[Bacterial contamination of eyedrops in clinical use]

PURPOSE

The aim of this study is to assess the importance of bacterial contamination of multidose eyedrops in a routine clinical setting.

MATERIAL AND METHODS

406 eyedrop vials were cultured about one week after clinical use: 204 collected from an Ophthalmic Department, and 202 from a Nursing Home. The microbiological analysis was performed on the tip and the residual eyedrop, counting the number of bacterial colonies.

RESULTS

66 (16.3%) from the 406 analyzed vials were contaminated, and 5.4% out of these were severely affected. There was no significant difference between the "Ophthalmic Department" and the "Nursing Home". Commensal germs were the most frequently encountered in both groups. 4 gram negative organisms were isolated from the "Nursing Home" group.

CONCLUSION

These results are in agreement with the literature. Comparison between our two groups is difficult because the eyedrops and uses were different. However, we notice the presence of gram negative organisms in the "Nursing Home". These severe contaminations due to opportunistic pathogen organisms are rare (0.75%), probably underestimated, and represent a real infectious risk during instillation. The study of the contamination site shows that the eyedrop is more often contaminated than the tip. This can be in relation to germ desicsation and to an aspiration phenomenon of contaminated fluid at the tip level. At last, the role of preservatives is not sufficient to ensure the sterility of multidose eyedrops during their use, and this justifies safer (single dose or filtration system) eyedrop vials.

The isolated perfused porcine liver: assessment of viability during and after six hours of perfusion

Isolated liver perfusion was developed for the study of liver physiology and preservation. The recent development of new perfusion devices and appropriate liver preservation solutions prompted us to reconsider liver perfusion for the specific purpose of evaluating viability in terms of biochemical changes, paying special attention to modifications in the histological ultrastructure. Twenty-two isolated pig livers were perfused with autologous blood. Arterio-portal perfusions were carried out using an extracorporeal perfusion circuit with a hollow fibre membrane oxygenator. Four groups of pig livers were studied using three different liver flushing solutions [Ringer's lactate, ELOHES, and University of Wisconsin (UW)] and two different oxygenation modalities. Liver function tests and histological studies were done. Our results revealed that a high partial oxygen pressure (PO2) level was deleterious to the ultrastructural elements of hepatocytes, in particular to the mitochondria. It was also associated with deficient metabolic performance, i.e., poor bile production and lack of aerobic metabolism. Normal blood gas values could be obtained with the use of air for liver oxygenation. Flushing of the liver with Ringer's lactate or a macromolecular solution such as ELOHES was associated with severe liver cell injuries, as reflected by a marked rise in liver enzymes and histological lesions. Satisfactory results were obtained when UW solution was used for liver harvesting. We conclude that an appropriate liver preservation solution, normal blood gas values, and normal physiological arterio-portal pressure and blood flow are essential for appropriate liver function with preservation of liver architecture and of hepatocyte ultrastructures. Total bilirubin in bile and Factor V are sensitive indicators of good liver function.

Expression of a NK cell-restricted epitope on decidual large granular lymphocytes

Decidual large granular lymphocytes (DLGL) are the most abundant lymphoid cell type found in the first trimester maternal decidua. The function of DLGL remains controversial, although freshly isolated DLGL have been shown to exert a weak NK activity. We report here the phenotypic characterization of two DLGL subpopulations by immunofluorescence, using mAb against CD56, PEN5 as well as adhesion molecules potentially involved in cell-cell contact between DLGL and trophoblasts. DLGL are CD56bright and express the CD2, CD11a, CD18, CD38 and CD50 molecules, dimly the CD54 molecule, and poorly the CD102 and CD69 molecules. A strong expression of the polysialylated form of N-CAM (or CD56) was also observed on the surface of DLGL. Finally, 40% of CD56bright DLGL cells express the PEN5 epitope, which is selectively expressed on CD56dim cells NK in the peripheral blood. No other phenotypic difference was detected between the CD56brightPEN5+ and the CD56brightPEN5- DLGL populations. Our results show that DLGL are heterogeneous and suggest that the CD56brightPEN5+ DLGL subset belongs to the classical NK cell lineage.

