Live Attenuated Influenza Vaccine. I. Background and Seasonal Vaccine

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1 Live Attenuated Influenza Vaccine I. Background and Seasonal Vaccine

2 Influenza infection stimulates multiple arms of the immune system Systemic antibody to HA and NA, and multiple internal proteins Mucosal antibody Multiple cellular responses Long-lived protection against reinfection

3 Attenuated influenza vaccine These data (results of human challenge studies) permit one to conclude that inhalation of influenza virus, attenuated by protracted passage through ferrets and mice, may be worthy of attention as a means of increasing the quantity of protective antibodies in human beings, and perhaps also, of enhancing their resistance to a subsequent influenza infection. A.A. Smorodintseff, Am. J. Med. Sci. 194: , 1937

4 Potential advantages of live, intranasal vaccination for influenza Immunogenicity advantages Induction of local, mucosal immunity Broadened spectrum of antibody Induction of cellular responses Vaccine delivery advantages Easier mode of administration - no sharps More acceptable to some recipients Manufacturing advantages More efficient production (more doses per egg)

5 Early approaches to development of live attenuated influenza vaccines Chemically mutagenized influenza viruses (e.g., ts-[e] and others) Alterations in NA function (e.g., Alice and Ann strains) Modified Jennerian Approach (e.g., A/Mallard/NY/78) Serial passage in cell culture (e.g., coldadapted, A/Ann Arbor/6/60)

6 Cold-adapted live attenuated influenza viruses Generated by serial passage of a wild-type influenza virus in cell culture at gradually decreasing temperatures Influenza A A/Ann Arbor/6/60 (H2N2) A/Leningrad/137/17/57 (H2N2) A/Leningrad/137/47/57 (H3N2) Influenza B B/Ann Arbor/6/66 B/USSR/60/69

7 Rapid attenuation of new antigenic variants by genetic reassortment PB1 PB2 PA HA NA NP M NS PB1 PB2 PA HA NA NP M NS PB1 PB2 PA HA NA NP M NS ATTENUATED DONOR VIRUS WILD-TYPE ANTIGENIC VARIANT ATTENUATED VACCINE VIRUS

8 Rapid attenuation of new antigenic variants by reverse genetics P B PB2 1 PA HA NA NP M NS PA PB1 PB2 HA NP M NS NA PB 1 PB2 PA HA NA NP M NS ATTENUATED DONOR VIRUS e.g., ca A/AA/6/60 WILD-TYPE VARIANT e.g., A/VN/04/05 H5N1 P B PB2 1 PA HA NA NP M NS ATTENUATED VACCINE VIRUS

9 Properties of cold-adapted master donor viruses (MDV) Three phenotypes Cold-adapted (ca): able to grow at 25 C Temperature-sensitive (ts): restricted replication at 39 C compared to 33 C Attenuation (att): reduced titers in the lower respiratory tract of ferrets and hamsters Reliable attenuation Genes responsible for ca, ts, and att phenotypes are on internal gene segments Genetically stable Multiple mutations contribute to attenuation

10 Genetic basis of attenuation of the A/Ann Arbor/6/60 virus Phenotype of single Gene segment gene reassortant from the A/AA/60 virus TS CA ATT Sequence of gene product AA Sequence position WT CA PB2 PB1 PA TS TS WT WT WT CA ATT ATT ATT Asn Lys Glu Glu Ala Lys Leu Ser Glu Asp Gly Thr Glu Pro Red: Confirmed role in ts phenotype by reverse genetics techniques, Jin Virology 2003

11 Genetic basis of attenuation of the B/Ann Arbor/1/66 virus 11 unique coding changes on 5 gene segments PA gene contributes to attenuation in ferrets as assessed by reassortment experiments Single amino acid change in PA results in phenotypic reversion

12 Trivalent live attenuated seasonal influenza vaccine (FluMist ) Trivalent formulation containing FFU of each component per 0.2 ml dose in sucrose/ phosphate/ glutamate buffer Preservative free Storage 4 C to 8 C Administered by nasal spray, 0.1 ml per nostril

