The seasonal antibody response in juvenile summer flounder (Paralichthys dentatus) to the hemoflagellate Trypanoplasma bullocki

Interaction between endocrine and immune systems in fish

Diseases in fish are serious problems for the development of aquaculture. The outbreak of fish disease is largely dependent on environmental and endogenous factors resulting in opportunistic infection. Recent studies, particularly on stress response, have revealed that bidirectional communication between the endocrine and immune systems via hormones and cytokines exists at the level of teleost fish. Recently information on such messengers and receptors has accumulated in fish research particularly at the molecular level. Furthermore, it has become apparent in fish that cells of the immune system produce or express hormones and their receptors and vice versa to exchange information between the two systems. This review summarizes and updates the knowledge on endocrine-immune interactions in fish with special emphasis on the roles of such mediators or receptors for their interactions.

The lipopolysaccharide O side chain of Vibrio vulnificus serogroup E is a virulence determinant for eels

Vibrio vulnificus is a gram-negative bacterium capable of producing septicemic infections in eels and immunocompromised humans. Two biotypes are classically recognized, with the virulence for eels being specific to strains belonging to biotype 2, which constitutes a homogeneous lipopolysaccharide (LPS)-based O serogroup (which we have designated serogroup E). In the present study we demonstrated that the O side chain of this LPS determines the selective virulence of biotype 2 for eels: (i) biotype 1 strains (which do not belong to serogroup E) are destroyed by the bactericidal action of nonimmune eel serum (NIS) through activation of the alternative pathway of complement, (ii) biotype 2 strains (of serogroup E) are resistant to NIS, and (iii) rough mutants of biotype 2 lacking the O polysaccharide side chain are sensitive to NIS and avirulent for eels.

The effect of temperature and water quality on antibody response to Aeromonas salmonicida in sunshine bass (Morone chrysops x Morone saxatilis)

The kinetics of the antibody response to Aeromonas salmonicida were determined in sunshine bass (hybrid striped bass: female Morone chrysops X male Morone saxatilis) acclimated to 10, 18, 24, 29 degrees C, and to 0.15 mg 1(-1) un-ionized ammonia and 200 mg 1(-1) nitrate levels. Temperature and water quality factors affected the immune response of sunshine bass. Temperatures of 10 degrees C and 18 degrees C decreased the magnitude and delayed the time of the antibody response to A. salmonicida. The antibody response was not affected at 29 degrees C, which is above the optimal temperature for sunshine bass. Elevated un-ionized ammonia concentrations of 0.15 mg 1(-1) also did not affect the antibody response. Elevated nitrate levels of 200 mg 1(-1), however, decreased the antibody response to the same extent as 18 degrees C water.

Genetic variation in susceptibility to Trypanoplasma borreli infection in common carp (Cyprinus carpio L.)

Gynogenetic reproduction of homozygous females, or crossbreeding two homozygous animals, results in fish lines without genetic variation. Hybrid crosses are expected to express a more stable development than homozygous lines, the latter may have an important value for gaining insight into genetic components of host resistance to parasite infection. We examined the antibody response of carp (Cyprinus carpio L.) to infection with Trypanoplasma borreli. Outbred carp responded with a production of specific antibodies, but highly susceptible isogenic hybrid carp did not. This suggests an apparent relationship between susceptibility and the lack of specific antibody production. This relation was partially confirmed by the passive transfer of immunity with immune plasma. In addition, two isogenic homozygous carp lines were highly susceptible to the trypanoplasm (100% mortality), in contrast with outbred carp, the majority of which survived infection. None of the carp in either homozygous carp line produced an antibody response to parasite-unrelated antigen (DNP-KLH). This suggests that the low antibody response was not entirely due to a poor state of health, but that these carp have a genetically predetermined low antibody response.

Effects of inoculum route and dose on the immune response of common carp, Cyprinus carpio to the blood parasite, Trypanoplasma borreli

Carp were inoculated intramuscularly (im) or intraperitoneally (ip) with different doses of live Trypanoplasma borreli. Prepatent period was shortened by using the im route and by increasing the dose. Haematocrit was reduced following im inoculation with 9.5 x 10(5) parasites. Most fish recovered between 8 and 13 weeks post-inoculation (wpi). Neither parasitaemia nor anaemia was detected in any recovered fish following homologous challenge. An enzyme-linked immunosorbent assay was developed to quantitate antibody response elicited by the parasite. Antibody levels rose rapidly during the first 4 wpi. The response elicited by increased dose was significantly higher only at 4 wpi. Route of exposure did not affect antibody response. Peak responses coincided with decline and eventual absence of parasitaemia.

Effect of size and temperature on the quantity of immunoglobulin in channel catfish, Ictalurus punctatus

Concentrations of serum immunoglobulin (Ig) were determined for 30 channel catfish from pond water at 10 degrees C. These values were compared to measurements of 15 channel catfish from pond water at 30 degrees C. Channel catfish from 10 degrees C pond water had no significant (P greater than 0.05) different Ig concentrations (mean, 398 mg/dl) than catfish from 30 degrees C pond water (mean, 367 mg/dl). Serum Ig concentrations appear not to be different in cold (10 degrees C) vs warm (30 degrees C) pond water for 37.5-45 cm catfish. Channel catfish, 7.5-15 cm (n = 24) had significantly (P less than 0.05) lower Ig levels (mean, 104 mg/dl) than catfish either 7.5-25.5 cm (n = 57, mean, 232 mg/dl) or 37.5-45 cm (n = 45, mean, 388 mg/dl). Also, catfish 17.5-25.5 cm had a significantly (P less than 0.05) less Ig than catfish 37.5-45 cm. The concentrations of serum Ig increase with size (P = 0.0001) of catfish. The mean Ig concentration for 7.5-45 cm catfish (n = 126) was 263 mg/dl. The Ig concentration range was 44 to 650 mg/dl of serum.

Immune response of fish to parasitic protozoa

Epizootic outbreaks of fish diseases are increasingly common as a result of intensive aquaculture, fish farming and sea ranching. Very few drugs are available for treatment or prophylaxis against fish diseases, and development of such compounds is inhibited by different national regulations governing the use of chemicals in fish for human or animal consumption. Alternative approaches are urgently needed. But although the taxonomy and biology of fish parasites have been extensively studied, relatively little is known about protective immunity in fish and the effects of parasites on the piscine immune system. In this article, Patrick Woo discusses the immune responses of fish to parasitic protozoa, showing that vaccination is a viable control strategy, and stressing the need for a coordinated global research programme on fish diseases.