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*Corresponding author: E-mail: collinsoguh@gmail.com; 
 
 
 

Asian Journal of Immunology 
 
3(1): 145-159, 2020; Article no.AJI.56272 
 

 
 

 

 

Structure and Function of COVID-19 Encode 
Proteins in the Transcription and Replication 
Mechanism with Its Preventive Measures and 

Propose Efficacy Treatments: A Critical  
Systematic Review 

 
Oguh C. E.1*, Obiwulu E. N. O.2, Oniwon W. O.3, Okekeaji U.4, Ugwu C. V.1, 

Umezinwa O. J.5 and Osuji C. A.1 

 
1
Department of Biochemistry, University of Nigeria, Nsukka, Enugu State, Nigeria. 

2
Department of Integrated Science, Delta State College of Education, Agbor, Delta State, Nigeria. 

3
Department of Biochemistry, Kogi State University, Anyigba, Nigeria. 

4
Department of Pharmaceutical Microbiology and Biotechnology, University of Nigeria, Nsukka,  

Enugu State, Nigeria. 
5
Department of Science Laboratory Technology, University of Nigeria, Nsukka, Enugu State, Nigeria. 

 
Authors’ contributions 

 
This work was carried out in collaboration among all authors. Author OCE designed the study, wrote 

the protocol and manage the analyses of the study. Author OENO wrote the first draft of the 
manuscript. Authors OWO, OU, UCV and UOJ managed the literature searches. Author OCA read 

and edit the final manuscript. All authors read and approved the final manuscript. 
 

Article Information 
 

Editor(s): 
(1) Dr. Cynthia Aracely Alvizo Báez, Autonomous University of Nuevo Leon, Mexico. 

Reviewers: 
(1) Loc Nguyen, Vietnam. 

(2) Lívia Garcia Bertolacci-Rocha, Universidade Federal de Goiás, Brasil. 
(3) Mujeeb Shittu, Michigan Technological University, USA. 

Complete Peer review History: http://www.sdiarticle4.com/review-history/56272 
 
 
 
 

Received 03 April 2020  
Accepted 25 April 2020 
Published 02 May 2020 

 
 

ABSTRACT 
 

The sudden occurrence outbreak of coronavirus disease in 2019 (COVID-19) by the severe acute 
respiratory syndrome coronavirus2 (SARS-CoV-2) poses a serious harm worldwide and local 
economies. Due to high numbers of infection and death, the pandemic calls for an urgent demand 
of active, effective, affordable and available drugs to control and diminish the pandemic.  
Coronavirus disease 2019 is a public health unexpected and sudden crisis which required action of 

Review Article 



 
 
 
 

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international concern. At present there is no generally recognized effective pharmaceutical 
treatment to the disease, although it is to a great extent for patient contracting the severe form of 
the disease. The development of new strategies to prevent or control the spread of COVID-19 
infections and the understanding of the virus replication, and pathogenesis required immediate 
action. Therefore, this systematic review was to investigate the biochemical effect of the virus in 
human, symptoms, prevention, statistics cases and summarize the evidence regarding chloroquine 
and hydroxychloroquine for the treatment of COVID-19. 

 

 
Keywords: Coronavirus; mechanism; prevention; structure; treatment. 
 

ABBREVIATIONS 
 
COVID-19: Coronavirus disease 2019;                   
SARS-CoV2: Severe acute respiratory syndrome 
coronavirus 2; S: Spike;  M: Membrane;                      
E: Envelope glycoproteins; HE: Hemagglutinin 
Esterase: N: Nucleocapsid protein; RdRp: RNA-
dependent RNA polymerase; MHV: Mouse 
hepatitis virus; ACE2: Angiotensin-converting 
enzyme 2; 3CLpro: Coronavirus main protease; 
PLpro: Papain-like protease; FECV: Feline 
Enteric Coronavirus; FIPV: Feline Infectious 
Peritonitis Virus; TGEV: Transmissible Gastro- 
Enteritis Virus; PEDV: Porcine Epidemic 
Diarrhea Virus;  PRCoV: Porcine Respiratory 
Coronavirus; CCoV: Canine coronavirus; BCoV: 
Bovine Coronavirus;  gRNA: RNA genome; DMV: 
Double-Membrane Vesicles; RTC: Replication 
and Transcription Complex; nsp3: non-structural 
protein3; CQ: Chloroquine; HCQ: Hydroxy-
chloroquine; EEs: Early endosomes; ELs: endo-
lysosomes; Cryo - EM: Cryo electron 
microscopy; IFA: Immune fluorescence analysis; 
ERGIC: Endoplasmic reticulum-Golgi apparatus 
intermediate compartment. 
 

