Figure 1.

(A) Rash on patient’s left arm on symptom day 9. (B) Antibody responses against Zika virus (ZIKV) and dengue virus (DENV) on symptom days 7, 9, 15, and 29. Gray box, 11-day exposure risk period during travel; *, estimated day of infection in the middle of the exposure period. Black arrow indicates symptom day 4 when serum and urine polymerase chain reactions were positive for ZIKV and serum was negative for DENV and chikungunya virus. Immunoglobulin (Ig)M (in red) was not detectable on day 7 but was positive on days 9, 15, and 29. Horizontal red dashed line indicates IgM ratio positive cutoff of ≥3. Focus reduction neutralization test (FRNT) for ZIKV (in blue) was <30 on day 7 but became positive (≥titer of 30; cutoff shown with dashed blue horizontal line); DENV-4 titer was <30 on days 7 and 9 but was positive on days 15 and 29. (C) Focus reduction neutralization test. Day 29 serum neutralized both ZIKV and DENV-4 but with a higher titer against ZIKV (1724) than DENV-4 (327), which is consistent with this ZIKV infection being an initial flavivirus infection in this patient. (D) Plasmablasts and activated CD4⁺ and CD8⁺ T cells on symptom days 9, 15, and 29. CD27⁺CD38⁺ plasmablasts (antibody-secreting B cells; solid black line) had a robust detected peak at the first time-point studied (symptom day 9) then decreased. A very strong peak in human leukocyte antigen (HLA)-DR⁺CD38⁺ activated CD8⁺ T cells (dashed tan line) occurred later (symptom day 15), and they were still elevated on day 29, suggesting ongoing antigenic stimulation. The HLA-DR⁺CD38⁺ CD4⁺ T cells (dotted black lines) had a much more modest detected peak on day 9. (E) ZIKV-specific CD4⁺ or CD8⁺ T-cell responses in peripheral blood mononuclear cells from day post symptom onset (DPO) 27. The percentages of total cytokine-producing cells among all CD4⁺ or CD8⁺ T cells were determined by intracellular cytokine staining and flow cytometry; results are shown for peptide pools spanning all 10 ZIKV proteins. Results for production of 5 cytokines (interferon-γ, interleukin-2, tumor necrosis factor-α, CD107, and macrophage inflammatory protein-1β) were summed in a Boolean analysis. Percentages >0.1% (bolded in the table) were considered significantly elevated relative to healthy human controls (data not shown). The patient’s CD4⁺ T cells mounted their strongest DPO 27 response against the nonstructural proteins NS1 and NS5. The patient’s CD8⁺ T cells mounted their strongest response against the structural protein E and the nonstructural proteins NS3 and NS5.