Possible ways viral leukemia spreads among the hamadryas baboons of the Sukhumi monkey colony

Leukemia virus transmission was studied during an outbreak of leukemia among the baboons of the Sukhumi monkey colony. First, the possibility of "vertical" transmission of the virus was examined, as the Papio stock in Sukhumi was genetically homogeneous. "Vertical" transmission of the virus from a common ancestor seems unlikely, since cases of leukemia were registered in animals descending from different families. However, there were cases of innate leukemia, when babies born from leukemic parents displayed pronounced signs of leukemia immediately after birth. "Horizontal" transmission of the virus also seems indisputable, because special experiments have shown that imported baboons, even of other species, caged together with leukemic animals, may develop leukemia due to close contact. It was established earlier that the leukemia virus was excreted with urine. Kidneys, lungs, and salivary glands are the possible routes of infection. Thus, the present report aknowledges the possibility of both "horizontal" and "vertical" transmission of leukemia oncornaviruses in primates.

Immune response of healthy and leukemic cats to the feline oncornavirus-associated cell membrane antigen

Feline leukemia is an infectious disease caused by a horizontally transmitted virus. Infection of animals or cultured cells with feline oncornaviruses results in the expression of a specific cell membrane antigen, feline oncornavirus-associated cell membrane antigen (FOCMA). The humoral antibody response to FOCMA is directly correlated with tumor progression. The measurement of this antibody is a useful tool for determining virus exposure. Using this procedure it was determined that cats living in leukemia "cluster" households as well as cats used as contact controls in virus injection experiments have a risk of infection of 90% or higher.

Bovine leucosis virus contamination of a vaccine produced in vivo against bovine babesiosis and anaplasmosis

Contamination of a batch of tick fever (babesiosis and anaplasmosis) vaccine with bovine leucosis virus (BLV) was detected when a herd, in the final stages of an enzootic bovine leucosis (EBL) accreditation program, developed a large number of seropositive cattle following use of tick fever vaccine. Investigations incriminated a single calf used to produce Anaplasma centrale vaccine from which 13,959 doses were distributed. The failure of this calf to give a positive agar gel immunodiffusion (AGID) test before use was not fully explained. A total of 22,627 cattle from 111 herds receiving contaminated vaccine was tested to validate claims for compensation. Results showed infection rates of 62% and 51.8% in vaccinated dairy and beef cattle, respectively, compared with 6.1% and 1.5% in non-vaccinated cattle in the same herds. The results also indicated that infection did not spread from vaccinated to non-vaccinated in-contact cattle. Heavy reliance is now placed on purchase of calves for vaccine production from EBL accredited-free herds and on transmission tests from the calves to sheep to prevent a recurrence of contamination. The need for a BLV antigen detection test, with the sensitivity of the sheep transmission test but simpler and faster to perform, is evident.

Bovine leukaemia: facts and hypotheses derived from the study of an infectious cancer

Bovine leukaemia virus (BLV) is the etiological agent of chronic lymphatic leukaemia/lymphoma in cows, sheep and goats. Infection without neoplastic transformation was also obtained in pigs, rhesus monkeys, chimpanzees, rabbits and observed in capybaras and water-buffaloes. Structurally and functionally, BLV is a relative of human T lymphotropic viruses 1 and 2 (HTLV-I and HTLV-II) In humans, HTLV-I induces a T-cell leukaemia and its type 2 counterpart has been found in dermatopathic lymphadenopathy, hairy T-cell leukaemia and prolymphocytic leukaemia cases. At variance with HTLV-I, BLV has not been associated with neurological diseases of the degenerative type. Bovine leukaemia virus, HTLV-I and HTLV-II show clearcut sequence homologies. The pathology of the BLV-induced disease, most notably the absence of chronic viraemia, a long latency period and lack of preferred proviral integration sites in tumours, is similar to that of adult T-cell leukaemia/lymphoma induced by HTLV-I. The most striking feature of these three naturally transmitted leukaemia viruses is the X region located between the env gene and the long terminal repeat (LTR) sequence. The X region contains several overlapping long open reading frames. One of them, designated XBL-I, encodes a trans-activator function capable of increasing the level of gene expression directed by BLV-LTR and most probably is involved in "genetic instability" of BLV-infected cells of the B cell lineage. The "genetic instability" renders the infected cell susceptible to move, along a number of stages, towards full malignancy. Little is known about these events and their causes; we present some theoretical possibilities. Bovine leukaemia virus infection has a worldwide distribution. In temperate climates, the virus spreads mostly via iatrogenic transfer of infected lymphocytes. In warm climates and in areas heavily populated by haematophagous insects, there are indications of insect-borne propagation of the virus.

