Infection of Newborn Piglets with Bordetella pertussis : a New Model for Pertussis

Abstract

Bordetella pertussis is the causative agent of pertussis or whooping cough. This bacterium is a human pathogen that under experimental conditions also infects selected rodents and primates. Here, we show for the first time that newborn piglets can be infected with B. pertussis when it is delivered intrapulmonarily. Infected piglets displayed fever and respiratory symptoms, such as nasal discharge, nonparoxysmal coughing, and breathing difficulties. Eventually, all infected animals developed severe bronchopneumonia, which in some cases was combined with a fibrinous pleuritits. Immunohistochemical staining revealed the presence of large numbers of B. pertussis cells within airways, adhering to the epithelial lining or phagocytosed by macrophages and neutrophils. Viable bacteria were reisolated from bronchoalveolar lavages and lung lesions for more than 10 days postinfection. The systemic presence of pertussis toxin was shown by hypoglycemia, lymphocytosis, and induction of a clustered pattern of CHO cells by serum and bronchoalveolar lavage samples. Thus, a largeanimal model for pertussis was developed, which should complement existing rodent models for identifying the immune responses relevant to the design of new vaccines. In particular, this model should help researchers analyze the roles of both maternal and mucosal immunity in disease protection against pertussis and should ultimately assist in the design of new vaccines for early life protection.

Protective Role of Passively Transferred Maternal Cytokines against Bordetella pertussis Infection in Newborn Piglets

“…Newborn piglets born to either vaccinated or control sows were challenged with 5 ϫ 10 9 CFU of live bacteria at 3 to 5 days of age. All of the piglets born to nonvaccinated control sows displayed severe clinical symptoms and pathological alterations similar to findings of our previously published studies (44,46). In contrast, piglets born to vaccinated sows showed no or significantly milder fever and respiratory symptoms (44).…”

“…(iii) Active immunization does not provide protection against infection with B. pertussis in newborn piglets. Piglets of both vaccinated and control groups were challenged with 2 ϫ 10 10 to 5 ϫ 10 10 CFU of live bacteria at 24 to 26 days of age as we described elsewhere (46)(47)(48). Piglets from either control or vaccinated groups displayed clinical symptoms, including mild fever, nasal discharge, nonparoxysmal cough, and breathing difficulties, as we previously showed (46,48).…”

“…Piglets were anesthetized with isoflurane and intubated using a laryngoscope and an endotracheal tube, and bacteria (5 ϫ 10 9 CFU) were delivered through the tube at a level of 1.5 ml/lung craniodorsal to the bronchial bifurcation, as we have previously described elsewhere (44,46,47).…”

“…Bacterial suspensions of strain Tohama I were stored at Ϫ80°C in Casamino Acids plus 10% glycerol. Organisms were initially grown on the surface of Bordet-Gengou (BG; Becton, Dickinson and Company) agar containing 15% (vol/vol) defibrinated sheep blood and 40 g/ml of cephalexin (Sigma-Aldrich) at 37°C for 72 h. After incubation, heavy inocula of bacteria were transferred to Stainer-Scholte (SS) medium and grown aerobically at 37°C overnight as liquid cultures, as we described elsewhere (46).…”

Resurgence of pertussis calls for re-evaluation of pertussis animal models

“…Also, all experimental animal species will have lifespan restrictions when testing durability of protection. Moreover, no model, not even the human, has disclosed a defined correlate or surrogate of protection for pertussis (Table 1) [12,18,22,[96][97][98][99][100][101][102][103][104][105][106][107][108][109][110][111][112][113].…”