Evaluation of dengue serological tests available in Puerto Rico for identification of prior dengue infection for prevaccination screening

Dengue: A review of laboratory diagnostics in the vaccine age

Background. Dengue is an important arboviral infection of considerable public health significance. It occurs in a wide global belt within a variety of tropical regions. The timely laboratory diagnosis of Dengue infection is critical to inform both clinical management and an appropriate public health response. Vaccination against Dengue virus is being introduced in some areas.Discussion. Appropriate diagnostic strategies will vary between laboratories depending on the available resources and skills. Diagnostic methods available include viral culture, the serological detection of Dengue-specific antibodies in using enzyme immunoassays (EIAs), microsphere immunoassays, haemagglutination inhibition or in lateral flow point of care tests. The results of antibody tests may be influenced by prior vaccination and exposure to other flaviviruses. The detection of non-structural protein 1 in serum (NS1) has improved the early diagnosis of Dengue and is available in point-of-care assays in addition to EIAs. Direct detection of viral RNA from blood by PCR is more sensitive than NS1 antigen detection but requires molecular skills and resources. An increasing variety of isothermal nucleic acid detection methods are in development. Timing of specimen collection and choice of test is critical to optimize diagnostic accuracy. Metagenomics and the direct detection by sequencing of viral RNA from blood offers the ability to rapidly type isolates for epidemiologic purposes.Conclusion. The impact of vaccination on immune response must be recognized as it will impact test interpretation and diagnostic algorithms.

Comparison of the Sensitivity and Specificity of Commercial Anti-Dengue Virus IgG Tests to Identify Persons Eligible for Dengue Vaccination

The Advisory Committee on Immunization Practices (ACIP) recommended that dengue pre-vaccination screening tests for Dengvaxia administration have at least 98% specificity and 75% sensitivity. This study evaluates the performance of commercial anti-DENV IgG tests to identify tests that could be used for pre-vaccination screening. First, for 7 tests, we evaluated sensitivity and specificity in early convalescent dengue virus (DENV) infection, using 44 samples collected 7-30 days after symptom onset and confirmed by RT-PCR. Next, for the 5 best performing tests and two additional tests (with and without an external test reader) that became available later, we evaluated performance to detect past dengue infection among a panel of 44 specimens collected in 2018-2019 from healthy 9-16-year-old children from Puerto Rico. Finally, a full-scale evaluation was done with the 4 best performing tests using 400 specimens from the same population. We used virus focus reduction neutralization test and an in-house DENV IgG ELISA as reference standards. Of seven tests, five showed ≥75% sensitivity detecting anti-DENV IgG in early convalescent specimens with low cross-reactivity to Zika virus. For the detection of previous DENV infections the tests with the highest performance were the Euroimmun NS1 IgG ELISA (sensitivity 84.5%, specificity 97.1%) and CTK Dengue IgG rapid test R0065C with the test reader (sensitivity 76.2% specificity 98.1%). There are IgG tests available that can be used to accurately classify individuals with previous DENV infection as eligible for dengue vaccination to support safe vaccine implementation.

Expression of recombinant dengue virus type 1 non-structural protein 1 in mammalian cells and preliminary assessment of its suitability to detect human IgG antibodies elicited by viral infection

In recent years dengue has become a rapidly growing public health problem worldwide, however, the availability of accurate and affordable diagnostic immunoassays is limited, partly due to the difficulty of producing large quantities of purified antigen. Non-structural protein 1 (NS1) has shown to be a good candidate for inclusion in diagnostic assays and for serosurveys, particularly in endemic countries as a prerequisite for vaccination. In this work the NS1 antigen derived from dengue virus type-1 (DENV1) was expressed in HEK293-T cells and purified by affinity chromatography. The recombinant protein was recovered properly folded as dimers, highly purified and with good yield (1.5 mg/L). It was applied as a serological probe in an indirect ELISA developed in this work to detect human IgG antibodies. Preliminary comparative performance values of 81.1% sensitivity and 83.0% specificity of the developed and preliminary validated iELISA, relative to a commercial kit were obtained, suggesting that the purified recombinant DENV1 NS1 antigen is suitable to detect IgG antibodies, indicative of past DENV infection.

