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Comparison of enzyme-linked immunosorbent and indirect immunofluorescence assays for the detection of human T-cell lymphotropic virus type-I antibodies in sera from rural Haiti
DIAGN MICROBIOL INFECT DIS 1992;15:121-124
121
VIROLOGY
Comparison of Enzyme-Linked Immunosorbent and Indirect Immunofluorescence Assays for the Detection of Human T-Cell Lymphotropic Virus Type-I Antibodies in Sera from Rural Haiti Wendy Grant, Frank J. Bia, Thomas M. Chacko, Michel Jean-Baptiste, and Brigitte P. Griffith
Serum samples were obtained from 340 healthy individuals without evidence of neurologic disease living in rural Haiti. Sera were screened for antibodies to human T-cell lymphotropic virus type I (HTLV-I) using two commercially available enzyme immunoassays (EIA) and by an indirect immunofluorescence assay (IFA) using a mixture of uninfected H9 cells and HTL V-I-infected MT-2 cells. Repeatedly positive samples
were confirmed by Western blot (WB). Results with the two EIA systems were concordant and detected 13 positive samples, each of which was confirmed by WB. Only 9 (69%) of 13 WB-positive sera were detected by IFA, and four additional samples, positive by IFA, could not be confirmed by WB. The prevalence of HTL V-I seropositivity in this selected rural Haitian population was 3.8% (13 of 340).
INTRODUCTION
I infection is endemic in s o u t h e r n Japan ( H i n u m a et al., 1985), the Caribbean (Catovsky et al., 1982), Africa ( H u n s m a n et al., 1984; Biggar et al., 1984; Verdier et al., 1989), and a m o n g some risk g r o u p s in United States (Robert-Guroff et al., 1986). Concerns about transmission of viruses t h r o u g h blood products have p r o m p t e d blood banks in the USA to screen blood d o n o r s for HTLV-I antibodies (Bove and Sandler, 1988). E n z y m e i m m u n o s o r b e n t assays (EIA) kits have recently b e e n licensed by the Food and Drug Administration (FDA) as screening tests for the detection of HTLV-I antibodies in US blood d o n o r s (CDC, 1988). Few studies have been published evaluating these assays (Gallo et al., 1988; Cossen et al., 1990). The indirect i m m u n o f l u o r e s cence assay (IFA) and EIAs have b e e n c o m p a r e d for the detection of HTLV-I antibodies in African sera (Verdier et al., 1990) a n d in blood b a n k donors, int r a v e n o u s d r u g abusers and h u m a n i m m u n o d e f i ciency virus antibody-positive individuals in the USA (Gallo et al., 1988). In a n o t h e r study, the performance of six HTLV-I EIA a n t i b o d y kits was com-
H u m a n T-cell l y m p h o t r o p i c virus type I (HTLV-I) has b e e n associated with adult T-cell l e u k e m i a - l y m p h o m a and with a progressive degenerative neurologic disease, referred to as tropical spastic paraparesis (TSP) in the Caribbean, or HTLV-I associated m y e l o p a t h y (HAM) in Japan (Blattner, 1989). HTLVFrom the Retrovirus Diagnostic Section, Virology Reference Laboratory, Veterans Affairs Medical Center (B.P.G., T.M.C.), West Haven; the Departments of Laboratory Medicine (W.G., F.J.B., B.P.G.) and Medicine (W.G., F.J.B.) Yale University School of Medicine, New Haven, Connecticut, USA; and Albert Schweitzer Hospital (M. J.-B.), Deschapelles, Haiti, West Indies. Presented at the 29th International Congress on Antimicrobial Agents and Chemotherapy, USA, 17-20 September 1989, Houston, Texas [abst 1167]. Address reprint requests to Dr. B.P. Griffith, Virology Reference Laboratory/151B,VA Medical Center, 950 Campbell Avenue, West Haven, CT 06516, USA. Received 31 January 1991; revised and accepted 2 April 1991. © 1992 Elsevier Science Publishing Co., Inc. 655 Avenue of the Americas, New York, NY 10010 0732-8893/92/$5.00
122
pared (Cossen et al., 1990). To our knowledge, there are no published data on the usefulness of these commercial kits for the detection of HTLV-I antibodies in individuals from the Caribbean. In the present study, we have compared an IFA test and two commercially available EIAs for their ability to detect HTLV-I antibodies in healthy individuals from Haiti.
