Enhanced infectivity of an R5-tropic simian/human immunodeficiency virus carrying human immunodeficiency virus type 1 subtype C envelope after serial passages in pig-tailed macaques (Macaca nemestrina)

Molecular cloning and in vitro evaluation of an infectious simian-human immunodeficiency virus containing env of a primary Chinese HIV-1 subtype C isolate

Human immunodeficiency virus (HIV) clade C is the most prevalent subtype and accounts for approximately 50% of all HIV infections worldwide. In China, the prevalent HIV strains are B'/C subtypes, in which the envelope belongs to subtype C. To evaluate potential AIDS vaccines targeting Chinese viral strains in non-human primate models, we constructed an infectious simian-human immunodeficiency virus (SHIV) that expresses most of the envelope of a primary HIV strain, which was isolated from a HIV-positive intravenous drug user from XinJiang province in China. The resulting chimeric SHIV-XJ02170 was infectious in human, rhesus monkey and cynomolgus monkey peripheral blood mononuclear cells (PBMC) and used CCR5 exclusively as coreceptor.

Divergent host responses during primary simian immunodeficiency virus SIVsm infection of natural sooty mangabey and nonnatural rhesus macaque hosts

To understand how natural sooty mangabey hosts avoid AIDS despite high levels of simian immunodeficiency virus (SIV) SIVsm replication, we inoculated mangabeys and nonnatural rhesus macaque hosts with an identical inoculum of uncloned SIVsm. The unpassaged virus established infection with high-level viral replication in both macaques and mangabeys. A species-specific, divergent immune response to SIV was evident from the first days of infection and maintained in the chronic phase, with macaques showing immediate and persistent T-cell proliferation, whereas mangabeys displayed little T-cell proliferation, suggesting subdued cellular immune responses to SIV. Importantly, only macaques developed (CD4+)-T-cell depletion and AIDS, thus indicating that in mangabeys limited immune activation is a key mechanism to avoid immunodeficiency despite high levels of SIVsm replication. These studies demonstrate that it is the host response to infection, rather than properties inherent to the virus itself, that causes immunodeficiency in SIV-infected nonhuman primates.

Inhibition of pathogenic SHIV replication in macaques treated with antisense DNA of interleukin-4

Interleukin-4 is implicated in the pathogenesis of HIV-induced AIDS and causes enhancement of replication of virus strains that use the CXCR4 (X4) coreceptor. In this study, we explored the effects of interleukin-4 (IL-4) antisense (AS) DNA on replication of X4, simian human immunodeficiency viruses, SHIV(KU-2) and SHIV89.6P. AS IL-4 oligomer caused inhibition of virus replication in cultures of CD4+ T cells and macrophages derived from macaques. Plasmid expressing AS IL-4 DNA was also effective in abrogating virus replication in macrophage cultures. Relevance of these cell culture studies was confirmed in vivo by treating SHIV89.6P-infected macaques with AS IL-4 DNA. Six macaques were inoculated with the virus, and 4 were treated with AS IL-4 DNA. This resulted in a significant decrease in viral RNA concentrations in the liver, lungs, and spleen tissues that are all sites of virus replication in macrophages. This is the first demonstration of effective inhibition of an HIV-like virus in tissues by AS DNA of a cytokine. In the present era of increasing resistance of HIV to antiviral compounds, exploration of adjunct therapies directed at host responses in combination with antiretroviral drugs may be of value for the treatment of AIDS.

Neuronal apoptosis is mediated by CXCL10 overexpression in simian human immunodeficiency virus encephalitis

Inflammatory mediators play a crucial role in the pathophysiology of several neurodegenerative diseases including acquired immune deficiency syndrome dementia complex. In the present study we identified a link between CXCL10 overexpression in the brain and human immunodeficiency virus dementia and demonstrated the presence of the chemokine CXCL10 and its receptor, CXCR3, in the neurons in the brains of macaques with simian human immunodeficiency virus encephalitis. Using human fetal brain cultures, we showed that treatment of these cells with either SHIV89.6P or viral gp120 resulted in induction of CXCL10 in neurons. Cultured neurons treated with the chemokine developed increased membrane permeability followed by apoptosis via activation of caspase-3. We confirmed the relevance of these findings in sections of human and macaque brains with encephalopathy demonstrating that neurons expressing CXCL10 also expressed caspase-3.

