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M D Daniel

Publications and source records attributed to M D Daniel.

At least 19 recordsLinked to original sources
PubMed1992

Protective effects of a live attenuated SIV vaccine with a deletion in the nef gene.

Vaccine protection against the human immunodeficiency virus (HIV) and the related simian immunodeficiency virus (SIV) in animal models is proving to be a difficult task. The difficulty is due in large part to the persistent, unrelenting nature of HIV and SIV infection once infection is initiated. SIV with a constructed deletion in the auxiliary gene nef replicates poorly in rhesus monkeys and appears to be nonpathogenic in this normally susceptible host. Rhesus monkeys vaccinated with live SIV deleted in nef were completely protected against challenge by intravenous inoculation of live, pathogenic SIV. Deletion of nef or of multiple genetic elements from HIV may provide the means for creating a safe, effective, live attenuated vaccine to protect against acquired immunodeficiency syndrome (AIDS).

Animals↗
PubMed1992

Differences in neutralization of simian lentivirus (SIVMAC) in lymphocyte and macrophage cultures.

Comparison of neutralization of SIVmac251 in primary macrophage cultures with neutralization in lymphocytes (CEM174 cells) showed that neutralizing antibodies induced by SIV251 in infected rhesus macaques protected both macrophages and T lymphocytes against infection when the virus was preincubated with the antibodies. In macrophages, the neutralizing antibodies also protected against infection when added 1 hour after the virus. Addition of antisera to macrophages between 24 and 48 hours after virus inoculation resulted in infection with continuous release of small amounts of p24 into the supernatant fluids but these antibody-treated cultures failed to exhibit cytopathic virus replication. In contrast, the same neutralizing antisera did not protect lymphocytes against infection and subsequent cytopathic replication of the virus when added only 1 hour after virus inoculation. This distinction in the effect that neutralizing antibodies had on the development of cytopathic infection in lymphocytes and macrophages when added after virus inoculation, suggests that they could alter the dynamics of virus replication and therefore the pathogenesis of disease.

Animals↗
PubMed1992

Genetic analysis of simian virus 40 from brains and kidneys of macaque monkeys.

Simian virus 40 (SV40) was isolated from the brains of three rhesus monkeys and the kidneys of two other rhesus monkeys with simian immunodeficiency virus-induced immunodeficiency. A striking feature of these five cases was the tissue specificity of the SV40 replication. SV40 was also isolated from the kidney of a Taiwanese rock macaque with immunodeficiency probably caused by type D retrovirus infection. Multiple full-length clones were derived from all six fresh SV40 isolates, and two separate regions of their genomes were sequenced: the origin (ori)-enhancer region and the coding region for the carboxy terminus of T antigen (T-ag). None of the 23 clones analyzed had two 72-bp enhancer elements as are present in the commonly used laboratory strain 776 of SV40; 22 of these 23 clones were identical in their ori-enhancer sequences, and these had only a single 72-bp enhancer element. We found no evidence for differences in ori-enhancer sequences associated with tissue-specific SV40 replication. The T-ag coding sequence that was analyzed was identical in all clones from kidney. However, significant variation was observed in the carboxy-terminal region of T-ag in SV40 isolated from brain tissues. This sequence variation was located in a region previously reported to be responsible for SV40 host range in cultured cell lines. Thus, SV40 appears to be an opportunistic pathogen in the setting of simian immunodeficiency virus-induced immunodeficiency, similarly to JC virus in human immunodeficiency virus-infected humans, the enhancer sequence organization generally attributed to SV40 is not representative of natural SV40 isolates, and sequence variation near the carboxy terminus of T-ag may play a role in tissue-specific replication of SV40.

Amino Acid Sequence↗
PubMed1991

Importance of the nef gene for maintenance of high virus loads and for development of AIDS.

When rhesus monkeys were infected with a form of cloned SIVmac239 having a premature stop signal at the 93rd codon of nef, revertants with a coding codon at this position quickly and universally came to predominate in the infected animals. This suggests that there are strong selective forces for open functional forms of nef in vivo. Although deletion of nef sequences had no detectable effect on virus replication in cultured cells, deletion of nef sequences dramatically altered the properties of virus in infected rhesus monkeys. Our results indicate that nef is required for maintaining high virus loads during the course of persistent infection in vivo and for full pathologic potential. Thus, nef should become a target for antiviral drug development. Furthermore, the properties of virus with a deletion in nef suggest a means for making live-attenuated strains of virus for experimental vaccine testing.

