Fig. 4

Elevated tissue viral load during is associated with suppression of CHIKV neutralizing antibodies production in the spleen. CHIKV-specific IgM (a) and total IgG (b) titer in the sera of CHIKV (n = 6) and CHIKV + PbA (n = 6) mice at 6 dpi and 15 dpi. c Neutralization of CHIKV infection in HEK293T cells using serum from CHIKV (n = 6) and CHIKV + PbA (n = 6) groups at 6 dpi and 15 dpi. CHIKV-specific IgM (d) and total IgG (e) titer in the sera of CHIKV (n = 7) and Py17x (−4 dpi) + CHIKV (n = 5) on 6 dpi and 15 dpi. f Neutralization of CHIKV infection in HEK293T cells using serum from CHIKV (n = 7) and Py17x (−4 dpi) + CHIKV (n = 5) groups at 6 dpi and 15 dpi. CHIKV-specific IgM and IgG titers were determined at 1:200 and 1:2000 respectively. Black dotted lines represents average OD reading of naïve mice for IgM and IgG. CHIKV neutralization assay was determined at 1:125 and 1:2000 dilution. Data in a–f were analyzed by Mann–Whitney two-tailed test (*P < 0.05 and **P < 0.01) and are representative of two independent experiments. g Joint inflammation, h, viraemia and viral load in the whole body (i) and footpad (j) of Control + CHIKV (n = 5), Control + CHIKV + PbA (n = 4), Splenectomy + CHIKV (n = 5) and Splenectomy + CHIKV + PbA (n = 5) groups. The green box denotes joint measurement during peak swelling whereby data were transformed to be expressed as relative to the mean of CHIKV infected mice in the respective background. The orange box denotes elevated tissue viral load in the control + CHIKV + PbA mice, which is prevented in the splenectomy + CHIKV + PbA mice. Data from co-infected mice were compared with their respective CHIKV infected controls by Mann-Whitney two-tailed analysis. Control + CHIKV versus Control + CHIKV + PbA comparison (*P < 0.05); Splenectomy + CHIKV versus Splenectomy + CHIKV + PbA (⁺P < 0.05 and ⁺⁺P < 0.01). Data represent the means ± SD. Abbreviations: CHIKV, Chikungunya virus; dpi, days post infection; ns, not significant; OD, optical density; PbA, Plasmodium berghei-ANKA; Py17x, Plasmodium yoelii 17×