Inhibition of HSP90 attenuates porcine reproductive and respiratory syndrome virus production in vitro.
BACKGROUND
Porcine reproductive and respiratory syndrome virus (PRRSV) infection leads to substantial economic losses to the swine industry worldwide. However, no effective countermeasures exist to combat this virus infection so far. The most common antiviral strategy relies on directly inhibiting viral proteins. However, this strategy invariably leads to the emergence of drug resistance due to the error-prone nature of viral ploymerase. Targeting cellular proteins required for viral infection for developing new generation of antivirals is gaining concern. Recently, heat shock protein 90 (HSP90) was found to be an important host factor for the replication of multiple viruses and the inhibition of HSP90 showed significant antiviral effects. It is thought that the inhibition of HSP90 could be a promising broad-range antiviral approach. However, the effects of HSP90 inhibition on PRRSV infection have not been evaluated. In the current research, we tried to inhibit HSP90 and test whether the inhibition affect PRRSV infection.


METHODS
We inhibit the function of HSP90 with two inhibitors, geldanamycin (GA) and 17- allylamono-demethoxygeldanamycin (17-AAG), and down-regulated the expression of endogenous HSP90 with specific small-interfering RNAs (siRNAs). Cell viability was measured with alamarBlue. The protein level of viral N was determined by western blotting and indirect immunofluorescence (IFA). Besides, IFA was employed to examine the level of viral double-stranded RNA (dsRNA). The viral RNA copy number and the level of IFN-β mRNA were determined by quantitative real-time PCR (qRT-PCR).


RESULTS
Our results indicated that both HSP90 inhibitors showed strong anti-PRRSV activity. They could reduce viral production by preventing the viral RNA synthesis. These inhibitory effects were not due to the activation of innate interferon response. In addition, we observed that individual knockdown targeting HSP90α or HSP90β did not show dramatic inhibitory effect. Combined knockdown of these two isoforms was required to reduce viral infection.


CONCLUSIONS
Our results shed light on the possibility of developing potential therapeutics targeting HSP90 against PRRSV infection.
Jintao
J
Gao
Shuqi
S
Xiao
Xiaohong
X
Liu
Liangliang
L
Wang
Xiaoyu
X
Zhang
Qianqian
Q
Ji
Yue
Y
Wang
Delin
D
Mo
State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, PR China. chyaosh@mail.sysu.edu.cn.
Yaosheng
Y
Chen
D000818:Animals; D016227:Benzoquinones / Q000378:metabolism; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D019084:Fluorescent Antibody Technique, Indirect; D055785:Gene Knockdown Techniques; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D047029:Lactams, Macrocyclic / Q000378:metabolism; D019316:Porcine respiratory and reproductive syndrome virus / Q000502:physiology*; D012367:RNA, Viral / Q000032:analysis; D060888:Real-Time Polymerase Chain Reaction; D013552:Swine; D014764:Viral Proteins / Q000032:analysis; D014779:Virus Replication
D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D012367:RNA, Viral; D014764:Viral Proteins; C112765:tanespimycin; C001277:geldanamycin