W. Grant et al.
by IFA. Samples repeatedly positive by IFA were tested by WB.
Human Immunodeficiency Virus Type-1 (HIV-1) Antibody Testing Serum samples that were reactive in the HTLV-I antibody EIAs were also tested for the presence of HIV1 antibodies using EIA (Abbott Laboratories) and WB (BioRad Clinical Division, Hercules, CA).
MATERIALS AND METHODS Serum Collection Serum specimens were collected from 340 healthy individuals accompanying friends or family members to the Hopital Albert Schwitzer in Deschapelles (Haiti, West Indies) or to one of its seven outlying dispensaries in the central Artibonite Valley of Haiti. Samples were collected over a 2-month period from June through August 1988, when -15,000 outpatients were evaluated at the hospital and its dispensaries. Information regarding age, sex, geographic data, pertinent travel, and medical and sexual history was obtained from each subject. This study, however, was not designed to reliably assess sexual practices and risk factors that might be associated with acquisition of retroviral infections (Cymet, 1990). Of the 340 subjects, 122 (36%) were male and 218 (64%) were female. The age range was 15-76 years. The majority of subjects (327) were from the Artibonite Valley district served by the Hopital Albert Schweitzer and 13 were from outside the hospital district. The collected blood samples were centrifuged, and sera were kept frozen at the hospital until they were subsequently transported on dry ice to the Virology Reference Laboratory at the VA Medical Center in West Haven, Connecticut.
HTLV-I Antibody Testing All serum specimens were tested for antibody to HTLV-I using two EIA kits (Abbott Laboratories, Chicago, IL, and Du Pont de Nemours, Wilmington, DE) according to the manufacturers' directions. Samples that were initially reactive by EIA were retested with the same EIA kit, and repeatedly reactive samples were confirmed by Western blot (WB) analysis (Du Pont). For IFA, a mixture of uninfected H9 cells (originally obtained from Robert Gallo, National Cancer Institute, Bethesda, MD) and MT-2 cells, an HTLVI-transformed human T-cell line (kindly provided by Dana Gallo, State of California Department of Health Services, Berkeley, CA) was used. The preparation of slides and the IFA procedure were as described previously (Gallo et al., 1988). Samples that were found to be initially positive by IFA were retested
RESULTS Of the samples tested, 13 (3.8%) of 340 were found to be repeatedly reactive in each of the HTLV-I EIAs. Results for both EIAs were concordant, that is, the Du Pont and Abbott EIAs detected the same thirteen positive samples. By WB, all 13 serum samples met established criteria for positivity, reacting with both gag p24 and env gp46 HTLV-I proteins (Figure 1A). To detect cross-reactivity or coinfection with HIV-1, all HTLV-I antibody positive samples were tested for the presence of HIV-1 antibody by ELISA and WB (Figure 1B). A single patient (no. 320) was found to be repeatedly reactive in the HIV-1 EIA. This sample was confirmed to be HIV-1 antibody positive by WB. Some of the HIV-l-negative, HTLV-I-positive sera showed reactivity at the p24 and p56 levels in the HIV-1 WB. Thirteen sera were repeatedly reactive in the HTLV-I IFA assay. Only nine (69%) of these 13 IFA-positive samples were concordant with those detected by the EIAs and WB assays. Four WB-positive samples (nos. 62, 99, 179, and 305) were IFA negative. The other four IFA-positive samples showed no bands on WB. The overall prevalence of HTLV-I antibodies was 3.8% in this selected population of rural Haitians. The rate for men was two (1.6%) of 122, and the rate for w o m e n was 11 (5.1%) of 218. For the most rural dispensaries, Laincourt, Bastien, and several others, the rates were three (2.8%) of 109, one (2.2%) of 45, and zero (0%) of 12, respectively. In the towns of Petite Riviere and Deschapelles, rates were five (4.2%) of 120 and two (5.1%) of 39. Although only 15 patients sampled were from larger towns and cities such as Port-au-Prince, St. Marc, and Gonaives, two samples (13.3%) were positive. In the age group ranging from age 15 to 64 years, the seroprevalence was 11 (3.4%) of 323. In the older population available for study (---65 years), the rate of seroprevalence was two (11.8%) of 17, even though the proportion of w o m e n in this group was slightly less than that of the entire study group (65% vs 69%).