Public health impact and cost-effectiveness of implementing a 'pre-vaccination screening' strategy with the dengue vaccine in Puerto Rico

BACKGROUND

The World Health Organization (WHO) recommended 'pre-vaccination screening' as its preferred implementation strategy when using the licensed dengue vaccine (CYD-TDV; Dengvaxia, Sanofi), so that only individuals with previous dengue infection are vaccinated. The US Centers for Disease Control and Prevention (CDC) recommended use of CYD-TDV to prevent dengue in children with previous laboratory-confirmed dengue infection in regions where dengue is endemic. Here, we evaluate the public health impact and cost-effectiveness of a 'pre-vaccination screening' strategy in Puerto Rico.

METHODS

The current analysis builds upon a previously published transmission model used to assess the benefits/risks associated with dengue vaccination. For 'pre-vaccination screening', three alternative testing methods were assessed: one using an immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) dengue serotest, another with dengue serotesting using a rapid diagnostic test (RDT), and one using both sequentially (as recommended in Puerto Rico). The time horizon considered was 10 years.

RESULTS

In Puerto Rico, the disability-adjusted life years (DALYs) averted for 'pre-vaccination screening' with an ELISA-based program, RDT-based program, and both sequentially would be a median 1,192 (95% CI: 716-2,232), 2,812 (95% CI: 1,579-5,019), and 1,017 (95% CI: 561-1,738), respectively. These benefits would arise from the reduction in cases: median 24,961 (95% CI: 17,480-36,782), 58,273 (95% CI: 40,729-84,796), 20,775 (95% CI: 14,637-30,374) fewer cases, respectively. The cost per DALY averted from a payer perspective would be US$12,518 (95 %CI: US$4,749-26,922), US$10,047 (95% CI: US$3,350-23,852), and US$12,334 (95% CI: US$4,965-26,444), respectively. All three strategies would be cost saving from a societal perspective.

CONCLUSIONS

Our study supports the WHO and CDC 'pre-vaccination screening' guidance for CYD-TDV implementation. In Puerto Rico, regardless of the testing strategy and even with a relatively low rate of testing, it would be cost-effective from a payer perspective and cost saving from a societal perspective.

Field evaluation of rapid diagnostic tests to determine dengue serostatus in Timor-Leste

The live attenuated tetravalent CYD-TDV vaccine (Dengvaxia) is effective but has scarcely been used due to safety concerns among seronegative recipients. Rapid diagnostic tests (RDTs) which can accurately determine individual dengue serostatus are needed for use in pre-vaccination screening. This study aimed to determine the performance of existing RDTs (which have been designed to detect levels of immunoglobulin G, IgG, associated with acute post-primary dengue) when repurposed for detection of previous dengue infection (where concentrations of IgG are typically lower). A convenience sample of four-hundred-and-six participants (including 217 children) were recruited in the community. Whole blood was collected by phlebotomy and tested using Bioline Dengue IgG/IgM (Abbott) and Standard Q Dengue IgM/IgG (SD Biosensor) RDTs in the field. Serum samples from the same individuals were also tested at National Health Laboratory. The Panbio indirect IgG ELISA was used as a reference test. Reference testing determined that 370 (91.1%) participants were dengue IgG seropositive. Both assays were highly specific (100.0%) but had low sensitivity (Bioline = 21.1% and Standard Q = 4.6%) when used in the field. Sensitivity was improved when RDTs were used under laboratory conditions, and when assays were allowed to run beyond manufacturer recommendations (and read at a delayed time-point), but specificity was reduced. Efforts to develop RDTs with high sensitivity and specificity for prior dengue infection which can be operationalised for pre-vaccination screening are ongoing. Performance of forthcoming candidate assays should be tested under field conditions with blood samples, as well as in the laboratory.

