The specific humoral immune response of sea bream, Sparus aurata (L.), against Vibrio anguillarum O1 and Photobacterium damselae subsp. piscicida (Phdp) after immunization with commercial and experimental bacterins was analysed quantitatively and qualitatively. Specific anti-V. anguillarum O1 and anti-Phdp levels provoked by the adjuvanted commercial vaccine reached higher levels in comparison to the aqueous commercial and experimental bacterins. Infection of vaccinated fish with V. anguillarum O1 bacterial cells acted as a boost of the humoral immune response, except for the sera of the group vaccinated with the adjuvanted vaccine. Infection with Phdp acted as a boost of the humoral immune response mainly for the group vaccinated with a monovalent Phdp bacterin and to a lesser degree for the group vaccinated with the aqueous commercial vaccine. Western blot analysis of the sera against V. anguillarum O1 whole cell antigens revealed strong reactions to only a few antigens below 54 kD and above 15 kD and weak reactions to other antigens. Similar reactions were observed from the sera isolated from the controls. Western blot analysis of the sera against Phdp whole cell antigens revealed strong reactions to only a handful of antigens below 20.7 and below 6.4 kD. Sera from the control group, as in the case of V. anguillarum O1, reacted with Phdp whole cell antigens. No differences regarding antigen reactions between monovalent and bivalent formulations were noted, in contrast to the adjuvanted and aqueous bacterins.

In South America, visceral leishmaniasis is frequently caused by Leishmania infantum and, at an unknown frequency, by Leishmania amazonensis. Therefore, mixed infections with these organisms are possible. Mixed infections might affect the clinical course, immune response, diagnosis, treatment and epidemiology of the disease. Here we describe the clinical course of mixed infections with L. amazonensis and L. infantum in a hamster model. We show that mixed infections are associated with more severe clinical disease than infection with L. amazonensis or L. infantum alone. In spleens with mixed infections, L. infantum outcompeted L. amazonensis in the tissue, but not in culture from tissue. We found increased levels of IgG in animals infected with L. infantum. Although more than 30 bands were revealed in a Western blot, the highest immunogenicity was observed with proteins having molecular masses of 95 and 90 kDa, whereas proteins with molecular masses of lower than 50 kDa were reactive frequently with serum from hamsters infected with L. amazonensis, and proteins with molecular masses of 80 and 70 kDa were reactive only with serum from hamsters infected with L. infantum. This finding has important implications regarding the biology of Leishmania and humoral immune responses to infections with these organisms.

The neonatal period is often polarised to T helper (Th2) response at the time of birth, predisposing offspring to allergic disorders. Passive immunity through the mother’s milk is critical for immune system development of newborns. Probiotics have been proposed to harmonise Th1/Th2 imbalance in allergic conditions in adults. In the present study, the anti-allergic effects of feeding probiotic Lactobacillus rhamnosus-fermented milk (PFM) either to dams during the suckling period or to their offspring after weaning individually or else in successive periods against ovalbumin (OVA)-induced allergy in newborns was analysed. After allergen sensitisation, physical symptoms of allergy, gut immune response, humoral immune response and cell-mediated response through interleukins were detected. Consumption of PFM by mothers and offspring showed a reduction (P<0·01) in physical allergic symptoms in newborns with an increase (P<0·01) in the numbers of goblet and IgA+ cells in the small intestine. Similarly, considerable (P<0·001) decreases in OVA-specific antibodies (IgE, IgG, IgG1) and ratios of IgE/IgG2a and IgG1/IgG2a in the sera of newborn mice were recorded. A decrease in IL-4 and an increase in interferon-γ levels further confirmed the shift from Th2 to Th1 pathway in PFM-fed mice. It is logical to conclude that the timing of PFM intervention in alleviating allergic symptoms is critical, which was found to be most effective when mothers were fed during the suckling period.

Mongolian jirds, Meriones unguiculatus, are susceptible to infection with Trypanosoma grosi, which naturally parasitizes Apodemus spp. The present study investigated T cell dependence of elimination of T. grosi from the bloodstream of jirds by in vivo T cell depletion using a monoclonal antibody (HUSM-M.g.15). In T cell-depleted jirds, elimination of T. grosi, particularly the dividing forms, from the bloodstream was significantly delayed, occurring at around week 3 p.i. The kinetics of serum levels of IgM and IgG specific to trypanosomes in T cell-depleted and control immunocompetent jirds were different; peak levels of IgM were noted on days 6–8 p.i. around the time of peak parasitaemia (day 6 p.i.) in immunocompetent jirds, whereas the serum levels began to increase abruptly after day 10 p.i., peaking at around day 18 p.i. in T cell-depleted jirds. Similarly, serum IgG increased after day 6 p.i. in immunocompetent jirds, in contrast to after day 12 p.i. in T cell-depleted jirds, and the level increased steadily even after disappearance of parasitaemia. Our findings indicate that T cells play a major role at least in the ‘first crisis’ during elimination of dividing T. grosi from the bloodstream.

It has been suggested that decreased immune responsiveness in the elderly may be counteracted by the antioxidant vitamin E. In a 3-month double-blind placebo-controlled intervention trial among elderly subjects aged 65 years and over we studied the effects of a daily dose of 100 mg dl-α-tocopheryl acetate on the cellular immune responsiveness (n 52) measured by the in vitro response of peripheral blood mononuclear cells (PBMC) to the mitogens concanavalin A (ConA) and phytohaemagglutinin (PHA). Also effects on the humoral immune responsiveness (n 74) were investigated by measuring immunoglobulin (Ig)G, IgG4 and IgA antibody concentrations against various common antigens. In the vitamin E group plasma α-tocopherol increased by 51 % (P = 0.0001) during intervention whereas no significant changes were observed in the control group. Initial proliferative PBMC responses differed between the vitamin E group and the control group whereas all other baseline characteristics were comparable. No significant changes were observed in cellular immune responsiveness when adjusted for initial values in either the control group or the vitamin E group and, after the trial period, responses in the two groups were not significantly different. Similarly, in the vitamin E group no significant changes were found in levels of IgG and IgA raised against Penicillium or IgG4 raised against egg, milk, or wheat proteins. In the control group small but significant increases in IgG anti-Penicillium (P <0.05) and decreases in IgG4 against milk proteins (P < 0.05) were observed. Thus, the results of this study performed with the relatively low dose of 100 mg dl-α-tocopheryl acetate do not support the claims of a beneficial effect of vitamin E intake on the overall immune responsiveness of elderly subjects.