Comparison of cardiac output measured by oesophageal Doppler ultrasonography or pulse pressure contour wave analysis

BACKGROUND

Maintaining adequate organ perfusion during high-risk surgery requires continuous monitoring of cardiac output to optimise haemodynamics. Oesophageal Doppler Cardiac Output monitoring (DCO) is commonly used in this context, but has some limitations. Recently, the cardiac output estimated by pulse pressure analysis- (PPCO) was developed. This study evaluated the agreement of cardiac output variations estimated with 9 non-commercial algorithms of PPCO compared with those obtained with DCO.

METHODS

High-risk patients undergoing neurosurgery were monitored with invasive blood pressure and DCO. For each patient, 9 PPCO algorithms and DCO were recorded before and at the peak effect for every haemodynamic challenge.

RESULTS

Sixty-two subjects were enrolled; 284 events were recorded, including 134 volume expansions and 150 vasopressor boluses. Among the 9 algorithms tested, the Liljestrand-Zander model led to the smallest bias (0.03 litre min(-1) [-1.31, +1.38] (0.21 litre min(-1) [-1.13; 1.54] after volume expansion and -0.13 litre min(-1) [-1.41, 1.15] after vasopressor use). The corresponding percentage of the concordance was 91% (86% after volume expansion and 94% after vasopressor use). The other algorithms, especially those using the Winkessel concept and the area under the pressure wave, were profoundly affected by the vasopressor.

CONCLUSIONS

Among the 9 PPCO algorithms examined, the Liljestrand-Zander model demonstrated the least bias and best limits of agreement, especially after vasopressor use. Using this particular algorithm in association with DCO calibration could represent a valuable option for continuous cardiac output monitoring of high risk patients.

CLINICAL TRIAL REGISTRATION

Comité d'éthique de la Société de Réanimation de Langue Française No. 11-356.

Tobacco rattle virus mediates gene silencing in a plant parasitic root-knot nematode

Root-knot nematodes (RKNs) are sedentary biotrophic parasites that induce the differentiation of root cells into feeding cells that provide the nematodes with the nutrients necessary for their development. The development of new control methods against RKNs relies greatly on the functional analysis of genes that are crucial for the development of the pathogen or the success of parasitism. In the absence of genetic transformation, RNA interference (RNAi) allows for phenotype analysis of nematode development and nematode establishment in its host after sequence-specific knock-down of the targeted genes. Strategies used to induce RNAi in RKNs are so far restricted to small-scale analyses. In the search for a new RNAi strategy amenable to large-scale screenings the possibility of using RNA viruses to produce the RNAi triggers in plants was tested. Tobacco rattle virus (TRV) was tested as a means to introduce double-stranded RNA (dsRNA) triggers into the feeding cells and to mediate RKN gene silencing. It was demonstrated that virus-inoculated plants can produce dsRNA and siRNA silencing triggers for delivery to the feeding nematodes. Interestingly, the knock-down of the targeted genes was observed in the progeny of the feeding nematodes, suggesting that continuous ingestion of dsRNA triggers could be used for the functional analysis of genes involved in early development. However, the heterogeneity in RNAi efficiency between TRV-inoculated plants appears as a limitation to the use of TRV-mediated silencing for the high-throughput functional analysis of the targeted nematode genes.

Transcriptome analysis of root-knot nematode functions induced in the early stages of parasitism

Root-knot nematodes of the genus Meloidogyne are obligate biotrophic parasites able to infest > 2000 plant species. The nematode effectors responsible for disease development are involved in the adaptation of the parasite to its host environment and host response modulation. Here, the differences between the transcriptomes of preparasitic exophytic second-stage juveniles (J2) and parasitic endophytic third-stage juveniles (J3) of Meloidogyne incognita were investigated. Genes up-regulated at the endophytic stage were isolated by suppression subtractive hybridization and validated by dot blots and real-time quantitative polymerase chain reaction (PCR). Up-regulation was demonstrated for genes involved in detoxification and protein degradation, for a gene encoding a putative secreted protein and for genes of unknown function. Transcripts of the glutathione S-transferase gene Mi-gsts-1 were 27 times more abundant in J3 than in J2. The observed Mi-gsts-1 expression in the oesophageal secretory glands and the results of functional analyses based on RNA interference suggest that glutathione S-transferases are secreted during parasitism and are required for completion of the nematode life cycle in its host. Secreted glutathione S-transferases may protect the parasite against reactive oxygen species or modulate the plant responses triggered by pathogen attack.

