Publisher Summary Recent biological investigations of the African trypanosomes have been moving away from their previous preoccupation with the phenomenon of antigenic variation. The feeling has arisen that antigenic variation, as demonstrated by the Trypanozoon and Nannomonas subgenera of trypanosomes, is too extensive, the number of serodemes too large, and the coexistence of different species in many areas too complicated, to allow any immunoprophylaxis based on antibodies to variable antigens. However, in the case of T. vivax, more information is required concerning antigenic variation and coat structure in this organism before these avenues of investigation are discarded. The ways of improving the yield of mature metacyclic trypanosomes in vitro must be found, so that the contribution of metacyclic variable antigens to the induction of immunity in T. vivax infection can be elucidated. The number of bloodstream variable antigen types (VATs) must be determined, as there is evidence both for VAT exhaustion contributing to the self-cure of infected hosts and for a possible limit to the number of VATs that can be expressed in infections in Africa. It is probable that new DNA probes will have to be prepared to ensure the identification of all the members of this geographically dispersed species of protozoan parasite.

Recent Studies of the Biology of Trypanosoma vivax

African trypanosomes induce a generalized state of immunosuppression in their mammalian hosts. One characteristic of this is a suppression of lymphocyte responses to mitogen, which is mediated by suppressor macrophages. We investigated the involvement of nitric oxide in this phenomenon. Both peritoneal and splenic cell cultures from infected mice released nitrite and this was inhibitable by NG-monomethyl L-arginine (L-NMMA). The release of nitrite correlated with suppressed splenic T cell proliferative responses to concanavalin A. It was shown that adherent spleen cells from infected mice mediate suppression, which could be abrogated by L-NMMA. These results suggest that in T. brucei infection, the activation of macrophages to produce nitric oxide leads to impaired lymphocyte responses and immunosuppression.

Nitric-Oxide Mediates Suppression of T-Cell Responses in Murine Trypanosoma-Brucei Infection

Immune responses of cattle to African trypanosomes: protective or pathogenic?

Major modifications of immune system have been observed in African trypanosomiasis. These immune reactions do not lead to protection and are also involved in immunopathology disorders. The major surface component (variable surface glycoprotein,VSG) is associated with escape to immune reactions, cytokine network dysfunctions and autoantibody production. Most of our knowledge result from experimental trypanosomiasis. Innate resistance elements have been characterised. In infected mice, VSG preferentially stimulates a Th 1-cell subset. A response of gamma delta and CD8 T cells to trypanosome antigens was observed in trypanotolerant cattle. An increase in CD5 B cells, responsible for most serum IgM and production of autoantibodies has been noted in infected cattle. Macrophages play important roles in trypanosomiasis, in synergy with antibodies (phagocytosis) and by secreting various molecules (radicals, cytokines, prostaglandins,...). Trypanosomes are highly sensitive to TNF-alpha, reactive oxygen and nitrogen intermediates. TNF-alpha is also involved in cachexia. IFN-gamma acts as a parasite growth factor. These various elements contribute to immunosuppression. Trypanosomes have learnt to use immune mechanisms to its own profit. Recent data show the importance of alternative macrophage activation, including arginase induction. L-ornithine produced by host arginase is essential to parasite growth. All these data reflect the deep insight into the immune system realised by trypanosomes and might suggest interference therapeutic approaches.

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Immunology and immunopathology of African trypanosomiasis

Dermatophilus congolensis infection (dermatophilosis) is an acute, subacute or chronic skin disease affecting a wide range of species of animals and man. It is world widely distributed but more prevalent in the humid, tropics and subtropics. The disease is now being reviewed in detail. In the present review, the geographical distribution, history and nomenclature, animal hosts affected, aetiological agent and clinical signs of the disease are discussed extensively. Emphasis is also given on the predisposing factors such as rainfall, humidity, ectoparasites etc. under epizootiology. Pathogenesis, pathology, immunology treatment, control and prophylaxis are other areas well covered. The economic importance of the disease is also stressed and a new approach (biological approach) to treatment and control of the disease is being described in this review. It was concluded that in view of the importance of the disease for the increase of livestock and leather production in the tropical and subtropical region especially in Africa, an international centre for dermatophilosis research is highly needed.

