Low frequency, weak MCP-1 secretion and exhausted immune status of peripheral monocytes were associated with progression of severe enterovirus A71-infected hand, foot and mouth disease

Low-frequency, exhausted immune status of CD56dim NK cells and disordered inflammatory cytokine secretion of CD56bright NK cells associated with progression of severe HFMD, especially in EV71-infected patients

BACKGROUND

The roles of CD56^bright and CD56^dim natural killer (NK) subsets in the viral clearance and inflammatory processes of hand, foot, and mouth disease (HFMD) remain undefined.

METHODS

A total of 39 HCs and 55 patients were enrolled to analyze peripheral CD56^bright and CD56^dim NK cells according to cell number, surface receptors, cytotoxic activities, and cytokine production. The plasma concentrations of IL-2, IL-6, IL-10, IFN-γ, TNF-α,and MCP-1 were detected using ELSA.

RESULTS

Peripheral blood NK cells was significantly lower in severe patients than in HCs due to the dramatic loss of CD56^dim NK cells with no changes in the cell count of CD56^bright NK cells. For mild patients, decreased NKp46 expression coincided with enhanced cytolysis (CD107a, GNLY, and GrB) in CD56^dim NK cells and decreased NKG2A expression with enhanced IL-10 production in CD56^bright NK cells. In contrast, severe patients showed the dominant expression of NKG2A and decreased expression of NKG2D accompanied by cytotoxic dysfunction in CD56^dim NK cells. Imbalanced receptor expression coincided with the increased concentrations of TNF-α in CD56^bright NK cells. Moreover, EV71+ patients showed significantly decreased counts of CD56^dim NK cells with cytolysis dysfunction, displayed cytokine hypersecretion in CD56^bright NK cells, while the EV71- patients displayed significantly higher plasma cytokine concentrations. The changes in the immune function of NK subsets and their subpopulations were closely related to clinical inflammatory parameters.

CONCLUSIONS

Low-frequency, exhausted immune status of CD56^dim NK cells and disordered inflammatory cytokine secretion of CD56^bright NK cells were associated with the progression of severe HFMD, especially in EV71-infected patients. This promoted the severity of inflammatory disorders, leading to enhanced disease pathogenesis.

Duck-origin H5N6 avian influenza viruses induce different pathogenic and inflammatory effects in mice

Since 2013, H5N6 highly pathogenic avian influenza viruses have caused considerable economic losses in the poultry industry and have caused 24 laboratory-confirmed human cases. In this study, we isolated nine (B1-B9) H5N6 viruses from healthy ducks in Guangdong Province, Southern China from December 2018 to April 2019. Phylogenetic analysis revealed that B1, B2, B3, B4, B5, B7, B8, and B9 clustered into the G1.1 genotype and shared high sequence similarity with human H5N6 isolates from Southern China in 2017 and 2018. Meanwhile, B6 clustered into the G1.1.9 genotype. The hemagglutinin (HA), neuraminidase (NA) and nonstructural protein (NS) gene segments of B6 were closely related to the human H5N6 isolates, while the other genomic segments were closely related to H5N6 viruses isolated from waterfowl in Southern China. Compared to B7, B6 had higher pathogenicity and induced stronger inflammatory responses in mice. B6 carried a full-length PB1-F2 protein (90 aa), while the rest carried an 11-amino acid C-terminal-truncated PB1-F2. The PB1-F2 protein may increase the virulence of B6 compared to that of B7. Our findings provide insight into the pathogenic mechanisms of H5N6 viruses in mammals and emphasize the need for continued surveillance of circulating H5N6 viruses in ducks.

Response of Severe EV71-Infected Patients to Hyperimmune Plasma Treatment: A Pilot Study

Hand, foot, and mouth disease (HFMD) is highly prevalent in East and Southeast Asia. It particularly affects children under five years of age. The most common causative agents are coxsackieviruses A6 and A16, and enterovirus A71 (EV71). The clinical presentation is usually mild and self-limited, but, in some cases, severe and fatal complications develop. To date, no specific therapy or worldwide vaccine is available. In general, viral infection invokes both antibody and cell-mediated immune responses. Passive immunity transfer can ameliorate the severe symptoms of diseases such as COVID-19, influenza, MERS, and SARS. Hyperimmune plasma (HIP) from healthy donors with high anti-EV71 neutralizing titer were used to transfuse confirmed EV71-infected children with neurological involvement (n = 6). It resulted in recovery within three days, with no neurological sequelae apparent upon examination 14 days later. Following HIP treatment, plasma chemokines were decreased, whereas anti-inflammatory and pro-inflammatory cytokines gradually increased. Interestingly, IL-6 and G-CSF levels in cerebrospinal fluid declined sharply within three days. These findings indicate that HIP has therapeutic potential for HFMD with neurological complications. However, given the small number of patients who have been treated, a larger cohort study should be undertaken. Successful outcomes would stimulate the development of anti-EV71 monoclonal antibody therapy.