Studies of Echovirus-12 in Volunteers: Determination of Minimal Infectious Dose and the Effect of Previous Infection on Infectious Dose

Abstract

A two-part study of echovirus-12 was done in volunteers. In the first part the human infectious dose of the virus was determined in 149 healthy adults with undetectable serum antibody, each of whom drank 0-330,000 plaque-forming units (pfu) of virus in 100 ml of nonchlorinated water. Infection was defined as fecal shedding of virus or significant (fourfold or greater) increases in serum antibody titer. The HID50 (i.e., the dose required for infection of 50% of the volunteers) was 919 pfu. Through statistical analysis of the data by probit transformation, a 1% human-infectious dose of 17 pfu was predicted. These results were used in the second portion of the study to determine the effect of previous infection on the infectious dose. Previously infected volunteers (those with neutralizing serum antibody) were given a dose of echovirus-12 (1,500 pfu) that had been found to infect 60% of persons with undetectable serum antibody. The presence of serum antibody caused no significant change in the percentage of volunteers infected by this dose. Furthermore, the concentration of serum antibody did not affect the rate of infection or the duration of viral shedding. These results indicate that previous infection with echovirus-12 does not provide lasting protection against reinfection.

Risk Assessment in Shellfish-Borne Outbreaks of Hepatitis A

“…Of note, 50% of the positive samples were harvested during the January-June 2008 period (cases per 100,000 inhabitants: 13.3), 33% during July-December 2007 (cases per 100,000 inhabitants: 11.6), and the remaining 17% during January-June 2007 (cases per 100,000 inhabitants: 3.3). Addition- (34,36). Exposure dose was figured by applying the formula and parameters described in Table 1.…”

“…Due to the lack of a reliable cell system for the recovery of wild-type HAV, standardized quantitative molecular approaches, including appropriate quality assurance and quality control measures to assess the efficiency of critical steps in virus analysis, open the possibility of producing consistent and accurate exposure data (11). Additionally, the lack of an actual dose-response model for HAV makes it necessary to apply models developed for other enteric viruses (21,25,36,39).…”

My Role in the Discovery and Classification of the Enteroviruses

“…The infectious dose of a wild-type (unattenuated) nonpolio enterovirus administered by the natural route to a large number of susceptible individuals has also been determined under carefully controlled conditions in an isolation facility. The virus chosen for the study was echovirus 12, since it has not been associated with serious human illness (95). The HID 50 was 919 PFU.…”

Nucleotide Sequences of IRES Domains IV and V of Natural ECHO Virus type 11 Isolates with Different Replicative Capacity Phenotypes

“…ECV11 Gregory and ECV12 Travis references strains were kindly obtained from the Virology Department of the Faculty of Medicine of Saint Etienne, France. Travis ECV12 prototype and strain belonging to serotype ECV2 (MON-ECV2) were chosen and included for comparison in this study because of their relatively avirulent phenotype as demonstrated in surveys of ECV prevalence from clinical samples and human challenge studies [46,47].…”