Dataset Information

Early-life hepatitis e infection in pigs: the importance of maternally-derived antibodies.

ABSTRACT: Passive immunity (PI), acquired through colostrum intake, is essential for piglet protection against pathogens. Maternally-derived antibodies (MDAs) can decrease the transmission of pathogens between individuals by reducing shedding from infected animals and/or susceptibility of naïve animals. Only a limited number of studies, however, have been carried out to quantify the level of protection conferred by PI in terms of transmission. In the present study, an original modeling framework was designed to estimate parameters governing the transmission of infectious agents in the presence and absence of PI. This epidemiological model accounts for the distribution of PI duration and two different forces of infection depending on the serological status of animals after colostrum intake. A Bayesian approach (Metropolis-Hastings algorithm) was used for parameter estimation. The impact of PI on hepatitis E virus transmission in piglets was investigated using longitudinal serological data from six pig farms. A strong impact of PI was highlighted, the efficiency of transmission being on average 13 times lower in piglets with maternally-derived antibodies than in fully susceptible animals (range: 5-21). Median infection-free survival ages, based on herd-specific estimates, ranged between 8.7 and 13.8 weeks in all but one herd. Indeed, this herd exhibited a different profile with a relatively low prevalence of infected pigs (50% at slaughter age) despite the similar proportions of passively immune individuals after colostrum intake. These results suggest that the age at HEV infection is not strictly dependent upon the proportion of piglets with PI but is also linked to farm-specific husbandry (mingling of piglets after weaning) and hygiene practices. The original methodology developed here, using population-based longitudinal serological data, was able to demonstrate the relative impact of MDAs on the transmission of infectious agents.

SUBMITTER: Andraud M

PROVIDER: S-EPMC4140806 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Early-life hepatitis e infection in pigs: the importance of maternally-derived antibodies.

Andraud Mathieu M Casas Maribel M Pavio Nicole N Rose Nicolas N

PloS one 20140821 8

Passive immunity (PI), acquired through colostrum intake, is essential for piglet protection against pathogens. Maternally-derived antibodies (MDAs) can decrease the transmission of pathogens between individuals by reducing shedding from infected animals and/or susceptibility of naïve animals. Only a limited number of studies, however, have been carried out to quantify the level of protection conferred by PI in terms of transmission. In the present study, an original modeling framework was desig ...[more]

PMID: 25144763

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Project description:Avian metapneumoviruses (aMPV) are a causative agent of turkey rhinotracheitis (TRT). Despite vaccination, cases of TRT outbreaks are frequently reported. Considering that there are aMPV-free areas, a part of turkey poults possess (MDA+) or do not possess (MDA-) maternally derived antibodies (MDA) in the first weeks of life, which is the time of TRT vaccination. Study was undertaken to establish the level of protection against homologue aMPV/A infection, in MDA+ and MDA- turkeys, vaccinated against TRT at the 0 or 14th d of life and infected 14 d later. With the use of ELISA test and qPCR techniques, we have established the level of immune system stimulation after the vaccination and how does it correlate with the level of protection against the aMPV infection. Vaccination of MDA+ turkeys (especially at 0 d of life) resulted in weaker IgA production in upper respiratory tract. In addition, we have demonstrated differences in both humoral and cell-mediated immunity stimulation after infection of vaccinated turkeys. Despite these differences, we have shown that all vaccinated birds were protected against the disease which was determined based on the clinical and histopathological scoring, as well as the level of aMPV/A replication and shedding. Nonvaccinated groups of turkeys displayed typical signs of TRT after infection which indicates that MDA alone are incapable of preventing the disease. Differences in TRT course were recorded between different age groups of nonvaccinated birds. Birds infected at the 28th d of life (especially MDA- birds) developed more severe signs, and the level of aMPV replication was higher than that in birds infected on the 14th d of life. Despite the minor role in alleviating TRT course, MDA seems not to interfere with the vaccination efficacy. It is hard to predict whether the observed immune system stimulation differences between MDA+ and MDA- birds after vaccination can influence the outcome of vaccination efficacy under the field conditions.

Project description:BackgroundStudies of the association between the level of anti-malarial antibody and protection from malaria infection can yield conflicting results if they fail to take into account differences in the malaria transmission rate. This can occur because high malaria exposure may drive high antibody responses, leading to an apparent positive association between immune response and infection rate. The neonatal period provides a unique window to study the protective effects of antibodies, because waning maternally-derived antibodies lead to different levels of protection with time.MethodsThis study uses data from two well-defined infant cohorts in Western Kenya with different burdens of malaria transmission. Survival models were used to assess how the magnitude of maternally derived malaria-specific IgG antibody (to 24 malaria antigens measured using Luminex beads) affected the time-to-first Plasmodium falciparum infection (detected by PCR). In addition, mathematical models were used to assess how the frequency of malaria infection varied between the cohorts with different exposure levels.ResultsDespite differences in underlying malaria incidence in the two regions, there was no difference in time-to-first malaria infection between the cohorts. However, there was a significant period of protection observed in children with high initial MSP1 (42 kDa fragment)-specific antibody levels, but this protection was not observed in children with low antibody levels. Children from the high transmission cohort had both longer initial periods of protection from malaria (attributable to higher initial antibody levels), but more rapid time-to-first-infection once malaria specific maternal antibodies declined below protective levels (attributable to higher exposure rates).ConclusionThis study demonstrates the complex interaction between passive (maternally-derived) immunity and the degree of malaria exposure in infants. Children from regions of high malaria transmission had higher levels of maternally-derived antibodies in early life, which led to a significant protection for several months. However, once this immunity waned, the underlying higher frequency of infection was revealed. A better understanding of the interaction between malaria exposure, immunity, and transmission risk will assist in identifying protective immune responses in P. falciparum infection.

Dataset Information

Early-life hepatitis e infection in pigs: the importance of maternally-derived antibodies.

Publications

Early-life hepatitis e infection in pigs: the importance of maternally-derived antibodies.

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