Experimental transmission of bovine leukosis virus by simulated rectal palpation

Eight six-month-old Holstein male calves were experimentally inoculated by rectal palpation with whole blood from a donor seropositive to bovine leukosis virus. The inoculation consisted of the deposition of 2 ml of whole blood on a disposable obstetrical sleeve followed by a 30 second rectal palpation to simulate the process of pregnancy detection or artificial insemination. This procedure was repeated at weekly intervals for three consecutive weeks. All eight calves developed antibodies to bovine leukosis virus within five weeks after the initial palpation. The presence of the virus was demonstrated in the peripheral blood leucocytes of all eight calves at nine weeks. These results indicated that routine rectal palpation may be an effective mode of spread of bovine leukosis virus in susceptible cattle.

Strong sequence conservation among horizontally transmissible, minimally pathogenic feline leukemia viruses

We report the first complete nucleotide sequence (8,440 base pairs) of a biologically active feline leukemia virus (FeLV), designated FeLV-61E (or F6A), and the molecular cloning, biological activity, and env-long terminal repeat (LTR) sequence of another FeLV isolate, FeLV-3281 (or F3A). F6A corresponds to the non-disease-specific common-form component of the immunodeficiency disease-inducing strain of FeLV, FeLV-FAIDS, and was isolated from tissue DNA of a cat following experimental transmission of naturally occurring feline acquired immunodeficiency syndrome. F3A clones were derived from a subgroup-A-virus-producing feline tumor cell line. Both are unusual relative to other molecularly cloned FeLVs studied to date in their ability to induce viremia in weanling (8-week-old) cats and in their failure to induce acute disease. The F6A provirus is organized into 5'-LTR-gag-pol-env-LTR-3' regions; the gag and pol open reading frames are separated by an amber codon, and env is in a different reading frame. The deduced extracellular glycoproteins of F6A, F3A, and the Glasgow-1 subgroup A isolate of FeLV (M. Stewart, M. Warnock, A. Wheeler, N. Wilkie, J. Mullins, D. Onions, and J. Neil, J. Virol. 58:825-834, 1986) are 98% homologous, despite having been isolated from naturally infected cats 6 to 13 years apart and from widely different geographic locations. As a group, their envelope gene sequences differ markedly from those of the disease-associated subgroup B and acutely pathogenic subgroup C viruses. Thus, F6A and F3A correspond to members of a highly conserved family and represent prototypes of the horizontally transmitted, minimally pathogenic FeLV present in all naturally occurring infections.

Bovine leukemia: facts and hypotheses derived from the study of an infectious cancer

Bovine leukemia virus is the etiological agent of a chronic lymphatic leukemia/lymphoma in cows, sheep, and goats. Infection without neoplastic transformation also was obtained in pigs, rhesus monkeys, chimpanzees, and rabbits, and was observed in capybaras and water buffaloes. Structurally and functionally, BLV is a relative of the human T lymphotropic viruses (HTLV-I and HTLV-II). HTLV-I induces in humans a T cell leukemia, and its type II counterpart has been found in dermatopathic lymphadenopathy, hairy T cell leukemia and prolymphocytic leukemia cases. At variance with HTLV-I, BLV has not been associated with neurological diseases of the degenerative type. BLV, HTLV-I, and HTLV-II show clearcut sequence homologies. The pathology of the BLV-induced disease, most notably, the absence of chronic viremia, a long latency period, and a lack of preferred proviral integration sites in tumors, is similar to that of adult T cell leukemia/lymphoma induced by HTLV-I. The most striking feature of the three naturally transmitted leukemia viruses is the X region located between the env gene and the LTR sequence. The X region contains several overlapping long open reading frames. One of them designated XBL-I encodes a trans-activator function capable of increasing the level of gene expression directed by BLV-LTR and most probably involved in "genetic instability" of BLV-infected cells of the B cell lineage. The genetic instability puts the cell into a context of fragility and ready to move along a number of stages towards full malignancy. Little is known about these events and their causes; we have presented some theoretical possibilities. BLV infection has a worldwide distribution. In temperate climates the virus spreads mostly via iatrogenic transfer of infected lymphocytes. In warm climates and in areas heavily populated by hematophageous insects, there are indications of insect-born propagation of the virus.

