Genetic heterogeneity of betanodaviruses in juvenile production trials of Pacific bluefin tuna, Thunnus orientalis (Temminck & Schlegel).

Pacific bluefin tuna, Thunnus orientalis (Temminck & Schlegel), is one of the most important commercially exploited fish species in the world, and juvenile production techniques have been developed for its culture and stock enhancement in Japan. However, recent juvenile production has often failed because of the occurrence of viral nervous necrosis caused by betanodaviruses. In this study, we examined the genetic variability of betanodaviruses detected in the diseased juveniles to understand the transmission of the disease in a tuna hatchery. A total of 94 nucleotide sequences of betanodavirus (partial sequence of the coat protein gene, RNA2) were obtained from fish samples by reverse-transcriptase polymerase chain reaction amplification and 13 haplotypes were recognized among the sequences. The haplotype distributions in the viral populations from the diseased juveniles were related to the broodstocks from which the juveniles originated, suggesting that vertical transmission had occurred in the hatchery. The statistical parsimony network of viral haplotypes suggests that the nucleotide substitutions among the samples were accumulated in a recent population growth.

PCR-based detection of betanodaviruses from cultured and wild marine fish with no clinical signs.

Betanodaviruses are the causative agents of viral nervous necrosis (VNN) or viral encephalopathy and retinopathy (VER) in cultured marine fish. A total of 131 apparently healthy fish from 30 species were collected in two geographically remote aquaculture areas, Yashima Bay (Kagawa Prefecture) and Tamanoura Bay (Nagasaki Prefecture), in Japan. The brains of fish were examined by reverse transcriptase-polymerase chain reaction (RT-PCR) and nested PCR to detect the coat protein gene of betanodavirus. In Yashima Bay, two and 13 of 20 cultured fish were positive for nodavirus in RT-PCR and nested PCR, respectively, and four of five wild fish were positive only in nested PCR. In Tamanoura Bay, 28 and 99 of 106 wild fish were positive for the virus in RT-PCR and nested PCR, respectively. All the sequences of the nested PCR products (177 nt) from 27 fish species (10 cultured and 17 wild) were highly homologous to each other (99-100%) and were closely related to that of the known betanodavirus, redspotted grouper nervous necrosis virus (RGNNV). These results illustrate that large populations of cultured and wild marine fish in aquaculture areas are subclinically infected with genetically closely related betanodaviruses, suggesting an importance of such infected fish as a carrier or reservoir of betanodaviruses.

Mutations in SIP1, encoding Smad interacting protein-1, cause a form of Hirschsprung disease.

Hirschsprung disease (HSCR) is sometimes associated with a set of characteristics including mental retardation, microcephaly, and distinct facial features, but the gene mutated in this condition has not yet been identified. Here we report that mutations in SIP1, encoding Smad interacting protein-1, cause disease in a series of cases. SIP1 is located in the deleted segment at 2q22 from a patient with a de novo t(2;13)(q22;q22) translocation. SIP1 seems to have crucial roles in normal embryonic neural and neural crest development.

Quasi-immune response of Penaeus japonicus to penaeid rod-shaped DNA virus (PRDV).

A quasi-immune response was demonstrated in kuruma prawn Penaeus japonicus infected naturally or experimentally with PRDV (penaeid rod-shaped DNA virus, also called white spot syndrome virus or WSSV), the causative agent of PAV (penaeid acute viremia). In the first step of this study, natural survivors 4 mo after a PAV outbreak demonstrated 94 % relative percent survival (RPS) upon experimental PRDV challenge. Mortalities after challenge were confirmed by PRDV detection to be due to PAV using a PCR method. In the second step, experimental PAV survivors were produced by intramuscular (IM) injection of PRDV into naive shrimp subsequently reared collectively in a tank (A group) or individually in chamber units (B group). Survival was 41 and 90% in the A and B groups, respectively. A subsequent IM re-challenge of these PRDV survivor groups with PRDV made 32 d after the first challenge revealed a protective response with high RPS of 77 and 64%, respectively. These high survival rates suggested that PAV survivors (natural or experimental) were able to resist PRDV infection and that the resistance was not due to selection of naturally resistant shrimp during a PAV outbreak, but due to enhancement of an immune-like system (quasi-immune response) after exposure to PRDV. No PRDV neutralizing activity was revealed in the serum of the 4 mo natural survivors of the PRDV outbreak. However, it was found in their serum 17 d after they had been experimentally challenged with PRDV.

mu-Chain gene expression in common variable immunodeficiency.

