Oligosymptomatic long-term carriers of SARS-CoV-2 display impaired innate resistance but increased high-affinity anti-spike antibodies.

The vast spectrum of clinical features of COVID-19 keeps challenging scientists and clinicians. Low resistance to infection might result in long-term viral persistence, but the underlying mechanisms remain unclear. Here, we studied the immune response of immunocompetent COVID-19 patients with prolonged SARS-CoV-2 infection by immunophenotyping, cytokine and serological analysis. Despite viral loads and symptoms comparable to regular mildly symptomatic patients, long-term carriers displayed weaker systemic IFN-I responses and fewer circulating pDCs and NK cells at disease onset. Type 1 cytokines remained low, while type-3 cytokines were in turn enhanced. Of interest, we observed no defects in antigen-specific cytotoxic T cell responses, and circulating antibodies displayed higher affinity against different variants of SARS-CoV-2 Spike protein in these patients. The identification of distinct immune responses in long-term carriers adds up to our understanding of essential host protective mechanisms to ensure tissue damage control despite prolonged viral infection.

MIF is essential to the establishment of house dust mite-induced airway inflammation and tissue remodeling in mice.

Macrophage migration inhibitory factor (MIF) is present in high amounts in the BALF and serum of asthmatic patients, contributing to the pathogenesis of experimental asthma induced by OVA in mice. Whether MIF contributes to the physiopathology on a more complex and relevant asthma model has not been characterized. Mif-deficient (Mif-/- ) or WT mice treated with anti-MIF antibody were challenged multiple times using house dust mite (HDM) extract by the intranasal route. HDM-challenged Mif-/- mice presented decreased airway hyperresponsiveness, lung infiltration of eosinophils, mucus hypersecretion, and subepithelial fibrosis compared to HDM-challenged WT mice. Amounts of IL-4, IL-5, and IL-13 were decreased in the lungs of Mif-/- mice upon HDM challenges, but the increase of CCL11 was preserved, compared to HDM-challenged WT mice. We also observed increased numbers of group 2 innate lymphoid cells and Th2 cells in the BALF and mediastinal LNs (mLN)-induced challenged by HDM of WT mice, but not in HDM-challenged Mif-/- mice. Anti-MIF treatment abrogated the airway infiltration of eosinophils, mucus hypersecretion, and subepithelial fibrosis in the lungs of HDM-challenged mice. In conclusion, MIF ablation prevents the pathologic hallmarks of asthma in HDM-challenged mice, reinforcing the promising target of MIF for asthma therapy.

Dynamics of Reverse Transcription-Polymerase Chain Reaction and Serologic Test Results in Children with SARS-CoV-2 Infection.

OBJECTIVES: To determine the time to reverse transcription-polymerase chain reaction (RT-PCR) negativity after the first positive RT-PCR test, factors associated with longer time to RT-PCR negativity, proportion of children seroconverting after proven severe acute respiratory syndrome coronavirus 2 infection, and factors associated with the lack of seroconversion. STUDY DESIGN: The Epidemiological Study of Coronavirus in Children of the Spanish Society of Pediatrics is a multicenter study conducted in Spanish children to assess the characteristics of coronavirus disease 2019. In a subset of patients, 3 serial RT-PCR tests on nasopharyngeal swab specimens were performed after the first RT-PCR test, and immunoglobulin G serology for severe acute respiratory syndrome coronavirus 2 antibodies was performed in the acute and follow-up (<14 and ≥14 days after diagnosis) phase. RESULTS: In total, 324 patients were included in the study. The median time to RT-PCR negativity was 17 days (IQR, 8-29 days), and 35% of patients remained positive more than 4 weeks after the first RT-PCR test. The probability of RT-PCR negativity did not differ across groups defined by sex, disease severity, immunosuppressive drugs, or clinical phenotype. Globally, 24% of children failed to seroconvert after infection. Seroconversion was associated with hospitalization, persistence of RT-PCR positivity, and days of fever. CONCLUSIONS: Time to RT-PCR negativity was long, regardless of the severity of symptoms or other patient features. This finding should be considered when interpreting RT-PCR results in a child with symptoms, especially those with mild symptoms. Seroprevalence and postimmunization studies should consider that 11 in 4 infected children fail to seroconvert.