Impaired antibody response after immunization of HIV-infected individuals with the polysaccharide vaccine against Salmonella typhi (Typhim-Vi®)

Infections with Salmonella species, including Salmonella typhi, are more frequently observed in HIV-infected individuals than in healthy individuals. HIV-infected individuals were vaccinated with polysaccharide vaccine against Salmonella typhi (Typhim-Vi®) which is assumed to be a T-cell-independent antigen. We found that the antibody response in patients with <200×10⁶/l CD4⁺ T lymphocytes was significantly lower compared with patients with ≥200×10⁶/l CD4⁺ T lymphocytes and healthy controls. The antibody response after vaccination with the polysaccharide salmonella Vi-antigen was correlated with the number of CD4⁺ T lymphocytes and therefore Typhim-Vi can be considered to be a T-cell-independent type 2 antigen. The results of this study indicate that after vaccination the proportion of HIV-infected individuals with protective antibody concentrations against Salmonella typhi will be lower than in healthy controls.     

Enhanced antibody response to pneumococcal polysaccharide vaccine after prior immunization with conjugate pneumococcal vaccine in HIV-infected adults

The antibody production by HIV-infected adults after two vaccinations with conjugated pneumococcal vaccine (CPV) and consecutive vaccination with polysaccharide pneumococcal vaccine (PPV) was studied. Thirty days after the second CPV, the geometric mean antibody concentrations (GMC) against pneumococcal polysaccharide serotypes (PPS) 6B, 14 and 19F were significantly lower in the group HIV-infected individuals with <200x10(6)/l CD4(+) T lymphocytes (group 1) than in the group with >/=200x10(6)/l CD4(+) T lymphocytes (group 2) and healthy controls. Thirty days after PPV vaccination the GMC against PPS 6B, 14, 19F and 23F in group 1, and against 6B and 19F in group 2, were significantly lower compared with healthy controls. Both in HIV-infected and in healthy individuals who received CPV and PPV the postvaccination GMC against PPS 14, 19F and 23F were higher compared with historical controls who were not previously immunized with CPV but only received PPV. We conclude that the antibody response to CPV is impaired in HIV-infected individuals. Higher antibody concentrations were achieved in HIV-infected and healthy individuals after sequential vaccination with CPV and PPV compared with PPV vaccination alone.     

Antibodies against pneumococcal polysaccharides after vaccination in HIV-infected individuals: 5-year follow-up of antibody concentrations.

We studied the production of IgG antibodies against eight pneumococcal polysaccharide serotypes (PPS) 1, 4, 6B, 9V, 14, 18C, 19F and 23F after vaccination of 50 HIV-infected adults with 23-valent Pneumovax((R))23 and the course of the antibodies against four PPS during the following years. Mean antibody concentrations against PPS 18C, 19F and 23F were sigificantly lower in the patients with CD4(+)-lymphocyte counts <200x10(6)/l than in healthy controls; mean antibody concentrations against PPS 1, 4, 9V, 6B and 14 were similar in HIV-infected individuals and controls. Although it has been assumed that polysaccharides induce a T-cell-independent immune response, our results indicate that some PPS are T-cell-independent type 2 antigens. The rates of decline of mean antibody concentrations in HIV-infected individuals and in healthy controls were similar during 5 y after vaccination. However, as a consequence of the low postvaccination antibody concentrations against several PPS, within 3 y after vaccination most HIV-infected individuals had antibody concentrations below the level which is assumed to be required for protection.     

Antibody response after influenza vaccination in HIV-infected individuals: a consecutive 3-year study

In a consecutive 3-year study the antibody response after immunization with influenza vaccine of a cohort of HIV-infected adults was studied. The haemagglutination-inhibiting (HAI) antibody titres after vaccination correlated with the number of CD4(+) T lymphocytes (p<0.001), the prevaccination antibody titres (p<0.001), and the proliferative response to anti-CD3 (p<0.001). Severely impaired antibody responses were observed in HIV-infected individuals with CD4(+) T-lymphocyte counts < or =100x10(6)/l. Significantly higher prevaccination antibody titres were observed in healthy controls in the 2nd or 3rd year of vaccination, but not in HIV-infected individuals. Annually repeated vaccination of HIV-infected individuals did not lead to higher postvaccination antibody titres. Annual vaccination of HIV-infected individuals with CD4(+) T-lymphocyte counts exceeding 100x10(6)/l seems to be worthwhile, although it may not be expected to render the same level of protection against influenza as in non-infected individuals.     

