T Cell Immunogenicity, Gene Expression Profile, and Safety of Four Heterologous Prime-Boost Combinations of HIV Vaccine Candidates in Healthy Volunteers: Results of the Randomized Multi-Arm Phase I/II ANRS VRI01 Trial

Heterologous prime-boost strategies are of interest for HIV vaccine development. The order of prime-boost components could be important for the induction of T cell responses. In this phase I/II multi-arm trial, three vaccine candidates were used as prime or boost: modified vaccinia Ankara (MVA) HIV-B (coding for Gag, Pol, Nef); HIV LIPO-5 (five lipopeptides from Gag, Pol, Nef); DNA GTU-MultiHIV B (coding for Rev, Nef, Tat, Gag, Env gp160 clade B). Healthy human volunteers (n = 92) were randomized to four groups: 1) MVA at weeks 0/8 + LIPO-5 at weeks 20/28 (M/L); 2) LIPO-5 at weeks 0/8 + MVA at weeks 20/28 (L/M); 3) DNA at weeks 0/4/12 + LIPO-5 at weeks 20/28 (G/L); 4) DNA at weeks 0/4/12 + MVA at weeks 20/28 (G/M). The frequency of IFN-γ-ELISPOT responders at week 30 was 33, 43, 0, and 74%, respectively. Only MVA-receiving groups were further analyzed (n = 62). Frequency of HIV-specific cytokine-positive (IFN-γ, IL-2, or TNF-α) CD4⁺ T cells increased significantly from week 0 to week 30 (median change of 0.06, 0.11, and 0.10% for M/L, L/M, and G/M, respectively), mainly after MVA vaccinations, and was sustained until week 52. HIV-specific CD8⁺ T cell responses increased significantly at week 30 in M/L and G/M (median change of 0.02 and 0.05%). Significant whole-blood gene expression changes were observed 2 wk after the first MVA injection, regardless of its use as prime or boost. An MVA gene signature was identified, including 86 genes mainly related to cell cycle pathways. Three prime-boost strategies led to CD4⁺ and CD8⁺ T cell responses and to a whole-blood gene expression signature primarily due to their MVA HIV-B component.

Optimal priming of poxvirus vector (NYVAC)-based HIV vaccine regimens for T cell responses requires three DNA injections. Results of the randomized multicentre EV03/ANRS VAC20 Phase I/II Trial

DNA vectors have been widely used as a priming of poxvirus vaccine in prime/boost regimens. Whether the number of DNA impacts qualitatively or quantitatively the immune response is not fully explored. With the aim to reinforce T-cell responses by optimizing the prime-boost regimen, the multicentric EV03/ANRS VAC20 phase I/II trial, randomized 147 HIV-negative volunteers to either 3xDNA plus 1xNYVAC (weeks 0, 4, 8 plus 24; n = 74) or to 2xDNA plus 2xNYVAC (weeks 0, 4 plus 20, 24; n = 73) groups. T-cell responses (IFN-γ ELISPOT) to at least one peptide pool were higher in the 3xDNA than the 2xDNA groups (91% and 80% of vaccinees) (P = 0.049). In the 3xDNA arm, 26 (37%) recipients developed a broader T-cell response (Env plus at least to one of the Gag, Pol, Nef pools) than in the 2xDNA (15; 22%) arms (primary endpoint; P = 0.047) with a higher magnitude against Env (at week 26) (P<0.001). In both groups, vaccine regimens induced HIV-specific polyfunctional CD4 and CD8 T cells and the production of Th1, Th2 and Th17/IL-21 cytokines. Antibody responses were also elicited in up to 81% of vaccines. A higher percentage of IgG responders was noted in the 2xDNA arm compared to the 3xDNA arm, while the 3xDNA group tended to elicit a higher magnitude of IgG3 response against specific Env antigens. We show here that the modulation of the prime strategy, without modifying the route or the dose of administration, or the combination of vectors, may influence the quality of the responses.

