COVID-19 cynomolgus macaque model reflecting human COVID-19 pathological conditions.

The pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a global threat to human health and life. A useful pathological animal model accurately reflecting human pathology is needed to overcome the COVID-19 crisis. In the present study, COVID-19 cynomolgus monkey models including monkeys with underlying diseases causing severe pathogenicity such as metabolic disease and elderly monkeys were examined. Cynomolgus macaques with various clinical conditions were intranasally and/or intratracheally inoculated with SARS-CoV-2. Infection with SARS-CoV-2 was found in mucosal swab samples, and a higher level and longer period of viral RNA was detected in elderly monkeys than in young monkeys. Pneumonia was confirmed in all of the monkeys by computed tomography images. When monkeys were readministrated SARS-CoV-2 at 56 d or later after initial infection all of the animals showed inflammatory responses without virus detection in swab samples. Surprisingly, in elderly monkeys reinfection showed transient severe pneumonia with increased levels of various serum cytokines and chemokines compared with those in primary infection. The results of this study indicated that the COVID-19 cynomolgus monkey model reflects the pathophysiology of humans and would be useful for elucidating the pathophysiology and developing therapeutic agents and vaccines.

Use of convalescent serum reduces severity of COVID-19 in nonhuman primates.

Passive transfer of convalescent plasma or serum is a time-honored strategy for treating infectious diseases. Human convalescent plasma containing antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently being used to treat patients with coronavirus disease 2019 where clinical efficacy trials are ongoing. Here, we assess therapeutic passive transfer in groups of SARS-CoV-2-infected African green monkeys with convalescent sera containing either high or low anti-SARS-CoV-2 neutralizing antibody titers. Differences in viral load and pathology are minimal between monkeys that receive the lower titer convalescent sera and untreated controls. However, lower levels of SARS-CoV-2 in respiratory compartments, reduced severity of virus-associated lung pathology, and reductions in coagulopathy and inflammatory processes are observed in monkeys that receive high titer sera versus untreated controls. Our data indicate that convalescent plasma therapy in humans may be an effective strategy provided that donor sera contain high anti-SARS-CoV-2 neutralizing titers given in early stages of the disease.

Social history and exposure to pathogen signals modulate social status effects on gene regulation in rhesus macaques.

Social experience is an important predictor of disease susceptibility and survival in humans and other social mammals. Chronic social stress is thought to generate a proinflammatory state characterized by elevated antibacterial defenses and reduced investment in antiviral defense. Here we manipulated long-term social status in female rhesus macaques to show that social subordination alters the gene expression response to ex vivo bacterial and viral challenge. As predicted by current models, bacterial lipopolysaccharide polarizes the immune response such that low status corresponds to higher expression of genes in NF-κB-dependent proinflammatory pathways and lower expression of genes involved in the antiviral response and type I IFN signaling. Counter to predictions, however, low status drives more exaggerated expression of both NF-κB- and IFN-associated genes after cells are exposed to the viral mimic Gardiquimod. Status-driven gene expression patterns are linked not only to social status at the time of sampling, but also to social history (i.e., past social status), especially in unstimulated cells. However, for a subset of genes, we observed interaction effects in which females who fell in rank were more strongly affected by current social status than those who climbed the social hierarchy. Taken together, our results indicate that the effects of social status on immune cell gene expression depend on pathogen exposure, pathogen type, and social history-in support of social experience-mediated biological embedding in adulthood, even in the conventionally memory-less innate immune system.

Serological Analysis of Herpes B Virus at Individual Epitope Resolution: From Two-Dimensional Peptide Arrays to Multiplex Bead Flow Assays.

Macacine herpesvirus or B Virus (BV) is a zoonotic agent that leads to high mortality rates in humans if transmitted and untreated. Here, BV is used as a test case to establish a two-step procedure for developing high throughput serological assays based on synthetic peptides. In step 1, peptide microarray analysis of 42 monkey sera (30 of them tested BV positive by ELISA) revealed 1148 responses against 369 different peptides. The latter could be grouped into 142 different antibody target regions (ATRs) in six different glycoproteins (gB, gC, gD, gG, gH, and gL) of BV. The high number of newly detected ATRs was made possible inter alia by a new preanalytical protocol that reduced unspecific binding of serum components to the cellulose-based matrix of the microarray. In step 2, soluble peptides corresponding to eight ATRs of particularly high antigenicity were synthesized and coupled to fluorescently labeled beads, which were subsequently employed in immunochemical bead flow assays. Their outcome mirrored the ELISA results used as reference. Hence, convenient, fast, and economical screening of arbitrarily large macaque colonies for BV infection is now possible. The study demonstrates that a technology platform switch from two-dimensional high-resolution peptide arrays used for epitope discovery to a readily available bead array platform for serology applications is feasible.