Animals↗
PubMed1991

Priming with T helper cell epitope peptides enhances the antibody response to the envelope glycoprotein of HIV-1 in primates.

The induction of a memory immune response to HIV, mediated by any kind of effector mechanism, requires the induction of T cell help. In previous studies performed in different murine MHC haplotypes, three immunodominant T cell epitopes (T1, T2, and TH4.1) had been identified in the HIV envelope glycoprotein. Moreover, these peptides were proliferative T cell epitopes in humans. In this study, rhesus monkeys, Macaca mulatta, were primed with these three peptides either in combination or given separately. Half of the monkeys had a proliferative response to one or more of the priming peptide(s). Those monkeys who had a T cell proliferative response also had a high antibody response after one boost with a suboptimal dose of the native protein gp 160, whereas three of four control monkeys who had received only the native protein immunization gave no detectable antibody response, and one displayed a very weak response. For reasons that are unclear, antibodies only to the gp41 portion of gp 160 could be detected in the sera. Thus, the peptides can prime Th cells in primates for an enhanced antibody response on first exposure to the whole protein. The three peptides belong to highly conserved and nonglycosylated regions of the envelope protein. The fact that the peptides acted as immunogenic T cell proliferative and helper epitopes in nonhuman primates is very encouraging for including them in future vaccine studies in humans.

Amino Acid Sequence↗
PubMed1991

Macrophage-tropic variants of SIV are associated with specific AIDS-related lesions but are not essential for the development of AIDS.

The importance of macrophage infection for the development of acquired immune deficiency syndrome (AIDS) was investigated. Molecularly cloned simian immunodeficiency virus (SIV)mac239 replicates very poorly in cultured macrophages yet it causes AIDS in rhesus monkeys. Three of five rhesus monkeys that died with AIDS following SIVmac239 infection showed no disease manifestations directly associated with macrophage infection, such as encephalitis and granulomatous interstitial pneumonia. Simian immunodeficiency virus recovered from the peripheral blood of these three animals at or near the time of death replicated very poorly if at all in cultured macrophages, and tissues taken at autopsy showed little or no infection of macrophages by immunohistochemical staining. However two of the five rhesus monkeys that died with AIDS following SIVmac239 infection displayed a characteristic SIV-related meningoencephalitis and/or granulomatous pneumonia, lesions associated with macrophage infection. Simian immunodeficiency virus recovered from the peripheral blood of these two animals near the time of death replicated extremely well in cultured macrophages, indicating the emergency of macrophage-tropic variants in vivo. Furthermore tissues taken at autopsy from these two showed many infected macrophages by immunohistochemical staining. These results indicate that AIDS and death can occur without obvious involvement of macrophage infection. However the presence of macrophage-tropic viral strains appears to influence the disease course and disease manifestations.

Animals↗
PubMed1991

Cytokine influence on simian immunodeficiency virus replication within primary macrophages. TNF-alpha, but not GMCSF, enhances viral replication on a per-cell basis.

The control of HIV-1 or SIV replication within macrophages is probably influenced by a variety of viral and cellular factors. Of the cellular factors, the authors have studied cytokine influence on SIV replication in vitro utilizing simian alveolar macrophages and uncloned SIVmacMTV, a macrophage-tropic variant. The approach allowed quantification of viral replication on a per-cell basis. As reported for HIV-1 replication in macrophages, TNF-alpha significantly increased SIV production in these macrophage cultures. GMCSF also resulted in marked increases in SIV gag protein in culture supernatants. However, after correcting for differences in total cell numbers and numbers of gag-containing cells in the treated and untreated cultures, GMCSF did not upregulate SIV production on a per-cell basis. IL-6 increased SIV replication little if at all but induced significantly greater cytopathic changes in the treated cultures compared with infected, untreated cultures. In contrast, IFN-gamma greatly decreased replication. Our results for GMCSF, IFN-gamma, and IL-6 are in contrast to previously published reports of cytokine control of HIV-1 growth in target cells, and they stress the importance of cell number analyses and the use of primary cultures in the study of lentiviral replication kinetics in macrophages.

Animals↗
PubMed1990

Complement-mediated, infection-enhancing antibodies in plasma from vaccinated macaques before and after inoculation with live simian immunodeficiency virus.

