ABSTRACT
We aimed to characterize presence of culturable virus in clinical specimens during acute illness, and antibody kinetics up to 6 months after symptom onset, among 14 early patients with coronavirus disease 2019 in the United States. We isolated viable severe acute respiratory syndrome coronavirus 2 from real-time reverse-transcription polymerase chain reaction-positive respiratory specimens collected during days 0-8 after onset, but not after. All 13 patients with 2 or more serum specimens developed anti-spike antibodies; 12 developed detectable neutralizing antibodies. We did not isolate virus after detection of neutralizing antibodies. Eight participants provided serum at 6 months after onset; all retained detectable anti-spike immunoglobulin G, and half had detectable neutralizing antibodies. Two participants reported not feeling fully recovered at 6 months.
Subject(s)
Antibodies, Neutralizing/immunology , Antibodies, Viral/immunology , Antibody Formation/immunology , COVID-19/immunology , Seroconversion/physiology , Antibodies, Neutralizing/blood , Antibodies, Viral/blood , COVID-19/blood , COVID-19/virology , Follow-Up Studies , Humans , Immunoglobulin G/blood , Immunoglobulin G/immunology , Spike Glycoprotein, Coronavirus/immunology , United StatesABSTRACT
Cytokine-activated STAT proteins dimerize and bind to high-affinity motifs, and N-terminal domain-mediated oligomerization of dimers allows tetramer formation and binding to low-affinity tandem motifs, but the functions of dimers versus tetramers are unknown. We generated Stat5a-Stat5b double knockin (DKI) N-domain mutant mice in which STAT5 proteins form dimers but not tetramers, identified cytokine-regulated genes whose expression required STAT5 tetramers, and defined dimer versus tetramer consensus motifs. Whereas Stat5-deficient mice exhibited perinatal lethality, DKI mice were viable; thus, STAT5 dimers were sufficient for survival. Nevertheless, STAT5 DKI mice had fewer CD4(+)CD25(+) T cells, NK cells, and CD8(+) T cells, with impaired cytokine-induced and homeostatic proliferation of CD8(+) T cells. Moreover, DKI CD8(+) T cell proliferation after viral infection was diminished and DKI Treg cells did not efficiently control colitis. Thus, tetramerization of STAT5 is critical for cytokine responses and normal immune function, establishing a critical role for STAT5 tetramerization in vivo.
