The outer surface protein A (OspA) vaccine against Lyme disease: efficacy in the rhesus monkey.

The efficacy of an outer surface protein A (OspA) vaccine in three different formulations was investigated in the rhesus monkey. The challenge infection was administered using Ixodes scapularis ticks that were infected with the B31 strain of Borrelia burgdorferi. Protection was assessed against both infection and disease, by a variety of procedures. Some of the animals were radically immune suppressed, as an attempt to reveal any putative low level infection in the vaccinated animals. The significant difference found between the spirochaetal infection rates of ticks that had fed on vaccinated vs. control monkeys, lack of seroconversion in the vaccinated animals, and the absence of spirochaetal DNA in the skin of vaccinated animals in the weeks following the challenge, indicate that vaccinated monkeys were protected against tick challenge. The post-mortem immunohistochemical and polymerase chain reaction analyses, however, suggest that these monkeys may have undergone a low-level infection that was transient.

Hepatitis B vaccine containing surface antigen and selected preS1 and preS2 sequences. 1. Safety and immunogenicity in young, healthy adults.

The safety and immunogenicity of a yeast-derived recombinant hepatitis B virus (HBV) vaccine containing surface antigen (S) and selected preS1 and preS2 sequences (S-L*) were compared with those of a vaccine prepared with S alone (Engerix-B). S-L* consisted of composite particles containing S and L* at a ratio of 70/30. L* encompassed amino acid residues 12-52 of preS1 residues 133-145 of preS2, and the entire S domain. A total of 100 healthy, HBV-seronegative, young adults were randomized to receive 20 micrograms/dose of either S-L* or Engerix-B under double-blind conditions according to a 0-, 1-, 2-, 12-month schedule. In vivo humoral and in vitro lymphoproliferative responses to S and preS regions were monitored. Addition of the selected preS sequences to S did not enhance the in vivo humoral anti-HBs response but improved the in vitro stimulating capacity of the antigen (L*) in S-L* primed subjects.

Hepatitis B vaccine containing surface antigen and selected preS1 and preS2 sequences. 2. Immunogenicity in poor responders to hepatitis B vaccines.

The immunogenicity of a yeast-derived recombinant hepatitis B virus (HBV) vaccine containing surface antigen (S) and selected preS1 and preS2 sequences (S-L*) was compared with that of a vaccine containing S alone (Engerix-B) in 32 healthy adults with a previous history of poor response (anti-HBs < 10 mIU ml-1) after at least three consecutive monthly doses of hepatitis B vaccines. The poor responders were randomized to receive three additional 20-microgram doses of either S-L* or Engerix-B in a double-blind fashion according to a 0-, 1-, 2-month schedule. In vivo humoral and in vitro lymphoproliferative responses to the S and preS regions were monitored. Although the addition of the selected preS sequences to S did not enhance the in vivo humoral anti-HBs response, the administration of the three additional vaccine doses, irrespective of their preS content, induced seroprotective anti-HBs levels in most vaccinees (29/32, 91%). In vitro proliferative responses to HBV surface antigens were only observed in subjects displaying anti-HBs titers > 1000 mIU ml-1 after the third additional vaccine dose.

Activation of monocytes by three OspA vaccine candidates: lipoprotein OspA is a potent stimulator of monokines.

The outer surface protein (Osp) A of Borrelia burgdorferi is the first Lyme antigen to be tested in a vaccine for humans. Three forms of OspA vaccine candidates were investigated by the induction of the cytokines interleukin (IL)-1 beta, IL-6, tumor necrosis factor (TNF)-alpha, IL-10 and interferon (IFN)-gamma as markers of monocyte activation and immune stimulation: lipidated OspA (L-OspA), non-lipidated OspA (NL-OspA), and a fusion protein of 81 amino acids of the nonstructural protein 1 of influenza virus with OspA (NS1-OspA). All OspA preparations induced IL-1 beta, IL-6 and TNF-alpha in a concentration-dependent manner with peak levels at 12-24 h. These cytokines were entirely derived from the monocyte fraction. In peripheral blood mononuclear cells from 10 healthy donors, L-OspA at 10 micrograms ml-1 induced up to 4-fold more IL-1 beta, IL-6, and TNF-alpha than the other OspA preparations (P < or = 0.0068), followed by NS1-OspA, which was still superior to NL-OspA. L-OspA. L-OspA also induced high levels of IL-10 within 24 h but no significant amounts of IFN-gamma. This superior stimulating activity of L-OspA on unstimulated monocytes predominantly depended on N-terminal lipidation of OspA. Similarities to other lipoproteins and synthetic lipopeptides suggest that lipidation confers adjuvant properties on OspA. High induction of IL-10 by L-OspA further suggested a negative feedback on monocyte activation by the lipidated form. The in vitro results are in line with in vivo results in mice, monkeys and humans and indicates that lipoprotein OspA has the best potential for induction of a protective effect in humans, compared to non-lipidated antigens.