DISCUSSION In the present study, EIAs were found to be superior to IFA for the detection of HTLV-I antibodies in in-
HTLV-I Antibody Assays on Sera from Rural Haiti
E
A
,3
123
O
o
(1)
~
Z
C..)
O
(3_
Z
6
23
25
49
62 99 104 179 184 187 269 305 320
gp 4 6 p 36
p 28 p24 p19
B gp 160-gp 120--
23 i
25
49
62
99
104 179 184 187 269 305:320
i
p 6 5 -p 55-gp41p32-- I p24-
I
II
plS--
!¸ii~J!~i i ii i!' i ~~
FIGURE 1 Western blot analysis of serum samples repeatedly reactive in EIAs: (A) reactivity to HTLV-I proteins and (B) reactivity to HIV-1 proteins. dividuals from an endemic area in the Caribbean. The HTLV-I WB of sera from these asymptomatic HTLV-I-infected individuals were not difficult to interpret because the majority exhibited reactivity to gag p19, p24, p53, and env gp 46. In contrast to what has been suggested for confirmation of the presence of HTLV-I antibodies in samples from the USA (CDC, 1988), evaluation of samples by radioimmunoprecipitation was not required in our population. The IFA method has been reported to be more sensitive than the EIA in detecting antibodies to HTLV-I in samples obtained from California intravenous drug abusers (Gallo et al., 1988). In a recent study of African sera (Verdier et al., 1990), however, EIAs were more sensitive and specific than IFAs, which were also found to be difficult to read and interpret. Sera obtained from HTLV-I endemic areas may differ in their reactivity in IFAs. False-positive IFAs could be due to cross-reactive antibodies, and circulating immune complexes due to parasitic infections, as suggested for HIV-1 (Biggar et al., 1985).
In the present study, all IFA-positive samples exhibited diffuse staining. This pattern has been reported before to be associated with high EIA ratios and multiple bands on WB (Gallo et al., 1988). Four of our IFA-positive samples were found to be WB negative. Four of our WB-positive samples were found to be IFA negative. Two of these samples (nos. 99 and 179) had bands present in low number and reduced intensity. However, samples 62 and 305 were IFA negative despite the presence of numerous and intense bands on WB. The prevalence of HTLV-I antibodies in this selected Haitian population is similar to that reported for populations in Jamaica, Barbados, and blacks in Trinidad (Newton et al., 1987; Riedel et al., 1989). Our data differ from those obtained by Giordano et al. (1989) in their study of selected urban population groups from Port-au-Prince. The seroprevalence of HTLV-I infection in their study was 8.3% (256 of 3078), of which a large proportion (71%) were coinfected with HIV-1. The highest infection rates for
124
HTLV-I were in AIDS patients (13.9%), prostitutes (12.4%), and spouses of AIDS patients (8.4%). The lower seroprevalence rates in our s t u d y p o p u l a t i o n probably reflect differences in social and sexual risk factors b e t w e e n u r b a n and rural agrarian societies, but we are unable to address such issues on the basis of this study. The seroprevalence rates for w o m e n from rural Haiti were more than three times greater than those for m e n in our s t u d y (5.1% vs 1.6%). Similarly, an analysis of sera obtained in Barbados s h o w e d that the seropositivity rate for w o m e n and m e n were 5.7% and 2.2%, respectively (Riedel et al., 1989). In contrast, other investigators did not demonstrate a g e n d e r difference for seroprevalence of HTLV-I antibodies in either Ivory Coast or G h a n a (Biggar et al., 1984; Verdier et al., 1989). Verdier et al. (1989) p e r f o r m e d a seroepidemiologic s u r v e y of 3177 residents of Ivory Coast, Africa for antibodies to HTLV-I. Seropositivity increased with age. Our data suggest a similar trend in rural Haiti, but the n u m b e r of patients age 65 or greater, available for this study, was too small for statistical comparison. Also, this s t u d y is biased with regard to the s t u d y population of the Artibonite River Valley, as the
W. Grant et al.
presence of the Schweitzer Hospital, its dispensaries, and public health p r o g r a m s has significantly altered health care in relation to the r e m a i n d e r of Haiti over the past 25 years. The same 13 HTLV-I-seropositive samples were correctly identified in this healthy g r o u p of 340 Haitian individuals b y two of the FDA-licensed EIA kits available for the detection of HTLV-I antibodies and were confirmed by WB analysis. O u r data do not s u p p o r t the notion that IFA can be used for the detection or confirmation of HTLV-I antibodies in serum samples from this e n d e m i c area. O u r results cannot be extrapolated to the Haitian p o p u l a t i o n at large. T h e y r e p r e s e n t data obtained from a selected samples of healthy patients in one rural area of Haiti.