Control of bovine leukosis virus in a dairy herd by a change in dehorning

Following the demonstration that bovine leukosis virus was transmitted in calves by gouge dehorning, electrical dehorning at a younger age was implemented in a commercial Holstein herd. Subsequently, annual testing of the herd revealed a decline in the prevalence of bovine leukosis virus antibodies as older cattle dehorned by the former method were replaced by younger cattle dehorned by the latter method.

[Feline leukemia virus (FeLV) and FeLV-associated diseases in cats: a review]

Feline leukaemia virus (FeLV) usually occurs in its natural species, the domestic cat. FeLV is also important to human individuals as a comparative model, as FeLV may cause a variety of diseases which are partly malignant and partly benign, such as immunosuppression which bears a resemblance to AIDS (acquired immune deficiency syndrome) in man. Although FeLV is a common infective agent, the incidence of disease due to FeLV is much higher in cats kept in closed households in which several of them are present than it is in free-range cats. Consequently, diseases caused by FeLV are frequently diagnosed in pedigree cats which are often maintained in relatively large numbers. FeLV is transmitted among cats by contagion. The main sources of infection are persistantly infected FeLV carrier cats which continuously excrete virus from the mouth and in other secretions. The majority of cats infected with FeLV will produce neutralising antibodies. Cats which are unable to do so, will become permanently infected. The prognosis is bad in these cats: 90 per cent will die within five years. Various techniques are used to detect FeLV. The most common method, the indirect immunofluorescence (IFA) test, is performed on air-dried blood smears. The results of the IFA agree with that are almost completely identical to those of the virus isolation test. Another test is ELISA (enzyme-linked immunosorbent assay), which produces approximately 10 per cent more positive results which are probably due to circulating FeLV antigens. Dissemination of FeLV among cats may be prevented by identifying infected carrier cats and removing them from contact with non-infected cats. Removal programmes using indirect immunofluorescent antibody (IFA) tests were used successfully in the Netherlands. The proportion of FeLV-positive cats decreased from 9 per cent in 1974 to approximately 3 per cent in 1985 during such a removal programme. During the above period, the removal programme was carried out in the society of Dutch cat breeders 'Felikat', the programme being made compulsory on all members of the society. The incidence of cats positive for FeLV decreased from over 11 per cent in 1974 to less than 2 per cent within four years. None of the cats tested in this society was found to be positive for FeLV in 1984 and 1985. Besides removal programmes, other methods of control, such as vaccination, were developed to prevent the spread of FeLV. The FeLV-immunostimulating complex vaccine (FeLV-ISCOM vaccine) a subunit vaccine in which FeLV-gp70 is presented in a particular manner, seems to be promising.