A novel gamma 2-herpesvirus of the Rhadinovirus 2 lineage in chimpanzees

Old World monkeys and, recently, African great apes have been shown, by serology and polymerase chain reaction (PCR), to harbor different gamma2-herpesviruses closely related to Kaposi's sarcoma-associated Herpesvirus (KSHV). Although the presence of two distinct lineages of KSHV-like rhadinoviruses, RV1 and RV2, has been revealed in Old World primates (including African green monkeys, macaques, and, recently, mandrills), viruses belonging to the RV2 genogroup have not yet been identified from great apes. Indeed, the three yet known gamma2-herpesviruses in chimpanzees (PanRHV1a/PtRV1, PanRHV1b) and gorillas (GorRHV1) belong to the RV1 group. To investigate the putative existence of a new RV2 Rhadinovirus in chimpanzees and gorillas we have used the degenerate consensus primer PCR strategy for the Herpesviral DNA polymerase gene on 40 wild-caught animals. This study led to the discovery, in common chimpanzees, of a novel gamma2-herpesvirus belonging to the RV2 genogroup, termed Pan Rhadino-herpesvirus 2 (PanRHV2). Use of specific primers and internal oligonucleotide probes demonstrated the presence of this novel gamma2-herpesvirus in three wild-caught animals. Comparison of a 1092-bp fragment of the DNA polymerase obtained from these three animals of the Pan troglodytes troglodytes subspecies, one from Gabon and the two others from Cameroon, revealed <1% of nucleotide divergence. The geographic colocalization as well as the phylogenetic "relationship" of the human and simian gamma2-herpesviruses support the model according to which herpesviruses have diversified from a common ancestor in a manner mediating cospeciation of herpesviruses with their host species. By demonstrating the existence of two distinct Rhadinovirus lineages in common chimpanzees, our finding indicates the possible existence of a novel human gamma2-herpesvirus belonging to the RV2 genogroup.

Molecular and phylogenetic analyses of 16 novel simian T cell leukemia virus type 1 from Africa: close relationship of STLV-1 from Allenopithecus nigroviridis to HTLV-1 subtype B strains

A serological survey searching for antibodies reacting with human T-cell leukemia virus type 1 (HTLV-1) antigens was performed on a series of 263 sera/plasma obtained from 34 monkey species or subspecies, originating from different parts of Africa. Among them, 34 samples exhibited a typical HTLV-1 Western blot pattern. Polymerase chain reaction was performed with three primer sets specific either to HTLV-1/STLV-1 or HTLV-2 and encompassing gag, pol, and tax sequences, on genomic DNA from peripheral blood mononuclear cells of 31 animals. The presence of HTLV-1/simian T-cell leukemia virus type 1 (STLV-1) related viruses was determined in the 21 HTLV-1 seropositive animals tested but not in the 10 HTLV-1 seronegative individuals. Proviral DNA sequences from the complete LTR (750 bp) and a portion of the env gene (522 bp) were determined for 16 new STLV-1 strains; some of them originating from species for which no STLV-1 molecular data were available as Allenopithecus nigroviridis and Cercopithecus nictitans. Comparative and phylogenetic analyses revealed that these 16 new sequences belong to five different molecular groups. The A. nigroviridis STLV-1 strains exhibited a very strong nucleotide similarity with HTLV-1 of the subtype B. Furthermore, four novel STLV-1, found in Cercocebus torquatus, C. m. mona, C. nictitans, and Chlorocebus aethipos, were identical to each other and to a previously described Papio anubis STLV-1 strain (PAN 503) originating from the same primate center in Cameroon. Our data extend the range of the African primates who could be permissive and/or harbor naturally STLV-1 and provide new evidences of cross-transmission of African STLV-1 between different monkey species living in the same environment and also of STLV-1 transmissions from some monkeys to humans in Central Africa.