Rhesus monkeys vaccinated against infection with simian immunodeficiency virus (SIV) were examined, in retrospect, for the presence of infection-enhancing antibodies and possible consequences associated with the presence of these antibodies. At the time of experimental inoculation with live virus, complement-mediated, infection-enhancing antibodies were detected in plasma specimens from six of six animals vaccinated with detergent-inactivated whole virus, from nine of nine animals vaccinated with Formalin-inactivated whole virus, and from seven of eight animals immunized with two SIV subunit preparations. The presence of infection-enhancing antibodies at the time of viral challenge gave no indication of predicting vaccine success or failure. After live-virus challenge, titers of infection-enhancing antibodies, like enzyme-linked immunosorbent assay titers, increased in unprotected animals and decreased or became undetectable in animals protected by vaccination. Thus, vaccine protection against SIV infection can still be achieved in the presence of detectable complement-mediated, infection-enhancing antibodies.

Animals↗
PubMed1990

Study of long-term cultures of simian immunodeficiency virus (SIVmac 251)-infected peripheral blood lymphocytes.

A culture of rhesus monkey peripheral blood lymphocytes was divided into two parts; one was kept as an uninfected control, and the other was infected with a strain of simian immunodeficiency virus (SIVmac251) originally isolated from a rhesus monkey that died of a malignant lymphoma associated with acquired immune deficiency syndrome. Both cultures were sampled at successive intervals from 1 to 40 days postinfection. Each sample was subjected to in situ hybridization for detection of viral mRNA, immunocytochemical detection of viral core protein (p27), reverse transcriptase assay, electron microscopy, and immunophenotypic characterization of infected cells. These techniques were used to define viral growth kinetics of this novel lentivirus in peripheral blood lymphocytes. The first evidence of SIVmac251 replication was obtained by an in situ hybridization signal for viral mRNA at 2 days postinoculation. This was followed by detection of viral p27 core protein by immunocytochemistry on day 4. Reverse transcriptase activity above control values was not detected until day 8. Budding particles were not found in the infected cultures until 14 days postinfection. Results of in situ hybridization, immunocytochemistry, and reverse transcriptase assay indicated that two bursts of viral replication occurred during the course of this study. The first, at 3 weeks postinfection, was due to infection and subsequent depletion of CD4+ lymphocytes, while the second, 3 weeks later, resulted from a cycle of replication in CD8+ lymphocytes and the remaining CD4+ cells, culminating in the death of all cells on day 39 postinoculation.

Animals↗
PubMed1990

Soluble and membrane-associated interleukin 2 receptor-alpha expression in rhesus monkeys infected with simian immunodeficiency virus.

More than 80% of rhesus monkeys infected with simian immunodeficiency virus (SIV) were found to have elevated levels of soluble interleukin-2 receptor (IL-2R) in their serum during the course of infection. All long-term survivors had stably elevated levels of soluble IL-2R. The highest levels of soluble IL-2R correlated with the expression of IL-2R on tissue macrophages. Although IL-2R expression was induced on alveolar macrophages by infection with SIV in vitro, expression of IL-2R on tissue macrophages in vivo was not associated with concurrent SIV protein expression in the same cells. Moreover, in animals with high soluble IL-2R levels, there was an inverse relationship between the numbers of cells expressing IL-2R and cells expressing viral protein. The results suggest that the induction of IL-2R may be an indirect or secondary effect of SIV infection. Changes in expression of macrophage-elaborated factors, such as that of IL-2R described in this report, may play a crucial role in some of the pathologic features of acquired immunodeficiency syndrome.

Animals↗
PubMed1990

Comparative biology of natural and experimental SIVmac infection in macaque monkeys: a review.

Epidemiologic and clinicopathologic data from 11 macaques with naturally acquired SIV infection--10 of which have died--were compared with those from 34 rhesus monkeys that have died of experimental SIVmac infection. Several differences, including gender affected, age at time of death, and the occurrence of certain opportunistic infections, could be explained by the experimental design; others remained unexplained. The most striking difference was the 41% incidence of meningoencephalomyelitis in the experimental group and its absence in naturally SIV-infected animals.

Age Factors↗
PubMed1990

Use of simian immunodeficiency virus for vaccine research.

