Biomedical subjects

R Hofmann-Lehmann

Publications and source records attributed to R Hofmann-Lehmann.

45 records · Page 3Linked to original sources

PubMed1996

[Quantification of proviral FIV DNA using competitive PCR].

Quantification of provirus copies is important in the context of different biological questions. The most reliable approach for DNA quantification is a PCR based on coamplification of two templates of similar length, the target sequence and the reference template, sharing the same primer recognition sequences. During the amplification, the two templates compete for the same primer set (competitive PCR, or cPCR) AND consequently amplify at the same rate independently of the number of cycles. The amplified products can be distingushed by their different lengths. After densitometrical analysis, the proviral copy number of experimentally feline immunodeficiency virus infected cats could be calculated, since a known amount of reference template was used. The method described here proved to be very sensitive (10 copies for the competitor-DNA) and was used to quantitate the proviral load during several experiments in which the influence of periodical immunestimulations and the effect of vaccines on the virus load was studied.

Animals↗

PubMed1996

[Liberation into the wild of wild felines--danger of the release of virus infections].

There are several felidae amongst the numerous endangered species. Means of aiding survival are the reintroduction to the wild of animals bred under the auspices of man and their relocation from densely populated to thinly populated areas. It is unlikely that the dangers of such reintroduction or relocation projects have been examined sufficiently in respect to the risks of virus infections confronting individuals kept in zoos or similar situations. This report presents three examples to illustrate that accidental virus infections may be expected to occur when relocating and reintroducing wild cats. The first example is the reintroduction of captive snow leopards. Zoo bred snow leopards may be infected with FIV, a virus infection that is highly unlikely to occur in the original himalayan highlands of Tibet and China. A second example is of several cases of FIP that occurred in European wild cats bred in groups in captivity. The third example mentioned is the relocation of lions from East Africa where all the commonly known feline viruses are wide-spread to the Etosha National Park. In the latter, virus infections such as FIV, FCV and FPV do not occur. The indiscriminate relocation and reintroduction of the wild cats mentioned here harbours a potential of undesirable consequences.

Animals↗

PubMed1995

FIV vaccine studies. I. Immune response to recombinant FIV env gene products and outcome after challenge infection.

We have vaccinated five groups of cats (n = 25) four times with five preparations of recombinant feline immunodeficiency virus (FIV) env gene products; one group (n = 7) served as control. The vaccine formulations were as follows: (1) envelope glycoprotein of FIV Zurich 2 (FIV Z2) expressed in a Baculovirus system and isolated by gel electroelution (denatured form); (2) insect cells expressing FIV Z2 glycoprotein; (3) envelope glycoprotein of a Boston strain (FIV Bangston) expressed in insect cells and isolated by gel electroelution (denatured form); (4) glycosylated Bangston envelope protein made in insect cells and isolated in a native form; (5) non-glycosylated Bangston envelope protein made in Escherichia coli. All cats were challenged with 20 50% cat infective doses (CID50) of FIV Z2 previously titrated in cats. All vaccinated cats developed high enzyme-linked immunosorbent assay (ELISA) antibodies to the homologous antigen; crossreactivity to heterologous antigens was seen at a lower level. Virus neutralizing antibodies (tested with Petaluma virus) reached titers up to 32. After challenge, all cats seroconverted (as judged by anti gag antibodies in Western blot) and became infected (as judged by virus isolation and/or polymerase chain reaction) between 4 and 11 weeks with the exception of one cat. It is concluded that it is relatively easy to induce high ELISA antibody titers using recombinant env gene products, ELISA antibody titers do not correlate with virus neutralization or with protection.

Animals↗

PubMed1995

FIV vaccine studies. II. Clinical findings, hematological changes and kinetics of blood lymphocyte subsets.

