A novel parvovirus (family Parvoviridae) in a freshwater fish, zander (Sander lucioperca)

In this study, a novel parvovirus (zander/M5/2015/HUN, OK236393) was detected in faecal specimens from a fish – zander or pikeperch (Sander lucioperca) – and genetically characterized using viral metagenomics and PCR methods. The NS1 and VP1 proteins of zander/M5/2015/HUN share <30% aa sequence identity, respectively, with the corresponding proteins of known members of the family Parvoviridae. Out of 62 faecal specimens collected from 13 freshwater fish species, three (4.8%) samples were positive by PCR for the novel parvovirus – all from zander. This is the second parvovirus detected in fish – after the disease-causing tilapia parvovirus of the subfamily Hamaparvovirinae – and it potentially represents a novel genus in the subfamily Parvovirinae.

Modulation of the expression of the transcription factor Max in rat retinal ganglion cells by a recombinant adeno-associated viral vector

Exclusion of the transcription factor Max from the nucleus of retinal ganglion cells is an early, caspase-independent event of programmed cell death following damage to the optic axons. To test whether the loss of nuclear Max leads to a reduction in neuroprotection, we developed a procedure to overexpress Max protein in rat retinal tissue in vivo. A recombinant adeno-associated viral vector (rAAV) containing the max gene was constructed, and its efficiency was confirmed by transduction of HEK-293 cells. Retinal ganglion cells were accessed in vivo through intravitreal injections of the vector in rats. Overexpression of Max in ganglion cells was detected by immunohistochemistry at 2 weeks following rAAV injection. In retinal explants, the preparation of which causes damage to the optic axons, Max immunoreactivity was increased after 30 h in vitro, and correlated with the preservation of a healthy morphology in ganglion cells. The data show that the rAAV vector efficiently expresses Max in mammalian retinal ganglion cells, and support the hypothesis that the Max protein plays a protective role for retinal neurons.

Production of recombinant H1 parvovirus stocks devoid of replication-competent viruses

Vector and helper plasmids for the production of recombinant H1 (rH1) parvovirus, an oncolytic virus and candidate vector for cancer gene therapy, were constructed with the aim of reducing the contamination of these preparations with replication-competent viruses (RCV). Split-helper plasmids were constructed by manipulating the splicing signals for the capsid proteins such that VP1 and VP2 were expressed from separate plasmids. H1 vectors with similarly mutated splice sites were packaged, using the split-helper plasmids, and the resulting recombinant H1 viruses were completely free of RCV because the generation of recombinants expressing both capsid proteins was prevented. Vector yields of rH1 produced with split-helper plasmids in combination with splice site-modified vectors were similar (in the range of 10(7) replication units/ml) to yields of rH1 produced with the standard vector/helper pair, in which case significant levels of RCV were generated (10(4)-10(5) plaque-forming units/ml). To assess the functionality of this approach in vivo, rH1 was produced that contained the human interleukin 2 (IL-2) transgene and that was devoid of RCV. This IL-2-carrying rH1 vector expressed IL-2 efficiently in human tumor cells (HeLa) in vitro and generated antitumor responses in nude mice xenografted with HeLa cells that had been infected ex vivo with this virus. These results should allow the large-scale production of recombinant oncotropic parvoviruses and their assessment for the gene therapy of cancer in a clinical setting.

The packaging capacity of adeno-associated virus (AAV) and the potential for wild-type-plus AAV gene therapy vectors

Because of its ability to integrate chromosomally and its non-pathogenic nature, adeno-associated virus (AAV) has significant potential as a human gene therapy vector. Here we investigate the maximum amount of DNA which can be inserted into the AAV genome and still allow efficient packaging into an infectious virus particle. Altered wild-type AAV genomes were constructed with inserts, which increased in size by 100 bp, ligated at map unit 96. These large wild-type-plus genomes were able to replicate and produce infectious virus, at levels slightly reduced but comparable to normal sized wild type, until the insert size reached 1 kb. These data indicate that the maximum effective packaging capacity of AAV is approximately 900 bp larger than wild type, or 119%. Furthermore, it is demonstrated that these large AAV genomes are able to latently infect cells by chromosomal integration as does wild-type AAV. These data suggest that therapy vectors carrying a foreign gene of 900 bp or less can be generated from AAV, by ligation into non-essential locations, and result in a recombinant AAV virus with a fully wild-type phenotype. Such wild-type-plus AAV vectors will have both advantages and disadvantages over defective recombinant AAV virus - the most important advantages being the ease in which high titers of infectious virus can be generated and the ability to specifically integrate within chromosome 19. Once the concern subsides over the presence of wild-type AAV in clinical applications, wild-type AAV vectors may find specific application niches for use in human gene therapy.