Development of a safe and effective HIV-1 vaccine would undoubtedly be the best solution for the ultimate control of the worldwide AIDS pandemic. To date, only one large phase III trial (RV144 Thai study) showed a partial and modest protection against HIV infection. This result raised hope in the field and encouraged the development of vaccines or strategies in order to improve vaccine efficacy. Several vaccine strategies designed to elicit broad HIV-specific T cells and/or neutralizing antibodies to prevent HIV-1 transmission are under evaluation. Among diverse candidate vaccines, the safety and immunogenicity of multi-gene DNA-based and Pox-virus derived vaccines have been evaluated in several clinical studies. The present study was designed to optimize the combination of these two vaccines with the aim of determining the optimal number of DNA primes for a poxvirus-based HIV vaccine regimen. We show here that the prime boost combination is highly immunogenic and that the number of DNA primes induces differentially T cell and antibody responses. A better priming of poxvirus-based vaccine regimens for T cells is obtained with 3 DNA injections. Our results contribute and extend data of several preclinical studies pointing out the potential interest of DNA as a prime capable not only of improving immune responses but also of imprinting the long-term responses to boost vaccines.

The human immunodeficiency virus preventive vaccine research at the French National Agency for acquired immunodeficiency syndrome research

The human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) epidemic is of unprecedented gravity and is spreading rapidly, notably in the most disadvantaged regions of the world. The search for a preventive vaccine is thus an absolute priority. For over 10 years the French National Agency for AIDS research (ANRS) has been committed to an original program combining basic science and clinical research. The HIV preventive vaccine research program run by the ANRS covers upstream research for the definition of immunogens, animal models, and clinical research to evaluate candidate vaccines. Most researchers in 2004 believe that it should be possible to obtain partial vaccine protection through the induction of a strong and multiepitopic cellular response. Since 1992, the ANRS has set up 15 phases I and II clinical trials in order to evaluate the safety and the capacity of the candidate vaccines for inducing cellular immune responses. The tested candidate vaccines were increasingly complex recombinant canarypox viruses (Alvac) containing sequences coding for certain viral proteins, utilized alone or combined with other immunogens (whole or truncated envelope proteins). ANRS has also been developing an original strategy based on the utilization of lipopeptides. These comprise synthetic fragments of viral proteins associated with lipids that facilitate the induction of a cellular immune response. These approaches promptly allowed the assessment of a prime-boost strategy combining a viral vector and lipopeptides.

Activities of garenoxacin against quinolone-resistant Streptococcus pneumoniae strains in vitro and in a mouse pneumonia model

Garenoxacin is a novel des-F(6) quinolone with enhanced in vitro activities against both gram-positive and gram-negative bacteria. We compared the activity of garenoxacin with that of trovafloxacin (TVA) against Streptococcus pneumoniae, together with their efficacies and their capacities to select for resistant mutants, in a mouse model of acute pneumonia. In vitro, garenoxacin was more potent than TVA against wild-type S. pneumoniae and against a mutant with a single mutation (parC), a mutant with double mutations (gyrA and parC), and a mutant with triple mutations (gyrA, parC, and parE). Swiss mice were infected with 10(5) CFU of virulent, encapsulated S. pneumoniae strain P-4241 or its derived isogenic parC, gyrA, gyrA parC, and efflux mutants and 10(7) CFU of poorly virulent clinical strains carrying a parE mutation or gyrA, parC, and parE mutations. The drugs were administered six times, every 12 h, beginning at either 3 or 18 h postinfection. The pulmonary pharmacokinetic parameters in mice infected with strain P-4241 and treated with garenoxacin or TVA (25 mg/kg of body weight) were as follows: maximum concentration of drug in serum (C(max); 17.3 and 21.2 micro g/ml, respectively), C(max)/MIC ratio (288 and 170, respectively), area under the concentration-time curve (AUC; 48.5 and 250 microg. h/ml, respectively), and AUC/MIC ratio (808 and 2000, respectively). Garenoxacin at 25 and 50 mg/kg was highly effective (survival rates, 85 to 100%) against the wild-type strain and mutants harboring a single mutation. TVA was as effective as garenoxacin against these strains. TVA at 200 mg/kg and garenoxacin at 50 mg/kg were ineffective against the mutant with the parC and gyrA double mutations and the mutant with the gyrA, parC, and parE triple mutations. The efficacy of garenoxacin was reduced only when strains bore several mutations for quinolone resistance.

