Dynamics of perinatal bovine leukemia virus infection.

BACKGROUND: Bovine leukemia virus (BLV) is highly endemic in many countries, including Argentina. As prevention of the spread from infected animals is of primary importance in breaking the cycle of BLV transmission, it is important to know the pathophysiology of BLV infection in young animals, as they are the main source of animal movement. In this work, we determined the proviral load and antibody titers of infected newborn calves from birth to first parturition (36 months). RESULTS: All calves under study were born to infected dams with high proviral load (PVL) in blood and high antibody titers and detectable provirus in the colostrum. The PVL for five out of seven calves was low at birth. All animals reached PVLs of more than 1% infected peripheral blood mononuclear cells (PBMCs), three at 3 months, one at 6 months, and one at 12 months. High PVLs persisted until the end of the study, and, in two animals, exceeded one BLV copy per cell. Two other calves maintained a high PVL from birth until the end of the study. Antibody titers were 32 or higher in the first sample from six out of seven calves. These decayed at 3-6 months to 16 or lower, and then increased again after this point. CONCLUSIONS: Calves infected during the first week of life could play an active role in early propagation of BLV to susceptible animals, since their PVL raised up during the first 12 months and persist as high for years. Early elimination could help to prevent transmission to young susceptible animals and to their own offspring. To our knowledge, this is the first study of the kinetics of BLV proviral load and antibody titers in newborn infected calves.

Natural progression of Bovine Leukemia Virus infection in Argentinean dairy cattle.

We describe the progression of Bovine Leukemia Virus (BLV) infection from birth until the first lactation in 61 animals from a typical large dairy herd of Argentina, with more than 85% of prevalence. The purpose was to identify potential points to effectively break the BLV cycle of transmission in our dairy productive system. We detected early infection in 11.47% of newborn calves by nested PCR. From birth to 12 months, no evidence of new infections was observed. After 12 months of age, the detection of new reactors increased slowly with time, from 15.09% at 15 months to 24% at 27 months. After that, the number of reactors increased rapidly up to 40% and 60.76% at 30 and 36 months, respectively. This last 9-month period coincided with parturition and the entry into the milking herd. Real-time PCR showed that more than 75% of adult animals had low peripheral-blood proviral load. Complementary, all infected animals showed low levels of provirus in milk and colostrum. The most important finding was that even when management procedures to prevent BLV iatrogenic transmission were followed, no significant change was observed in the prevalence after three years, strongly suggesting that other way/s of transmission play a key role under natural conditions. This study showed an interesting baseline to draw an alternative approach based on selective segregation according to the peripheral-blood proviral load as a potential indicator of risk transmission, and as an alternative to classical control measures.

Cyclophosphamide adjuvant arthritis in Trypanosoma cruzi infected rats with inflammatory cytokine effects.

OBJECTIVE: To analyze whether the cyclophosphamide (CYC) induced reestablishment of adjuvant arthritis (AA) in chronically Trypanosoma cruzi infected rats correlates with changes in the secretion of pro- and antiinflammatory cytokines by popliteal lymph node cells. METHODS: Inbred "l" rats infected with T. cruzi 90 days earlier and age matched controls were given CYC (25 mg/kg body weight) or physiologic saline 48 h before arthritis induction. Popliteal lymph node cells were collected at the time of AA induction (48 h after CYC treatment) or during the peak response, to study the concanavalin-A (ConA) or Mycobacterium tuberculosis-driven in vitro proliferation of several cytokines in their culture supernatants. Results. Infected rats given CYC were recovered from the otherwise decreased ConA induced proliferation seen at the time of peak AA. The CYC mediated reestablishment of AA in T. cruzi infected rats coexisted with an increased presence of tumor necrosis factor-a in supernatants from either antigen or ConA stimulated cultures as well as interleukin 12 (IL-12) in the latter case. CYC also lowered to normal the increased IL-10 levels from ConA stimulated cultures that the T. cruzi group displayed at the time of inducing AA. Conclusion. The process by which CYC restores the clinical expression of AA affects the balance between cytokines that influence the regulation of arthritis in favor of the inflammatory component.