Baboon Virus Research Articles

Isolation of Diverse Simian Arteriviruses Causing Hemorrhagic Disease.

Genetically diverse simian arteriviruses (simarteriviruses) naturally infect geographically and phylogenetically diverse monkeys, and cross-species transmission and emergence are of considerable concern. Characterization of most simarteriviruses beyond sequence analysis has not been possible because the viruses fail to propagate in the laboratory. We attempted to isolate 4 simarteriviruses, Kibale red colobus virus 1, Pebjah virus, simian hemorrhagic fever virus, and Southwest baboon virus 1, by inoculating an immortalized grivet cell line (known to replicate simian hemorrhagic fever virus), primary macaque cells, macrophages derived from macaque induced pluripotent stem cells, and mice engrafted with macaque CD34+-enriched hematopoietic stem cells. The combined effort resulted in successful virus isolation; however, no single approach was successful for all 4 simarteriviruses. We describe several approaches that might be used to isolate additional simarteriviruses for phenotypic characterization. Our results will expedite laboratory studies of simarteriviruses to elucidate virus-host interactions, assess zoonotic risk, and develop medical countermeasures.

Subclinical Infection of Macaques and Baboons with A Baboon Simarterivirus.

Simarteriviruses (Arteriviridae: Simarterivirinae) are commonly found at high titers in the blood of African monkeys but do not cause overt disease in these hosts. In contrast, simarteriviruses cause severe disease in Asian macaques upon accidental or experimental transmission. Here, we sought to better understand the host-dependent drivers of simarterivirus pathogenesis by infecting olive baboons (n = 4) and rhesus monkeys (n = 4) with the simarterivirus Southwest baboon virus 1 (SWBV-1). Surprisingly, none of the animals in our study showed signs of disease following SWBV-1 inoculation. Three animals (two rhesus monkeys and one olive baboon) became infected and sustained high levels of SWBV-1 viremia for the duration of the study. The course of SWBV-1 infection was highly predictable: plasma viremia peaked between 1 × 107 and 1 × 108 vRNA copies/mL at 3–10 days post-inoculation, which was followed by a relative nadir and then establishment of a stable set-point between 1 × 106 and 1 × 107 vRNA copies/mL for the remainder of the study (56 days). We characterized cellular and antibody responses to SWBV-1 infection in these animals, demonstrating that macaques and baboons mount similar responses to SWBV-1 infection, yet these responses are ineffective at clearing SWBV-1 infection. SWBV-1 sequencing revealed the accumulation of non-synonymous mutations in a region of the genome that corresponds to an immunodominant epitope in the simarterivirus major envelope glycoprotein GP5, which likely contribute to viral persistence by enabling escape from host antibodies.

Cellular Immune Responses against Simian T-Lymphotropic Virus Type 1 Target Tax in Infected Baboons.

There are currently 5 million to 10 million human T-lymphotropic virus type 1 (HTLV-1)-infected people, and many of them will develop severe complications resulting from this infection. A vaccine is urgently needed in areas where HTLV-1 is endemic. Many vaccines are best tested in nonhuman primate animal models. As a first step in designing an effective HTLV-1 vaccine, we defined the CD8(+) and CD4(+) T cell response against simian T-lymphotropic virus type 1 (STLV-1), a virus closely related to HTLV-1, in olive baboons (Papio anubis). Consistent with persistent antigenic exposure, we observed that STLV-1-specific CD8(+) T cells displayed an effector memory phenotype and usually expressed CD107a, gamma interferon (IFN-γ), and tumor necrosis factor alpha (TNF-α). To assess the viral targets of the cellular immune response in STLV-1-infected animals, we used intracellular cytokine staining to detect responses against overlapping peptides covering the entire STLV-1 proteome. Our results show that, similarly to humans, the baboon CD8(+) T cell response narrowly targeted the Tax protein. Our findings suggest that the STLV-1-infected baboon model may recapitulate some of the important aspects of the human response against HTLV-1 and could be an important tool for the development of immune-based therapy and prophylaxis. HTLV-1 infection can lead to many different and often fatal conditions. A vaccine deployed in areas of high prevalence might reduce the incidence of HTLV-1-induced disease. Unfortunately, there are very few animal models of HTLV-1 infection useful for testing vaccine approaches. Here we describe cellular immune responses in baboons against a closely related virus, STLV-1. We show for the first time that the immune response against STLV-1 in naturally infected baboons is largely directed against the Tax protein. Similar findings in humans and the sequence similarity between the human and baboon viruses suggest that the STLV-1-infected baboon model might be useful for developing a vaccine against HTLV-1.