In vitro viral expression as a criterion for development of control procedures for enzootic bovine leukosis

In a university beef herd of 304 cattle in which six died of lymphosarcoma between 1980 and 1984, 77% of the Angus and 26% of the Charolais cattle were determined to be infected with bovine leukemia virus (BLV). Changes in iatrogenic procedures were initiated as early control measures. In vitro viral expression (VE) was used as a criterion to identify cattle for subsequent segregation or culling. This involved determinations of percentages of BLV-associated lymphocyte profiles among thin-sectioned Ficoll-Paque-isolated blood lymphocytes that were processed into plastic after culture for 48 h. Cattle retained until completion of nutritional studies or as breeding stock were separated into two groups. The BLV-seronegative cattle, BLV-seropositive cattle with 0% VE, and BLV-seropositive cattle with 1% to 4% VE were placed in group 1. Seropositive cattle with greater than or equal to 5% VE were placed in group 2. In 1985, evaluation of in vitro VE in 108 mature BLV-seropositive cattle retained for breeding revealed 36 (33%) had no observable VE. In 1986, 58 of 108 cattle were available to be reexamined, and 21 (36%) had 0% VE in both years. The VE expression values for individual cattle were generally comparable over the 2-year period. Of 48 initial seronegative breeding stock housed in group 1 with BLV-seropositive cattle with low or no VE, 21 (44%) seroconverted during 1985 to 1986. A positive correlation of 0.585 was found between VE and age-related absolute lymphocyte number.

Relationships of bovine leukemia virus prevalence in dairy herds and density of dairy cattle to human lymphocytic leukemia

A case-control study was conducted to examine possible relationships between human acute lymphoid leukemia and exposure to dairy cattle and drinking of raw milk. Two hundred twenty-three persons with acute lymphoid leukemia, diagnosed during the years 1969 to 1971 and 1973 to 1980 from the 87 most rural Iowa counties, were accessed from case records at the Iowa State Health Registry for participation in the present study. Each person and 2 matched controls were interviewed for history of residence, exposure to dairy cattle, and consumption of nonpasteurized dairy products. Two types of comparisons between affected persons and controls were done: the prevalence of bovine leukemia virus infection (as measured by serologic study) in dairy herds with which the affected persons and controls had either occupational contact or from which they had consumed raw milk and the density of dairy cattle in the townships where affected persons and controls lived. The bovine leukemia virus infection prevalence in dairy herds with which affected persons had contact was 20%, whereas the infection prevalence in the herds with which the controls had contact was 38%. The density of dairy cows in townships where affected persons resided was generally less than that in townships where controls resided. However, there was one exception; the density of dairy cows at 20 years before diagnosis was higher (589) in townships where affected adult female persons resided, compared with that in townships where controls resided (567).

The zoonotic potential of feline leukemia virus

The many studies that have addressed the possibility for FeLV infection in human beings are reviewed in this article. Because of the many similarities between FeLV-induced immune system impairment in cats and retrovirus related acquired immune deficiency syndrome in man, these two conditions are discussed as well.

Primary infection of Japanese infants with adult T-cell leukaemia-associated retrovirus (ATLV): evidence for viral transmission from mothers to children

Primary infection with adult T-cell leukemia virus (ATLV) was investigated by follow-up studies on 16 ATLV-seropositive mothers and their breastfed infants in an ATLV-endemic area of Japan. Maternal antibody to ATLV decreased in all the infants, and was detectable in only three of 12 infants tested 6 months after birth. Reappearance of the antibody 9-18 months after birth was observed in only four of the 16 infants. The ATLV-bearing cells in peripheral blood were detected in all 16 mothers after delivery. None of the 16 infants showed ATLV-bearing cells in peripheral or cord blood sampled at birth, or 1, 3 or 6 months after birth. However, virus-bearing cells in the blood became detectable 9-18 months after birth in 13 of the 16 infants. Maternal antibody and virus-bearing cells were never detected in a control group of seven infants of ATLV-seronegative mothers. These findings provide evidence for the high incidence of primary ATLV infection during early infancy among infants born to ATLV-seropositive mothers and suggest maternal viral transmission. Furthermore, samples of breast milk from all 12 seropositive mothers examined contained cell-associated ATLV capable of being transmitted to peripheral leucocytes of neonates. This finding suggests that one of the possible maternal transmission routes of ATLV is via breast milk.

Embryo transfer and transmission of bovine leukosis virus in a dairy herd

Transmission of bovine leukosis virus (BLV) by embryo transfer was investigated in a large commercial Holstein herd. One hundred and sixteen calves, transplanted as embryos from BLV-positive cows into BLV-negative heifers, were serologically negative, as were recipients, whereas 5 of 29 (17%) calves transplanted as embryos into BLV-positive recipients were infected with BLV, as evidenced by antibodies in the agar gel immunodiffusion test.