Performance Evaluation of a Dengue IgG Rapid Diagnostic Test Designed to Determine Dengue Serostatus as Part of Prevaccination Screening

The World Health Organization has recommended prevaccination screening for prior dengue infection as the preferred approach prior to vaccination with the dengue vaccine CYD-TDV. These screening tests need to be highly specific and sensitive, and deliverable at the point-of-care. We evaluate here the sensitivity and specificity of the newly developed OnSite Dengue IgG rapid diagnostic test (RDT). A retrospective double-blind study of the sensitivity and specificity of the OnSite Dengue IgG RDT was performed using a sample panel consisting of archived serum specimens collected during CYD-TDV clinical trials in Latin American and Asia, with the reference serostatus for each sample determined by an algorithm using measured dengue PRNT90, PRNT50, and NS1 IgG ELISA. An additional panel of dengue seronegative samples positive for other flaviviruses and infections was used to assess cross-reactivity. Samples were included from 579 participants; 346 in the specificity panel and 233 in the sensitivity panel. The OnSite dengue IgG RDT exhibited a specificity of 98.0% (95% CI = 95.9 to 99.2) and sensitivity of 95.3% (95% CI = 91.7 to 97.6). The sensitivity for samples exhibiting a multitypic immune profile (PRNT90-positive to >1 dengue serotype) was 98.8% while for monotypic immune samples (PRNT90-positive to a single dengue serotype) it was 88.1%. The OnSite dengue IgG RDT showed minimal to no cross-reactivity to related flaviviruses. These findings support the use of the OnSite dengue IgG RDT to determine dengue serostatus in CYD-TDV prevaccination screening. IMPORTANCE Dengue remains a significant public health issue, with over 5.2 million cases reported to the World Health Organization (WHO) in 2019. The tetravalent dengue vaccine (CYD-TDV) is currently licensed for use in those aged ≥9 years; however, vaccinees with no previous exposure to dengue experience an increased risk of hospitalized and severe dengue upon subsequent heterotypic infection. Consequently, WHO recommends screening for prior dengue infection before vaccination. Screening tests for previous infection need to be highly specific and sensitive, and deliverable at the point-of-care. High sensitivity ensures that the largest number of individuals with previous infection can be identified and vaccinated, while high specificity prevents the inadvertent vaccination of those without previous infection. This study of the OnSite Dengue IgG Rapid Test, which was explicitly developed to meet this need, found that it had both high specificity (98.0% [95% CI = 95.9 to 99.2]) and sensitivity (95.3% [95% CI = 91.7 to 97.6]).

Dengue: A Growing Problem With New Interventions

Dengue is the disease caused by 1 of 4 distinct, but closely related dengue viruses (DENV-1-4) that are transmitted by Aedes spp. mosquito vectors. It is the most common arboviral disease worldwide, with the greatest burden in tropical and sub-tropical regions. In the absence of effective prevention and control measures, dengue is projected to increase in both disease burden and geographic range. Given its increasing importance as an etiology of fever in the returning traveler or the possibility of local transmission in regions in the United States with competent vectors, as well as the risk for large outbreaks in endemic US territories and associated states, clinicians should understand its clinical presentation and be familiar with appropriate testing, triage, and management of patients with dengue. Control and prevention efforts reached a milestone in June 2021 when the Advisory Committee on Immunization Practices (ACIP) recommended Dengvaxia for routine use in children aged 9 to 16 years living in endemic areas with laboratory confirmation of previous dengue virus infection. Dengvaxia is the first vaccine against dengue to be recommended for use in the United States and one of the first to require laboratory testing of potential recipients to be eligible for vaccination. In this review, we outline dengue pathogenesis, epidemiology, and key clinical features for front-line clinicians evaluating patients presenting with dengue. We also provide a summary of Dengvaxia efficacy, safety, and considerations for use as well as an overview of other potential new tools to control and prevent the growing threat of dengue .

