Length variation of glycoprotein 120 V2 region in relation to biological phenotypes and coreceptor usage of primary HIV type 1 isolates.

Conflicting data have been published concerning the correlation between the length of the second variable region (V2) in the HIV-1 envelope and the biological phenotype of the virus. Here the V2 region length of primary HIV-1 isolates was compared with biological phenotype and coreceptor usage. The V2 region variation was determined by DNA fragment length analysis, virus biological phenotype by the MT-2 cell assay, and coreceptor usage by infection of U87.CD4 cells expressing CCR3, CCR5, or CXCR4. Ninety-three primary virus isolates from 40 patients were analyzed. This panel of viruses included sequential isolates obtained from patients who progressed to AIDS with or without a virus phenotypic switch. We found that NSI MT-2-negative isolates had significantly shorter V2 regions than SI MT-2-positive isolates. However, when V2 region lengths of viruses were analyzed in more detail, we observed that NSI isolates obtained from patients shortly before the phenotypic switch had V2 region lengths similar to those of SI isolates. V2 regions of NSI isolates obtained from patients who progressed to AIDS without a virus phenotypic switch had, in contrast, shorter V2 region than isolates obtained just before virus phenotypic switch. Coreceptor analysis revealed that CCR5-using (R5) isolates generally had shorter V2 regions than virus isolates with the ability to enter CXCR4-expressing cells. Moreover, no significant difference in V2 region length was observed between monotropic SI isolates, that is, X4 isolates, and multitropic SI isolates, that is, R3R5X4 or R5X4 isolates. Thus, we conclude that R5 NSI isolates obtained from patients with stable virus phenotype through the whole disease course display shorter V2 regions than isolates obtained from patients at switch of virus phenotype, suggesting that V2 region length may influence virus coreceptor usage.     

CCR5 is the major coreceptor used by HIV-1 subtype C isolates from patients with active tuberculosis.

Tuberculosis (TB) is the major opportunistic infection of HIV-infected patients in developing countries and is associated with activation of the immune system and increased HIV-1 expression. The aim of this study was to explore the biological properties of HIV-1 isolates from patients with active TB. Ten HIV-1 subtype C isolates were analyzed for biological phenotypes, using MT-2 cells, and for coreceptor usage, using coreceptor-transfected cell lines. All isolates were nonsyncytium inducing (NSI) in the MT-2 assay and replicated in CCR5-expressing cells. None of the isolates used CXCR4 or any of the minor coreceptors (CCR1, CCR2b, or CCR3) efficiently. Analysis of the V3 region showed that all isolates contained the GPGQ motif characteristic of subtype C and also had a sequence profile typical of NSI viruses. These data indicate that despite their advanced disease state, patients with TB harbor viruses that use the CCR5 coreceptor. It is possible that activation of monocytes and macrophages during TB infection results in the expansion of macrophage-tropic isolates that preferentially use CCR5.     

Biological characterization and chemokine receptor usage of HIV type 1 isolates prevalent in Brazil

The human immunodeficiency virus type 1 (HIV-1), the etiological agent of the acquired immunodeficiency syndrome (AIDS), shows a variety of biological properties, which may constitute an obstacle to development of effective vaccines or antiretroviral therapy. To characterize Brazilian strains of HIV-1, we studied 24 viruses isolated from blood samples of HIV-1-positive patients from different regions of the country. To examine the cell tropism and the virus ability to form syncytia, primary macrophages and the CD4+ T cell line MT-2 were infected with these viruses. We found that 22 isolates replicated well in macrophages (macrophage-tropic isolates), 2 infected only MT-2 cells (T cell line tropic variants), while 6 of them grew in both cells. We found 8 syncytium-inducing (SI) and 16 non-SI (NSI) isolates. Continuous cultures of 18 isolates were established in the CCR5+/CXCR4+ cell line PM-1, and SI/NSI features of these viruses were confirmed by cell fusion assay with uninfected CD4+ T cell lines (PM-1, MT-2, H9, and SUP-T1). The coreceptor usage of 18 isolates was investigated by infecting U87 cells transfected with CD4 and chemokine receptors, and we found that 11 isolates infected only CCR5+ cells, 3 only CXCR4+ cells, whereas 4 used both coreceptors. We also observed that X4 isolates were more sensitive to neutralization by dextran sulfate than R5 or R5X4 viruses. Our findings show that the Brazilian isolates are phenotypically similar to those prevalent in other regions, which could mean that therapeutic strategies based on HIV-1 phenotypic properties would be efficient in Brazil, as in other countries.     

