Lateral and End-On Kinetochore Attachments Are Coordinated to Achieve Bi-orientation in Drosophila Oocytes

In oocytes, where centrosomes are absent, the chromosomes direct the assembly of a bipolar spindle. Interactions between chromosomes and microtubules are essential for both spindle formation and chromosome segregation, but the nature and function of these interactions is not clear. We have examined oocytes lacking two kinetochore proteins, NDC80 and SPC105R, and a centromere-associated motor protein, CENP-E, to characterize the impact of kinetochore-microtubule attachments on spindle assembly and chromosome segregation in Drosophila oocytes. We found that the initiation of spindle assembly results from chromosome-microtubule interactions that are kinetochore-independent. Stabilization of the spindle, however, depends on both central spindle and kinetochore components. This stabilization coincides with changes in kinetochore-microtubule attachments and bi-orientation of homologs. We propose that the bi-orientation process begins with the kinetochores moving laterally along central spindle microtubules towards their minus ends. This movement depends on SPC105R, can occur in the absence of NDC80, and is antagonized by plus-end directed forces from the CENP-E motor. End-on kinetochore-microtubule attachments that depend on NDC80 are required to stabilize bi-orientation of homologs. A surprising finding was that SPC105R but not NDC80 is required for co-orientation of sister centromeres at meiosis I. Together, these results demonstrate that, in oocytes, kinetochore-dependent and -independent chromosome-microtubule attachments work together to promote the accurate segregation of chromosomes.

In acentrosomal oocytes, spindle assembly depends on the chromosomes. The nature of the chromosome-microtubule interactions in oocytes that organize spindle bipolarity and orientation of the homologs has been unclear. We have found that several types of functional chromosome-microtubule interactions exist in oocytes, and that each type participates in unique aspects of chromosome orientation and spindle assembly. We present here a model for chromosome-based spindle assembly and chromosome movements in oocytes that highlights the multiple and unappreciated roles played by the kinetochores and has implications for how homologous chromosomes bi-orient during meiosis.

Closely related HIV-1 CRF01_AE variant among injecting drug users in northern Vietnam: evidence of HIV spread across the Vietnam-China border

To investigate the nature of recent HIV outbreaks among injecting drug users (IDUs) near the Vietnam-China border, we genetically analyzed 24 HIV-positive blood specimens from 2 northern provinces of Vietnam (Lang Son and quang Ninh) adjacent to the China border, where HIV outbreaks among IDUs were first detected in late 1996. Genetic subtyping based on gag (p17) and env (C2/V3) sequences revealed that CRF01_AE is a principal strain circulating throughout Vietnam, including the provinces near the China border. The majority of CRF01_AE sequences among IDUs in Quang Ninh and Lang Son showed significant clustering with those found in nearby Pingxiang City of China's Guangxi Province, sharing a unique valine substitution 12 amino acids downstream of the V3 loop. This particular subtype E variant, uniquely found among IDUs in northern Vietnam and southeastern China, is designated E(v). The genetic diversity of CRF01_AE distributed in Quang Ninh (1.5 +/- 0.6%) and Pingxiang City (1.9 +/- 1.2%) was remarkably low, indicating the emerging nature of HIV spread in these areas. It is also noted that the genetic diversity of CRF01_AE among IDUs was consistently lower than that in persons infected sexually, suggesting that fewer closely related CRF01_AE variants were introduced into IDUs and, conversely, that multiple strains of CRF01_AE had been introduced via the sexual route. The data in the present study provide additional evidence that HIV outbreaks among IDUs in northern Vietnam were caused by the recent introduction of a highly homogeneous CRF01_AE variant (E(v)) closely related to that prevailing in nearby southern China.