Management and outcomes of pregnancies complicated by human B19 parvovirus infection: a prospective study

During a large statewide outbreak of fifth disease in Connecticut in 1988, 39 pregnant women were identified who had serologic evidence of recent human B19 parvovirus infection. The patients were followed up prospectively with targeted fetal ultrasonographic examinations to detect signs of fetal hydrops. Of these 39 pregnant women, 37 had healthy infants and two patients had miscarriages. None of the fetuses developed hydrops. We propose that pregnant women exposed to B19 parvovirus be tested for evidence of IgG and IgM B19-specific antibodies and that targeted fetal ultrasonography be considered when IgM antibodies are found. Percutaneous umbilical blood sampling and intrauterine transfusion can be considered in cases of B19 parvovirus-associated hydrops and anemia. The overall fetal loss rate in this prospective follow-up group was 5%.

Charge configurations in viral proteins

The spatial distribution of the charged residues of a protein is of interest with respect to potential electrostatic interactions. We have examined the proteins of a large number of representative eukaryotic and prokaryotic viruses for the occurrence of significant clusters, runs, and periodic patterns of charge. Clusters and runs of positive charge are prominent in many capsid and core proteins, whereas surface (glyco)proteins frequently contain a negative charge cluster. Significant charge configurations are abundant in regulatory proteins implicated in transcriptional transactivation and cellular transformation. Proteins with charge structures are much more predominant in animal DNA viruses as compared to animal RNA viruses and prokaryotic viruses. This contrast might reflect the role of protein charge structures in facilitating competitive virus-host interactions involving the cellular transcription, translation, protein sorting, and transport apparatus.

Virucidal efficacy of physico-chemical treatments against coronaviruses and parvoviruses of laboratory animals

Virucidal efficacy of chemical disinfectants, heating and ultraviolet radiation against mouse hepatitis virus (MHV), canine coronavirus (CCV), Kilham rat virus (KRV) and canine parvovirus (CPV) were examined. Coronaviruses (MHV and CCV) were inactivated by ethanol, isopropanol, benzalkonium chloride, iodophor, sodium hypochlorite, sodium chlorite, cresol soap and formaldehyde as well as by heating at 60 degrees C for 15 minutes, whereas parvoviruses (KRV and CPV) appeared to be inactivated by disinfectants such as formaldehyde, iodophor, sodium hypochlorite and sodium chlorite. Parvoviruses were stable under heating of up to 80 degrees C for 30 minutes. Ultraviolet radiation inactivated all viruses within 15 minutes. No significant differences in stability against physico-chemical treatments were seen between viruses in the same group.

Risk of adverse outcomes of pregnancy after human parvovirus B19 infection

Human parvovirus B19 (B19) infection during pregnancy has been associated with fetal deaths. We conducted several studies to develop data needed to make recommendations for preventing fetal death associated with infection. In the first study, after an outbreak of B19 infection, specimens of cord blood from 47 infants with congenital anomalies, 10 with suspected intrauterine infection, and gestational age-matched controls were tested for IgG and IgM antibodies to B19. None had evidence of recent infection. Next, 192 women with unknown exposure to B19 who had stillbirths or spontaneous abortions were studied. Two patients and two controls had evidence of recent B19 infection. In a second case-control study of women who had stillbirths after outbreaks of erythema infectiosum in area schools, none of the 20 patients or 26 controls were IgM positive at the time of delivery. The rate of infection, as demonstrated by IgM positivity, among 267 pregnant control subjects was approximately 1%. These studies suggest that among pregnant women unselected for exposure to B19, neither infection nor stillbirths are common.