[Allelic polymorphism of Plasmodium falciparum MSP-2 gene in blood samples from Gabonese children]

In this study we have undertaken the molecular analysis of the MSP-2 gene of R falciparum isolates collected from schoolchildren living in the village of Dienga (Gabon). Using conventional microscopy and the polymerase chain reaction, 61% of these children harboured parasites without any symptom of malaria (asymptomatic status). Children with a malaria episode were those with an axillary temperature > or = 37.5 degrees C and a parasitaemia > or =800 parasites/microl of blood. Comparisons of the allelic diversity and distribution of MSP-2 gene were carried out according to the clinical status at the time of sampling. Polymorphism of the MSP-2 gene was large in both clinical groups, both asymptomatic and symptomatic (11 identified alleles). The allele FC27/560bp (base pairs) was found significantly in clinical isolates. Prevalence of the 3D7 family was 68% and 44% in asymptomatic infections and clinical infections, respectively. Multiple P. falciparum genotypes were more predominant in clinical cases (2.96 clones/child with a malaria attack vs 2.01 clones/child with asymptomatic infections). We observed also a reduction of the complexity of infection beyond the age of 10 years. These results are discussed in regard to studies conducted in other areas in Africa.

The relationship between parasitological status and humoral responses to Loa loa antigens in the Mandrillus sphinx model after immunization with irradiated L3 and infection with normal L3

In order to identify antigens associated with protection and those associated with active infection, the humoral immune response of 6 Mandrillus sphinx immunized with 150 irradiated L3 and challenged with 100 normal L3 of Loa loa or 6 animals infected with 100 L3 were compared. The plasma of these animals was analysed by Western blot using adult, Mf and L3 antigens. Several antigens with molecular weights varying from 120 kDa to 13 kDa were recognized by the plasma of all animals. It was shown that early recognition of microfilarial antigens with molecular weights of 97, 68, 45 and 33 kDa correlated with the amicrofilaraemic state. A total of 83% of animals with circulating microfilariae had antibodies against the microfilariae 21 kDa antigen. Furthermore, the antibodies against the 21 kDa appeared 1 month before detection of microfilariae in the peripheral blood of 80% of these animals, and declined when animals became amicrofilaraemic. In contrast, when L3 antigen was used, a molecule with a relative molecular weight of 20 kDa was recognized by antibodies of the only animal which remained amicrofilaraemic for 1 year after immunization with irradiated L3. These results suggest that the microfilarial molecule of 21 kDa may be useful as a marker of Loa loa patent infection, whereas the 97, 68, 45 and 33 kDa molecules of microfilariae and the L3 molecule of 20 kDa may be associated with resistance against Loa loa.

Organization of the X and Y chromosomes in human, chimpanzee and mouse pachytene nuclei using molecular cytogenetics and three-dimensional confocal analyses

We used multicolour fluorescence in-situ hybridization on air-dried pachytene nuclei to analyse the structural and functional domains of the sex vesicle (SV) in human, chimpanzee and mouse. The same technology associated with 3-dimensional analysis was then performed on human and mouse pachytene nuclei from cytospin preparations and tissue cryosections. The human and the chimpanzee SVs were very similar, with a consistently small size and a high degree of condensation. The mouse SV was most often seen to be large and poorly condensed, although it did undergo progressive condensation during pachynema. These results suggest that the condensation of the sex chromosomes is not a prerequisite for the formation of the mouse SV, and that a different specific mechanism could be responsible for its formation. We also found that the X and Y chromosomes are organized into two separate and non-entangled chromatin domains in the SV of the three species. In each species, telomeres of the X and Y chromosomes remain clustered in a small area of the SV, even those without a pseudoautosomal region. The possible mechanisms involved in the organization of the sex chromosomes and in SV formation are discussed.

Comparative analysis of natural killer cell activity, lymphoproliferation and lymphocyte surface antigen expression in nonhuman primates housed at the CIRMF Primate Center, Gabon

Six different species of nonhuman primates housed at the CIRMF Primate Center, cynomolgus monkeys (Macaca fascicularis), rhesus monkeys (Macaca mulatta), mandrills (Mandrillus sphinx), vervets (Cercopithecus aethiops pygerythrus), chimpanzees (Pan troglodyte) and baboons (Papio hamadryas), were evaluated for their natural killer cell activity and for the ability of their peripheral blood mononuclear cells to proliferate in response to known mitogens (concanavalin A, phytohemagglutinin and staphylococcal enterotoxin A) and to react with a panel of mouse monoclonal antibodies directed against human leukocyte surface antigens. Basic information on normal immune functions in these primates is important because of their use as experimental animal models for the study of human diseases such as acquired immunodeficiency syndrome (AIDS), hepatitis, loiasis and malaria.