A simian hemorrhagic fever virus isolate from persistently infected baboons efficiently induces hemorrhagic fever disease in Japanese macaques

Simian hemorrhagic fever virus is an arterivirus that naturally infects species of African nonhuman primates causing acute or persistent asymptomatic infections. Although it was previously estimated that 1% of baboons are SHFV-positive, more than 10% of wild-caught and captive-bred baboons tested were SHFV positive and the infections persisted for more than 10 years with detectable virus in the blood (100–1000 genomes/ml). The sequences of two baboon SHFV isolates that were amplified by a single passage in primary macaque macrophages had a high degree of identity to each other as well as to the genome of SHFV-LVR, a laboratory strain isolated in the 1960s. Infection of Japanese macaques with 100PFU of a baboon isolate consistently produced high level viremia, pro-inflammatory cytokines, elevated tissue factor levels and clinical signs indicating coagulation defects. The baboon virus isolate provides a reliable BSL2 model of viral hemorrhagic fever disease in macaques.

Two novel simian arteriviruses in captive and wild baboons (Papio spp.).

Since the 1960s, simian hemorrhagic fever virus (SHFV; Nidovirales, Arteriviridae) has caused highly fatal outbreaks of viral hemorrhagic fever in captive Asian macaque colonies. However, the source(s) of these outbreaks and the natural reservoir(s) of this virus remain obscure. Here we report the identification of two novel, highly divergent simian arteriviruses related to SHFV, Mikumi yellow baboon virus 1 (MYBV-1) and Southwest baboon virus 1 (SWBV-1), in wild and captive baboons, respectively, and demonstrate the recent transmission of SWBV-1 among captive baboons. These findings extend our knowledge of the genetic and geographic diversity of the simian arteriviruses, identify baboons as a natural host of these viruses, and provide further evidence that baboons may have played a role in previous outbreaks of simian hemorrhagic fever in macaques, as has long been suspected. This knowledge should aid in the prevention of disease outbreaks in captive macaques and supports the growing body of evidence that suggests that simian arterivirus infections are common in Old World monkeys of many different species throughout Africa. Historically, the emergence of primate viruses both in humans and in other primate species has caused devastating outbreaks of disease. One strategy for preventing the emergence of novel primate pathogens is to identify microbes with the potential for cross-species transmission in their natural state within reservoir species from which they might emerge. Here, we detail the discovery and characterization of two related simian members of the Arteriviridae family that have a history of disease emergence and host switching. Our results expand the phylogenetic and geographic range of the simian arteriviruses and define baboons as a natural host for these viruses. Our findings also identify a potential threat to captive macaque colonies by showing that simian arteriviruses are actively circulating in captive baboons.

Pathogenicity of different baboon herpesvirus papio 2 isolates is characterized by either extreme neurovirulence or complete apathogenicity.

In comparisons of the pathogenicity of simian alphaherpesviruses in mice, two isolates of the baboon virus HVP2 were nearly as lethal as monkey B virus, a biological safety level 4 agent (J. W. Ritchey, K. A. Ealey, M. Payton, and R. Eberle, J. Comp. Pathol. 127:150-161, 2002). To confirm these results, mice were inoculated intramuscularly with 10(5) PFU of HVP2 isolates obtained from different baboon subspecies and primate centers. Some of the HVP2 isolates (6 of 13) caused paralysis and death in the mice, while 7 of 13 HVP2 isolates produced no clinical signs of disease. The apathogenic HVP2 isolates (HVP2ap) induced only low levels of serum antiviral immunoglobulin G relative to levels observed in sera from mice infected with the neurovirulent isolates of HVP2 (HVP2nv). Histological examination of tissues from mice inoculated with HVP2nv isolates showed extensive neural tissue destruction, while mice infected with HVP2ap isolates showed no lesions. Tissue samples collected at 48-h intervals postinfection suggested that HVP2ap isolates failed to replicate at the site of inoculation. There was no significant difference in the in vitro replication, plaque size, or cytopathic effect morphology of HVP2ap versus HVP2nv isolates. While HVP2 isolates replicated better in Vero monkey kidney cells than in murine L cells, plaquing efficiency of individual isolates did not correlate with the dichotomous pathogenic properties seen in mice. Phylogenetic analyses of both coding and intergenic regions (US4-6) of the HVP2 genome separated isolates into two distinct clades that correlated with the two in vivo virulence phenotypes. Taken together, these results demonstrate that two subtypes of HVP2 exist that are very closely related but differ dramatically in their ability to cause disease in a murine model.

