Characterization of a novel simian immunodeficiency virus from guereza colobus monkeys (Colobus guereza) in Cameroon: a new lineage in the nonhuman primate lentivirus family.

Exploration of the diversity among primate lentiviruses is necessary to elucidate the origins and evolution of immunodeficiency viruses. During a serological survey in Cameroon, we screened 25 wild-born guereza colobus monkeys (Colobus guereza) and identified 7 with HIV/SIV cross-reactive antibodies. In this study, we describe a novel lentivirus, named SIVcol, prevalent in guereza colobus monkeys. Genetic analysis revealed that SIVcol was very distinct from all other known SIV/HIV isolates, with average amino acid identities of 40% for Gag, 50% for Pol, 28% for Env, and around 25% for proteins encoded by five other genes. Phylogenetic analyses confirmed that SIVcol is genetically distinct from other previously characterized primate lentiviruses and clusters independently, forming a novel lineage, the sixth in the current classification. Cercopithecidae monkeys (Old World monkeys) are subdivided into two subfamilies, the Colobinae and the Cercopithecinae, and, so far, all Cercopithecidae monkeys from which lentiviruses have been isolated belong to the Cercopithecinae subfamily. Therefore, SIVcol from guereza colobus monkeys (C. guereza) is the first primate lentivirus identified in the Colobinae subfamily and the divergence of SIVcol may reflect divergence of the host lineage.

Evidence for differences in MT2 cell tropism according to genetic subtypes of HIV-1: syncytium-inducing variants seem rare among subtype C HIV-1 viruses.

Non-syncytium-inducing (NSI) variants seem to be more readily transmitted than syncytium-inducing (SI) variants, and the switch from NSI to SI during HIV-1 infection seems to be a key determinant to the evolution of AIDS. We investigated eventual differences in the SI capacity on MT-2 cells according to genetic subtypes of HIV-1 and correlated this observations with CD4 counts and duration of HIV infection. In total, 86 patients, most with known date of HIV contamination and infected with different genetic subtypes, have been studied: 11 subtype A, 46 subtype B, 22 subtype C, and 7 subtype E. Multivariate analysis used a Cox's proportional hazards regression. The number and percentage of patients infected with an SI strain were as follows: 3 of 11 (27%) for subtype A, 15 of 46 (33%) for subtype B, 0 of 22 (0%) for subtype C, and 5 of 7 (71%) for subtype E. After adjustment for time after seroconversion and CD4 counts, significantly fewer SI variants were observed in patients infected with subtype C (p < .002) and it was found that subjects infected with subtype E had a higher risk of being infected with an SI strain (rate ratio [RR] = 12.39%; 95% confidence interval [CI] 1.55-98.67; p < .001). Most of the subtype E-infected patients from our study switched from an NSI to SI phenotype early after seroconversion (<4 years). To predict the in vitro presence of SI variants, we scanned V3-loop sequences for mutations at positions 11 and/or 25. Overall, 54 of 55 (98.2%) NSI strains in vitro were predicted NSI, and only 4 of 12 (33.3%) of SI viruses were predicted SI. For patients in whom a switch from an NSI to an SI virus was observed, the SI phenotype could be detected earlier in vitro than by the corresponding V3-loop sequence. No SI strains were observed among patients infected with subtype C; however, longer follow-up is needed to see whether the appearance of SI variants in subtype E or the absence of SI variants in subtype C-infected patients is also associated respectively with a faster or slower progression to AIDS as described for subtype B.

Different evolution of simian immunodeficiency virus in a natural host and a new host.

To address the mechanisms of host-virus adaptation and pathogenesis of lentiviral infections, we compared the evolution of the same isolate of simian immunodeficiency virus (SIVsmm9) in two different situations: nonpathogenic infection of its natural host, the sooty mangabey, and AIDS-inducing infection of a new host, the rhesus macaque. Samples were obtained at 6, 12, and 23 or 30 months postinfection from three animals of each species. Sequences were derived from the V1 and V2 domains of the surface glycoprotein. In the macaques, we observed specific variations absent from all mangabey samples, indicating that different host species select different virus variants. In the macaques, we also observed a different shape in the phylogenetic tree, a lower divergence of sibling sequences, and a lower synonymous/nonsynonymous change ratio than in the mangabeys. This suggests that the viral population is larger and submitted to weaker selection pressures when host-virus adaptation is achieved, such as in the mangabey.

Characterization of dual HIV-1 and HIV-2 serological profiles by polymerase chain reaction.

OBJECTIVE: To evaluate the frequency of dual HIV-1 and HIV-2 DNA sequences in patients with dual serological profiles. DESIGN: We tested 40 samples from AIDS patients living in Abidjan, Côte d'Ivoire. METHODS: Dual serological reactivity was determined by double Western blot and two enzyme-linked immunosorbent assays with recombinant proteins and synthetic peptides as antigens. The Western blot was considered to show dual reactivity when sera reacted with at least two glycoproteins and one core protein of each virus. HIV DNA sequences were detected by hybridization to radiolabelled probes of polymerase chain reaction (PCR) products amplified using specific primers. RESULTS: Both HIV-1 and HIV-2 DNA sequences were detected in four out of 11 samples with a dual serological profile and in four out of 24 samples with anti-HIV-1 antibodies only. CONCLUSION: These results show that dual HIV-1 and HIV-2 serological profiles are not always due to infection by both viruses, and emphasize the need for a combination of serological and PCR assays for the appraisal of these viral infections.