Streptococcus pneumoniae strain-dependent lung inflammatory responses in a murine model of pneumococcal pneumonia

OBJECTIVE

The inherent properties of an invading bacterium may influence the cytokine profile that is ultimately produced. We determined the alterations in proinflammatory (TNF-alpha, IL-1, and IL-6) and anti-inflammatory cytokine (IL-10) expressions in lung tissues within the first 48 h after infection in mice with pneumonia induced by direct intratracheal inoculation of five different pneumococcal strains.

DESIGN

Experimental murine model of Streptococcus pneumoniae pneumonia.

SUBJECTS

Female BALB/cby mice aged 8-10 weeks.

INTERVENTIONS

Five S. pneumoniae clinical isolates were used in this study. The strains included two serotype 3 strains (P4241 and P30606), two serotype 6 strains (P26772 and P23477), and one serotype 19 strain (P15986). The trachea of anesthetized animals was cannulated via the mouth with a blunt needle, and 50 micro l bacterial suspension of two different inocula (their respective 100% lethal inoculum and the same 10(5) CFU/mouse inoculum of S. pneumoniae strains) were instillated. At predetermined times after pneumococcal infection, i.e., time 0 (preinfection) and 2, 4, 6, 12, 24, and 48 h postinfection in experimental groups, lung tissues were sampled from groups of three mice to quantify lung pro- and anti-inflammatory mediators. The experiments were repeated at least three times.

RESULTS

Pneumonia induced by five different pneumococcal isolates resulted in pronounced differences in the local pro- and anti-inflammatory profiles. For example, with a 100% lethal inoculum of S. pneumoniae, the extent and timing of TNF-alpha expression varied greatly among strains, ranging from 2,643 to 10,022 pg/g and from 4 to 48 h, respectively. Moreover, TNF-alpha productions within 48 h postinfection measured by the 48 h area under the curve were differed significantly, ranging from 59,700 to 275,825. These different profiles were not serotype dependent. Comparable results were obtained when IL-1, IL-6, and IL-10 expressions in lung tissues were studied.

CONCLUSIONS

These findings confirm that the production of the pro- and anti-inflammatory mediators are critically dependent not only upon the different species of bacteria used to establish the experimental infection but also upon the different strains of a specific bacterial species used, i.e., S. pneumoniae in this study. These substantially different host responses were not serotype dependent. Moreover, the profile of lung pro-and anti-inflammatory cytokines within 48 h postinfection, at least in this pneumonia model, was not related to outcome of animals.

Complex relationship between acquisition of beta-lactam resistance and loss of virulence in Streptococcus pneumoniae

In a previous study of a murine peritonitis model, no Streptococcus pneumoniae strains were found that were both clinically penicillin resistant and virulent. This study assessed the relationship between acquired resistance and virulence in single- and double-isogenic penicillin-resistant (Peni-R) mutants obtained by transformation of a virulent penicillin-susceptible recipient strain with pbp2b and pbpX polymerase chain reaction fragments from a Peni-R donor strain. Sequence analysis results of the pbp2b and pbpX alleles from these strains were in keeping with acquired penicillin resistance. The virulence of these strains was significantly reduced, which shows a relationship between beta-lactam resistance and loss of virulence. The phenotype of the 23.2x mutant remained stable after in vivo passage, which suggests that the pbpX gene is involved in growth, whereas virulent revertants of the 23.2b and 23.2b.2x mutants had no change in MIC. Compensatory mutations are implicated in the revival of virulence.