Relationships between simian and human enteroviruses.

Partial sequences from two genomic regions of simian enteroviruses were analysed and their relatedness to other picornaviruses was compared. Of the 18 simian viruses included in the analysis, sequences were obtained from eleven strains for at least one genomic region. In the 5' non-coding region, SV6, SV19, SV26, SV35, SV43 and SV46 (simian viruses) and BA13 (baboon virus) clearly grouped together with human enteroviruses, whereas SV4, SV28 and SA4 (South African isolate) were more distantly related. In the 3D RNA polymerase-coding region, SV26, SV35, SV43 and SV46 could be clearly identified as enteroviruses and fell into the previously defined cluster A, which contains such human viruses as coxsackievirus A16 and enterovirus 71. However, although SV6 and BA13 were also enterovirus-like, they did not belong to any known genetic cluster of human enteroviruses. Moreover, while SV18 could be recognized as a picornavirus, it did not directly group with members of the genus Enterovirus.

Amplification of simian retroviral sequences from human recipients of baboon liver transplants.

Investigations into the use of baboons as organ donors for human transplant recipients, a procedure called xenotransplantation, have raised the specter of transmitting baboon viruses to humans and possibly establishing new human infectious diseases. Retrospective analysis of tissues from two human transplant recipients with end-stage hepatic disease who died 70 and 27 days after the transplantation of baboon livers revealed the presence of two simian retroviruses of baboon origin, simian foamy virus (SFV) and baboon endogenous virus (BaEV), in multiple tissue compartments. The presence of baboon mitochondrial DNA was also detected in these same tissues, suggesting that xenogeneic "passenger leukocytes" harboring latent or active viral infections had migrated from the xenografts to distant sites within the human recipients. The persistence of SFV and BaEV in human recipients throughout the posttransplant period underscores the potential infectious risks associated with xenotransplantation.

Characterization of New Simian Foamy Viruses from African Nonhuman Primates

Simian foamy viruses (SFV) are exogenous retroviruses present in most if not all nonhuman primate species. Baboons and other African monkey species are known to harbor SFVs, yet there is presently no data in regard to their genetic relationship. Here we studied SFVs from baboons as compared to other SFVs isolated from a Hamlyn's guenon, a patas monkey, and a vervet. By Western blot analysis, thegagprecursor proteins (p74/p70) were detected from all SFVs. In addition, the envelope glycoproteins from a vervet isolate (SFV-Agm2) were comparable in size to theenvprecursor gp130, the exterior glycoprotein (gp70), and the transmembrane protein (gp48) as detected by lentil lectin binding and radioimmunoprecipitation (RIPA). Molecular comparison of PCR amplified products frompoland LTR regions of each SFV demonstrated a close relationship among baboon SFVs while SFVs from patas, Hamlyn's guenon, and vervet clustered together. The baboon viruses only varied by 4% among each other in the LTR region; however, as much as 26% variation was noted when compared to the other African monkey SFVs. To determine the prevalence rate of SFV-Bab in our baboon colony, we employed both Western blotting and PCR analysis. Antibodies to SFVgagprecursor proteins were seen in 7 of 10 infants; however, none were positive by PCR, suggesting that these infants were virus negative and that their antibodies were maternal in origin. Only one juvenile (1/10) and all adults (38/38) were infected with SFV. Taken together these results suggest that SFVs have arisen and diverged along with the evolution of their natural hosts. Furthermore, the high prevalence rates to SFV seen in adult baboons strongly suggest a sexual or oral routes of transmission.