This work was supported in part by a Wilbur Downs Fellowship in International Health, Yale University School of Medicine (WG). Informed consent was obtained from all subjects in this study according to HIC Protocol 4773, Yale School of Medicine, and the Human Investigation Committee of the HopitaI Albert Schweitzer.
REFERENCES Biggar RJ, Saxinger C, Gardiner C, et al., (1984). Type I HTLV antibody in urban and rural Ghana, West Africa. Int J Cancer 34:215. Biggar RJ, Gigase PL, Melbye M (1985) ELISA HTLV retrovirus antibody reactivity associated with malaria and immune complexes in healthy Africans. Lancet 2:520. Blattner W (1989) Retroviruses. In Viral Infections of Humans: Epidemiology and Control, 3d ed. Ed, AS Evans. New York: Plenum, pp 545-592. Bove JR, Sandler SG (1988) HTLV-I and blood transfusion. Transfusion 28:93. Catovsky D, Greaves MF, Rose M, et al. (1982) Adult Tcell lymphoma-leukemia in blacks from the West Indies. Lancet 1:639. CDC (1988) Licensure of screening tests for antibody to human T-lymphotropic virus type I. M M W R 37:736. Cossen C, Hagens S, Fukuchi R, Forghani B, Wilber J, Asche M (1990) Comparative performance of six HTLVI EIA antibody kits. Abstract of the 5th Consensus Conference on Testing for Human Retroviruses, Kansas City. Cymet TC (1990) The spread of AIDS in the Haitan-American population: a cultural perspective. Osteopath Med News 7:11. Gallo D, Hoffman MN, Cossen CK, Diggs JL, Hurst JW, Penning LM (1988) Comparison of immunofluorescence, enzyme immunoassay and Western blot methods for detection of antibody to human T-cell leukemia virus type I. J Clin Microbiol 26:1487. Giordano M, Pape J, Blattner W, Johnson WD (1989) The
seroprevalence of HTLV-I and HIV-1 co-infection in Haiti [abst MGP3]. In Abstracts of the 5th International Conference on AIDS, Montreal, p 998. Hinuma Y, Komoda H, Chosa T, et al. (1985). Antibodies to adult T-cell leukemia-virus-associated antigen (ATLA) in sera from patients with ATL and controls in Japan: a nation-wide seroepidemiologic study. Int J Cancer 29:631. Hunsman G, Bayer H, Schneider J, et al. (1984) Antibodies to ATLV-HTLV-I in Africa. Med Microbiol Immunol (BerI) 173:167. Newton M, Cruickshank K, Miller D, et al. (1987) Antibody to human T-lymphotropic virus type I in WestIndian-born UK residents with spastic paraparesis. Lancet 1:415. Riedel DA, Evans AS, Saxinger, C, Blattner WA (1989) A historical study of human T lymphotropic virus type I transmission in Barbados. J Infect Dis 159:603. Robert-Guroff M, Weiss S, Giron J, et al. (1986) Prevalence of antibodies to HTLV-I, II and III in intravenous drug abusers from an AIDS endemic region, l A M A 255:3133. Verdier M, Denis F, Sangare A, et al. (1989) Prevalence of antibody to human T-cell leukemia virus type I (HTLVI) in populations of Ivory Coast, West Africa. J Infect Dis 160:363. Verdier M, Denis F, Leonard G, et al. (1990) Comparison of immunofluorescence, particle agglutination, and enzyme immunoassays for detection of human T-cell leukemia virus type I antibody in African sera. J Clin Microbiol 28:1988.