Noninfectivity of semen from bulls infected with bovine leukosis virus

An opportunity for study of the potential role of semen in the transmission of bovine leukosis virus (BLV) was provided when a Jersey herd was found to be BLV-seronegative. This was a closed herd; new genetic material had been introduced by artificial insemination (AI), using semen collected and processed at 7 AI centers in the United States. Of 66 donor bulls from which semen had been collected for AI use in the herd during the 5 years the herd remained seronegative, 24 were consistently BLV-seropositive and 2 became seropositive for BLV during the study. Semen collected from the BLV-seropositive bulls accounted for 1,019 semen units, representing 48.3% of the semen purchased. The maintenance of BLV seronegativity in this herd for 5 years, when semen from BLV-seropositive bulls was used for AI, provided evidence for the lack of infectivity of BLV in bovine semen.

Transmission of feline leukaemia virus in the milk of a non-viraemic cat

The possibility of the transmission of feline leukaemia virus (FeLV) from latently infected cats was studied. Five female cats with latent infections were examined for evidence of transmission of the virus to their kittens. One of the cats infected members of four consecutive litters of kittens which subsequently became persistently viraemic and transmitted the virus to other susceptible kittens by contact. Shortly after birth its kittens were apparently FeLV-free since neither viral antigen nor infectious virus was detected in their blood and no virus was found in cell cultures made from aspirates of bone marrow. The kittens became viraemic from 45 days of age onwards at a time when their passively acquired colostral FeLV neutralising antibodies were no longer detectable. Transmission of the virus occurred via the milk since both FeLV antigen and infectious virus were found in milk samples taken six weeks after kittening and the virus was transmitted to a fostered kitten. Eleven weeks after the birth of the fourth litter the cat became viraemic. The intermittent presence of FeLV antigens detected by the Leukassay F test, but not infectious virus, in the plasma of this cat over the previous months and a low level of serum neutralising antibodies distinguished it from four other latently infected queens which did not transmit infection to their kittens. These factors may indicate a risk of milk transmission and reactivation of latent virus.

Transmission of human T-cell leukemia virus (HTLV-I) by blood transfusion: demonstration of proviral DNA in recipients' blood lymphocytes

Human T-cell clones bearing antigens encoded by human T-cell leukemia/lymphoma virus (HTLV-I) were isolated from 6 patients who produced antibodies against HTLV-I after having received anti-HTLV-I-positive blood units containing cell components. On the other hand, it was not possible to isolate clonal cells carrying viral antigens from the recipients who did not produce antibodies. The clonal cell lines had the same surface markers as neoplastic cells of adult T-cell leukemia and had the HLA phenotype of the recipients themselves. Proviral DNA of HTLV-I was demonstrated in each of the clonal cell lines. The site of integration was different in each case even if the clones were derived from the same recipient. These results indicate that blood transfusion can cause persistent HTLV-I infection.

Bovine leukosis: an example of poor disease monitoring of international livestock shipments to developing countries

Over the past few years, cattle imported into a number of countries have been shown to carry antibodies against bovine leukosis virus (BLV), the cause of enzootic bovine leukosis. The disease, imported into England via shipments of Canadian dairy cattle in the late 1970s, is still a significant problem in the United Kingdom. Many countries now require a blood test for serum antibodies to BLV as a precondition of shipment from certain endemic countries. Those cattle positive for BLV are excluded from shipment. Well-documented cases of shipments of hundreds of Canadian cattle without testing for BLV has been obtained. These shipments were to the African country of Malawi where the BLV status is unknown. Also, although the United States is endemic for BLV, most of the recent live cattle exports were received by countries which did not require a blood test for BLV. Of the 44 countries that imported U.S. cattle during 1982 and 1983, only 13 required BLV antibody testing before shipment. This report concerns one disease in one species. The millions of livestock shipped yearly between the countries of the world may harbor many viruses at risk of being introduced into susceptible animal populations. While international animal health agencies are doing a credible job of providing disease surveillance to member countries, there still needs to be improvements in disease information dissemination.