SIV Hunt Leads to Baboon Virus Discovery

SIV Hunt Leads to Baboon Virus Discovery

PCR identification and differentiation of baboon cytomegalovirus from other human and nonhuman primate cytomegalovirus

Background: Differential identification of baboon alpha, beta, and gamma herpesviruses is an essential technology in order to monitor xenozoonotic transmission of baboon viruses to foreign species organ and/or cell recipients. We present polymerase chain reaction techniques that will differentiate known baboon cytomegaloviruses (CMV) from their closely related counterparts found in humans. Methods and Results: Polymerase chain reaction techniques for identification of the known beta herpesviruses commonly present in the baboon are reported. The techniques described also permit the unequivocal differentiation of these virus types from closely related human as well as other nonhuman primate viruses in the family herpesviridae. Methods are based upon sequence analysis of specifically selected genes of baboon CMV. Primer pairs from sequence analyses were selected based upon nonhomologous sequences in gene homologues of human CMV. Unique, baboon species specific amplimers were identified both with ethidium bromide staining and with radiolabeled probe analyses. Conclusions: With the described techniques, it is possible to monitor organ/cell recipients of xenograft transplantation for the establishment of baboon CMV in the foreign human host. Monitoring can be performed throughout the life of the recipient in effort to rule out host susceptibility to baboon CMV, as well as to rule out potential host:donor recombinant viruses formed between the closely related members of herpesvirus family. (Mol Diagn 1996 Sep;1(3):267-273)

Herpesvirus papio 2, an SA8-like alpha-herpesvirus of baboons.

Several SA8 isolates obtained from baboons were compared to the prototype SA8 herpesvirus of African green monkeys. SDS-PAGE and restriction enzyme analyses revealed definite differences between green monkey and baboon isolates. DNA and amino acid sequences of the gB, gD and gJ glycoprotein genes exhibited substantial differences in variable regions. For the gB and gD, the amount of amino acid substitutions between SA8 and the baboon viruses was comparable to levels observed between analogous genes of SA8 & B virus or HSV1 & HSV2. Although a high degree of antigenic cross-reactivity was apparent, virus-specific antigenic determinants were also readily detected. Phylogenetic analyses supported separation of the baboon isolates and SA8 as distinct viruses. Taken together these results suggest that although closely related to SA8, the baboon viruses represent a distinct simian alpha-herpesvirus which we propose be designated Herpesvirus papio 2.

Characterization of a new polyomavirus (Polyomavirus papionis-2) isolated from baboon kidney cell cultures

Viruses with papovavirus morphology were seen in fluids from baboon kidney cell cultures on three separate occasions (isolates A, B, and C). The size of the virions, 47.9 nm, placed the virus in the polyomavirus genus. It grew well in baboon kidney and Vero cells and less well in human embryo lung (HEL) fibroblasts. The virus could not be identified as the previously described baboon polyomavirus, SA 12, or as any of the other known primate polyomaviruses BK, JC or SV 40, the non-primate viruses mouse polyoma, K, rabbit kidney vacuolating virus (RKV) or bovine polyomavirus (FRKV) by immunofluorescence, immune electron microscopy or hemagglutination inhibition (HI) tests. A rabbit antiserum to the new virus (isolate A) reacted only with the three isolates and not with the other primate polyomaviruses studied. Thirteen percent of 118 wild-caught baboons (Papio anubis) had HI antibody to the new polyomavirus and 21 percent were seropositive for SA 12; only two baboons had antibody to both viruses. These results suggest that in baboons there are two antigenically distinct polyomaviruses which circulate independently. The two viruses may also be distinguished by their hemagglutinating properties: SA 12 agglutinated erythrocytes from a wider range of species but only the newly recognized polyomavirus agglutinated baboon erythrocytes. We propose that the two baboon viruses, SA 12 and the new virus, should be named Polyomavirus papionis-1 and Polyomavirus papionis-2 respectively.

