Neutralizing antibody responses and evolution of antigenic variants in monozygotic twin lambs infected with phenotypically distinct ovine lentiviruses.

Ovine lentivirus (OvLV) isolates 85/34 (OvLV 34) and 84/28 (OvLV 28) were initially characterized as phenotypically distinct "rapid/high" and "slow/low" strains based on replication kinetics, syncytiogenesis, and cell lysis in vitro. In the present study, sera from OvLV-34- or OvLV-28-infected monozygotic twin lambs defined these virus strains as distinct neutralization serotypes. We also show that immune recognition of at least one OvLV neutralization epitope is influenced by genetic differences between lambs. Additional studies determined the neutralization phenotype of virus isolates from alveolar macrophages of OvLV-34- or OvLV-28-infected lambs, evaluated the role of neutralizing antibodies in selection and persistence of antigenic variants, and related the severity of OvLV-induced lymphoid interstitial pneumonia (LIP) to the evolution of neutralization variants. These studies demonstrate that (i) macrophage-associated OvLV neutralization variants can arise in the presence or the absence of neutralizing antibodies directed to inoculum viruses, (ii) OvLV variants persist in macrophages in the presence of serum neutralizing antibodies, and (iii) the emergence of OvLV variants is apparently unrelated to the severity of LIP.     

Analysis of antibody responses to phenotypically distinct lentiviruses.

To define the immune responses against phenotypically and pathogenically distinct lentiviruses, we used an immunoblotting assay to study antibodies to viral proteins of ovine lentivirus (OvLV) in 16 experimentally and 12 naturally infected sheep. Two distinct phenotypes of OvLV were used to experimentally infect lambs: strain 85/34, a "rapid/high" isolate which rapidly induced lysis in infected primary macrophage cultures and replicated to relatively high titers, and strains 84/28 and 85/14, "slow/low" isolates which induced slowly progressive syncytia with minimal lysis in vitro and replicated only to low titers in the same cell type. Serum antibodies against four major viral structural proteins, gp105, p25, p16, and p14, were detected. In a longitudinal study of experimentally infected lambs, the antibody to p25 (major gag protein) usually appeared first (average, about 3 weeks postinoculation [p.i.]) and was followed in about 2 weeks by p16, p14, and gp105 almost simultaneously. Six of 16 animals did not develop anti-p14 antibody by the time of necropsy at 9 to 29 weeks p.i. Two of 10 lambs which developed antibody to p14 had the antibody only transiently from 3 to 8 or 13 weeks p.i. and lost it by the time of necropsy at 21 or 22 weeks p.i. In contrast, antibodies to the other three structural proteins remained fairly constant until the time of necropsy. There were differences in the antibody responses of the experimentally infected lambs to the two phenotypes of OvLV. Seven of 10 (70%) lambs which were inoculated with the rapid/high strain developed antibody to p14, whereas only 17% of the lambs inoculated with the slow/low strains had antibody to this protein. In the longitudinal study, no decline was observed in the activity of any specific antibody such as that which occurs with anti-p24 antibody in human immunodeficiency virus infection, except in the case of anti-p14 antibody in two lambs. There were no significant differences in antibody titers against p25, p16, and p14 in final blood samples between rapid/high virus- and slow/low virus-infected groups. However, the rapid/high virus-infected group developed a fivefold-higher geometric mean titer of anti-env product (gp 105) antibody than did the slow/low virus-infected group (P 相似文献   

Ovine lentivirus lymphoid interstitial pneumonia. Rapid induction in neonatal lambs.

