CD8+ cytotoxic T lymphocytes of a cynomolgus macaque infected with simian immunodeficiency virus (SIV) mac32H-J5 recognize a nine amino acid epitope in SIV Gag p26

Transcriptionally abundant major histocompatibility complex class I alleles are fundamental to nonhuman primate simian immunodeficiency virus-specific CD8+ T cell responses

Simian immunodeficiency virus (SIV)-infected macaques are the preferred animal model for human immunodeficiency virus (HIV) vaccines that elicit CD8(+) T cell responses. Unlike humans, whose CD8(+) T cell responses are restricted by a maximum of six HLA class I alleles, macaques express up to 20 distinct major histocompatibility complex class I (MHC-I) sequences. Interestingly, only a subset of macaque MHC-I sequences are transcriptionally abundant in peripheral blood lymphocytes. We hypothesized that highly transcribed MHC-I sequences are principally responsible for restricting SIV-specific CD8(+) T cell responses. To examine this hypothesis, we measured SIV-specific CD8(+) T cell responses in MHC-I homozygous Mauritian cynomolgus macaques. Each of eight CD8(+) T cell responses defined by full-proteome gamma interferon (IFN-γ) enzyme-linked immunospot (ELISPOT) assay were restricted by four of the five transcripts that are transcriptionally abundant (>1% of total MHC-I transcripts in peripheral blood lymphocytes). The five transcriptionally rare transcripts shared by these animals did not restrict any detectable CD8(+) T cell responses. Further, seven CD8(+) T cell responses were defined by identifying peptide binding motifs of the three most frequent MHC-I transcripts on the M3 haplotype. Combined, these results suggest that transcriptionally abundant MHC-I transcripts are principally responsible for restricting SIV-specific CD8(+) T cell responses. Thus, only a subset of the thousands of known MHC-I alleles in macaques should be prioritized for CD8(+) T cell epitope characterization.

MHC class I characterization of Indonesian cynomolgus macaques

Cynomolgus macaques (Macaca fascicularis) are quickly becoming a useful model for infectious disease and transplantation research. Even though cynomolgus macaques from different geographic regions are used for these studies, there has been limited characterization of full-length major histocompatibility complex (MHC) class I immunogenetics of distinct geographic populations. Here, we identified 48 MHC class I cDNA nucleotide sequences in eleven Indonesian cynomolgus macaques, including 41 novel Mafa-A and Mafa-B sequences. We found seven MHC class I sequences in Indonesian macaques that were identical to MHC class I sequences identified in Malaysian or Mauritian macaques. Sharing of nucleotide sequences between these geographically distinct populations is also consistent with the hypothesis that Indonesia was a source of the Mauritian macaque population. In addition, we found that the Indonesian cDNA sequence Mafa-B*7601 is identical throughout its peptide binding domain to Mamu-B*03, an allele that has been associated with control of Simian immunodeficiency virus (SIV) viremia in Indian rhesus macaques. Overall, a better understanding of the MHC class I alleles present in Indonesian cynomolgus macaques improves their value as a model for disease research, and it better defines the biogeography of cynomolgus macaques throughout Southeast Asia.

Identification of a cytotoxic T-lymphocyte (CTL) epitope recognized by Gag-specific CTLs in cynomolgus monkeys infected with simian/human immunodeficiency virus

Infection of Macaca fascicularis (cynomolgus monkey) with chimeric simian/human immunodeficiency virus (SHIV) provides a valuable experimental animal model of AIDS and is widely used for the development of human immunodeficiency virus vaccine strategies. In these settings, analysis of CD8(+) T-cell responses during infection represents one of the key parameters for monitoring the evaluation of containment of virus replication. The generation of Gag-specific CD8(+) T cells was reported previously from a cynomolgus monkey infected with SHIV89.6P by taking advantage of a B-lymphoblastoid cell line transduced with a retroviral vector expressing simian immunodeficiency virus (SIV) Gag. Here, it was shown that these cytotoxic T lymphocytes (CTLs) demonstrated specificity for a single 9 aa peptide (NCVGDHQAA) spanning aa 192-200 of the SIVmac239 p55(gag) protein. Furthermore, a positive response was found against the same epitope in one of six other SHIV-infected monkeys. This newly identified SIV Gag CTL epitope in SHIV-infected cynomolgus monkeys will be a useful tool for monitoring and evaluating Gag-specific immune responses during vaccination and infection in the cynomolgus monkey model of AIDS.

