Cells of the dendritic family display some unique properties that confer to them the capacity to sensitize naive T cells in vitro and in vivo. In the mouse, two subclasses of dendritic cells (DCs) have been described that differ by their CD8α expression and their localization in lymphoid organs. The physiologic function of both cell populations remains obscure. Studies conducted in vitro have suggested that CD8α⁺ DCs could play a role in the regulation of immune responses, whereas conventional CD8α⁻ DCs would be more stimulatory. We report here that both subclasses of DCs efficiently prime antigen-specific T cells in vivo, and direct the development of distinct T helper (Th) populations. Antigen-pulsed CD8α⁺ and CD8α⁻ DCs are separated after overnight culture in recombinant granulocyte/macrophage colony-stimulating factor and injected into the footpads of syngeneic mice. Administration of CD8α⁻ DCs induces a Th2-type response, whereas injection of CD8α⁺ DCs leads to Th1 differentiation. We further show that interleukin 12 plays a critical role in Th1 development by CD8α⁺ DCs. These findings suggest that the nature of the DC that presents the antigen to naive T cells may dictate the class selection of the adaptative immune response.

Brucellosis is not a sustainable disease in humans. The source of human infection always resides in domestic or wild animal reservoirs. The routes of infection are multiple: food-borne, occupational or recreational, linked to travel and even to bioterrorism. New Brucella strains or species may emerge and existing Brucella species adapt to changing social, cultural, travel and agricultural environment. Brucella melitensis is the most important zoonotic agent, followed by Brucella abortus and Brucella suis. This correlates with the fact that worldwide, the control of bovine brucellosis (due to B. abortus) has been achieved to a greater extent than the control of sheep and goat brucellosis (due to B. melitensis), these latter species being the most important domestic animals in many developing countries. The long duration and high cost of treatment of human brucellosis reduces the efficacy of the therapy. There is no human vaccine for brucellosis and the occurrence of brucellosis is directly linked to the status of animal brucellosis in a region. In this context, the Word Health Organization has defined the development of a human vaccine, besides the implementation of control and eradication programs in animals, as a high priority. The pathogenicity for humans of B. suis biovars 1, 3 and 4 is well established, whereas B. suis biovar 2 seems to be less pathogenic. Indeed, although hunters and pig farmers have repeatably experienced infectious contact with B. suis biovar 2 (found in wild boar and outdoor-rearing pigs in Europe), isolation of B. suis biovar 2 from human samples have only been seldom reported. Marine mammal brucellosis, due to two new proposed Brucella species i.e. B. cetaceae and B. pinnipediae, represents a new zoonotic threat but the pathogenicity for humans of the different Brucella species found in cetaceans and pinnipeds still has to be clearly established.

Small Gram-negative cocco-bacilli resembling Brucella strains have been reported from marine mammals since the mid-1990s. Their placement in the genus Brucella has been supported by the following characteristics: they are aerobic, non-motile and catalase-positive, do not produce acid from carbohydrates and have a DNA–DNA relatedness value of >77 % with the six established members of the genus. Twenty-eight European isolates of the genus Brucella from marine mammals were distinguished from the six recognized species by their pattern of utilization of eleven substrates in oxidative metabolism tests and phage lysis. The 28 strains could be further separated into two groups with cetaceans and seals as their respective preferred hosts on the basis of molecular methods and on differences in the metabolism of l-arabinose, d-galactose and d-xylose. The names Brucella ceti sp. nov. and Brucella pinnipedialis sp. nov. are proposed for the isolates from cetaceans and seals, respectively. The type strain of Brucella ceti sp. nov. is NCTC 12891^T (=BCCN 94-74^T) and the type strain of Brucella pinnipedialis sp. nov. is NCTC 12890^T (=BCCN 94-73^T).

To describe and discuss the merits of various direct and indirect methods applied in vitro (mainly on blood or milk) or in vivo (allergic test) for the diagnosis of brucellosis in animals. The recent literature on brucellosis diagnostic tests was reviewed. These diagnostic tests are applied with different goals, such as national screening, confirmatory diagnosis, certification, and international trade. The validation of such diagnostic tests is still an issue, particularly in wildlife. The choice of the testing strategy depends on the prevailing brucellosis epidemiological situation and the goal of testing. Measuring the kinetics of antibody production after Brucella spp. infection is essential for analyzing serological results correctly and may help to predict abortion. Indirect ELISAs help to discriminate 1) between false positive serological reactions and true brucellosis and 2) between vaccination and infection. Biotyping of Brucella spp. provides valuable epidemiological information that allows tracing an infection back to the sources in instances where several biotypes of a given Brucella species are circulating. Polymerase chain reaction and new molecular methods are likely to be used as routine typing and fingerprinting methods in the coming years. The diagnosis of brucellosis in livestock and wildlife is complex and serological results need to be carefully analyzed. The B. abortus S19 and B. melitensis Rev. 1 vaccines are the cornerstones of control programs in cattle and small ruminants, respectively. There is no vaccine available for pigs or for wildlife. In the absence of a human brucellosis vaccine, prevention of human brucellosis depends on the control of the disease in animals.