For examination of the characteristics of lentivirus-induced pulmonary disease in an animal model, neonatal lambs were given intratracheal injections of high-and low-passage ovine lentivirus (OvLV) isolates. In 6 of 6 lambs inoculated with low-passage OvLV or OvLV from lung lavage fluid, lesions of lymphoid interstitial pneumonia (LIP) developed. In none of 7 lambs inoculated with a high-passage OvLV or 4 control lambs inoculated with medium alone or ultrafiltered lung fluid did lung lesions develop. Systemic distribution of lentivirus was greater and development of lentivirus antibody was more rapid in lambs inoculated with low-passage OvLV, compared with lambs inoculated with high passage OvLV. The number of lymphocytes in bronchoalveolar lavage samples was increased in lambs with lymphoid interstitial pneumonia. The development of lymphoid interstitial pneumonia was markedly accelerated, in comparison with previous reports of experimentally induced lentivirus pneumonia in sheep. In lentivirus-inoculated lambs pulmonary lesions developed comparable to lymphoid interstitial pneumonia associated with the acquired immunodeficiency syndrome and other human benign lymphoid disorders of the lung. Similarities between the disease manifestations and virologic properties of OvLV and human T-cell lymphotropic virus III argue for the relevance of OvLV-induced disease as a model for human retrovirus diseases. The ability of OvLV to cause accelerated pulmonary disease in neonates may be due to age-related susceptibility factors that enhance the pathogenicity of lentiviruses.     

Lentivirus-induced lymphoproliferative disease. Comparative pathogenicity of phenotypically distinct ovine lentivirus strains.

For investigation of the pathogenicity of lentivirus strains, which have distinctly different cytopathic phenotypes in synovial membrane cell culture, plaque-purified, lytic, and nonlytic ovine lentivirus (OvLV) isolates were inoculated intratracheally into two groups of neonatal lambs. Twelve lambs were inoculated with a lytic OvLV isolate and 3 lambs each with two nonlytic OvLV isolates. Five control lambs were inoculated with either virus-free medium or were left uninoculated. In 8 of 12 lambs inoculated with a lytic OvLV isolate mild to severe lesions of lymphoid interstitial pneumonia (LIP) and pulmonary lymphoid hyperplasia developed, 6 of 12 lambs had lesions of pulmonary lymph node follicular hyperplasia, 3 of 9 female lambs had lesions of lymphoproliferative mastitis, 3 of 10 lambs had lesions of lymphocytic/plasmacytic synovitis, and 3 lambs had no lesions. In 3 of 6 lambs inoculated with nonlytic OvLV isolates only mild LIP lesions developed, without concurrent mammary gland or joint lesions. Bronchoalveolar lavage samples from OvLV-diseased lambs contained on average 1.5-fold more numbers of total leukocytes, and 4-fold more numbers of lymphocytes, compared with bronchoalveolar lavage samples of normal lambs. Monoclonal antibodies to ovine lymphocyte surface markers showed that the SBU-T8+ lymphocyte (CD 8 equivalent) was the predominant lymphocyte subset (mean of 65% of total lavaged lymphocytes) in bronchoalveolar lavage samples of 3 diseased lambs. Ovine lentivirus was reisolated from multiple tissues of both groups of OvLV-inoculated lambs, but the percentage of individual tissues infected was greater in lambs inoculated with the lytic viral isolate. Control lambs had no lesions and failed to produce OvLV-specific antibodies or yield OvLV from tissues. All OvLV-inoculated lambs produced either low or undetectable serum virus neutralizing antibodies. In contrast, lambs inoculated with either lytic or nonlytic OvLV produced precipitating antibodies to OvLV glycoprotein and group-specific protein. However, initial detection of precipitating antibodies to OvLV glycoprotein was earlier (mean, 5.8 weeks after inoculation) in OvLV-infected lambs in which severe lymphoproliferative disease developed and delayed (mean, 10.2 weeks after inoculation) in OvLV-infected lambs with mild or no lesions. Together, these results suggest that lentivirus isolates produced disease in a virus strain-dependent manner and suggest that humoral immune responses against OvLV failed to prevent lesion development in lentivirus-infected lambs.(ABSTRACT TRUNCATED AT 400 WORDS)     

Acute-phase proteins and hematologic values in ovine lentivirus-infected lambs treated with recombinant ovine IFN-tau.