Bovine leukaemia virus and enzootic bovine leukosis

Infection of bovines with bovine leukaemia virus (BLV) manifests itself in either of two ways: 30-70% of carriers develop persistent lymphocytosis (PL), with the viral genome integrated at a large number of different sites in the DNA of the affected B-lymphocytes, without causing any chromosomal abnormalities. Only 0,1-10% of carriers develop lymphoid tumours, which also consist of B-lymphocytes. In contrast to PL, however, they are of mono- or oligoclonal origin in terms of the integration site, which is characteristic for each tumour. All cells contain one or more copies of the viral genome, chromosomal aberrations are common and if deletions are present they are invariably found in the 5'-half of the virus DNA sequence. In both types of affected cells transcription is repressed in vivo, but transient virus production can be induced in vitro and detected by means of syncytia induction or haemagglutination. In vivo production of virus in some unknown cell is suggested by the presence of high antibody titres in infected animals, especially against the envelope glycoprotein gp51. This can be detected by various techniques such as immunodiffusion, radioimmune assay or ELISA. Monoclonal antibodies against gp51 have revealed 8 epitopes, 3 of which are recognized by neutralizing antibodies and one by a cytolytic antibody. The BLV genome, about 9 kb in size, have been cloned, and some of the information obtained on its molecular structure and function is discussed. It codes for at least 4 non-glycosylated and 2 glycoproteins. Of special interest is the recently discovered serological relationship between some of the non-glycosylated proteins and those of the human T-cell leukaemia virus. The functional role of BLV in leukaemogenesis is largely unknown. The presence of the viral genome seems to be necessary for the maintenance of the transformed state, but not its continuous expression nor an LTR-mediated promotion of transcription of cellular genes. No oncogene is carried by the virus. Although bovine leukosis is not of major economic importance, its eradication is desirable and feasible in countries with a relatively low incidence, by means of testing and elimination. For endemic situations vaccination would be preferable, and distinct possibilities exist for the development of gp51 based vaccines.

Natural transmission of bovine leukemia virus in dairy calves by dehorning

Gouge dehorning was evaluated as a mode of transmitting bovine leukemia virus in Holstein calves at a commercial dairy. Significantly (p less than 0.05) more calves dehorned by the gouge method developed antibodies to bovine leukemia virus, as measured by agar-gel immunodiffusion, three months after dehorning, than calves not dehorned. The field use of a blood-contaminated dehorning device resulted in transmission of bovine leukemia virus.

Transfusion-mediated spread of the human T-cell leukemia virus in chronic hemodialysis patients in a heavily endemic area, Nagasaki

The incidence of anti-adult T-cell leukemia-associated antigens (ATLA) was surveyed in 134 patients under chronic hemodialysis in the Nagasaki area, as well as 4708 blood donors resident in the same area as controls: 23 patients (17%) and 201 donors (4.3%) were positive for anti-ATLA antibody. All seropositive patients were found to have had a positive history of blood transfusions. Seroconversions were confirmed in 9 cases, all of them after initiation of transfusions. In total, 216 units of blood were transfused in 7 seroconverted patients, and this is consistent with the estimated rate of anti-ATLA antibody-positive donor blood supplied by the Red Cross Nagasaki Blood Center (5%).

Search for possible routes of vertical and horizontal transmission of adult T-cell leukemia virus

Adult T-cell leukemia virus associated antigen (ATLA) was detected in peripheral mononuclear cells from 29 of 35 anti-ATLA-positive mothers, but was not detected in cells from any of the neonates. Cells from breast milk of all of 12 anti-ATLA-positive mothers and semen from one of three anti-ATLA positive men were ATLA-positive.

