Antigenic stimulation of T lymphocytes in chronic nononcogenic retrovirus infection: equine infectious anemia

Efficacy of inactivated whole-virus and subunit vaccines in preventing infection and disease caused by equine infectious anemia virus

We report here on a series of vaccine trials to evaluate the effectiveness of an inactivated equine infectious anemia virus (EIAV) whole-virus vaccine and of a subunit vaccine enriched in EIAV envelope glycoproteins. The inactivated vaccine protected 14 of 15 immunized ponies from infection after challenge with at least 10(5) 50% tissue culture-infective doses of the homologous prototype strain of EIAV. In contrast, it failed to prevent infection in any of 15 immunized ponies that were challenged with the heterologous PV strain. Levels of PV virus replication and the development of disease, however, were significantly reduced in 12 of the 15 ponies so challenged. The subunit vaccine prevented infection from homologous challenge in four of four ponies tested but failed to prevent infection in all four challenged with the PV strain. Two of the four subunit vaccinates had more severe symptoms of equine infectious anemia than nonimmunized ponies infected in parallel. Both vaccines stimulated EIAV-specific cell-mediated immunity. The in vitro lymphoproliferative response was shown to be mediated by T lymphocytes and appeared to be indistinguishable from that induced by EIAV infection. Significant differences were observed in the in vivo lymphocyte responses following challenge with the two virus strains. While peripheral blood mononuclear cells from the inactivated virus vaccinates were equally stimulated by both the prototype and PV strains, the subunit vaccinates challenged with PV exhibited lower levels of spontaneous proliferation and serine esterase activity. This diminished cellular response to PV was correlated with more severe clinical disease in the same ponies. These studies demonstrate for the first time that both an EIAV inactivated whole-virus vaccine and a viral envelope glycoprotein-based subunit vaccine can provide protection against rigorous challenge levels of homologous virus but are unable to protect against similar challenge levels of a heterologous virus. Moreover, the data demonstrate that protection can be achieved in the absence of detectable levels of virus-specific neutralizing antibody in the vaccine recipients at the time of virus challenge. While vaccine-induced virus-specific cell-mediated immune responses were detected, their role in conferring protection was not obvious. Nevertheless, protection from disease appeared to be correlated with the induction of high levels of serine esterase activity following challenge. A significant observation is that while the whole-virus vaccine was usually capable of preventing or markedly moderating disease in the PV-infected ponies, the subunit vaccine appeared to have a high potential to enhance the disease induced by PV infection.(ABSTRACT TRUNCATED AT 400 WORDS)

T and B lymphocytes in horses persistently infected with equine infectious anaemia virus

The percentage of T and B lymphocytes in the peripheral blood of horses chronically infected with equine infectious anaemia (EIA) virus was determined and the results were compared with the percentage of these cells in healthy uninfected horses. Cells with membrane receptors for sheep erythrocytes (T and active T lymphocytes) were determined by E and A rosette techniques, while cells with receptors for the C3b component of complement and those with receptors for mouse erythrocytes (B lymphocytes), were determined by the EAC rosette method. The percentage of Fe positive cells was assayed by the EA rosette test. The majority of peripheral blood lymphocytes (PBL) from both uninfected and EIA-infected horses formed rosettes of each kind with only three erythrocytes indicating a low density of the corresponding receptors on the cell membrane under the condition of the assays used. The percentage of T lymphocytes in the peripheral blood of diseased horses (52.4 +/- 1.6%), as detected by E rosettes, was significantly (p less than 0.01) higher than in control animals (42.4 +/- 3.5%). In clinically healthy horses 8.9 +/- 1.1% of PBL were identified by A rosettes as active T cells, whereas animals with a chronic form of EIA had a much lower (p less than 0.001) percentage of these cells (4.7 +/- 0.7%). In the B lymphocyte subpopulations the percentages of cells bearing Fc and C3b receptors were markedly elevated (p less than 0.001) in EIA-infected horses (24.7 +/- 0.8% and 42.8 +/- 2.2% respectively) as compared to uninfected animals (15.1 +/- 1.4% and 29.6 +/- 1.2% respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

T lymphocyte development in horses. I. Characterization of monoclonal antibodies identifying three stages of T lymphocyte differentiation

Six monoclonal antibodies reacting with equine T lymphocytes at different stages of maturation were selected from antibodies produced against lymphoid cell preparations. EqT12 and EqT13 antibodies identified subsets of cortical thymocytes with high terminal deoxynucleotidyltransferase (TdT) activity and no phytolectin responsiveness. EqT12+ thymocytes were scattered throughout the cortex while EqT13+ thymocytes were located in the subcapsular cortex. EqT12 bound to small numbers of bone marrow cells, splenocytes, and circulating lymphoid cells, but not to mature T lymphocytes. EqT13 bound to very small numbers of bone marrow cells but not to more mature lymphocytes. EqT6 and EqT7 reacted with a large population of cortical thymocytes with high TdT activity and no phytolectin responsiveness. EqT2 and EqT3 bound primarily to medullary thymocytes with low TdT activity. Eq2+ thymocytes responded to phytolectin stimulation while EqT3+ thymocytes did not. EqT2 and EqT3 bound to 33% and 91% of circulating T lymphocytes, respectively. The T lymphocytes bound by both antibodies included cells capable of suppressing a mixed lymphocyte reaction. Thus, EqT12 and EqT13 identify cells with the functional characteristics of prothymocytes. EqT6 and EqT7 identify resident cortical thymocytes, and EqT2 and EqT3 identify a subpopulation of mature T lymphocytes and all mature T lymphocytes, respectively.

Pronounced production of polyclonal immunoglobulin G1 in the synovial fluid of goats with caprine arthritis-encephalitis virus infection

Infection of goats with caprine arthritis-encephalitis virus, a lentivirus, resulted in arthritis characterized by the production of intrasynovial immunoglobulin G1 concentrations that were 2 to 5.3 times the serum concentrations in the inoculated carpi at 6 months postinoculation. The intrasynovial immunoglobulin was polyclonal, and its presence was accompanied by increased albumin leakage into the joints. Synovial fluid immunoglobulin levels fluctuated temporally but remained elevated compared with medium-inoculated controls for 38 months after infection. Elevated immunoglobulin G1 concentrations correlated with focal sublumenal plasmacytic infiltrates in the synovia of inoculated carpi at 5 months postinoculation. Inflammation in the uninoculated joints of infected goats was also accompanied by increased intrasynovial immunoglobulin G1 levels. Antibody to systemically administered antigens was a greater proportion of the immunoglobulin population in sera than in synovial fluids of infected goats, suggesting that antibody production to local antigens was responsible for increased intrasynovial immunoglobulin G1 levels.