Susceptibility of Human Volunteers With Different Histo-Blood With Different Histo-Blood Group Antigens to Norovirus
Condition: Healthy Adults
MeSH terms: Disease Susceptibility
Study type: Interventional
Phase: Phase 1

Summary: 
      Objectives: To evaluate the role of human histo-blood group antigens in susceptibility to
      Norovirus infections.

      Description of Study Design: Healthy volunteers with different blood types and low antibody
      titers to the challenge strain will be challenged orally with a Norovirus in the CCCR
      inpatient facility. Subjects with resistant (non-secretors) or susceptible (secretors (of
      either A, B or O blood group)) to the challenge strain will be recruited. The challenge study
      will be conducted in two groups of twenty, each with approximately ten secretors and ten
      non-secretors. Three additional subjects per group will serve as alternates in the event that
      any of the study subjects are unavailable or become ineligible at the time of the inpatient
      study. Subjects will be monitored daily in the isolation facility for at least five days
      following this challenge for daily clinical and virological evaluations. Subjects will return
      to the investigational site for evaluation the day after discharge from the inpatient unit
      and about 30 days (28-35 days) post challenge.

      Study Endpoints: Norovirus infection as assessed by viral shedding, seroconversion and
      clinical illness assessed by the duration and severity of symptoms
    

Detailed description: 
      Noroviruses are single-stranded, positive-sense RNA viruses that cause acute gastroenteritis
      in humans. The prototype Norwalk virus (NV) was identified in a large outbreak of acute
      gastroenteritis in an elementary school in Norwalk, Ohio, in 1968. Since then, many strains
      have been described and named by the locations of their first isolation. Genetically,
      Noroviruses belong to one of four genera within Caliciviridae (CV). Phylogenetic analysis has
      shown that the Norovirus genus is divided into five genogroups and each genogroup can be
      further divided into genetic clusters; at least 30 genetic clusters of Noroviruses have been
      identified.

      Noroviruses have been recognized as the most important cause of non-bacterial epidemics of
      acute gastroenteritis, affecting individuals of all ages, in both developing and developed
      countries. Such outbreaks usually have high attack rates and have occurred in child care
      centers, schools, restaurants, summer camps, hospitals, nursing homes, ships (both civilian
      and military) as well as deployed military troops. The viruses are highly contagious and are
      able to survive in the environment for extended periods of time. They are spread by contact
      with environmental surfaces and person-to-person transmission. Noroviruses normally cause
      moderate-to-severe diarrhea and the disease is often incapacitating and can be fatal in the
      young and elderly. The most important public health concern is that Noroviruses can cause
      large water- and food-borne outbreaks, resulting in the virus being classified as a Category
      B agent.

      Noroviruses have also been implicated in several military outbreaks. The "Desert Shield
      virus" (DSV) isolated in US troops in the 1991 Gulf War was subsequently identified as a
      Norovirus. Similarly the recently reported "mysterious" attacks of acute gastroenteritis
      affecting the British troops in Afghanistan were also caused by a Norovirus. Large outbreaks
      of Norovirus-associated gastroenteritis are common on US Navy ships, similar to those that
      occurred on board cruise ship lines. Surveillance of acute gastroenteritis on board five US
      Navy combat ships in 1998-1999 showed that all the ships experienced large outbreaks of
      Norovirus acute gastroenteritis during their deployment in the Pacific and Indian Oceans,
      following port visits. Because of the rapid spread of the disease, many departments and units
      on board the ships were unable to function during the peak of the outbreaks.

      Noroviruses are difficult to study because: 1) they are genetically and antigenically highly
      diverse and multiple strains with distinct genetic identities co-circulate in the same
      communities, making diagnosis and disease control extremely difficult; and 2) the virus
      cannot be cultivated in cell culture and 3) no small animal model for studying Noroviruses
      exists. The molecular cloning of the prototype Norwalk Virus (NV) in 1990 by one of the
      co-investigators of this application has allowed rapid progress in studying Noroviruses and
      other genera; however, many issues on Norovirus infection, pathogenesis, immunology and host
      range remain unknown.

      The discovery of Norovirus receptors provides new opportunities to evaluate the pathogenesis
      and epidemiology of Noroviruses. A host genetic factor involving Norovirus infection was
      originally suggested by many researchers before the cloning of Noroviruses in the 1990s
      because about 20-30% of individuals who did not have antibodies against Noroviruses were
      never infected following a challenge with NV, and in outbreaks, individuals who remained
      healthy were clustered in families that had the same exposure to Noroviruses as the ill
      families. Further, pre-existing antibodies against NV were not protective against NV
      infection, while individuals who had high levels of antibodies against NV were more
      susceptible to NV than individuals who did not have the antibodies. These observations
      indicate that, in addition to immune responses, there must be another factor(s) that controls
      the host-specificity of Norovirus infection.