To evaluate changes in complete blood cell (CBC) counts, haptoglobin and fibrinogen in ovine lentivirus (OvLV)-infected lambs treated with recombinant ovine interferon-tau (rOVIFN-tau), 24 lambs were allocated to one of four groups (n = 6 per group): (1) virus + rOvIFN-tau, VI, (2) virus + placebo, VP, (3) no virus + rOVIFN-tau, NVI, and (4) no virus + placebo, NVP. Three lambs in each group were treated once a day for 12 weeks, and the remaining 3 lambs were treated for 33 weeks. Blood was collected at days 0, 7, and 10 and at weeks 2-10, 12, 32, and 33 to determine CBC counts, as well as haptoglobin and fibrinogen levels. Hematologic values remained within normal limits in all groups. However, hemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), and packed cell volume (PCV) values decreased (p < 0.05) in the two rOvIFN-tau-treated groups (VI and NVI) compared with the placebo-treated (VP and NVP) groups. Both rOvIFN-upsilon and OvLV had a mild negative effect on neutrophil numbers. Although Hb, MCV, MCHC, PCV, and neutrophil values declined in the rOvIFN-tau-treated lambs compared with the placebo-treated lambs, these values remained within the reference range for sheep. Experimental lambs did not show adverse clinical signs associated with OvLV infection or as a result of rOvIFN-tau treatment. The lack of significant side effects of high-dose rOvIFN-tau in sheep and previous reports of broad-spectrum and cross-species antiviral activity suggest that rOvIFN-tau warrants further investigation as an antiviral therapeutic agent.     

Host-virus interaction as defined by amplification of viral DNA and serology in lentivirus-infected sheep

Summary To correlate the presence of ovine lentivirus (OvLV) as detected by polymerase chain reaction (PCR) with detection of antibody, 42 sheep from a flock with enzootic OvLV infection were studied. The results of agar gel immunodiffusion (AGID), ELISA, and immunoblotting assays were compared, and leukocytes (blood, bone marrow, lymph node, and lung cells) were assessed for viral DNA by PCR usingpol and LTR primers; amplified products were detected by specific DNA and RNA probes. Based on the number of animals that had detectable viral DNA, the specificities of AGID, ELISA, and immunoblotting were 77%, 92%, and 95 or 100% (depending on which criterion was used to interpret immunoblot results), respectively. Only in animals with OvLV-associated disease was OvLV DNA detected in leukocyte DNA prior to the amplification of virus in culture and only in this group was high titer antibody detected to the OvLV major surface (gp 105) and transmembrane (gp 55) antigens. Animals that were both antibody and PCR-negative lacked histopathologic evidence of disease. From this study there was no indication that OvLV infection without the development of antibody occurs, and detection of OvLV DNA in animals with weak or partial serological reactions likely indicates early OvLV infection rather than false-positive PCR results.     

Structural responses of pulmonary intravascular macrophages in lentivirus-infected and/or recombinant ovine interferon-τ–treated lambs

Ovine lentivirus (OvLV), a retrovirus, infects and disseminates to various tissue organs via monocytes. The differentiation of infected monocytes into macrophages is a prerequisite for viral replication, and the presence of infected macrophages in tissue organs induces chronic immunopathology such as lymphoid interstitial pneumonia. The pulmonary intravascular macrophage (PIM) is a recently identified mononuclear phagocyte in domestic animal species, including sheep. Recombinant ovine interferon-tau (roIFN-τ), a type I IFN originally named as the ovine trophoblast protein, has potent antiviral activity against OvLV and human immunodeficiency virus and prevents the development of OvLV-associated lung pathology. We investigated and compared the structural features of PIMs in OvLV-infected and/or roIFN-τ–treated 1-month-old lambs using transmission electron microscopy. The PIMs' numerical counts were performed in toluidine blue–stained sections of Epoxy-embedded lung tissues. A reduction in the number of PIMs was observed with OvLV infection and/or roIFN-τ treatment of lambs as compared to the control group (P ≤ 0.05). The majority of the PIMs in OvLV-infected and/or roIFN-τ–treated groups were devoid of their surface coat. The PIMs of OvLV-infected lambs exhibited signs of biosynthetic activation such as expanded rough endoplasmic reticulum, prominent Golgi complexes, and accumulation of secretory vesicles. A few PIMs contained OvLV-like structures. In roIFN-τ–treated OvLV-infected lambs, the lymphocytes had ruffled plasma membranes and were in intimate contact with the PIMs, as is observed during cytotoxic cell-mediated killing of target cells. Most of the PIMs in roIFN-τ–treated OvLV-infected lambs appeared smaller in size. Ovine lentivirus and roIFN-τ, individually or in combination, alter the integrity of the surface coat of PIMs and cause their disappearance from the lungs. Ovine lentivirus infection induces morphological changes that correlate with cytotoxic cell behavior between lymphocytes and PIMs in roIFN-τ–treated or placebo-treated lambs. The loss of PIMs, probably infected with OvLV, either through direct killing by roIFN-τ or indirectly by roIFN-τ–activated cytotoxic T lymphocytes may represent different aspects of therapeutic actions of this cytokine. Anat. Rec. 251:472–485, 1998. © 1998 Wiley-Liss, Inc.     