[Development and basic properties of the viral preparation viroden]

Laboratory studies demonstrated the effectiveness of viroden preparation in different doses against preimago stages of Aedes aegypti mosquitoes. After treatment of larvae of instar 1 at preimago stages about 77% of the insects died. The preparation is stable on storage and resistant to unfavourable environmental factors: sun radiation, heating, pH variations, without significant loss of activity. The study of the host range of densonucleosis virus, the active principle of the viroden preparation, showed that it was not harmful for other animals. Large-scale trials of the preparation in different climatic zones are necessary for the elucidation of its effectiveness against naturally occurring mosquito species.

Variation of erythroid and myeloid precursors in the marrow and peripheral blood of volunteer subjects infected with human parvovirus (B19)

Infection of normal individuals with human parvovirus (B19) results in a mild disease (erythema infectiosum) but gives rise to aplastic crises in patients with chronic hemolytic anemias. The effects of this disease on hemopoiesis were investigated following intranasal inoculation of the virus into three volunteers. A typical disease ensued with a viremia peaking at 9 d. Marrow morphology 6 d after inoculation appeared normal but at 10 d there was a severe loss of erythroid precursors followed by a 1-2-g drop in hemoglobin, and an increase in serum immunoreactive erythropoietin. Erythroid burst-forming units (BFU-E) from the peripheral blood were considerably reduced, starting at the time of viremia and persisting for 4-8 d depending on the individual. Granulocyte-macrophage colony-forming units (CFU-GM) were also affected but the loss started 2 d later. Both CFU-GM and BFU-E showed a sharp overshoot at recovery. In the marrow, BFU-E and CFU-E were reduced at 6 and 10 d in the individual having the longest period of peripheral progenitor loss. In contrast, there was an increase in BFU-E and CFU-E in the subject with least change in peripheral progenitors. In the third subject, with an intermediate picture, there was a loss at 6 d but an increase at 10 d of erythroid progenitors. It is suggested that the architecture of the marrow might partially isolate progenitors from high titers of virus in the serum and individual variation in this respect might give the results observed.

Human parvovirus B19-induced epidemic acute red cell aplasia in patients with hereditary hemolytic anemia

From March to August 1984, 26 patients with hereditary hemolytic anemia in northeastern Ohio developed acute, profound red cell aplasia. The patients included 14 males and 12 females 2 to 23 years old, with sickle cell anemia (20 cases), hemoglobin SC-disease (4 cases), sickle-beta-thalassemia (1 case), or hereditary spherocytosis (1 case). All had an acute onset of severe reticulocytopenia and anemia and prodromal symptoms of illness including fever, abdominal symptoms, headache, and arthralgias. Twenty-two received transfusions. Reticulocytosis occurred spontaneously within 2 to 14 days of presentation. In five acute-phase sera, 10(8) to 10(12) viral particles/mL were detected by electron microscopy. Human parvovirus B19 DNA was demonstrated in high concentration by hybridization in the same five acute-phase sera and in low concentration in sera of eight additional patients. The five highly viremic sera inhibited erythroid colony formation in vitro. B19-specific IgM was detected in sera of 24/26 patients, and B19-specific IgG in 21 of 22 patients tested. Our results indicate that human parvovirus B19 was the etiologic agent in this large epidemic of life-threatening acute red cell aplasia in patients with hereditary hemolytic anemia.

Pasteurization of antihemophilic factor and model virus inactivation studies

Heating sterilized albumin preparations at 600 degrees C for 10 hours has historically been shown to yield a hepatitis-free, efficacious product. We have evaluated such a pasteurization procedure with AHF preparations. Procoagulant activity and fibrinogen stability were dependent on the amount of sucrose used as a stabilizer. Flash pasteurization at 72 degrees C was evaluated and was found to be detrimental to AHF. Effect of sucrose concentration was shown on the inactivation kinetics of porcine parvovirus. In the absence of other stabilizers, increased sucrose can provide increased thermoresistance to the virus in 2.5% albumin.