Decreased ratio of influenza-specific IgG versus IgM in response to influenza vaccination in antiretroviral-treated HIV-infected African Americans compared to Caucasians,and its direct correlation with the percentages of peripheral Tfh cells

BackgroundRacial differences have been observed in the rate of bacterial infection and disease progression in HIV. Here, we evaluate racial differences in seasonal influenza vaccine responses.Methods16 healthy controls (9 Caucasians (CC) and 7 African Americans (AA)) and 26 antiretroviral therapy (ART)-treated aviremic HIV+ subjects (11 CC and 15 AA) were enrolled in the current study. Blood was collected at pre-vaccination (D0) and day 14 (D14) following seasonal influenza vaccination. Serologic responses were characterized in plasma by ELISA. B and T cells were assessed by flow cytometry ex vivo.ResultsThe absolute counts of CD4+ CD3+ T cells and CD19+ B cells were similar in healthy controls and HIV-infected individuals, and similar in CC and AA in the two study groups. However, the percentage of peripheral T follicular helper (pTfh) cells was decreased in HIV+ AA compared to HIV+ CC. There were no racial differences in IgG antibody responses against vaccination in the two study groups. However, the ratio of anti-influenza-specific IgG versus IgM induction following vaccination was decreased in HIV+ AA compared to HIV+ CC, which was directly correlated with the percentages of pTfh cells. This racial difference and correlation were not demonstrable in healthy controls.ConclusionHere we report that HIV + AA has decreased fold induction of IgG versus IgM after influenza vaccination, which may suggest impaired class-switching from IgM to IgG in AA HIV-infected individuals.     

HIV-1感染者CD8+T细胞受体基因多样性特点及其与病毒载量的相关性

目的 研究HIV-1感染者CD8+T细胞受体(TCR)基因的多样性变化特征及其与病毒载量的相关性.方法 应用抗CD8单克隆抗体从9份HIV-1感染者和7份HIV-1阴性对照样本外周血单个核细胞中分离CD8+T细胞,提取总RNA,然后采用一步(one step)及巢式(nested)多聚酶链式反应(PCR)的方法对22个T细胞受体Vβ基因家族的瓦补决定区3(CDR3)进行扩增,利用ABI-3700测序仪对扩增的PCR产物进行扣描,定量分析HIV-1感染者TCR CDR3区多样性变化特征及其与病毒载量的相关性.结果 HIV-1感染者和正常人相比较其CD8+T细胞的TCR基因多样性明显减少,部分TCR Vβ基因家族CDR3区的高斯分布破坏;TCR的紊乱与病毒载量呈正相关(r=0.771,P<0.05);HIV-1感染引起患者TCR多样性的改变不仅表现在不同Vβ基因家族上,而且也表现在CDR3长度上,其中感染者VB2、Vβ4、Vβ5、Vβ17、Vβ20、Vβ21、Vβ23及Vβ24基因家族的变化与正常人存在统计学差异.结论 HIV-1感染能引起CD8+T细胞TCR基因多样性的减少及高斯分布的破坏,TCR CDR3区的紊乱与病毒载量呈正相关.     

The induction of CD80 and apoptosis on B cells and CD40L in CD4+ T cells in response to seasonal influenza vaccination distinguishes responders versus non-responders in healthy controls and aviremic ART-treated HIV-infected individuals

BackgroundStudies have shown that HIV infection is associated with an impaired influenza vaccine response. We examined the role of cellular phenotypes and function in influenza vaccine responsiveness in healthy controls and aviremic HIV-infected subjects on antiretroviral treatment (ART).Methods16 healthy controls and 26 ART+ aviremic HIV+ subjects were enrolled in the current study. Blood was collected at pre-vaccination (D0), and on days 7–10 (D7) and 14–21 (D14) following the 2013–2014 seasonal influenza vaccine administrations. Subjects were classified as responders if neutralizing titers against H1N1 virus increased ⩾4-fold at D14 compared to D0. A serial analysis of B and CD4+ T cell frequencies and activation was performed on D0 and D7 by flow cytometry.Results9 of 26 (34.6%) HIV-infected individuals and 7 of 16 (43.8%) healthy controls were classified as responders to influenza vaccines. Total B cell apoptosis (annexin V) was increased on D7 post-vaccination in non-responders but not in responders among both controls and HIV+ subjects. Surface CD80 expression on memory B cells and intracellular CD40L expression on memory CD4+ T cells were induced on D7 in responders of controls but not in non-responders. The CD80 and CD40L induction was not demonstrable in HIV-infected subjects regardless of responders and non-responders. Memory CD4+ T cell cycling tended to increase on D7 in the four study groups but did not achieve significance. All the other parameters were indistinguishable between responders and non-responders, regardless of HIV-infection status.ConclusionThe perturbation of activation and apoptotic induction on B cells or CD4+ T cells after seasonal influenza vaccination in non-responders and HIV-infected subjects may help understand the mechanism of impaired vaccine responsiveness.     