121
VIROLOGY
Comparison of Enzyme-Linked Immunosorbent and Indirect Immunofluorescence Assays for the Detection of Human T-Cell Lymphotropic Virus Type-I Antibodies in Sera from Rural Haiti Wendy Grant, Frank J. Bia, Thomas M. Chacko, Michel Jean-Baptiste, and Brigitte P. Griffith
Serum samples were obtained from 340 healthy individuals without evidence of neurologic disease living in rural Haiti. Sera were screened for antibodies to human T-cell lymphotropic virus type I (HTLV-I) using two commercially available enzyme immunoassays (EIA) and by an indirect immunofluorescence assay (IFA) using a mixture of uninfected H9 cells and HTL V-I-infected MT-2 cells. Repeatedly positive samples
were confirmed by Western blot (WB). Results with the two EIA systems were concordant and detected 13 positive samples, each of which was confirmed by WB. Only 9 (69%) of 13 WB-positive sera were detected by IFA, and four additional samples, positive by IFA, could not be confirmed by WB. The prevalence of HTL V-I seropositivity in this selected rural Haitian population was 3.8% (13 of 340).
INTRODUCTION
I infection is endemic in s o u t h e r n Japan ( H i n u m a et al., 1985), the Caribbean (Catovsky et al., 1982), Africa ( H u n s m a n et al., 1984; Biggar et al., 1984; Verdier et al., 1989), and a m o n g some risk g r o u p s in United States (Robert-Guroff et al., 1986). Concerns about transmission of viruses t h r o u g h blood products have p r o m p t e d blood banks in the USA to screen blood d o n o r s for HTLV-I antibodies (Bove and Sandler, 1988). E n z y m e i m m u n o s o r b e n t assays (EIA) kits have recently b e e n licensed by the Food and Drug Administration (FDA) as screening tests for the detection of HTLV-I antibodies in US blood d o n o r s (CDC, 1988). Few studies have been published evaluating these assays (Gallo et al., 1988; Cossen et al., 1990). The indirect i m m u n o f l u o r e s cence assay (IFA) and EIAs have b e e n c o m p a r e d for the detection of HTLV-I antibodies in African sera (Verdier et al., 1990) a n d in blood b a n k donors, int r a v e n o u s d r u g abusers and h u m a n i m m u n o d e f i ciency virus antibody-positive individuals in the USA (Gallo et al., 1988). In a n o t h e r study, the performance of six HTLV-I EIA a n t i b o d y kits was com-
H u m a n T-cell l y m p h o t r o p i c virus type I (HTLV-I) has b e e n associated with adult T-cell l e u k e m i a - l y m p h o m a and with a progressive degenerative neurologic disease, referred to as tropical spastic paraparesis (TSP) in the Caribbean, or HTLV-I associated m y e l o p a t h y (HAM) in Japan (Blattner, 1989). HTLVFrom the Retrovirus Diagnostic Section, Virology Reference Laboratory, Veterans Affairs Medical Center (B.P.G., T.M.C.), West Haven; the Departments of Laboratory Medicine (W.G., F.J.B., B.P.G.) and Medicine (W.G., F.J.B.) Yale University School of Medicine, New Haven, Connecticut, USA; and Albert Schweitzer Hospital (M. J.-B.), Deschapelles, Haiti, West Indies. Presented at the 29th International Congress on Antimicrobial Agents and Chemotherapy, USA, 17-20 September 1989, Houston, Texas [abst 1167]. Address reprint requests to Dr. B.P. Griffith, Virology Reference Laboratory/151B,VA Medical Center, 950 Campbell Avenue, West Haven, CT 06516, USA. Received 31 January 1991; revised and accepted 2 April 1991. © 1992 Elsevier Science Publishing Co., Inc. 655 Avenue of the Americas, New York, NY 10010 0732-8893/92/$5.00
122
pared (Cossen et al., 1990). To our knowledge, there are no published data on the usefulness of these commercial kits for the detection of HTLV-I antibodies in individuals from the Caribbean. In the present study, we have compared an IFA test and two commercially available EIAs for their ability to detect HTLV-I antibodies in healthy individuals from Haiti.
W. Grant et al.
by IFA. Samples repeatedly positive by IFA were tested by WB.
Human Immunodeficiency Virus Type-1 (HIV-1) Antibody Testing Serum samples that were reactive in the HTLV-I antibody EIAs were also tested for the presence of HIV1 antibodies using EIA (Abbott Laboratories) and WB (BioRad Clinical Division, Hercules, CA).