Five groups of cats were vaccinated with different recombinant feline immunodeficiency virus (FIV) SU vaccines expressed either in Escherichia coli or in the Baculovirus system. In Part I of this series, we described the humoral immune response and outcome of intraperitoneal FIV challenge exposure. Additionally, all cats were monitored for clinical and hematological changes and the course of blood lymphocyte subsets. These results are described in this present paper. A great increase of antibodies was found after vaccination with different recombinant FIV antigens, which did not protect the cats from intraperitoneal FIV challenge infection. This observation was paralleled by an increase of eosinophils during vaccination which was even more pronounced after challenge infection. After FIV challenge, infection lymphadenopathy, gingivitis, pharyngitis, changes in total leukocytes and neutrophils and a decrease in the CD4+:CD8+ ratio were found in cats of all groups and were considered as a sign of the FIV infection taking place, independent of vaccination. The following observations suggest that in these cats a TH2-like immune response was elicited: the high counts of eosinophils, the nature of antigen and adjuvant (aluminium hydroxide) and the high amounts of antigens used for immunization. Clearly, this type of immune response did not protect the animals from intraperitoneal FIV challenge infection.

Animals↗

PubMed1995

Recombinant FeLV vaccine: long-term protection and effect on course and outcome of FIV infection.

The efficacy and the long-term protection of a recombinant feline leukemia virus (FeLV) vaccine were determined in 30 specified pathogen free cats for over 3 years. At the same time, in order to specify the effects of feline immunodeficiency virus (FIV) on the immune system, one half of the cats (n = 15) were previously infected with the Swiss isolate FIV Zurich 2. The second half of the animals (n = 15) served as non-infected controls. Eighteen (nine FIV-negative, nine FIV-positive) vaccinated and 12 (six FIV-negative, six FIV-positive) non-vaccinated cats were intraperitoneally challenged with FeLV A. Seventeen of 18 vaccinated cats were protected against persistent viremia, while ten of 12 non-vaccinated controls became infected. An increase of antibodies against FeLV SU was found in all protected cats after the challenge exposure. No difference in vaccine efficacy was found between FIV-negative and FIV-positive animals. The whole group of cats was observed for over 3 years. There were no further vaccinations during this period. CD4+ and CD8+ cell subsets, clinical outcome and time of survival of the cats were recorded. FIV-negative and FIV-positive animals were kept in two different rooms. However, FeLV-negative and FeLV viremic cats were housed together in both rooms in order to imitate a natural FeLV exposure situation. Anti-recombinant FeLV SU antibodies were measured by enzyme-linked immunosorbent assay. Although a continuous decline of antibodies was found in FeLV vaccinated cats, they remained protected against constant FeLV challenge for over 3 years. FIV infection had a stronger effect on the depression of the CD4+:CD8+ ratio than FeLV infection. Within the group of FIV-positive cats, the FeLV-vaccinated animals had significantly better survival rates as well as better clinical and laboratory parameters. FIV- and FeLV-coinfected cats showed the lowest CD4+:CD8+ ratio, mainly caused by decreased CD4+ lymphocyte counts. CD8+ lymphocytes with strong fluorescence (CD8(high)) disappeared and cells with weak fluorescence (CD8(low)) appeared instead. Prevention of coinfection by immunizing FIV-positive cats against FeLV infection improved the clinical outcome and prolonged the cat's life expectancy.

Animals↗

PubMed1995

Circulating immune complexes and analysis of renal immune deposits in feline immunodeficiency virus-infected cats.