13 Increased risk of medically significant wheezing in children under 2 compared to TIV Belshe 2007 NEJM 356:685

14 Shedding of vaccine virus depends on age

15 Shedding of vaccine virus by children 6-59 months of age 6 mo -23 mo 24 mo. 59 mo. Mallory Vaccine 2011

16 CAIV-T Transmission 197 children aged 8-36 months in day-care setting randomized to vaccine or placebo, cultured daily x 21 days wt Influenza A (H3) co-circulating Influenza B detected in 1/99 placebo Confirmed ca, retains phenotypes Risk 0.58% (95% CI 0, 1.7%) Influenza A detected in 6/99 placebo Confirmed wt in 2 subjects Could not be characterized in 4 subjects Risk (WCS) 2.4% (95% CI 0.13, 4.6%) Vesikari PIDJ 25:590, 2006

17 Potential role of mucosal immunity Protection of the upper respiratory tract Role in otitis media Prevent viral shedding, transmission Intracellular neutralization of viruses Protective mechanisms other than neutralization Local cellular effectors

18 Antibody responses Frequency and magnitude of responses are highest in children > adults > elderly Lower levels are seen in adults than children even if subjects are prescreened for antibody LAIV induces higher levels of mucosal HAspecific IgA than TIV TIV induces higher levels of serum HAI, MN, and HA-specific IgG than TIV

19 Cellular Responses: B cells Flu specific IgG and IgA ASC peak on day 7-12 after either LAIV or TIV ASC are seen in approximately equal numbers following LAIV or TIV in children, but are substantially higher following TIV in adults Development of ASC may be a more sensitive indicator of take than Ab Responses are less frequent in previous recipients of TIV Sasaki 2007 J Virol 81:215

20 Cellular responses: T cells Interferon secreting CD4+ and CD8+ responses seen after both LAIV and TIV Children: TIV and LAIV induce CD4+ cells, only LAIV induced CD8+ and NK Adults: No consistent changes in T cells after either vaccine, high variability Levels of activation markers on cells also differs between vaccines He 2006 J Virol He 2008 JID

21 Differing CD4 and CD8 T cell responses to LAIV and TIV LAIV and TIV responses in 5-9 yr olds Responses to LAIV in children and adults He 2006 J Virol 80:11756

22 Evaluation of the protective efficacy of ca vaccines in adults 35 Culture positive influenza Rate per 1,000 subjects Placebo Cold-adapted Inactivated H1N1 H3N2 Edwards JID 169:68, 1994

23 Pooled results of experimental infection studies in adults Virus shedding Infection Influenza illness TIV CAIV Pooled Odds Ratio (95% CI) compared to placebo Treanor Vaccine 18:899, 1999

24 Cold-adapted influenza vaccine prevents severe febrile illness in working adults Outcome Rate per 1,000 persons per 7- week peak outbreak period Vaccine Placebo % reduction (95% CI) Febrile illness Severe febrile illness Febrile URI (-2.1,20.7) 18.8 (7.4,28.8) 23.6 (12.7,33.2) Nichol JAMA 282:137, 1999

25 Live vaccine provides protection against flu in healthy adults 35 Culture positive influenza Rate per 1,000 subjects Placebo Cold-adapted Inactivated H1N1 H3N2 Edwards JID 169:68, 1994

26 Efficacy of trivalent coldadapted vaccine in children Group No. of subjects (%) with laboratory documented: No. of subjects Influenza A Influenza B Either Placebo (12.0) 37 (7.0) 95(17.8) Vaccine (0.7) 7 (0.7) 14 (1.9) 6 children in the placebo group had both influenza A and B Protective efficacy against A is 95% (CI 95 88%, 97%) Protective efficacy against B is 91% (CI 95 79%, 96%) Belshe NEJM 358:1405, 1998

27 Efficacy against the drift variant, A/Sydney/95 No. of subjects (%) with illness due to influenza A/H3N2 viruses that were: Group No. of subjects Wuhan -like Sydney -like Either Vaccine (0) 15 (2) 15 (2) Placebo (1) 51 (12) 55 (12) Protective efficacy against Wuhan = 100% (54%, 100%), efficacy against Sydney = 86% (75%, 92%) Belshe J. Pediatr. 136:168, 2000

28 Establishing a correlate of protection? Forrest 2008 Clin Vaccine Immunol 15:1042

29 Cold adapted influenza vaccine in elders Replication of the vaccine virus is relatively restricted, even in those with low levels of antibody Well tolerated, even in presence of lung disease Immunogenicity is poor Nasal antibody no greater than seen with inactivated vaccine

