Dengue virus infection-enhancing and neutralizing antibody balance in children of the Philippines and Indonesia

Dengue seroprevalence study in Bali

INTRODUCTION

Dengue infection poses significant public health problems in tropical and subtropical regions worldwide. The clinical manifestations of dengue vary from asymptomatic to severe dengue manifestations. This serological survey highlighted the high incidence of asymptomatic cases. This study aimed to determine the prevalence of dengue in healthy and ill adults in Bali.

METHODS

Cross-sectional seroprevalence surveys were performed between July 2020 and June 2021 among healthy and ill adults in Denpasar Bali. Blood samples were collected from 539 randomly selected urban sites in Denpasar. Immunoglobulin G antibodies against the dengue virus were detected in serum using a commercial enzyme-linked immunosorbent assay kit.

RESULTS

Overall, the dengue seroprevalence rate among the 539 clinically healthy and ill adults was high (85.5%). The median age was 34.1 (18-86.1). Most of the participants in the study were younger than 40 years (61.2%). Men were the dominant sex (54.5%). The study found a significant association between dengue seropositivity among people aged > 40 years and healthy status (p = 0.005; odds ratio [OR] = 0.459 and p < 0.001; OR = 0.336, respectively). The study reported that as many as 60% of the subjects had a history of previously suspected dengue infection. This study reflected the proportion of asymptomatic dengue patients requiring better assessment with a serological test.

CONCLUSION

The current study highlighted that real cases of dengue infection may be higher than reported, with a high prevalence of dengue seropositivity and a relatively dominant proportion of asymptomatic cases. The study guides physicians to be aware of every dengue infection in tropical countries and prevent the spread of the disease.

Trends in dengue research in the Philippines: A systematic review

Dengue is an important public health problem in the Philippines. We sought to describe the trends in dengue research in the country. We searched four databases and identified published studies on dengue research in the Philippines during the past 60 years. We reviewed 135 eligible studies, of which 33% were descriptive epidemiologic studies or case series, 16% were entomologic or vector control studies, 12% were studies on dengue virology and serologic response, 10% were socio-behavioral and economics studies, 8% were clinical trials, 7% were on burden of disease, 7% were investigations on markers of disease severity, 5% were on dengue diagnostics, and 2% were modeling studies. During the last decade, dengue research in the Philippines has increased and evolved from simple descriptive studies to those with more complex and diverse designs. We identified several key topics where more research would be useful.

Key Amino Acid Substitution for Infection-Enhancing Activity-Free Designer Dengue Vaccines

Dengue is a globally important disease caused by four serotypes of dengue virus. Dengue vaccine development has been hampered by antigenic cross-reactivity among serotypes, which potentially causes antibody-dependent enhancement of infection and disease severity. Here we found that a single amino acid substitution in the envelope protein at position 87 from aspartic acid to asparagine or at position 107 from leucine to phenylalanine is critical for suppressing the induction of infection-enhancing antibody in a mouse model. The site and type of amino acid substitution were determined via neutralization escape using an enhancing-activity-only monoclonal antibody that was engineered to reveal neutralizing activity. Mutated dengue type 1 DNA vaccines containing either or both amino acid substitutions induced neutralizing antibodies devoid of enhancing activity against all serotypes. The effect of substitution was further demonstrated using other serotypes and a tetravalent formulation. This finding may contribute to the development of infection-enhancing-activity-free dengue vaccines.

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Amino acids at E87 or E107 are critical for dengue-enhancing antibody induction

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Neutralization escape is useful for identifying the key types or sites of amino acids

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Each substitution can be applied to antigens of all four dengue serotypes

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A modified tetravalent DNA vaccine suppresses enhancing antibody induction in mice

FEVER AS INDICATOR TO SECONDARY INFECTION IN DENGUE VIRAL INFECTION

Dengue Virus Infections are distributed in tropical and sub-tropical regions and transmitted by the mosquitoes such as Aedes aegypti and Aedes albopictus. Dengue virus can cause dengue fever, dengue hemorrhagic fever and dengue shock syndrome or dengue and severe dengue classified by World Health Organization. Beside it concurrent infection virus salmonella had been found some cases who showed fever more than 7 days. Concurrent infection with two agents can result in an illness having overlapping symptoms creating a diagnostic dilemma for treating physician, such as dengue fever with typhoid fever. The aim of this research is detection of dengue virus and secondary infection with Salmonella typhi in patients suspected dengue virus infection. Detection of dengue virus and Salmonella typhi using immunochromatography test such as NS1, IgG/IgM for dengue virus infection, and IgM/IgG Salmonella and blood culture. The fifty children with dengue virus infection came to Soerya hospital and 17 cases suspected dengue virus infection, five cases showed a positive NS1 on the second day of fever and one case concurrent with clinical manifestation of convulsi on the third days of fever there were five cases only showed positive. It was showed in this study that on the fourth to six day of fever in dengue virus infection accompanied by antibody IgM & IgG dengue. There were 12 cases showed the clinical manifestation of concurrent dengue viral infection and Salmonella, all of them showed a mild clinical manifestation and did not show plasma leakage and shock. In this study we found the length of stay of concurrent Dengue Virus Infection and Salmonella infection is more than 10 days. These patients were also more likely to have co-existing haemodynamic disturbances and bacterial septicaemia which would have required treatment with inotropes and antibiotics. This idea is very important to make update dengue viral management to decrease mortality in outbreak try to gain new prevention method before the occurrence of outbreak.

