2019 EIS conference

Publication date from document properties.eis-conference-2019-508.pdf2019618

Mechanisms of GII.4 norovirus antigenic variation and evolution

Noroviruses infect an estimated 21 million people annually in the United States, resulting in ~70,000 hospitalizations and ~800 deaths. These viruses are easily transmitted among people in close proximity, including healthcare and educational settings, cruise ships, military environments, and restaurants. Norovirus symptoms include vomiting and diarrhea over a period of 24-72 hours, but life-threatening or chronic infections can develop in infants and very young children, the elderly and immunocompromised individuals. Unfortunately, there are no licensed norovirus therapeutics or vaccines currently available. One factor complicating vaccine and therapeutic design for noroviruses is antigenic variation in GII.4 norovirus, which account for over 70% of all outbreaks. Every 2-4 years the predominant circulating GII.4 strain is replaced by a new emergent strain. In predominant GII.4 strains, genetic changes are most prevalent in continuously evolving areas of the capsid P2 domain and correlate with antigenic changes. This suggests that GII.4 norovirus strain emergence is driven by changes in neutralization epitopes as a result of escaping herd immunity to the previous strain. Therefore, effectively designed therapeutics and vaccines must be broadly active or easily reformulated to account for the antigenic properties of emergent viruses. Our work aims to define the mechanisms that drive genetic changes leading to antigenic changes in GII.4 noroviruses. In Chapter 2, we use structure-guided approaches to map epitope A, the immunodominant GII.4 blockade (potential neutralizaton) epitope. Chapter 3 characterizes antigenic changes between two successive GII.4 strains, GII.4-2009 New Orleans and GII.4-2012 Sydney. In Chapter 4, we investigate the antigenic change that occurs within an individual chronically infected with norovirus over time, map the varying epitopes and compare the degree of change with population-wide changes. We also propose that broadly-blocking GII.4 human monoclonal antibody 71.4 is a potential treatment for chronic norovirus infection. Chapter 5 proposes a VLP-based vaccine platform that utilizes chimeric particles to induce a broadly-blocking immune response against multiple GII.4 strains. These GII.4 norovirus studies have allowed us to identify major determinants of antigenic change in GII.4 noroviruses that will allow for rapid diagnostic identification of new epidemic strains and direct the rational development of norovirus therapeutics and vaccines.Doctor of Philosoph

Risks and benefits of drinking water treatment : focusing on child health and prenatal development

Drinking water is our most important food item and its access is indispensable for a wellfunctioning society. Recent Swedish water-borne outbreaks have demonstrated a system vulnerability and a clear need for improved knowledge on how variations in drinking water quality affects our health. This thesis explores this topic and consists of two large-scale epidemiological studies. The specific objectives were to i) obtain data on drinking water consumption patterns among adults, ii) assess whether changes in drinking water treatment and/or raw water source–aiming to increase pathogen reduction–affected the risk of gastrointestinal illness (GII) and iii–iv) assess if gestational exposure to by-products from drinking water chlorination war associated with the risk of adverse reproductive outcomes. In a longitudinal cohort, we collected repeated information on tap water consumption and GII episodes via a monthly SMS among 5,200 participants during several periods in 2012-2016. The study was conducted in two parts of Sweden, in populations of neighbouring municipalities. In Paper I, we found that 99.8% of adults were consumers of cold tap water, while the consumption of bottled water was low. This lends support to the use of large register-based studies to assess the associations between drinking water exposures and health. In Paper II, we assessed if changes in municipal drinking water production and/or of raw water source affected the risk of GII. These changes encompassed either switching ground water treatment plant, changing from a surface to a ground water treatment plant or switching the surface water treatment plant and raw water source, all resulting in increased pathogen reduction in the drinking water. We observed no differences in the risk of GII among adults, however, among children, a 24% relative risk reduction in GII was observed after switching surface water treatment plant and raw water source. The indications that children are the most sensitive population to drinking water related GII are in line with previous findings. In a nationwide register-based study, we assessed whether gestational exposure to chlorination by-products, trihalomethanes (TTHM), was associated with small for gestational age (SGA), preterm delivery or congenital malformations. We included more than 620,000 children born during 2005–2015 of mothers residing in Swedish localities (≥10 000 inhabitants) and where information on trimester specific TTHM exposure was available. The exposure was categorized into no chlorination, 15 μg TTHM/L and stratified by treatment (hypochlorite and chloramine). In Paper III, we found indications of a dosedependent multivariable-adjusted association of TTHM with risk of SGA in areas using hypochlorite, odds ratio (OR) 1.20 (95% confidence interval [CI]: 1.08-1.33) when comparing the highest exposed population to the unexposed. In Paper IV, TTHM was dosedependently associated with malformations, but only in areas using chloramine. Comparing the population with highest exposure to the unexposed, ORs of 1.82 (95% CI: 1.07–3.12), 2.06 (95% CI: 1.53–2.78), 1.77 (95% CI: 1.38–2.26) and 1.34 (95% CI: 1.10–1.64) were seen for malformations of the nervous system, urinary system, genitals and limbs, respectively. The findings indicate that chlorination by-products may be associated with several adverse reproductive outcomes. Congenital malformations linked to chlorination by-product from chloramine use has not previously been highlighted and needs further attention

