ANTIBODY RESPONSE TO DENGUE VIRUS PROTEINS IN DENGUE PATIENTS

Abstract

Dengue virus proteins have been shown to be involved in protection as well as the pathogenetic mechanism in DHF/DSS. Antibody reactivities against non-structural proteins NS1, NS3 and NS5 and structural protein E were analysed in dengue patients’ sear. Dengue virus structural protein E and non-structural proteins NS1, NS3 and NS5 of the four dengue serotypes were obtained from dengue infected C6/36 cells which were harvested on predetermined days postinfection to obtain the maximal amounts of viral proteins for studies. The pattern of antibody responses to the virus proteins of the four dengue serotypes in a group of convalescent dengue patients has been found to be similar. The proportion of sera reacting to at least one of the non-structural proteins NS1, NS2, NS3 and NS5 was 76.6% but only 5% of the sera reacted against structural E glycoprotein. The difference in antibody reactivity was significant among the four dengue serotypes. Among the non-structural proteins, the number of sera which reacted against the NS1 glycoprotein was significantly higher than that against NS3 protein of dengue types 1 and 2 viruses. The number of reactive sera against NS1 was also significantly higher than against NS5 in dengue types 1, 2 and 4 viruses. However, the pattern of antibody responses to NS3 and NS5 was essentially similar. Cross-reactivity among dengue virus serotypes in antibody responses to dengue virus were found to be similar in two groups of patients; one group from a dengue outbreak from which dengue 2 was predominantly isolated and the other from dengue outbreaks of unknown serotype. The western blot analyses of sera from dengue patients from known dengue virus serotype have been isolated also revealed a similar pattern of antibody reactivity against the individual viral proteins of the four dengue serotypes. Antibody reactivity against diner and monomer forms of NS1 have been studied in both mild and severe forms of dengue infection. Both dimer (20% to 35%) and monomer (5% to 15%) forms were found in the acute and convalescent sera of dengue fever patients, but a higher number of acute sera reacted against the dimer form. In the convalescent sera, similar number of patients reacted to both dimer and monomer forms of NS1. In primary dengue infections, antibodies to the dimer and the monomer forms were only found in the convalescent sera but not it the acute sera. In secondary infections, antibodies to both dimer and monomer forms were detected in both acute and sera convalescent sera. In sera from DHF/DSS patients, only the dimer form was observed in the acute sera, whereas both forms were observed in the acute sera, whereas both forms were observed in the convalescent sera with a higher frequency in the dimer form. The different patterns of antibody responses in the acute and convalescent sera of dengue fever and DHF/DSS patients suggest that the dimer and the monomer forms of NS1 may be involved in the pathogenesis of dengue infection.