Correlates of Protection against Enterotoxigenic Escherichia coli

Transcription

1 Correlates of Protection against Enterotoxigenic Escherichia coli Firdausi Qadri Infectious Disease Division Correlates of enteric vaccine induced protection Fondation Merieux, Annecy 22 March, 216

2 Importance of enterotoxigenic E. coli (ETEC) in children in developing countries In Bangladesh, acute dehydrating diarrhea is common and epidemics seen at least two times every year and additionally peaks during natural disasters ETEC is the most common cause of bacterial diarrhea in children 3 years (1-2% of all cases) Repeated ETEC diarrheas can cause malnutrition, growth retardation and stunting

3 Number of ETEC Distribution of ETEC cases in 2% surveillance system of the icddr,b Dhaka Hospital March, 216, 18% of ETEC in the 2% Surveillance system of of the icddr,b hospital

4 Nationwide surveillance on ETEC in Bangladesh carried out in the Upazilla hospitals and other health facilities Study in 7 divisions of Bangladesh 1 sites ( ; ongoing) VC: 5 (1.47%) ETEC: 2 (.59%) VC: Positive : 2 (.43%) ETEC: Positive : 6 (1.28%) VC: 4 (11.83%) ETEC: 15 (4.44%) DMC - VC: 4 (2.48%) ETEC: 9 (5.59%) VC: 24 (4.87%) ETEC: 24 (4.87%) VC: 46 (7%) ETEC: 29 (4.41%) Uttara - VC: 8 (5.1%) ETEC: 7 (4.46%) BITID - VC: 145 (26.8%) ETEC: 23 (4.14%) VC: 26 (5.34%) ETEC: 11 (2.26%) VC: 33 (8.13%) ETEC: 1 (2.46%)

5 Towards bettter understanding ETEC infections and protective mechanisms for vaccine evaluation ETEC diarrheal infections trigger mucosal immune responses which are not easy to study using invasive procedures such as small intestinal biopsies Surrogate markers of local responses can be studied in secretions and in blood to decipher the nature of the B and T cell response The potential destination of circulating antigen specific antibody secreting cells can be investigated by studying the expression of gut homing markers A more targeted immune response can be associated with longer lasting immunity

6 LTB, CFA/I and CS6 specific antibody responses in plasma of Bangladeshi adults with ETEC diarrhea A LTB IgA B CFAI IgA 8 C 4 15 Plasma anti-ltb IgA (ELISA Unit) Study day Fold increase Response(%) D Plasma anti-ltb IgG (ELISA Unit) Study day Fold increase Response(%) D2 D7 D3 D2 D7 D LT or LT/ST ETEC ST ETEC LTB IgG D2 D7 D3 D2 D7 D LT or LT/ST ETEC ST ETEC Plasma anti-cfa/i IgA (ELISA Unit) Study day D2 D7 D3 D2 D7 D3 Fold increase Response(%) E Plasma anti-cfa/i IgG (ELISA Unit) Study day Fold increase Response(%) CFAI group ETEC D2 D7 D3 D2 D7 D CFA/I group ETEC CFAI IgG Plasma anti-cs6 IgA (ELISA Unit) Study day 1 5 Fold increase Response(%) Plasma anti-cs6 IgG (ELISA Unit) F Study day Fold increase Response(%) CS6 IgA D2 D7 D3 D2 D7 D CS6 ETEC D2 D7 D3 D2 D7 D CS6 ETEC CS6 IgG Increased levels of plasma IgA and IgG antibodies at day 7 after onset ETEC diarrhea to different antigens

7 Circulating ASC responses to LTB, CFA/I and CS6 in adult Bangladeshi ETEC patients LTB specific IgA per total Ig ASC (%) LTB IgA CFA/I specific IgA per total Ig ASC (%) CFA/I IgA CS6 specific IgA per total Ig ASC (%) CS6 IgA. d2 d7 d3 d2 d7 d3 LT or LT/ST ETEC ST ETEC. d2 d7 d3 d2 d7 d3 CFA/I group ETEC. d2 d7 d3 d2 d7 d3 CS6 ETEC LTB specific IgG per total Ig ASC (%) LTB IgG CFA/I specific IgG per total Ig ASC (%) CFA/I IgG CS6 specific IgG per total Ig ASC (%) CS6 IgG. d2 d7 d3 d2 d7 d3 LT or LT/ST ETEC ST ETEC d2 d7 d3 d2 d7 d3 CFA/I group ETEC d2 d7 d3 d2 d7 d3 CS6 ETEC Increased circulating ASCs of IgA and IgG isotypes at day 7 after onset of ETEC diarrhea