Dengue-Immune Humans Have Higher Levels of Complement-Independent Enhancing Antibody than Complement-Dependent Neutralizing Antibody

Dengue is the most important arboviral disease worldwide. We previously reported that most inhabitants of dengue-endemic countries who are naturally immune to the disease have infection-enhancing antibodies whose in vitro activity does not decrease in the presence of complement (complement-independent enhancing antibodies, or CiEAb). Here, we compared levels of CiEAb and complement-dependent neutralizing antibodies (CdNAb) in dengue-immune humans. A typical antibody dose-response pattern obtained in our assay system to measure the balance between neutralizing and enhancing antibodies showed both neutralizing and enhancing activities depending on serum dilution factor. The addition of complement to the assay system increased the activity of neutralizing antibodies at lower dilutions, indicating the presence of CdNAb. In contrast, similar dose-response curves were obtained with and without complement at higher dilutions, indicating higher levels of CiEAb than CdNAb. For experimental support for the higher CiEAb levels, a cocktail of mouse monoclonal antibodies against dengue virus type 1 was prepared. The antibody dose-response curves obtained in this assay, with or without complement, were similar to those obtained with human serum samples when a high proportion of D1-V-3H12 (an antibody exhibiting only enhancing activity and thus a model for CiEAb) was used in the cocktail. This study revealed higher-level induction of CiEAb than CdNAb in humans naturally infected with dengue viruses.

Serodiagnosis of asymptomatic dengue infection

Dengue virus (DENV) is a mosquito-transmitted virus that is expanding across the world. The incidence of dengue infection, especially severe disease, has been increasing. DENV consist of 4 serotypes of single stranded RNA viruses (D1-D4) in the genus Flavivirus, family Flaviviridae. Majority of dengue infections are asymptomatic cases, which cause difficulty in disease control and are important in dengue surveillance. There is still no gold standard to diagnose asymptomatic dengue infection. Plaque reduction neutralization test (PRNT) has been developed for many purposes such as immunological study, clinical study, vaccine trial and is currently the most sensitive and specific method for serological surveillance. However, PRNT shows some degree of cross reaction among different dengue serotypes especially secondary dengue infection cases and to other flaviviruses. Moreover, various modification since the beginning make PRNT lack of inter-laboratory standardization which is an important issue. This paper discusses the important of asymptomatic dengue infection and its diagnostic method.

Complement-independent dengue virus type 1 infection-enhancing antibody reduces complement-dependent and -independent neutralizing antibody activity

Dengue fever and dengue hemorrhagic fever are globally important mosquito-transmitted viral diseases. However, the only licensed vaccine is not highly protective. Viremia is related to disease severity in infected humans, and it is thought to be reduced by neutralizing antibodies but increased by infection-enhancing antibodies. We established an assay system to measure the balance between neutralizing and enhancing antibodies and found that most dengue-immune individuals in endemic areas carry complement-independent enhancing antibodies (CiEAb). Studying CiEAb is important for dengue vaccine development because the enhancing activity of CiEAb does not decrease in the presence of complement, which can reduce the enhancing activity of other antibodies in vitro. Here, we investigated the effects of CiEAb on the activity of neutralizing antibodies (mainly, complement-dependent neutralizing antibodies; CdNAb) using cocktails of mouse monoclonal antibodies (MAbs) against dengue virus type 1 (DENV-1). These cocktails included MAbs with enhancing activity only (represented by D1-V-3H12 [3H12]) or neutralizing activity only (represented by D1-IV-7F4 [7F4]). Because 3H12, an IgG1 subclass antibody, is complement-independent and cross-reacted with all dengue serotypes, it is a suitable model of CiEAb. An approximately equal amount of 3H12 abolished the neutralizing activity of 7F4. The complement-dependent neutralizing activities of the IgG2a and IgG2b variants of 7F4 were also completely inhibited by ⩾3-fold concentrations of the IgG1 variant. The complement-dependent antibody activities of other anti-DENV-1 MAbs and those of MAbs directed against other serotypes were inhibited 50% by 3H12 at various mixing ratios, ranging from one-hundredth to 10-fold. The complement-dependent neutralizing activities of dengue-immune mouse ascites fluids were also effectively inhibited by 3H12. This suggests that concomitantly induced CiEAb exerts an unwanted effect on the protective capacity of a vaccine. Thus, the effective inhibition of the neutralizing activity of CdNAb by CiEAb has implications for dengue pathogenesis and vaccine development.

