Pulmonary function impairment of asymptomatic and persistently symptomatic patients 4 months after COVID-19 according to disease severity

Objective

Evaluation of pulmonary function impairment after COVID-19 in persistently symptomatic and asymptomatic patients of all disease severities and characterisation of risk factors.

Methods

Patients with confirmed SARS-CoV-2 infection underwent prospective follow-up with pulmonary function testing and blood gas analysis during steady-state cycle exercise 4 months after acute illness. Pulmonary function impairment (PFI) was defined as reduction below 80% predicted of DLCOcSB, TLC, FVC, or FEV1. Clinical data were analyzed to identify risk factors for impaired pulmonary function.

Results

76 patients were included, hereof 35 outpatients with mild disease and 41 patients hospitalized due to COVID-19. Sixteen patients had critical disease requiring mechanical ventilation, 25 patients had moderate–severe disease. After 4 months, 44 patients reported persisting respiratory symptoms. Significant PFI was prevalent in 40 patients (52.6%) occurring among all disease severities. The most common cause for PFI was reduced DLCOcSB (n = 39, 51.3%), followed by reduced TLC and FVC. The severity of PFI was significantly associated with mechanical ventilation (p < 0.001). Further risk factors for DLCO impairment were COPD (p < 0.001), SARS-CoV-2 antibody-Titer (p = 0.014) and in hospitalized patients CT score. A decrease of paO2 > 3 mmHg during cycle exercise occurred in 1/5 of patients after mild disease course.

Conclusion

We characterized pulmonary function impairment in asymptomatic and persistently symptomatic patients of different severity groups of COVID-19 and identified further risk factors associated with persistently decreased pulmonary function. Remarkably, gas exchange abnormalities were revealed upon cycle exercise in some patients with mild disease courses and no preexisting pulmonary condition.

Supplementary Information

The online version contains supplementary material available at 10.1007/s15010-021-01669-8.

Profound phenotype alteration and delayed regeneration of circulating antigen presenting cells in COVID-19

Disease manifestations in COVID-19 range from mild symptoms to severe/critical illness with lung inflammation, hypercoagulation and cardiovascular complications, which may be caused by a dysregulated innate immune response. Antigen presenting cells may contribute to the inflammatory response and shape the adaptive immune response in COVID-19 patients. We therefore investigated the frequency and phenotype of circulating dendritic cells (DCs) and monocytes in hospitalized COVID-19 patients with mild/moderate or severe disease at different time points (n=65). We found an overall reduction of DCs and a shift towards the CD14+ DC3 population within the DCs in patients vs. controls.

In patients with more severe disease, we observed upregulation of CXCR3, CCR2, CD40 and PD-L1, but reduced expression of CD86 and HLADR in monocytes and conventional DCs (cDCs) within the first 3 weeks after diagnosis (n=26). Increased proliferation and expansion of precursor cells in the blood indicated an enhanced turnover that was observed even in convalescent patients. Proliferating cDC2 and DC3 showed a phenotype similar to that found in healthy controls suggesting that the phenotype alterations are induced in differentiated DCs by external factors. The observed changes were accompanied by increased inflammatory cytokine levels in the plasma and lymphopenia.

Thus, in more severe COVID-19 circulating cDCs and monocytes exhibited a profoundly altered expression of costimulatory molecules and were poised to exit the blood in response to inflammatory chemokines. Increased proliferation even after recovery indicated delayed regeneration of the mononuclear phagocyte system.

SERINC5 Is an Unconventional HIV Restriction Factor That Is Upregulated during Myeloid Cell Differentiation

Classical antiviral restriction factors promote cellular immunity by their ability to interfere with virus replication and induction of their expression by proinflammatory cytokines such as interferons. The serine incorporator proteins SERINC3 and SERINC5 potently reduce the infectivity of HIV-1 particles when overexpressed, and RNA interference or knockout approaches in T cells have indicated antiviral activity also of the endogenous proteins. Due to lack of reagents for detection of endogenous SERINC proteins, it is still unclear whether SERINC3/5 are expressed to functionally relevant levels in different primary target cells of HIV infection and how the expression levels of these innate immunity factors are regulated. In the current study, analysis of SERINC3/5 mRNA steady-state levels in primary lymphoid and monocyte-derived cells revealed selective induction of their expression upon differentiation of myeloid cells. Contrary to classical antiviral restriction factors, various antiviral α-interferon subtypes and proinflammatory interleukins had no effect on SERINC levels, which were also not dysregulated in CD4+ T cells and monocytes isolated from patients with chronic HIV-1 infection. Notably, HIV-1 particles produced by terminally differentiated monocyte-derived macrophages with high SERINC5 expression, but not by low-expressing monocytes, showed a Nef-dependent infectivity defect. Overall, these findings suggest endogenous expression of SERINC5 to antivirally active levels in macrophages. Our results classify SERINC5 as an unconventional HIV-1 restriction factor whose expression is specifically induced upon differentiation of cells towards the myeloid lineage.