Immunologic and virologic response after tetanus toxoid booster among HIV-1- and HIV-2-infected Senegalese individuals.

Twelve HIV-1-infected, nine HIV-2-infected patients and eight HIV-negative subjects were given a 40IU booster dose of tetanus toxoid (TT). Blood was collected on days 0, 7 and 30 after immunization. Changes in HIV-1 or HIV-2 RNA load were evaluated by nested PCR. TT-IgG antibody levels were quantified by ELISA. CD4 cell counts as well as activation, memory and maturation markers of T lymphocyte subsets were determined by flow cytometry. The induction of apoptosis was investigated using 7-aminoactinomycin D (AAD) and propidium iodide (PI) staining. Proliferative responses to TT and pokeweed mitogen (PWM) were determined by the level of [(3)H] thymidine incorporation. Seven and 30 days after immunization, there was no detectable increase in HIV-1 or HIV-2 plasma load. There were also no changes in CD4 cell counts, CD69, HLA-DR and memory CD45RO or naive CD45RA antigens. Immunization did not increase the spontaneous apoptosis of peripheral blood mononuclear cells (PBMCs), CD4+ and CD8+ T cells subsets neither in controls nor in HIV-infected patients. Similarly, apoptosis induced in vitro by PWM or by the specific TT recall antigen did not vary during the study period. The proliferative response to PWM and to the TT recall antigen was decreased both in HIV-1- and HIV-2-infected patients compared to HIV-negative controls. Immunization significantly increased the TT-IgG levels in healthy controls and in HIV-infected patients. However, the anti-TT-IgG response, as measured by the fold-increase index between days 0 and 30, was significantly higher in healthy controls than in HIV-1- (P=0.036) and HIV-2-infected patients (P=0.003). In conclusion, we found no deleterious immunologic or virologic effect was detected in healthy HIV-1- and HIV-2-infected individuals after antigenic challenge with a TT booster. However, the response to TT vaccination was lower in HIV-1- and in HIV-2-infected individuals than in healthy HIV-negative controls.     

One dose of an MF59-adjuvanted pandemic A/H1N1 vaccine recruits pre-existing immune memory and induces the rapid rise of neutralizing antibodies

Protective antibody responses to a single dose of 2009 pandemic vaccines have been observed in the majority of healthy subjects aged more than 3 years. These findings suggest that immune memory lymphocytes primed by previous exposure to seasonal influenza antigens are recruited in the response to A/H1N1 pandemic vaccines and allow rapid seroconversion. However, a clear dissection of the immune memory components favoring a fast response to pandemic vaccination is still lacking. Here we report the results from a clinical study where antibody, CD4+ T cell, plasmablast and memory B cell responses to one dose of an MF59-adjuvanted A/H1N1 pandemic vaccine were analyzed in healthy adults. While confirming the rapid appearance of antibodies neutralizing the A/H1N1 pandemic virus, we show here that the response is dominated by IgG-switched antibodies already in the first week after vaccination. In addition, we found that vaccination induces the rapid expansion of pre-existing CD4+ T cells and IgG-memory B lymphocytes cross-reactive to seasonal and pandemic A/H1N1 antigens. These data shed light on the different components of the immune response to the 2009 H1N1 pandemic influenza vaccination and may have implications in the design of vaccination strategies against future influenza pandemics.     