Presence of HIV-1 in human parenchymal and non-parenchymal liver cells in vivo.

The infection of liver cells by HIV-1 was investigated in vivo. Liver biopsies from 13 anti-HIV-1 antibody-positive patients were studied and HIV-1 DNA was revealed by polymerase chain reaction (PCR) in eight. In situ hybridization demonstrated the presence of HIV-1 RNA in all eight PCR-positive liver specimens. Mononuclear inflammatory cells in the portal tracts and Kupffer cells were labeled by a HIV-1 35S-RNA probe in all cases and by an anti-p24 monoclonal antibody, in seven cases. In addition, hepatocytes also clearly scored positive for HIV-1 RNA in three cases. These results demonstrate the infection of both parenchymal and non-parenchymal liver cells by HIV-1 in vivo and therefore show that HIV-1 can infect an epithelial CD4-negative cell type.

Genetic differences accounting for evolution and pathogenicity of simian immunodeficiency virus from a sooty mangabey monkey after cross-species transmission to a pig-tailed macaque.

We determined the nucleotide sequences of two related isolates of simian immunodeficiency virus from the sooty mangabey monkey (SIVsmm) that exhibit dramatic differences in virulence. These isolates are separated by one experimental cross-species transmission, from sooty mangabey to pig-tailed macaque. The parental virus (SIVsmm9), nonpathogenic in the original host (sooty mangabeys), causes a chronic AIDS-like disease in macaques. In contrast, the variant virus (SIVsmmPBj14) induces an acute lethal disease in various macaque species and is also pathogenic for sooty mangabeys. The combination of necessary and sufficient mutations that determined the acutely lethal phenotype on the SIVsmm9 genetic background is included within a maximal set of 57 point mutations, plus two insertions located in the long terminal repeat (22 bp spanning an NF-kappa B-like enhancer element) and in the surface envelope glycoprotein (5 amino acids). Comparisons of synonymous and nonsynonymous nucleotide substitutions in the genome of SIVsmm indicated that selective pressures, probably due to the host immune response, favored amino acid changes in the envelope. This immunoevolutionary mechanism could explain the increase in diversity and the apparition of new virulent phenotypes after cross-species transmission.

Frequent and early in utero HIV-1 infection.

We have investigated in utero human immunodeficiency virus type 1 (HIV-1) transmission by analyzing human fetal tissues for the presence of viral DNA by means of the polymerase chain reaction (PCR). Thirty three fetal samples: thymus, spleen, and peripheral mononuclear blood cells (PMBC) were obtained at abortion (16 to 24 weeks) from HIV-1-infected asymptomatic women. The results of HIV-1-DNA detection were considered only in 9 cases where contamination of fetal samples by infected mother cells could be definitely eliminated by using primers specific for a polymorphic cellular locus. PCR allowed the identification of HIV-1 DNA sequences in 6/8, 8/9, and 5/9 of specimens from thymus, spleen, and PMBC, respectively. Positive results were shown in fetuses as early as 16 weeks. Viral cultures as well as assays for serum p24 HIV-1 antigen were negative in 9.9 and 33/33 tested, respectively. Therefore, our results indicate early and frequent in utero HIV-1 infection. Different patterns of viral activation after birth might then lead to either rapid or delayed onset of acquired immunodeficiency syndrome.

The polymerase chain reaction in the human immunodeficiency virus diagnosis.

The PCR technique detects HIV1 and HIV2 DNA and RNA sequences in mononuclear cells with high sensitivity. It allows therefore to analyse the mother to child HIV1 transmission. Moreover, in the near future, the quantification of the PCR products could allow the follow-up of the patients treated for HIV infection.

Polymerase chain reaction for studies of mother to child transmission of HIV1 in Africa.

The feasibility and implications of the use of the polymerase chain reaction (PCR) assay in studies of HIV1 mother to child transmission in Africa were investigated. Uncultured leukocyte blood cells (PBL) obtained in Brazzaville (Congo) from newborns and infants (mean age = 27 weeks) of infected mothers were tested. HIV1 DNA sequences were identified in the PBL of six of eight newborns and 14 of 23 babies born to HIV1-positive mothers. In addition two of four babies, who at birth had been seropositive and subsequently were seronegative, were HIV1 DNA positive by PCR. This study demonstrates directly, therefore, a high rate of HIV1 transmission in Africa; it also indicates that PCR should be used for such epidemiological studies.

Detection of HIV1 DNA in infants and children by means of the polymerase chain reaction.

The polymerase chain reaction (PCR) assay was used to investigate the possibility of HIV1 DNA detection in uncultured peripheral blood mononuclear cells from newborn infants and children of HIV-infected mothers. HIV1 DNA sequences were detected in mononuclear cells of six of fourteen symptom-free newborn infants of seropositive mothers. Only one of these infants had detectable HIV antigenaemia. In addition, HIV1 DNA was identified in the mononuclear cells of five of ten children (2-5 years old) of infected mothers who had become seronegative 12-15 months after birth; among these, four children had only mild clinical features related to HIV infection, while the other had none. HIV1 DNA was shown in all of eight seropositive children with HIV infection and none of fifteen normal seronegative controls. The PCR assay thus provides an early and direct identification of HIV infection in newborn infants and seronegative children born to infected mothers.