The role of palindromic and non-palindromic sequences in arresting DNA synthesis in vitro and in vivo

The nature of specific DNA sequences that arrest synthesis by mammalian DNA polymerase alpha in vitro was analyzed using circular, single-stranded M13 or phi X174 virion DNA templates annealed to a unique, terminally labeled, DNA primer. This method rigorously defined both the starting nucleotide position and the direction of synthesis, as well as making the amount of radioactivity proportional to the number rather than the length of nascent DNA chains. The precise nucleotide locations of arrest sites were determined over templates with complementary sequences by cloning unique DNA restriction fragments into M13 DNA and isolating virions containing either the Watson or Crick strand. Results were correlated with the locations of palindromic (self-complementary) sequences, repeated sequences, and repeated sequences with mirror-image orientation. Two classes of DNA synthesis arrest sites were identified, distinct in structure but equivalent in activity. Class I sites consisted of palindromic sequences that formed a stable hairpin structure in solution and arrested DNA polymerase on both complementary templates. The polymerase stopped precisely at the base of the duplex DNA stem, regardless of the direction from which the enzyme approached. Class II sites consisted of non-palindromic sequences that could not be explained by either secondary structure or sequence symmetry elements, and whose complementary sequence was not an arrest site. Size limits, orientation and some sequence specificity for arrest sites were suggested by the data. Arrest sites were also observed in vivo by mapping the locations of 3'-end-labeled nascent simian virus 40 DNA strands throughout the genome. Arrest sites closest to the region where termination of replication occurs were most pronounced, and the locations of 80% of the most prominent sites appeared to be recognized by alpha-polymerase on the same template in vitro. However, class I sites were not identified in vivo, suggesting that palindromic sequences do not form hairpin structures at replication forks.

Experimental viral myocarditis: parvoviral infection of neonatal pups

Myocarditis was produced in seronegative five-day-old pups by oral and by intraperitoneal inoculation of canine parvovirus. The disease was subclinical. Histologic lesions were compatible with, but less extensive than, those seen in naturally occurring canine parvoviral myocarditis. In pups necropsied 23 days after inoculation, scattered cardiac myocytes contained intranuclear inclusion bodies, and virus-infected myocytes were demonstrated by immunofluorescence. Degeneration and loss of cardiac myocytes usually was not associated with a cellular infiltrate. At 51 days after inoculation, the myocardium contained an extensive lymphocytic infiltrate which was sometimes associated with fragmented myocytes, and was often contiguous with areas of interstitial fibrosis. At 108 days after inoculation, inflammatory lesions had regressed, and there were multifocal areas of myocardial fibrosis.

Hypothesis: the aplastic crisis of hereditary spherocytosis is due to a single transmissible agent

Aplastic crisis in sickle cell anaemia has been associated with infection by a serum parvovirus-like virus (SPLV). Reports of outbreaks of these crises in hereditary spherocytosis (HS) were investigated to see if the data were consistent with a single agent such as SPLV being their cause. The age distribution of the cases and the pattern of spread were compatible with an infectious aetiology. The symptoms and duration of the cases, and the intervals between them, were sufficiently uniform to indicate that they were caused wholly or predominantly by a single agent with an incubation period of about nine days. There were close similarities between these illnesses and recognised cases of SPLV infection. It is concluded that SPLV is probably the main cause of aplastic crisis in HS.

Farm studies of porcine parvovirus infection

Epizootics of reproductive failure associated with porcine parvovirus infection were investigated on 38 farms. Mummification was common to all epizootics. The mean number of mummified fetuses per affected litter was 3.1. Mean number of pigs born alive for gilts and sows farrowing litters with mummified fetuses was 5.0, but for sows without mummified litters on the same farms it was 9.0. Mummified fetuses were observed in aborted litters on 8 (21.1%) farms. Gilts and sows that appeared pregnant but "lost" their swollen abdomens and failed to farrow were observed on 12 (39.5%) farms. Delayed return to estrus was evident on only 3 (7.9%) farms with a continuous farrowing program. On 21 farms with a batch farrowing program, only 2 (10%) epizootics involved more than 1 batch. Up to 100% of the pregnant swine in the group farrowing together produced mummified pigs, but less than 20% of the breeding herd was affected in 26 (68.4%) cases. The prevalence of disease was not related to herd size, housing, or farrowing management.

Naturally occurring lethal parvovirus infection of juvenile and young-adult rats

A lethal disease characterized by hemorrhage and necrosis of the brain, testes, and epididymides developed in young adult rats housed in specific pathogen free quarters. Morphological, virological, and serological investigations of the outbreak indicated that the probable causative agent was rat virus (Kilham), a common parvovirus of rats that usually induces persistent, asymptomatic infection in adult rats.