1. INTRODUCTION 
 

Coronavirus is a novel disease that had not been 
previously identified in human of recent. 
Coronavirus disease 2019 is a respiratory 
disease illness that is transitive from one 
individual to the other. The type of virus that 
causes COVID-19 is a new inventive disease 
that was firstly recognize during a survey 
outbreak in December. 2019 at Wuhan, China, 
this disease has spread to more than 213 
countries with 2,931,787 confirmed cases and 
over 203,596 confirmed deaths worldwide as of 
April 26, 2020 [1] with U.S, Spain, Italy and 
France as the most affected countries with 
960,896, 223,759, 195,351 and 161,488 confirm 
cases respectively. The name coronavirus, 
coined in 1968, is derived from the corona-like or 
crown-like morphology observed for these 
viruses in the electron microscope. The virus is 

highly contagious and thousands of new cases 
are reported around the world every day. The 
risk of infection from the virus that causes 
COVID-19 is higher for people who have close 
contacts with people with the disease, such as 
healthcare workers and household members and 
other people at higher risk for this infection are 
those who are living in an area with ongoing 
spread of COVID-19 or those who traveled to 
effected place. Risk of death is only higher in 
older people (above an age of 60 years) and 
people with pre-existing health conditions. 
Coronaviruses infect both animals and humans, 
especially animals such as bats, this animal host 
the largest variety of corona viruses shows to be 
immune to corona virus-induced illness in human 
[2]. Researchers have been working to trace the 
achievable treatments in order to save lives and 
produce vaccines for future prevention and 
control. The viruses infect a variety of organisms 
such as human and animal host cells, and also 
carry out their infection and replication on the 
host. Also, many proteins located on the virus 
have most important function in the replication 
mechanism, although the role is yet to be 
defined. In this case, it is important to investigate 
the role and importance of these proteins during 
mechanism. Therefore; this review explains the 
structure, classification, symptoms, prevention, 
statistics cases and summarize the evidence 
regarding chloroquine and hydroxychloroquine 
for the treatment of COVID-19. 
 

1.1 Structure of Covid-19 
 

Coronaviruses are enveloped viruses with round 
and sometimes pleiomorphic virions of 
approximately 80 to 120 nm in diameter (Fig. 1). 
The coronaviruses also contain positive-strand 
RNA, which have the largest RNA genome 
(approximately 30 kb) reported to date (178, 
196). Corona viruses (COVID-19) are mainly 
large viruses containing a single-stranded 
positive-sense RNA genome protected by 
membrane within a membrane envelope within 
the virus. The viral membrane is covered with 



 
 
 
 

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glycoprotein spikes that give coronaviruses their 
crown like appearance. COVID-19 virus encode 
five structural proteins in their genomes. These 
are the Spike (S), Membrane (M), Envelope (E) 
glycoproteins, Hemagglutinin Esterase HE and 
Nucleocapsid N protein, (Fig. 1). The virus 
envelope proteins and N protein is embedded in 
all virion but HE is only present in some beta 
coronaviruses. In addition to that, it is thought the 
virus particles are huddled together owing to 
interaction between these proteins [3,4]. 
 

1. S Glycoproteins: They are located outside 
the virion which gives the virion the typical 
shape. The S proteins form homotrimers, 
which allow the formation of sun-like 
morphologies that give the name of 
Coronaviruses [5]. S proteins bind to the 
virion membrane via the C-terminal 
transmembrane regions, also they interact 
with M proteins [6]. The Virions is attach to a 
specific surface receptors in the plasma 
membrane of the host cell through the N-
terminus of the S proteins. This S 
glycoprotein initiate host cell invasion by 
both SARS-CoV and SARS-CoV-2 via 
binding to a receptor protein called 
angiotensin-converting enzyme 2 (ACE2) 
which is located on the surface membrane 
of host cells [7,8]. A study conducted by [9, 
10], shows that the invasion process 
requires S protein priming which is 
accompany by the host cell produced serine 
protease. Also the viral genome also 
encodes several nonstructural proteins 
which include the RNA-dependent RNA 
polymerase (RdRp), coronavirus main 
protease (3CLpro) and papain-like protease 
(PLpro) [9,10].  