30 Efficacy of LAIV in healthy adults 60 and older (mean age 69) Incidence (%) in Antigenically similar All H1 H3 B LAIV (1567) P (1569) VE (95% ci) 42.3 (21.6, 57.8) (32.1, 67.2) (-113, 42.7) Any isolate All H1 H3 B (20.9, 57.1) (32.1, 67.2) -9.7 (-108, 42) Devilliers 2010 Vaccine 28:228

31 Protective efficacy of combined IIV and LAIV vaccination in nursing homes Laboratory confirmed influenza Influenza-like lllness Vaccine Placebo Respiratory illness Incidence (%)

32 Evaluation of combined TIV and LAIV in patients with COPD Subjects 50 and older with COPD Relative VE for any influenza 16% (-22,43) Relative VE for H3 26% (-17, 53) Relative VE for B -5% (-113, 48) Vaccine was generally well tolerated Gorse, Vaccine 2003

33 Live vaccine is especially efficacious in unprimed, immunologically naïve subjects 6 5 Relative protective efficacy of CAIV compared to TIV 89.2 (67.7 to 97.4) 79.2 (70.6 to 85.7) 16.1 (-7.7 to 34.7) Antigenic relatedness of vaccine and circulating virus Attack rate (%) Unmatched Matched 1 0 CAIV TIV CAIV TIV CAIV TIV A/H3N2 A/H1N1 B Belshe et al NEJM 356:685-96, 2007

34 Comparative efficacy of CAIV and TIV in children 6-72 mo with history of frequent URI CAIV-T (n = 1,050) TIV (n = 1,035) Antigenically related (21.6, 72.2) Any 52.4 (24.6, 70.5) Cases Cases Any H1N1 H3N2 B 0 Any H1N1 H3N2 B Ashkenazi, 2006 PIDJ 25:870

35 Live vaccine may be less efficacious than inactivated vaccine in adults 7 Flu B Flu A 6 Cumulative incidence (%) % (37, 92) 57% (-3, 82) 1 0 TIV CAIV Placebo Ohmit, et al. NEJM 355:2513, 2006

36 Live vaccine may be less efficacious than inactivated vaccine in adults 12 Flu B Flu A Cumulative incidence (%) % (46, 81) 36 (0, 59) 0 TIV CAIV Placebo Mont, et al. NEJM 361:1260, 2009

37 Evaluation of TIV and LAIV in military recruits Wang, JAMA 2009

38 Summary: Seasonal LAIV Infectivity and immunogenicity probably depend on prior exposure and susceptibility Most effective in young children Safe and well tolerated in all age groups and in individuals with chronic conditions Wheezing remains a concern Limitations in indicated groups are based on lack of evidence of efficacy, not on concerns about safety Effectively induces mucosal antibody and T cells Immune responses more robust in young No correlate of protective immunity exists Effective for prevention of influenza in children, adults, and the elderly In direct comparisons, better than TIV in children, probably less effective in adults

39 Live Attenuated Influenza Vaccine 2. Pandemic approaches and alternative live vaccines

40 Potential use of live vaccines for pandemic influenza Conventional CAIV are highly immunogenic in susceptible populations Higher levels of protection Potential use of low doses Induction of mucosal immunity might reduce shedding, halt transmission Broader cross protection But.. Overattenuation is possible Concerns about transmission

41 Adverse consequences of use of a live vaccine for pandemic flu H5 N1 PB1 PB2 PA HA PB1 PB2 PA HA H3 N2 NA NP M NA NP M NS NS Deployed Live Pandemic H5N1 Vaccine Conventional Human wt H3N2 virus

42 Adverse consequences of use of a live vaccine for pandemic flu H5 N1 PB1 PB2 PA HA NA NP M NS H5 N1 PB1 PB2 PA HA NA PB1 PB2 PA HA NA NP M NS H3 N2 NP M Deployed Live Pandemic H5N1 Vaccine NS Conventional Human wt H3N2 virus Artificially Created Pandemic