Serological evidence for variation in the incidence of herpesvirus infections in different species of apes

Sera from captive lowland gorillas, chimpanzees, orangutans, and gibbons were screened by enzyme-linked immunosorbent assay (ELISA) for antibody to herpesviruses serologically related to human herpes simplex virus types 1 and 2 (HSV-1, HSV-2), a baboon virus (SA8), and a macaque herpesvirus (B virus). The incidence of herpesvirus antibodies varied considerably among the different species, gorillas having the highest incidence of seropositivity (65.4%) and orangutans the lowest. The virus specificity of positive sera was further analyzed by examining the kinetics of virus neutralization, competition of reactivity in ELISAs, and immunoblotting against HSV-1, HSV-2, SA8, and B virus antigens. Using these assays, the majority of positive gorilla sera (49 of 53, 92%) were determined to react in a manner identical to human HSV-1 immune sera. The remaining four positive gorilla sera reacted as HSV-2-positive sera. In contrast, the majority of positive chimpanzee sera (5 of 7, 71%) reacted as HSV-2 immune rather than HSV-1 immune. All positive sera from gibbon apes reacted as HSV-1 positive. No orangutan sera were identified which gave positive reactions by ELISAs to any of the four primate herpesviruses tested. Although four orangutan sera gave equivocal results against HSV-1 antigen, further analysis by immunoblotting could not confirm any specific reactivity with any of the primate herpesvirus antigens. Varied reactivity among individual animals with both SA8 and B virus proteins was observed, but none of the seropositive primates detected appeared to be infected with either of these simian viruses. Three gorilla sera had antigen recognition patterns slightly different from those of HSV-2-positive human and chimpanzee sera and another HSV-2-positive gorilla serum, raising the possibility that these animals harbor an indigenous virus related to HSV-2.

Comparative Oligonucleotide Analysis of Exogenous and Endogenous Primate Type C Viruses

RNAs of representative viruses of the exogenous simian sarcoma virus-gibbon ape lymphosarcoma virus (SiSV/GALV) and endogenous baboon virus (BaEV) classes of subhuman primate type C viruses were compared and related to HEL-12 virus, an isolate derived from human embryonic lung cells. The extent of sequence identity between different viral RNA preparations was determined by comparison of fingerprint patterns obtained after electrophoretic separation of RNase T1-resistant oligonucleotides. The studies presented indicate that HEL-12 viral RNA and simian sarcoma-simian associated virus [SiSV(SSAV)] RNA share 90 to 95% of the large oligonucleotides. From 5 to 10% of virus-specific oligonucleotides were detected in each of several virus preparations examined and their occurrence was independent of the cell line on which the virus ws propagated. HEL-12 virus and GALV-SF have 50% unique oligonucleotides in common. These are the same oligonucleotides that are shared between GALV-SF and SisV(SSAV) RNA. Two BaEV isolates, M7 and BILN, and RD114, and BaEV-related endogenous virus of cats, each easily displayed distinguishable oligonucleotides patterns. Large oligonucleotides characteristic for these three endogenous virus isolates were not detected in the fingerprints of HEL-12 virus, SiSV(SSAV) and GALV-SF.

Conserved sequence related to the 3'-terminal region of retrovirus RNA'S In normal cellular DNAs.

The nucleotide sequences related to the 3'-terminal protion of retrovirus genomic RNA have been detected in the DNA of animals, including humans. The DNA complementary to the 400 to 700 nucleotides from the 3'-terminal end of retrovirus RNA (cDNA3'), which contains the enriched conserved region, was hybridized with DNA from a variety of animal cells. Under the conditions of annealing in 0.72 M NaCl at 67 degrees C and hydroxyapatite chromatography at 55 degrees C, 20 to 50% of the radioactivity of the cDNA3' prepared from two retroviruses, a murine Rauscher virus (RLV) and a baboon virus (M7), annealed with normal cellular DNA of animals, including human tissue. The thermal denaturation profile revealed considerable mismatching between the duplex of the cDNA3' and human DNA, cDNA3' of retroviruses is most homologous to cellular DNA of the host species of origin and is less homologous to cellular DNA of species that are distant in the phylogeny of the host species. The conservation and evolution of nucleotide sequences related to the 3' end of retrovirus genomes in animal DNAs, including humans, suggest that the sequences may have important functions.