Relationship between capsular type, penicillin susceptibility, and virulence of human Streptococcus pneumoniae isolates in mice

We examined the relationship between penicillin susceptibility, peritoneal virulence in Swiss mice, and capsular type in a selection of 122 clinical Streptococcus pneumoniae isolates belonging to 24 serotypes. Regardless of the serotype, all 32 virulent strains were susceptible to penicillin, and all 41 strains with diminished susceptibility or resistance to penicillin were avirulent. The remaining 49 strains were both susceptible to penicillin and avirulent, irrespective of the serotype. On the basis of their capsular type and pathogenic behavior, strains fell into one of four groups. In the group consisting of serotypes 1, 3, and 4 (n = 16), strains were predominantly virulent (81.3%), and all were penicillin susceptible. In the serotype 6 group (n = 32), the frequency of virulence was significantly lower (34.4 versus 81.3%, P = 0.002), and strains were predominantly penicillin susceptible (71.9%). In the group composed of serotypes 9, 14, 19, and 23 (n = 50), all strains were avirulent, and 56% had decreased susceptibility (n = 12) or resistance to (n = 16) penicillin. The fourth group was heterogenous, as it pooled 24 strains of 15 different serotypes; in this group the frequency of virulence was 33.3%, and strains were predominantly penicillin susceptible (83.3%). These data point to a complex relationship between penicillin susceptibility and virulence in mice but do not entirely separate these characteristics from the role of the capsular type. The possibility that the mechanisms conferring penicillin resistance are related to those leading to a loss of virulence is supported by these findings.

[Selection of virulent mutants of Streptococcus pneumoniae. Utilization of a murine model of septicemia]

Genetic construction of virulence deficient mutant is a strategy to analyse virulence genes of Streptococcus pneumoniae and was used to virulence factors as capsule, pneumolysin, autolysin and PspA. We perform a model allowing the in vivo positive selection of virulent S. pneumoniae mutants. Mice which are the most susceptible animals to pneumococcal infection, offer the best model for screening virulent S. pneumoniae. Indeed, after intraperitoneal injection of bacterial mix which was composed to a lot of avirulent bacteria (6 log10 CFU per mouse) (V1015 strain, DL50 = 7.05) and few virulent pneumococci (1 to 2 log10 CFU per mouse) (P4241 strain, DL50 < 1), mice cleared all avirulent bacteria but not virulent pneumococci. Thus, mice dead in 3 to 4 days with septicaemia and positive hemoculture contained only virulent strain. This model was validated by in vivo selection of a virulent mutant (V1042, DL50 = 4.1) which was obtained after transformation of avirulent strain V1015 with the genomic fragment of virulent strain P4241. Our model of screening was the only one allowing detection of virulent S. pneumoniae mutants. This new genetic strategy which consisted in gene addition and used mouse as selection agent, could be used to discover new virulence genes required to in vivo bacterial development.

Efficacy of trovafloxacin against penicillin-susceptible and multiresistant strains of Streptococcus pneumoniae in a mouse pneumonia model

The increasing emergence of penicillin-resistant and multidrug-resistant strains of Streptococcus pneumoniae will create a serious therapeutic problem in coming years. Trovafloxacin is a novel naphthyridone quinolone with promising activity against S. pneumoniae, including penicillin-resistant strains (MIC for 90% of the isolates tested, 0.25 microg/ml). We compared its in vivo efficacy with that of other fluoroquinolones (ciprofloxacin, temafloxacin, and sparfloxacin) and a reference beta-lactam (amoxicillin) in a model of acute experimental pneumonia. Immunocompetent Swiss mice were infected by peroral tracheal delivery of a virulent, penicillin-susceptible strain (MIC, 0.03 microg/ml); leukopenic Swiss mice were infected with three poorly virulent, penicillin-resistant strains (MICs, 4 to 8 microg/ml) and a ciprofloxacin-resistant strain (MIC, 32 microg/ml). Treatments were started 6 h (immunocompetent mice) or 3 h (leukopenic mice) after infection. Doses ranging from 12.5 to 300 mg/kg were given at 12- or 8-h intervals for 3 days. Trovafloxacin (25 mg/kg) was the most effective agent in vivo against penicillin-susceptible and -resistant strains. Corresponding survival rates were 2- to 4-fold higher than with 50-mg/kg sparfloxacin or temafloxacin and 8- to 16-fold higher than with 100-mg/kg ciprofloxacin. The ratios of the area under the concentration-time curve to the MIC in serum and lung tissue were more favorable with trovafloxacin than with the other quinolones. Efficacy in vivo correlated with pharmacokinetic parameters. Trovafloxacin shows potential for the treatment of infections due to penicillin-susceptible and -resistant S. pneumoniae but appears to be ineffective against a ciprofloxacin-resistant strain.