HIV-1 subtype distribution and the problem of drug resistance

Genetic diversity is a hallmark of HIV-1 infection with regard to the expansion of distinct viral subtypes (clades A, B, C, D, E, F, G, K, and O) in different geographical regions. Here, we discuss the issues of HIV-1 sensitivity to antiretroviral drugs and drug resistance in the context of HIV-1 subtype diversity. Virtually all available evidence suggests that all subtypes of HIV display similar sensitivity to antiviral drugs, but viruses from some subtypes or geographical regions may occasionally have a greater propensity to develop resistance against certain drugs than other viral variants. In some situations, the types of mutations associated with resistance may vary, as a result of subtle differences among subtypes with regard to the genetic code. This consideration notwithstanding, drug resistance is unlikely to become a more serious issue in developing than developed countries, and there is an urgency to make anti-HIV drugs available to all who are in need.

Rapid CD4+ T-lymphocyte depletion in rhesus monkeys infected with a simian-human immunodeficiency virus expressing the envelope glycoproteins of a primary dual-tropic Ethiopian Clade C HIV type 1 isolate

Simian-human immunodeficiency virus (SHIV) chimerae with the envelope glycoproteins of X4 or R5/X4 HIV-1 isolates from clade B can cause rapid and severe CD4(+) T cell depletion and AIDS-like illness in infected monkeys. We created a SHIV (SHIV-MCGP1.3) expressing the envelope glycoproteins of a primary R5/X4, clade C HIV-1 isolate. Infection of a rhesus monkey with SHIV-MCGP1.3 resulted in a low level of viremia and no significant alteration in CD4(+) T-lymphocyte counts. However, serial intravenous passage of the virus resulted in the emergence of SHIV-MCGP1.3 variants that replicated efficiently and caused profound CD4(+) T cell depletion during the acute phase of infection. The CD4(+) T cell counts in the infected monkeys gradually returned to normal, and the animals remained healthy. The ability to cause rapid and profound loss of CD4(+) T lymphocytes in vivo is a property shared by passaged, CXCR4-using SHIVs, irrespective of the clade of origin of the HIV-1 envelope glycoproteins.

HIV-1 subtype B' dictates the AIDS epidemic among paid blood donors in the Henan and Hubei provinces of China

OBJECTIVE

To investigate the genetic background of HIV-1 strains among infected paid blood donors (PBD) in the Henan and Hubei provinces of China.

METHODS

The polymerase chain reaction was used to amplify HIV-1 gag p17 fragments and some 5'-half or full-length viral genomes from peripheral blood mononuclear cells. The HIV-1 sequences obtained were analysed using phylogenetic and recombinant approaches.

RESULTS

Among the total of 62 samples studied, 59 (95.2%) came from PBD. Of those 59 PBD, 45 were collected from 14 different geographical locations in Henan, whereas the remaining 14 were from five locations in Hubei. A total of 62 HIV-1 gag p17 fragments, three 5'-half and one full HIV-1 genome sequences were obtained. Phylogenetic analysis of these sequences suggests that PBD from Henan and Hubei, despite being geographically distant, harbored a group of genetically closely related HIV-1 B' strains. No recombinant forms have been detected in this cohort.

CONCLUSION

Our data indicate that the AIDS epidemic among PBD in Henan and Hubei is caused largely by HIV-1 subtype B', which contrasts greatly with the CB' recombinant strains CRF-07 and CRF-08 currently dominating among the drug abusers in other regions of China. Our report has revealed the first complete genome background of the most dominant circulating HIV-1 strain in Henan and Hubei, which is essential for the design and development of an effective AIDS vaccine for the region.

