Hepatitis C virus impairs natural killer cell-mediated augmentation of complement synthesis
Authors: Hangeun Kim
Keith Meyer
Sandip K Bose
Ranjit Ray
Journal: Journal of Virology (2014)
Discipline: MICROBIOLOGY
Keywords: NK cells; complement system; hepatitis C virus; HCV; core protein

Abstract:  Natural killer (NK) cells and the complement system play critical roles in the first line of defense against pathogens. The synthesis of complement components C4 and C3 is transcriptionally downregulated by hepatitis C virus (HCV) core and NS5A proteins, and this negative regulation is apparent in chronically HCV-infected patients. In this study, we have examined the potential contribution of an NK cell line as a model in regulating complement synthesis. Coculture of NK cells (NK3.3) with human hepatoma cells (Huh7.5) expressing HCV core or NS5A protein led to a significant increase in C4 and C3 complement synthesis via enhanced specific transcription factors. Reestablishment of complement protein expression was found to be mediated by direct interaction between NKG2D on NK cells and the hepatocyte protein major histocompatibility complex class I-related chains A and B (MICA/B) and not to be associated with specific cytokine signaling events. On the other hand, C4 and C3 synthesis remained impaired in a coculture of NK cells and Huh7.5 cells infected with cell culture-grown HCV. The association between these two cell types through NKG2D and MICA/B was examined further, with MICA/B expression in HCV-infected hepatocytes found to remain inhibited during coculture. Further experiments revealed that the HCV NS2 and NS5B proteins are responsible for the HCV-associated decrease in MICA/B. These results suggest that HCV disables a key receptor ligand in infected hepatoma cells, thereby inhibiting the ability of infected cells to respond to stimuli from NK cells to positively regulate complement synthesis. Importance: The complement system contributes to the protection of the host from virus infection. However, the involvement of complement in viral hepatitis has not been well documented. Whether NK cells affect complement component expression in HCV-infected hepatocytes remains unknown. Here, we have shown how HCV subverts the ability of NK cells to positively mediate complement protein expression. 

Retracted: No

PubPeer comments:
 December 2017 author correction reads:  Volume 88, no. 5, p. 2564u20132571, 2014, [doi: 10.1128 JVI.02988-13] . * Page 2566, Fig. 1B: The Control blot for the C4 row was a duplicate of the Huh7.5+IL-2 blot for the C4 row in panel A because of an inadvertent error during figure assembly. We have remade Fig. 1B with new C4 and Actin rows with Control and NKCM-treated cells, using a duplicate set of these experiments. * Page 2566, Fig. 1A: We have replaced the Huh7.5+NK+IL-2 C4 and Actin rows with a new data set generated under similar conditions to avoid confusion with the Huh7.5+NK+IL-2 C4 and Actin rows in Fig. 2A, which were used as a control. I have included both the original and corrected images here, and highlighted the corrected portions in yellow. Although the correction does address the issues indicated in the orange and purple boxes, I still have some concerns about these figures. - Pink boxes: C4 row in Fig. 2A is unexpectedly similar to Actin row in Fig. 1C when rotated 180 degrees and stretched. - Blue boxes: Actin row in Fig. 1A for Huh7.5+NK w o IL-2 cells looks similar to Actin row in Fig. 2A for Huh7.5+NK+IL-2 cells - Green boxes: Actin rows in Fig. 2A and 2B for Huh7.5+NK+IL-2+a-MICA B cells appear to be similar which may not be an issue as long as the target proteins were all probed on the same blot - However, Actin row in Fig. 2B for Huh7.5 cells should be a separate control, but it shares similar features with the other green boxes ![file] , 
 Thanks for your interest and criticisms. I do not agree with the similarities of the bands you observed. , 
 Thank you for your response. My first image is very busy so I have created a new one with the bands of interest isolated ![file] ,