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Amphibian populations suffer massive mortalities from infection with frog virus 3 FV3, genus Ranavirus, family Iridoviridae, a pathogen also involved in mortalities of fish and reptiles. Experimental oral infection with FV3 in captive-raised adult wood frogs, Rana sylvatica Lithobates sylvaticus, was performed as the first step in establishing a native North American animal model of ranaviral disease to study pathogenesis and host response. Oral dosing was successful LD50 was 10(2.93 2.423.44) p.f.u. for frogs averaging 35mm in length. Onset of clinical signs occurred 614days post-infection p.i. median 11 days p.i. and time to death was 1014 days p.i. median 12 days p.i.. Each tenfold increase in virus dose increased the odds of dying by 23-fold and accelerated onset of clinical signs and death by approximately 15. Ranavirus DNA was demonstrated in skin and liver of all frogs that died or were euthanized because of severe clinical signs. Shedding of virus occurred in faeces 710 days p.i. 34.5days before death and skin sheds 10 days p.i. 01.5days before death of some frogs dead from infection. Most common lesions were dermal erosion and haemorrhages haematopoietic necrosis in bone marrow, kidney, spleen and liver and necrosis in renal glomeruli, tongue, gastrointestinal tract and urinary bladder mucosa. Presence of ranavirus in lesions was confirmed by immunohistochemistry. Intracytoplasmic inclusion bodies probably viral were present in the bone marrow and the epithelia of the oral cavity, gastrointestinal tract, renal tubules and urinary bladder. Our work describes a ranaviruswood frog model and provides estimates that can be incorporated into ranavirus disease ecology models., (© 2015 The Authors.)

We investigated the presence of the measles virus genome in order to identify asymptomatic infections in the adult population. Bone-marrow aspirates were obtained from 179 patients, 20-96 years of age, for the diagnosis of malignant diseases (29 with malignant lymphoma, 28 with acute leukaemia, 21 with myelodysplastic syndrome, five with multiple myeloma and 96 with other diseases). The measles virus genome was detected in 17 (9.5%) of 179 individuals by RT-PCR and 28 (15.6%) through hybridization. The genomes detected in bone marrow were all in the same cluster, D5, the strain circulating during the study period, and no evidence of persistent infection was obtained. We conclude that asymptomatic infections of measles virus are common in adults and the presence of the measles virus genome would not be related to the pathogenesis of illness.

An emerging amount of data indicates a correlation between gender-related factors and regulation of virus infection and supports what is known in clinical circles, that these topics are of great importance in many infectious diseases. In the present study we found that young adult NMRI male mice are more susceptible to infection by a variant of Friend murine leukaemia virus, FIS-2, than are female mice. We observed that the level of virus in serum, bone marrow and spleen was initially higher in male mice. Male mice were also more susceptible to FIS-2-induced immunosuppression. These results indicate a more efficient virus replication and dissemination in male mice. Studies with recombinant viruses between FIS-2 and the prototype Friend murine leukaemia virus revealed that FIS-2 LTR is one major factor contributing to the observed gender differences. A possible sex hormone influence on FIS-2 transcription due to the presence of a glucocorticoid response element in FIS-2 LTR is discussed.

The antibody response to the envelope proteins of hepatitis C virus (HCV) may play an important role in controlling the infection. To allow molecular analyses of protective antibodies, we isolated human monoclonal antibodies to the E2 envelope glycoprotein of HCV from a combinatorial Fab library established from bone marrow of a chronically HCV-infected patient. Anti-E2 reactive clones were selected using recombinant E2 protein. The bone marrow donor carried HCV genotype 2b, and E2 used for selection was of genotype 1a. The antibody clones were expressed as Fab fragments in E. coli, and as Fab fragments and IgG1 in CHO cells. Seven different antibody clones were characterized, and shown to have high affinity for E2, genotype 1a. Three clones also had high affinity for E2 of genotype 1b. They all bind to conformation-dependent epitopes. Five clones compete for the same or overlapping binding sites, while two bind to one or two other epitopes of E2. Four clones corresponding to the different epitopes were tested as purified IgG1 for blocking the CD81-E2 interaction in vitro; all four were positive at 0.3-0.5 microg/ml. Thus, the present results suggest the existence of at least two conserved epitopes in E2 that mediate inhibition of the E2-CD81 interaction, of which one appeared immunodominant in this donor.