2. M Glycoproteins: The M Glycoproteins on 
the virus have three transmembrane 
regions. The proteins are glycosylated in the 
organelle called Golgi apparatus [11]. This 
reformation of the M protein is important for 
the virion to fuse into the cell and to make 
protein antigenic. The M protein plays a key 
important role in stimulate virions in the cell. 
The virus N protein also forms a complex by 
binding to genomic RNA and the M protein 
elicit the production and formation of 
interacting virions in this endoplasmic 
reticulum-Golgi apparatus intermediate 
compartment (ERGIC) with this complex 
[12,13]. 

3. E Glycoproteins: This are small proteins 
that are constitute of just about 76 to 109 
different amino acids. Approximately 30 

different amino acids in the N-terminus of 
the E proteins permit attachment to the 
membrane of viruses [14]. In addition, 
coronavirus E proteins play a critical 
important role in pulling together and 
morphogenesis of virions within the cell. A 
study of coronavirus E and M proteins were 
expressed together with mammalian 
expression vectors to form virus-like 
structures within the cell [15]. In a study, 
there was a great decrease in the ability of 
the recombinant mouse hepatitis virus 
(MHV) and SARS viruses to elicit E protein 
expression in the genome to support this 
status [16,17]. 

4. N Proteins: They are phosphor proteins 
that are capable of binding to helix and have 
elastic structure of viral genomic RNA. It 
plays a crucial role in virion structure, 
replication and transcription of 
coronaviruses, because the N protein focus 
in both the replication and the transcriptional 
region of the coronaviruses and the ERGIC 
area where the virus is collected [16,17]. 
(Fig. 2).  

 
1.2 Classification of Coronaviruses 
 
The classification of Coronaviruses is based on 
genomic organization, resemblance in genomic 
sequence, antigenic properties of viral proteins, 
replication strategies and structural character-
istics of virions, pathogenic, cytopathogenic and 
physicochemical properties [18]. The 
Coronaviruses are species of virus belonging to 
the Nidovirales order, which comprises 
Coronaviridae, Arteriviridae, Roniviridae and 
Mesoniviridae families [19]. The Arteviridae 
family consist of swine and equine pathogens, 
and the Roniviridae family is composed of 
invertebrate viruses. The Coronaviridae family is 
the largest among the four families, range from 
26 to 32 kb by its genomic sizes of coronaviridae 
[20]. Coronaviridae virus family subdivided into 
two subfamilies, coronavirinae and torovirinae. 
Coronavirinaeis gulf into four genera, Alpha 
coronavirus, Beta coronavirus, Gamma 
coronavirus and Delta coronavirus (Fig. 3). Alpha 
coronaviruses type 1 species are classified into 
the porcine TGEV (Transmissible Gastro- 
Enteritis Virus), feline FCoV, FECV (Feline 
Enteric Coronavirus) and FIPV (Feline Infectious 
Peritonitis Virus), Porcine PEDV (Epidemic 
Diarrhea Virus), PRCoV (Porcine Respiratory 
Coronavirus) and the canine CCoV. Alpha 
coronaviruses also agree with human CoVs such 



 
 
 
 

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as HCoV-229E and HCoVNL63, but various bat 
Coronaviruses.  
 
Beta coronaviruses infect a wide varieties of 
mammalians, with species such as human with 
SARS-CoV, mice, HCoV-OC43, HCoV-HKU1, 
and MERS-CoV, Bovine Coronavirus (BCoV), 
and Murine coronavirus (MHV). Likewise to 
SARS-CoV and MERS-CoV, SARS-CoV-2 
violence the lower respiratory system to cause 
viral pneumonia in human, and may also affect 
the heart, kidney, gastrointestinal system, liver, 
and central nervous system leading to multiple 

organ failure [21,22]. Current information 
indicates that SARSCoV-2 is more transmissible 
and very contagious than SARS-CoV [23].The 
beta coronavirus genome encrypt more than a 
few or several structural proteins, including the 
glycosylated spike (S) protein that functions as a 
major inducer of host immune responses. 
Gamma coronaviruses are exact of birds, with 
one exclusion of a beluga whale Coronavirus. 
The delta coronavirus genus was generated in 
2012 and with various groups (HKU11, HKU12, 
HKU13) Coronavirus from mammals to birds [24] 
Fig. 3. 

 

 
 
Fig. 1. Coronavirus virion. (A) Electron micrograph of mouse hepatitis virus MHV particles. 