MATERIALS AND METHODS Serum Collection Serum specimens were collected from 340 healthy individuals accompanying friends or family members to the Hopital Albert Schwitzer in Deschapelles (Haiti, West Indies) or to one of its seven outlying dispensaries in the central Artibonite Valley of Haiti. Samples were collected over a 2-month period from June through August 1988, when -15,000 outpatients were evaluated at the hospital and its dispensaries. Information regarding age, sex, geographic data, pertinent travel, and medical and sexual history was obtained from each subject. This study, however, was not designed to reliably assess sexual practices and risk factors that might be associated with acquisition of retroviral infections (Cymet, 1990). Of the 340 subjects, 122 (36%) were male and 218 (64%) were female. The age range was 15-76 years. The majority of subjects (327) were from the Artibonite Valley district served by the Hopital Albert Schweitzer and 13 were from outside the hospital district. The collected blood samples were centrifuged, and sera were kept frozen at the hospital until they were subsequently transported on dry ice to the Virology Reference Laboratory at the VA Medical Center in West Haven, Connecticut.
HTLV-I Antibody Testing All serum specimens were tested for antibody to HTLV-I using two EIA kits (Abbott Laboratories, Chicago, IL, and Du Pont de Nemours, Wilmington, DE) according to the manufacturers' directions. Samples that were initially reactive by EIA were retested with the same EIA kit, and repeatedly reactive samples were confirmed by Western blot (WB) analysis (Du Pont). For IFA, a mixture of uninfected H9 cells (originally obtained from Robert Gallo, National Cancer Institute, Bethesda, MD) and MT-2 cells, an HTLVI-transformed human T-cell line (kindly provided by Dana Gallo, State of California Department of Health Services, Berkeley, CA) was used. The preparation of slides and the IFA procedure were as described previously (Gallo et al., 1988). Samples that were found to be initially positive by IFA were retested
RESULTS Of the samples tested, 13 (3.8%) of 340 were found to be repeatedly reactive in each of the HTLV-I EIAs. Results for both EIAs were concordant, that is, the Du Pont and Abbott EIAs detected the same thirteen positive samples. By WB, all 13 serum samples met established criteria for positivity, reacting with both gag p24 and env gp46 HTLV-I proteins (Figure 1A). To detect cross-reactivity or coinfection with HIV-1, all HTLV-I antibody positive samples were tested for the presence of HIV-1 antibody by ELISA and WB (Figure 1B). A single patient (no. 320) was found to be repeatedly reactive in the HIV-1 EIA. This sample was confirmed to be HIV-1 antibody positive by WB. Some of the HIV-l-negative, HTLV-I-positive sera showed reactivity at the p24 and p56 levels in the HIV-1 WB. Thirteen sera were repeatedly reactive in the HTLV-I IFA assay. Only nine (69%) of these 13 IFA-positive samples were concordant with those detected by the EIAs and WB assays. Four WB-positive samples (nos. 62, 99, 179, and 305) were IFA negative. The other four IFA-positive samples showed no bands on WB. The overall prevalence of HTLV-I antibodies was 3.8% in this selected population of rural Haitians. The rate for men was two (1.6%) of 122, and the rate for w o m e n was 11 (5.1%) of 218. For the most rural dispensaries, Laincourt, Bastien, and several others, the rates were three (2.8%) of 109, one (2.2%) of 45, and zero (0%) of 12, respectively. In the towns of Petite Riviere and Deschapelles, rates were five (4.2%) of 120 and two (5.1%) of 39. Although only 15 patients sampled were from larger towns and cities such as Port-au-Prince, St. Marc, and Gonaives, two samples (13.3%) were positive. In the age group ranging from age 15 to 64 years, the seroprevalence was 11 (3.4%) of 323. In the older population available for study (---65 years), the rate of seroprevalence was two (11.8%) of 17, even though the proportion of w o m e n in this group was slightly less than that of the entire study group (65% vs 69%).
DISCUSSION In the present study, EIAs were found to be superior to IFA for the detection of HTLV-I antibodies in in-
HTLV-I Antibody Assays on Sera from Rural Haiti
E
A
,3
123
O
o
(1)
~
Z
C..)