Post-exposure immunotherapy for two ebolaviruses and Marburg virus in nonhuman primates.

The 2013-2016 Ebola virus (EBOV) disease epidemic demonstrated the grave consequences of filovirus epidemics in the absence of effective therapeutics. Besides EBOV, two additional ebolaviruses, Sudan (SUDV) and Bundibugyo (BDBV) viruses, as well as multiple variants of Marburg virus (MARV), have also caused high fatality epidemics. Current experimental EBOV monoclonal antibodies (mAbs) are ineffective against SUDV, BDBV, or MARV. Here, we report that a cocktail of two broadly neutralizing ebolavirus mAbs, FVM04 and CA45, protects nonhuman primates (NHPs) against EBOV and SUDV infection when delivered four days post infection. This cocktail when supplemented by the anti-MARV mAb MR191 exhibited 100% efficacy in MARV-infected NHPs. These findings provide a solid foundation for clinical development of broadly protective immunotherapeutics for use in future filovirus epidemics.

[Markers of hepatitis A in the monkeys of the Adlers primate center.]

Hepatitis A is a widespread viral infection. The HAV strains of "human" and "monkey" origin are similar in their morphological and antigenic properties, but differ genotypically. OBJECTIVES: The aim of this research was a comparative study of serological and molecular-genetic markers of HAV infection in monkeys born at the Adler Primate Center and in those imported from different countries. MATERIAL AND METHODS: Fecal samples (n = 313) and serum (n = 266) from various species of monkey using ELISA and RT-PCR were studied. RESULTS AND DISCUSSION: The frequency of anti-HAV-IgG was high (78.9%) in imported animals (vervet monkeys from Tanzania and cynomolgus monkeys from Vietnam) and as well as in various species of monkeys (rhesus monkeys, cynomolgus monkeys, green monkeys and papio hamadryas) of the Center (88.6%). At the same time, in the imported monkeys, the markers of "fresh" HAV infection (IgM-27.2%, Ag-HAV-16.7%, RNA-22.0%) were detected significantly more often (p> 0.05) than in monkeys kept at the Colony (IgM-7.5%, HAV-Ag - 5.2%, RNA - 3.6%). In general, anti-IgG reactivity ranged from 1.064 to 2.073 OD450, anti-IgM ranged from 0.546 to 1.059 OD450. The number of HAV-Ag was 0.496 - 1.995 OD450. RNA HAV only in rhesus monkeys and cynomolgys monkeys born at the Colony, as well as in imported vervet monkeys was detected. CONCLUSIONS: The data obtained indicate a wide circulation of HAV among monkeys born in the Adler Primate Center and among the imported animals. Markers of "fresh" HAV infection varied depending on the species of monkeys and their origin.

Persistent Marburg Virus Infection in the Testes of Nonhuman Primate Survivors.

Sexual transmission of filoviruses was first reported in 1968 after an outbreak of Marburg virus (MARV) disease and recently caused flare-ups of Ebola virus disease in the 2013-2016 outbreak. How filoviruses establish testicular persistence and are shed in semen remain unknown. We discovered that persistent MARV infection of seminiferous tubules, an immune-privileged site that harbors sperm production, is a relatively common event in crab-eating macaques that survived infection after antiviral treatment. Persistence triggers severe testicular damage, including spermatogenic cell depletion and inflammatory cell invasion. MARV mainly persists in Sertoli cells, leading to breakdown of the blood-testis barrier formed by inter-Sertoli cell tight junctions. This disruption is accompanied by local infiltration of immunosuppressive CD4+Foxp3+ regulatory T cells. Our study elucidates cellular events associated with testicular persistence that may promote sexual transmission of filoviruses and suggests that targeting immunosuppression may be warranted to clear filovirus persistence in damaged immune-privileged sites.