Emerg Infect Dis

Emerging Infectious Diseases is providing access to these abstracts on behalf of the ICEID 2022 program committee (http://www.iceid.org), which performed peer review. ICEID is organized by the Centers for Disease Control and Prevention and Task Force for Global Health, Inc.Emerging Infectious Diseases has not edited or proofread these materials and is not responsible for inaccuracies or omissions. All information is subject to change. Comments and corrections should be brought to the attention of the authors.Suggested citation: Authors. Title [abstract]. International Conference on Emerging Infectious Diseases 2022 poster and oral presentation abstracts. Emerg Infect Dis. 2022 Sep [date cited]. http://www.cdc.gov/EID/pdfs/ICEID2022.pdf2022PMC94238981187

Computational and Molecular Biology Approaches to Viral Replication and Pathogenesis

The primary objective of this dissertation was to combine the power of bioinformatics with synthetic genomics, reverse genetics, and molecular genetic approaches to generate a platform technology, with which to empirically test well-informed hypotheses towards understanding complex mechanisms of viral pathogenesis and replication. This integrative strategy was used to: 1) identify unique sequence signatures that were associated with aberrant or altered gene function, focusing on replicase and structural proteins of the Coronavirus family and the capsid protein of the Norovirus family; 2) use these sequence signatures to generate hypotheses and predictions about gene function or evolution; and then 3) empirically test these models using reverse genetics, synthetic biology, molecular genetics, and biochemistry in the laboratory setting. Applying this integrative strategy allowed us to generate three informative models. First, we generated an informative model for the pleiotropic role of a Coronavirus non-structural protein 10 in replication and proteolytic processing, by demonstrating that this protein regulates RNA transcription during replication, in addition to an essential role in polyprotein processing. Second, we demonstrated that the receptor-binding domain of the Coronavirus spike protein is the minimal domain requiring adaptation for host range switching, which helps explain the evolutionary epidemiology of SARS-CoV emergence from zoonotic reservoirs. And finally, we generated an informative model for the molecular mechanisms governing the persistence of the GII.4 noroviruses in human populations, whereby we demonstrated that these viruses persist by evolving unique epitopes on the capsid protein surface to circumvent herd immunity and mediate receptor switching

