Immunity to Human Cholera in Bangladesh
Condition: Cholera
MeSH terms: Cholera
Study type: Observational

Summary: 
      Cholera is a severe diarrhea illness caused by bacteria. The purpose of this study is to
      better understand how the immune systems of people in Dhaka, Bangladesh, fight infection with
      cholera. Understanding immune responses that influence the outcome of infection with cholera
      can assist in the development of more effective cholera vaccines. The International Center
      for Diarrheal Diseases Research, Bangladesh (ICDDR,B) will enroll in this study 75 patients
      with acute cholera and 250 of their household contacts. Individuals ages 2-60 years are
      eligible. Study participation will last 1 year for cholera patients and 30 days for household
      contacts. Participants will come to the ICDDR,B for 3 (household contacts) or 4 (cholera
      patients) study visits, and field workers will visit them at home at other times. For all
      participants, blood samples will be taken at each of the ICDDR,B visits. Household contacts
      will have rectal swabs taken at 2 ICDDR visits and during field worker visits.
    

Detailed description: 
      The purpose of this study is to investigate protective immunity to human cholera in Dhaka,
      Bangladesh. Immune responses to Vibrio cholerae are poorly understood and have not been
      extensively studied in an endemic setting such as Bangladesh. Understanding systemic and
      mucosal immune responses that influence the outcome of infection with V cholerae can assist
      in the development of more effective cholera vaccines. Identifying host factors, such as
      human genetic variations or nutritional status, that affect the outcome of infection with V
      cholerae can lead to an improved understanding of disease pathogenesis and better treatment
      modalities. One of the likely key determinants of protection following either natural cholera
      or vaccination is the duration of immune responses to key antigens, particularly at the
      mucosal surface. This study proposes to assess the duration of immune responses in a group of
      75 cholera study participants over the course of 1 year of follow-up and to correlate
      baseline immune responses in 250 household contacts of the index patients, with protection
      from disease over the subsequent 30 days. The researchers will assess the duration of
      immunity in serum to known cholera virulence factors, including the serum vibriocidal
      antibody and antibodies specific for LPS, cholera toxin, B subunit (CtxB), and TcpA. The
      researchers will also measure antigen-specific memory B cells circulating in human blood,
      which has previously been used to examine the longevity of B cell immunologic memory
      following various infections and vaccinations. The objectives of this study are to determine
      genes and proteins expressed by V. cholerae during human infection; determine which V.
      cholerae proteins are immunogenic during human cholera infection in Bangladesh; assess the
      duration of immune responses to V. cholerae antigens following an episode of cholera;
      determine which anti-V. cholerae immune responses are protective on exposure to cholera in
      household contacts; and evaluate selected host factors that influence the development of
      immune responses following cholera, or susceptibility to symptomatic cholera following
      exposure in household contacts. A total of 325 study participants (75 index patients with
      acute cholera and 250 of their household contacts) will be enrolled. Index study participants
      will be recruited from among patients presenting with acute cholera to the International
      Center for Diarrheal Diseases Research, Bangladesh (ICDDR,B) hospital in Dhaka, Bangladesh.
      Any individual with acute cholera between the ages of 2 to 60 years, inclusive, without a
      severe complicating illness, and any household contact of the cholera patients between the
      ages of 2 and 60 years, inclusive, is eligible for enrollment in this study. The length of
      participation for each study participant will be 1 year for acute cholera index patients and
      30 days for their household contacts. For cholera patients, study physicians will perform an
      initial assessment and collect blood at various time points over 1 year. Study participants
      (cases and household contacts) will come to the ICDDR,B for blood collection. On Study Days 3
      through 6 and 8 through 10, a trained field worker will visit the household contacts to
      collect information about symptoms and treatment of diarrhea and to obtain rectal swab
      samples. Household contacts will come to the ICDDR,B on Days 2 or 3, and 7 (range 6-9) for a
      questionnaire, rectal swab, and blood drawing. Questionnaires will be filled out upon
      enrollment and at each study visit.
    

Time perspective: Prospective
Keywords: cholera, Vibrio cholerae, diarrhea, Bangladesh, children