A Tale of Two Viruses: Does Heterologous Flavivirus Immunity Enhance Zika Disease?

The rise of Zika virus (ZIKV) and its unusual clinical manifestations provided ground for speculative debate. The clinical severity of secondary dengue virus (DENV) infections is associated with antibody-dependent enhancement (ADE), and it was recently suggested that previous exposure to DENV may worsen ZIKV clinical outcomes. In this Opinion article we analyze the relationship among different flaviviruses and ADE. We discuss new evidence obtained in non-human primates and human cohorts demonstrating that there is no correlation to ADE when ZIKV infection occurs in the presence of pre-existing DENV immunity. We propose a redefinition of ADE in the context of complex immunological flavivirus interactions to provide a more objective perspective when translating in vitro or in vivo observations into the clinical setting.

Antibody Responses to Zika Virus Infections in Environments of Flavivirus Endemicity.

Zika virus (ZIKV) infections occur in areas where dengue virus (DENV), West Nile virus (WNV), yellow fever virus (YFV), and other viruses of the genus Flavivirus cocirculate. The envelope (E) proteins of these closely related flaviviruses induce specific long-term immunity, yet subsequent infections are associated with cross-reactive antibody responses that may enhance disease susceptibility and severity. To gain a better understanding of ZIKV infections against a background of similar viral diseases, we examined serological immune responses to ZIKV, WNV, DENV, and YFV infections of humans and nonhuman primates (NHPs). Using printed microarrays, we detected very specific antibody responses to primary infections with probes of recombinant E proteins from 15 species and lineages of flaviviruses pathogenic to humans, while high cross-reactivity between ZIKV and DENV was observed with 11 printed native viruses. Notably, antibodies from human primary ZIKV or secondary DENV infections that occurred in areas where flavivirus is endemic broadly recognized E proteins from many flaviviruses, especially DENV, indicating a strong influence of infection history on immune responses. A predictive algorithm was used to tentatively identify previous encounters with specific flaviviruses based on serum antibody interactions with the multispecies panel of E proteins. These results illustrate the potential impact of exposure to related viruses on the outcome of ZIKV infection and offer considerations for development of vaccines and diagnostics.

Initiation of Antiretroviral Therapy Restores CD4+ T Memory Stem Cell Homeostasis in Simian Immunodeficiency Virus-Infected Macaques.

UNLABELLED: Treatment of human immunodeficiency virus (HIV) infection with antiretroviral therapy (ART) has significantly improved prognosis. Unfortunately, interruption of ART almost invariably results in viral rebound, attributed to a pool of long-lived, latently infected cells. Based on their longevity and proliferative potential, CD4(+) T memory stem cells (TSCM) have been proposed as an important site of HIV persistence. In a previous study, we found that in simian immunodeficiency virus (SIV)-infected rhesus macaques (RM), CD4(+) TSCM are preserved in number but show (i) a decrease in the frequency of CCR5(+) cells, (ii) an expansion of the fraction of proliferating Ki-67(+) cells, and (iii) high levels of SIV DNA. To understand the impact of ART on both CD4(+) TSCM homeostasis and virus persistence, we conducted a longitudinal analysis of these cells in the blood and lymph nodes of 25 SIV-infected RM. We found that ART induced a significant restoration of CD4(+) CCR5(+) TSCM both in blood and in lymph nodes and a reduction in the fraction of proliferating CD4(+) Ki-67(+) TSCM in blood (but not lymph nodes). Importantly, we found that the level of SIV DNA in CD4(+) transitional memory (TTM) and effector memory (TEM) T cells declined ∼100-fold after ART in both blood and lymph nodes, while the level of SIV DNA in CD4(+) TSCM and central memory T cells (TCM-) did not significantly change. These data suggest that ART is effective at partially restoring CD4(+) TSCM homeostasis, and the observed stable level of virus in TSCM supports the hypothesis that these cells are a critical contributor to SIV persistence. IMPORTANCE: Understanding the roles of various CD4(+) T cell memory subsets in immune homeostasis and HIV/SIV persistence during antiretroviral therapy (ART) is critical to effectively treat and cure HIV infection. T memory stem cells (TSCM) are a unique memory T cell subset with enhanced self-renewal capacity and the ability to differentiate into other memory T cell subsets, such as central and transitional memory T cells (TCM and TTM, respectively). CD4(+) TSCM are disrupted but not depleted during pathogenic SIV infection. We find that ART is partially effective at restoring CD4(+) TSCM homeostasis and that SIV DNA harbored within this subset contracts more slowly than virus harbored in shorter-lived subsets, such as TTM and effector memory (TEM). Because of their ability to persist long-term in an individual, understanding the dynamics of virally infected CD4(+) TSCM during suppressive ART is important for future therapeutic interventions aimed at modulating immune activation and purging the HIV reservoir.