Norovirus immunobiology and vaccine design

Noroviruses are a genus of 40+ diverse positive polarity RNA viruses that cause approximately 23 million cases of gastroenteritis annually in the United States alone. The lack of a cell culture system or small animal model in which to study these human pathogens has hindered development of norovirus vaccines since their discovery in 1972. Because noroviruses have a very low infectious dose and high transmissibility, vaccines would be beneficial for employees and patrons of institutionalized settings such as hospitals, nursing homes, and schools, where outbreaks frequently occur. To begin to unravel how norovirus exposure affects the adaptive immune response, we utilized Venezuelan equine encephalitis virus replicons as immune adjuvants and delivery vectors for norovirus antigens to demonstrate induction of B cell and T cell responses in protective immunity to noroviruses in mice. Norovirus-like particle (VLP) vaccination induces robust IgG and IgA responses in serum, feces, and tissues that can block norovirus binding to ABH histo-blood group antigen receptors in a strain-specific manner but have little cross-reactivity to additional norovirus strains. CD4+ T cells are also activated following vaccination to produce large amounts of the anti-viral compound IFN-[gamma] upon stimulation with homologous norovirus VLPs or peptides in vitro. To effect a broader immune response, we vaccinated mice with a cocktail of VLPs from multiple norovirus strains simultaneously resulting in cross-reactive receptor-blocking antibody responses to heterologous strains not included in the vaccine composition. Furthermore, multivalent vaccination did not diminish specificity or quantity of antibody or T cell responses to individual vaccinating strains. Studies with the newly discovered murine norovirus (MNV) revealed that MNV VLP vaccination protects against MNV infection, and both humoral and cellular immunity are involved in clearance of the virus. Furthermore, adoptive transfer of serum but not CD4+ or CD8+ T cells from vaccinated mice completely protected immunodeficient mice from MNV infection, suggesting pre-existing antibodies can prevent establishment of acute infection. Vaccination with multiple human VLPs also provided significant protection against MNV infection in mice, advocating the development of multivalent human norovirus vaccines for cumulative protection against norovirus challenge

Foodborne or pandemic: An analysis of the transmission of norovirus-associated gastroenteritis and the role of food handlers

This study examined the strength of association between food workers and food to norovirus in comparison to bacteria associated with foodborne-related gastroenteritis by whether norovirus had a direct (physical evidence), indirect (statistical evidence), or suspect (neither of the two) association with food or food handlers. The Centers for Disease Control and Prevention considers norovirus to cause the largest number of foodborne-related gastroenteritis cases in the United States. The association of norovirus with foodborne outbreaks through its information data collection form focuses on the food worker as the typical source. Yet, many outbreaks are not foodborne in nature. The gap in the research is the evidence supporting the theory that norovirus transmission is the same as bacterial transmission. A secondary data anaylsis was conducted on the data from the electronic Foodborne Outbreak Reporting System between 1998 and 2006. An odds ratio analysis showed no similarity between proportion of the implicated and nonimplicated numbers of outbreaks from norovirus and those from Salmonella. The odds ratios also showed a stronger similarity between proportions of food handler implicated outbreaks from norovirus than from Salmonella. An analysis showed, though, a significant emphasis was not placed on the food handler but on other indirect routes of transmission of norovirus in outbreaks. The analysis also indicated that norovirus transmission was not mainly through food. Norovirus transmission appeared to be through person-to-person rather than food and had more similarities with pandemic influenza than gastroenteritis-associated bacteria. A change in approach to norovirus by local, state, and federal agencies could have social change implications for prevention, surveillance, and public health programs to reduce infection and outbreaks

2023 EIS Conference

Welcome or welcome back. Four years have passed since our last in-person conference of CDC\u2019s Epidemic Intelligence Service (EIS). The COVID-19 pandemic has been hard on everyone and especially for our public health workforce. The EIS classes of 2018, 2019, and 2020 were remarkable for having completed EIS during the pandemic and while transitioning to virtual training. Thank you to our officers for your service under the most challenging of circumstances. And thank you to our EIS alumni, supervisors, and partners for your service and continued support of the EIS program. We are thankful you are back with us at the EIS conference.The conference is a core element of EIS training. It is an opportunity for EIS officers to refine their scientific communication skills, gain experience responding to questions about their work, and share their stories. For all of us, the conference is an opportunity to learn from their analyses, investigations, and practice of consequential epidemiology.Publication date from document properties.https://www.cdc.gov/eis/downloads/eis-conference-2023-508.pd

Serological humoral immunity following natural infection of children with high burden gastrointestinal viruses

Acute gastroenteritis (AGE) is a major cause of morbidity and mortality worldwide, resulting in an estimated 440,571 deaths of children under age 5 annually. Rotavirus, norovirus, and sapovirus are leading causes of childhood AGE. A successful rotavirus vaccine has reduced rotavirus hospitalizations by more than 50%. Using rotavirus as a guide, elucidating the determinants, breath, and duration of serological antibody immunity to AGE viruses, as well as host genetic factors that define susceptibility is essential for informing development of future vaccines and improving current vaccine candidates. Here, we summarize the current knowledge of disease burden and serological antibody immunity following natural infection to inform further vaccine development for these three high-burden viruses