Dengue pre-vaccination screening test evaluation for the use of dengue vaccine in an endemic area

Background

The dengue vaccine (Dengvaxia) is only recommended for individuals with prior dengue infection (PDI). This study aimed to perform a serosurvey to inform decision-making for vaccine introduction and identify appropriate target populations. We also evaluated the performance of the serological tests using plaque reduction neutralization test (PRNT) as a reference test in identifying PDI to determine suitability for pre-vaccination screening.

Methods

We enrolled 115 healthy individuals between 10 and 22 years of age living in the Ratchaburi province of Thailand. The serum samples were tested by PRNT to measure the prevalence and concentration of serotype-specific neutralizing antibodies. The performance of the IgG rapid diagnostic test (RDT, SD Bioline, Korea) and IgG enzyme-linked immunosorbent assay (ELISA, EUROIMMUN, Germany) in identifying PDI were evaluated by using PRNT as a reference method.

Results

Ninety-four (81.7%) individuals neutralized one or more dengue serotypes at a titer threshold greater than or equal to 10. Multitypic profiles were observed in 70.4% of the samples which increased to 91.9% in subjects aged 19–22. Among monotypic samples, the highest proportion was reactive against DENV-1 followed by DENV-2, DENV-3, and DENV-4. The highest anti-dengue antibody titers were recorded against DENV-1 and increased with age to a geometric mean NT50 titer (GMT) of 188.6 in the 19–22 age group. While both RDT and ELISA exhibited 100% specificity, RDT demonstrated low sensitivity (35%) with ELISA displaying much greater sensitivity (87%).

Conclusions

Almost 80% of adolescents and youth in Ratchaburi province had already been exposed to one or more of the dengue virus serotypes. The dengue IgG RDT displayed low sensitivity and is likely not be suitable for dengue pre-vaccination screening. These results support the use of IgG ELISA test for dengue vaccination in endemic areas.

Implementation strategies for the first licensed dengue vaccine: A meeting report

Dengue vaccination would enhance the control of dengue, one of the most frequent vector-borne viral diseases globally. CYD-TDV is the first dengue vaccine to be licensed, but global uptake has been hampered due to its use being limited to seropositive persons aged 9 years and above, and the need for a 3-dose schedule. The Partnership for Dengue Control (PDC) organized a meeting with key opinion leaders and stakeholders to deliberate on implementation strategies for the use of CYD-TDV. New data have emerged that support the shortening of the primary schedule from a 3 to 2 dose schedule, extending the age range below 9 to 6 years of age, and expanding the indication from endemic populations to also include travelers to endemic areas. Cost-effectiveness may improve with the modified 2-dose regimen and with multiple testing. Strategies to implement a dengue vaccination program have been developed, in particular school-based strategies. A range of delivery scenarios can then be considered, using various settings for each step of the intervention. However, several challenges remain, including communication about limiting the use of this vaccine to seropositive individuals only. Affordability will vary from country to country, as will government commitment and community acceptance. Well-tailored communication strategies that target key stakeholders are expected to make up a significant part of any future dengue vaccination program.

Salvana EM, de Lamballerie X, Olliaro PL, Peeling RW. Target product profile for a dengue pre-vaccination screening test