Characterization of the immune response in ganglia after primary simian varicella virus infection.

Primary simian varicella virus (SVV) infection in non-human primates causes varicella, after which the virus becomes latent in ganglionic neurons and reactivates to cause zoster. The host response in ganglia during establishment of latency is ill-defined. Ganglia from five African green monkeys (AGMs) obtained at 9, 13, and 20 days post-intratracheal SVV inoculation (dpi) were analyzed by ex vivo flow cytometry, immunohistochemistry, and in situ hybridization. Ganglia at 13 and 20 dpi exhibited mild inflammation. Immune infiltrates consisted mostly of CD8(dim) and CD8(bright) memory T cells, some of which expressed granzyme B, and fewer CD11c(+) and CD68(+) cells. Chemoattractant CXCL10 transcripts were expressed in neurons and infiltrating inflammatory cells but did not co-localize with SVV open reading frame 63 (ORF63) RNA expression. Satellite glial cells expressed increased levels of activation markers CD68 and MHC class II at 13 and 20 dpi compared to those at 9 dpi. Overall, local immune responses emerged as viral DNA load in ganglia declined, suggesting that intra-ganglionic immunity contributes to restricting SVV replication.

Non-human Primate Lymphocryptoviruses: Past, Present, and Future.

Epstein-Barr virus (EBV) orthologues from non-human primates (NHPs) have been studied for nearly as long as EBV itself. Cross-reactive sera and DNA hybridization studies provided the first glimpses of the closely related herpesviruses that belonged to the same gamma-1 herpesvirus, or lymphocryptovirus, genus, as EBV. Over the years, detailed molecular and sequence analyses of LCVs that infect humans and other NHPs revealed similar colinear genome structures and homologous viral proteins expressed during latent and lytic infection. Despite these similarities, experimental infection of NHPs with EBV did not result in acute symptoms or persistent infection as observed in humans, suggesting some degree of host species restriction. Genome sequencing and a molecular clone of an LCV isolate from naturally infected rhesus macaques combined with domestic colonies of LCV-naïve rhesus macaques have opened the door to a unique experimental animal model that accurately reproduces the normal transmission, acute viremia, lifelong persistence, and immune responses found in EBV-infected humans. This chapter will summarize the advances made over the last 50 years in our understanding of LCVs that naturally infect both Old and New World NHPs, the recent, groundbreaking developments in the use of rhesus macaques as an animal model for EBV infection, and how NHP LCVs and the rhLCV animal model can advance future EBV research and the development of an EBV vaccine.

Evidence That Rhesus Macaques Self-Cure from a Schistosoma japonicum Infection by Disrupting Worm Esophageal Function: A New Route to an Effective Vaccine?

