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Sterilising immunity is a desired outcome for vaccination against human immunodeficiency virus (HIV) and has been observed in the macaque model using inactivated simian immunodeficiency virus (SIV). This protection was attributed to antibodies specific for cell proteins including human leucocyte antigens (HLA) class I and II incorporated into virions during vaccine and challenge virus preparation. We show here, using HLA bead arrays, that vaccinated macaques protected from virus challenge had higher serum antibody reactivity compared with non-protected animals. Moreover, reactivity was shown to be directed against HLA framework determinants. Previous studies failed to correlate serum antibody mediated virus neutralisation with protection and were confounded by cytotoxic effects. Using a virus entry assay based on TZM-bl cells we now report that, in the presence of complement, serum antibody titres that neutralise virus infectivity were higher in protected animals. We propose that complement-augmented virus neutralisation is a key factor in inducing sterilising immunity and may be difficult to achieve with HIV/SIV Env-based vaccines. Understanding how to overcome the apparent block of inactivated SIV vaccines to elicit anti-envelope protein antibodies that effectively engage the complement system could enable novel anti-HIV antibody vaccines that induce potent, virolytic serological response to be developed.

The detailed study of immune effector mechanisms in primate models of infectious disease has been limited by the inability to adoptively transfer lymphocytes from vaccinated animals into naïve immunocompetent recipients. Recent advances in our understanding of the Major Histocompatibility Complex diversity of Mauritian cynomolgus macaques enabled the establishment of a breeding program to generate Major Histocompatibility Complex (MHC)-identical animals. The current study utilised this resource to achieve an improved model of adoptive transfer of lymphocytes in macaques. The effect of route of transfusion on persistence kinetics of adoptively transferred lymphocytes was evaluated in an autologous transfer system. Results indicated that peripheral persistence kinetics were comparable following infusion by different routes, and that cells were detectable at equivalent levels in lymphoid tissues six weeks post-infusion. In a pilot-scale experiment, the persistence of adoptively transferred lymphocytes was compared in MHC-identical siblings and MHC-identical unrelated recipients. Lymphocytes transferred intra-peritoneally were detectable in the periphery within one hour of transfer and circulated at detectable levels in the periphery and lymph nodes for 10 days. Donor lymphocytes were detectable at higher levels in MHC-identical siblings compared with unrelated animals, however the total time of persistence did not differ. These results demonstrate a further refinement of the lymphocyte adoptive transfer system in Mauritian cynomolgus macaques and provide a foundation for hitherto impractical experiments to investigate mechanisms of cellular immunity in primate models of infectious disease.

Immunopathology during early simian retrovirus type 2 (SRV-2) infection is poorly characterized. Here, viral dynamics, immune response and disease progression in transiently- or persistently-infected cynomolgus macaques are assessed. Viral nucleic acids were detected in selected lymphoid tissues of both persistently- and transiently-infected macaques, even after viral clearance from the periphery. Immunohistochemical staining of lymphoid tissues revealed alterations in a number of immune cell populations in both transiently- and persistently-infected macaques. The precise pattern depended upon the infection status of the macaque and the marker studied. Gross immunopathological changes in lymphoid tissues were similar between SRV infection and those observed for other simian retroviruses SIV and STLV, suggesting a common immunopathological response to infection with these agents., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Background: Live attenuated simian immunodeficiency virus (SIV) vaccines represent the most effective means of vaccinating macaques against pathogenic SIV challenge. However, thus far, protection has been demonstrated to be more effective against homologous than heterologous strains. Immune correlates of vaccine-induced protection have also been difficult to identify, particularly those measurable in the peripheral circulation., Methodology/principal Findings: Here we describe potent protection in 6 out of 8 Mauritian-derived cynomolgus macaques (MCM) against heterologous virus challenge with the pathogenic, uncloned SIVsmE660 viral stock following vaccination with live attenuated SIVmac251/C8. MCM provided a characterised host genetic background with limited Major Histocompatibility Complex (MHC) and TRIM5α allelic diversity. Early protection, observed as soon as 3 weeks post-vaccination, was comparable to that of 20 weeks vaccination. Recrudescence of vaccine virus was most pronounced in breakthrough cases where simultaneous identification of vaccine and challenge viruses by virus-specific PCR was indicative of active co-infection. Persistence of the vaccine virus in a range of lymphoid tissues was typified by a consistent level of SIV RNA positive cells in protected vaccinates. However, no association between MHC class I/II haplotype or TRIM5α polymorphism and study outcome was identified., Conclusion/significance: This SIV vaccine study, conducted in MHC-characterised MCM, demonstrated potent protection against the pathogenic, heterologous SIVsmE660 challenge stock after only 3 weeks vaccination. This level of protection against this viral stock by intravenous challenge has not been hitherto observed. The mechanism(s) of protection by vaccination with live attenuated SIV must account for the heterologous and early protection data described in this study, including those which relate to the innate immune system.