With increasing geographic spread, frequency, and magnitude of outbreaks, dengue continues to pose a major public health threat worldwide. Dengvaxia, a dengue live-attenuated tetravalent vaccine, was licensed in 2015, but post hoc analyses of long-term data showed serostatus-dependent vaccine performance with an excess risk of hospitalized and severe dengue in seronegative vaccine recipients. The World Health Organization (WHO) recommended that only persons with evidence of past dengue infection should receive the vaccine. A test for pre-vaccination screening for dengue serostatus is needed. To develop the target product profile (TPP) for a dengue pre-vaccination screening test, face-to-face consultative meetings were organized with follow-up regional consultations. A technical working group was formed to develop consensus on a reference test against which candidate pre-vaccination screening tests could be compared. The group also reviewed current diagnostic landscape and the need to accelerate the evaluation, regulatory approval, and policy development of tests that can identify seropositive individuals and maximize public health impact of vaccination while avoiding the risk of hospitalization in dengue-naive individuals. Pre-vaccination screening strategies will benefit from rapid diagnostic tests (RDTs) that are affordable, sensitive, and specific and can be used at the point of care (POC). The TPP described the minimum and ideal characteristics of a dengue pre-vaccination screening RDT with an emphasis on high specificity. The group also made suggestions for accelerating access to these RDTs through streamlining regulatory approval and policy development. Risk and benefit based on what can be achieved with RDTs meeting minimal and optimal characteristics in the TPP across a range of seroprevalences were defined. The final choice of RDTs in each country will depend on the performance of the RDT, dengue seroprevalence in the target population, tolerance of risk, and cost-effectiveness.

This paper describes the consensus on the minimum and ideal performance and operational characteristics of rapid tests that would be used for dengue pre-vaccination screening. This profile will incentivize industry to develop better pre-vaccination screening tests. The choice of which test to use depends on the seroprevalence of the population targeted for vaccination and the optimal balance between benefit and risks. The group also made suggestions for accelerating access to these pre-vaccination screening tests through streamlining regulatory approval and policy development.

Immunogenicity and safety of a tetravalent dengue vaccine and a bivalent HPV vaccine given concomitantly or sequentially in girls aged 9 to 14 years in Mexico

Dengue is endemic in several regions, and the global incidence is increasing. The recombinant, live, attenuated, tetravalent dengue vaccine (CYD-TDV) is recommended for dengue seropositive individuals ≥ 9 years. Human papillomavirus (HPV) vaccination is recommended for girls aged 9-14 years to prevent HPV infection-related cancers. This study assessed the immunogenicity and safety of a bivalent HPV (types 16 and 18) vaccine and CYD-TDV when co-administered concomitantly or sequentially. This was a Phase IIIb, randomized, open-label, multicenter study in girls aged 9-14 years in Mexico (NCT02979535). Participants were randomized 1:1 to receive three doses of CYD-TDV 6 months apart and two doses of bivalent HPV vaccine either concomitantly with, or 1 month before (sequentially), the first 2 CYD-TDV doses. Antibody levels were measured at baseline and 28-days after each vaccine dose for all participants, using an enzyme-linked immunosorbent assay for HPV-16 and HPV-18 antibodies, and a plaque reduction neutralization test for the four dengue serotypes; results are reported only for participants who were seropositive at baseline. Safety was assessed for all randomized participants throughout the study. Of the randomized participants, 305/478 (63.8%) were seropositive for dengue at baseline: 154 in the concomitant group and 151 in the sequential group. After the last HPV vaccine dose, the antibody titers for HPV were comparable in seropositive participants between treatment groups, with between group titer ratios of 0.966 for HPV-16 and 0.999 for HPV-18. After dose 3 of CYD-TDV, antibody titers were comparable for the concomitant and sequential groups across all serotypes, with between-group ratios close to 1 (serotype 1: 0.977; serotype 2: 0.911; serotype 3: 0.921; serotype 4: 0.931). CYD-TDV and a bivalent HPV vaccine administered concomitantly or sequentially in dengue seropositive girls aged 9-14 years elicited comparable immune responses with similar safety profiles.

Determining dengue virus serostatus by indirect IgG ELISA compared with focus reduction neutralisation test in children in Cebu, Philippines: a prospective population-based study

Background

Detection of dengue virus antibodies is important for understanding future dengue virus risk and for prevaccination screening. We aimed to evaluate the performance of a dengue IgG indirect ELISA in determining dengue seroprevalence in a cohort of children in the Philippines, using a focus reduction neutralisation test (FRNT) as the reference test.