BACKGROUND: Rhesus macaques are unusual among schistosome hosts, self-curing from an established infection and thereafter manifesting solid immunity against a challenge, an ideal model for vaccine development. Previously, the immunological basis of self-cure was confirmed; surviving worms had ceased feeding but how immunological pressure achieved this was unclear. The schistosome esophagus is not simply a conduit for blood but plays a central role in its processing. Secretions from the anterior and posterior esophageal glands mix with incoming blood causing erythrocyte lysis and tethering and killing of leucocytes. METHODOLOGY/PRINCIPAL FINDINGS: We have analysed the self-cure process in rhesus macaques infected with Schistosoma japonicum. Faecal egg output and circulating antigen levels were used to chart the establishment of a mature worm population and its subsequent demise. The physiological stress of surviving females at perfusion was especially evident from their pale, shrunken appearance, while changes in the structure and function of the esophagus were observed in both sexes. In the anterior region electron microscopy revealed that the vesicle secretory process was disrupted, the tips of lining corrugations being swollen by greatly enlarged vesicles and the putative sites of vesicle release obscured by intense deposits of IgG. The lumen of the posterior esophagus in starving worms was occluded by cellular debris and the lining cytoplasmic plates were closely adherent, also potentially preventing secretion. Seven proteins secreted by the posterior gland were identified and IgG responses were detected to some or all of them. Intrinsic rhesus IgG colocalized with secreted SjMEGs 4.1, 8.2, 9, 11 and VAL-7 on cryosections, suggesting they are potential targets for disruption of function. CONCLUSIONS/SIGNIFICANCE: Our data suggest that rhesus macaques self-cure by blocking esophagus function with antibody; the protein products of the glands provide a new class of potential vaccine targets.

Abortive intrabronchial infection of rhesus macaques with varicella-zoster virus provides partial protection against simian varicella virus challenge.

UNLABELLED: Varicella-zoster virus (VZV) is a human neurotropic alphaherpesvirus and the etiological agent of varicella (chickenpox) and herpes zoster (HZ, shingles). Previously, inoculation of monkeys via the subcutaneous, intratracheal, intravenous, or oral-nasal-conjunctival routes did not recapitulate all the hallmarks of VZV infection, including varicella, immunity, latency, and reactivation. Intrabronchial inoculation of rhesus macaques (RMs) with simian varicella virus (SVV), a homolog of VZV, recapitulates virologic and immunologic hallmarks of VZV infection in humans. Given that VZV is acquired primarily via the respiratory route, we investigated whether intrabronchial inoculation of RMs with VZV would result in a robust model. Despite the lack of varicella and viral replication in either the lungs or whole blood, all four RMs generated an immune response characterized by the generation of VZV-specific antibodies and T cells. Two of 4 VZV-inoculated RMs were challenged with SVV to determine cross-protection. VZV-immune RMs displayed no varicella rash and had lower SVV viral loads and earlier and stronger humoral and cellular immune responses than controls. In contrast to the results for SVV DNA, no VZV DNA was detected in sensory ganglia at necropsy. In summary, following an abortive VZV infection, RMs developed an adaptive immune response that conferred partial protection against SVV challenge. These data suggest that a replication-incompetent VZV vaccine that does not establish latency may provide sufficient protection against VZV disease and that VZV vaccination of RMs followed by SVV challenge provides a model to evaluate new vaccines and therapeutics against VZV. IMPORTANCE: Although VZV vaccine strain Oka is attenuated, it can cause mild varicella, establish latency, and in rare cases, reactivate to cause herpes zoster (HZ). Moreover, studies suggest that the HZ vaccine (Zostavax) only confers short-lived immunity. The development of more efficacious vaccines would be facilitated by a robust animal model of VZV infection. The data presented in this report show that intrabronchial inoculation of rhesus macaques (RMs) with VZV resulted in an abortive VZV infection. Nevertheless, all animals generated a humoral and cellular immune response that conferred partial cross-protection against simian varicella virus (SVV) challenge. Additionally, VZV DNA was not detected in the sensory ganglia, suggesting that viremia might be required for the establishment of latency. Therefore, VZV vaccination of RMs followed by SVV challenge is a model that will support the development of vaccines that boost protective T cell responses against VZV.

African green monkeys recapitulate the clinical experience with replication of live attenuated pandemic influenza virus vaccine candidates.