The restricted major histocompatibilty complex of Mauritian cynomolgus macaques confers exceptional potential on this species in human immunodeficiency virus (HIV) vaccine development. However, knowledge of the effects of Mhc genetics on commonly used simian immunodeficiency virus (SIV) and simian/human immunodeficiency virus (SHIV) stocks is incomplete. We determined the effect of Mhc haplotypes on SHIVsbg replication kinetics in a cohort of 25 naïve cynomolgus macaques. Haplotype M3 was associated with a 1.58log(10) reduction in viraemia at day 28 post infection (p.i.). Haplotype M6 was associated with elevated SHIVsbg viraemia at days 28 and 56. No significant effect of Mhc class II haplotypes on viral replication was observed. These data emphasise the importance of genetic characterisation of experimental macaques and advance our understanding of host genetic effects in SIV/SHIV models of HIV infection.

Background: Prevalence of simian retrovirus-2 (SRV-2) and simian T lymphotropic virus type I (STLV-I), was unknown in 337 captive cynomolgus macaques., Methods and Results: Molecular assays identified 29% of animals as SRV-2 mono-infected, 4% of animals as STLV-I mono-infected and 9% of animals as dual-infected. Of 108 juvenile animals, 83% were SRV-2-negative and no juvenile animal was STLV-I-positive. A subsequent study of juvenile macaques over a period of 2.5 years detected no STLV-I and 10 SRV-2 infections, six of which occurred between testing and day of colony formation. The study also highlighted that an anti-SRV-2 serological response does not presuppose infection. Tissue reservoirs of latent SRV-2 were not identified in suspected SRV-2 infections., Conclusions: Low transmissibility of the viruses present in the parental cohort and improved knowledge of the host response to SRV-2 has facilitated the creation of specific-retrovirus-free colonies of cynomolgus macaques.

Background: Mauritian cynomolgus macaques have greatly restricted genetic diversity in the MHC region compared to other non-human primates; however, the frequency of common MHC haplotypes among captive-bred populations has not been reported., Methods: Microsatellite PCR was used to determine MHC haplotype frequencies among captive macaques at a UK breeding facility. Allele-specific PCR and reference strand conformational analysis were used to determine the allele expression profile of a subset of animals., Results: Haplotypes H3 (21%) and H1 (19%) were most common in the captive population of Mauritian cynomolgus macaques. Predicted alleles were detected by allele-specific PCR-SSP in 98% of animals. Allele expression profiles were similar in animals with identical haplotypes., Conclusions: Mauritian cynomolgus macaques in the UK breeding facility have restricted MHC diversity comparable to a previously described population. Microsatellite-derived haplotypes are highly predictive of allele expression. A selective breeding program has been established to produce MHC-identical animals for biomedical research.

Simian retrovirus type 2 (SRV-2) is a natural pathogen of Macaca fascicularis. Although SRV-2 may be endemic in macaque colonies, it is not necessarily detected in all individuals suggesting differential susceptibility to SRV-2; factors contributing to this susceptibility are not fully understood. We have investigated the role of host genetic origin on virus susceptibility. We have shown that high levels of anti-SRV-2 antibodies correlate with failure to establish persistent virus infection, thus we targeted our genetic analysis of virus susceptibility with an investigation of the role of the polymorphic macaque major histocompatibility complex (MHC) class II locus. DRB genotypes, both novel and previously characterised, were identified in individuals and family groups. A discordance with SRV-2 infection status suggests that an Mhc II DRB genotype is not overtly associated with the outcome of viral infection.

Background: A new challenge stock of the simian immunodeficiency virus SIVmacJ5 has been produced following passage in vivo., Methods: SIVmacJ5 3/92 (J5M), was passaged serially through cynomolgus macaques (Macaca fascicularis) by intravenous inoculation of infected spleen cells isolated and prepared 14 days post-infection. Two challenge stocks, SIVmacJ5 S61MLN and SIVmacJ5 S62spl, were prepared by culture of lymphoid tissue ex vivo., Results: These virus stocks appeared better adapted for replication in M. fascicularis as demonstrated by a greater persistence of recoverable live virus from the periphery and increased pathology in lymphoid tissues 20 weeks post-challenge as detected by immunohistochemistry. Sequence analysis of the envelope gene from these stocks did not identify marked diversification of sequence as a result of this procedure., Conclusions: These stocks display more robust peripheral persistence and tissue pathology in cynomolgus macaques and should prove valuable analysing recombinant vaccines based upon SIVmacJ5 transgenes.