Coreceptor usage of primary HIV type 1 isolates obtained from different lymph node subsets

Biological characteristics of virus quantitatively rescued from different cell types present in lymph nodes of HIV-1-infected individuals in various stages of their disease were determined, not including patients with AIDS defining illness. Viruses were obtained by cocultivation with donor monocyte-derived macrophages and T-lymphocytes and their biological phenotype compared to viruses obtained from the peripheral blood mononuclear cells of the same patient. The biological phenotype was determined on established cell lines (U937-2, CEM, and MT-2) and on the U87.CD4 coreceptor indicator cell lines and variable region 3 (V3) of the envelope was subjected to direct sequencing. All isolates obtained from lymph node subsets used CCR5 as coreceptor. Furthermore, these viruses were also sensitive to inhibition by beta-chemokines as analyzed for viruses of one patient. All 12 V3 regions showed a unique sequence indicating compartmentalization within each patient. The biological phenotype of CCR5-dependent (R5) HIV-1 isolates obtained from PBMC resembles the phenotype of viruses isolated from different lymph node cell subsets.     

Genotypic and phenotypic characterization of viral isolates from HIV-1 subtype C-infected children with slow and rapid disease progression

The genotypes and biological phenotypes of HIV-1 isolates obtained from 40 perinatally infected children in South Africa were analyzed. This included 15 infants who had HIV-related symptoms, most of whom died within 2 years of birth (rapid progressors), and 25 children who survived between 4 and 9 years with varying signs of disease (slow progressors). Heteroduplex mobility assays and sequence analysis confirmed that within the env and gag regions, all isolates were HIV-1 subtype C. Viral isolates from 14 of the 15 rapid progressors used the CCR5 coreceptor, whereas 1 (02ZARP1) used both the CXCR4 and CCR5 coreceptors. Among the 25 slow progressors, 22 isolates used CCR5 only, 2 used CXCR4 only, and 1 used both CCR5 and CXCR4. Two of the slow-progressing children who harbored CXCR4-using viruses had AIDS. All four CXCR4-using viruses had genotypic changes in the V3 region previously shown to be associated with CXCR4 usage. This cross-sectional study shows that HIV-1 subtype C viruses from both rapid- and slow-progressing perinatally infected children used predominantly CCR5. Similar to adults, CXCR4 usage was uncommon among HIV-1 subtype C isolates from pediatric infections.     

Phenotypic characterization of HIV type 1 isolates from Ghana

Viral isolates from 27 HIV-1-infected patients in Ghana, most of whom were symptomatic, were characterized for coreceptor usage using MT-2 and U87.CD4 cells. Irrespective of clinical status, most infections were caused by CCR5-tropic viruses although three CXCR4-tropic viruses were also found. Genotyping was performed by sequencing the gp41 region. Seven viruses clustered with subtype G reference strains, while the remaining 20 viruses clustered within the subtype A reference viruses. Most subtype A isolates clustered loosely with the CRF02_AG viruses and are described as CRF02_AG-like. The V3 loop was sequenced in selected isolates including all isolates capable of using CXCR4. The V3 region of CXCR4-using viruses contained genetic traits characteristic of CXCR4-using subtype B and C viruses, such as increased charge, the presence of positively charged residues at positions 11 and 25, and loss of a predicted glycosylation site. This study supports previous work showing that CRF02_AG is responsible for most HIV-1 infections in Ghana at this time. The predominance of CCR5-using viruses, even in symptomatic patients, suggests that CCR5-blocking strategies may be useful for prevention and treatment of HIV-1 infections in Ghana.     