Methods

In this prospective population-based cohort study, we enrolled healthy children residing in Bogo or Balamban, Cebu, Philippines, who were to be aged 9–14 years at the time of a mass dengue vaccination campaign. Sera were collected from participants and batch tested by indirect IgG ELISA and FRNT. The primary endpoint was dengue seroprevalence in the cohort, detected by ELISA, and validated by that detected by reference FRNT. This study is registered with ClinicalTrials.gov, NCT03465254.

Findings

We collected 2996 serum samples between May 2, and June 2, 2017, and we tested each sample with IgG ELISA. Using 1961 samples (65· 5%) that were tested with FRNT, and 1035 samples (34·5%) with imputed results, we found that 320 (10·7%) of 2996 children were dengue naive and 2676 (89·3%) were seropositive for previous dengue virus infection. Based on the 1961 non-imputed FRNT results classified as dengue seronegative or seropositive, the ELISA (with a 0·9 index value cutoff) showed 95·2% sensitivity, 93·4% specificity, 6·6% false positivity, and 4·8% false negativity. However, sensitivity of the ELISA was poor (77·1%) among children with immunity to just one dengue virus serotype. Of the 11 sera that were false positive with ELISA, seven samples (63·6%) were seropositive for Zika virus or Japanese encephalitis virus with FRNT.

Interpretation

Most children (89·3%) assessed in our study and eligible to participate in the mass dengue vaccination campaign were seropositive for previous dengue virus infection. Compared with FRNT, ELISA had high sensitivity and specificity (>90%), but the false-negative and false-positive rates makes the test suboptimal for prevaccination screening. Individuals who are falsely identified as seropositive by dengue IgG ELISA and then vaccinated might be at risk of developing severe disease during a subsequent exposure to wild-type dengue virus. Those with a monotypic profile would benefit the most from vaccination, but the sensitivity of the IgG ELISA was much lower in this group than in those with a multitypic profile.

Funding

Philippine Department of Health, Hanako Foundation, WHO, Swedish International Development Cooperation Agency through the International Vaccine Institute, and University of North Carolina, Chapel Hill, NC, USA.

Immune Response Persistence and Safety of a Booster Dose of the Tetravalent Dengue Vaccine in Adolescents and Adults Who Previously Completed the 3-dose Schedule 4-5 Years Earlier in Latin America: A Randomized Placebo-controlled Trial

BACKGROUND

We previously described an increased immune response 28 days after a booster dose of the live, attenuated, tetravalent dengue vaccine (CYD-TDV) in healthy adolescents and adults in Latin America (CYD64, NCT02623725). This follow-up study evaluated immune response persistence and safety of a CYD-TDV booster dose up to Month (M) 24 post-booster.

METHODS

This study included 250 participants who previously received 3 primary doses of CYD-TDV in the CYD13 (NCT00993447) and CYD30 (NCT01187433) studies, and who were randomized 4-5 years later to receive a CYD-TDV booster or placebo (3:1). Dengue neutralizing antibodies against the parental dengue virus strains were assessed using the plaque reduction neutralization test (PRNT50) at M6, M12, and M24 post-booster. Post-booster memory B-cell responses were assessed in a subset of participants using the FluoroSpot assay up to M12 post-booster.

RESULTS

In the CYD-TDV group (n = 187), dengue neutralizing antibody geometric mean titers (GMTs) declined from the peak at day 28 through to M24 for all serotypes. GMTs at M24 were similar to those at pre-booster among baseline dengue seropositives. A similar trend was observed for baseline dengue seronegatives, albeit at a lower magnitude. Previous vaccination-induced detectable B-cell memory responses in seropositives and seronegatives that decreased to pre-booster levels at M12 post-booster. The CYD-TDV booster dose was well-tolerated.

CONCLUSIONS

In baseline dengue seropositives, following a CYD-TDV booster dose administered 4-5 years after primary immunization, dengue neutralizing antibody GMTs and B-cell memory responses peaked in the short-term before gradually decreasing over time. A CYD-TDV booster dose could improve protection against dengue during outbreak periods.