Acute leukemia and pregnancy: a review of management and outcome, 1972-1982

Acute leukemia is a rare complication of pregnancy. Previous reviews that covered cases reported before the introduction of effective combination chemotherapy found fewer than 300 reported pregnancies, with a 36-69 per cent perinatal mortality and median maternal survival, from diagnosis, of less than 6 months. Advances in the fields of hematology-oncology, maternal-fetal medicine, and neonatology have resulted in a marked improvement in both perinatal survival statistics, and median maternal survival. Since 1972, there have been 14 pregnancies reported in patients cured of acute lymphocytic leukemia, with 1 early spontaneous abortion and 13 term infants. All mothers survived. There have been 47 reports of pregnancy in association with acute leukemia. In 40 pregnancies in which acute leukemia was treated, there were 5 abortions, 3 perinatal demises, 1 infant "liveborn in grave condition," and 31 surviving infants. Median maternal survival was at least 6, and possibly more than 12 months from delivery. In seven cases in which leukemia was untreated, there were one abortion, two perinatal demises, and four living infants; only one of six mothers survived beyond 6 months. Here, a case of pregnancy complicated by acute promyelocytic leukemia is presented. The mother was aggressively treated with combination chemotherapy. The fetus was closely monitored and delivered following a course of betamethasone at 34 weeks' gestation, and had no neonatal problems. The mother expired 13 months status-post bone marrow transplantation, 16 months after delivery. Cases of pregnancy complicated by acute leukemia reported in the period 1972-1982 are reviewed, and management is discussed in detail. Aggressive hematologic and obstetric management is advocated, and should result in further improvements in fetal and maternal outcome.

Factors affecting the infectivity of lymphocytes from cattle with bovine leukosis virus

Peripheral blood mononuclear cells were obtained from 13 bovine leukosis virus infected cattle and inoculated subcutaneously into 29 recipient adult steers to determine (a) the number of mononuclear cells (equivalent amount of blood) necessary to cause infection and (b) factors influencing infectivity of mononuclear cells from bovine leukosis virus-infected animals. A total of 55 inoculations were made. Inoculation of 1 X 10(4), 2 X 10(4) and 5 X 10(4) mononuclear cells caused seroconversion in 12%, 57% and 62% of steers, respectively. No infections occurred with 1 X 10(3) or 2 X 10(3) mononuclear cells. Cattle infected for longer than 24 months and those animals greater than three years of age were more likely to cause infection with 1 to 5 X 10(4) mononuclear cells than were cattle infected for less than 24 months or animals less than three years of age. Lymphocytes from cattle with persistent lymphocytosis caused more infections when 1 X 10(4) or 2 X 10(4) mononuclear cells were inoculated, than did lymphocytes from nonpersistent lymphocytosis cattle; however, both groups were equally infectious when 5 X 10(4) mononuclear cells were inoculated. No differences were found in infectivity of experimentally vs naturally exposed animals.

A retrospective study on transmission of adult T cell leukemia virus by blood transfusion: seroconversion in recipients

Possible transmission of adult T cell leukemia virus (ATLV) by blood transfusion was studied retrospectively. Of 41 recipients of whole blood or blood components containing cells from donors having antibodies to antigen that is associated with ATLV (anti-ATLA), 26 (63.4%) produced anti-ATLA. However, no anti-ATLA was detected in all 14 recipients of fresh-frozen plasma prepared from anti-ATLA-positive donors. None of 252 recipients of blood with cell components from anti-ATLA-negative donors produced anti-ATLA. The development of anti-ATLA in the recipients may correspond to antibody production after establishment of primary infection with ATLV that is associated with cells in blood from anti-ATLA-positive donors who are ATLV carriers.

Defining and measuring exposure in epidemiologic studies of potential zoonoses

Articles suggesting the zoonotic potential of certain human diseases (eg, multiple sclerosis, rheumatoid arthritis, and leukemia) periodically appear in the literature and frequently receive considerable attention in the popular press. Although various epidemiologic study designs have been utilized to test these hypotheses, defining and accurately measuring animal exposure has been a problem common to most of these studies and in some instances has limited their usefulness. The relative strengths and limitations of the definitions and measurements used most commonly by investigators evaluating potential zoonoses are discussed. In addition, several recommendations for assessing animal exposure in future studies are made.