Determinants for the syncytium-inducing phenotype of HIV-1 subtype F isolates are located in the V3 region

The HIV-1 syncytium-inducing phenotype is determined by virus replication and the presence of cytopathic effects in MT-2 cells. There is a strong correlation between the syncytium-inducing/MT-2-tropic phenotype and positively charged amino acids at positions 306 and 320 in the V3 loop for HIV-1 subtypes A, B, D, and E. In contrast, a lack of correlation between signature amino acids and syncytium formation in MT-2 cells for subtype F viruses from Romania has been reported. Virus phenotype and V3 loop amino acid sequences from Romanian HIV-1 subtype F isolates were further investigated in the present study. While the determinants of MT-2 tropism are clearly harbored in the V3 loop of subtype F isolates from Romania, the induction of syncytium formation occurs in the presence or absence of positively charged amino acids at positions 306, 320, and/or 324. However, the net positive charge of V3 loop sequences derived from syncytium-inducing viruses was higher than that of the nonsyncytium-inducing isolate.     

Genotypic characterization and comparison of full-length envelope glycoproteins from South African HIV type 1 subtype C primary isolates that utilize CCR5 and/or CXCR4

CCR5 has preferentially been used by all circulating HIV-1 subtype C viruses for cell entry. Recently, we reported the highest proportion of CXCR4-utilizing primary isolates among a cohort of 20 South African AIDS patients. This study describes and compares the Env genotypic characteristics from these 20 HIV-1 subtype C (and unique CD recombinant) primary isolates. Fourteen primary isolates utilized CCR5, four (including the CD recombinant) used CXCR4, and two were dual tropic. Extensive analysis and comparison of important structural motifs such as the N-linked glycosylation sites, signal sequences, CD4-binding sites, variable loops, cleavage sites, known neutralizing antibody and small molecule inhibitor binding sites confirmed that other than the expected differences in the V3 loop, no sequence motifs distinguished between R5 and X4 tropism. Further correlation of the env genotype to functionally relevant motifs is necessary to elucidate the relationship between biologically and immunologically relevant sites and aid vaccine and novel drug design.     

Coreceptor utilization of HIV type 1 subtype E viral isolates from Thai men with HIV type 1-infected and uninfected wives.

HIV-1 coreceptors CCR5 and CXCR4 play an important role in viral entry and pathogenesis. To better understand the role of viral tropism in HIV-1 transmission, we examined the coreceptor utilization of viral isolates obtained from men enrolled in a study of heterosexual transmission in northern Thailand. Viral isolates were obtained from HIV-1-positive males who had either HIV-1-infected spouses (RM; n = 5) or HIV-1-uninfected spouses (HM; n = 10). Viral isolates from 1 of the 5 RM males and 2 of the 10 HM males were CCR5 tropic, whereas isolates from 3 RM males and 6 of the HM male isolates were CXCR4 tropic. Of the nine X4-tropic isolates, seven also used at least one of the following coreceptors: CCR8, CCR1, CCR2b, or CX3CR1, and none employed CCR5 as an additional coreceptor. More importantly, three isolates, RM-15, HM-13, and HM-16 (one from a transmitter and two from nontransmitter), did not infect GHOST4.cl.34 cells expressing any of the known coreceptors. Further analysis using MAGI-plaque assays, which allow visualization of infected cells, revealed that RM-15 had low numbers of infected cells in MAGI-R5 and MAGI-X4 cultures, whereas HM-13 and HM-16 had high levels of plaques in MAGI-X4 cultures. Replication kinetics using activated lymphocytes revealed that these three isolates replicated in CCR5(+/+) as well as CCR5(-/-) peripheral blood mononuclear cells, suggesting that these isolates did not have an absolute requirement of CCR5 for viral entry. All three isolates were sensitive to the X4-antagonistic compounds T-22 and AMD3100. Analysis of the C2V3 region did not reveal any significant structural differences between any of the Thai subtype E isolates. Thus, there was no association between the pattern of coreceptor usage and transmissibility among these subtype E HIV-1 isolates.     