Strong increase in the percentage of the CD8bright+ CD28- T-cells and delayed engraftment associated with cyclosporine-induced autologous GVHD

Four children with acute lymphoblastic leukaemia had autologous bone marrow (BM) or peripheral stem cell (PSC) transplantation with low dose of cyclosporine (CsA, img/kg/d i.v. during the first 28 d) to induce an autologous GVHD (auto-GVHD). Two children did not have clinical auto-GVHD and they relapsed 3 and 4 months after treatment. The 2 other children had clinical signs of auto-GVHD (grade I and grade II); they both are in complete remission but after a first normal haematological recovery they had a prolonged period of aplasia until month 9 for 1 patient and still persistent at month 7 in the other case. We studied lymphocyte subsets reconstitution after transplantation in these patients. All patients had an important decrease in the CD4/CD8 ratio related both to a strong decrease in the CD4+ cells and a strong increase in the CD8+ cells. Most of the CD8+ cells were of the CD8bright+ CD28- phenotype. These CD8bright+ CD28- T-cells represented from 33% to 68% of the total lymphocytes. We discuss the role of these cells after autologous transplantation with CsA, and wonder if these cells could mediate cytotoxicity. In conclusion, among 4 children who received autologous BM or PBC transplantation with low dose of CsA, we observed a complete remission after an auto-GVHD and a prolonged period of aplasia in 2 patients and a relapse of leukaemia in 2 other patients. All these 4 patients had an increase in the CD8bright+ CD28- T lymphocytes.

RU 41 740 (Biostim) and IL-4, or IL-13, have opposite effects on CD14, CD23, HLA-DR and HLA-DQ on monocytes

RU 41 740 (Biostim) is a glycoprotein extract obtained from Klebsiella pneumoniae. Its immunostimulating properties on monocytes have been established in vivo and in vitro. To confirm its spectrum of action at molecular level we studied its role on the modulation of four molecules involved in antigen presentation (HLA-DR, HLA-DQ), uptake of endotoxin (CD14) and activation (CD23). These four molecules are known to be modulated by interleukins IL-4 and IL-13. We found that HLA-DR, HLA-DQ, CD14 and CD23 were differentially regulated by biostim and IL-4 or IL-13. Surprisingly, Biostim inhibited the IL-4 or IL-13-induced expression of CD23, HLA-DQ and HLA-DR, while it did not have any action on these molecules by itself. We therefore hypothesize that Biostim, through the action on its receptor, could interact with the IL-4 receptor and IL-13 receptor and/or inhibit the IL-4 and IL-13 receptor transducing signal.

[Apheresis tolerance and acceptability in the child weighing 30 kg or less, with the exception of infants]

Over the ten past years, we performed 336 apheresis among 51 children who were 19 months to 15 years old (10 to 30 kg body weight). 3 types of apheresis were carried out. 14 red blood cell exchange, 293 plasma exchanges and 29 peripheral blood stem cell collections (CSP). 5 different types of continuous or discontinuous flow machines have been used. Technical adaptations depending on patient blood volume, hematocrit, type of machine used and apheresis performed permitted us to obtain a very good tolerance and acceptability. According us, the apheresis should be used each time this treatment is needed in the child, because of the very low frequency of side effects.

Lymphocyte subset abnormalities in German shepherd dog pyoderma (GSP)

Peripheral blood lymphocyte subpopulations were studied in 12 German shepherd dogs suffering from deep pyoderma (GSP). Twelve other healthy but matched dogs were used as controls. GSP was found to be associated with an imbalance in the CD4 and CD8 subsets (respectively 37.3 +/- 8.7% and 28.6 +/- 6.6%, as compared to 47.5 +/- 8.8% and 19.3 +/- 4.0% in the controls). The activation markers were not affected by GSP. Moreover, analysis of the B-cell populations showed a striking decrease in the level of CD21 cells (5.5 +/- 3.3% of CD21+ lymphocytes, compared to 12.2 +/- 6.0 in the controls). This study suggests that the immunological imbalance observed in GSP may be associated with defective helper cells, and provides further evidence that dogs suffering from GSP are not immunologically normal reactors.

