Immune responsiveness to phytohemagglutinin displays species but not sex differences in three anuran species

Phytohemagglutinin (PHA)-induced skin swelling response is widely used as a rough surrogate of integrative cell-mediated and innate immunity across multiple vertebrate taxa due to its simplification and feasibility. However, little is known whether there are sex and interspecific differences of immune responsiveness to PHA in ectotherms, especially for anurans. Therefore, we studied sex and species differences of PHA response in three anurans, Asiatic toads (Bufo gargarizans), Dark-spotted frogs (Pelophylax nigromaculatus) and Mongolian toads (Pseudepidalea raddei), captured in northern regions of Anhui Province (China). Footpad thickness was measured prior to (0 h) and after (6, 12, 24, 48 and 72 h) a PHA injection and normalized against saline injection in the opposite footpad. Body mass was recorded at the beginning (0 h) and end of each assay (72 h). Results showed effects of PHA assay, sex and taxa on body mass. Relative maximum swelling response (PHAmax) ranged from 18.58–29.75%, 9.77 to 20.56% and 21.97 to 31.78% and its occurrence over time was apparent 10.6–19.72 h , 7.74–14.01 h and 17.39–23.94 h postinjection for Asiatic toads, Dark-spotted frogs and Mongolian toads, respectively. Finally, the magnitude or timing of PHAmax in Dark-spotted frogs was significantly thinner and faster than in Mongolian toads, and Asiatic toads had an in-between value, not different from the other two species. The magnitude of PHAmax was significantly positively correlated with the timing of PHAmax considering individuals altogether, but not when analyzed within species. Our results indicate that male and female anuran species respond similarly to PHA antigen stimulation, but the magnitude and timing of PHAmax is species-specific. Briefly, we provide new evidence for the suitability of PHA assay in non-model anuran species with different body sizes, and exhort the need to further investigate the nature of PHA assay at the hematological and histological levels in order to extend its application in ecoimmunological studies of amphibians.

Transgenerational effects enhance specific immune response in a wild passerine

Vertebrate mothers transfer diverse compounds to developing embryos that can affect their development and final phenotype (i.e. maternal effects). However, the way such effects modulate offspring phenotype, in particular their immunity remains unclear. To test the impact of maternal effects on offspring development we treated with Newcastle disease virus (NDV) vaccine wild breeding house sparrow (Passer domesticus) females in Sevilla, SE Spain. Female parents were vaccinated when caring first broods, and their offspring from their following brood were evaluated for their immune response to the same vaccine and to the PHA inflammatory test. Vaccinated chicks from vaccinated mothers developed a stronger specific response that was related to maternal NDV antibody concentration. Chick’s carotenoid concentration and total antioxidant capacity in blood were negatively related to NDV antibody concentration, whereas no relation with PHA response was found. Specific NDV antibodies could not be detected on 10 day old control chicks from vaccinated mothers, implying that maternally transmitted antibodies promote offspring specific immunity through a priming effect, while other immunity components remain unaffected. Maternally transmitted antibodies are short-lived, depend on maternal circulation levels and may be adaptive when chicks are frequently exposed to the same pathogens as their mothers.

Transgenerational effects enhance specific immune response in a wild passerine

Vertebrate mothers transfer diverse compounds to developing embryos that can affect their development and final phenotype (i.e. maternal effects). However, the way such effects modulate offspring phenotype, in particular their immunity remains unclear. To test the impact of maternal effects on offspring development we treated with Newcastle disease virus (NDV) vaccine wild breeding house sparrow (Passer domesticus) females in Sevilla, SE Spain. Female parents were vaccinated when caring first broods, and their offspring from their following brood were evaluated for their immune response to the same vaccine and to the PHA inflammatory test. Vaccinated chicks from vaccinated mothers developed a stronger specific response that was related to maternal NDV antibody concentration. Chick’s carotenoid concentration and total antioxidant capacity in blood were negatively related to NDV antibody concentration, whereas no relation with PHA response was found. Specific NDV antibodies could not be detected on 10 day old control chicks from vaccinated mothers, implying that maternally transmitted antibodies promote offspring specific immunity through a priming effect, while other immunity components remain unaffected. Maternally transmitted antibodies are short-lived, depend on maternal circulation levels and may be adaptive when chicks are frequently exposed to the same pathogens as their mothers.

Vector abundance determines Trypanosoma prevalence in nestling blue tits

SUMMARYThe effect of insect vectors on avian exposure to infection by pathogens remains poorly studied. Here, we used an insect repellent treatment to reduce the number of blood-sucking flying insects in blue tit Cyanistes caeruleus nests and examined its effect on nestling health status measured as body mass, nestling phytohaemagglutinin (PHA) response and blood parasite prevalence. We found that (i) the insect repellent treatment significantly reduced the number of blood-sucking flying insects in nests and (ii) the number of blood-sucking flying insects had a significant effect on the prevalence of the blood parasite Trypanosoma independently of the treatment. In addition, we found support for an adverse effect of parasite infections on nestling PHA response. Nestlings infected by Trypanosoma mounted a weaker response against PHA than non-parasitized ones. In addition, the number of blowflies in the nest was negatively associated with nestling PHA response. Overall, we found support for the hypothesis that blood-sucking flying insects attacking nestlings increase their exposure to parasite infections. Our results further substantiate the adverse effect of parasites on nestling condition.

Nestling immune response to phytohaemagglutinin is not heritable in collared flycatchers

The response to intradermally injected phytohaemagglutinin (PHA-response) is a commonly used quantification of avian immunocompetence (the ability to resist pathogens). Parasite-mediated sexual selection requires heritable immunocompetence, but evidence for heritability of PHA-response in birds largely stems from full-sib comparisons. Using an animal model approach, we quantified the narrow-sense heritability of PHA-response in 1626 collared flycatcher ( Ficedula albicollis ) nestlings from 332 families, most of which were cross-fostered. Nestling PHA-response was not significantly heritable ( h 2 =0.06±0.10), but was subject to non-heritable nest-of-origin effects (10% of variation). Our findings illustrate that full-sib comparisons of immunological measures may lead to an inflated estimate of heritability and also reveal a limited role of nestling PHA-response for sexual selection in this population.