Genetic similarity of HIV type 1 subtype E in a recent outbreak among injecting drug users in northern Vietnam to strains in Guangxi Province of southern China

To investigate the molecular epidemiology of a recent HIV-1 outbreak in northern Vietnam and its relation to the epidemic in surrounding areas, we analyzed 17 HIV-positive blood specimens from 3 heterosexuals, 2 sexually transmitted disease patients, and 12 injecting drug users (IDUs), collected in 4 provinces near Hanoi in 1998. These were compared with the specimens from Ho Chi Minh City (n = 10) and An Giang Province (n = 10) in southern Vietnam and with published sequences from neighboring countries. Genetic subtyping based on the env C2/V3 sequences revealed that HIV-1 subtype E predominated throughout Vietnam in all risk populations; the exception was one typical United States-European-type HIV-1 subtype B detected in a patient in Ho Chi Minh City, the first case of HIV infection identified in Vietnam in 1990. The HIV-1 subtype E sequences identified in 9 of the 12 IDUs from northern provinces were closely related phylogenetically to those in IDUs in nearby Guangxi Province of China, and also shared a common amino acid signature downstream of the env V3 loop region. The low interperson nucleotide diversity among IDUs in northern Vietnam supports the view that HIV-1 subtype E was introduced recently among IDUs in northern Vietnam. These data indicate a linkage between HIV-1 circulating among IDUs in northern Vietnam and southern China, and suggest recent transborder introductions as the likely source of HIV-1 subtype E in northern Vietnam.

HIV monitoring in Vietnam: system, methodology, and results of sentinel surveillance

OBJECTIVE

To measure the prevalence of and trends in HIV infections in populations defined by sentinel surveillance in Vietnam.

METHODS

Surveillance was conducted in eight provinces in 1994, expanded to 12 in 1995 and to 20 in 1996. Sentinel populations were sexually transmitted disease (STD) patients, female sex workers (FSW), injecting drug users (IDU), tuberculosis (TB) patients, pregnant women, and military conscripts. Samples were collected twice yearly for high-risk populations and once yearly for low-risk populations.

RESULTS

The overall HIV epidemic in Vietnam comprises several different smaller epidemics. It is primarily associated with injecting drug use, but its extent varies widely throughout the country. In 1998, HIV prevalence rates ranged from 0 to 85% (median, 13.1%), with an aggregate prevalence rate (APR; i.e., the sum of HIV-positive study subjects divided by the sum of all study subjects tested in sentinel provinces) of 17% among IDUs; this ranged from 0 to 14.7% (median, 0.8%), with the APR of 2.4% among FSWs; and from 0 to 6% (median, 0%), with the APR of 0.9% among STD patients. The APRs among antenatal women and army conscripts were less than 0.15%. APRs increased significantly from 1994 to 1998 among STD patients (p < .001), FSWs (p < .001), TB patients (p < .001), and pregnant women (p < .05) in original sentinel provinces. HIV prevalence also increased significantly among younger age groups of IDUs and FSWs.

CONCLUSION

Vietnam's HIV epidemic is increasing predominantly and most rapidly among IDUs. However, prevalence rates among FSWs and STD patients are rising but are still low among pregnant women and army conscripts. Vietnam, at present, is still in the early phase of the HIV epidemic and has time to take effective and appropriate actions.

Identification and molecular characterization of human T lymphotropic virus type II infections in intravenous drug abusers in the former South Vietnam

Previous serological studies have demonstrated that some 60% of intravenous drug abusers (IVDAs) in urban areas of the former South Vietnam are infected with HTLV-II. In the present report we have attempted to characterize the viruses using restriction fragment length polymorphism (RFLP) and nucleotide sequence analysis of the provirus long terminal repeat (LTR) region. RFLP analysis of nine samples demonstrated that all were infected with the HTLV-IIb subtype. The HTLV-IIa subtype was not detected. Phylogenetic analysis of the nucleotide sequences demonstrated that the viruses clustered closely with HTLV-IIb isolates present in IVDAs from the New York City area. The present molecular analysis together with the previously reported absence of HTLV-II infection in North Vietnam supports the view that HTLV-II may have been introduced from the United States to this part of Asia by military personnel during the Vietnam conflict.

Nucleotide sequence variation of human T-lymphotropic virus type II in Vietnam

A high rate of human T-lymphotropic virus type II (HTLV-II) infection has been documented in intravenous drug abusers (IVDAs) in South Vietnam. We have investigated the molecular characteristics of the virus and have shown that one HTLV-II subtype is predominant in Ho Chi Minh City. This molecular subtype, HTLV-IIb, was identified in a number of South Vietnamese by nucleotide sequence analysis of the long terminal repeat (LTR) region. HTLV-IIa was not found. These findings suggest that HTLV-IIb is endemic in IVDAs in South Vietnam, although IVDAs in urban areas in North America are predominantly infected with HTLV-IIa.

