Hand, foot, and mouth disease (HFMD) is a common illness in children. However, no effective vaccine or antiviral drug is yet available for HFMD. Coxsackievirus A16 (CVA16) and enterovirus 71(EV71) are two major etiological agents of HFMD [1, 10, 28]. The seroprevalence for individuals (ages≥1 year) was found to be nearly 60% for CVA16 and 40% for EV71 . In recent years, large outbreaks of EV71-associated HFMD in the Asia-Pacific region [3, 13, 25], often coupled with severe clinical manifestations, have drawn a lot of attention to this virus. In contrast, CVA16 appears to have drawn very little interest, probably due to its association with often mild and benign clinical symptoms. As such, very little information has been made available for CVA16. However, it has been observed the recombination between CVA16 and EV71 [32, 34], and the co-circulation of these two viruses may have contributed to the increase of HFMD cases in China over the past few years . Thus, for CVA16, further understanding of its virology, epidemiology and virus-host interactions and host pathogenesis is of importance.
CVA16 is described as one of the human enterovirus A species under the genus Enterovirus in the Picornaviridae family of viruses, which includes EV71 and poliovirus . The exact mechanism for CVA16 replication has been poorly understood and was often speculated based on studies on other picornaviruses. CVA16 virus particle first attaches to the host cell surface via cellular receptors (HSCARB2 and PSGL-1) [23, 29]before entering and uncoating to unveil the viral RNA genome. Viral RNA is translated by cellular translational machinery to give a polyprotein that is then cleaved by the virus-encoded proteases 2Apro and 3Cpro to give four structural (VP1-4) and seven non-structural (2A-C and 3A-D) individual proteins . Within virus-induced membrane vesicles, viral RNA (+) is copied by the viral RNA polymerase, 3Dpol, to give (-) strand RNA intermediates, which in turn provide the template for the synthesis of (+) strand viral RNA. The (+) strand viral RNAs are used to generate more (-) strand viral RNAs, which are translated into viral proteins or packaged into progeny virions. Lysis of host cells will result in the release of progeny virions into the cytoplasm, where it directly translates into a polyprotein .
Viral kinetic studies have elucidated the process of host-viral interactions in influenza A, hepatitis B and C, and cytomegalovirus infections [2, 8, 11, 21, 27]. These detailed viral studies have enabled investigators to examine the efficacy of antiviral compounds in limiting viral replication while assessing the development of resistance with resurgence in viral replication. In the Picornavirus family, the kinetics of poliovirus , Enterovirus 71  and Hepatitis A Virus (HAV)  have been described in several studies. However, little information is known about CVA16 infection. The objectives of the present investigation were to conduct a study on viral RNA replication, viral protein synthesis, packaging and secretion in rhabdomyosarcoma (RD) cells to achieve an understanding of the viral kinetics of CVA16.
Replication Kinetics of Coxsackievirus A16 in Human Rhabdomyosarcoma Cells *
- Received Date: 15 February 2012
- Accepted Date: 19 June 2012
Abstract: Coxsackievirus A16 (CVA16), together with enterovirus type 71 (EV71), is responsible for most cases of hand, foot and mouth disease (HFMD) worldwide. Recent findings suggest that the recombination between CVA16 and EV71, and the co-circulation of these two viruses may have contributed to the increase of HFMD cases in China over the past few years. It is therefore important to further understand the virology, epidemiology, virus-host interactions and host pathogenesis of CVA16. In this study, we describe the viral kinetics of CVA16 in human rhabdomyosarcoma (RD) cells by analyzing the cytopathic effect (CPE), viral RNA replication, viral protein expression, viral RNA package and viral particle secretion in RD cells. We show that CVA16 appears to first attach, uncoat and enter into the host cell after adsorption for 1 h. Later on, CVA16 undergoes rapid replication from 3 to 6 h at MOI 1 and until 9 h at MOI 0.1. At MOI 0.1, CVA16 initiates a secondary infection as the virions were secreted before 9 h p.i. CPE was observed after 12 h p.i., and viral antigen was first detected at 6 h p.i. at MOI 1 and at 9 h p.i. at MOI 0.1. Thus, our study provides important information for further investigation of CVA16 in order to better understand and ultimately control infections with this virus.