Reactivity with a specific epitope of outer surface protein A predicts protection from infection with the Lyme disease spirochete, Borrelia burgdorferi.

The response to recombinant vaccines for Lyme disease was studied to determine serum antibody levels effective in protecting against tick-transmitted infection. Data presented here demonstrate a significant correlation between antibody to an epitope on outer surface protein A (OspA) and protection against infection with Borrelia burgdorferi in canines and mice. A competitive enzyme-linked immunosorbent assay was developed to measure antibody to a site on OspA, defined by monoclonal antibody LA-2. Comparison of LA-2 titers against infection of canines and mice following vaccination and challenge established a predicted value for LA-2 titers. The statistical relationship between serum antibody levels and protection was calculated by logistic regression analysis. The statistical model predicted that an LA-2 titer of 0.32 microg equivalents (eq) per ml correlated to an 80% predicted probability of protection for both mice and dogs. This value was used to classify mice and dogs as to their protected status at the time of tick exposure. The LA-2 cutoff titer (0.32 microg eq/ml) correctly classified all dogs (n = 13) and mice (n = 44) that failed to become infected. By contrast, 20 of 22 dogs and 28 of 31 mice with titers of less than 0.32 microg eq/ml became infected. On the basis of these results, we conclude that an LA-2 titer is a reliable indicator of immune status for estimating immune protection following use of OspA-based vaccines for B. burgdorferi sensu stricto.

A preliminary evaluation of a recombinant circumsporozoite protein vaccine against Plasmodium falciparum malaria. RTS,S Malaria Vaccine Evaluation Group.

BACKGROUND: The candidate vaccines against malaria are poorly immunogenic and thus have been ineffective in preventing infection. We developed a vaccine based on the circumsporozoite protein of Plasmodium falciparum that incorporates adjuvants selected to enhance the immune response. METHODS: The antigen consists of a hybrid in which the circumsporozoite protein fused to hepatitis B surface antigen (HBsAg) is expressed together with unfused HBsAg. We evaluated three formulations of this antigen in an unblinded trial in 46 subjects who had never been exposed to malaria. RESULTS: Two of the vaccine formulations were highly immunogenic. Four subjects had adverse systemic reactions that may have resulted from the intensity of the immune response after the second dose, which led us to reduce the third dose. Twenty-two vaccinated subjects and six unimmunized controls underwent a challenge consisting of bites from mosquitoes infected with P. falciparum. Malaria developed in all six control subjects, seven of eight subjects who received vaccine 1, and five of seven subjects who received vaccine 2. In contrast, only one of seven subjects who received vaccine 3 became infected (relative risk of infection, 0.14; 95 percent confidence interval, 0.02 to 0.88; P<0.005). CONCLUSIONS: A recombinant vaccine based on fusion of the circumsporozoite protein and HBsAg plus a potent adjuvant can protect against experimental challenge with P. falciparum sporozoites. After additional studies of protective immunity and the vaccination schedule, field trials are indicated for this new vaccine against P. falciparum malaria.

Evaluation of the safety, reactogenicity and immunogenicity of three recombinant outer surface protein (OspA) lyme vaccines in healthy adults.

The safety, reactogenicity and immunogenicity of three candidate Lyme vaccines based on recombinant outer surface protein (OspA) presented in either lipidated or unlipidated forms, were assessed in 300 seronegative volunteers. Subjects received three doses of one of the three formulations at monthly intervals and were evaluated for antibody levels and the presence of symptoms after each dose. All formulations proved to be safe, the majority of local reactions being reported as mild, and all general symptoms were perceived to be either-mild or moderate in intensity. No subject refused a subsequent vaccine dose. All subjects were tested for both anti-OspA IgG and LA-2 equivalent antibodies up until day 84. All three vaccines induced an immune response but subjects who received lipoprotein OspA had the highest anti-OspA IgG and LA-2 equivalent GMTs after each dose and this was also true for the subset of subjects tested on day 180. The lipoprotein OspA group also had the largest number of subjects who remained seropositive for anti-OspA IgG antibodies. As the lipoprotein formulation produced the strongest immune response, with symptoms which were acceptable to all the vaccinees, we suggest further development of this vaccine.