Appraising the performance of genotyping tools in the prediction of coreceptor tropism in HIV-1 subtype C viruses

ABSTRACT: BACKGROUND: In human immunodeficiency virus type 1 (HIV-1) infection, transmitted viruses generally use the CCR5 chemokine receptor as a coreceptor for host cell entry. In more than 50% of subtype B infections, a switch in coreceptor tropism from CCR5- to CXCR4-use occurs during disease progression. Phenotypic or genotypic approaches can be used to test for the presence of CXCR4-using viral variants in an individual's viral population that would result in resistance to treatment with CCR5-antagonists. While genotyping approaches for coreceptor-tropism prediction in subtype B are well established and verified, they are less so for subtype C. METHODS: Here, using a dataset comprising V3 loop sequences from 349 CCR5-using and 56 CXCR4-using HIV-1 subtype C viruses we perform a comparative analysis of the predictive ability of 11 genotypic algorithms in their prediction of coreceptor tropism in subtype C. We calculate the sensitivity and specificity of each of the approaches as well as determining their overall accuracy. By separating the CXCR4-using viruses into CXCR4-exclusive (25 sequences) and dual-tropic (31 sequences) we evaluate the effect of the possible conflicting signal from dual-tropic viruses on the ability of a of the approaches to correctly predict coreceptor phenotype. RESULTS: We determined that geno2pheno with a false positive rate of 5% is the best approach for predicting CXCR4-usage in subtype C sequences with an accuracy of 94% (89% sensitivity and 99% specificity). Contrary to what has been reported for subtype B, the optimal approaches for prediction of CXCR4-usage in sequence from viruses that use CXCR4 exclusively, also perform best at predicting CXCR4-use in dual-tropic viral variants. CONCLUSIONS: The accuracy of genotyping approaches at correctly predicting the coreceptor usage of V3 sequences from subtype C viruses is very high. We suggest that genotyping approaches can be used to test for coreceptor tropism in HIV-1 group M subtype C with a high degree ofconfidence that they will identify CXCR4-usage in both CXCR4-exclusive and dual tropic variants.     

Emergence of X4 usage among HIV-1 subtype C: evidence for an evolving epidemic in South Africa

This study investigated the genotype and phenotype of HIV-1 isolates of 20 South African AIDS patients. We found the highest percentage of CXCR4 usage among primary isolates, in which 30% efficiently utilized CXCR4 and exhibited the syncytium-inducing phenotype. Phylogenetic analysis of env confirmed that 19 of the 20 were subtype C, and syncytium-inducing viruses had genetic changes in the V3 loop, characteristic of CXCR4 usage. Results imply that the frequency of CXCR4-utilizing subtype C is increasing with time.     

Genotypic and phenotypic analysis of HIV type 1 primary isolates from western Cameroon.