Dengue virus infection-enhancing antibody activities against Indonesian strains in inhabitants of central Thailand

Dengue virus (DENV) infection-enhancing antibodies are a hypothetic factor to increase the dengue disease severity. In this study, we investigated the enhancing antibodies against Indonesian strains of DENV-1-4 in 50 healthy inhabitants of central Thailand (Bangkok and Uthai Thani). Indonesia and Thailand have seen the highest dengue incidence in Southeast Asia. The infection history of each subject was estimated by comparing his/her neutralizing antibody titers against prototype DENV-1-4 strains. To resolve the difficulty in obtaining foreign live viruses for use as assay antigens, we used a recombinant system to prepare single-round infectious dengue viral particles based on viral sequence information. Irrespective of the previously infecting serotype(s), most serum samples showed significantly higher enhancement titers against Indonesian DENV-2 strains than against Thai DENV-2 strains, whereas the opposite effect was observed for the DENV-3 strains. Equivalent enhancing activities were observed against both DENV-1 and DENV-4. These results suggest that the genotype has an impact on enhancing antibody activities against DENV-2 and DENV-3, because the predominant circulating genotypes of each serotype differ between Indonesia and Thailand.

The Complexity of a Dengue Vaccine: A Review of the Human Antibody Response

Dengue is the most prevalent mosquito-borne viral disease worldwide. Yet, there are no vaccines or specific antivirals available to prevent or treat the disease. Several dengue vaccines are currently in clinical or preclinical stages. The most advanced vaccine is the chimeric tetravalent CYD-TDV vaccine of Sanofi Pasteur. This vaccine has recently cleared Phase III, and efficacy results have been published. Excellent tetravalent seroconversion was seen, yet the protective efficacy against infection was surprisingly low. Here, we will describe the complicating factors involved in the generation of a safe and efficacious dengue vaccine. Furthermore, we will discuss the human antibody responses during infection, including the epitopes targeted in humans. Also, we will discuss the current understanding of the assays used to evaluate antibody response. We hope this review will aid future dengue vaccine development as well as fundamental research related to the phenomenon of antibody-dependent enhancement of dengue virus infection.

A mouse monoclonal antibody against dengue virus type 1 Mochizuki strain targeting envelope protein domain II and displaying strongly neutralizing but not enhancing activity

Dengue fever and its more severe form, dengue hemorrhagic fever, are major global concerns. Infection-enhancing antibodies are major factors hypothetically contributing to increased disease severity. In this study, we generated 26 monoclonal antibodies (MAbs) against the dengue virus type 1 Mochizuki strain. We selected this strain because a relatively large number of unique and rare amino acids were found on its envelope protein. Although most MAbs showing neutralizing activities exhibited enhancing activities at subneutralizing doses, one MAb (D1-IV-7F4 [7F4]) displayed neutralizing activities without showing enhancing activities at lower concentrations. In contrast, another MAb (D1-V-3H12 [3H12]) exhibited only enhancing activities, which were suppressed by pretreatment of cells with anti-FcγRIIa. Although antibody engineering revealed that antibody subclass significantly affected 7F4 (IgG3) and 3H12 (IgG1) activities, neutralizing/enhancing activities were also dependent on the epitope targeted by the antibody. 7F4 recognized an epitope on the envelope protein containing E118 (domain II) and had a neutralizing activity 10- to 1,000-fold stronger than the neutralizing activity of previously reported human or humanized neutralizing MAbs targeting domain I and/or domain II. An epitope-blocking enzyme-linked immunosorbent assay (ELISA) indicated that a dengue virus-immune population possessed antibodies sharing an epitope with 7F4. Our results demonstrating induction of these antibody species (7F4 and 3H12) in Mochizuki-immunized mice may have implications for dengue vaccine strategies designed to minimize induction of enhancing antibodies in vaccinated humans.

[Research activities in Kobe-Indonesia Collaborative Research Centers]

Kobe-Indonesia Collaborative Research Center was established in Institute of Tropical Disease (ITD), Airlangga University, Surabaya, Indonesia in 2007 under the program of ''Founding Research Centers for Emerging and Reemerging Infectious Diseases'' supported by the Ministry of Education, Culture, Sports, Science and Technology, Japan, and then it has been under the Japan Initiative for Global Research Network on Infectious Diseases (J-GRID) since 2010. Japanese researchers have been stationed at ITD, conducting joint researches on influenza, viral hepatitis, dengue and infectious diarrhea. Also, another Japanese researcher has been stationed at Faculty of Medicine, University of Indonesia, Jakarta, carrying out joint researches on'' Identification of anti-hepatitis C virus (HCV) substances and development of HCV and dengue vaccines'' in collaboration with University of Indonesia and Airlangga University through the Science and Technology Research Partnership for Sustainable Development (SATREPS) supported by the Japan Science and Technology Agency (JST) and Japan International Cooperation Agency (JICA) since 2009. In this article, we briefly introduce the background history of Kobe University Research Center in Indonesia, and discuss the research themes and outcomes of J-GRID and SATREPS activities.