Viral phenotype in mother-to-child HIV-1 transmission and disease progression of vertically acquired HIV-1 infection

Identification of CRF10_CD viruses among bar and hotel workers in Moshi, Northern Tanzania

We recently identified an HIV-1 subtype C and D circulating recombinant form (CRF10_CD) in infants in Dar es Salaam, Tanzania. So far, this is the only reported HIV-1 CRF in East Africa. However, evidence for its spread in the adult population is scarce. Here we describe the presence of CRF10_CD in two asymptomatic bar and hotel workers in Moshi, Northern Tanzania. Subgenomic sequences from gag (3'p24-5'p7), env (C2-C5), and the 5' LTR were used for phylogenetic analysis and identification of recombination. Genetic divergence between the CRF10_CD sequences from Moshi suggested that they were contracted from independent sources. A third bar worker was infected with an apparent CRF10_CD/subtype A recombinant virus. Our data indicate that CRF10_CD genomes can be transmitted both vertically and heterosexually.

Age-related changes in expression of CXCR4 and CCR5 on peripheral blood leukocytes from uninfected infants born to human immunodeficiency virus type 1-infected mothers

Cross-sectional analysis of human immunodeficiency virus-exposed, uninfected infants revealed high proportions of CXCR4-expressing cells in their cord blood, which declined at 4.5 months and increased between 9 and 15 months to levels approaching those of uninfected adults. Proportions of CCR5-expressing cells, however, were very low in cord blood and subsequently increased with age.

Effect of perinatal short-course zidovudine on the clinical and virological manifestations of HIV-1 subtype E infection in infants

BACKGROUND

The perinatal short-course zidovudine (ZDV) chemoprophylaxis that can reduce HIV-1 vertical transmission by 51% has been widely practiced in developing countries such as Thailand because of its simpler and less cost.

OBJECTIVES

To investigate the effects of short-course regimen of oral ZDV for prophylaxis of HIV-1 subtype E vertical transmission among 'break-through' HIV-1 infected infants.

STUDY DESIGN

The study analyzed clinical and virological outcomes of 80 infants, whose mothers received ZDV prophylaxis starting at 36 weeks gestation (group Z) and 37 infants whose mothers never received anti-retroviral drugs (group C), at the ages of 1-2, 4-6, and 12 months.

RESULTS

Of the 12 HIV-1 infected infants, 5/7 (71.4%) from group Z and 1/5 (20%) from group C progressed to a symptomatic clinical stage by the age 4-6 months. The intersample nucleotide distance of HIV-1 pol reverse transcriptase (RT) sequences of isolates collected at age of 1-2 months from group Z was significantly higher than that from group C (3.34 and 2.92%, P=0.02). All twelve virus isolates from infected infants were non syncytium inducing (NSI) and macrophage tropic strains; and 5/6 (83.3%) viruses from symptomatic infants were also T-tropic viruses. The symptomatic infants also had significantly higher HIV-1 nucleic acid quantitation than asymptomatic infants.

CONCLUSION

Our results preliminary suggested that infected infants who were perinatally exposed to ZDV may have a more rapid early disease progression with unfavorable viral manifestations than those without exposure to antiretroviral drug.

Association of HIV-1 viral phenotype in the MT-2 assay with perinatal HIV transmission

A case-control design study was used to investigate the association of maternal HIV-1 phenotype in MT-2 cells at or near the time of delivery with perinatal transmission of HIV-1, controlling for maternal CD4 percentage and duration of rupture of membranes, in 48 transmitting and 96 non-transmitting HIV-1-infected mothers who gave birth between 1990 and 1995. The non-syncytium-inducing (NSI) phenotype was more commonly seen in transmitting mothers compared with non-transmitting mothers (90% vs. 75%, p =.04). In a multivariable logistic regression model, the following maternal characteristics were significantly associated with HIV transmission: NSI phenotype (odds ratio [OR] = 6.08; 95% confidence interval [CI]: 1.73-21.35) and log(10) viral load (OR = 2.11; CI: 1.19-3.74). Finally, the association of NSI phenotype with transmission was stronger in transmitting women who received azidothymidine during pregnancy compared with transmitters who did not.

Chemokine receptor expression by human syncytiotrophoblast--a review

Knowledge of chemokine receptor expression by human syncytiotrophoblast has important implications for our understanding of maternal-fetal HIV transmission as well as for understanding the regulation of placental growth and development. This review discusses what is known about chemokine receptor expression by trophoblast and other placental cells. In addition, new data are presented showing that CXCR4 is expressed on the syncytiotrophoblast surface. In other new studies, leukocyte-mediated HIV-1Lai(an X4 strain) infection of syncytiotrophoblast cultures was reduced when stromal derived factor-1alpha was added to the cocultures, consistent with a role for CXCR4. The available information on chemokine receptor expression by trophoblast is discussed in terms of the apparent selective transmission of R5 strains. Studies in other systems indicate that caution must be used in predicting chemokine receptor usage by different HIV isolates, particularly when the route of infection is cellmediated.