In this study we report the molecular and biological characteristics of 19 HIV-1 primary isolates obtained in April 1999 from 47 HIV-1-infected individuals living mainly in western Cameroon. Discontinuous portions of gag, pol, and env were amplified by polymerase chain reaction and directly sequenced. Phylogenetic analysis of these sequences showed that all were of HIV-1 group M with the following genotypes: A(gag)/A(pol)/A(env) (n = 4), A(gag)/AG(pol)/AG(env) (n = 2), AG(gag)/A(pol)/AG(env) (n = 1), AG(gag)/U(pol)/AG(env) (n = 1), AG(gag)/AG(pol)/AG(env) (n = 6), G(gag)/G(pol)/G(env) (n = 3), F2(gag)/F2(pol)/F2(env) (n = 1), and a novel A(gag)/J(pro/rt)/A(int)/U(env) complex recombinant (n = 1). This A/J/U recombinant shared the same gag-pol cross-over point with known CRF02.AG viruses and 99CMBD6, an AG recombinant from our panel of isolates. The biological phenotype of most of the isolates correlated with the clinical status of the patient. Six isolates were syncytium inducing (SI) on MT-2 cells whereas 13 isolates were of the non-syncytium-inducing phenotype (NSI). Coreceptor usage by these isolates determined on GHOST cells correlated with their biological phenotype, as all SI isolates used CXCR4 and all NSI isolates used CCR5. Our results show a high predominance of subtype A (mainly CRF02.AG-like viruses) in western Cameroon and fewer HIV-1 subtypes compared with other parts of Cameroon. Genetic variability was, however, not reflected in the biological characteristics of the isolates. The presence of a novel A/J/U complex recombinant from this region further emphasizes the role of recombination in the global evolution of HIV.     

Molecular and phenotypic characteristics of neurotropic HIV-1 subtype E

Although HIV-1 subtype E associated with neurological dysfunction is common, the virological characteristics of HIV-1 isolated from the CNS for this subtype have not yet been identified. In this study, paired blood and CSF isolated from patients with AIDs-defining illnesses were cultured, sequenced and aligned. Phylogenetic tree and nucleotide-distances from both blood and CSF were investigated. Cytopathicity and co-receptor usage of paired blood and CSF isolates were compared to define the specific characteristics of CNS isolates. The results confirmed that CSF isolates showed less cytopathicity. It was found that both blood and CSF isolates used either CXCR4 or CXCR4 and CCR5 as co-receptors. Interestingly, one CSF isolate using CCR3 as a co-receptor was identified. By sequence analysis, the pair-wise distances of envelope gp 120 sequence and those of all variable regions (except V3 region) between blood and CSF isolates were significantly different. The genetic distances in V1/V2 regions of CSF isolates showed more diversity than those of blood isolates. These findings suggest that the evolution of V1/V2 regions of CSF isolates seems to be an advantage for HIV-1 in CNS infection. In contrast, the genetic distance in V4 and V5 regions of CSF isolates showed less diversity, suggesting that conservation in these regions might be necessary during the process of HIV-1 CNS infection.     

Coreceptor requirements of primary HIV type 1 group O isolates from Cameroon.

HIV-1 group O has its epicenter in Cameroon and neighboring countries and is responsible for 3 to 5% of all HIV infections in this region. It is believed that HIV-1 group O was introduced into the human population by a separate cross-species transmission, occurring independently of the HIV-1 (group M and group N) and HIV-2 transmissions. We have studied the coreceptor requirements of 12 primary HIV-1 O-type isolates from individuals with different clinical symptoms. Only 2 of these 12 viruses showed a syncytium-inducing phenotype after infection of primary peripheral blood mononuclear cells (PBMCs) and were infectious for the T cell line C8166. These isolates used CXCR4 as a coreceptor for entry, whereas the remaining isolates used only CCR5 efficiently. One isolate was able to use BOB and CCR8 as coreceptors in addition to CXCR4. All group O isolates tested were efficiently inhibited by SDF-1 or RANTES, the natural ligands of CXCR4 and CCR5, respectively. These results indicate that CXCR4 and CCR5 are the principal coreceptors for HIV-1 O-type viruses. Most of the HIV-1 group O isolates studied were derived from patients at later stages of the disease. Although HIV-1 group O and group M infections do not differ in their pathogenesis, the studied isolates did not evolve to use a broad range of coreceptors as described for HIV-1 group M and HIV-2.     

