th percentile cytokine levels. The whiskers denote the minimum and maximum cytokine levels observed at each time point. The horizontal dotted line represents the median cytokine values for the healthy donor controls. Comparisons between MAYV infected subjects and healthy donors were performed by a 2-tailed Mann-Whitney test (*p<0.05).

Fig 2. Kinetic profile of cytokines and chemokines significantly affected following MAYV infection.

Serum samples were collected at the acute visit as well as the convalescent visit (20±10 days), at 90±10 days, at 180±15 days, and at 360±30 days after the acute visit. The serum concentrations of a variety of cytokines were assessed by a multiplex cytokine bead array. Three kinetic profiles are presented based on the peak of cytokine expression: Acute: cytokines/chemokines that peak during the acute phase (upon enrollment); Convalescent: cytokines/chemokines that peak during the convalescent phase 20 (±10) days post enrollment and may remain elevated for few months after MAYV infection; and Sustained: cytokines/chemokines whose expression remain elevated up to 12 months following MAYV infection. The box plot denotes the median, 25^th percentile, and 75^th percentile cytokine levels. The whiskers denote the minimum and maximum cytokine levels observed at each time point. The horizontal dotted line represents the median cytokine values for the healthy donor controls. Data sets were evaluated by using Wilcoxon non-parametric tests to evaluate the evolution of cytokine levels at each time point post-infection (*p<0.05).

Fig 3. Induction of cytokine/chemokine immune mediators in MAYV-infected subjects with or without persistent arthralgia.

Serum samples were collected at the acute visit as well as the convalescent visit (20±10 days), at 90±10 days, at 180±15 days, and at 360±30 days after the acute visit. The serum concentrations of a variety of cytokines were assessed by a cytokine bead array. The cytokine concentrations in subjects with (open circles) or without (closed circles) persistent arthralgia were compared to healthy donor controls by a 2-tailed Mann-Whitney test. An asterisk (*) indicates statistical significance (p<0.05) when compared to healthy controls. Comparisons between MAYV infected groups were also performed by a 2-tailed Mann-Whitney test. No statistical significance (p<0.05) between the MAYV infected groups was found. The horizontal dotted line represents the median cytokine values for the healthy donor controls. Each circle corresponds to the cytokine concentration of an individual subject and the solid horizontal line represents the mean cytokine concentration of the group.

Fig 4. Cytokine/chemokine immune mediators in MAYV-infected subjects and potential predictors of MAYV-induced long-term arthralgia.

At the acute visit as well as the convalescent visit (20±10 days), at 90±10 days, at 180±15 days, and at 360±30 days after the acute visit, cytokine concentrations of subjects with (open circles) or without (closed circles) persistent arthralgia were compared to healthy donor controls as well as between MAYV-infected groups by a 2-tailed Mann-Whitney test. An asterisk (*) indicates statistical significance (p<0.05) when compared to healthy controls. The horizontal dotted line represents the median cytokine values for the healthy donor controls. Each circle corresponds to the cytokine concentration of an individual subject and the solid horizontal line represents the mean cytokine concentration of the group. Levels of IL-9 were not significantly different when compared to the healthy control group. Immune mediators on the right are potential predictors of MAYV-induced long-term arthralgia.