Characterization of a simian human immunodeficiency virus encoding the envelope gene from the CCR5-tropic HIV-1 Ba-L

The tat, rev, vpu, and env genes from the monocytotropic CCR5-dependent HIV-1 Ba-L isolate were substituted for homologous simian immunodeficiency virus (SIV) sequences in the SIV genome. The resultant SHIV (SHIV Ba-L) replicated in CCR5-positive PM-1 cells but not in CCR5-negative CEMX174 cells. Infection of HOS cells expressing different co-receptors showed SHIV Ba-L to be strictly CCR5-dependent. Infection of PM-1 cells and rhesus peripheral blood mononuclear cells (PBMCs) was highly sensitive to RANTES but not to SDF-1. Although SHIV Ba-L infected rhesus and pigtail macaques intravenously or rectally, plasma viremia was controlled after 3 weeks. After serial passage through 4 pigtails by blood and bone marrow transfer, virus from pigtail PBMCs had higher in vitro infectious titers on rhesus PBMCs and was efficiently transmitted vaginally in rhesus and cynomolgus macaques. Plasma viremia generally persisted longer than after infection with unpassaged virus but was eventually controlled with no significant decrease in CD4+ T-cell counts in peripheral blood. The envelope gene of SHIV Ba-L revealed a very little genetic drift during in vivo passage. SHIV Ba-L provides a potentially useful model for R5 HIV-1 infection of humans.

Infection of a chimeric simian and human immunodeficiency virus with CCR5-specific HIV-1 envelope to Rhesus macaques

Human immunodeficiency virus (HIV) infects lymphocytes and macrophages via CD4 and chemokine receptors. In this study, the infectivity of a chimeric simian and human immunodeficiency virus (SHIV) having a CCR5-specific HIV-1 envelope gene was examined. A SHIV strain termed SHIV-JRFL could enter cells via CD4 with a chemokine receptor CCR5, not CXCR4, and the viral replication was suppressed by recombinant human RANTES, one of beta-chemokines. The intravenous inoculation of SHIV-JRFL into two rhesus macaques resulted in a systemic infection, though it was rather weak. During the early infection, the production of RANTES from Con A-stimulated PBMCs of the infected monkeys increased. These results suggested that beta-chemokine has the potential to limit the infectivity of an R5-type SHIV.

Comparing the ex vivo fitness of CCR5-tropic human immunodeficiency virus type 1 isolates of subtypes B and C

Continual human immunodeficiency virus type 1 (HIV-1) evolution and expansion within the human population have led to unequal distribution of HIV-1 group M subtypes. In particular, recent outgrowth of subtype C in southern Africa, India, and China has fueled speculation that subtype C isolates may be more fit in vivo. In this study, nine subtype B and six subtype C HIV-1 isolates were added to peripheral blood mononuclear cell cultures for a complete pairwise competition experiment. All subtype C HIV-1 isolates were less fit than subtype B isolates (P < 0.0001), but intrasubtype variations in HIV-1 fitness were not significant. Increased fitness of subtype B over subtype C was also observed in primary CD4(+) T cells and macrophages from different human donors but not in skin-derived human Langerhans cells. Detailed analysis of the retroviral life cycle during several B and C virus competitions indicated that the efficiency of host cell entry may have a significant impact on relative fitness. Furthermore, phyletic analyses of fitness differences suggested that, for a recombined subtype B/C HIV-1 isolate, higher fitness mapped to the subtype B env gene rather than the subtype C gag and pol genes. These results suggest that subtype B and C HIV-1 may be transmitted with equal efficiency (Langerhans cell data) but that subtype C isolates may be less fit following initial infection (T-cell and macrophage data) and may lead to slower disease progression.

