DIAGNOSTICS ALGORITHMS IN DENGUE INFECTIONS

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1 ECDC training Workshop on laboratory diagnosis of dengue virus infections Berlin, January 2012 DIAGNOSTICS ALGORITHMS IN DENGUE INFECTIONS Cristina Domingo Carrasco Robert Koch Institut

2 KINETICS OF VIRUS REPLICATION AND HOST RESPONSE FEVER Viral dissemination Antibodies in serum Viremia The patterns of viremia and immune response after dengue infection are different in primary and secondary infections

3 KINETICS OF VIRUS REPLICATION AND HOST RESPONSE IN PRIMARY INFECTIONS 99% 80% Guzmán MG, Nature Reiews, 2010 The physiological definition of a primary infection is one characterized by a high molar fraction of anti dengue IgM and low molar fraction of anti dengue IgG

4 KINETICS OF VIRUS REPLICATION AND HOST RESPONSE IN PRIMARY INFECTIONS CROSS REACTING ANTIBODIES SEROTYPING ANTIBODIES 90 Specimens obtained during late convalescence from patients with a primary seroresponse pattern may be useful for serotyping

5 KINETICS OF VIRUS REPLICATION AND HOST RESPONSE IN SECONDARY (ANAMNESTIC) INFECTIONS PRIMARY INFECTION SECONDARY INFECTION Viremia IgM IgG Viremia IgM IgG The physiological definition of a secondary infection isone characterized by a low molar fraction of anti dengue IgM and a high molar fraction of IgG broadly reactive to flaviviruses

6 KINETICS OF VIRUS REPLICATION AND HOST RESPONSE IN SECONDARY (ANAMNESTIC) INFECTIONS ANTIBODIES SEROTYPE 1st DENGUE CROSS REACTING ANTIBODIES Viremia IgM IgG The physiological definition of a secondary infection isone characterized by a low molar fraction of anti dengue IgM and a high molar fraction of IgG broadly reactive to flaviviruses

7 KINETICS OF VIRUS REPLICATION AND HOST RESPONSE DIAGNOSTIC ALGORITHMS NS1 antigen D. NS1 antigen D. SEROLOGY SEROLOGY MOLECULAR D. MOLECULAR D VIRAL ISOLATION VIRAL ISOLATION Viremia IgM IgG Viremia IgM IgG PRIMARY INFECTIONS SECONDARY INFECTIONS Domingo C., de Ory F., Sanz J.C., et al. Diagnostic Microbiol. and Infect. Dis. 2009

8 WHEN A SECONDARY INFECTION SHOULD BE CONSIDERED? Presence of IgG 2 3 days after onset together with viral genome or NS1 antigen HOW TO DISCRIMINATE BETWEEN PRIMARY AND SECONDARY DENGUE INFECTION? IgM/IgG ratio Avidity index Domingo et al, Diagn. Microbiol. Infect. Dis., 2009 Influence of previous flavivirus vaccines in the serological profile

9 Time dependent discriminatory power of the IgM/IgG ratio and the avidity test 110 IgG corrected avidity index PRIMARY SECONDARY R 2 = 0,045 R 2 = 0, Days of evolution IgG avidity corrected index in primary dengue confirmed cases (22 samples) and secondary dengue confirmed cases (15 samples) plotted against days after start of symptoms Domingo C. et al, Diagn. Microbiol. Infect. Dis., 2009

10 KINETICS OF VIRUS REPLICATION AND HOST RESPONSE INFLUENCE OF PREVIOUS VACCINATIONS YELLOW FEVER VACCINE JAPANESE ENCEPHALITIS VACCINE TRAVELLERS TICK BORNE ENCEPHALITIS EUROPEANS

11 ACUTE DENGUE CASE CLASSIFICATION CONFIRMED PRIMARY ACUTE DENGUE CONFIRMED SECONDARY ACUTE DENGUE PCR NS1 antigen IgM IgG / +/ + IgM/IgG ratio <1.8 2 IgG avidity index >50% PCR NS1 antigen IgM IgG + /+ +* + + /+ +* + +* * In the absence of previous flavivirus vaccination PROBABLE SECONDARY ACUTE DENGUE* PCR NS1 antigen IgM IgG * SAMPLE < 10 days post onset

12 WHICH SAMPLES ARE SUITABLE? Genome detection and virus isolation: serum, plasma, blood, CSF, tissues Antigen detection: serum, tissues Specific antibodies: serum, CSF WHEN SHOULD THE SAMPLES BE COLLECTED? As soon as possible The collection of paired samples, optimal 10 days apart, must be encouraged to confirm or refute acute dengue diagnosis In the envent of a fatality at the time of death HOW MUST THE SAMPLES BE COLLECTED? Aseptically Identify the samples with patient ID, date of collection, type of sample Use screw cap tubes preferably For genome detection avoid heparin or EDTA

13 HOW MUST THE SAMPLES BE STORED AFTER COLLECTION? During the first 24h after collection: 4 C but preferably 80 C or 20 C More than 24h after collection: Viral isolation: 80 C Genome: storage short time 20 C ( C preferred) Antigen/antibody detection: 20 C WHICH ARE THE BIOSAFETY REQUIREMENTS FOR SAMPLE TRANSPORT? Dengue is a BSL 3 pathogen in Europe Sample transport must be done following current normative for infectious clinical specimens (double package, dessicant, absorbent material, labelling ) OPTION: The samples can be sent in specific buffers (AVL buffer, RNA later buffer, QIAGEN): inactivation of the pathogen plus protection RNA

14 WHICH ARE THE BIOSAFETY REQUIREMENTS FOR SAMPLE MANIPULATION ON ARRIVAL? Viral isolation of samples suspected of dengue infection must be performed in BSL 3 facilities Sample preparation and inactivation for molecular or serological diagnosis could be performed in BSL 2 facilities under Class II biosecurity laminarflow and personal protection measures (double pair of gloves, mask, lab coat ) Inactivate the samples under the laminar flow using suitable buffers or by heating at 56 C during 1h for use in serological assays (only sera) Special consideration for samples of DHF cases coming from VHF endemic areas

15 WHICH INFORMATION DOES THE LABORATORY NEED FOR FURTHER INTERPRETATION OF THE RESULTS? Mandatory: Date of onset of illness Date of sample collection Travel history (country, dates ) Contact physician Recommended: Other diagnosis Previous flavivirus infections orvaccinations Nationality History of previous travel to endemic areas Previous fever episodes after travel Concise clinical findings Age