(B) Schematic of virion 
 

 
 

Fig. 2. Cartoon illustration of the coronavirus structure and viral receptor ACE2 on the host 
cell surface 



 
 
 
 

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Fig. 3. Classification of Covid-19 
 

2. COVID-19 MECHANISM OF ACTION 
(REPLICATION AND TRANSCRIPTION) 

 
Coronavirus entry starts with the S protein 
binding to a target receptor on the cell surface, 
where after fusion is mediated at the cell 
membrane, delivering the viral nucleocapsid 
inside the cell for subsequent replication. The 
action of coronaviruses replication occurs in the 
cytoplasm of the host cell. The viruses mainly 
bind to the host receptor cell surface through the 
spike (S) protein. A conformational structure 
occurs in the structure and the process of entry 
into the virus cell start when S protein is bound to 
the receptor [25]. This process with endocytosis 
is reliant of pH through the receptor. The virus 
particle releases the RNA genome after going 
into the cytoplasm. This genome is a non-
segmented RNA virus with the largest known 
RNA genome (gRNA), single-stranded, which is 
approximately 26-32 kb. The genome consists of 
seven several genes. It is prearranged into 5’ 
non-structural protein coding regions include the 
replicase genes (gene 1), which are two-thirds of 
the genome, and 3’ structural and nonessential 
accessory protein coding regions including the 
gene 2-7 [26]. The replicase gene 1 products are 
encoded two very large open reading frames 
ORF1a and 1b, which are interpreted or 
translated into two large polypeptides pp1a and 
pp1b, which are produce and synthesized 
directly from the 5’ two-thirds of the genomic 
RNA of CoV (Fig. 4).  
 
After the protein have been synthesized, which is 
made up of 16 units, non-structural protein (nsp1 
to nsp16) is change with the influence of viral 

proteases pp1a and pp1b [27]. Same time, the 
Double-Membrane Vesicles (DMV) is virus 
Replication and Transcription Complex (RTC) 
[28,29]. The 16 unit’s proteins form DMV. These 
nsp proteins, particularly non-structural protein3 
(nsp3), have an important function in the virion 
structure, and the replication and transcription of 
CoV [30,31]. Genes 2 to 7 are transform from 
sub genomic mRNA. Sub genomics RNAs 
encode the main viral Envelope protein (E), 
structural proteins (S), Membrane protein (M), 
Nucleocapsid protein (N), and the accessory 
proteins, which are vital for virus-cell receptor 
binding. The recently structural synthesized 
proteins are released into the endoplasmic 
reticulum. All of these proteins, along with the N 
protein, are connected to the viral genomic RNA 
and localized in the ERGIC region [28,32] as 
shown in Fig. 4.  
 
Although, N protein is known to be very essential 
for coronavirus replication, the exact function or 
role that this protein plays in this process 
remains unidentified. But, several research 
suggested that N protein interact with nsp3, 
which plays a critical and important role in the 
virus replication early in infection. The 
communication between viral S protein and 
Angiotensin-converting enzyme 2 (ACE2) on the 
host cell surface is of important interest since it 
initiates the infection process. Cryoelectron 
microscopy (Cryo-EM) structure analysis has 
make known that the binding affinity of SARS-
CoV-2 S protein to ACE2 is approximately 10−20 
times higher than that of SARS-CoV S protein 
binding to ACE2 [33,34]. It is consider that the 
binding affinity may contribute to the reported 



 
 
 
 

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Fig. 4. MHV genome organization and replicase proteins 
 

 
 

Fig. 5. Life cycle of coronavirus in a host cell 
 
higher transmissibility spread and 
contagiousness of SARS-CoV-2 as compared to 
SARS-CoV [23]. 
 
The search also exists for discovery a 
breakthrough of therapeutic agents such as 
drugs and vaccine for targeting the highly 
preserved proteins related with both SARS-CoV 

and SARS-CoV-2 proteins [34-37]. RNA-
dependent RNA polymerase (RdRp) and  
Coronavirus main protease (3CLpro) of SARS-
CoV-2 share over 95 % of sequence similarity 
with those of SARS-CoV notwithstanding the fact 
that these two viruses shows or demonstrate 
only 79 % sequence similarity at the genome 
level proteins [34-37]. On the foundation of 



 
 
 
 

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sequence arrangement and homology modeling, 
SARS-CoV and SARS-CoV-2 share an 
extremely preserved receptor-binding domain 
(RBD), a domain of S protein and 76% of 
sequence similarity in their S proteins [34-37]. 
Although the Papain-like protease (PLpro) 
sequences of SARS-CoV-2 and SARSCoV are 
only 83% similar, they share the same active 
sites [35]. 
 