O
(3_
Z
6
23
25
49
62 99 104 179 184 187 269 305 320
gp 4 6 p 36
p 28 p24 p19
B gp 160-gp 120--
23 i
25
49
62
99
104 179 184 187 269 305:320
i
p 6 5 -p 55-gp41p32-- I p24-
I
II
plS--
!¸ii~J!~i i ii i!' i ~~
FIGURE 1 Western blot analysis of serum samples repeatedly reactive in EIAs: (A) reactivity to HTLV-I proteins and (B) reactivity to HIV-1 proteins. dividuals from an endemic area in the Caribbean. The HTLV-I WB of sera from these asymptomatic HTLV-I-infected individuals were not difficult to interpret because the majority exhibited reactivity to gag p19, p24, p53, and env gp 46. In contrast to what has been suggested for confirmation of the presence of HTLV-I antibodies in samples from the USA (CDC, 1988), evaluation of samples by radioimmunoprecipitation was not required in our population. The IFA method has been reported to be more sensitive than the EIA in detecting antibodies to HTLV-I in samples obtained from California intravenous drug abusers (Gallo et al., 1988). In a recent study of African sera (Verdier et al., 1990), however, EIAs were more sensitive and specific than IFAs, which were also found to be difficult to read and interpret. Sera obtained from HTLV-I endemic areas may differ in their reactivity in IFAs. False-positive IFAs could be due to cross-reactive antibodies, and circulating immune complexes due to parasitic infections, as suggested for HIV-1 (Biggar et al., 1985).
In the present study, all IFA-positive samples exhibited diffuse staining. This pattern has been reported before to be associated with high EIA ratios and multiple bands on WB (Gallo et al., 1988). Four of our IFA-positive samples were found to be WB negative. Four of our WB-positive samples were found to be IFA negative. Two of these samples (nos. 99 and 179) had bands present in low number and reduced intensity. However, samples 62 and 305 were IFA negative despite the presence of numerous and intense bands on WB. The prevalence of HTLV-I antibodies in this selected Haitian population is similar to that reported for populations in Jamaica, Barbados, and blacks in Trinidad (Newton et al., 1987; Riedel et al., 1989). Our data differ from those obtained by Giordano et al. (1989) in their study of selected urban population groups from Port-au-Prince. The seroprevalence of HTLV-I infection in their study was 8.3% (256 of 3078), of which a large proportion (71%) were coinfected with HIV-1. The highest infection rates for
124
HTLV-I were in AIDS patients (13.9%), prostitutes (12.4%), and spouses of AIDS patients (8.4%). The lower seroprevalence rates in our s t u d y p o p u l a t i o n probably reflect differences in social and sexual risk factors b e t w e e n u r b a n and rural agrarian societies, but we are unable to address such issues on the basis of this study. The seroprevalence rates for w o m e n from rural Haiti were more than three times greater than those for m e n in our s t u d y (5.1% vs 1.6%). Similarly, an analysis of sera obtained in Barbados s h o w e d that the seropositivity rate for w o m e n and m e n were 5.7% and 2.2%, respectively (Riedel et al., 1989). In contrast, other investigators did not demonstrate a g e n d e r difference for seroprevalence of HTLV-I antibodies in either Ivory Coast or G h a n a (Biggar et al., 1984; Verdier et al., 1989). Verdier et al. (1989) p e r f o r m e d a seroepidemiologic s u r v e y of 3177 residents of Ivory Coast, Africa for antibodies to HTLV-I. Seropositivity increased with age. Our data suggest a similar trend in rural Haiti, but the n u m b e r of patients age 65 or greater, available for this study, was too small for statistical comparison. Also, this s t u d y is biased with regard to the s t u d y population of the Artibonite River Valley, as the
W. Grant et al.
presence of the Schweitzer Hospital, its dispensaries, and public health p r o g r a m s has significantly altered health care in relation to the r e m a i n d e r of Haiti over the past 25 years. The same 13 HTLV-I-seropositive samples were correctly identified in this healthy g r o u p of 340 Haitian individuals b y two of the FDA-licensed EIA kits available for the detection of HTLV-I antibodies and were confirmed by WB analysis. O u r data do not s u p p o r t the notion that IFA can be used for the detection or confirmation of HTLV-I antibodies in serum samples from this e n d e m i c area. O u r results cannot be extrapolated to the Haitian p o p u l a t i o n at large. T h e y r e p r e s e n t data obtained from a selected samples of healthy patients in one rural area of Haiti.
This work was supported in part by a Wilbur Downs Fellowship in International Health, Yale University School of Medicine (WG). Informed consent was obtained from all subjects in this study according to HIC Protocol 4773, Yale School of Medicine, and the Human Investigation Committee of the HopitaI Albert Schweitzer.
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