Pleiotropic mutations alter the kinetics of calcium transport, competence regulation, autolysis and experimental virulence in Streptococcus pneumoniae

Streptococcus pneumoniae is a pathogen in which the extracellular calcium concentration plays a major physiological role, in growth as well as in the induction of competence for genetic transformation and activation of autolysis. Both responses are under the control of a protein activator exported in the medium. We have checked the impact of mutations which alter the regulation of competence and autolysis on experimental virulence. Isogenic encapsulated derivatives carrying the relevant mutations were serotype 3 smooth clones, obtained by transformation of the relevant rough strains with DNA from a serotype 3 smooth isolate. Survival kinetics and bacterial clearance from the blood were followed after intraperitoneal infection of Swiss mice with the different bacterial cultures. In this model, mutants showing an attenuation of virulence relative to the wild type fell into two classes. In the first, represented by the lytA::ery mutant V1095 defective for calcium-induced autolysis, attenuated virulence could be correlated with rapid bacterial clearance from the blood. In the second, represented by the dmb mutants V2200 and V3300, attenuation was associated with delayed bacterial clearance from the blood, and correlated with altered kinetics of calcium transport and of regulation of competence and autolysis. It appeared unlikely that attenuation of virulence for strains V2200 and V3300 was a direct consequence of their competence phenotype, since the com::ery mutants V1008 and V1019, defective for the production of the competence activator, were as virulent as the wild-type strain. Autolysis involving an N-acetyl-muramyl-alanine amidase encoded by lytA was also regulated by calcium. The inserted allele lytA0::ery further reduced virulence in the dmb1 background (V2200). This additive effect of lytA- to dmb1 points to different routes of virulence regulation by LYT and DMB1 and suggests that the kinetics of calcium traffic controls several pathways involved in the virulence of pneumococcus.

Efficacies of cefotaxime and ceftriaxone in a mouse model of pneumonia induced by two penicillin- and cephalosporin-resistant strains of Streptococcus pneumoniae

We previously demonstrated the efficacy of ceftriaxone (CRO), at 50 mg/kg of body weight every 12 h, against a highly penicillin-resistant (MIC, 4 micrograms/ml) Streptococcus pneumoniae strain with low-level resistance to CRO (MIC, 0.5 microgram/ml) in a leukopenic-mouse pneumonia model (P. Moine, E. Vallée, E. Azoulay-Dupuis, P. Bourget, J.-P. Bédos, J. Bauchet, and J.-J. Pocidalo, Antimicrob. Agents Chemother. 38:1953-1958, 1994). In the present study, we assessed the activity of CRO versus those of cefotaxime (CTX) and amoxicillin (AMO) against two highly penicillin- and cephalosporin-resistant S. pneumoniae strains (P40422 and P40984) (MICs of 2 and 8 for penicillin, 2 and 4 for AMO, and 4 and 8 for CRO or CTX, respectively). Against both strains, a greater than an 80% cumulative survival rate was observed with CRO at a dose of 100 or 200 mg/kg every 12 h (dose/MIC ratio, 25). With CTX, a high dosage of 400 mg/kg (dose/MIC ratio, 100 or 50) administered every 8 h (TID) was needed to protect 66 and 75% of the animals, respectively, with no statistically significant differences versus CRO. Against the P40422 strain, CRO (100 mg/kg) produced the greatest bactericidal effect, from the 8th to the 24th hour after a single injection (1.8-log-unit reduction over 24 h), and the fastest bacterial pulmonary clearance during treatment; with CTX, only multiple injections at a high dosage, i.e., 400 mg/kg TID, demonstrated a significant bactericidal effect. AMO in a high dosage, 400 mg/kg (dose/MIC ratio, 200) TID, showed good activity only against the P40422 strain. Despite the identical MICs of CTX and CRO, the longer time (3.6 to 4.6 h) that serum CRO concentrations remained above the MICs for the pathogens at a dose of 100 mg/kg resulted in greater efficacy versus CTX against highly penicillin- and cephalosporin-resistant S. pneumoniae strains.