      We recently discovered that Noroviruses recognize human histo-blood group antigens as
      receptors. Using recombinant capsid proteins from different Noroviruses representing
      different genetic clusters, we have identified four binding patterns of Noroviruses to human
      histo-blood group antigens, which are defined by the host Lewis, secretor and ABO blood
      types. This finding provides a new approach to develop strategies to control the disease.
      Specifically, if Noroviruses rely on the histo-blood group antigens on the surfaces of the
      intestinal epithelial cells as receptors, a compound that inhibits the interaction between
      the virus and receptors could be developed as an antiviral drug for Noroviruses. This finding
      provides the basis for this protocol which seeks to confirm the relationship between specific
      Norovirus susceptibility and specific histo-blood group antigen presence as well as establish
      a model to evaluated future interventions (drugs and vaccines).

      The specificity of the NV interaction with the sugar moieties of histo-blood group antigens
      was shown by specific blocking of the binding by human milk from a secretor, by monoclonal
      antibodies specific for secretor human blood-group antigens (HBGAs), by synthetic
      oligosaccharide conjugates containing secretor antigens, and by treatment of the tissues with
      a1,2 fucosidase. NV also binds to differentiated CaCo2 cells and differentiated CaCo2 cells
      express human histo-blood group antigens. Transfection of Chinese Hamster Ovary (CHO) cells
      with a a1,2-linked fucosyl-transferase cDNA allowed attachment of NV virus-like particles
      (VLPs). The bound rNV VLPs were internalized following incubation of the cells at 37oC.

      To further investigate the association between secretor status and susceptibility to Norwalk
      virus (NV), we collaborated with Dr. Christine Moe at Emory University's School of Medicine
      on a volunteer challenge study. This study utilized the prototype NV, the first Norovirus
      strain to be used for human challenge studies. Saliva samples from 77 NV-challenged
      volunteers were tested for secretor status and for NV-binding. Fifty-five (71%) of the 77
      volunteers were secretors. Among the 55 secretors, 34 (62%) were infected with NV following
      challenge and saliva from 41 (75%) bound NV recombinant VLPs. None of the saliva samples from
      the 22 non-secretor volunteers bound NV virus-like particles (VLPs) and none of them became
      infected following NV challenge; strongly suggesting that the susceptibility to NV is
      determined at least in part by the ability of the host to bind the norovirus strain.

      More recently we performed a study to determine whether other strains of Noroviruses have a
      similar pattern of host-specificity and have extended the binding patterns to 7 based on
      examination of fourteen Noroviruses. The 7 patterns have been classified into two groups
      according to their interactions with three major epitopes (A/B, H and Lewis) of HBGAs: the
      A/B binding group and the Lewis-binding group. Strains in the A/B binding group recognize the
      A and/or B and H antigens, but not the Lewis antigens, while strains in the Lewis-binding
      group react only to the Lewis and/or H antigens. This classification also resulted in a model
      of the Norovirus/HBGA interaction, in which a maximum of two binding sites within a receptor
      binding interface are involved in NV/HBGA interaction. The A, B and H side chains are
      responsible for binding by the A/B binding strains while the Lewis epitopes are responsible
      for the Lewis binding strains. Phylogenetic analyses showed that strains with identical or
      closely related binding patterns tended to be clustered, but strains in both binding groups
      can be found in both genogroups I and II. Our results suggest that Noroviruses have a wide
      spectrum of host range and human HBGAs play an important role in Norovirus evolution.

      Since human Noroviruses cannot be cultivated in vitro or infect animals, it is necessary to
      perform human volunteer challenge studies to study the pathobiology of the infection. The
      study will further the concept that Norovirus has a narrow host range which is fundamental in
      the pathogenesis and immunology of Noroviruses. Additionally, we recently have identified
      more than a dozen compounds that specifically block Norovirus attachment to their receptors.
      The human challenge study should also establish a model that can be used in the evaluation of
      these new compounds in regards to their capacity to block virus replication (anti-viral
      drug). Furthermore, our study will re-evaluate whether acquired immunity is an independent
      factor in Norovirus infections which may provide additional information in host immunity
      potentially useful in vaccine development. Finally, the study will allow for banking of the
      Norovirus challenge strain by collecting the diarrheal stools passed by the study subjects.
      Banking of additional specimen, as mentioned above, is critical for future clinical trials
      because the virus cannot be cultivated in vitro and must be isolated from humans infected
      with the virus.

      A specific challenge study would only use one challenge strain and any challenge strain used
      in human clinical trials would have a separate IND and FDA approval prior to administration
      to subjects.
    

Intervention name(s): Norovirus
Intervention type(s): Biological
Intervention description(s): Norovirus challenge pool administered to each subject
Other intervention name(s): Norovirus challenge pool
Allocation: Non-Randomized
Intervention model: Single Group Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)