Development of a simple, rapid and accurate in vitro whole blood technique for the detection and semi-quantification of FIV cellular viremia

A new, simple, rapid and accurate culture technique is described for a semi-quantitative analysis of cellular viremia in FIV-infected cats. This assay can be carried out with small amounts of whole blood, and is based on the detection of FIV core gag antigen, which is released in culture supernatants. The amount of core antigen produced is measured with an enzyme-linked immunoassay using specific monoclonal antibodies. This whole blood technique (WB method) was compared with a culture method using isolated peripheral blood mononuclear cells (PBMC method). FIV could be detected in whole blood of all experimentally infected cats, but not from uninfected cats. This assay offers a number of advantages (small blood samples required, no leukocyte separation and lymphocyte purification procedures) and its reproducibility is very good. It provides a convenient in vitro cellular assay for viral semi-quantitation, well adapted for monitoring efficacy of prototype FIV vaccines or experimental antiviral drugs. Also, it could facilitate the study of the pathogenesis of FIV-related progressive immunodepression. Finally, it offers an alternative to serological techniques for diagnostic purposes in several circumstances: early viremia, maternal antibodies.

[Granulated CD56 lymphocytes of decidual tissue]

The reproduction is a complex mechanism wich is subtly immunoregulated since the semiallogenic fetus is not rejected by the mother. At the feto-maternal tissue interface, where fundamental mechanisms of tolerance occur, a large and unusual lymphocytes population takes place. These cells recruited during the earlier stages of pregnancy are very granulated and express brightly the N-CAM molecule (or CD56) with numerous adhesion and activation molecules. Nevertheless, they seem fonctionnally inactivated. They phenotypically belong to the peripheral blood minor fraction of NK cells which are CD56++CD16-CD3-. Although their function in the establishment of the gestation is not clearly known, because of their phenotypical heterogeneity, they may have two distinct functions: cytotoxicity and suppression. Their cytokine pattern, preferentially of the Th1 type, inform us about their potential functions and their interactions with other cells populations in this tissue, allowing us to understand the main mechanism in the establishment of the pregnancy.

Allogenic BMT in children: differential lymphocyte subset reconstitution according to the occurrence of acute GVHD

To acquire some biological markers associated with the occurrence of acute graft-versus-host disease (aGVHD) after allogeneic bone marrow transplant (BMT) in children, we have studied the lymphocyte subset reconstitution and the percentage of peripheral blood mononuclear cells bearing HLA-DR and HLA-DQ class II molecules. This study included 37 allogeneic BMT: either with (n = 17) or without (n = 20) aGVHD. Within 2 months after transplantation, we observed that patients with aGVHD had a unique mononuclear cell profile characterized by (i) a significant increase in the percentages of CD8bright+CD28- T cells (P = 0.05) and CD3+ T cells (P = 0.001), (ii) an important decrease in the percentage of CD56+ cells (P = 0.0001), and (iii) a decrease in the percentages of HLA-DQ+ and HLA-DR+ monocytes (P = 0.001) and HLA-DQ+ T lymphocytes (P = 0.0001), in comparison with patients without aGVHD. Moreover, statistical studies indicate that there was a positive correlation between CD8bright+CD28- and CD3+ T cells, whereas CD3+ T cells were negatively correlated to CD56+ cells. We did not find any statistical correlation between the percentages of HLA-DQ+ or HLA-DR+ cells and the percentages of these lymphocyte subsets. Therefore, in this study done in children, we suggest that patients with (i) less than 20% of DQ+ monocytes, (ii) less than 25% of CD56+ lymphocytes, and (iii) an enhanced percentage of CD8bright+CD28- T cells are strongly associated with aGVHD. Unfortunately, these biological markers of a GVHD may not precede the clinical manifestations of the disease.

Autoantibodies to histone, DNA and nucleosome antigens in canine systemic lupus erythematosus

Dogs can develop systemic lupus erythematosus syndromes that are clinically similar to those seen in humans. In contrast, previous observations suggest differences in their autoantibody reactivity patterns against histones and DNA which are components of the nucleosome in chromatin. The objective of this study was to assess comprehensively the levels of autoantibodies against histone, DNA and nucleosome antigens in a population of lupus dogs. The specificities of antibodies in lupus and control dog sera were determined using IgM- and IgG-specific reagents in an ELISA against a variety of chromatin antigens. When compared with control sera, IgG antibodies to individual histones H1, H2A, H3 and H4 were significantly higher in the lupus group. In contrast, we did not detect IgG antibodies specific for H2B, H2A-H2B, DNA, H2A-H2B-DNA or nucleosome in lupus dogs. There was no significant increase in any of the IgM specificities tested. Therefore, the reactivity pattern to nucleosome antigens in canine lupus is restricted to IgG antibodies against individual histones H1, H2A, H3 and H4. This stands in contrast with human and murine lupus, where autoantibodies are directed against a wide variety of nucleosomal determinants, suggesting that unique mechanisms lead to the expansion of anti-histone antibody clones in canine lupus. The high incidence of glomerulonephritis in dog lupus suggests that anti-DNA antibodies are not required for the development of this complication, whereas IgG anti-histone antibodies may be relevant to its pathogenesis.