Total immunoglobulin content and concentration of immune complexes (IC) were determined in the sera of 51 cats infected with feline immunodeficiency virus (FIV) and of 40 controls. IgG and IgM were quantified by radial immunodiffusion and circulating IC (CIC) by the CIC-conglutinin assay. IgG fractions were obtained by acid elution from kidney tissues of 15 FIV-infected and five negative control cats to investigate the possible role of IC in the genesis of renal damage observed in infected animals. Mean concentrations of IgG and circulating IC were higher in FIV-infected cats than in controls (29.6 +/- 6.7 versus 23.0 +/- 1.9 mg/dl (mean +/- s.d.) P < 0.001; and 66.5 +/- 17.0 versus 27.4 +/- 19.9% I, P < 0.001, respectively), while IgM levels were only slightly increased (0.9 +/- 0.05 versus 0.87 +/- 0.04 mg/dl, P < 0.02). Immunoglobulin fractions were eluted from 10 of the 15 renal tissue samples from FIV-infected cats and were found to be polyclonal and at least partly specific for FIV antigens. These findings confirm the presence of a B cell activation in FIV-infected cats and demonstrate the presence of high levels of CIC in their sera. The presence of immune deposits in renal tissues suggests that IC might play a role in the pathogenesis of the renal damage observed in FIV-infected cats.

AIDS-Associated Nephropathy↗

PubMed1994

[Vaccination of cats against infection with feline leukemia virus (FeLV): first recombinant vaccine and the effect of a pre-existing infection with feline immunodeficiency virus (FIV)].

A new recombinant FeLV vaccine was evaluated in 30 specified pathogen-free cats 10 months of age cats. The vaccine consisted of the non-glycosylated FeLV envelope protein p45, aluminium hydroxide and a saponin adjuvant. The cats (n = 18) were vaccinated twice intramuscularly, 3 weeks apart. All animals were challenged intraperitoneally with FeLV subgroup A, 18 weeks later. While 94% of the vaccinated cats showed no viraemia or were only transiently viraemic, 80% of the non-vaccinated animals became persistently viraemic within 2 to 3 weeks. In our hands the preventable fraction of the vaccine was 93%. In order to determine the effect of a pre-existing infection with feline immunodeficiency virus on the efficacy of vaccination, 50% of the cats were previously infected with FIV. The infected cats were protected to the same degree as the non-infected animals. With prolonged duration of FIV infection the probability increases, that the immune system of the cat will fail and clinical signs will appear. In order to observe a state of possible immunodeficiency, an accurate clinical examination of every cat prior to vaccination seems of major importance.

Animals↗

PubMedDate not supplied

Clinical, serologic, and parasitologic follow-up after long-term allopurinol therapy of dogs naturally infected with Leishmania infantum.

Canine leishmaniasis usually is treated with antimony compounds, but frequent relapses, adverse effects, high costs, and development of resistance to long-term antimonial therapy emphasize the importance of searching for alternative antileishmanial drugs. Allopurinol was used at a dosage of 10 mg/kg/day PO to treat 10 dogs naturally infected with Leishmania infantum for a period of 2-24 months. Nine dogs recovered within 2-6 months of chemotherapy, and no relapses were observed during the treatment of up to 20 months. However, 3 of 4 dogs relapsed after treatment was discontinued. These dogs again recovered clinically when therapy was resumed. Parasite-specific immunoglobulin concentrations (IgG2) were high in all dogs before therapy and remained high even in clinically cured dogs during or after therapy. On the other hand, specific IgG1 reactions, which have been shown to be detectable in symptomatic animals, persisted in 7 dogs for long periods after clinical recovery. Three of these dogs relapsed within 2-4 weeks after interrupting therapy. However, 1 dog with no detectable specific IgG1 reaction at the end of therapy did not relapse in the following 4 months. Parasites could be detected in 8 of 9 dogs after clinical improvement by in vitro cultivation or polymerase chain reaction (PCR) testing of lymph node aspirates. In 4 of these dogs, parasites also were detected in blood samples by PCR. Hence, these clinically cured dogs must be regarded as reservoirs of Leishmania and allopurinol cannot be recommended in endemic areas.

Allopurinol↗

PubMedDate not supplied

1999: a time to re-evaluate AIDS vaccine strategies.

The field of AIDS vaccine development is in flux. Important new findings were reported in 1999 that led to a rethinking of AIDS vaccine strategies. We have been given the challenging task of providing an overview. Rather than attempting to provide a comprehensive summary, we will restrict our discussion to a few major topics, and we ask for understanding if we can only highlight.

AIDS Vaccines↗