43 Generation of reassorted viruses in humans PB1 PB1 PB2 PA HA NA NP M + PB1 PB2 PA HA NA NP M PB2 PA HA NA NP M NS 5 M only NS NS CA WT PB1 PB2 PA HA 2 NS only NA 340 clones NP M NS 8/340(2.8%) reassortants PB1 PB2 PA HA NA NP M NS 1 PA + M Youngner et al J Clin Microbiol 32:

44 Issues related to use of LAIV prior to a pandemic Vaccine viruses could be spread to contacts and transmitted throughout the population Reassortment could occur with wild-type viruses and regenerate virulent pandemic virus Prevention strategies: Studies only done in summer months Subjects kept in isolation until PCR negative Staff vaccinated with seasonal vaccine, use of protective equipment

45 LID program to generate candidate pandemic LAIV Prioritized HA subtypes based on epidemiology, risk (H5, H7, H9, H2, H6) Antigenic relatedness to other members of the subtype and potential to induce broadly reacting antibody Replicative properties of candidate vaccines and evaluation in animal models Sensitivity to oseltamivir

46 A/chicken/Hong Kong/G9/97 H9N2 % with virus shedding by: % with 4-fold response by Group N CX PCR HAI MN IgG EIA H9N2 sero (+) Dose 1 Dose (33*) 11 0 (67*) 0 33 (67*) H9N2 sero (-) Dose 1 Dose (92*) (79*) (50*) * % responding comparing day 0 and day 56 Karron 2009 JID 199:711

47 A/Vietnam/1203/2004 (H5N1) A/Hong Kong/213/2003 (H5N1) % with virus shedding by: % with 4-fold response by Group N CX PCR HAI MN IgA EIA VN/2004 Dose 1 Dose (10*) 0 0 (5*) (52*) HK/2003 Dose 1 Dose (0*) 0 0 (0*) 6 13 (18*) * % responding comparing day 0 and day 56 Karron 2009 Vaccine 27:4953

48 A/teal/Hong Kong/W312/97 (H6N1) A/ck/BC/CN-6/2004 (H7N3) % with virus shedding by: % with 4-fold response by Group N CX PCR HAI MN IgA EIA HK/1997 Dose 1 Dose (5*) 5 0 (5*) (24*) BC/2004 Dose 1 Dose (67*) (48*) (71*) * % responding comparing day 0 and day 56 Talaat 2011 Vaccine 29:3144 Talaat 2009 Vaccine 27:3744

49 Antibody secreting cells on day 7 after H7N3 LAIV

50 Conclusions Despite lack of prior immunity, ca avian reassortants are substantially restricted in replication in adult humans Mutations associated with receptor binding may play a role in restricted replication Strong antibody responses have not been detected but assays are not really validated Markers of B cell activation may be detectable in peripheral blood following vaccination

51 Alternative approaches to development of LAIV Deletion of some or all of the NS1 protein Deletion of M2 cytoplasmic tail Polymerase mutations Replacement of HA cleavage site with elastase motif

52 Multifunctional roles of NS1 in influenza replication Hale et al J Gen Virol 89:2359, 2008

53 NS deletion mutants with truncated NS1 and intact NEP Levels of attenuation in animal models depends on NS1 length rwt wt att Solorzano et al J Virol 79:7535, 2005

54 Replacement of the coding sequence of influenza B HA and NA with those of influenza A virus PB1 PB2 PA HA NA NP M NS PB1 PB2 PA HA NA NP M NS delns Influenza B virus Harimoto J Virol 77:8031, 2003 Flaudorfer J Virol 77:9116, 2003 delns Influenza B virus with influenza A HA and NA HAI J Virol 85:6232, 2011

55 Multiple vectors for delivery of influenza antigens Adenoviruses Used extensively as vaccines in the military Poxviruses (fowlpox, MVA) Limited to single cycle of replication, used extensively for smallpox vaccination (MVA) Alphavirus replicons Replication defective, target dendritic cells, self adjuvanting Newcastle Disease Virus (NDV) Mucosal administration, highly attenuated

56 Summary. Pandemic LAIV Despite lack of prior immunity, ca avian reassortants are substantially restricted in replication in adult humans Mutations associated with receptor binding may play a role in restricted replication Strong antibody responses have not been detected but assay sensitivity is not clear ASC may be detectable in peripheral blood following vaccination Lack of clear immune correlates for LAIV makes assessment of potential role difficult