Sensitivity of HIV type 1 subtype C isolates to the entry inhibitor T-20

T-20 is the first in a new class of antiretroviral drugs targeting the entry stage of the virus life cycle. It is a 36 amino acid peptide that binds to the HR1 region of gp41 preventing gp41-mediated fusion with the host cell membrane. T-20 was designed based on the HR2 sequence of HIV-1 subtype B gp41, a region that shows significant genetic variation with HIV-1 subtype C sequences. In order to assess the efficacy of T-20 to inhibit subtype C isolates, a total of 23 isolates were tested for their ability to replicate in the presence of T-20. This included 15 isolates that used CCR5, five that used both CCR5 and CXCR4, and three that used CXCR4. Five of these were from patients failing other antiretroviral therapies. Sequence analysis of the HR2 region indicated that there were 10-16 amino acid changes in the region corresponding to T-20. However, all isolates were effectively inhibited by T-20 at 1 microg/ml. There were no significant differences between viruses that used CCR5 or CXCR4 to enter cells. All isolates, except one, had GIV at positions 36-38 in the HR1 region. One isolate had a GVV motif but this did not affect its sensitivity to T-20. Therefore, T-20 inhibited subtype C viruses despite significant genetic differences in the HR2 region and there was no evidence for baseline resistance to T-20. These data suggest that T-20 would be highly effective in patients with HIV-1 subtype C infection, including those failing existing antiretroviral drug regimens.     

Biological characterization of HIV type 1 envelope V3 regions from mothers and infants associated with perinatal transmission.

Our previous study has shown that the human immunodeficiency virus type 1 (HIV-1) envelope V3 region minor genotypes of infected mothers were transmitted to their infants and predominated initially as a homogeneous virus population in the infants (Ahmad N, Baroudy BM, Baker RC, et al.: J Virol 1995;69:1001-1012). Here we have characterized the biological properties, including cellular tropism, replication efficiency, cytopathic effects, and coreceptor utilization, of these V3 region isolates from mothers and infants. Nineteen V3 region sequences from three mother-infant pairs, including the minor variants of mothers and the major variants of infants as characterized in our previous study, were reciprocally inserted into an HIV-1 infectious molecular clone, pNL4-3, and chimeric viruses were generated by DNA transfections into HeLa cells. Equal amounts of chimeric viruses were then used to infect T lymphocyte cell lines (A3.01 and MT-2), primary blood lymphocytes (PBLs), primary monocyte-derived macrophages (MDMs), and coreceptor cell lines. We found that the V3 region chimeras failed to replicate in T lymphocyte cell lines but replicated in MDMs and PBLs, albeit at reduced levels compared with R5 laboratory HIV-1 strains. In addition, the V3 region chimeras were able to infect the HOS-CD4(+)CCR5(+) cell line, suggesting CCR5 coreceptor utilization. Moreover, the V3 region chimeras were unable to induce syncytia in MT-2 cells, indicative of non-syncytium-inducing (NSI) phenotypes. In conclusion, the HIV-1 minor genotypes of infected mothers with macrophage-tropic and NSI or R5 phenotypes are transmitted to their infants and are initially maintained with the same properties.     

Position 22 of the V3 loop is associated with co-receptor usage and disease progression in HIV-1 subtype B isolates