8 LTB and CF specific memory B cell responses in patients infected with ETEC diarrhea A % LTB-IgA memory B cell per total IgA LTB IgA B % CF-IgA memory B cell per total IgA CF IgA. d2 d3 d2 d3 Responder (%) C % LTB-IgG memory B cell per total IgG LT or LT/ST ETEC ST ETEC d2 d3 d2 d3 Responder (%) LT or LT/ST ETEC LTB IgG ST ETEC. d2 d3 d2 d3 Total Response (%) CFA/I specific (%) CS6 specific (%) % CF-IgG memory B cell per total IgG D CFA/I group and CS6 ETEC d2 d3 d2 d3 Total Response(%) CFA/I specific (%) CS6 specific (%) CFA/I group and CS6 ETEC CF IgG Alam et al., PNTD, 214

9 Avidity indices of LTB (A and D), CFA/I (B and E) and CS6 (C and F) specific IgA and IgG antibodies in plasma in Bangladeshi adults infected with ETEC Avidity indices at day 7 remained elevated up to day 3 in patients infected with ETEC expressing LT or LT/ST, CFA/I and CS6 Alam et al., PNTD, 214

10 Total gut-homing ( 7+) ASC responses in ETEC patients Total IgA spots/ million cell HC Total IgA Day 2 Day 7 Day 3 Total IgG spots/ million cell HC Total IgG Day 2 Day 7 Day 3 Increased levels of gut homing total immunoglobulin (IgA and IgG) were observed at day 7 after onset of ETEC diarrhea Bhuiyan et al., CVI, 215

11 CTB and CFA/I specific IgA and IgG ( 7+) ASC responses were observed on day 7 compared to healthy controls and on study, day 2 and 3 % of CFA/I specific IgA/ total Ig % of CTB specific IgA/ total Ig HC HC d2 CFA/I d7 CTB Day 2 Day 7 IgA d3 IgA Day 3 % of CFA/I specific IgG/ total Ig % of CTB specific IgG/ total Ig HC HC d2 d2 CFA/I CTB 2 d7 d7 d3 IgG IgG d3

12 CS6 specific gut homing ( 7+) ASC responses in ETEC patients % of CS6 specific IgA/ total Ig HC CS6 p=.949 d7 d3 IgA % of CS6 specific IgG/ total Ig HC CS6 d7 IgG d3 CS6 specific IgA and IgG responses were observed at day 7 Bhuiyan et al., CVI, 215

13 Association of gut-homing ASCs with plasma antibody titers in patients with ETEC infection A B CTB IgA ELISA Units at day r =.62 p =.3 CTB IgA/D % of CTB specifiic 7+ IgA ASCs at day 7 CTB IgA ELISA Units at day CTB IgA/D r =.39 p = % of CTB specific 7+ IgA ASCs at day 7 CTB IgG ELISA Units at day C r =.56 p =.2 CTB IgG/D % of CTB specific 7+ IgG ASCs at day 7 CTB IgG ELISA Units at day D CTB IgG/D3 r =.37 p = % of CTB specific 7+ IgG ASCs at day 7 ETEC specific gut-homing IgA and IgG ASCs at day 7 were positively correlated with specific IgA and IgG antibodies on days 7 and 3 post onset of diarrhea Bhuiyan et al., CVI, 215

14 Antigen specific Memory helper T cell responses Stimulation Index, CD3+CD4+ CD45RO+ 1 5 ^ ^.651 Day Antigen HC HC HC HC HC LTB dmlt ST EatA G33D mct

15 Cytokine responses IFN- ELISA IL-13 ELISA IFN-g concentration (pg/ml) IL-13 concentration (pg/ml) day2 day7 day2 day7 day2 day7 day2 day7 day2 day7 day2 day7 LTB dmlt G33D mct LTB dmlt G33D mct

16 Birth cohort study on ETEC and relatedness of ETEC diarrhea with blood group antigen Studies on children in a birth cohort in Mirpur have shown : ETEC infections cause stunting in children. Children with CFA/I ETEC diarrhea are protected from homologous ETEC infection Children with histoblood group AB and A have increased susceptibility to ETEC infection Children with Lewis blood group Le(a+b-) are more susceptible to CFA/I diarrhea Lewis blood group a antigen may be a candidate receptor for ETEC colonization factor CFA/I

17 Studies on ETEC in an urban setting in Mirpur in Dhaka

18 Conclusions ETEC induces memory B cells and high avidity antibodies to LTB and CFs that could mediate anamnestic responses on re-exposure to ETEC and may help in understanding the requirements for designing and following effectiveness of vaccines Need to evaluate whether memory responses, affinity maturation and level of antibodies to these ETEC antigen correlate with protection following vaccination Vaccine studies can now include studies of mucosal gut homing ASC in young children and infants using low volumes of blood using the cell sorting and ELISPOT technique Measurement of ALS/ASC and plasma antibody levels within 5 days of second/booster dose of oral vaccines is critical for gauging the peak of the responses in endemic settings Relationship of ABO and Lewis blood group and genetic factors on response to oral vaccines is an area that needs to be given attention ETVAX vaccine is now in the infant phase with encouraging results of safety in all age groups