Rhesus monkeys were immunized with purified, disrupted, noninfectious simian immunodeficiency virus (SIV) in adjuvant induced SIV neutralizing antibodies. Two of six previously vaccinated macaques were protected against infection when challenged with 200-1,000 animal infectious doses of uncloned, pathogenic SIV and both have remained free of signs of virus infection for 19 and 30 months. Prior vaccination appeared to be of benefit in decreasing the virus load and in delaying the onset of AIDS in animals that became infected. Nonetheless, two of four previously vaccinated monkeys that became infected following challenge eventually developed AIDS and died 505 and 538 days after infection. Thus, for a vaccine to be truly effective against AIDS, it may have to protect absolutely against initial infection.

Animals↗
PubMed1990

Nef genes of SIV.

Molecular clones of SIVmac were constructed that differed only in sequences within the nef gene. DEAE-transfection of viral DNA containing an open from of nef yielded virus that replicated with similar kinetics and to a similar extent in macaque peripheral blood lymphocyte (PBL) cultures as virus with a deletion or stop codon within nef. Rhesus monkeys that received each kind of molecularly cloned virus became infected. Our results additionally suggest that mutant forms of virus are selected in vitro while open, functional forms are selected in vivo. In animals infected with virus containing a stop codon within nef, reversion of the stop codon to a coding codon was demonstrated in five of five clones analyzed. These results indicate that nef is playing some role crucial to the virus life cycle in vivo.

Animals↗
PubMed1990

Molecular changes associated with replication of simian immunodeficiency virus in human cells.

The SIVmac239 infectious clone does not have a premature stop codon in its transmembrane protein (TMP) region and it produces full-length (41 kilodalton, kDa) TMP in macaque peripheral blood lymphocytes (PBL) in vitro and in vivo. However, viruses with truncated forms of TMP (28kDa) are selected during propagation in human cell types; truncated forms arise from point mutations, CAG (glutamine) to TAG (stop), in the viral genome. These results document molecular changes associated with adaptation of SIVmac for growth in human cells.

Animals↗
PubMed1989

Vaccine protection against simian immunodeficiency virus infection.

Rhesus monkeys were immunized by multiple inoculations with purified, disrupted, noninfectious simian immunodeficiency virus (SIV) in adjuvant. Immunized monkeys developed anti-SIV antibodies detectable by whole-virus ELISA and by immunoblot reactivity; these antibodies had weak neutralizing activity. One week after the last immunization, monkeys were challenged with 200-1000 animal infectious doses of uncloned, live SIV. The same strain of SIV that was used for vaccination was also used for challenge. Anamnestic antibody responses and SIV recovery from peripheral blood were used to evaluate infection following the live virus challenge; two of six vaccinated monkeys showed no evidence of infection following the live virus challenge. Transfusion of 10 ml of whole blood from these two into uninfected, naive rhesus monkeys did not result infection of the recipients, providing further support for the lack of infection in the two previously vaccinated animals. Four of four unvaccinated control monkeys inoculated with these doses of live SIV became infected and three of these died with AIDS 118-258 days after infection. Only one of the six vaccinated monkeys has died to date. In situ hybridization with lymph node biopsy specimens suggested that the virus load was much higher in control macaques than in vaccinated macaques. These results indicate that vaccination with inactivated whole virus can protect macaques against challenge with live SIV. Furthermore, they provide hope that vaccine protection against human AIDS virus infection may be possible.

Animals↗
PubMed1989

Prevalence of antibodies to SIV in baboons in their native habitat.

We have documented rare infection of baboons in their native habitat with simian immunodeficiency virus (SIV). Of 124 sera collected from yellow baboons in central Tanzania, two gave high readings by SIVagm ELISA (greater than 1.0) and moderate by SIVmac ELISA (0.5-1.0). These two sera gave strong reactions to the major SIVagm proteins, including gp130, by western blot analysis; their reactivity to SIVmac protein was considerably weaker. Similar testing of 155 sera from olive baboons of Ethiopia revealed no clearly positive sera. Thus, 2 of 279 baboon sera or 0.7% were positive for antibodies to SIV. The strong reactivity of the two positive yellow baboon sera with SIVagm proteins raises questions about whether these animals may have been infected by green monkeys in their native habitat; baboons occasionally prey upon and eat green monkeys. In addition to these two clearly positive samples, one olive baboon serum and one yellow baboon serum reacted only with major gag protein (p24-p26). Continued study of prevalence and diversity of SIV in primates will be important for understanding the history and evolution of primate lentiviruses and, it is hoped, the origins of viruses that cause AIDS in humans.

Animals↗