Conserved Region of Mammalian Retrovirus RNA

The viral RNAs of various mammalian retroviruses contain highly conserved sequences close to their 3' ends. This was demonstrated by interviral molecular hybridization between fractionated viral complementary DNA (cDNA) and RNA. cDNA near the 3' end (cDNA(3')) from a rat virus (RPL strain) was fractionated by size and mixed with mouse virus RNA (Rauscher leukemia virus). No hybridization occurred with total cDNA (cDNA(total)), in agreement with previous results, but a cross-reacting sequence was found with the fractionated cDNA(3'). The sequences between 50 to 400 nucleotides from the 3' terminus of heteropolymeric RNA were most hybridizable. The rat viral cDNA(3') hybridized with mouse virus RNA more extensively than with RNA of remotely related retroviruses. The related viral sequence of the rodent viruses (mouse and rat) showed as much divergence in heteroduplex thermal denaturation profiles as did the unique sequence DNA of these two rodents. This suggests that over a period of time, rodent viruses have preserved a sequence with changes correlated to phylogenetic distance of hosts. The cross-reacting sequence of replication-competent retroviruses was conserved even in the genome of the replication-defective sarcoma virus and was also located in these genomes near the 3' end of 30S RNA. A fraction of RD114 cDNA(3'), corresponding to the conserved region, cross-hybridized extensively with RNA of a baboon endogenous virus (M7). Fractions of similar size prepared from cDNA(3') of MPMV, a primate type D virus, hybridized with M7 RNA to a lesser extent. Hybridization was not observed between Mason-Pfizer monkey virus and M7 if total cDNA's were incubated with viral RNAs. The degree of cross-reaction of the shared sequence appeared to be influenced by viral ancestral relatedness and host cell phylogenetic relationships. Thus, the strikingly high extent of cross-reaction at the conserved region between rodent viruses and simian sarcoma virus and between baboon virus and RD114 virus may reflect ancestral relatedness of the viruses. Slight cross-reaction at the site between type B and C viruses of rodents (mouse mammary tumor virus and RPL virus, 58-2T) or type C and D viruses of primates (M7, RD114, and Mason-Pfizer monkey virus) may have arisen at the conserved region through a mechanism that depends more on the phylogenetic relatedness of the host cells than on the viral type or origin. Determining the sequence of the conserved region may help elucidate this mechanism. The conserved sequences in retroviruses described here may be an important functional unit for the life cycle of many retroviruses.

Sequences Homologous to BAV Component of HL23V in Baboon Tissues

The BAV component of HL23V virus (HL23V-BAB) hybridized to DNA from different Baboon tissues and appears to be an endogenous Baboon virus. Competition hybridization studies show that HL23V-BAB is closely related to viruses isolated from various Baboon species: P. hamadrys, P. papio, and P. cynocephalus. Competition hybridization studies also show that normal Baboon tissues contain more copies of proviral DNA than cells infected in vitro.

Antibody responses to herpesvirus papio antigens in baboons with lymphoma

An Epstein-Barr virus-related herpesvirus, termed Herpesvirus papio (HVP), was isolated from baboons (Papio hamadryas) at the Institute of Experimental Pathology and Therapy, Sukhumi, USSR, where there is a continuing outbreak of lymphoma. In the present study sera from diseased baboons and from age- and sex-matched control animals were examined for antibodies to HVP antigens. Results showed that animals with lymphoid disease had antibodies to HVP virus capsid, early, soluble, and nuclear antigens at higher frequencies and at higher titers than did control animals. Antibody titers were not age- or sex-related. No concordancy was detected for antibodies to soluble and nuclear antigens. The sera were also examined for antibodies to two other widely distributed viruses of hamadryas baboons, cytomegalovirus and foamy virus. The results of these studies did not indicate a disease-related role for either of these viruses.

A review of Herpesvirus papio, a B-lymphotropic virus of baboons related to EBV

In the last four year B-lymphotropic herpesvirus have been identified as indigenous viruses of chimpanzees, baboons, orang-utans and gorillas. These viruses are related to Epstein-Barr virus (EBV) as demonstrated by cross-reactivity of certain viral antigens and partial viral genome homology. In addition they share certain biologic properties in common with EBV, i.e. replication limited only to B-lymphocytic cells, transformation of lymphocytes in vitro, and potential for inducing lymphoproliferative disease in susceptible hosts. Herpesvirus papio (HVP) the indigenous virus of baboons ( Papio sp.), has been the most extensively studied of this group of viruses and this review summarizes and compares with EBV the relevant properties of HVP.