Phenotypic and ultrastructural characteristics of bronchoalveolar lavage cells of lentivirus-infected lambs treated with recombinant ovine IFN-tau.

Ovine lentivirus (OvLV) belongs to the family Retroviridae and closely resembles the human immunodeficiency virus (HIV). Pulmonary lesions in OvLV-infected sheep consist of lymphoid interstitial pneumonia (LIP) and lymphocytic alveolitis. Similar pulmonary lesions occur in up to 40% of HIV-infected children and in some adults with AIDS. Interferon-tau (IFN-tau), a type I IFN, is produced by trophectoderm of ruminant conceptuses and is the pregnancy recognition signal in these species. To evaluate changes in phenotypes of bronchoalveolar lavage (BAL) cells of OvLV-infected lambs treated with recombinant ovine IFN-tau (rOvIFN-tau), 24 lambs were randomly allocated to one of four groups (n = 6 per group): 1, no virus + placebo (NVP); 2, no virus + rOvIFN-tau (NVI); 3, virus + placebo (VP); 4, virus + rOvIFN-tau (VI). The BAL cells from 3 lambs in each group were labeled with monoclonal antibodies (mAb) to cell surface markers at 16 weeks of treatment, and cells from the remaining 3 lambs in each group were labeled with mAb at 34 weeks of treatment. After labeling, BAL cells were analyzed by flow cytometry. The morphology of BAL cells from all experimental lambs was examined by transmission electron microscopy (TEM). At week 16, no differences in the relative proportions of BAL cell phenotypes were detected among the experimental groups. At week 34, VI lambs had higher proportions of CD8(+), gammadelta(+), MHC class II(+), and L-selectin (LS(+)) BAL cells compared with VP lambs. Higher proportions of CD14(+) and CD44(+) cells were found in VP lambs compared with NVP lambs at 34 weeks. OvLV-like particles were detected only in bronchoalveolar macrophages of VP lambs. In this study, rOvIFN-tau increased the proportions of primary antiviral gammadelta(+) and CD8(+) immune cells in OvLV-infected lambs. This may represent a cellular mechanism to explain the antiviral and therapeutic efficacy of this cytokine, in addition to its direct antiviral effect. However, because the actual number of cells labeled with mAb CD8 was low and some subsets of gammadelta cells may coexpress the CD8 marker, further studies are necessary to better define the role of rOvIFN-tau in the modulation of these cells in vivo.     

Differences in antibody responses of mice to intranasal or intraperitoneal immunization with influenza A virus and vaccination with subunit influenza vaccine

Two antigenically related but different influenza A virus strains of H3N2 subtype, A/Dunedin/ 4/73 (H3N2) (Dunedin) and A/Mississippi/1/85 (H3N2) (Mississippi), were used for intranasal (i.n.) and intraperitoneal (i.p.) immunization of mice and respective antibody responses were compared. In ELISA, using purified influenza A virus as antigen, the highest titer of antiviral antibodies was observed after a repeated i.n. infection, in which the Dunedin strain was followed by the Mississippi strain and vice versa. Similarly, in virus neutralization (VN) test, the highest titer of VN antibodies was found after a repeated i.n. infection. The subunit vaccine INFLUVAC, when administered intramuscularly (i.m.), induced only a poor antibody response as assayed by ELISA. Moreover, the INFLUVAC vaccination elicited a 100-fold lower titer of VN antibodies than the i.n. infection and an approx a 10-fold lower titer than the i.p. immunization. A repeated INFLUVAC vaccination did not lead to a significant increase of VN antibody titer. Also the antibody response to HA2gp--a conserved part of influenza hemagglutinin (HA) that might contribute to the induction of specific antiviral antibodies--was followed. Similarly to the VN antibody response, the highest HA2 antibody titer was induced after a repeated i.n. infection, whereas the lowest HA2 antibody titer was observed after a single or repeated INFLUVAC vaccination. Overall, the HA2 antibody titers remarkably well corresponded to the VN potential of the examined sera.     