3. TRANSMISSION OF COVIDS-19 
 

The virus that causes COVID-19 most likely 
emerged or come out from an animal source, 
which is now spreading from one person to the 
other. Via respiratory droplets generate when an 
infected individual sneezes or coughs can extend 
the spread of the virus to close contact (within 
about 6 feet length). The COVID-19 can also be 
contracted by touching a surface or object that 

has been contaminated with the virus from an 
infected person and then touching their own 
mouth, nose, or perhaps their eyes.  
 

3.1 Symptoms of Covid-19 
 
Patients with COVID-19 will eventually have 
slight to severe respiratory illness with symptoms 
of: 
 
 Fever 
 Cough 
 Running nose 
 Sore throat 
 Body Ache 
 Shortness or difficulty breathing 
 At severe complications from this virus such 

as pneumonia in the lungs, multi-organ 
failure and in some cases lead to death. 

 

 
 

Fig. 6. Common and uncommon symptoms of COVID-19 
 

 



 
 
 
 

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3.2 Preventive Actions and Spreading of 
COVID-19 to Others 

 
 People should avoid close by contact with 

people sneezing and coughing and people 
that are sick. 

 Avoid touching face, eyes, nose, and mouth 
with unwashed hands.  

 Washing of hands regularly with soap               
and running water for at least 30 seconds. 
Also the use of alcohol-based                        
hand sanitizer that contains at least 65% 
alcohol if soap and water are not          
available. 

 Stay home when you are sick.  
 People with COVID-19 symptoms produce                        

a respiratory droplets when they cough                    
or sneezes so, should practice cough 
manners or etiquette i.e maintaining 
distance when coughing or sneezing, cover 
coughs, wear face mask, sneezes with 
disposable tissues or clothing, and wash 
hands regularly.  

 Clean and disinfect frequently all touched 
objects and surfaces. 

 Limit person-to-person transmission which 
include reducing secondary infections 
amidst close by contacts and health care 

workers, and preventing transmission 
amplification. 

 Identify, isolate and be concerned for 
patients timely, including providing enhance 
care for infected patients to avoid spread of 
the disease. 

 Avoid unprotected contact with wild animals 
to Identify and reduce spread of virus from 
the animal source. 

 Converse critical risk and event information 
to all communities and counter 
misinformation. 

 Address all crucial unknowns regarding 
clinical harshness, extent of transmission 
and infection treatment options, and 
accelerate the development of diagnostics, 
therapeutics and vaccines. 

 Minimize social and economic impact 
through multispectral partnerships.  

 People that have traveled from an affected 
area, should be isolated and restrictions for 
2 weeks. If the patient develop symptoms 
during the isolation period with fever, cough, 
and trouble breathing, then seek for medical 
advice or call the health care provider for 
COVID-19 in the community before                
telling them about the travel and the 
symptoms.  

 

 
 

Fig. 7. Countries areas with reported confirmed cases of COVID-19, 26 April 2020 by ECDC 
 



 
 
 
 

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Fig. 8. Epidemic curve of confirmed COVID-19, by date of report and WHO region through 25 
March 2020 

 

 
 

Fig. 9. Distribution of COVID-19 cases worldwide, as at 26 April, 2020 by ECDC 
 

3.3 Summary Situation Worldwide as at 
26 April 2020 Reported by ECDC [38] 

 
 Globally: 2,931,787 confirmed cases 

worldwide and 203,596 deaths worldwide. 

 Asia: 456350 confirmed, and most case 
were reported in Turkey, Iran, China, India 
and Saudi Arabia with 107773, 89328, 
83909, 26496, and 16299 respectively  and 
16865 deaths, most death are in Iran,



 
 
 
 

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Fig. 10. Distribution of COVID-19 death cases worldwide, as at 26 April, 2020 by ECDC 

 
China, Turkey, India and Indonesia with 
5650, 4636, 2706, 824 and 720 death 
respectively. 

 America: 1134686 confirmed, most 
reported countries are US, Brazil, Canada, 
Peru and Mexico with  939053, 58509, 
45341, 25331 and 13842 respectively and 
63649 deaths, most death were recorded in 
US, Brazil, Canada, Mexico and Peru with 
53189, 4016, 2465, 1305 and 700 death 
respectively. 

