Swine immunology in-depth: vaccines, immunity, and allergies

Oct 25, 2023

The Power of Maternal Vaccination: Shielding Piglets from PRRSV Threat

In swine farming, prioritizing piglets' health and well-being is paramount. Maternally-derived immunity (MDI) has long been hailed as a pivotal defense mechanism, shielding these young swine from dangerous pathogens. Today, we delve into the intriguing domain of porcine immunology to examine how maternal vaccination, with particular emphasis on autogenous inactivated vaccines (AIVs), can revolutionize the battle against Porcine Reproductive and Respiratory Syndrome Virus Type 2 (PRRSV-2).

Its genetic diversity and immune-suppressive properties have made PRRSV-2 a formidable adversary in the swine industry. Vaccines have offered a glimmer of hope, yet they face distinctive challenges, especially when safeguarding the swine population's most vulnerable members.

In this exposition, we explore the latest scientific discoveries that shed light on the potential of maternal vaccination to empower piglets against PRRSV-2 and introduce us to some remarkable and novel immune phenomena in the porcine world. Further insights can be gleaned by viewing Dr. Tobias Kaeser's participation in The Swine It Podcast and perusing his recent research.

Maternal-Derived Immunity: An Orchestrated Shield

Visualize an intricate orchestration of immunity, where mothers choreograph a harmonious ballet to protect their offspring. In the case of piglets, this orchestration involves the transmission of immunoglobulins, immune cells, and various immune-related molecules, all vital for the survival of the young swine. It resembles a symphonic masterpiece in which mothers equip their progeny for the challenges of the outside world. We encounter B cells and diverse T-cell subsets among the transferred immune cells, each playing a distinctive role in the defense. These T-cell subsets can be categorized based on their differentiation stage and homing pattern, offering us a glimpse into the fascinating diversity of piglet immunity.

The PRRSV Challenge

Now, let us turn our attention to the antagonist of our narrative: PRRSV. This notorious virus exists in two forms, PRRSV-1 and PRRSV-2, and has been a relentless adversary in the swine industry. PRRSV has inflicted substantial economic losses due to its high mutation rate and immune-suppressive capabilities. While vaccines are at our disposal, they confront their own set of challenges. On one front, we have modified live virus (MLV) vaccines, renowned for their immunogenicity but often less effective against prevailing PRRSV strains due to their protracted development process. Conversely, inactivated vaccines, particularly autogenous inactivated vaccines (AIVs), are tailored to target farm-specific strains. However, AIVs exhibit lower immunogenicity, rendering them susceptible, especially in the context of young piglets.

The Immune Arsenal: Maternal Vaccination

In response to these challenges, swine producers have turned to maternal vaccination to fortify piglet immunity. Research has unveiled that maternal vaccination with commercial MLV vaccines against PRRSV-1 can partially protect piglets against heterologous challenges. This approach triggers the production of specific immunoglobulins and interferon (IFN)-γ-secreting cells in the colostrum and milk of vaccinated sows.

A Promising Horizon: Combined Vaccination

Cognizant of the limitations inherent to individual MLV or AIV vaccines, the study examined in this discourse endeavors to ascertain the efficacy of maternal vaccination utilizing two distinct AIVs to augment the safeguarding provided by the industry-standard MLV vaccine. The research delves into the humoral and cell-mediated immune response in gilts and their piglets subjected to a PRRSV-2 challenge at a mere two weeks of age. The findings of this study illuminate that AIV boost vaccination could significantly enhance piglet protection against the PRRSV challenge.

Unveiling Immune Phenomena

This study not only provides encouraging outcomes but also reveals noteworthy immune mechanisms within piglets:

  1. CD8α-CCR7- CD4 T cells, functioning as formidable entities contributing to IFN-γ production in bronchoalveolar lavage (BAL), potentially representing CD4 TEMRA cells.
  2. IFN-γ-producing B cells, emerging as a pivotal force in the anti-PRRSV response, particularly within piglets. 

Conclusion: A Promising Path Forward

Overall, autogenous inactivated vaccines hold great promise for the battle against PRRSV. This strategy underscores the significance of transferring neutralizing antibodies to piglets, and it introduces us to two novel immune cell subsets in swine: the IFN-γ-producing CD21α+ B cells and the CD8α-CCR7- CD4 T cells. These discoveries broaden our comprehension of maternally derived immunity and proffer prospective solutions to confront one of the swine industry's most formidable adversaries. The future appears promising for the health and well-being of piglets.