Dengue extract of Carica papaya leaves (PLE) against dengue

 Dengue disease is characterized by marked
decrease in platelet count which is life threatening. In the present study, we
investigated the anti-viral activity of aquous extract of Carica papaya leaves (PLE) against
dengue virus (DENV) and its effect on platelet augmentation. Anti-dengue
activity of PLE in DENV infected THP-1 cells was determined by immunoblotting
and flow cytometry. Effect of PLE on erythrocyte damage was determined by
hemolytic and anti-hemolytic assays. Virus infected THP-1 cells were assayed
for IFN-? secretion.  Its effect on
platelet augmentation in cyclophosphamide induced thrombocytopenic rats was
also examined. The rats were divided into five groups, control,  cyclophosphamide control, PLE only treated group,
cyclophosphamide induced rats in which PLE dose was given prophylactically and
in fifth group PLE dose was given therapeutically after establishment of
thrombocytopenia. Platelet
count of blood from retro orbital plexus of rats was examined at
different time interval of 1st, 4th, 7th, 11th and 14 th
day of study.  On 14 th  day
rats were sacrificed for  histopathological examination  of  liver, kidney and spleen . Plasma of thrombocytopenic
rats was examined for TPO and IL-6 secretion.

 PLE significantly
decreased the expression of DENV envelope and NS1 protein in DENV infected
THP-1 cells. Marked decrease in intracellular viral load by PLE confirmed its
antiviral activity.PLE was found to significantly decrease erythrocyte damage
and hydrogen peroxide induced lipid peroxidation in vitro. In in vivo
thrombocytopenia study average platelet count in  control rats was 595.33±15.9
 ×103/mm3 on day 1. Platelet count in cyclophosphamide group started to fall after Day
3 (239.5
± 40.63×103/ mm3
cyclophosphamide and  252.33 ± 20.36 × 103
/ mm3
in therapeutic) and remarkable thrombocytopenia
developed after day 7 (200.5 ±31.26 × 103/mm3 in
cyclophosphamide  and 172.66 ± 14.1 × 103/mm3
in therapeutic). However in third group
interestingly, there was only mild decrease in platelet count (415 ± 13.2 ×105/
mm3)  and on day 11 it reaches normal level (606.17 ±
65.94 × 103/ mm3). PLE
also increases platelet count  significantly in the fourth group (578.33± 57 ×103/
mm3) at day
14. PLE was also found to increase rat IL-6 and TPO levels in thrombocytopenic
rat plasma.  Our findings suggest
that PLE can be used as a potential antiviral agent as it helps in platelet
augmentation and exhibits excellent antiviral activity against DENV.

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Dengue is an  arboviral disease caused by dengue virus (DENV)
 belonging to the family Flaviviridae. It is endemic throughout
tropical and sub-tropical regions of the world causing around 390 million new
infections annually (Bhatt S et al., 2013). It is asymptomatic in majority of
people but   may cause dengue fever in few cases but if
untreated it may lead to dengue  hemorrhagic fever (DHF)  or in some instances results in a hypovolemic
shock syndrome, dengue shock syndrome (DSS) 
with the hallmark symptom of thrombocytopenia  (Henchal et al.,1990). Studies suggest that the low
platelet count is one of the major causes of bleeding in these patients. The
platelet count drops below normal level (150,000–450,000 platelets/? L) and may reach as low as < 40000 platelets/? L during day 3–7 of fever in many patients. Thrombocytopenia has always been one of the most decisive criteria used by WHO guidelines as a potential indicator of clinical severity WHO book. In WHO guidelines, the definitions generally describe a rapid decline in platelet count or a platelet count less than 150,000 per microliter of blood WHO book. Several reasons are held responsible for thrombocytopenia in dengue disease like bone marrow suppression, increased platelet destruction, platelet dysfunction, imbalance between coagulation, fibrinolysis and anti-coagulant pathways,  (Azeredo 2015). Recently  ojha has reported that platelet activation determines the severity of thrombocytopenia in dengue infection (Ojha et al., 2017).  There is no approved anti-dengue drug or vaccine available in the market although Dengvaxia vaccine of sanofi Pasteur has shown promising results in clinical trials but still it is not safe for use by children ( Guy et. al., 2011). Natural products have been the main source of test materials in the development of antiviral drugs based on traditional medical practices (Jassim and Naji, 2003). These products are considered to be effective and non-toxic. Currently, not a single natural product has actually been approved as an antiviral drug against DENV, although few are reported to have antiviral activity ( Mishra, et al., 2013;  Latifah 2013; Zandi et al.,  2012, Sharma et al. 2016 ).  Carica papaya, commonly known as papaya is a tree-like herbaceous plant, belonging to the family Caricacea. It is cultivated globally mainly for its fruit (Silva et al., 2007). Its almost all parts are used for miscellaneous purposes like fruits beside being used for edible purpose, also have anti-bacterial properties (Emeruwa 1982)  Papaya leaves are  reported to reduce symptoms of asthma, worming and dysentery (Parle M and Guruditta 2011) it also has  anti-cancerous properties (Noriko O et. al.,  2010).  Carica papaya leaf extracts are prescribed as a tonic for heart and also for the treatment of fever, pyrexia, diabetes, gonorrhea, syphilis, inflammation and  dressing foul wounds (Hasheen 2007, Aruoma 2006, Mehdipour 2006). Previous phytochemical analysis (Baskaran 2012) reveals the presence of flavonoids, alkaloids, carbohydrates, saponins, glycosides, phytosterols, phenolics, terpenoids and tannins in the leaves of Carica papaya. There are few studies which reports an increase in platelet count by usage of PLE in dengue patients ( Subenthiran et al. 2013, Yunita et al. 2012 )  but effect of PLE on dengue virus infection in vitro has not been studied so far. Therefore, the objective of the present study was to investigate the possible anti-dengue effects of papaya leaf extract and its role in platelet augmentation. Present study gives a scientific support that PLE can be used a potential therapeutic drug against dengue virus infection.  


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