 Europe: 1214584 confirmed, five most 
confirm case were in Spain, Italy, Germany, 
United kingdom and France with 219764, 
195351, 154175, 148377 and 124114 
respectively and 119306 deaths, most death 
were recorded in Italy, France, Spain,  
United kingdom and Belgium with 26384, 
22614, 22524, 20319 and 6917 death 
respectively. 

 Oceania: 8080 confirmed, five most cases 
were in Australia, New Zealand, Guam, 
Frence Polynesia and Fiji with 6703, 1121, 
141, 57, 18 death respectively and 106 
deaths, with the most death case recorded 
in Australia, New Zealand, Guam and 
Northern Mariana islands with 81, 18, 5, 2 
death respectively. 

 African Region: 30316 confirmed cases, 
five most countries are  South Africa, Egypt, 
morocco, Algeria and Cameroon with 4361, 
4319, 3897, 3256 and 1518 respectively  
and 1382 deaths, the top most countries are 

Algeria, Egypt, morocco, south Africa and 
Cameroon with 419, 307, 159, 86 and 53 
death cases respectively 

 Others: 696 confirmed and 7 deaths 

 
4. TREATMENT 
 
4.1 Efficacy and Safety of Chloroquine, 

Remdesivir (GS-5734) and Hydroxy-
chloroquine for the Treatment of 
COVID-19 

 
Coronavirus Disease-2019 (COVID-19) is a 
public health emergency of international concern. 
As of this time there is no recognize exact, 
effectual, proven, pharmacological treatment for 
the cure of COVID-19. Invitro studies have 
suggested that chloroquine, an immune 
modulant drug traditionally used to cure malaria, 
is effective in reducing viral replication in other 
contagion, as well as the SARS-associated 
coronavirus (CoV) and MERS-CoV [39,40]. 
Chloroquine (N4-(7-Chloro-4-quinolinyl)-N1,N1-
diethyl-1,4-pentanediamine) (CQ) has been used 
worldwide for above 80 years, and it is part of the 
World Health Organization (WHO) model list of 
vital medicines. The drug is also inexpensive and 
has a set up clinical safety profile. However, the 
effectiveness and safety of the drug chloroquine 
for treatment of SARS-CoV-2 (the novel virus 
causing COVID-19) pneumonia remains 
indistinct.  
 



 
 
 
 

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A group of Chinese researchers, from literature 
have studied the impact of chloroquine in vitro, 
using Vero E6 cells contaminated by SARS-CoV-
2 at an array of contagion (MOI) of 0.05. The 
study established the  fact  that chloroquine was 
extremely effectual in decrease viral N protein 
replication, with an effectual dosage (EC) 90 of 
6.90 μM that can be easily attainable with normal 
standard dosing, due to its advantageous 
penetration in tissues, including in the lung. The 
authors described that chloroquine is known to 
obstruct virus contagion by cumulating 
endosomial pH and by meddling with the 
glycosylation of cellular receptor of SARSCoV. 
Also guesswork on the possibility that the known 
immunomodulant effect of the drug may improve 
the antiviral effect in vivo [41]. 
 
A description letter written by Chinese authors 
give an account that a news meeting from the 
State Council of China had stated that 
chloroquine phosphate had established marked 
effectiveness and satisfactory safety in treating 
COVID-19 related pneumonia in multi-center 
clinical trials conducted in China. The authors 
also specified that these discovery came from 
more than 100 patients included in the trials [42]. 
Evidence of such data was sought in the trial 
registries to review and was found none. So far 
cases had been reported in 213 countries as at 
26th April 2020, the low cost of chloroquine is a 
main advantage for both the extreme stressed 
healthcare systems of involved elevated-income 
countries and none funded healthcare systems of 
mid-and low-income counties. 
 
The skilled agreement was in print on 20th 
February by a multicentre cooperation group of 
the Department of Science and Technology of 
Guangdong Province and Health Commission of 
Guangdong Province paper and have to do with 
specifically to the use of chloroquine phosphate. 
No information was provided on condition that 
the method used to attain agreement [43]. Based 
on the in vitro evince and still not published 
clinical experience, the board recommended and 
endorsed chloroquine phosphate tablet, at a 
dose of 500 mg twice per day for 10 days, for 
patients diagnosed as slight mild and severe 
cases of SARS-CoV-2 pneumonia, on condition 
that there were no opposition or contraindication 
to the drug. 
 