Abnormalities of lymphocyte subsets in canine systemic lupus erythematosus

Canine systemic lupus erythematosus (SLE) is a disease clinically very similar to its human counterpart. But so far, no study has reported an accurate evaluation of the lymphocyte subsets in the canine disease. Here, we present a study in which lymphocyte subsets have been evaluated in the peripheral blood of 20 dogs suffering from spontaneous systemic lupus erythematosus (SLE) in active and inactive phases, before and during treatment with prednisone and levamisole. 22 healthy dogs have been used as a control population. We show that canine SLE in active phases is associated with a several lymphopenia (1050 +/- 520 10(6) cells/l versus 2130 +/- 1 020 10(6) cells/l in controls). A striking finding is the imbalance of the CD4 and CD8 subsets (respectively 56.7 +/- 10.7% and 10.9 +/- 3.8% of CD4+ and CD8+ lymphocytes versus 40.5 +/- 11.5% and 18 +/- 4.4% in controls) and a strong activation of T-cells in active phases (64.1 +/- 16.9% of 2B3+ cells versus 46.5 +/- 16.7%). Moreover, we observed a persistence of the T subset imbalance during spontaneous evolution. In contrast, the treatment induced in dogs showing a good response the correction of CD4/CD8 ratio and no clinical manifestations, whereas in low responders no such improvements were observed. Thus, this work suggests that the main immunological imbalance seen in SLE could be associated with defective suppressor cells and provides further evidence of similarity of human and dog SLE.

Effects of PGE2 upon differentiation and programmed cell death of suspension cultured CD4-CD8- thymocytes

Recently, several works have focused on the modulation of the immune response by arachidonic acid metabolites. Some of these metabolites, such as prostaglandins, have been shown to influence thymocyte "education" in vitro. However, the effect of one of them, prostaglandin E2 (PGE2), in the education of CD4-CD8- double negative immature thymocytes (DN cells) remained unclear. Using a flow cytometry analysis of DN cells cultured for 24 h in the presence of PGE2, we observed, compared with DN thymocytes cultured without PGE2, an increase in the CD4+CD8-CD3- immature thymocytes and in the CD4+CD8- and CD8+CD4- mature single positive thymocytes and a decrease in the DN and CD4highCD8high double positive thymocytes. Other differentiation thymocyte surface markers, such as CD3, CD5, TCR alpha beta, TCR delta gamma and HSAg, revealed an increasing number of thymocytes bearing these first four markers and a lower expression of the HSAg. Furthermore, we observed an accumulation of CD4lowCD8low thymocytes and an increasing proportion of hypodiploid nuclei. These two findings have been shown to be markers of the programmed cell death process. These findings suggest that PGE2 probably acts on thymocyte differentiation through at least two distinct pathways. On the one hand, PGE2 seems to promote differentiation of DN cells into CD4+CD8-CD3- immature cells and drive CD4+CD8+CD3+ thymocyte to a CD4+CD8- and CD8+CD4- mature phenotype. On the other hand, PGE2 is probably implicated directly or indirectly in the increase or the acceleration of the programmed cell death process of immature CD4+CD8+CD3+ thymocytes, which is linked to the positive and/or negative selection.

Selective detection of human hepatitis B virus surface and core antigens in peripheral blood mononuclear cell subsets by flow cytometry