Simian homologues of human gamma-2 and betaherpesviruses in mandrill and drill monkeys

Recent serological and molecular surveys of different primate species allowed the characterization of several Kaposi's sarcoma-associated herpesvirus (KSHV) homologues in macaques, African green monkeys, chimpanzees, and gorillas. Identification of these new primate rhadinoviruses revealed the existence of two distinct genogroups, called RV1 and RV2. Using a degenerate consensus primer PCR method for the herpesvirus DNA polymerase gene, the presence of KSHV homologues has been investigated in two semi-free-ranging colonies of eight drill (Mandrillus leucophaeus), five mandrill (Mandrillus sphinx), and two hybrid (Mandrillus leucophaeus-Mandrillus sphinx) monkeys, living in Cameroon and Gabon, Central Africa. This search revealed the existence of not only two distinct KSHV homologues, each one belonging to one of the two rhadinovirus genogroups, but also of two new betaherpesvirus sequences, one being close to cytomegaloviruses and the other being related to human herpesviruses 6 and 7 (HHV-6 and -7). The latter viruses are the first simian HHV-6 and -7 homologues identified to date. These data show that mandrill and drill monkeys are the hosts of at least four novel distinct herpesviruses. Moreover, mandrills, like macaques and African green monkeys, harbor also two distinct gamma-2 herpesviruses, thus strongly suggesting that a second gamma-2 herpesvirus, belonging to the RV2 genogroup, may exist in humans.

Protection against Plasmodium falciparum malaria in chimpanzees by immunization with the conserved pre-erythrocytic liver-stage antigen 3

In humans, sterile immunity against malaria can be consistently induced through exposure to the bites of thousands of irradiated infected mosquitoes. The same level of protection has yet to be achieved using subunit vaccines. Recent studies have indicated an essential function for intrahepatic parasites, the stage after the mosquito bite, and thus for antigens expressed during this stage. We report here the identification of liver-stage antigen 3, which is expressed both in the mosquito and liver-stage parasites. This Plasmodium falciparum 200-kilodalton protein is highly conserved, and showed promising antigenic and immunogenic properties. In chimpanzees (Pan troglodytes), the primates most closely related to humans and that share a similar susceptibility to P. falciparum liver-stage infection, immunization with LSA-3 induced protection against successive heterologous challenges with large numbers of P. falciparum sporozoites.

[Evaluation of a simple and rapid method of Plasmodium falciparum DNA extraction using thick blood smears from Gabonese patients]

In field-based studies, sometimes it is difficult to collect and store samples. We have evaluated a method of malaria parasite deoxyribonucleic (DNA) extraction from non-stained thick dried blood smears collected from 108 Gabonese patients. This method of DNA isolation was compared to those using phenol/chloroform. Patients parasitemia ranged from 0 to 240,000 parasites/microliter of blood. Both methods of DNA preparation gave similar results. Of the 108 slides, 57% were Plasmodium falciparum positive after PCR analysis of the MSA-2 gene and 34% were positive by microscopical examination. Thirty-six and seventy-two blood smears from patients were also tested after one and four weeks' storage respectively, at room temperature, and the parasite DNA was successfully extracted. We conclude that this simple method of collection and rapid procedure of parasite DNA isolation are adequate and convenient in the field when a large number of samples are required and in the case of repetitive samplings of patients.