Background: The immunogenicity and protective efficacy of recombinant modified vaccinia virus Ankara (rMVA) vectors expressing structural (gag/pol, env) and regulatory (tat, rev, nef) genes of SIVmac251/32H-J5 (rMVA-J5) were assessed., Methods: Immunization with rMVA constructs (2.5 x 10(7) IU) 32, 20 and 8 weeks pre-challenge was compared with 32 and 20 weeks but with a final boost 8 weeks pre-challenge with 2 x 10(6) fixed-inactivated HSC-F4 cells infected with SIVmac32H. Controls received rMVA vectors expressing an irrelevant transgene or were naïve challenge controls. All received 10 MID(50) SIVmac32H/J5 intravenously., Results: Vaccinates immunized with rMVA-J5 exhibited significant, albeit transient, control of peak primary viraemia despite inconsistent and variable immune responses elicted by vaccination. Humoral and cellular responses to Env were most consistent, with lower responses to Nef, Rev and Tat. Increasing titres of anti-vaccinia neutralizing antibodies reflected the number and dose of rMVA inoculations., Conclusions: Improved combinations of viral vectors are required to elicit appropriate immune responses to control viral replication.

Cynomolgus macaques are frequently used in biomedical research. However, in contrast to their closest relative, the rhesus macaque, little is known about their Mhc genes except for the DQB1 locus. In this study, 33 DRB-sequences belonging to 17 allelic lineages were detected in a total of 68 macaques, 58 originating from Mauritius and 10 from China. The majority of the sequences were detected in the few macaques from China, confirming the low degree of genetic variation in macaques from Mauritius. In summary, the DRB region in cynomolgus macaques is polymorphic. The sequences belong in general to the same allelic lineages as in their closest relative, the rhesus macaque. Two exon 2 DNA sequences were identical in both species and may represent a trans-species origin. In addition, protein sequences of members of the DRB*W1 lineage seem to be rather conserved in the three macaque species examined so far. Six DRB-haplotypes were detected in the macaques from Mauritius. While single DRB-alleles or some protein sequences seemed to be conserved among macaque species, we could not detect any evidence for a trans-species conservation of a complete DRB region. Overall, the data indicate that reorganization of the DRB region by recombination is a major force in creating diversity in cynomolgus macaques as it is in rhesus macaques., (Copyright 2004 Blackwell Munksgaard)

Various simian immunodeficiency virus (SIV)sm/mac and simian/human immunodeficiency virus (SHIV) strains are used in different macaque species to study AIDS pathogenesis, as well as to evaluate candidate vaccine and anti-retroviral drugs efficacy. In this study we investigated the effect of route of infection, species of macaques and nature of virus stock on early plasma viral RNA load. We monitored the plasma RNA concentrations of 63 rhesus (Macaca mulatta) and cynomolgus macaques (Macaca fascicularis) infected with well-characterised virus stocks administered either by oral, rectal, vaginal or intravenous (i.v.) routes. In SIV(mac)-infected macaques, no significant difference in plasma RNA loads was observed between the rectal, oral and i.v. routes of infection. Cynomolgus macaques developed lower steady state SIV plasma RNA concentrations compared with rhesus macaques and no significant difference was observed between rectal and i.v. routes of infection. In SHIV(89.6p)-infected macaques, no difference between species or between route of infection was observed with this particular chimeric virus.

Two cynomolgus macaques were infected with a complex, but characterized, challenge stock of simian immunodeficiency virus (SIVmac251 32H). The polymerase chain reaction was applied in a temporal sequence analysis to determine the sequences of the gp120 region of the SIV env gene, which were present in the blood of both macaques at 1, 6, and 15 months postinfection (p.i.). At 1 month p.i. selected sequences, which had been present in the original virus challenge stock, were reisolated. At later times, new sequences emerged, which had not been detected in the original virus challenge stock. Changes in sequence were restricted to specific regions of gp120, notably those equivalent to V1, V2, V4, and V5 of HIV-1, but not V3. The diversity and the rate of appearance of new sequences in the V1 region suggest that genetic evolution occurs by mechanisms in addition to nucleotide substitutions. These results are discussed in relation to the role of the envelope protein in the generation of protective immunity against infection with immunodeficiency viruses.

Cynomolgus macaques are frequently used in biomedical research. However, in contrast to their closest relative, the rhesus macaque, little is known about their Mhc genes except for the DQB1 locus. In this study, 33 DRB-sequences belonging to 17 allelic lineages were detected in a total of 68 macaques, 58 originating from Mauritius and 10 from China. The majority of the sequences were detected in the few macaques from China, confirming the low degree of genetic variation in macaques from Mauritius. In summary, the DRB region in cynomolgus macaques is polymorphic. The sequences belong in general to the same allelic lineages as in their closest relative, the rhesus macaque. Two exon 2 DNA sequences were identical in both species and may represent a trans-species origin. In addition, protein sequences of members of the DRB*W1 lineage seem to be rather conserved in the three macaque species examined so far. Six DRB-haplotypes were detected in the macaques from Mauritius. While single DRB-alleles or some protein sequences seemed to be conserved among macaque species, we could not detect any evidence for a trans-species conservation of a complete DRB region. Overall, the data indicate that reorganization of the DRB region by recombination is a major force in creating diversity in cynomolgus macaques as it is in rhesus macaques. [ABSTRACT FROM AUTHOR]