Jembrana disease virus (JDV) is a lentivirus that causes an acute, severe disease syndrome in infected Bali cattle in Indonesia. An in situ hybridization technique was developed that detected JDV genomic RNA in formalin-fixed paraffin-embedded tissue sections, using a digoxigenin-labelled riboprobe. Large numbers of JDV-infected cells were demonstrated in many tissue sections from experimentally infected animals early in the disease course, which was consistent with the extremely high circulating viraemia previously reported to occur during the febrile phase. The number of infected cells was consistently highest in sections of spleen, followed by many other tissues including lymph nodes, lungs, bone marrow, liver and kidney. Infected cells were also identified in the general circulation and within unusual intravascular lesions in lung sections. The relatively high level of infection found in bone marrow suggested that its involvement may be important in the disease pathogenesis, as it is with other lentiviruses.

We analysed the production of transforming growth factor beta (TGF-beta) during a cytomegalovirus (CMV) infection in a rat model system. Splenocytes from immunocompetent rats infected with rat CMV (RCMV) released increased amounts of TGF-beta1. TGF-beta production was also evident in RCMV-infected radiation-immunosuppressed rats; their sera inhibited the interleukin 2-induced proliferation of T cells, which could be restored by anti-TGF-beta antibodies. In addition, TGF-beta production could be visualized immunohistologically in the lungs, spleen, liver and bone marrow of radiation-immunosuppressed infected rats. The virus directly induced this cytokine since TGF-beta was produced upon RCMV infection in vitro. The induction of TGF-beta production may contribute to immunosuppression during CMV infection.

To elucidate in vivo cell tropism and infection kinetics of an immunodeficiency-inducing isolate of feline leukaemia virus (FeLV-FAIDS), we quantified the two major genotypes comprising FeLV-FAIDS [the replication-competent common form (clone 61E) and the replication-defective variant (clone 61C)] in lymphocyte and leukocyte populations from infected cats. Micromagnetic separation of cell subsets, virus genome-specific PCR and flow cytometry were used to demonstrate the following sequence of events in infected animals: (i) very early replication of both 61E and 61C in CD4 T cells (provirus burden 0.2 to 1 copy/cell at 2-4 weeks post-infection); (ii) lower magnitude replication of both viruses in CD8 T cells and B cells during this initial phase of infection; (iii) plateauing of CD4 cell virus burden accompanied by escalation in CD8 and B cell provirus burdens after 4 weeks; (iv) extensive infection of haemopoietic and circulating myeloid cells. FeLV-FAIDS 61E and 61C replication kinetics and lymphocyte tropisms were similar in blood and lymph nodes, where provirus burdens ranged from 0.15 to 1.0 copy/cell. Moreover, virus infection was productive; 8-48 percent of blood lymphocytes, 35-81 percent of node lymphocytes and 53-98 percent of bone marrow cells expressed FeLV capsid antigen (p27 Gag). These findings suggest that the immunosuppressive potency of FeLV-FAIDS reflects the unique cytopathicity rather than unique cytotropism of its 61C (versus 61E) component.

The initial replication of lactate dehydrogenase-elevating virus (LDV) in mice, its invasion of the central nervous system (CNS) and infection of anterior horn neurons in C58 and AKXD-16 mice were investigated by Northern and in situ hybridization analyses. Upon intraperitoneal injection, LDV replication in cells in the peritoneum was maximal at 8 h post-infection (p.i.). Next, LDV infection was detected in bone marrow cells and then in macrophage-rich regions of all tissues investigated (12 to 24 h p.i.). By 2 to 3 days p.i., LDV RNA-containing cells had largely disappeared from all non-neuronal tissues due to the cytocidal nature of the LDV infection of macrophages. In the CNS at 24 h p.i. LDV replication was very limited and confined to cells in the leptomeninges. LDV replication in the cells of the leptomeninges should result in the release of progeny LDV into the cerebrospinal fluid and thus its dissemination throughout the CNS. However, in C58 and AKXD-16 mice, which are susceptible to paralytic LDV infection, only little LDV RNA and few LDV-infected cells were detectable in the spinal cord until at least 10 days p.i. Extensive cytocidal infection of anterior horn neurons occurred only shortly before the development of paralytic symptoms between 2 and 3 weeks p.i. The reason for the relatively long delay in LDV infection of anterior horn neurons is not known. No LDV RNA or LDV RNA-containing cells were detected in the brain, except in the leptomeninges at early times after infection.