Inhibition of 7,12-dimethylbenz(a)anthracene-induced tumors in Syrian hamsters by prior infection with H-1 parvovirus

Hamsters, given injections s.c. at birth of H-1 parvovirus and 1 month later given a single injection of 7,12-dimethylbenz(a)anthracene, had a 38% tumor incidence compared with a 95% incidence in animals receiving 7,12-dimethylbenz(a)anthracene alone. Thus, H-1 which, it has already been shown, invokes a resistance to the incidence of spontaneous and adenovirus-induced neoplasms in hamsters also produces a suppression of a carcinogen-induced tumor in these animals; this suggests that the H-1-induced barrier to successful oncogenesis by these diverse agents has a common mechanism which, present experiments indicate, is not related to a positive or negative H-1 serology. The pathology of the 7,12-dimethylbenz(a)anthracene-induced tumors was similar for both control and H-1-infected hamsters. Although all but one of the primary neoplasms were anaplastic fibrosarcomas as reported previously by others, 25% of the affected females had, in addition, mammary adenocarcinomas, an extremely rare tumor in hamsters.

Canine parvovirus infection in Australia during 1980

A questionnaire sent to all veterinary practitioners in Australia and many in New Zealand asking for details of their experience with canine parvovirus infections in 1980 elicited the following information. In 1980 explosive outbreaks of disease occurred in most parts of Australia. There was no obvious pattern of spread over the continent as a whole. In many cases outbreaks in country areas occurred after dog shows. Canine parvovirus enteritis affected all age groups with an overall mortality of 16 per cent. While the death rate in the young was high, most dogs responded well to fluid therapy. Canine parvovirus did not appear to be associated with clinical entities other than gastroenteritis and myocarditis. No connection with reproductive problems was established. Killed canine parvovirus vaccines were used extensively after the initial release for sale in July 1980. The vaccines appeared to be safe and effective at least in the short term. Problems arose only in vaccination of very young animals.

[Parvovirus enteritis and myocarditis in a confined colony of beagles. (The 1st detection of parvovirus infection in Czechoslovakia]

A description of the findings in a parvoviral epizooty, having occurred in a confined colony of 250 Beagle dogs in the autum and winter 1979-1980 and in 1981, is presented. 5 of the four month-old and older dogs perished in the course of an enteritic form of infection; 5 puppies, younger than 3 months, belonging to a group of 12 puppies derived from two infected litters, died in consequence of a parvoviral myocarditis. The simultaneous occurrence of myocarditis and enteritis was observed in a 9 day-old puppy. Among the seven remaining animals, two dogs were sacrificed at the ages of 18 and 23 months, respectively. Scars were found in the wall of the left ventricle of both of them. Parvoviral enteritis preceded the occurrence of parvoviral myocarditis. Characteristic intramuscular inclusions were demonstrated both in the enterocytes and in the myocardial cells. Electronmicroscopically particles of the size of the parvoviruses could be demonstrated in the nuclei of the myocardial cells, on one hand, and regressive changes of the nuclear components observed on the other hand.

[Acute viral enteritis in dogs]

The results of a post-mortem examination of 15 dogs suffering from acute viral infection probably of parvoviral etiology, are described. The characteristical finding was an acute catarhally hemorrhagic or even a hemorrhagically necrotic enteritis, eventually a colitis with isolated intranuclear inclusions in the epithelium of the crypts, there was also a marked depletion of lymphocytes in the lymphatic organs and some atrophy of the bone marrow.

Experimental infection of conventional dogs with canine parvovirus

Four 6-week-old conventional pups were inoculated with a parvovirus (PV) isolated from the feces of a dog with naturally occurring enteritis. Blood for hematologic studies, virus isolation (VI), and antibody titration and feces for VI and negative-contrast electron microscopy were collected on day 0 and daily until necropsy. Beginning at postinoculation day 2, necropsies were done and specimens were collected for immunofluorescence, VI, and light microscopic examination. The PV infection was confirmed by VI, immunofluorescence, electron microscopy, and seroconversion. Clinical illness was not observed in inoculated pups, although mild intestinal lesions similar to those of naturally occurring PV enteritis were found. The failure to elicit severe disease in conventional pups indicates that one or more factors, such as intercurrent enteric or systemic infections, immune status, age, nutrition, virulence of virus, dose of infectious virus, and route of inoculation influence the clinical and pathologic manifestations of PV infection.

