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Kompanets Galina,
Far Eastern Federal University, Assistant Professor, School of Biomedicine Somov Institute of Epidemiology and Microbiology, Head, Leading Scientific Researcher, Laboratory of Hantavirus Infections E-mail: [email protected]
Iunikhina Olga,
Somov Institute of Epidemiology and Microbiology, Scientific Researcher, Laboratory of Hantavirus Infections,
Pacific State Medical University E-mail: [email protected]
Pott Anastasia,
Somov Institute of Epidemiology and Microbiology, Postgraduate student, Junior Scientific Researcher, Laboratory of Hantavirus Infections E-mail: [email protected]
Antibodies against Hepatitis E virus in humans in the non-endemic region of the Russia
Kuznetsova Natalia, Somov Institute of Epidemiology and Microbiology, Senior Scientific Researcher, Laboratory of Hantavirus Infections E-mail: [email protected]
Antibodies against Hepatitis E virus in humans in the non-endemic region of the Russia
Abstract: Hepatitis E virus (HEV) infection is very important public health problem in many countries worldwide. Most regions of Russia lay in moderate climatic zones and are considered as non-endemic for this infection and consequently no HEV cases were in official statistics until 2013. The main purpose of our study was the study of seroprevalence to HEV in the patients with different infectious diseases. We examined 57 sera samples from patients with infections accompanied by liver impairment that were hospitalized during 2013-2015 in the southern part of Russian Far East for the presence of antibodies against hepatitis E virus. We found that 7 (12.3 %) of the samples were positive for IgG or IgM antibodies. The detection of anti-HEV antibodies (especially IgM) in this non-endemic region of the world suggests that there is contact with the virus, which probably circulates in wild and domestic animals. We also suppose that some HEV cases can be imported from neighboring countries. The results prompt us to continue study of sources and genetic structure in our region.
Keywords: Hepatitis E virus, seroprevalence, non-endemic region.
Introduction
Hepatitis E virus (family Hepeviridae, genus Hep-evirus) is a non-enveloped positive-stranded RNA virus with an anicosahedral capsid and a size of27-34 nm. with a genome of ~7.2 kb. that contains three open reading frames [5, 1336-1338; 7, 123-125]. HEV is the causative agent of hepatitis E in humans, and many species of animals are reservoirs this virus. Most parts of the territory of Russia lay in moderate climatic zones, and are considered as non-endemic for HEV; however, there have been reports of a seroprevalence of from 2.1 % to 13.5 % in people in regions with a temperate climate [3, 18-21]. Given the current epidemiological situation, knowledge about this infection, common borders with such endemic regions as China, Turkmenistan, Uzbekistan, Kyrgyzstan, and Tajikistan, starting in 2013, HEV was made a notifiable disease in Russia as a distinct nosological entity of viral hepatitis. So far, 92 and 110 cases of HEV were registered in 2013 and 2014, respectively, in Russia [6].
The aim of our study was to examine the presence of anti-HEV antibodies in the sera of patients with different infectious diseases accompanied by liver impairment that were hospitalized during 2013-2015 in the southern part of the Far East of Russia.
Materials and methods
The study protocol was approved by the Somov Institute of Epidemiology and Microbiology Human
Research Review Committee and the Institutional Review Board (protocol №12 on 13.04.2014). All participants (n = 57) were informed of the testing and signed an informed consent form. The age of the study participants ranged from 8 to 66 years (mean 35.8 years). The number of male and women patients was nearly equal (30 males (52.6 %) and 27 women (47.4 %)). In serological assays, the diagnoses of hepatitis A, B, and C, lep-tospirosis, and hemorrhagic fever with renal syndrome in these patients were not confirmed.
Serum samples were tested for immunoglobulin (Ig) G and IgM against HEV by using a commercial ELISA kits and according to the manufacturer's guidelines (Vectogep E IgM and Vectogep E IgG, JSC Vector-Best, Koltsovo, Russia). Briefly, we tested serial two-fold dilutions (1:10-1:3200) of each sample and compared the results with the results for negative control antigens. The optical density (OD) value was measured at a wavelength of450 nm. using a microplate spectrophotometer (Multiskan EX, Labsystems). The critical optical density (COD) was the mean value of the OD of the two negative controls plus 0.20. A sample was considered positive if the OD value was equal to or higher than the COD value and the following analytical conditions were fulfilled: mean OD value, measured in the two cells with negative control was not more than 0.2 and OD value measured in the cell with positive control was not less than 0.6.
Results and discussion
Positive antibody titers of IgG or IgM against HEV were found for 7 (12.3 %) people (2 women and 5 men). The mean age of seropositive individuals was 46.86 (range 23-77) years. The preliminary diagnoses given for these persons were unknown fever (n = 2), yersini-osis (n = 2), scarlet-like fever (n = 2), and chronic hepatitis C (n = 1). Anti-HEV IgM (titer 1:200) antibodies were detected in one woman (43 years old) who lived in a rural area, suggesting an acute form of infection. Notably, anti-HEV IgG antibodies were found in a native Chinese man (23 years old) who was a seasonal worker on a farm in Primorski Krai.
The zoonotic nature of HEV, first proposed by Balayan [1, 155-165], has been confirmed by the detection of HEV and anti-HEV antibodies in animals in many counties worldwide, including Japan and China [4, 929-936; 8, 291-298]. It is well known that the primary route of HEV infection is the fecal-oral route, and the virus can be transmitted via contaminated water, raw meat, mollusks, and vegetables. One possible explanation for the anti-HEV antibodies in humans in non-endemic regions may be contact with infected people or reservoir animals, such as pigs, cats, rodents, and chickens.
HEV infection is usually an acute self-limiting disease, and in severe cases causes hepatic and extrahepat-ic manifestations, including a number of neurological
syndromes and renal injury. In immunocompromised patients, e. g., organ transplant recipients, patients requiring chemotherapy, and AIDS patients, HEV may be the cause of chronic infection with rapidly progressive fatal cirrhosis.
Recent years have been characterized by intensive labor migration from countries of Central Asia to Russia, and by the import of pork meat from China. These facts, among other factors, including possible persistence of HEV in synanthropic rodents [2, 2-3], can contribute to sporadic cases of viral hepatitis E in humans in different parts of the Far East of Russia. To our knowledge, no studies regarding the prevalence of viral hepatitis E in swine or any animals in our region have been performed.
Conclusions
The results of our study indicate that a part of the adult population in the south of the Russian Far East has been infected with hepatitis E virus. Sporadic cases of HEV may be related to many contributing factors, and an acute form of infection not associated with travelling abroad may be evidence of persistence HEV in animal reservoirs of Primorsky Krai or direct contact with an infected person. Further studies on the genetic structure of HEV, epidemiology, and epizootology are required to obtain new knowledge about this important emerging viral pathogen in far-eastern Russia.
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