Pharmacokinetics, metabolism and excretion of megazol in a Trypanosoma brucei gambiense primate model of human African trypanosomiasis. Preliminary study

The pharmacokinetics of megazol (2-amino-5-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazol, CAS 19622-55-0) was investigated after a 100 mg/kg oral administration to six primates infected with Trypanosoma brucei gambiense. The plasma levels of megazol were between 0.2 microgram/ml and 46 micrograms/ml 24 h after dosing in all animals. In animals with prolonged infection, megazol absorption was accelerated (Tmax was 4 h compared with 8 h, for day 53 and day 39 post inoculation) but the amount absorbed was not modified. The megazol concentrations in the cerebrospinal fluid represented between 5.5% and 10.6% of the plasma levels at the same times. Unchanged megazol was eliminated predominantly via the kidneys: 46-96% of the ingested dose was recovered in the urine, compared with 0-5% in the faeces. Furthermore, this urinary elimination of megazol was altered in animals with prolonged infections. In the urine, 4 unknown metabolites were observed, unchanged megazol was characterized by LC-MS/MS. This study indicates that megazol crosses the blood-brain barrier after oral administration. Prolonged infections affect the absorption of megazol and its urinary elimination.

Corticotropin-releasing hormone in chimpanzee and gorilla pregnancies

In humans, the length of gestation and the onset of parturition have been linked to the exponential production of placental CRH and a late gestational decline in maternal plasma CRH-binding protein (CRH-BP). CRH has been shown to have direct effects on the myometrium and on the fetal adrenal, where it stimulates production of the estrogen precursor dihydroepiandrosterone sulfate. In vitro placental CRH production is stimulated by cortisol and inhibited by progesterone. To determine whether this mechanism might operate in other apes, we sampled eight chimpanzees and two gorillas through their pregnancies for CRH, CRH-BP, cortisol, estradiol, progesterone, and alpha-fetoprotein. We show that both chimpanzee and gorilla maternal plasma CRH concentrations rise exponentially as observed in the human. The gorillas exhibited a human-like antepartum fall in CRH-BP, whereas CRH-BP in the chimpanzee remained stable. Pregnancy-associated changes in cortisol, estradiol, progesterone, and alpha-fetoprotein were qualitatively similar to those observed in humans. Maternal plasma cortisol correlated with plasma CRH in both gorillas (r = 0.60; P < 0.05) and chimpanzees (r = 0.36; P < 0.02). Further, there was a strong correlation between plasma estradiol and the log of plasma CRH in the gorilla (r = 0.93; P < 0.0001) and in the chimpanzee (r = 0.72; P < 0.001), which is consistent with the hypothesis that placental CRH determines the placental production of estradiol by stimulating the production of fetal adrenal dehydroepiandrosterone sulfate. Plasma CRH and progesterone were positively correlated providing no in vivo support for progesterone inhibition of CRH release.

Leptospirosis and Ebola virus infection in five gold-panning villages in northeastern Gabon

An exhaustive epidemiologic and serologic survey was carried out in five gold-panning villages situated in northeastern Gabon to estimate the degree of exposure of to leptospirosis and Ebola virus. The seroprevalence was 15.7% for leptospirosis and 10.2% for Ebola virus. Sixty years after the last seroepidemiologic survey of leptospirosis in Gabon, this study demonstrates the persistence of this infection among the endemic population and the need to consider it as a potential cause of hemorrhagic fever in Gabon. There was no significant statistical correlation between the serologic status of populations exposed to both infectious agents, indicating the lack of common risk factors for these diseases.

Plasmodium coatneyi: differential clinical and immune responses of two populations of Macaca fascicularis from different origins

Two species of macaques, including two Macaca fascicularis from the Philippines, two M. fascicularis from Mauritius, and one Macaca mulatta, were experimentally infected with blood stages of Plasmodium coatneyi and followed during their clinical, parasitological, biological, and immunological evolution. Plasma cytokine (TNF-alpha, IL-1beta, IL-6, IFN-gamma) production peaked for all monkeys 11 days after inoculation, concomitantly with peaks of parasitemia. Only the M. fascicularis from the Philippines survived the infection. The main features, which discriminated nonfatal from fatal cases, were the observation in M. fascicularis from the Philippines of a mean CD4+/CD8+ ratio below I and of their ability, as revealed by mitogenic stimulation of whole blood, to produce increasing amounts of IFN-gamma as infection evolved. The contribution of environmental and genetic factors, which may differentiate the three groups of monkeys and therefore explain fatal or nonfatal evolution of the infection among them, is discussed.