Early-life and contemporaneous nutritional and environmental predictors of antibody response to vaccination in young Gambian adults

Recent research links nutritional exposures early in life with alterations in functional immunity that persist beyond childhood. Here we investigate predictors of antibody response to polysaccharide vaccines in a cohort of Gambian adults with detailed records from birth and early infancy available. 320 adults were given a single dose of a Vi polysaccharide vaccine for Salmonella typhi and a 23-valent capsular polysaccharide pneumococcal vaccine. Anti-Vi antibody levels and antibodies against 4 pneumococcal serotypes (1, 5, 14 and 23F) were measured in serum samples collected at baseline and then 14 days following vaccination and compared to data available from birth and early infancy. Post-vaccination antibody titres to serotype 14 of the pneumococcal vaccine were negatively associated with rate of growth from birth to three months of age, infant weight at 12 months of age and season of birth, but no other associations were observed with early-life exposures. The strongest predictor of antibody levels was pre-vaccination antibody titres, with adult height and serum neopterin levels at time of vaccination also implicated. The current study does not support the hypothesis that nutritional exposures early in life consistently compromise antibody response to polysaccharide vaccines administered in young adulthood.     

Safety and immunogenicity of 23-valent pneumococcal polysaccharide vaccine in HIV-1 infected former drug users

The immunogenicity of 23-valent pneumococcal polysaccharide vaccine was assessed in 57 HIV-1 infected former intravenous drug users and in 20 HIV-1 negative controls. The effect of vaccination on HIV-1 infection was studied in a subgroup of 38 patients, 60% of whom under highly active antiretroviral therapy (HAART). Antibody to capsular polysaccharides from Streptococcus pneumoniae serotypes 3, 4, 6B, 19F, 23 F, and changes in CD4+ count, HIV-1 RNA, proviral DNA and HIV-1 phenotype were measured in pre- and post-vaccination samples.Vaccinations were well-tolerated. The rate of responders was higher (P<0.05) in HIV-1 negative than in HIV-1 infected individuals. No difference in antibody response was found within HIV-1 infected patients stratified according to CD4+ counts. Post-vaccination antibody geometric mean concentrations (GMCs) to the five antigens were higher (P<0.05) than baseline in HIV-1 negative subjects, but not in HIV-1 positive individuals. Those with CD4+ >500 cells/mm(3) showed a significant increase of antibody against type 3 only. Immunisation caused no significant changes in CD4+ counts and in either plasma HIV-1 RNA nor proviral DNA levels. Pneumococcal vaccination does not induce virological or immunological deterioration in HIV infected patients, but the antibody response to a single dose of vaccine is poor.     

Antigen-specific activation and proliferation of CD4+ and CD8+ T lymphocytes from brucellosis patients

Salt-extractable antigen from Brucella melitensis 16M (RCM-BM) was used to evaluate the immune response from acute and chronic patients suffering from Brucella infections (in Mexico); their responses were compared with those of healthy controls. As a readout we used upregulation of CD69 (a well-established early activation marker for lymphocytes), lymphocyte proliferation by 3[H]thymidine or 5-bromo-2-deoxyuridine (BrdU) incorporation measured by liquid scintillation or flow cytometry, respectively, and production of gamma interferon (IFN gamma). We compared the antigen-specific response with the response induced by phytohaemagglutinin (PHA) as a positive control. There was no difference between acute patients and the healthy controls in the percentages of CD3+, CD4+ or CD8+ lymphocytes. However, we found that chronic patients had a significant (P < 0.05) increase in the CD8+ T cells, in line with previous studies. Antigen-specific responses to RCM-BM showed a significant (P < 0.05) upregulation of CD69 in both CD4+ and CD8+ T lymphocytes in acute brucellosis patients and in CD8+ T lymphocytes in chronic patients, indicating that both populations became activated by this antigen preparation. Moreover, lymphocyte proliferation from both acute and chronic patients in response to RCM-BM was highly significant (P < 0.001) when compared with healthy controls. However, there were no apparent differences between acute and chronic patients. Although the incorporation of BrdU showed similar results it provided additional information, since we demonstrated that both CD4+ and CD8+ T lymphocytes from acute and chronic patients proliferated equally well in response to RCM-BM. Similar results were observed with intracellular IFN gamma determination. As a whole, our data suggest an important role for both CD4+ and CD8+ T lymphocytes in Brucella infection in humans. As has been reported in mice, it is feasible that activated CD8+ T cells participate in protection against Brucella in humans through cytotoxicity or/and by the production of factors such as interferon and granulysin. The role of these cells should be carefully analysed to understand better their participation in human infection by Brucella.     