Canine parvovirus infection potentiates canine distemper encephalitis attributable to modified live-virus vaccine

Twelve gnotobiotic dogs from 2 litters were allotted to 3 groups. Group A dogs received a modified-live polyvalent (canine distemper, adenovirus type 2, and parainfluenza virus and Leptospira -canicola-icterohemorrhagiae bacterin) vaccine 3 days prior to oral inoculation with canine parvovirus (CPV). Group B dogs received CPV alone. Group C dogs received 1 dose of vaccine only. In none of the 9 CPV-inoculated dogs did clinical signs of CPV infection develop, although high serum antibody titers for CPV developed in all of them. However, in 2 of the 5 CPV-inoculated vaccinates, canine distemper virus encephalomyelitis subsequently developed. The results suggested that CPV exerts an immunomodulating effect on canine immune responses and may be responsible for vaccination failures in dogs.

Radiographic appearance of canine parvovirus enteritis

Sixty dogs with serologically proved parvovirus infection were radiographically evaluated for signs of gastrointestinal disease. Patient grouping was based on duration of illness, which correlated generally with severity of clinical signs. Early in the disease, the radiographic appearance usually was normal. As the disease progressed, abnormal gas and fluid distention of the small bowel became evident. Contrast radiographic findings usually were normal early in the disease but became abnormal as the disease progressed. Vomiting of the contrast agent, delayed gastrointestinal transit time, flocculation, and abnormal bowel patterns were observed frequently. It was concluded that noncontrast radiographic features of canine parvovirus enteritis often were similar to those identified in other gastrointestinal disorders and, therefore, were not always specific for the disease. Results of contrast radiography, however, were highly specific for parvovirus enteritis. Intestinal contrast examination was believed to be a reliable means of differentiating parvovirus enteritis from clinically similar disorders and in ruling out primary or secondary intestinal obstruction. The duration of illness was correlated with the number, severity, and nature of radiographic signs.

Toxigenic Clostridium perfringens from a parvovirus-infected dog

A strain of Clostridium perfringens, type A, has been isolated from the intestine of a dog which died from parvovirus infection. This Clostridium strain produces a toxin which can be detected by counterimmunoelectrophoresis, using C. difficile antitoxin, and produces cytotoxicity in WI-38 cell culture. Cytopathology can be blocked by C. difficile antitoxin. Its role in canine parvovirus infection is unknown.

Reproductive performance of gilts exposed to porcine parvovirus at 56 or 70 days of gestation

A total of 18 pregnant gilts, which were free of antibody for porcine parvovirus (PPV), were exposed oronasally to PPV on either the 56th day (9 gilts) or 70th day (9 gilts) of the gestation to determine whether infection at these times would affect their reproductive performance. The gilts were either necropsied late in gestation or allowed to farrow, and their fetuses and pigs were tested for evidence of infection. Gilts remained clinically healthy throughout the experiment, and none farrowed prematurely. litters of 7 of 9 gilts exposed to PPV at 56 days of the gestation were infected transplacentally, and PPV caused death of fetuses in 5 of the infected litters. These litters comprised 29 dead fetuses (2 to 12/litter) and 31 live fetuses or pigs (1 to 10/litter). In addition, PPV may have been directly or indirectly responsible for an increased frequency of stillbirth and neonatal death, but the role of PPV in these conditions was difficult to assess. Litters of 6 to 9 gilts exposed to PPV at 70 days of the gestation also were infected transplacentally, but in contrast to earlier infection, PPV did not cause fetal death in these litters.