Three patients with common variable immunodeficiency (CVID) were analyzed for translation from mu mRNA by the cell-free translation method and for expression of mu mRNA by northern blotting. In cases 1 and 2, the mu chain was not detected in the products by cell-free translation nor was mu mRNA detected by northern blotting. In case 3, mu mRNA was detected at a low level. This suggests that the disorders occur between rearrangement of the Ig genes and transcription of the C mu gene in cases 1 and 2, and that the functions of rearrangement and transcription are qualitatively preserved to a certain degree in case 3. Thus, the pathogeneses of CVID are variable and more research on regulatory mechanisms of B cell development is necessary to understand each case of CVID.

Long-term follow up of patients with common variable immunodeficiency treated with intravenous immunoglobulin: reevaluation of intravenous immunoglobulin replacement therapy. IVIG therapy in CVID.

Five patients with common variable immunodeficiency treated in our hospital between December 1979 and December 1990 were given six kinds of intravenous immunoglobulin preparations (pepsin treated, S-sulfonated, polyethylene glycol treated, pH4 treated, alkylated, and pH4.25 formulation preparation) for replacement therapy. Duration of the therapy ranged from 7.6 to 11 years. Incidences of fever and acute infections were variable among patients, but no significant differences were seen in the incidences among periods given each preparation. Three cases revealed abnormal pulmonary functions in tests. Adverse reactions were rarely seen in our study periods, and no severe reactions were observed. No significant differences were seen in incidences of adverse reactions. Postinfusion levels of serum complement slightly decreased from preinfusion levels. However, the decrease in complement was not related to any adverse reaction. No long-term complications such as transmission of hepatitis have been observed. Our data suggest that no obvious differences exist between the efficacy and safety of each IVIG preparation. Differences of efficacy of IVIG replacement therapy may be due to the variable pathophysiology of each patient.

Properties of a new virus belonging to nodaviridae found in larval striped jack (Pseudocaranx dentex) with nervous necrosis.

Spherical virus particles were purified from larval striped jack (Pseudocaranx dentex) with nervous necrosis. The virus consists of nonenveloped particles, about 25 nm in diameter, and contains two single-stranded, positive-sense RNA molecules with molecular weights of 1.01 x 10(6)Da (RNA 1) and 0.49 x 10(6)Da (RNA 2), respectively. The RNAs do not have poly(A) sequences at the 3' terminus. Virus structural proteins consist of two proteins with molecular weights of 42 and 40 kDa. When translated into cell-free extracts of rabbit reticulocytes, RNA 1 directed the synthesis of the 1a protein (100 kDa), whereas RNA 2 synthesized the 2a protein (42 kDa), which is probably the coat protein of the virus, and a polypeptide of 40 kDa which appears to be the processed form of the 42-kDa protein. Under electron microscopic observation, the virus particles were found in the tissues of the central nervous system of the affected larval striped jack. From morphological and biochemical properties of the virus, we identified this virus as a new member of the family of Nodaviridae and designated it striped jack nervous necrosis virus.

Suppression of immunoglobulin production of lymphocytes by intravenous immunoglobulin.

The proliferative responses and the immunoglobulin production of peripheral blood mononuclear cells to pokeweed mitogen were dose-dependently suppressed by sulfonated intravenous immunoglobulin (IVIG), polyethylene glycol-treated IVIG, pH 4-treated IVIG, or human gamma-globulin, but they were not or only slightly suppressed by human serum albumin or pepsin-treated IVIG. Moreover, the suppression of immunoglobulin production by sulfonated IVIG, polyethylene glycol-treated IVIG, or pH 4-treated IVIG was seen in the cases in which B cells preincubated with IVIGs were cocultured with T cells and monocytes preincubated with or without IVIGs and in the cases in which monocytes preincubated with IVIGs were cocultured with T cells and B cells preincubated with or without IVIGs. However, in the cases in which only T cells were preincubated with IVIGs, immunoglobulin production was not suppressed. The suppression of the monocyte function by IVIGs tended to be less than the suppression of the B-cell function by IVIGs. Moreover, the suppression by IVIGs was blocked by anti-human IgG Fc. Our results suggest that IVIGs suppress the immunoglobulin production of lymphocytes through suppression of the B-cell function and the antigen presenting-cell function by attachment of IVIGs to Fc receptors of B-cell membranes and antigen presenting-cell membranes.