Dermatophilus congolensis infection (dermatophilosis) in animals and man! An update

Groups of cattle infected singly with Trypanosoma vivax and T. congolense and, with a combination of T. vivax and T. congolense, were vaccinated against contagious bovine pleuropneumonia (CBPP) 6 weeks before or after infection. All animals were revaccinated 12 weeks after primary vaccination. The primary antibody responses in cattle vaccinated 6 weeks after infection with T. vivax and a combination of T. vivax plus T. congolense were slightly depressed in contrast to other groups which were similar in their response to the control group. Although secondary antibody responses developed in all infected groups, with a delay in those infected with T. congolense, they did not reach the levels of the controls. In spite of the slight depression in antibody responses, however, 50% of the vaccinated trypanosomal animals contracted CBPP on exposure to experimental infection while the vaccinated controls were immune. It is suggested that the protective immunity to CBPP engendered by vaccination is impaired during infection with African trypanosomes and that the level of antibody response to CBPP vaccination in trypanosomal animals does not reflect the degree of immunodepression. The importance of trypanosomiasis control in ensuring success of vaccination campaigns against CBPP is discussed.

Immunodepressive effects of trypanosomal infection in cattle immunized against contagious bovine pleuropneumonia.

Mycoplusma cupri (souche de Smith) et le virus de la peste des petits ruminants (PPR) ont été inoculés séparément ou simultanément à des chèvres adultes. Deux des quatre chèvres infectées par A4 cupri sont mortes d’une pneumonie généralisée 10 à 12 jours après inoculation. L’une des quatre chèvres inoculées avec le virus PPR est morte d’une gastroentérite grave 12 jours après inoculation de même que trois des quatre chèvres inoculées simultanément avec les deux germes sont mortes de pneumonie et de gastro-entérite, Des symptômes de pneumonie et de diarrhée sont apparus à des niveaux divers dans le groupe de chèvres témoin.

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Experimental infection of goats with Mycoplasma capri and "peste des petits ruminants" virus

R éponse immunitaire à la vaccination contre la péripneumonie contagieuse bovine sur des animaux atteints de dermatophiloses Cinq zébus atteints de dermatophilose et 5 zébus apparemment sains ont été vaccinés contre la péripneumonie contagieuse bovine (PCB). Les anticorps humoraux de la péripneumonie contagieuse bovine et à Dermatophilus congolensis ont été mesurés à l’aide du test d’hémaglutination passive. Pour les 3 animaux les plus infectés, la réponse immunitaire à la PCB s’est avérée très faible, comparée à celle des 2 animaux moyennement atteints et à celle des témoins. Les auteurs discutent brièvement de la signification de I’accroissement non ssécifiaue du niveau sériaue des anticorus à D. congolensis à la suite 2e la vacination Lnti-péripneumonique. Mots clés : Zébu Réponse immunitaire Périnneumonie contagieuse bovine Dermkophilose Vaccin Nigeria.

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Immune response to contagious bovine pleuropneumonia vaccine in dermatophilosis-infected animals.

Diverses colonies de Gap. meurent 24 heures apres avoir pris un repas de sang contenu dans un plateau recouvert avec une membrane de silicone. Une recherche sur la cause de la mort est entreprise. Une bacterie est isolee de la plupart des mouches. Il s'agit de Serratia marcescens. La signification de cet isolat en tant qu'entomopathogene est discutee

A bacterium pathogenic to tsetse fly (Glossina palpalis)

A lyophilised T1 vaccine was produced by direct lyophilisation of a 72-hour broth culture to which 10% sterile sucrose solution was added. Each vial contained 2 ml to make a total of 10 doses when reconstituted. Each ml of the product contained an average of 109 colony forming units of the organism. When injected at the tip of the tail or subcutaneously behind the shoulder of 2,000 zebu and 1,0000 Ndama cattle, no outward reactions were observed. 12 zebu cattle were vaccinated and challenged 6 months later by direct contact with artificially infected cattle for 4 months. All the animals were completely protected against the disease.

J. C. Chima

Papers

Immunodepressive effects of trypanosomal infection in cattle immunized against contagious bovine pleuropneumonia.

Experimental infection of goats with Mycoplasma capri and "peste des petits ruminants" virus

Immune response to contagious bovine pleuropneumonia vaccine in dermatophilosis-infected animals.

A bacterium pathogenic to tsetse fly (Glossina palpalis)

The T1 vaccine used in the control of contagious bovine pleuropneumonia in Nigeria.