Dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) and liver/lymph node-specific intercellular adhesion molecules-3-grabbing non-integrin (L-SIGN) are calcium-dependent C-type lectin receptors (CLRs). Both proteins mediate the entrance of viruses by recognizing mannose or fructose oligosaccharides on the viral surface. However, potential regulation of DC-SIGN or L-SIGN on viral replication is neglected. In this study, we established murine cell lines stably expressing DC-SIGN, L-SIGN and their functional domain chimeras respectively, and analyzed the impacts of the expressed proteins on murine coronavirus replication. The results showed that L-SIGN had a more obviously inhibitory effect on viral replication than DC-SIGN, which was related to difference in the sequences. The inhibitory effect might act by antagonizing the downregulation of extracellular signal-regulated kinase (ERK) signaling pathway triggered by the virus. DC-SIGN was not found to directly mediate the entry of virus into receptor-unexpressed cell lines. The regulation of DC-SIGN and L-SIGN on the viral replication was dependent on the viral receptor mouse carcinoembryonic antigen-related cell adhesion molecule 1a (mCEACAM1a) which might interact with DC-SIGN trimer on the cell surface. These results suggest that CLR can regulate the viral replication through interference with signaling events even if they cannot mediate directly the entry of the virus.

A novel avian influenza A (H7N9) virus has caused epidemics during 2013 to 2014, and sporadic infections in 2015. To investigate the evolutionary history and seasonal variations of H7N9 in live poultry markets (LPMs), 2 655 pharyngeal swabs of chickens and ducks were collected from July to December 2013 in Suzhou, Jiangsu Province, China, which was one of the major epidemic areas in 2013. The results showed that the positive rate in winter was higher than that in summer and there were mixed infections among H5, H7, and H9 strains, suggesting the occurrence of multiple reassortment events. The HA, NA and PB2 genes from selected H7N9-positive samples were then sequenced to trace the evolutionary history of the novel H7N9 virus. Phylogenetic analysis revealed that all Suzhou isolates in this study were clustered around the novel H7N9 virus, but they also continued to evolve while circulating in the poultry. In fact, the PB2 gene of some sequenced samples was closely related to H5N1. This study identifies the genetic reassortment of a novel H7N9 virus in Suzhou and suggests that constant surveillance of all avian influenza virus subtypes in LPMs will help to track the source of newly emerging virulent viral strains.

The regulator of colanic acid capsule synthesis (Rcs) is a complicated two-component signal transduction system. Although details of Rcs in most Enterobacteria are known, its regulation in Shigella has not been reported yet. This study aims to explore the influences of environmental stresses on Rcs transcription in Shigella. Based on biological informatics analysis of RcsBDC in Shigella flexneri 2a 301, the transcriptional levels of rcsB, rcsD, rcsC at different growth stages were analyzed by real-time polymerase chain reaction (PCR), and the changes in the transcriptional levels of the three genes in acid and osmotic pressure conditions were examined. The transcriptional levels of the three genes were higher in 5－6 h (logarithmic phase), and lower in 8－10 h (stationary phase). The transcriptional levels of rcsB and rcsD in acid and osmotic pressure conditions were higher than in normal condition, suggesting environmental stimuli promote the transcriptional levels of rcsB and rcsD in Shigella flexneri during stationary phase.

The present paper aims to investigate the optimum amount of serum samples used to isolate exosomes by Qiagen exoRNeasy Serum/Plasma Midi Kit. Exosomes were isolated by Qiagen exoRNeasy Serum/Plasma Midi Kit from different gradient serum samples, including 250 μL, 500 μL, 1 000 μL. The particle size and morphology of exosomes were measured by transmission electron microscopy. The expressions of exosomal surface protein markers CD63 and TSG101 were determined by Western blotting. The expression of microRNA-122 (miR-122) in exosomes was detected by real-time fluorescent quantitative polymerase chain reaction (PCR). Serum exosomes were circular or elliptic under the transmission electron microscope with diameters of 30-150 nm and they had intact membrane structure. Western blotting results showed that CD63 and TSG101 were positive in exosomes. The real-time fluorescent quantitative PCR results showed that when the initial serum volume was 250 μL, 500 μL and 1 000 μL, the expression of miR-122 in chronic hepatitis B patients was up-regulated by 22.44 folds, 21.48 folds and 20.69 folds, respectively compared with controls (P＝0.42). It is suggested that a small amount of 250 μL serum could be used for isolation of exosomes by Qiagen exoRNeasy Serum/Plasma Midi Kit, when the clinical serum sample is limited.

Exosomes are endogenous nanoparticles secreted by cells in physiological or pathological state. It is a durably hot topic in research fields of pathology and drug carrier systems. In recent years, it has been found that exosomes can transfer viral components and virus-related immune molecules in human immunodeficiency virus type 1 (HIV-1) infection. The mechanisms of exosome-mediated HIV-1 infection are reviewed in the present paper.

Approximately 20% of human immunodeficiency virus (HIV)-infected patients do not achieve optimal CD4^＋ T cell recovery despite suppression of viral replication after antiretroviral (ART) treatment. These patients are referred to as immunological non-responders (INRs). However, the mechanisms involved are incompletely understood. This review summarizes the risk factors regarding the impaired immune reconstitution in HIV infection from the perspectives of clinical and immunological indicators. The speculated mechanisms of the failure of immune recovery may be the exhaustion of CD4^＋ T cells in peripheral circulation system, orchestration of cytokines and pyroptosis of CD4^＋ T cells at the gastrointestinal mucosal site. Specifically, microbial flora may contribute to the pyroptosis of CD4^＋ T cells at the intestinal mucosa-associated lymphoid tissue. Several clinical trials of additional treatment to ART that may improve immune reconstitution have been investigated but results thus far have proved disappointing because of the absence of medical evidence. Thus, prospective cohort study of larger samples should be conducted in future to define INRs, elucidate mechanisms and support clinical practice.

Tuberculosis is a global health concern. Cell-mediated immunity plays important roles against the infection. Several types of immune cells and cytokines play key roles in the pathogenesis, development and prognosis of tuberculosis through a variety of mechanisms. Neutrophils participate in constituting the first line of defense to Mycobacterium tuberculosis (M. tuberculosis). Neutrophils gather at the infection site rapidly after infection, and play the roles of anti-tuberculosis immunity through various mechanisms, such as phagocytosis, apoptosis, granuloma formation, neutrophil extracellular traps and producing effector cytokines. In addition, neutrophils also participate in the tissue injury process in tuberculosis patients. The recent research progress on the functions of neutrophils and some cytokines related to the immune response to tuberculosis is summarized.