Live attenuated cold-adapted (ca) H5N1, H7N3, H6N1, and H9N2 influenza vaccine viruses replicated in the respiratory tract of mice and ferrets, and 2 doses of vaccines were immunogenic and protected these animals from challenge infection with homologous and heterologous wild-type (wt) viruses of the corresponding subtypes. However, when these vaccine candidates were evaluated in phase I clinical trials, there were inconsistencies between the observations in animal models and in humans. The vaccine viruses did not replicate well and immune responses were variable in humans, even though the study subjects were seronegative with respect to the vaccine viruses before vaccination. Therefore, we sought a model that would better reflect the findings in humans and evaluated African green monkeys (AGMs) as a nonhuman primate model. The distribution of sialic acid (SA) receptors in the respiratory tract of AGMs was similar to that in humans. We evaluated the replication of wt and ca viruses of avian influenza (AI) virus subtypes H5N1, H6N1, H7N3, and H9N2 in the respiratory tract of AGMs. All of the wt viruses replicated efficiently, while replication of the ca vaccine viruses was restricted to the upper respiratory tract. Interestingly, the patterns and sites of virus replication differed among the different subtypes. We also evaluated the immunogenicity and protective efficacy of H5N1, H6N1, H7N3, and H9N2 ca vaccines. Protection from wt virus challenge correlated well with the level of serum neutralizing antibodies. Immune responses were slightly better when vaccine was delivered by both intranasal and intratracheal delivery than when it was delivered intranasally by sprayer. We conclude that live attenuated pandemic influenza virus vaccines replicate similarly in AGMs and human subjects and that AGMs may be a useful model to evaluate the replication of ca vaccine candidates. Importance: Ferrets and mice are commonly used for preclinical evaluation of influenza vaccines. However, we observed significant inconsistencies between observations in humans and in these animal models. We used African green monkeys (AGMs) as a nonhuman primate (NHP) model for a comprehensive and comparative evaluation of pairs of wild-type and pandemic live attenuated influenza virus vaccines (pLAIV) representing four subtypes of avian influenza viruses and found that pLAIVs replicate similarly in AGMs and humans and that AGMs can be useful for evaluation of the protective efficacy of pLAIV.

Postnatal acquisition of primary rhesus cytomegalovirus infection is associated with prolonged virus shedding and impaired CD4+ T lymphocyte function.

BACKGROUND: Although virus-specific CD4(+) T lymphocytes emerge rapidly during primary cytomegalovirus (CMV) infection in humans, they exhibit a state of prolonged functional exhaustion of unknown etiology. To investigate the suitability of rhesus macaques as a model of primary human CMV infection, we examined the virologic and immunologic features of naturally acquired primary CMV infection in rhesus macaques. METHODS: CMV-specific CD4(+) T lymphocytes and CMV load in blood, saliva, and urine were evaluated in a cohort of simian immunodeficiency virus (SIV)-negative rhesus macaques stratified by age into infant, juvenile, and adult groups. RESULTS: CMV infection was detected in juvenile and adult monkeys but not in infant monkeys. CMV loads and shedding frequency in urine and saliva were significantly higher in the 2-3-year old juvenile monkeys, compared with the adult monkeys. The increased CMV load in juvenile monkeys was associated with lower polyfunctionality, impaired proliferation, and increased expression of the inhibitory receptor PD-1 in CMV-specific CD4(+) T lymphocytes. The proliferative defect was partially reversible by exogenous PD-1 blockade or addition of interleukin 2. CONCLUSIONS: Postnatal acquisition of primary CMV infection in rhesus macaques results in prolonged virus excretion and impaired CMV-specific CD4(+) T-lymphocyte function, findings that recapitulate key features of primary CMV infection in humans.

Production of CXC and CC chemokines by human antigen-presenting cells in response to Lassa virus or closely related immunogenic viruses, and in cynomolgus monkeys with lassa fever.

The pathogenesis of Lassa fever (LF), a hemorrhagic fever endemic to West Africa, remains unclear. We previously compared Lassa virus (LASV) with its genetically close, but nonpathogenic homolog Mopeia virus (MOPV) and demonstrated that the strong activation of antigen-presenting cells (APC), including type I IFN production, observed in response to MOPV probably plays a crucial role in controlling infection. We show here that human macrophages (MP) produce large amounts of CC and CXC chemokines in response to MOPV infection, whereas dendritic cells (DC) release only moderate amounts of CXC chemokines. However, in the presence of autologous T cells, DCs produced CC and CXC chemokines. Chemokines were produced in response to type I IFN synthesis, as the levels of both mediators were strongly correlated and the neutralization of type I IFN resulted in an inhibition of chemokine production. By contrast, LASV induced only low levels of CXCL-10 and CXCL-11 production. These differences in chemokine production may profoundly affect the generation of virus-specific T-cell responses and may therefore contribute to the difference of pathogenicity between these two viruses. In addition, a recombinant LASV (rLASV) harboring the NP-D389A/G392A mutations, which abolish the inhibition of type I IFN response by nucleoprotein (NP), induced the massive synthesis of CC and CXC chemokines in both DC and MP, confirming the crucial role of arenavirus NP in immunosuppression and pathogenicity. Finally, we confirmed, using PBMC samples and lymph nodes obtained from LASV-infected cynomolgus monkeys, that LF was associated with high levels of CXC chemokine mRNA synthesis, suggesting that the very early synthesis of these mediators may be correlated with a favourable outcome.