The presence of hepatitis B surface protein (HBs) and hepatitis B core protein (HBc) was investigated, by flow cytometry, on the surface of peripheral mononuclear cells (PBMC) from cells of the following phenotype: CD3 (T lymphocytes), CD4 (T helper/ inducer), CD8 (T cytotoxic/suppressor), CD19 (B lymphocytes) and CD56 [natural killer (NK) cells] among eight patients suffering from chronic hepatitis B and five healthy HBV-negative subjects. This study demonstrated the presence of HBsAg and HBcAg on the lymphocyte surface for most of the patients. The mean percentage of labelled cells was 17% for HBsAg and 15% for HBcAg. Among the different lymphocyte subsets only B lymphocytes and the NK cells expressed HBsAg for 57% and 26% of cells, respectively. Similarly HBcAg was also detected among CD19 and CD56 cells only. Polymerase chain reaction (PCR) was used to search for the presence of hepatitis B virus (HBV) DNA and RNA in PBMC, using primers located in the S gene. HBV DNA was detected with variable intensity in the CD3, CD4, CD19 and CD56 subsets following their separation with a cell sorter. For HBV RNA the signal obtained after PCR and Southern blotting was higher for CD56 and CD19 cells than for CD3 cells and undetectable for CD4 cells. This study demonstrates that replication and transcription of the HBV can occur in CD19- and CD56-positive cells. Positive signals in CD3 cells may be due to contamination of this subpopulation by NK cells.

Effects of intravenous immunoglobulins (IVIG) on peripheral blood B, NK, and T cell subpopulations in women with recurrent spontaneous abortions: specific effects on LFA-1 and CD56 molecules

Polyspecific IgG given intravenously at high dose (IVIG) are increasingly used as an immunomodulating therapy in autoimmune diseases. However, very few studies have dealt with the action of IVIG on the expression of the leukocyte markers. During a clinical trial in which 13 young and healthy women received IVIG to prevent unexplained recurrent abortions we have evaluated by flow cytometry the action of IVIG on 17 clusters of leukocyte differentiation (CD). We found that the IVIG perfusions (0.5 g/kg) induced an increase in the number of polymorphonuclear and monocyte cells in the peripheral blood. This effect lasted 8 days. The IVIG treatment had no effect upon T cell populations stained with antibodies specific for CD2, CD3, CD4, CD8 and on CD4+CD45RA+, CD4+CD29+, CD8+CD28+, CD8+CD28- subpopulations. A weak decrease in the B cell number was observed. The most striking phenomenon was the decrease in the number of CD56+ cells, whereas CD16+ and CD57+ cells were unaltered. By the double-staining technique we showed that CD56+CD16+ cells became CD56-CD16+ cells. Moreover, IVIG decrease the expression level of the LFA-1 molecule on monocytes and lymphocytes. The other adhesion molecules studied remained steady (CD11b, CD49d, CD49e, CD29, CD28, and CD62L). This study has shown that IVIG have no effect on 15 of 17 CD used but downmodulate two adhesion molecules playing a key role in the immune system.

A high percentage of HLA-DQ+ and HLA-DR+ mononuclear cells is associated with a low incidence of acute graft-versus-host disease after allogeneic bone marrow transplantation (BMT) in children

In order to discover some biological markers of acute graft-versus-host disease (aGVHD), we have studied the percentage of peripheral monocytes and T lymphocytes bearing HLA-DR and HLA-DQ class II molecules. This study included 25 allogeneic BMT in children, either with (n = 10) or without (n = 15) aGVHD. Within 2 months after transplantation, a higher percentage of DQ+ and DR+ monocytes and of DQ+ T lymphocytes was observed in patients without aGVHD compared with patients with aGVHD. The most discriminating marker was the strong increase in the percentage of DQ+ monocytes in patients without aGVHD (P = 0.001). In a sequential study, we observed a low percentage of DQ+ and DR+ peripheral blood mononuclear cells (PBMC) as long as the clinical manifestations of aGVHD continued. We speculate if the modulation of DQ and DR molecules on PBMC after BMT is a consequence of the action of some lymphokines, and if it plays a role in the regulation of the acute GVH reaction. We conclude that MHC class II molecules on peripheral mononuclear cells may be reliable biological markers for the diagnosis of aGVHD.

Histone-reactive IgA antibodies in adult IgA nephropathy and other primary glomerulonephritis

The levels of histone-reactive IgA antibodies in the sera of adult patients with IgA mesangial glomerulonephritis, membranous glomerulonephritis, membranoproliferative glomerulonephritis and idiopathic nephrotic syndrome (minimal change disease+segmental glomerulosclerosis+IgM nephropathy) were evaluated by an enzyme-linked immunosorbent assay. Increased levels of IgA antibodies to all five major histones (H1, H2A, H2B, H3, H4) were found in all four disease groups when compared to normal controls. These histone-reactive IgA antibodies were restricted to the IgA1 subclass and their levels did not correlate with the levels of total serum IgA, nor with serum creatinine, creatinine clearance, and 24-hour proteinuria. Increasing ionic strength resulted in only partial inhibition of the binding to histones and, in individual patients, levels of reactivity with individual histones were usually correlated. This study shows that elevated levels of IgA antibodies reactive with self antigens are present in primary glomerulonephritis and extends previous observations indicating that anomalies of the IgA system occur in various forms of primary glomerulonephritis and are not limited to IgA nephropathy.