Research have shown that chloroquine (CQ) and 
remdesivir (GS-5734), efficiently inhibited SARS-
CoV-2 contagious in vitro. Remdesivir is a 
nucleoside analog pro drug technologically 

advanced by Gilead Sciences (USA). A clinical 
report in United States showed that treatment 
with remdesivir improved and better the clinical 
state of the first patient infected by SARS-CoV-2 
[44] and a stage III clinical trial of remdesivir in 
opposition to SARSCoV-2 was open in Wuhan 
on February 4, 2020. Although, as an 
experimental drug, remdesivir is not likely to be 
largely obtainable for treating a very large 
number of patients in a timely way. However, of 
the two potential drugs for treating of COVID-19, 
CQ happen to be the best drug of choice for 
large-scale use because of  its obtainability and 
availability, a safety record proven, and a 
moderately low in cost.  
 
Chloroquine CQ (N4-(7-Chloro-4-quinolinyl)-N1, 
N1-diethyl-1,4-pentanediamine) have been in 
used for long in the treatment of  malaria and 
amebiasis. However, Plasmodium falciparum 
technologically advanced extensive resistance to 
it, and with the advancement of new anti-malarial 
drugs, CQ has become a choice for the 
prophylaxis of malaria. Furthermore, over dose of 
CQ can cause acute or severe poisoning and 
death [45]. In the past years, due to occasional 
use of CQ in clinical practice, its manufacture 
and market supply was very much reduced, at 
least in China.  
 
Hydroxychloroquine (HCQ) sulfate, is a 
derivative of CQ, and was first synthesized in 
1946 by initiating a hydroxyl group OH into CQ.  
HCQ establish and demonstrated to be much 
less (~40%) toxic than CQ in animals [46]. HCQ 
is still extensively obtainable and available to 
treat autoimmune diseases, such as rheumatoid 
arthritis and systemic lupus erythematosus. 
Since CQ and HCQ have similar chemical 
structures and mechanisms of acting as a feeble 
base and immune modulator, HCQ have shown 
to be more effective and potent drugs to treat 
SARS-CoV-2. In fact, as of February 23, 2020, 
seven clinical trial records were found in Chinese 
Clinical Trial Registry for using HCQ to treat 
SARS-CoV-2. What makes HCQ to be more 
efficacious than CQ in treating SARS-CoV-2 
infection still be short of experimental prove. 
 
Liu et al. [47] assess the antiviral impact of HCQ 
against SARS-CoV-2 infection in comparison to 
CQ in vitro. Initially, the cytotoxicity of HCQ and 
CQ in African green monkey kidney VeroE6 cells 
(ATCC-1586) was determined by standard CCK8 
assay. The result demonstrated that the 50% 
cytotoxic concentration (CC50) values of CQ and 
HCQ were 273.20 and 249.50 μM, respectively, 



 
 
 
 

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156 

 

which shows a no significant different from each 
other. The antiviral activity of CQ versus HCQ 
was compared, and the dose–response curves of 
the two compounds against SARS-CoV-2 were 
evaluated at four several multiplicities of infection 
(MOIs) by enumerate of viral RNA copy numbers 
in the cell supernatant at 48 h post infection (p.i.). 
The result showed that, at all MOIs (0.01, 0.02, 
0.2, and 0.8), the 50% maximal effectiual 
concentration (EC50) for CQ were 2.71, 3.81, 
7.14 and 7.36 μM respectively, and HCQ were 
4.51, 4.06, 17.31, and 12.96 μM respectively at 
all MOIs. CQ values was lower than that of HCQ. 
The differences in EC50 values were statistically 
significant at an MOI of 0.01 (P < 0.05) and MOI 
of 0.2 (P < 0.001).  
 
Consequently, the selectivity index (SI = 
CC50/EC50) of CQ (100.81, 71.71, 38.26, and 
37.12) was higher than that of HCQ (55.32, 
61.45, 14.41, 19.25) at MOIs of 0.01, 0.02, 0.2, 
and 0.8 respectively. These results were verify 
by immune fluorescence microscopy as 
indication by several expression stage of the 
virus nucleoprotein (NP) at the indicated drug 
concentrations at 48 h p.i. This study suggest 
that the anti-SARS-CoV-2 activity of HCQ appear 
to be less strong or potent compared to CQ, at 
slightest at certain MOIs. The two drugs CQ and 
HCQ are feeble bases that are known to raise 
the pH of acidic intracellular organelles, such as 
endosomes/lysosomes, vital for membrane 
synthesis.  
 