Identification of a vir-orthologous immune evasion gene family from primate malaria parasites.

The immune evasion gene family of malaria parasites encodes variant surface proteins that are expressed at the surface of infected erythrocytes and help the parasite in evading the host immune response by means of antigenic variation. The identification of Plasmodium vivax vir orthologous immune evasion gene family from primate malaria parasites would provide new insight into the evolution of virulence and pathogenesis. Three vir subfamilies viz. vir-B, vir-D and vir-G were successfully PCR amplified from primate malaria parasites, cloned and sequenced. DNA sequence analysis confirmed orthologues of vir-D subfamily in Plasmodium cynomolgi, Plasmodium simium, Plasmodium simiovale and Plasmodium fieldi. The identified vir-D orthologues are 1-9 distinct members of the immune evasion gene family which have 68-83% sequence identity with vir-D and 71.2-98.5% sequence identity within the members identified from primate malaria parasites. The absence of other vir subfamilies among primate malaria parasites reflects the limitations in the experimental approach. This study clearly identified the presence of vir-D like sequences in four species of Plasmodium infecting primates that would be useful in understanding the evolution of virulence in malaria parasites.

Loss of memory CD4+ T-cells in semi-wild mandrills (Mandrillus sphinx) naturally infected with species-specific simian immunodeficiency virus SIVmnd-1.

Simian immunodeficiency virus (SIV) infection is found in a number of African primate species and is thought to be generally non-pathogenic. However, studies of wild primates are limited to two species, with SIV infection appearing to have a considerably different outcome in each. Further examination of SIV-infected primates exposed to their natural environment is therefore warranted. We performed a large cross-sectional study of a cohort of semi-wild mandrills with naturally occurring SIV infection, including 39 SIV-negative and 33 species-specific SIVmnd-1-infected animals. This study was distinguished from previous reports by considerably greater sample size, examination of exclusively naturally infected animals in semi-wild conditions and consideration of simian T-lymphotropic virus (STLV) status in addition to SIVmnd-1 infection. We found that SIVmnd-1 infection was associated with a significant and progressive loss of memory CD4(+) T-cells. Limited but significant increases in markers of immune activation in the T-cell populations, significant increases in plasma neopterin and changes to B-cell subsets were also observed in SIV-infected animals. However, no increase in plasma soluble CD14 was observed. Histological examination of peripheral lymph nodes suggested that SIVmnd-1 infection was not associated with a significant disruption of the lymph node architecture. Whilst this species has evolved numerous strategies to resist the development of AIDS, significant effects of SIV infection could be observed when examined in a natural environment. STLVmnd-1 infection also had significant effects on some markers relevant to understanding SIV infection and thus should be considered in studies of SIV infection of African primates where present.

A novel small animal model to study the replication of simian foamy virus in vivo.

Preclinical evaluation in a small animal model would help the development of gene therapies and vaccines based on foamy virus vectors. The establishment of persistent, non-pathogenic infection with the prototype foamy virus in mice and rabbits has been described previously. To extend this spectrum of available animal models, hamsters were inoculated with infectious cell supernatant or bioballistically with a foamy virus plasmid. In addition, a novel foamy virus from a rhesus macaque was isolated and characterised genetically. Hamsters and mice were infected with this new SFVmac isolate to evaluate whether hamsters are also susceptible to infection. Both hamsters and mice developed humoral responses to either virus subtype. Virus integration and replication in different animal tissues were analysed by PCR and co-cultivation. The results strongly indicate establishment of a persistent infection in hamsters. These studies provide a further small animal model for studying FV-based vectors in addition to the established models.