Species tropism of chimeric SHIV clones containing HIV-1 subtype-A and subtype-E envelope genes

To analyze HIV-1 genes in a nonhuman primate model for lentivirus infection and AIDS, recombinant SIV/HIV-1 (SHIV) clones were constructed from two HIV-1 subtype-A isolates (HIV-1(SF170) and HIV-1(Q23-17) from individuals in Africa) and two HIV-1 subtype-E isolates (HIV-1(9466) and HIV-1(CAR402) from AIDS patients in Thailand and Africa), respectively. These four SHIV clones, designated SHIV-A-170, SHIV-A-Q23, SHIV-9466.33, and SHIV-E-CAR, contain envelope (env) genes from the subtype-A or -E viruses. Interestingly, SHIV-A-170, SHIV-A-Q23, and SHIV-9466.33 were restricted for replication in cultures of macaque lymphoid cells, whereas SHIV-E-CAR replicated efficiently in these cells. Additional studies to define the block to replication in macaque cells were focused on the subtype-E clone SHIV-9466.33. A SHIV intragenic env clone, containing sequence-encompassing V1/V2 regions of HIV-1(CAR402) and V3/V4/V5 regions of SHIV-9466.33, infected and replicated in macaque lymphoid cells. These results indicated that the sequence-encompassing V1/V2 region of HIV-1(9466) was responsible for the block of the SHIV-9466.33 replication in macaque cells. Analysis of viral DNA in acutely infected macaque cells revealed that SHIV-9466.33 was blocked at a step at/or before viral DNA synthesis, presumably during the process of virion entry into cells. In a fluorescence-based cell-cell fusion assay, fusion pore formation readily took place in cocultures of cells expressing the SHIV-9466.33 env glycoprotein with macaque T-lymphoid cells. Taken together, these results demonstrated that the block of SHIV-9466.33 replication in macaque cells is at an early step after fusion pore formation but before reverse transcription.

CD4+ lymphocytopenia in acute infection of Asian macaques by a vaginally transmissible subtype-C, CCR5-tropic Simian/Human Immunodeficiency Virus (SHIV)

An R5-tropic SHIV(CHN19P4) was previously generated using a primary HIV-1 subtype-C envelope. We have further characterized this SHIV in two species of macaques. To determine whether this isolate is transmissible vaginally, female pig-tailed macaques were inoculated with 2 x 10(3) TCID50 of SHIV(CHN19P4) by the vaginal route. Animals became infected with a high peak plasma viremia (>10(7) viral copies/mL) and rapid seroconversion. The viremia was accompanied by CD4+ lymphocytopenia in the gut lamina propria lymphocyte (LPL) population. Comparable CD4+ T-cell loss was not seen in peripheral blood and colonic lymph nodes. These findings demonstrate a unique R5-tropic SHIV that can be used to study envelope-related issues in vaginal transmission of the most prevalent subtype of HIV-1. We also found that rhesus macaques intravenously inoculated with 1 x 10(3) TCID50 of SHIV(CHN19P4) became infected and showed CD4+ lymphocytopenia in the gut LPL population. Despite inactivation of the vpu gene in SHIV(CHN19P4), the virus appears to target mainly gut-associated lymphoid tissues during the initial stage of infection as has been described for SHIV(SF162P), another R5-tropic (subtype B) recombinant virus. Our data indicate that the R5-mediated CD4+ lymphocytopenia in the gut is likely independent of HIV-1 genotypes and of the function of vpu at the acute phase of viral infection.

Properties of the surface envelope glycoprotein associated with virulence of simian-human immunodeficiency virus SHIV(SF33A) molecular clones