Our goal in this study was to analyze position 22 of the V3 loop associated with co-receptor usage and disease progression in human immunodeficiency virus type 1 (HIV-1) subtype B infection. Bioinformatics approaches were used to compare the amino acid sequence and secondary structure of the V3 loop of the CCR5-tropic virus and CXCR4-tropic virus in HIV-1 subtype B. HIV-1 subtype B V3 amino acid sequence files in the FASTA format were collected from the HIV Sequence Database. The amino acid sequences of different tropism were multiple-aligned with CLUSTAL W program, and the frequencies of the amino acids at each position of the V3 loop sequences of two groups were calculated and sorted in descending order. The secondary structure of the consensus V3 amino acid sequences from CCR5-tropic and CXCR4-tropic viruses were predicted with the APSSP2 method. The amino acids at positions 11, 22, and 25 of V3 were different between the CCR5-tropic virus and CXCR4-tropic virus. The consensus amino acid frequencies were found to be 71.9% S, 66.7% A, and 56.0% D for the CCR5-tropic virus and 50.0% R, 57.1% T, and 26.2% Q for the CXCR4- tropic virus at positions 11, 22, and 25, respectively. There was a strong association between the identity of the residues at position 11, 22, and 25 of the V3 loop amino acid sequence and CD4+ T cell counts of different patients. The change of the residue at position 22 in the R5-tropic or X4-tropic viruses is expected to likely change the secondary structure to be similar to the X4-tropic or R5-tropic viruses. Our study indicates that position 22 of the V3 loop amino acid sequence is significantly associated with viral tropism and disease progression in HIV-1 subtype B.     

Coreceptor change appears after immune deficiency is established in children infected with different HIV-1 subtypes

Change of HIV-1 coreceptor use has been connected to progression of disease in children infected with HIV-1, presumably subtype B. It has not been possible to discern whether the appearance of new viral phenotypes precedes disease development or comes as a consequence of it. We studied the evolution of coreceptor use in HIV-1 isolates from 24 vertically infected children. Their clinical, virological, and immunological status was recorded and the env V3 subtype was determined by DNA sequencing. Coreceptor use was tested on human cell lines, expressing CD4 together with CCR5, CXCR4, and other chemokine receptors. The children carried five different env subtypes (nine A, five B, four C, three D, and one G) and one circulating recombinant form, CRF01_AE (n = 2). Of the 143 isolates, 86 originated from peripheral blood mononuclear cells (PBMCs) and 57 originated from plasma, received at 90 time points. In 52 of 54 paired plasma and PBMC isolates the coreceptor use was concordant. All 74 isolates obtained at 41 time points during the first year of life used CCR5. A change from use of CCR5 to use of CXCR4 occurred in four children infected with subtype A, D, or CRF01_AE after they had reached 1.5 to 5.8 years of age. There was a significant association with decreased CD4+ cell levels and severity of disease but, interestingly, the coreceptor change appeared months or even years after the beginning of the immunological deterioration. Thus CXCR4-using virus may emerge as a possible consequence of immune deficiency. The results provide new insights into AIDS development in children.     

HIV phenotype correlates with the relative amounts of lymphocyte function-related molecule 1 (LFA-1) and major histocompatibility complex (MHC) class II in the virion envelope

OBJECTIVE: The biological phenotype of HIV-1 has been associated with various aspects of its infectivity, including syncytium formation and coreceptor usage. Adhesion molecules, present on both the target cell and the virus, have also been shown to play a role in the infectious process. A possible correlation between the presence of adhesion molecules in the envelope of HIV-1 with the biological phenotype of the virus is examined. DESIGN: The envelopes of 56 isolates of HIV-1 of known biological phenotype were analyzed for the presence of lymphocyte function-related molecule 1 (LFA-1) and major histocompatibility complex (MHC) class II molecules. METHODS: The coreceptor usage of each isolate was determined in a GHOST cell or a U87.CD4 infectivity assay. The presence of LFA-1 and MHC class II in each virus envelope was then determined using a virus-binding enzyme-linked immunosorbent assay (ELISA). RESULTS: Viruses using the chemokine receptor CCR5 have relatively higher levels of MHC class II than LFA-1 in their envelopes compared with those using CXCR4. CONCLUSIONS: The finding that there is a differential incorporation of MHC class II and LFA-1 molecules by CXCR4- and CCR5-using viruses augments the list of properties contributing to the biological phenotype of HIV-1. This may explain, in part, how CXCR4-using viruses are able to bind to and infect a broader range of cell types than CCR5-using viruses, and why CXCR4-using viruses are associated with a more aggressive disease course.