INFLUENZA EVOLUTION: Challenges for diagnosis

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2 INFLUENZA EVOLUTION: Challenges for diagnosis Jairo A. Méndez-Rico Influenza Team PAHO/WHO, Washington, DC

3 Overview Every year, influenza infects up to one in five people around the world, and causes up to half a million deaths Human immune system can detect and destroy the virus However, people can catch flu many times throughout their lifetimes

4 Viral evolution Evolutionary process lead changes generating new viruses, therefore a new infection and a new immune response has to be established Evolution is a natural process that can occur spontaneously However, viruses are pressured to change: Immune response, vaccines, new cell receptors

5 Viral evolution Genetic punctual mutation aa change Not aa change Same protein Altered protein Deleterious Beneficial

6 Viral evolution: antigenic drift Genetic punctual mutation aa change Not aa change Same antigen New antigen Well recognized Not recognized

7 Viral evolution: antigenic drift Genetic punctual mutation aa change Not aa change Same antigen New antigen Antigenic drift Well recognized Not recognized

8 Viral evolution: influenza Before 2009 A/H1N1 A/H3N2 B/Vic B/Yam Different viruses with different proteins: Same viruses, same proteins, different lineages Hemagglutinin 1 / 3 Neuraminidase 1 / 2 Hemagglutinin Neuraminidase

9 Viral evolution: influenza Mutations to the HA1 region of the hemagglutinin protein are thought to drive the majority of antigenic drift in the influenza virus How does it affect lab diagnosis? James Stevens and Ian A. Wilson. SSRL Science Highlight - August 2004

10 Viral evolution: impact for characterization Lab characterization of antigenic phenotype is possible through the hemagglutination assays, based on: Hemagglutination Hemagglutination inhibition

11 Haemagglutination Science 4 July 1941: Vol. 94 no pp it was noted that the red cells of the infected chick agglutinated in the alantoic fluid.

12 Haemagglutination + = Non agglutinated RBC Influenza virus Haemagglutination Depends of viral HA to bind polysaccharides of RBS membrane

13 Haemagglutination inhibition J Exp Med 1 January 1942: Vol. 75 pp it was shown that the addition of specific immune serum inhibited the agglutination in the presence of the homologous virus

14 Haemagglutination inhibition + + Influenza virus Specific antibodies = Y Y Y Y Depends of specific antibodies to bind (opsonize) viral HA Haemagglutination inhibition

15 The challenge Y Y Y Y Haemagglutination Haemagglutination inhibition Since both process depend on HA, antigenic drift may alter the performance of the assays

16 The challenges Since the 1990s the receptor-binding characteristics of A(H3N2)have evolved

17 Faster evolution Bedford et al. elife 2014;3:e DOI: /eLife.01914

18 The challenges Since the 1990s the receptor-binding characteristics of A(H3N2)have evolved Two major consequences: 1. Difficulty for isolation in eggs 2. Progressive reduction in the ability to bind and agglutinate chicken RBC (1990s) and turkey RBC (2000s)

19 The challenge 1. Difficulty for isolation in eggs -Low egg isolation rates (Limited availability of candidate vaccine viruses) -Selective pressures (egg adaptation mutations)

20 Categorization in 2 groups: 1. Restriction to sialoglycans 2. Restriction to egg glycans Less prone to undergoing receptor (antigenic) drift

21 Egg-adapted strain was antigenically distinct from WHO recommended vaccine prototipe

22 The challenge: reducing the impact on vaccine selection Impact on vaccine selection

23 The solutions Change the age at which embryonated eggs are inoculated (9-10 days to days old) Change the inoculation route (to allantoic cavity) Change the egg incubation T o (from 33 o C to 35 o C) Low egg isolation rates Improved up to 18%

24 The solutions Utilizing egg/cell paired viruses (routine characterization) Egg adaptation mutations To estimate how differences between the two may alter HI profiles; helps to select the best A(H3N2) candidate vaccine viruses

25 The challenge 2. Progressive reduction in the ability to bind and agglutinate chicken RBC (1990s) and turkey RBC (2000s) - H3N2 Inadequate sialic acid receptor interactions -Technical difficulties to perform serologic assays (IH)

26 Decrease in HIA sensitivity Bedford et al. elife 2014;3:e DOI: /eLife Adapted from: Rambaut A. Integrating influenza antigenic dynamics with molecular evolution. Geneva, 2014

27 The challenge: Improving HI assays Additional limitations: Time consuming Hard to standardize Inter- and Intra-laboratory variability RBCs from different species are used (turkey, guinea pig, human, chicken, horse, goose) RBC lots can be variable Results can be affected by antibody source Interpretation is subjective Low sensitivity to detect antibodies against avian viruses (Stevens J. CDC. Geneva, 2014)

28 The solutions Alternatives proposed to improve: -Sensitivity -Accuracy -Sample throughput -Reproducibility between labs Bead formats Solid matrices

29 -Bead formats (surrogate RBC) Purified Synthetic

30 -Bead formats (surrogate RBC) Very promising results Reproducible Size of the bead is critical Bead stability is variable Beads are affected by buffer Glycan choice

31 -Solid matrices Glycan coated bead or RBC vesicle Solid phase + synthetic glycans Solid phase + specific Abs Solid phase + viral HA

32 The solutions Virus or recombinant protein Synthetic sialyl-glycans RBC membrane vesicles RBC membrane fragments Purified proteins with unspecified glycan composition Detection options Fluorescence Chemiluminescence FRET Direct binding

33 Conclusions Evolution lead changes generating new influenza viruses Mutations of HA protein generate antigenic drift (specially AH3N2) These changes affect the performance of characterization tests Mutations (drift) may be introduced as part of egg-based vaccine production

34 Conclusions New methods (or improved) have to be designed to assess serologic characterization of A(H3N2) (synthetic carbohydrates, surrogate RBC ) There are several options (ongoing) to improve HA/HAI assays but also several challenges! Keep it simple Sensitivity/reliability/reproducibility Applicable to all subtypes Keeping costs down

35 Conclusions More studies have to be developed sharing viruses increase the chances of better approaches

36 GRACIAS!