Amoxicillin dose-effect relationship with Streptococcus pneumoniae in a mouse pneumonia model and roles of in vitro penicillin susceptibilities, autolysis, and tolerance properties of the strains

We used a mouse model of pneumococcal pneumonia to assess the bactericidal effect of increasing doses of amoxicillin (AMX) against clinical strains with various susceptibilities to penicillin. Twelve strains that exhibited similar virulence in mice were selected. Three were penicillin susceptible (PS) (penicillin and AMX MICs = 0.01 to 0.03 microgram/ml), three were intermediately resistant (PIR) (penicillin and AMX MICs = 0.5 to 1 microgram/ml), and six were penicillin resistant (PR) (penicillin and AMX MICs = 1 to 8 micrograms/ml). Leukopenic Swiss mice were infected intratracheally with 10(7) CFU of each strain. Treatment was initiated 3 h after infection and consisted of a single subcutaneous injection of AMX at doses ranging from 2.5 to 10 mg/kg (PS strains), 5 to 100 (PIR strains), and 25 to 3,000 (PR strains). Bacterial killing kinetics were recorded in the lungs over 9 h. The maximal log CFU reduction (Emax) was observed 3 h postinjection. The relation between Emax and log10(dose/MIC) showed two populations. With seven strains (the three PS, the three PIR, and one of the six PR [MICs, penicillin/AMX = 4/1]) a good correlation was observed between Emax and log10(dose/MIC) (r = 0.772; P < 0.02). A bactericidal effect equal to 3.5 log10 CFU was observed at a log10(dose/MIC) = 2. At this ratio, with the five other PR strains, Emax varied from 0.4 to 1.6 log10 CFU. In brain heart infusion medium containing AMX at 50 times the relevant MIC, these five PR strains were tolerant in vitro. Treatment failure with AMX was found in vivo, with tolerant, highly resistant strains.

Mutations which alter the kinetics of calcium transport alter the regulation of competence in Streptococcus pneumoniae

In Streptococcus pneumoniae, Ca2+ induces a stress response which is regulated by a proteic activator known as competence factor (CF). This stress response is expressed as the induction of competence for DNA uptake and genetic transformation in exponentially growing cultures and by autolysis in late exponential phase. DNA transport during competence can be described as a homeostatic response that prevents autolysis of the cultures. Electrogenic and cooperative calcium transport with a Hill number (nH) of 2 appears to mediate this Ca2+ response. Mutant strains altered in their kinetics for Ca2+ transport, with nHs of 1 and 4, were isolated and characterized in order to address the role of the kinetics of Ca2+ transport in the Ca2+ response. The reduced cooperativity of Ca2+ uptake in mutant strain Cp2200 was associated with an absolute requirement for added CF to develop competence and with resistance to autolysis. The enhanced cooperativity of Ca2+ uptake in mutant strain Cp3300 was associated with facilitated competence and hypersensitivity to autolysis. Moreover, the mutation carried by strain Cp3300 increases the CF response of previously described competence-defective mutants. The pleiotropic mutants Cp2200 and Cp3300 allowed us to demonstrate that cooperativity of transport determines the Ca2+ response in S. pneumoniae.