IgM and IgA rheumatoid factors in canine polyarthritis

IgM and IgA rheumatoid factor (RF) were detected by ELISA using a purified dog IgG as antigen in normal controls (N = 84), dogs with unclassified polyarthritis (N = 95), dogs with rheumatoid arthritis (RA) (N = 22), dogs with systemic lupus erythematosus (SLE) (N = 35), dogs with leishmaniasis or heart worm disease (N = 20) and dogs with pyometra (N = 16). Frequency and titre of IgM and IgA RF are low and comparable (P < 0.05) in dogs with unclassified polyarthritis or RA: respectively 24.2% and 27.3% for IgM RF and 21.0% and 18.2% for IgA RF; the mean titre being respectively 0.781 +/- 0.581 and 0.649 +/- 0.365 for IgM RF, and 0.774 +/- 1.331 and 0.740 +/- 1.169 for IgA RF. The frequencies of IgM and IgA RF are a little higher in dogs with SLE (IgM RF: 37.1%, IgA RF: 25.7%) and higher in dogs with leishmaniasis or heart worm disease (45.0% and 30.0%), especially in dogs with pyometra (68.7% and 37.5%). So, although dogs can produce IgM and IgA RF, these auto-antibodies are uncommon in dogs with RA. Furthermore, when RF are present their titre is much lower than in human RA.

[Demonstration of cell death process by apoptosis in cat lymphocytes infected by FIV (feline immunodeficiency virus)]

Feline immunodeficiency virus (FIV), the causative agent of feline AIDS, induces a disease syndrome in cats characterized by a decreased lymphocyte-proliferative response to mitogens at all stages of infection and selective depletion of CD4 lymphocyte subsets. In this work, we report that peripheral blood lymphocytes isolated from FIV-infected cats undergo a spontaneous death, in vitro, according to a programmed cell death (PCD) or apoptosis. This phenomenon has also been seen in peripheral blood lymphocytes from HIV-infected humans and SIV-infected macaques. Four different techniques were used to document PCD in FIV-infected cats. DNA gel electrophoresis has shown a DNA fragmentation pattern with DNA fragments displaying sizes corresponding to multiples of oligonucleosomes DNA length unit (180 bp). Transmission electron microscopy revealed condensation of both nuclear chromatin and cytoplasm. An increase in the percentage of fragmented DNA was demonstrated by Burton's technique. In addition, flow cytometric analysis detected a cell population with condensed chromatin. The spontaneous PCD in FIV-infected cats could not be inhibited by RNA synthesis inhibitors or protein synthesis inhibitors. Our results could have implications for understanding the pathogenesis of FIV-infection and establishing specific strategies against apoptosis in cats and humans.

Monitoring of early events of experimental woodchuck hepatitis infection: studies of peripheral blood mononuclear cells by cytofluorometry and PCR

The peripheral blood mononuclear cells (PBMC) of woodchucks experimentally infected by woodchuck hepatitis virus (WHV) were examined simultaneously for the presence of membrane associated WHV antigens by cytofluorometry, and for WHV DNA and RNA sequences by the polymerase chain reaction (PCR). Four woodchucks were inoculated: two with a well-defined infectious inoculum and two with an inoculum obtained from an animal at the late incubation phase, which was positive for WHV DNA by PCR but still devoid of WHV markers. Infection was demonstrated in all four inoculated woodchucks by the appearance at different times of WHV DNA and WHV antigens in both leucocytes and serum. WHV DNA was first detected by PCR either in the serum (two cases) or in leucocytes (two cases). The mean percentage of cells positive for membrane associated WHsAg or WHcAg detected by cytofluorometry were 37% +/- 25 and 17% +/- 15 respectively. After 8 weeks, all inoculated animals were WHsAg positive in serum. These data suggest that PBMC are involved in the early events of hepadnavirus infection. They also show that sera which are positive by PCR for WHV DNA may transmit viral infection even while still seronegative for WHV markers and for WHV DNA by dot blot.