Evidence of proviral clearance following postpartum transmission of an ovine lentivirus

Lentiviral transmission by transfer of infected colostrum and/or milk is considered to be highly efficient. In this study, postpartum transmission of ovine progressive pneumonia virus (OPPV) from 10 naturally infected ewes to their 23 lambs was followed from the perinatal period throughout a four-year period. The lambs were allowed to suckle from their dam from birth through 32 weeks of age. Virus was tracked by virus isolation, quantitative PCR (qPCR), and anti-OPPV antibody responses as measured by cELISA. Cell-associated OPPV was isolated from colostrum/milk cells in 7 out of 10 ewes and provirus envelope (env) loads ranged 8 to 10(5) copies/mug DNA in colostrum/milk cells from the 10 ewes using qPCR. Provirus env loads were also detected in the peripheral circulation of 21 lambs at 8 weeks and two lambs at 22 weeks. The qPCR product at 8 weeks was confirmed as the transmembrane (tm) gene of OPPV by cloning and sequencing. Both cELISA titers ranging from 325 to 3125 and cross-neutralizing antibody titers ranging from 6 to 162 to seven different OPPV strains were found in the colostrum of the 10 ewes. Furthermore, cELISA titers in serum from lambs remained detectable through 32 weeks following the clearance of provirus at 24 weeks. After 32 weeks, both provirus and anti-OPPV antibody responses have subsequently remained undetectable through 4 years of age. These data suggest the clearance of cell-associated lentiviruses from lamb circulation after passive transfer of antibody via colostrum.     

Analysis of ovine lentivirus infectivity and replication by using a focal immunoassay and an antigen-capture enzyme-linked immunosorbent assay.

A focal immunoassay and an antigen-capture enzyme-linked immunosorbent assay (antigen-capture ELISA) were developed to quantify infectious ovine lentivirus (OvLV) and OvLV capsid protein (CA) (p27), respectively. The in vitro kinetics of replication and cytopathogenicity of distinct biological clones of OvLV (rapid/high and slow/low phenotypic variants) were assessed. Both viruses were detected by focal immunoassay within 48 h postinfection, 2 days before syncytia were observed in goat synovial membrane cells infected with rapid/high OvLV and 4 days before they appeared in cultures infected with slow/low OvLV. CA was first detected by antigen-capture ELISA in supernatants of cells infected with rapid/high OvLV 4 days postinfection, and it reached a plateau by 10 days, 4 days after peak syncytium formation. In contrast, in cultures infected at the same multiplicity of infection with slow/low OvLV, CA was detected 8 days postinfection, and the titer gradually increased over the following 12 days while the number of syncytia gradually decreased. Peripheral blood mononuclear cells (PBMC) from seropositive sheep treated with phorbol 12-myristate 13-acetate (PMA) generally expressed CA earlier and at higher levels than PBMC treated with either phytohemagglutinin or concanavalin A. Serum CA levels above 3 ng/ml were found in 58% (18 of 31) of seropositive sheep. However, there was no correlation between PMA-induced CA expression and levels of antigenemia. Viral heterogeneity may account for variations both in CA expression in cultures of PBMC and in antigenemia, humoral immune response, and viral pathogenicity in infected animals.     

Epitope analysis of capsid and matrix proteins of North American ovine lentivirus field isolates.