Long-term evaluation of immune status in leprosy patients undergoing multiple drug therapy

A long-term survey of leprosy patients of all clinical types, starting at the time of diagnosis, was carried out to monitor clinical, bacteriological and immunological parameters at regular intervals during multiple drug therapy (MDT). The patients were assigned to two groups for treatment following WHO guidelines: paucibacillary (PB) and multibacillary (MB). Immunoglobulin levels, specific antibodies, skin-test responses to different soluble mycobacterial antigens (new tuberculins), and in vitro proliferative responses to mitogens and to antigens were measured during treatment, as were clinical changes, the bacterial index, and clinical improvement. No exact relations between disease activity and IgM antibody levels, both IgM immunoglobulin and specific IgM antibody to a species-specific antigen (ND-O-BSA), could be seen for MB patients. Changes in in vitro cell-mediated immunity and skin-test response seemed to be more directly related to the bacterial load and could reflect the improvement of bacteriological and clinical parameters during MDT.

Serum immunoglobulins, including IgG subclasses, in Vietnamese leprosy patients

Levels of serum immunoglobulins were measured in healthy Vietnamese and in leprosy patients. Healthy Vietnamese had higher levels of IgG, IgA, IgM, and IgE than did healthy Dutch controls, as well as higher levels of three of the four subclasses of IgG (IgG1, IgG2, IgG3). Lepromatous leprosy patients had significant increases in all classes and subclasses of immunoglobulins, except for IgG2, in comparison with local controls. Tuberculoid leprosy patients had more IgG1, IgG3, and IgG4 than did local controls and had higher total IgG levels. The patients had no increase in autoantibodies against tissue antigens compared to local or Dutch controls.

Association between leprosy and immunoglobulin allotypes: Gm-A2m and Km frequencies in Vietnamese

The relationship between immunoglobulin allotypes and leprosy was studied in 91 unrelated patients and 100 healthy controls from Vietnam. Twenty Vietnamese patients with tuberculosis were also typed for the Gm, A2m and Km allotypes. The results were compared with those from the healthy controls. No significant association was found for the allotypes G1m(z,a,x,f) G2m(n), G3m(g,b), A2m(1,2) and Km(1,3) between the two groups of patients and the controls. Heterogeneity in the distribution of G2m(n), G3m(b), A2m(2) and Km(3) was found when 60 polar-lepromatous (LL) patients and 27 borderline-tuberculoid (BT) patients were separated out of the 91 leprosy patients. In the LL patients there appeared to be a significantly higher frequency of G2m(n), G3m(b) and A2m(2) in comparison with the BT patients (P less than 0.05). A significantly lower frequency of Km(3) was found in the LL patients in comparison with the healthy control group (P less than 0.05). The frequencies of the Gm-A2m haplotypes and of the occurrence of the Km(1) and Km(3) in the Vietnamese population were calculated on the basis of the results in the 100 samples of healthy controls. The main haplotype is Gmaf;n;b (frequency 0.676), occurring with A2m1 (0.200), as well as with A2m2 (0.476).

Rosette-forming cells in patients with treated leprosy

White blood cell counts and the percentages and absolute numbers of lymphocytes in the peripheral blood of active lepromatous (BT, BB, BL) leprosy patients, patients with borderline leprosy, and normal controls were determined. Lepromatous patients showed decreased leukocyte counts and elevated percentages of lymphocytes, resulting in normal absolute lymphocyte counts. The proportion of peripheral blood mononuclear cells forming "active" rosettes, standard (4 degrees C overnight) rosettes, and "high affinity" (29 degrees C for 1 hr) rosettes with sheep erythrocytes, and rosettes with EAC were determined. Lepromatous patients, compared with normal controls, had decreased "active" rosettes, standard rosettes, and "high affinity" rosettes with sheep erythrocytes with an increase in the nonrosetting proportion. Both lepromatous and borderline leprosy patients showed increased percentages of EAC rosettes compared with normal controls.