Simian T-cell lymphotropic virus type 1 from Mandrillus sphinx as a simian counterpart of human T-cell lymphotropic virus type 1 subtype D

A recent serological and molecular survey of a semifree-ranging colony of mandrills (Mandrillus sphinx) living in Gabon, central Africa, indicated that 6 of 102 animals, all males, were infected with simian T-cell lymphotropic virus type 1 (STLV-1). These animals naturally live in the same forest area as do human inhabitants (mostly Pygmies) who are infected by the recently described human T-cell lymphotropic virus type 1 (HTLV-1) subtype D. We therefore investigated whether these mandrills were infected with an STLV-1 related to HTLV-1 subtype D. Nucleotide and/or amino acid sequence analyses of complete or partial long terminal repeat (LTR), env, and rex regions showed that HTLV-1 subtype D-specific mutations were found in three of four STLV-1-infected mandrills, while the remaining monkey was infected by a different STLV-1 subtype. Phylogenetic studies conducted on the LTR as well as on the env gp21 region showed that these three new STLV-1 strains from mandrills fall in the same monophyletic clade, supported by high bootstrap values, as do the sequences of HTLV-1 subtype D. These data show, for the first time, the presence of the same subtype of primate T-cell lymphotropic virus type 1 in humans and wild-caught monkeys originating from the same geographical area. This strongly supports the hypothesis that mandrills are the natural reservoir of HTLV-1 subtype D, although the possibility that another monkey species living in the same area could be the original reservoir of both human and mandrill viruses cannot be excluded. Due to the quasi-identity of both human and monkey viruses, interspecies transmission episodes leading to such a clade may have occurred recently.

The atrophic variant of dermatofibrosarcoma protuberans in childhood: a report of six cases

Dermatofibrosarcoma protuberans (DFSP) is typically diagnosed during early adult life at a tumoral stage. It occurs only rarely in children. We report six childhood cases of DFSP which presented initially with the misleading clinical appearance of atrophic plaques, and we review over 140 cases of DFSP in childhood. As compared with adult forms, DFSP in children does not show distinctive features except for a tendency for acral localization. The diagnosis is difficult because of the slow course of the lesions, which present initially as apparently benign atrophic morphoeaor keloid-like plaques. We believe that DFSP in childhood is probably under-estimated, as a significant proportion of patients diagnosed as young adults had an onset several years earlier. Better knowledge of the initial appearance is important for making an early diagnosis and for an easier surgical treatment.

Phylogenetic analysis of SIV and STLV type I in mandrills (Mandrillus sphinx): indications that intracolony transmissions are predominantly the result of male-to-male aggressive contacts

Natural SIVmnd and STLVmnd infections of mandrills in a colony at the Centre International de Recherches Médicales de Franceville (CIRMF) in Gabon were investigated by genetic analysis to determine the extent of intracolony transmission. SIVmnd pol sequence analysis indicates that the six strains present in the colony belong to the SIVmnd lentivirus subgroup previously defined according to the only available prototype sequence (SIVmndGB1), which originated from the same colony. The intraanimal nucleotide diversity (1.1-3.1%) was similar in range to that reported in individuals infected by other HIV/SIVs. The interanimal diversity (0.5-4.3%) was not significantly different from that observed in each individual mandrill, indicating an epidemiological link among the SIVmnd isolates of distinct animals within the colony. Phylogenetic analysis of these isolates, together with seroepidemiological and behavior surveillance within the colony, indicates a predominant male-to-male transmission of SIVmnd that probably occurred during bouts of interanimal aggression. Moreover, our results suggest one case of vertical transmission of SIVmnd from a naturally infected founder female to one of her six offspring. The first genetic analysis of STLV isolates from mandrills is also reported here. Partial tax/rex sequences were used to evaluate the diversity between seven STLVmnd isolates and their phylogenetic relationships with other known strains of human and nonhuman primate T cell leukemia virus, types I and II (PTLV-I/II). They all belong to the PTLV-I subtype, but two genetically distinct STLVmnd groups were evidenced within the mandrill colony. The phylogenetic analyses of the STLVmnd isolates, together with seroepidemiological and behavior surveillance of the mandrills, indicate that intracolony transmissions of STLVmnd are also predominantly the result of male-to-male aggressive contacts.