Transmission of bovine leukaemia virus in milk

Nineteen calves born to dams free of bovine leukaemia virus (BLV) did not possess maternally derived precipitating antibody to BLV in their sera after the ingestion of colostrum. Eight of these calves remained serologically negative after being fed milk from BLV-free cows while three (27.3%) of 11 similar calves that had been fed milk from BLV-infected cows developed antibody. Forty-four of 47 calves born to BLV-infected dams acquired maternal antibody to BLV after ingesting colostrum. Two (8.7%) of the 23 calves fed milk from BLV-free cows developed antibody to BLV probably as a result of transplacental or colostrum infection whereas four (16.7%) of the 24 calves fed milk from BLV-infected cows developed antibody. It is concluded that milk transmission of BLV is responsible in part for the high rates of infection encountered in our dairy herds and that calves lacking specific maternal antibody are more susceptible to BLV infection through the ingestion of milk than are calves with maternal antibody.

Antibodies against human T-cell leukemia/lymphoma virus (HTLV) and expression of HTLV p19 antigen in relatives of a T-cell leukemia patient originating from Surinam

Serum and peripheral blood cell samples from eleven relatives of a T-cell leukemia patient with human T-cell leukemia/lymphoma virus (HTLV)-associated disease, were investigated for the presence of HTLV antibody and antigen expression. In addition to the patient, three family members were seropositive and a wide range in HTLV antibody titer was observed. The father of the patient showed the highest titer (173,000) and carried HTLV p19+ cells in his peripheral blood. Upon induction of proliferation of these cells by short-term culture in the presence of phytohemagglutinin (PHA) and 12-O-tetradecanoyl phorbol-13-acetate (TPA), an increase from 1% to 28% HTLV p19+ cells was observed confirming previous findings that HTLV p19 expression was correlated with proliferative activity of the host cells. In none of the other seronegative or seropositive relatives of the patient HTLV p19 expression was revealed when tested in freshly isolated mononuclear cells, upon short-term incubation in PHA + TPA or after prolonged culture for 2 or 3 passages in medium containing T-cell growth factor. The results from HLA typing studies did not provide any evidence for HTLV related abnormalities in haplotype expression. Our data confirmed the earlier notion of a prevalence of HTLV infection within families of patients with HTLV-associated disease. It is furthermore obvious from our results that a normal individual may possess high titer HTLV antibody and circulating HTLV p19+ cells without showing signs of disease.

A prospective investigation of bovine leukemia virus infection in young dairy cattle, using survival methods

The authors studied bovine leukemia virus infection in cattle born between July 1, 1979, and June 30, 1981, and followed up to 27 months in the University of Florida Dairy Research Unit herd, a 200-cow milking herd. Cattle were tested monthly for antibodies to the virus by agar-gel immunodiffusion with the glycoprotein-51 antigen. Of 473 live calves entering the study at birth, 54 became infected during the course of the study. Rates of detection of bovine leukemia virus infection were examined using survival methods. Plotted cumulative hazard rates revealed a nonlogarithmic survivorship function and three age-specific detection phases. These phases were 0-6 months, 7-16 months, and 17-26 months of age with estimated incidence rates of 5.25, 2.14, and 14.37 new detections per 10,000 cattle-days at risk, respectively. Significant differences were found between incidence rates of the first and second phase (p = 0.0168) and between those of the second and third phase (p less than 0.0001); corresponding relative risks were 0.41 and 6.71, respectively. The reduced incidence rate of the second phase coincided with movement of calves from a crowded calf barn to pastures. The increased incidence rate of the third phase coincided with mixing of bred heifers with bovine leukemia virus-infected dry cows. Increased incidence rates did not coincide with common-needle vaccination or artificial insemination. Evidence was not found for milk-borne infection. Age-specific detection rates were not associated with dam parity (p = 0.93), dam age (p = 0.79), breed (p = 0.60), or consumption of colostrum from cows infected with the virus (p = 0.23). However, detection rates were lower in cattle born to bovine leukemia virus-infected cows than in those born to noninfected cows (p = 0.03).