Monoclonal antibodies (MAbs) directed against two phenotypically distinct ovine lentivirus (OvLV) strains were generated by fusion of BALB/c SP2/0-Ag 14 myeloma cells with spleen cells from mice immunized with purified OvLV. Hybridomas were selected by indirect enzyme-linked immunosorbent assay (ELISA) and analysis of reactivity on immunoblots. The majority (17 of 21) of the MAbs recognized the gag-encoded capsid protein, CA p27, of both strains. Four other MAbs recognized a smaller structural protein, presumably a matrix protein, MA p17. Three distinct epitopes on CA p27 and one on MA p17 were distinguished by the MAbs with competition ELISA. MAbs from each epitope group were able to recognize 17 North American field isolates of OvLV and the closely related caprine arthritis-encephalitis virus (CAEV). Analysis of the data indicated that these epitopes were highly conserved among naturally occurring isolates. A representative MAb from each epitope group of anti-CA p27 MAbs reacted with four field strains of OvLV and CAEV on immunoblots. An anti-MA p17 MAb recognized the same OvLV strains on immunoblots but failed to recognize CAEV. MAbs which recognize conserved epitopes of gag-encoded lentivirus proteins (CA p27 and MA p17) are valuable tools. These MAbs can be used to develop sensitive diagnostic assays and to study the pathogenesis of lentivirus infections in sheep and goats.     

Differential induction of tumor necrosis factor alpha in ovine pulmonary alveolar macrophages following infection with Corynebacterium pseudotuberculosis, Pasteurella haemolytica, or lentiviruses.

Soluble mediators such as tumor necrosis factor alpha (TNF-alpha) may be important in the pathogenesis of many chronic pulmonary infections. We examined the ability of Corynebacterium pseudotuberculosis, Pasteurella haemolytica, and ovine lentiviruses (OvLV) to induce TNF-alpha secretion by pulmonary alveolar macrophages (PAM). Bronchoalveolar lavage cells, composed of greater than 90% PAM, were obtained from normal sheep. Bronchoalveolar lavage cells were cultured for 2, 24, 48, 72, or 168 h in endotoxin-free RPMI medium (with 10% autologous serum) or in medium containing one of the following additives: lipopolysaccharide, 1-micron polystyrene beads, C. pseudotuberculosis, P. haemolytica, or one of two plaque-cloned OvLV, 85/28 or 85/34. Lipopolysaccharide, C. pseudotuberculosis, and P. haemolytica induced TNF-alpha activity in PAM cultures as early as 2 h after inoculation, as assessed by a colorimetric cytotoxicity assay. This activity could be blocked by rabbit anti-recombinant bovine TNF-alpha serum. In contrast, medium alone, polystyrene beads, and productive infection by OvLV did not induce TNF-alpha activity in PAM cultures. Bacterial pathogens which infect pulmonary macrophages may elicit the secretion of TNF-alpha within the lungs and lead to the cachectic state associated with chronic pneumonia.     

Detection and transmission of 30 nm virus particles (astroviruses) in faeces of lambs with diarrhoea

Summary An outbreak of diarrhoea in lambs was investigated, and electron microscopic examination revealed small round virus-like particles in the faeces from eight of seventeen lambs. A bacteria-free filtrate of faeces from one lamb was given orally to a gnotobiotic lamb, which subsequently excreted virus in faeces. Intestinal contents were collected from this lamb and a filtrate given orally to two further gnotobiotic lambs, which subsequently developed diarrhoea and excreted virus in faeces. The mean diameter of the virus particles was 29.7 nm, and 12 per cent of them showed their surface structure arranged in the form of a six-pointed or five-pointed star. They were similar to those particles previously observed in human infant faeces which were referred to as astroviruses.The passage through gnotobiotic lambs with development of diarrhoea showed that these particles were animal viruses which were probably pathogenic for lambs.With 2 Figures     

Long-term evaluation of HIV antigen and antibodies to p24 and gp41 in patients with hemophilia. Potential clinical importance