Immunologic and virologic evaluation of HIV-1-infected children after rabies vaccination

BACKGROUND: One-third of Thai children experience a dog bite by the time they are 15 years old, and HIV-1 infection in children is also not uncommon. Previous study has shown that rabies vaccination of HIV-1-infected children may not result in a satisfactory antibody response when CD4+ T cells are less than 15%. The objective of this prospective clinical study is to evaluate the immunologic response and effect on viral load after rabies vaccination in HIV-infected children. METHODS: Thirteen HIV-1-infected children were vaccinated with the intramuscular rabies pre-exposure regimen using human diploid cell rabies vaccine (HDCV) on days 0, 7 and 28. CD4+ and CD8+ lymphocyte counts were performed on days 0, 7 and 28. Plasma viral loads were determined on days 0, 7, 14, 60, 90, 180 and 360. RESULTS: There were no significant change in serial measurements of CD4+/CD8+ lymphocytes during a period of 1 month and in plasma viral load during 1 year. There was no associated clinical deterioration or any adverse reactions attributable to vaccine. CONCLUSIONS: Rabies vaccination in HIV-1-infected children appears to be safe but did not significantly change the levels of plasma HIV RNA, CD4+ and CD8+ cell counts.     

Flow cytometric assessment of chicken T cell-mediated immune responses after Newcastle disease virus vaccination and challenge

The objective of this study was to use flow cytometry to assess chicken T cell-mediated immune responses. In this study two inbred genetic chicken lines (L130 and L133) were subjected to two times vaccination against Newcastle disease (ND) and a subsequent challenge by ND virus (NDV) infection. Despite a delayed NDV-specific antibody response to vaccination, L133 appeared to be better protected than L130 in the subsequent infection challenge as determined by the presence of viral genomes. Peripheral blood was analyzed by flow cytometry and responses in vaccinated/challenged birds were studied by 5-color immunophenotyping as well as by measuring the proliferative capacity of NDV-specific T cells after recall stimulation. Immunophenotyping identified L133 as having a significantly lower CD4/CD8 ratio and a lower frequency of γδ T cells than L130 in the peripheral T cell compartment. Furthermore, peripheral lymphocytes from L133 exhibited a significantly higher expression of CD44 and CD45 throughout the experiment. Interestingly, also vaccine-induced differences were observed in L133 as immune chickens had a significantly higher CD45 expression on their lymphocytes than the naïve controls. Immune chickens from both lines had a significantly higher frequency of circulating γδ T cells than the naïve controls both after vaccination and challenge. Finally, the proliferative capacity of peripheral CD4+ and CD8+ cells specific for NDV was addressed 3 weeks after vaccination and 1 week after infection and found to be significantly higher in L133 than in L130 at both sampling times. In conclusion, we found the applied flow cytometric methods very useful for the study of chicken T cell biology.     

Nasal immunization of mice with AFCo1 or AFPL1 plus capsular polysaccharide Vi from Salmonella typhi induces cellular response and memory B and T cell responses

The response to infection against Salmonella involves both B and T cell mediated immunity. An effective immunization can activate an adequate immune response capable to control the primary infection and protect against a secondary infection. Mucosal vaccination, by inducing local pathogen-specific immune responses, has the potential to counter mucosally transmitted pathogens at the portal of entry, thereby increasing the efficacy of vaccines. The aim of this work was to explore the efficacy of AFCo1 or AFPL1, as mucosal adjuvants to stimulate cell immunity and memory responses against Vi polysaccharide antigen of Salmonella typhi (PsVi). Mice immunized with 3 intranasal doses exhibited high levels of PsVi-specific IgG (p < 0.05), IgG2a and IgG2c subclasses. Also, an amplified recall response after a booster immunization with a plain polysaccharide vaccine was induced. Avidities index were higher in mice immunized with adjuvanted formulations at different chaotropic concentrations. Furthermore, IL-12 and IFN-γ levels in nasally vaccinated mice with both adjuvants were induced. Moreover, priming with 3 doses followed by booster immunization with VaxTyVi^® resulted in high levels of anti-Vi specific IgG, IgG subclasses and antibody avidity. Long lived plasma cells in bone marrow, memory B cells and long-term memory T cells after booster dose were induced. The combined formulation of Vi polysaccharide with mucosal adjuvants provides an improved immunogenicity, in particular with regard to cellular responses and long lasting cells responses.     

