Transfer of maternal immunity using a polyvalent vaccine and offspring protection in Nile tilapia, Oreochromis niloticus

Background: Vaccination is an effective and alternative means of disease prevention, however, it cannot be conducted on the offspring of fish. For this process to take place, the transfer of maternal immunity must be implemented. This study aims to determine the effectiveness of transferring immunity from the broodstock to the offspring using a polyvalent vaccine against Aeromonas hydrophila, Streptococcus agalactiae, and Pseudomonas fluorescens in Nile tilapia, Oreochromis niloticus. Methods: Nile tilapia broodstock, with an average weight of 203g (±SD 23 g) was injected with a vaccine used as a treatment. Example include A. hydrophila monovalent (MA), S. agalactiae monovalent (MS), P. fluorescens monovalent (MP), A. hydrophila and S. agalactiae bivalent (BAS), A. hydrophila and P. fluorescens bivalent (BAP), P. fluorescens and S. agalactiae bivalent (BPS), and A. hydrophila, S. agalactiae, and P. fluorescens polyvalent vaccines (PAPS). While the control was fish that were injected with a PBS solution. The broodstock’s immune response was observed on the 7th, 14th, 21st, and 28th day, while the immune response and challenge test on the offspring was conducted on the 10th, 20th, 30th, and 40th day during the post-hatching period. Result: The application of PAPS in broodstock could significantly induce the best immune response and immunity to multiple diseases compared to other treatments. The RPS of the PAPS was also higher than the other types of vaccines. This showed that the transfer of immunity from the broodstock to the Nile tilapia offspring could protect it against bacterial diseases such as A. hydrophila, S. agalactiae, and P. fluorescens. Conclusion: The application of PAPS A. hydrophila, S. agalactiae, P. fluorescens vaccines increased the broodstock’s immune response and it was transferred to their offsprings. They were able to produce tilapia seeds that are immune to diseases caused by A. hydrophila, S. agalactiae, and P. fluorescens.

Transfer of maternal immunity project

This preprint is a part of the article "Transfer of maternal immunity using a polyvalent vaccine and offspring protection in Nile tilapia, Oreochromis niloticus"

Paternal Behavior from a Neuroendocrine Perspective

How hormones and neuromodulators initiate and maintain paternal care is important for understanding the evolution of paternal care and the plasticity of the social brain. The focus here is on mammalian paternal behavior in rodents, non-human primates and humans. Only 5% of mammalian species express paternal care, and many of those species likely evolved the behavior convergently. This means that there is a high degree of variability in how hormones and neuromodulators shape paternal care across species. Important factors to consider include social experience (alloparental care, mating, pair bonding, raising a previous litter), types of care expressed (offspring protection, providing and sharing food, socio-cognitive development), and timing of hormonal changes (after mating, during gestation, after contact with offspring). The presence or absence of infanticide towards offspring prior to mating may also be a contributor, especially in rodents. Taking these important factors into account, we have found some general trends across species. (1) Testosterone and progesterone tend to be negatively correlated with paternal care but promote offspring defense in some species. The most evidence for a positive association between paternal care and testosterone have appeared in rodents. (2) Prolactin, oxytocin, corticosterone, and cortisol tend to be positively correlated. (3) Estradiol and vasopressin are likely nuclei specific—with some areas having a positive correlation with paternal care and others having a negative association. Some mechanisms appear to be coopted from females and others appear to have evolved independently. Overall, the neuroendocrine system seems especially important for mediating environmental influences on paternal behavior.

Oral immunization with a probiotic cholera vaccine induces broad protective immunity againstVibrio choleraecolonization and disease in mice

Oral cholera vaccines (OCVs) are being increasingly employed, but current killed formulations generally require multiple doses and lack efficacy in young children. We recently developed a new live-attenuated OCV candidate (HaitiV) derived from aVibrio choleraestrain isolated during the 2010 Haiti cholera epidemic. HaitiV exhibited an unexpected probiotic-like activity in infant rabbits, preventing intestinal colonization and disease by wild-typeV. choleraebefore the onset of adaptive immunity. However, it remained unknown whether HaitiV would behave similarly to other OCVs to stimulate adaptive immunity againstV. cholerae.Here, we orally immunized adult germ-free female mice to test HaitiV’s immunogenicity. HaitiV safely and stably colonized vaccinated mice and induced known adaptive immune correlates of cholera protection within 14 days of administration. Pups born to immunized mice were protected against lethal challenges of both homologous and heterologousV. choleraestrains. Cross-fostering experiments revealed that protection was not dependent on vaccine colonization in or transmission to the pups. These findings demonstrate the protective immunogenicity of HaitiV and support its development as a new tool for limiting cholera.Author summaryVaccines for cholera are gaining acceptance as public health tools for prevention of cholera and curtailing the spread of outbreaks. However, current killed vaccines provide minimal protection in young children, who are especially susceptible to this diarrheal disease, and do not stimulate immunity against antigens that may only be expressed by live bacteria during infection. We recently developed HaitiV, an extensively engineered live-attenuated oral cholera vaccine candidate, derived from a clinical isolate from the Haiti cholera outbreak. Here, we found that the HaitiV induces immunological correlates of protection against cholera in germ free mice and leads to protection against disease in their offspring. Protection in this model was dependent on passively acquired factors in the milk of immunized dams and not transmission or colonization of HaitiV. Coupling the immunogenicity data presented here with our previous observation that HaitiV can protect from cholera prior to the induction of adaptive immunity, suggests that HaitiV may provide both rapid-onset short-term protection from disease while eliciting stable and long-lasting immunity against cholera.

Macroecology of parental care in arthropods: higher mortality risk leads to higher benefits of offspring protection in tropical climates

The intensity of biotic interactions varies around the world, in such a way that mortality risk imposed by natural enemies is usually higher in the tropics. A major role of offspring attendance is protection against natural enemies, so the benefits of this behaviour should be higher in tropical regions. We tested this macroecological prediction with a meta‐regression of field experiments in which the mortality of guarded and unguarded broods was compared in arthropods. Mortality of unguarded broods was higher, and parental care was more beneficial, in warmer, less seasonal environments. Moreover, in these same environments, additional lines of defence further reduced offspring mortality, implying that offspring attendance alone is not enough to deter natural enemies in tropical regions. These results help to explain the high frequency of parental care among tropical species and how biotic interactions influence the occurrence of parental care over large geographic scales. Finally, our findings reveal that additional lines of defences – an oftentimes neglected component of parental care – have an important effect on the covariation between the benefits of parental care and the climate‐mediated mortality risk imposed by natural enemies.

Freezing suppression by oxytocin in central amygdala allows alternate defensive behaviours and mother-pup interactions

When animals and their offspring are threatened, parents switch from self-defense to offspring protection. How self-defense is suppressed remains elusive. We postulated that suppression of the self-defense response, freezing, is gated via oxytocin acting in the centro-lateral amygdala (CeL). We found that rat dams conditioned to fear an odor, froze when tested alone, whereas if pups were present, they remained in close contact with them or targeted the threat. Furthermore, blocking oxytocin signaling in the CeL prevented the suppression of maternal freezing. Finally, pups exposed to the odor in the presence of the conditioned dam later froze when re-exposed alone. However, if oxytocin signaling in the dam had been blocked, pups failed to learn. This study provides a functional role for the well-described action of oxytocin in the central amygdala, and demonstrates that self-defense suppression allows for active pup protection and mother-pup interactions crucial for pup threat learning.