To investigate the relation between human immunodeficiency virus (HIV) antigenemia and clinical manifestations of HIV infections, we studied 96 patients with hemophilia who were positive for HIV antibody, for a median of 34 months. Every 4 to 10 months a clinical and laboratory examination was performed and serum samples were tested for three HIV markers: HIV antigen, antibody to p24, and antibody to gp41. Twenty-two subjects (23 percent) were found to be positive for HIV antigen: 8 were positive upon entry and remained so (Group 1), and 14 became positive during the study, 4 to 26 months after HIV antibody appeared (seroconversion), 13 of whom remained positive for HIV antigen (Group 2). Most subjects positive for HIV antigen had low or undetectable titers of antibody to p24, whereas the antibody titer to gp41 remained high. In Group 2, patients with low p24 antibody titers had further decreases in their titers before or at the time HIV antigen appeared. Once present, HIV antigen persisted and tended to increase in concentration. In contrast to Group 3 (negative for HIV antigen, low anti-p24 titer) and 4 (negative for HIV antigen, high anti-p24 titer), the groups positive for HIV antigen had significantly higher incidences of acquired immunodeficiency syndrome (P = 0.05), immunodeficiency-related infections (P less than 0.001), and immune thrombocytopenia (P = 0.001), and had more severe disease as measured by the Walter Reed staging system (P less than 0.001). In this study, HIV antigen appeared to be a better predictive marker of HIV-related complications than the absolute T4+ count. These results suggest that HIV antigenemia indicates a poor clinical prognosis.     

Cytokine pattern is solely influenced by priming vaccine but immunity and disease by both priming and boosting vaccines in mice challenged with respiratory syncytial virus

Vaccine formulation can influence cytokine and disease patterns in mice following respiratory syncytial virus (RSV) challenge. The influence of different live and killed dual-vaccine combinations on subsequent immune responses was investigated. BALB/c mice received either killed followed by killed (KV/KV), killed followed by live (KV/LV), live followed by killed (LV/KV), or live followed by live (LV/LV) RSV vaccines intramuscularly. Mouse weight loss, viral replication, cytokine expression patterns, immunoglobulin isotype antibody profiles, neutralizing antibody responses, and cytotoxicity T lymphocyte (CTL) activities in lungs were compared on subsequent live RSV challenge. On challenge, mice vaccinated initially with KV and boosted with either KV or LV expressed significantly skewed ratios of IL-4 to IFN-gamma mRNA and IgG1 to IgG2a antibody, when compared to those vaccinated initially with LV. Low levels of RSV replication were detected in lungs of mice vaccinated with KV/KV, KV/LV, and LV/KV, but not in mice vaccinated with LV/LV. Mice vaccinated with KV/LV, LV/KV, or LV/LV had RSV-specific CTL activity in lungs six days after RSV challenge, while no CTL activity was detected in KV/KV-vaccinated mice. Mice vaccinated with KV/KV had the greatest weight loss, while LV/LV-vaccinated mice resulted in the least. Mice vaccinated with either KV/LV or LV/KV had intermediate weight loss after challenge. These data indicate that an original antigenic sin-like phenomenon was exhibited in cytokine and immunoglobulin isotype responses in mice after challenge. T helper (Th)-like immune responses were determined solely by the initial vaccination, while weight loss, viral replication, neutralizing antibody responses, and CTL activities were also influenced by boosted vaccinations.     

Maternal immunoglobulins and parainfluenza 3 virus inhibitors in the nasal and lachrymal secretions and serum of newborn lambs.

Concentrations of IgG, IgM and IgA were measured in the serum, nasal secretions and lachrymal secretions of suckled newborn lambs. The major immunoglobulin constituent of precolostral serum was IgM. Maternal immunoglobulins, of which IgG was predominant, reached peak values on day 1 of life and then declined over the next 3 weeks. Half lives were calculated as: IgG, 13-7 days; IgM, 4-1 days; and IgA 1-8 days. No immunoglobulin was detectable in nasal or lachrymal secretions prior to sucking but IgG was present in all samples of these secretions obtained approximately 24 hr after first sucking. IgG was present in nasal washings from suckled lambs, reared either naturally or on immunoglobulin-free milk substitute and levels declined as the lambs grew older. IgM and IgA did not appear consistently in the secretions until lambs were 2-3 weeks old. It was concluded, therefore, that colostral IgG reaches the nasal and lachrymal secretions of the newborn lamb. However, because the ewes in this experiment had only low serum titres, no maternal antibody to parainfluenza 3 virus (PI3) was detected in the nasal secretions of the lambs, although non-specific inhibitors were present. It is suggested, however, that low levels of maternal antibody in the secretions may play a valuable role in preventing respiratory virus infections of young ruminants before active local production of IgA and IgM begins at 2 to 3 weeks of age.