In vivo adaptation of simian-human immunodeficiency virus (SHIV) clone SHIV(SF33) resulted in the emergence of pathogenic isolate SHIV(SF33A), which caused a rapid and severe CD4(+) T-cell depletion when inoculated into rhesus macaques. Two molecular clones generated by inserting the env V1-to-V5 region amplified from SHIV(SF33A)-infected animals into the parental SHIV(SF33) genome retained a pathogenic phenotype. The gp120 envelope glycoproteins of pathogenic clones SHIV(SF33A2) and SHIV(SF33A5) conferred a threefold increase in viral entry and fusogenicity compared to the parental glycoprotein. Changes in gp120 were also responsible for a higher replication capacity and cytopathicity in primary CD4(+) T-cell cultures. Last, gp120 carried the determinants of SHIV(SF33A) neutralization resistance. Thus, changes in SHIV(SF33A) gp120 produced a set of properties that could account for the pathogenic phenotype observed in vivo. Measurement of antibody binding to SHIV(SF33A) viral particles revealed an increased exposure of the CD4-induced epitope recognized by the 17b monoclonal antibody in a region that was shown to contribute to coreceptor binding. Exposure of this epitope occurred in the absence of CD4 binding, suggesting that the envelope glycoprotein of pathogenic SHIV(SF33A) clones folded in a conformation that was primed for interaction with CXCR4 or for the subsequent step of fusion.

Infectious simian/human immunodeficiency virus with human immunodeficiency virus type 1 subtype C from an African isolate: rhesus macaque model

Human immunodeficiency virus type 1 (HIV-1) subtype C is responsible for more than 56% of all infections in the HIV and AIDS pandemic. It is the predominant subtype in the rapidly expanding epidemic in southern Africa. To develop a relevant model that would facilitate studies of transmission, pathogenesis, and vaccine development for this subtype, we generated SHIV(MJ4), a simian/human immunodeficiency virus (SHIV) chimera based on HIV-1 subtype C. SHIV(MJ4) contains the majority of env, the entire second exon of tat, and a partial sequence of the second exon of rev, all derived from a CCR5-tropic, primary isolate envelope clone from southern Africa. SHIV(MJ4) replicated efficiently in human, rhesus, and pig-tailed macaque peripheral blood mononuclear cells (PBMCs) in vitro but not in CEMx174 cells. To assess in vivo infectivity, SHIV(MJ4) was intravenously inoculated into four rhesus macaques (Macaca mulatta). All four animals became infected as determined through virus isolation, PCR analysis, and viral loads of 10(7) to 10(8) copies of viral RNA per ml of plasma during the primary infection phase. We have established a CCR5-tropic SHIV(MJ4)/rhesus macaque model that may be useful in the studies of HIV-1 subtype C immunology and biology and may also facilitate the evaluation of vaccines to control the spread of HIV-1 subtype C in southern Africa and elsewhere.

Using SHIVs to develop an anti-HIV-1 live-attenuated vaccine

The use of chimeric simian and human immunodeficiency viruses (SHIVs) that encode HIV-1 Env and are infectious to macaques has made it possible to analyze the pathogenicity of HIV-1 in vivo, and to evaluate the efficacy of candidate vaccines in macaques. In addition, we believe that gene-deleted SHIVs could potentially be used as anti-HIV-1 live-attenuated vaccines. Gene-deleted SHIVs replicate transiently, are non-pathogenic and induce strong protection against challenge infection. The most important advantage of gene-deleted SHIVs is that their efficacy and safety can be evaluated in macaques before they are used in humans.

Construction and analysis of an infectious human Immunodeficiency virus type 1 subtype C molecular clone

Human immunodeficiency virus type 1 (HIV-1) subtype C is now the predominant subtype in the global epidemic. This subtype is encountered in southern Africa and parts of Asia, where the epidemic is rapidly spreading. One possible explanation for these epidemiological observations is that this subtype has genetic characteristics that may contribute to its spread and/or pathogenic potential. In this report, we describe the construction of MJ4, an infectious chimeric molecular clone of HIV-1 subtype C that replicates in donor peripheral blood mononuclear cells and macrophages. We also tested this clone for its ability to use the chemokine receptors CCR1, CCR2b, CCR3, CXCR4, and CCR5 and found that the clone utilizes only CCR5 as the coreceptor for cell entry. The MJ4 clone will be useful in further biological and virological characterization of HIV-1 subtype C and will be an important tool in the continuing efforts to understand what may constitute protective immunity in HIV-1. The clone may also be used in experimental design of vaccine candidates that may be directed against HIV-1 subtype C.