Chemokine receptor expression by human syncytiotrophoblast

Despite their potential importance in placental HIV infection and placental immune function, nothing is known about the expression of chemokine receptors by human syncytiotrophoblast cells. Immunocytochemical analysis revealed that primary cultures of term syncytiotrophoblast cells express CCR1, CCR3, CXCR4, and CCR6. Immunohistochemical examination of cryosections of term placental villous tissue confirmed the expression of CCR3, CXCR4, and CCR6 by trophoblast cells. The primary syncytiotrophoblast cultures showed no reactivity with antibodies against CCR5. In the villous tissue sections, CCR5 was detected in stromal cells and blood vessel walls but was not found in trophoblast cells. RT-PCR analysis of RNA extracted from cultured syncytiotrophoblast cells confirmed that the cells express message for CCR1, CCR3, CXCR4, CCR6 and CCR10. No transcripts corresponding to CCR2b, CCR5, or CCR8 were detected. Other experiments showed that exposure of syncytiotrophoblast cells to soluble SDF-1alpha elicited a calcium mobilization response, consistent with the expression of functional CXCR4. Thus, human syncytiotrophoblast cells express CXCR4, a known co-receptor for TCL-tropic HIV-1 isolates but do not express CCR5, the major co-receptor for M-tropic isolates. In addition to implications for the maternal-fetal transmission of HIV, the expression of chemokine receptors by syncytiotrophoblast cells could be important in other aspects of placental immune function.

Vertical human immunodeficiency virus type 1--HIV-1--transmission--a review

Several factors appear to affect vertical HIV-1 transmission, dependent mainly on characteristics of the mother (extent of immunodeficiency, co-infections, risk behaviour, nutritional status, immune response, genetical make-up), but also of the virus (phenotype, tropism) and, possibly, of the child (genetical make-up). This complex situation is compounded by the fact that the virus may have the whole gestation period, apart from variable periods between membrane rupture and birth and the breast-feeding period, to pass from the mother to the infant. It seems probable that an extensive interplay of all factors occurs, and that some factors may be more important during specific periods and other factors in other periods. Factors predominant in protection against in utero transmission may be less important for peri-natal transmission, and probably quite different from those that predominantly affect transmission by mothers milk. For instance, cytotoxic T lymphocytes will probably be unable to exert any effect during breast-feeding, while neutralizing antibodies will be unable to protect transmission by HIV transmitted through infected cells. Furthermore, some responses may be capable of controlling transmission of determined virus types, while being inadequate for controlling others. As occurrence of mixed infections and recombination of HIV-1 types is a known fact, it does not appear possible to prevent vertical HIV-1 transmission by reinforcing just one of the factors, and probably a general strategy including all known factors must be used. Recent reports have brought information on vertical HIV-1 transmission in a variety of research fields, which will have to be considered in conjunction as background for specific studies.

Inhibition of HIV type 1 infection with a RANTES-IgG3 fusion protein

The natural ligands for the chemokine receptors CCR5 (RANTES, MIP-1alpha, and MIP-1beta) and CXCR4 (SDF-1) can act as potent inhibitors of infection by the human immunodeficiency virus type 1 (HIV-1) at the level of viral entry. Unlike antibody-mediated inhibition, chemokine-mediated inhibition is broadly effective. Different HIV-1 strains can utilize the same coreceptor(s) for viral entry and, therefore, can be blocked by the same chemokine(s). HIV-1 strains that are highly resistant to neutralization by V3-specific antibodies are sensitive to inhibition by chemokines. Therefore, the use of chemokine-derived molecules constitutes a potential therapeutic approach to prevent infection by HIV-1. We have generated a fusion protein between RANTES and human IgG3 (RANTES-IgG3). The effectiveness of RANTES-IgG3 inhibition of infection by HIV-1 was similar to that of rRANTES. Inhibition of HIV-1 by RANTES-IgG3 was specific for CCR5-dependent but not CXCR4-dependent HIV-1 isolates. Fusion of a chemokine to an IgG moiety offers two desirable properties with respect to the recombinant chemokine alone. First, IgG fusion proteins have extended half-lives in vivo. Second, molecules with IgG heavy chain moieties may be able to cross the placenta and potentially induce fetal protection.

CXCR4 and CCR5 on Human Thymocytes: Biological Function and Role in HIV-1 Infection

Thymocyte infection with HIV-1 is associated with thymic involution and impaired thymopoiesis, particularly in pediatric patients. To define mechanisms of thymocyte infection, we examined human thymocytes for expression and function of CXCR4 and CCR5, the major cell entry coreceptors for T cell line-tropic (T-tropic) and macrophage-tropic (M-tropic) strains of HIV-1, respectively. CXCR4 was detected on the surface of all thymocytes. CXCR4 expression on mature, high level TCR thymocytes was similar to that on peripheral blood T cells, but was much lower than that on immature thymocytes, including CD34+ thymic progenitors. Consistent with this, stroma-derived factor-1 (SDF-1) induced calcium flux primarily in immature thymocytes, with CD34+ progenitors giving the strongest response. In addition, SDF-1 mRNA was detected in thymic-derived stromal cells, and SDF-1 induced chemotaxis of thymocytes, suggesting that CXCR4 may play a role in thymocyte migration. Infection of immature thymocytes by the T-tropic HIV-1 strain LAI was 10-fold more efficient than that in mature thymocytes, consistent with their relative CXCR4 surface expression. Anti-CXCR4 antiserum or SDF-1 blocked fusion of thymocytes with cells expressing the LAI envelope. In contrast to CXCR4, CCR5 was detected at low levels on thymocytes, and CCR5 agonists did not induce calcium flux or chemotaxis in thymocytes. However, CD4+ mature thymocytes were productively infected with the CCR5-tropic strain Ba-L, and this infection was specifically inhibited with the CCR5 agonist, macrophage inflammatory protein-1β. Our data provide strong evidence that CXCR4 and CCR5 function as coreceptors for HIV-1 infection of human thymocytes.