Furthermore, CQ could inhibit SARS-CoV entry 
via altering the glycosylation of ACE2 receptor 
and spike protein [48]. Extra additional 
experiment confirmed that HCQ efficiently 
inhibited the entry step, in addition to the post-
entry stages of SARS-CoV-2, which was also 
found upon CQ treatment.  
 
To further discover the full mechanism of action 
of CQ and HCQ in inhibiting the COVID-19 entry, 
co-localization of virions with early endosomes 
(EEs) or endo lysosomes (ELs) was examine by 
immunofluorescence analysis (IFA) and confocal 
microscopy. Quantification examination showed 
that, at 90 min p.i. in untreated cells, 16.2% of 
adopt virions (anti-NP, red) were detected in 
early endosome antigen 1 (EEA1)-positive EEs 
(green), whereas more virions (34.3%) were 
transfer into the late endosomal–lysosomal 
protein LAMP1+ ELs (green) (n > 30 cells for 
each group). By difference, in the presence of 
CQ or HCQ, significantly more virions (35.3% for 
CQ and 29.2% for HCQ; shows a significant P 

<0.001) were detected in the EEs, while only 
very few virions (2.4% for CQ and 0.03% for 
HCQ; P < 0.001) were found to be co-localized 
with LAMP1+ ELs (n > 30 cells).  
 
This suggested that both CQ and HCQ obstruct 
the transport of SARS-CoV-2 from EEs to ELs, 
which happen to be a condition to release the 
viral genome as in the case of SARS-CoV [49]. 
However, CQ and HCQ treatment caused 
obvious changes in the number and 
size/morphology of EEs and ELs. In CQ and 
HCQ-treated cells, unusually increase EE 
vesicles were seen, arrows in the upper panels), 
many of which are even larger than ELs in the 
untreated cells. In the untreated cells, most EEs 
were much smaller than ELs. Previous report 
study have showed that treatment with CQ 
induced the formation of expanded cytoplasmic 
vesicles [50].  
 
Within the EE vesicles, virions (red) were 
contained around the membrane (green) of the 
vesicle. The treatment with CQ did not cause 
noticeable changes in the number and size of 
ELs; however, the regular vesicle structure 
seemed to be disrupted, at least partially. By 
difference, in HCQ-treated cells, the size and 
number of ELs raised significantly, arrows in the 
lower panels. Since acidification is important and 
vital for endosome maturation and function, then 
surmise that endosome maturation might be 
blocked at midway stages of endocytosis, 
resulting in failure of additional transport of 
virions to the ultimate releasing site. CQ was 
reported to elevate the pH of lysosome from 
about 4.5 to 6.5 at 100 μM [51]. 
 
Research have shown that oral absorption of CQ 
and HCQ in humans is very effective in the 
treatment of SARS-CoV-2. In animals, both 
drugs share similar tissue distribution patterns, 
with high concentrations in the liver, spleen, 
kidney, and lung spread levels of 200–700 times 
higher than those in the plasma [52]. It was 
reported that safe dosage (6–6.5 mg/kg per day) 
of HCQ sulfate could generate serum levels of 
1.4–1.5 μM in Humans. Therefore, with a safe 
recommended dosage, HCQ concentration in the 
above tissues is likely to be achieved to inhibit 
SARS-CoV-2 infection. 
 

5. CONCLUSION  
 

Coronaviruses are diverse family of viruses that 
interact at various levels with constituent of host 
cells taking this benefit of some of the cellular 



 
 
 
 

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157 

 

machineries for replication and proliferation. In 
conclusion, CQ and HCQ can efficiently inhibit 
SARS-CoV-2 infection in vitro and it is more 
effective with HCQ. In combination with its anti-
inflammatory function, and was predict that the 
drug has a good effect to combat the virus 
disease. This possibility awaits confirmation by 
clinical trials. HCQ is less toxic than CQ, 
prolonged and overdose usage of HCQ can still 
cause poisoning. Although the use of chloroquine 
can also support expert opinion, clinical use of 
this drug in patients with COVID-19 should stick 
to the ethical approval as a trial as stated by the 
WHO. 
 

CONSENT 
 
It is not applicable. 
 

ETHICAL APPROVAL 
 
It is not applicable. 

 
COMPETING INTERESTS 
 
Authors have declared that no competing 
interests exist. 

 
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