Seroprevalence and Serotyping of Dangue in Fection in Nepal

Abstract

Dengue fever represents a serious emerging infectious disease and has become a global epidemic with almost half of the world’s population at risk of infection. Dengue is arthropod-borne viral disease caused by RNA virus of the family Flaviviridae and spread by Aedes mosquitoes mainly, Aedes aegypti and A. albopictus and are prevalent in tropical and sub-tropical countries. There are 4 distinct, but closely related, serotypes of the virus that cause dengue (DENV-1, DENV-2, DENV-3 and DENV-4). As It is one of the emerging viral diseases in Nepal, people living mainly in Terai region are at high risk. Furthermore, cocirculation of multiple serotypes may worsen any outbreak significantly by increasing the= risk of patients which might lead to death due to immune pathology driven complications. This study aims to determine the antibody titer against dengue serotypes circulating in Nepalese population by serotype specific In-House ELISA and helps to know whether Nepalese population have protective antibodies against dengue virus. In this study, In-house ELISA was performed by using serotype specific antigens for dengue virus. The study consisted of total sample size of 32 among them 62.5 % were males (n=20) and 37.5% were females (n=12) with the ratio of male: female as 1.67:1. The age group ranged from 14 years to 72 years. Antibody production against different serotypes of dengue were found to be 62.5%, 68.75%, 6.25% and 56.25% respectively for DENV-1, DENV-2, DENV-3 and DENV-4 respectively. In case of In-House ELISA, the OD values were found to be higher for DENV-1 antigen and DENV-2 and lower for DENV-3. The statistical analysis was also performed by unpaired t-test. The p-value was found to be <0.05 for all the controls and samples and there was significant difference between the mean of the positive and negative samples. Most of the samples which were positive in In-Bios Kit has shown to have higher antibody titer for all antigens. The samples which were negative for the kit also showed lower antibody titer. Out of 32 samples 15 samples were found IgM positive while only two samples were positive for IgG ELISA, higher IgM titer showed that patients had a recent acute dengue infection and IgG positive showed that person had an infection sometimes in past. Calculating the ratio between IgG and IgM, it was found that most of cases were of primary infection. Molecular serotyping was done by Nested Reverse Transcriptase PCR (RT-PCR), using dengue specific primers for part of envelope region, which showed the circulation of DENV-1 in the year 2016 in NEPAL. The developed In-House ELISA was able to determine the antibody produced against theserotypes of dengue virus (DENV 1-4) in Nepalese population. Till now ELISA kits for NS1antigen and antibody detection (IgG and IgM) kits are available, however, no any serotypespecific antibody detection ELISA has been developed. Hence this study might be useful inserotype identification which is important in epidemiological and pathological analysis. Key Words: DENV, RT-PCR, In-House ELISA, Serotyping