Assessment of the antibody response in 110 healthy individuals who have been subject to Vi capsular polysaccharide vaccine

Typhoid fever is a disease predominant in underdeveloped and developing countries. Typhoid fever is more prevalent, in fact endemic, in countries where fecal contamination of water and food sources are very common. The majority of the reported cases are in the adult age group. There are three different vaccines which can be used to prevent typhoid fever. In this study, we have used the parenteral Vi vaccine which was developed using the polysaccharide Vi antigen that covers the bacterial surface, thus, concealing the O antigen protecting the bacteria against Anti-O antibodies and regarded as virulence factor. A total of 110 individuals whose sera were negative for seroconversion prior to vaccination were included in this study in which we have assessed Anti-Vi antibodies by tube agglutination. Serum and stool samples of 110 individuals were assessed 1 month after the vaccination. A total of 105 (95.5%) of the vaccinated people were considered to have positive (1/40 and higher) response and this result was regarded as prophylactic seroconversion. None of the people in the study group had Salmonella typhi, S. paratyphi A,B,C isolated from their stool cultures.     

Inhalative vaccination with pneumococcal polysaccharide in patients with chronic obstructive pulmonary disease

In order to determine the feasibility of inhalative vaccination with polysaccharide antigen in patients with chronic obstructive pulmonary disease (COPD), we used controlled inhalation of a defined dose of Pneumovax in a randomized 3-arm study. The vaccine was either deposited in the alveoli (alveolar vaccination) or in the large airways (bronchial vaccination) and these were compared to standard intramuscular vaccination. Adverse effects were minor and never exceeded WHO grade 2. There was frequent cough, headache and shivering in the bronchial vaccination group, frequent fatigue only in the alveolar vaccination group and no frequent adverse effects in the intramuscular vaccination group. Specific serum IgG antibody was measured before and at 4 and 12 weeks after vaccination. At 12 weeks there was a greater than twofold rise in 7 out of 10 individuals in every vaccination group. Mean antibody levels of responders at 12 weeks were 278 mg/l for alveolar vaccination, 238 mg/l for bronchial vaccination and 737 mg/l for standard intramuscular vaccination. The data show that polysaccharide vaccine can be safely administered by controlled inhalation in COPD patients and that it can induce a rapid serum antibody response.     

内蒙古新发现HIV感染者首次CD4~+T淋巴细胞检测分析

目的:通过对内蒙古地区新发现的HIV感染者首次CD4+T淋巴细胞进行检测分析,了解其免疫状况及疾病进展情况。方法:采用流式细胞术对采集的全血样本进行CD4+T淋巴细胞绝对值检测,统计分析其测定值。结果:能随访到的182例HIV感染者CD4+T淋巴细胞绝对值的均值为(459.85±240.21)个/μl。不同年龄组HIV感染者间CD4+T淋巴细胞绝对值差异具有统计学意义(F=9.509,P=0.0001**<0.05),且随年龄增长CD4+T淋巴细胞绝对值具有下降趋势。结论:内蒙古新发现HIV感染者中1/3已进入艾滋病期,需要监测疾病进程并及时对其进行抗病毒治疗。加强宣传,早发现、早干预、早管理,以提高HIV感染者的生存质量。     

Serological response to pneumococcal vaccination in HAART-treated HIV-infected patients: one year follow-up study

The aim of this study was to evaluate specific IgG responses against pneumococcal serotypes 1, 6B, 14, 19F, 23F at baseline, 1 and 12 months after vaccination with the 23-valent polysaccharide pneumococcal vaccine in 89 HAART-treated HIV-infected patients, 24 antiretroviral "na?ve" HIV-infected and 30 non-HIV-infected healthy subjects. Levels of specific antipneumococcal IgG and the mean fold increase in IgG levels at 1 month as well as the kinetics of antibodies along the 12 months in all groups of HIV-infected patients and healthy subjects were similar. Neither CD4 cell count at baseline nor "nadir" CD4 cells correlated with the response to the vaccine. In conclusion, the immunogenicity conferred by the polysaccharide vaccine in HIV-infected patients under HAART is at least as good as that observed in healthy subjects.