Chinese rhesus and cynomolgus macaques in HIV vaccine and pathogenesis research

The development of an effective, prophylactic vaccine for HIV is a public health priority. Nonhuman primate models of AIDS are an instrumental component of HIV vaccine and pathogenesis research. Rhesus macaques of Indian origin are by far the most widely used species in vaccine research. The demand for these animals is intense, threatening their future availability. Do other macaques, such as non-Indian rhesus macaques and cynomolgus macaques, represent a viable alternative? In this perspective, the potential advantages and pitfalls of performing HIV vaccine research in non-Indian rhesus or cynomolgus macaques is examined.

Detection of simian immunodeficiency virus (SIV)-specific T-cell-mediated cytotoxicity in the peripheral blood from infected cynomolgus monkeys

We have previously demonstrated that peptide immunization restimulates the memory CD4 T-cell response, but fails to induce cytotoxic T lymphocyte (CTL) in cynomolgus macaques. To examine the nature of protective immunity to simian immunodeficiency virus (SIV) in this study, freshly isolated peripheral blood mononuclear cells (PBMC) from four infected juvenile cynomolgus macaques and from three uninfected control macaques were assessed for CTL activity monthly for 9 consecutive months, beginning 1 month after detection of infection. Target cells consisted of major histocompatibility (MHC) haploidentical parental PBMC which were stimulated with mitogen and then pulsed with heat-killed SIVcyn. CTL activity was demonstrated in PBMCs from all four infected animals. The effector cells are T cells which mediate cytotoxicity against SIVcyn-pulsed target cells in an MHC-restricted manner. Furthermore, the cytotoxicity is virus specific and predominantly, if not exclusively, mediated by CD8+ T cells; it is also MHC class I restricted. Incubation of target cells with pepstatin A during antigen pulsing prior to the cytotoxic assay inhibited target cell generation, suggesting that viral antigens are processed via an endocytic pathway.

Simian immunodeficiency virus as a model of human HIV disease

Because of strong clinical, pathological, virological and immunological analogies with HIV infection of humans, infection of macaques with SIV provides a valuable model for exploring crucial issues related to both the pathogenesis and prevention of HIV infection. The model has offered a unique setting for the preclinical evaluation of drugs, vaccines and gene-therapies against HIV, and has helped to identify many virus and host determinants of lentiviral disease. For instance, the importance of an intact nef gene for efficient lentivirus replication and disease induction, and the protective ability of live attenuated, nef-deleted viruses have been first demonstrated in macaques using molecular clones of SIV. More recently, the development of chimeric HIV-SIV vectors able to establish infection and induce disease in macaques has provided new opportunities for the evaluation of vaccination strategies based upon HIV antigens. The aim of this review is to describe the natural course of SIV infection in macaques and to outline how this model has contributed to our understanding of the complex interaction between lentiviruses and host immune system.

Peptide immunization restimulates the memory CD4 T cell response but fails to induce cytotoxic T lymphocytes in cynomolgus monkeys

A potential strategy to induce peptide specific CTL in vivo was investigated. A synthetic vaccine consisting of an SIV-derived, HLA-A2. 1-binding CTL epitope and a tetanus toxin-derived T helper epitope was evaluated for its capacity to induce peptide-specific CTL in monkeys. Thirteen animals were immunized and boosted twice with 150 microg of CTL plus 250 microg of the T helper peptide (p30). Peripheral blood mononuclear cells (PBMC) were regularly analysed for cytotoxic and proliferative responses before, between, and after the immunizations, and the serum was tested for anti-peptide antibodies. No unequivocal induction of SIV peptide-specific CTL in any of the monkeys was observed. However, a wide pattern of mild and transient side reactions were observed, ranging from local redness at the injection site to generalized exanthema, myalgias, arthralgias, and fever. The side-effects were related to the T helper epitope, as they were similar to the side-effects experienced after tetanus immunization, correlated to the magnitude of the p30-specific in vitro proliferative response, and occurred only if p30 was co-injected. No antibody against the SIV-derived peptides nor against p30 was detectable in the serum after repeated immunizations. The data suggest that the CTL peptide, at the concentration used in this study, failed to induce a cytotoxic immune response in vivo, although the T helper peptide seems to be capable of restimulating the specific memory T cells.