Activity of some enzymes involved in "adenylate cycle" in rat embryo cells infected with parvoviruses (X14, H-1)

In rat embryo cell cultures infected with X14 or H-1 parvovirus and in mock-infected cell cultures the activity of some enzymes involved in purine nucleotide interconversion and in "adenylate cycle" was determined. The enzymatic activities have been assayed on 100,000 x g supernatant by spectrophotometric methods, measuring the absorbance variation in U.V. and by radiometric methods, resolving the radioactive products of reaction by TLC on PEI cellulose. The results indicated a decrease of the enzymatic activities that degrade purine nucleosides and nucleotides in infected cells compared to the controls. Some different behaviour patterns showed the enzymes involved in base salvage pathway; adenine phosphoribosyltransferase did not show a significant modification of activity, whereas hypoxanthine (guanine) phosphoribosyltransferase increased slightly in X14 virus-infected cells. The behaviour of the above mentioned enzymatic activities may be considered as a mechanism of purine nucleotide saving, coupled to an active salvage pathway for the synthesis of nucleotides required for the viral replication.

Pool and synthesis of phosphoribosylpyrophosphate in rat embryo cells infected with X14 or H-1 parvovirus

In rat embryo cell cultures infected with X14 or H-1 parvovirus the PRPP pool and the PRPP synthetase activity have been assayed. A radiometric method, prepared by Authors, based on the conversion of [6-14C) orotate to [6-14C) UMP by the mixed enzyme orotate phosphoribosyltransferase and orotidylate decarboxylase and on the separation of UMP by ascending chromatography, has been utilized. The PRPP pool and te PRPP synthetase activity appeared nearly unmodified in the cells infected with X14 or H-1 parvovirus compared to the mock-infected cells. Therefore, the lowered pyrimidine nucleotide synthesis in infected cells, shown in previous studies, may depend, rather than on the diminished PRPP pool, on the lower PRPP utilization; in fact, some inhibition by metabolites, that may be removed by added PRPP, might occur in the infected cells.

Outbreak of aplastic crises in sickle cell anaemia associated with parvovirus-like agent

Since 1952, 112 children with sickle cell anaemia (SCA) in Jamaica have had an aplastic crisis. Outbreaks occurred in 1956, 1960, 1065-67, 1971-73, and 1979-80. Most cases occurred in children under 10 years of age, and an aplastic crisis in a patient over the age of 15 years is rare. There were 38 cases in 1979-80 and stored serum specimens from 28 of these were available for virus studies. Evidence for infection with a parvovirus-like agent was found in 24 of these 28 cases. Viral antigen was detected in 2 patients, both of whom demonstrated seroconversion. Seroconversion during 1980 was detected in a further 7, increasing amounts of antibody during the convalescent period were found in 5, antibody was found in 2 of 4 patients from whom only an acute phase specimen was available and the remaining 10 were antibody positive in the only convalescent phase sample available for testing. Antibody was found in 4 of 94 controls with the SS genotype (in retrospect 2 of these may have had an aplastic crisis) and in 17% of 48 controls with a normal haemoglobin (AA) genotype. The results accord with the possibility that the parvovirus-like agent is the principal cause of aplastic crisis in SCA.

Secondary infection of rat lungs with Pasteurella pneumotropica after Kilham rat virus infection

Lung congestion was observed after an outbreak of Kilham rat virus infection (KRV) in a rat colony, previously free of all rat viruses. A high proportion of congested lungs contained Pasteurella pneumotropica suggesting that KRV might have caused primary damage to the alveoli (hitherto not recorded) which allowed the secondary bacterial colonization. Experimental infection of rats with KRV caused acute damage to the lung alveoli. Since KRV infection is very common in animal facilities it could therefore be a significant agent in the development of respiratory disease.

Experimental parvovirus infection in dogs

Five eight week old dogs were inoculated orally and intranasally with cell culture origin canine parvovirus. Three dogs became depressed and anorectic and developed a mild (one dog) to severe diarrhea five days postinfection. The remaining dogs had subclinical infections but developed a lymphopenia followed by a transient lymphocytosis. The ill dogs developed mild (one dog) to severe neutropenia and a moderate lymphopenia. One died nine days postinfection. Recovery was associated with cessation of viral excretion and with lymphocytosis and antibody production. Two of three dogs challenged intragastrically developed mild clinical signs and a moderate panleukopenia four to eight days postinfection. The pathological changes of the experimental disease were very similar to that of spontaneous disease. Bone marrow changes included a severe granulocytic and mild erythroid depletion. The pathogenesis of canine parvovirus infection is discussed.