Natural infection of a household pet red-capped mangabey (Cercocebus torquatus torquatus) with a new simian immunodeficiency virus

A seroprevalence survey was conducted for simian immunodeficiency virus (SIV) antibody in household pet monkeys in Gabon. Twenty-nine monkeys representing seven species were analyzed. By using human immunodeficiency virus type 2 (HIV-2)/SIVsm, SIVmnd, and SIVagm antigens, one red-capped mangabey (RCM) (Cercocebus torquatus torquatus) was identified as harboring SIV-cross-reactive antibodies. A virus isolate, termed SIVrcm, was subsequently established from this seropositive RCM by cocultivation of its peripheral blood mononuclear cells (PBMC) with PBMC from seronegative humans or RCMs. SIVrcm was also isolated by cocultivation of CD8-depleted RCM PBMC with Molt 4 clone 8 cells but not with CEMx174 cells. The lack of growth in CEMx174 cells distinguished this new SIV from all previously reported sooty mangabey-derived viruses (SIVsm), which grow well in this cell line. SIVrcm was also successfully transmitted (cell free) to human and rhesus PBMC as well as to Molt 4 clone 8 cells. To determine the evolutionary origins of this newly identified virus, subgenomic pol (475 bp) and gag (954 bp) gene fragments were amplified from infected cell culture DNA and sequenced. The position of SIVrcm relative to those of members of the other primate lentivirus lineages was then examined in evolutionary trees constructed from deduced protein sequences. This analysis revealed significantly discordant phylogenetic positions of SIVrcm in the two genomic regions. In trees derived from partial gag sequences, SIVrcm clustered independently from all other HIV and SIV strains, consistent with a new primate lentivirus lineage. However, in trees derived from pol sequences, SIVrcm grouped with the HIV-1/SIVcpz lineage. These findings suggest that the SIVrcm genome is mosaic and possibly is the result of a recombination event involving divergent lentiviruses in the distant past. Further analysis of this and other SIVrcm isolates may shed new light on the origin of HIV-1.

Characterization and titration of an HIV type 1 subtype E chimpanzee challenge stock

A subtype E human immunodeficiency virus type 1 (HIV-1) isolate from the Central African Republic (E/90CR402) was adapted to growth on chimpanzee peripheral blood mononuclear cells (PBMCs) by cocultivation of irradiated, infected human PBMCs with chimpanzee PBMCs. The resulting virus was passaged in chimpanzee PBMCs to generate a stock of chimpanzee-adapted virus. Although its V3 region sequence was identical to that of the parental isolate, the chimpanzee-adapted virus had a syncytium-inducing phenotype as opposed to the non-syncytium-inducing phenotype of the parental virus. After demonstrating in one animal each that the passaged virus could infect chimpanzees following intravenous (i.v.) or cervical inoculation, the i.v. infectious titer of the stock was determined. Exposure of three chimpanzees to different doses of the virus indicated that the titer was between 2 and 5 TCID50. Thus, the HIV-1 E/90CR402 chimpanzee challenge stock established persistent infections in chimpanzees by both the i.v. and genital routes and should be valuable for future HIV-1 vaccine studies to evaluate cross-protection between HIV-1 subtypes.

Occurrence and frequency of transmission of naturally occurring simian retroviral infections (SIV, STLV, and SRV) at the CIRMF Primate Center, Gabon

Among the primates held at the CIRMF Primate Center, Gabon, no serological sign of SIV infection could be demonstrated in 68 cynomolgus monkeys, 60 chimpanzees, nine gorillas, and 12 sun-tailed monkeys, while seven of 102 mandrills and six of 24 vervets were infected with SIV. Six mandrills, seven vervets and ten cynomolgus monkeys exhibited a full HTLV type 1 Western blot profile. The sera of two gorillas and one chimpanzee presented with a positive but not typical HTLV Western blot profile. The sera of the gorillas lacked p24 antibodies, and the chimpanzee had a Western blot profile evocative of HTLV-II. All attempts to amplify viruses from these animals by PCR were unsuccessful. Two other chimpanzees and seven gorillas presented with indeterminate HTLV Western blot profiles. In the mandrill colony, only male animals were STLV seropositive and no sexual transmission to females was observed. SIV infection was also more frequent in male than female mandrills and sexual transmission appeared to be a rare event. No SRV infection was observed in macaques.